China Building Energy Use and Carbon Emission Yearbook 2021: A Roadmap to Carbon Neutrality by 2060 9811675775, 9789811675775

Table of contents :
Preface
Acknowledgements (TBD)
Building Energy Research Center of Tsinghua University
Executive Summary
Achieving Carbon Target Will Lead to a Revolution of Building Sector
Reduce Direct Carbon Emission of Building Sector Needs Electrification
Reduce Indirect Carbon Emission from Electricity PEDF Buildings
Reduce Indirect Carbon Emission for Heating Require Zero-Carbon Heat Supply
Seize the Opportunities and Challenges
Contents
List of Figures
List of Tables
1 Introduction
2 Carbon Neutrality Pathways for China’s Building Sector
2.1 Director Carbon Emission
2.1.1 Cooking
2.1.2 Domestic Hot Water (DHW)
2.1.3 Heating
2.1.4 Gas Boilers and Others
2.2 Indirect Carbon Emission from Electricity and Heat
2.2.1 The Zero-Carbon Electricity Production Landscape and the Importance of Energy Conservation
2.2.2 The Building Sector Should Change from an Energy Consumer into an Active Contributor to Wind and Solar Power Development.
2.2.3 Methods to Achieve Zero-Carbon Heating
2.3 Carbon Emissions from the Construction of Buildings
2.4 Non-CO2 Greenhouse Gas Emissions
2.5 Eco-civilization Concept Should Be the Foundation
2.6 The Pathway to Zero-Carbon
3 China’s Building Energy Use and GHG Emissions
3.1 Basic Situation of China’s Building Sector
3.1.1 Urban and Rural Demographic
3.1.2 Building Stock
3.2 Global Energy Use and gGHG Emissions in the Building Sector
3.3 Energy Consumption of China’s Building Sector
3.3.1 Embodied Energy of Building Sector
3.3.2 Energy Use During Building Operation
3.4 GHG Emission of Building Sector
3.4.1 Embodied CO2 Emission of Building Sector
3.4.2 CO2 Emission During Building Operation
3.4.3 Other GHG Emission in Building Sector
4 Urban Residential Buildings Energy and Emissions
4.1 Urban Residential Buildings
4.2 Envelope Retrofitting of Northern Urban Residential Buildings
4.2.1 Distribution and current heating demand
4.2.2 Standards and Significance of Building Envelope Retrofit
4.2.3 Upgrading Techniques of Building Envelopes and Upgrading Results
4.2.4 Recommendations for the Future
4.3 Natural Gas Use in Urban Residential Buildings
4.3.1 Household Natural Gas Use and Distribution in Urban Residential Buildings
4.3.2 Electrification of Cooking
4.3.3 Electrification of DHW
4.4 Electricity Use in Urban Residential Buildings
4.4.1 The Total Electricity Consumed by Urban Households
4.4.2 Per Household Electricity Consumption
4.4.3 Difference in Lifestyle
4.4.4 The Future of Electricity Consumption in Urban Residential Housing
4.5 Multi-split Air Conditioning Systems in Urban Residential Areas
4.5.1 The Use of Multi-Split Air Conditioning Systems in Urban Residential Areas
4.5.2 Comparison of Multi-split and Split Air Conditioning in Urban Residential Buildings

Citation preview

Shan Hu Yi Jiang Da Yan

China Building Energy Use and Carbon Emission Yearbook 2021 A Roadmap to Carbon Neutrality by 2060

China Building Energy Use and Carbon Emission Yearbook 2021

Shan Hu · Yi Jiang · Da Yan

China Building Energy Use and Carbon Emission Yearbook 2021 A Roadmap to Carbon Neutrality by 2060

Shan Hu Department of Building Science and Technology Tsinghua University Beijing, China

Yi Jiang Department of Building Science and Technology Tsinghua University Beijing, China

Da Yan Department of Building Science and Technology Tsinghua University Beijing, China

ISBN 978-981-16-7577-5 ISBN 978-981-16-7578-2 (eBook) https://doi.org/10.1007/978-981-16-7578-2 Jointly published with China Architecture Publishing & Media Co., Ltd. The print edition is not for sale in China (Mainland). Customers from China (Mainland) please order the print book from: China Architecture Publishing & Media Co., Ltd. © China Architecture Publishing & Media Co., Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publishers, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publishers nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publishers remain neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

2020 is an unforgettable year in human civilization. China has been the first country to win the battle against the pandemic despite its constant rebound. There have been zero confirmed case in China for a month in the midst of the pandemic onslaught in other parts of the world. The successful containment of the spread of the virus is a testament of China’s magnificent strength, and it reflects how human beings have tried, time and time again for hundreds of years, to ward off the infectious virus of various kinds, which is conducive to disaster relieve and contingency respond in the future. On September 22, 2020, President Xi Jinping announced China’s strategy on mitigating climate change during United Nations General Assembly, that China will strive to reach carbon peak by 2030, with a fight to reach a target of carbon neutrality by 2060. Since then, President Xi has reiterated the dual carbon target on six different international events, and it has been emphasized on the recent China’s annual economic meeting during the plenary session of the 19th National People’s Congress of the Communist Party of China. The dual carbon target has laid a solid foundation and act as a momentum for China’s energy transformation, which will leave a lasting impact in China’s society, economy, and culture for forty years to come. Energy transformation and carbon neutrality are going to have a huge impact on building sector, which is one of the biggest energy consumers in China, with industry and transportation being the other two big energy consumers. It remains an important task to the relative departments of the government to achieve carbon peak and carbon neutrality in building sector, which will be keenly observed by the practitioners in this field. Under such background, this report dissects the target of carbon neutrality in building sector, including discussion on the carbon neutrality pathways and its impact on the building sector as a whole. Energy transformation, in its essence, is to transform the source of energy from carbon-based fossil fuel into zero-carbon-based renewables. The reconstruction of the energy system will lead to the reform of energy conversion, transmission, and services, which will result in changing how terminal energy is used. For the building sector, it means abandoning some of the previous

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Preface

patterns that had been actively promoted in the past, such as “coal to gas” conversion, natural gas-based combined cooling heat and power (CCHP), and other methods that rely on fossil energy. In the meantime, priority will be given to the research and study on zero-carbon development such as solar PV in buildings, energy storage, and flexible use of electricity. To promote zero-carbon development, buildings need to become more than an energy consumer, but an energy prosumer to produce, consume, store energy and adjust the balance between energy supply and demand. These change will lead to a transformation of building construction and operation, retrofitting, and maintenance in China. Lastly, I want to thank you, the readers, for your constant support. Let us work together to make this report an integral part of achieving the great goal of carbon neutrality in the building sector. Heqingyuan, China March 2021

Yi Jiang

Acknowledgements (TBD)

This publication was prepared by the Building Energy Research Center (BERC) of Tsinghua University. The lead authors were Dr. Shan Hu, Prof. Yi Jiang, and Prof. Da Yan. Other authors also contributed important sections for this report, and they were Yang Zhang (3.1, 3.3, 3.4), Ziyi Yang (3.2, 4.1, 4.4), Ao Luo (4.2), Xuyuan Kang (4.4), Mingyang Qian (4.5). The report was edited by Jing Dou from Springer Press. Special thanks go to reviewers and contributors: TBD by Springer. The research of this report was supported by National Key R&D Program of China “Research and Integrated Demonstration on Suitable Technology of Net Zero Energy Building” (grant no. 2019YFE0100300), Youth Program of National Natural Science Foundation of China (grant no. 51908311), National Natural Science Foundation of China (grant no. 51778321), and State Key Laboratory of Air-conditioning Equipment and System Energy Conservation (ACSKL2020KT04).

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Building Energy Research Center of Tsinghua University

The Building Energy Research Center (BERC) was founded in 2005 at Tsinghua University. The mission of BERC is devoted to the development of energy-efficient and environmentally responsible buildings in China in accordance with national and international energy and environmental targets, including buildings research and innovation. The principal research activities within BERC include: • Assessment of the current buildings status in China and the provision of strategic outlooks on buildings energy consumption and efficiency. • Occupant behavior and building simulation research. • Research and development (R&D) of innovative high-efficiency buildings technology and systems. • Energy efficiency application research on subsectors, including space heating in Northern China; rural residential buildings and urban residential buildings; and public and commercial buildings. Since 2007, BERC has published ten Annual Report on China Building Energy Efficiency to provide data reference and technical and policy suggestions to policy makers and engineers in the building energy conservation sector. BERC is also involved in international exchange and cooperation, including ongoing collaboration with the International Energy Agency.

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Executive Summary

Achieving Carbon Target Will Lead to a Revolution of Building Sector China’s central government has announced the mid- and long-term climate targets of carbon peaks by 2030 and carbon neutrality by 2060. Low-carbon development is not only the task for the energy sector but also for all sectors. It will be the largest influencer for socioeconomic development for the next four decades in China. The dual carbon targets set forth by the central government are very clear and need to be achieved on time. Currently, the direct carbon emission of the building sector has already peaked, whereas the indirect one from electricity use and heating will be peaked by 2030. To achieve carbon peak in the building sector at an early date, we recommend large-scale electrification transformation for building energy use and strengthen energy efficiency of new buildings while retrofitting existing ones and promote green living while practicing frugality. To realize zero-carbon emission in building sector, we recommend building new type of building energy system with distributed photovoltaic, distributed energy storage, low-voltage DC distribution network, and flexible load control. Key technologies and related research on new rural energy system based on distributed photovoltaic, combined with water and power generation based on recovered heat from nuclear and cross-seasonal heat storage, need to be promoted and implemented at a faster pace.

Reduce Direct Carbon Emission of Building Sector Needs Electrification In 2019, there were 600 million tons CO2 emitted from building operation directly. Two hundred million tons CO2 emission were caused by urban cooking, roughly 300 million tons from household gas-fired and coal-fired heating, and 100 million tons

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Executive Summary

came from direct emission of gas-fired water heating, steam boilers, and absorption refrigeration. Rural areas accounted for over half of the total CO2 direct emission. The key to zero-carbon direct emission of building sector lies in the pace and the penetration of electrification transformation. According to the analysis, 80% of the electrification endeavor will not lead to more cost, and the investment on electrification apparatus will be paid back in 5 years. Therefore, cost should not be a concern during electrification transformation, but the awareness and the traditional culture of cooking are the main barrier to this cause. Priority should be given to the promotion of the benefit of electrification of buildings and “switching from gas to electricity” for new and existing buildings, so as to achieve zero-carbon direct emission of building sector.

Reduce Indirect Carbon Emission from Electricity PEDF Buildings In 2019, the aggregate electricity consumption of China’s building sector amounted to 1890 Twh, emitted 1.1 billion CO2 indirectly. China’s per capita power use is onesixth of the USA and Canada, around one-third of France and Japan. The per unit area electricity consumption is one-third of the USA and Canada. The difference of lifestyles and building operation contributes to the major difference between China and other developed countries. In recent years, the surge of building power use has led to more carbon emission, which surpassed the rate of decline of carbon emission based on lowering emission factors. The building indirect carbon emission from power use will continue to grow, and it has yet to reach peak level. It is important to promote green lifestyle and encourage the general public and building sector to practice frugality so as to avoid the spike of energy consumption in tandem with fast economy growth, which was an old path of other developed countries. On top of that, it is also important to promote new electricity system featuring distributed photovoltaic, distributed energy storage, low-voltage DC distribution network, and flexible load control. Through the wide-spread implementation of distributed photovoltaic, distributed energy storage, low-voltage DC distribution network, and flexible load control, zero-carbon emission in the building sector will be reached at an earlier date than the power decarbonization in Chia.

Reduce Indirect Carbon Emission for Heating Require Zero-Carbon Heat Supply In 2019, the total floor area for NUH was 15.2 billion m2 and the indirect carbon emission of heating during building operation was 440 million tons of CO2 .

Executive Summary

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Recently, the heating demand and heating area of NUH region have been growing continuously, yet the energy consumption for heating per each square meter has been decreasing while its indirect carbon emission has been growing gradually. The indirect carbon emission for heating during building operation will reach its peak, on the condition that energy efficiency will be improved, the potential of low-grade residual heat resources will be tapped, and distributed coal-fired boilers will be phased out. As government continues to usher in zero-carbon transformation on thermal power in China (CCUS and biomass alternatives), the indirect carbon emission of heating during building operation will be achieved in tandem with zero-carbon trend of the grid as a whole. To reach this end, we should strengthen the standard for existing buildings while improving energy efficiency of the old ones, so as to lower the heat consumption of NUH in the winter from 0.35 GJ/m2 to 0.3 GJ/m2 , which will alleviate the pressure of heat source supply for heating. Between 2020 and 2035, terminal renovation of district heating system should be the main method to reduce the temperature of return water, and it will also effectively facilitate the recovery of residual heat from power plant as well as low-grade residual heat. The increasing heating demand of buildings will be met by tapping the full potential of existing heat source supply. CHP transformation will be implemented on nuclear power plant at coastal areas in the north, which will provide enough heat source to the hinterland areas adjacent to the 200 km of coastline. Starting from 2035, it is suggested to carry out cross-seasonal heat storage projects in tandem with the phase out of thermal power plant, so as to solve the issue of decreasing heat power. Then by 2045, residual heat from nuclear, thermal power for ramping service, and low-grade residual heat will be collected annually through the cross-seasonal heat storage capability. In this way, zero carbon of the grid as well as zero carbon for building indirect carbon emission for heating can be achieved.

Seize the Opportunities and Challenges The concept of ecological civilization is the basis for accomplishing these tasks. To achieve carbon neutrality, revolutionary changes must be implemented in all areas regarding types of energy, ways to use energy, building materials and structures, and cooling methods of air conditioning. Only through these fundamental changes will it be possible to eliminate or neutralize building-related GHGs. These revolutionary changes, in turn, are driving technological forces across the board. Thus, carbon reduction and carbon neutrality do not constrain economic development; rather, they break the deadlock in technological and economic development, opening up new frontiers that can feed disruptive technologies and facilitate leapfrogging across the industry. Seizing this opportunity for development brought about by these tasks and looking at the development of the industry from a new perspective will enable us to see many issues more clearly and thus develop completely different solutions to promote revolutionary changes.

Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

2 Carbon Neutrality Pathways for China’s Building Sector . . . . . . . . . . 2.1 Director Carbon Emission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Cooking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Domestic Hot Water (DHW) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 Heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 Gas Boilers and Others . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Indirect Carbon Emission from Electricity and Heat . . . . . . . . . . . . . 2.2.1 The Zero-Carbon Electricity Production Landscape and the Importance of Energy Conservation . . . . . . . . . . . . . . 2.2.2 The Building Sector Should Change from an Energy Consumer into an Active Contributor to Wind and Solar Power Development. . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Methods to Achieve Zero-Carbon Heating . . . . . . . . . . . . . . . 2.3 Carbon Emissions from the Construction of Buildings . . . . . . . . . . . 2.4 Non-CO2 Greenhouse Gas Emissions . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Eco-civilization Concept Should Be the Foundation . . . . . . . . . . . . . 2.6 The Pathway to Zero-Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 China’s Building Energy Use and GHG Emissions . . . . . . . . . . . . . . . . . 3.1 Basic Situation of China’s Building Sector . . . . . . . . . . . . . . . . . . . . . 3.1.1 Urban and Rural Demographic . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Building Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Global Energy Use and gGHG Emissions in the Building Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Energy Consumption of China’s Building Sector . . . . . . . . . . . . . . . . 3.3.1 Embodied Energy of Building Sector . . . . . . . . . . . . . . . . . . . 3.3.2 Energy Use During Building Operation . . . . . . . . . . . . . . . . .

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3.4 GHG Emission of Building Sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Embodied CO2 Emission of Building Sector . . . . . . . . . . . . . 3.4.2 CO2 Emission During Building Operation . . . . . . . . . . . . . . . 3.4.3 Other GHG Emission in Building Sector . . . . . . . . . . . . . . . .

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4 Urban Residential Buildings Energy and Emissions . . . . . . . . . . . . . . . 53 4.1 Urban Residential Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2 Envelope Retrofitting of Northern Urban Residential Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2.1 Distribution and current heating demand . . . . . . . . . . . . . . . . 62 4.2.2 Standards and Significance of Building Envelope Retrofit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.2.3 Upgrading Techniques of Building Envelopes and Upgrading Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.2.4 Recommendations for the Future . . . . . . . . . . . . . . . . . . . . . . . 73 4.3 Natural Gas Use in Urban Residential Buildings . . . . . . . . . . . . . . . . 74 4.3.1 Household Natural Gas Use and Distribution in Urban Residential Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 4.3.2 Electrification of Cooking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.3.3 Electrification of DHW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 4.4 Electricity Use in Urban Residential Buildings . . . . . . . . . . . . . . . . . . 85 4.4.1 The Total Electricity Consumed by Urban Households . . . . 85 4.4.2 Per Household Electricity Consumption . . . . . . . . . . . . . . . . . 86 4.4.3 Difference in Lifestyle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 4.4.4 The Future of Electricity Consumption in Urban Residential Housing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 4.5 Multi-split Air Conditioning Systems in Urban Residential Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.5.1 The Use of Multi-Split Air Conditioning Systems in Urban Residential Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.5.2 Comparison of Multi-split and Split Air Conditioning in Urban Residential Buildings . . . . . . . . . . . . . . . . . . . . . . . . . 102

List of Figures

Fig. 2.1 Fig. 2.2 Fig. 2.3 Fig. 3.1 Fig. 3.2

Fig. 3.3 Fig. 3.4 Fig. 3.5

Fig. 3.6

China’s per unit GDP energy use and per unit energy use carbon emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PEDF power distribution system . . . . . . . . . . . . . . . . . . . . . . . . . . Seawater desalination and water-heat co-generation system with cross-season energy storage function . . . . . . . . . . . . . . . . . . Population growth in China (2001–2019) . . . . . . . . . . . . . . . . . . . Newly built and demolished building stock of civil buildings in China. Source The newly built building stock data of this report are based on the China Statistical Yearbook on Construction. Demolished building stock is estimated by the model, with data from the China Statistical Yearbook on Construction, 2018 Report of China Construction and Demolition Waste Disposal Industry, 2019 Outline on China Construction and Demolition Waste Recycle and Disposal Industry, and Annual Report on Comprehensive Utilization of Resources in China (2014) . . . Newly built building stock of P&C buildings according to different functions (2001, 2019) . . . . . . . . . . . . . . . . . . . . . . . . China’s existing building stock (2001–2019) . . . . . . . . . . . . . . . . Per capita building stock in China and other countries. Source IEA Buildings Summary, World Bank WDI database, Odyssee Mure database(2018), ERI database, US, NRCA, Canada, Energy Use Data Handbook Tables (2017), Database of Ministry of Land, Infrastructure, Transport and Tourism, Japan, Summary of architectural statistics for 2018, South Korea, Satish Kumar (2019), India . . . Types and boundaries of energy use and greenhouse gas (GHG) emissions in the building sector . . . . . . . . . . . . . . . . . . . .

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Fig. 3.7

Fig. 3.8

Fig. 3.9

Fig. 3.10

Fig. 3.11

Fig. 3.12

Fig. 3.13

Fig. 3.14 Fig. 3.15 Fig. 3.16 Fig. 3.17

List of Figures

Global terminal energy use and CO2 emissions in the building sector (2019). Source International Energy Agency, 2019 Global status report for buildings and construction. The construction sector includes civil buildings, production buildings and infrastructure construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . China’s building energy use and CO2 emissions (2019). Source Building Energy Research Centre, Tsinghua University. The construction sector refers to civil buildings, production buildings and infrastructure construction . . . . . . . . . . Comparison of building operational energy use between China and the world. Source IEA World Energy Statistics and Balances, IEA Buildings Summary, World Bank WDI database, Odyssey Mure database (2018), ERI database, US, NRCAN, Canada, Energy Use Data Handbook Tables (2017), database from the Ministry of Land, Infrastructure, Transport and Tourism, Japan, Summary of architectural statistics for 2018, South Korea, Satish Kumar (2019), India. The electricity consumption of different countries was converted to primary energy use based on the coal consumption of generating stations of different countries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of carbon emissions from building operations between China and the world (2018). Source Result from 2018 IEA CO2 emissions from fuel combustion database, and 2019 BERC model-based estimation . . . . . . . . . . . Comparison of per capita carbon emissions of different countries (2018). Source Results of the 2018 IEA, CO2 emissions from the Fuel Combustion 2019 Highlights 2019 database, and 2019 BERC model-based estimation . . . . . . Embodied energy use of China’s civil buildings (2004– 2019). Source BERC Tsinghua University. Only for civil buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Embodied energy consumption of China’s construction sector (2014 ~ 2019). Source Calculation from BERC, Tsinghua University. Construction sector, including civil building, production building and infrastructure construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Total energy use and per value added energy use of the manufacturing sector in . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy use structure of the manufacturing industry in China and selected developed countries . . . . . . . . . . . . . . . . . . Per value added energy use of selected subindustries of the manufacturing industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy consumption for building material production . . . . . . . . .

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List of Figures

Fig. 3.18 Fig. 3.19 Fig. 3.20 Fig. 3.21 Fig. 3.22

Fig. 3.23 Fig. 3.24 Fig. 4.1 Fig. 4.2 Fig. 4.3

Fig. 4.4

Fig. 4.5 Fig. 4.6 Fig. 4.7

Fig. 4.8 Fig. 4.9 Fig. 4.10 Fig. 4.11 Fig. 4.12 Fig. 4.13

Primary energy consumption and total electricity use for building operation in China (2001–2019) . . . . . . . . . . . . . . . . Energy use of building operation in China (2019) . . . . . . . . . . . . Trend of total energy use and energy intensity for different subsectors (2001–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Embodied carbon emissions of civil buildings. Source BERC Tsinghua University. Only for civil building . . . . . . . . . . . Embodied carbon emissions of the construction sector in China (2004–2019). Source BERC Tsinghua University. The construction sector includes civil buildings, production buildings and infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CO2 emission of building operation (2019) . . . . . . . . . . . . . . . . . CO2 emissions from China building operation (2019) . . . . . . . . . Urban residential building floor space in different years (1990–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Urban residential building floor numbers in different years (1990–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unit space for China’s residential buildings in urban areas (based on the demographic census conducted in 2015 on 1% of the population, sample size: 155,158 households) . . . . Unit space for China’s residential buildings in urban areas in different provinces (based on the demographic census conducted in 2015, sample size: 155,158 households) . . . . . . . . . Total floor space of China’s urban residential buildings (2000–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scaling up of China’s urban residential buildings (2001– 2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Building floor area between China and other countries. Source Odyssee Mure database, US Energy Information Agency database, database of Ministry of Land, Infrastructure, Transport and Tourism of Japan, IEA Buildings Summary, Satish Kumar (2019), NRCAN Energy Use Data Handbook Tables, Canada . . . . . . . . . . . . . . . . . China’s residential housing completion year distribution (2015 census) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Construction year distribution of residential buildings in China’s city area (2015 census, city) . . . . . . . . . . . . . . . . . . . . . Construction year distribution of residential buildings in China’s town area (2015 census, town) . . . . . . . . . . . . . . . . . . . Construction year distribution of residential buildings in China’s rural area (2015 census, rural) . . . . . . . . . . . . . . . . . . . The distribution of the year of completion for urban residential buildings in China (2015, model estimation) . . . . . . . Building floor areas for energy-saving reconstruction in northern China during the 12th Five-Year-Plan period . . . . . . .

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56 56 57

59 59 60 60 60 61 62

xx

Fig. 4.14 Fig. 4.15

Fig. 4.16 Fig. 4.17 Fig. 4.18 Fig. 4.19

Fig. 4.20

Fig. 4.21

Fig. 4.22

Fig. 4.23 Fig. 4.24 Fig. 4.25 Fig. 4.26 Fig. 4.27 Fig. 4.28 Fig. 4.29 Fig. 4.30 Fig. 4.31 Fig. 4.32 Fig. 4.33 Fig. 4.34 Fig. 4.35 Fig. 4.36

List of Figures

Average heat demand per unit area of different types of residential buildings in some cities . . . . . . . . . . . . . . . . . . . . . . Distribution of heat demand per unit area in some cities with no energy-saving standard and the energy-saving standards for third-stage buildings are adopted . . . . . . . . . . . . . . . Comparison of actual heat demand in different types of buildings in Chifeng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Photos of the buildings tested . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy savings per unit area for each upgrading method . . . . . . . Static payback period for energy efficiency upgrading methods at different heating costs for various types of residential buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of natural gas consumption between self-heating and non-self-heating households in Beijing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Histogram of the distribution of average household gas consumption in non-self-heating residential buildings in Beijing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Distribution diagram of the distribution of average household gas consumption in non-self-heating residential buildings in Beijing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Changes in gas consumption in non-self-heating buildings . . . . . Distribution of household cooking energy use in Beijing (2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . China’s gas penetration rate (gas-using population/resident population) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cooking habits of Beijing households (2018) . . . . . . . . . . . . . . . . Domestic sales of various types of electric cookware in China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main uses of energy in Beijing households . . . . . . . . . . . . . . . . . . Ownership of domestic hot water equipment in Beijing . . . . . . . Distribution of domestic hot water equipment in Beijing . . . . . . . Distribution of domestic hot water equipment in Shanghai . . . . . Domestic hot water usage in Beijing in 2018 . . . . . . . . . . . . . . . . Comparison of water consumption between Chinese and foreign households (L/household/day) . . . . . . . . . . . . . . . . . . Total urban residential electricity consumption in China (2001–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Urban residential electricity consumption per capita and per household (2001–2019) . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameters of total annual electricity consumed by urban residential users in six cities in Jiangsu Province (total sample size: 83,243 households) . . . . . . . . . . . . . . . . . . . . . . . . . .

63

64 67 68 71

72

74

75

76 76 77 78 78 79 80 81 81 82 82 83 85 86

87

List of Figures

Fig. 4.37

Fig. 4.38

Fig. 4.39 Fig. 4.40 Fig. 4.41 Fig. 4.42 Fig. 4.43 Fig. 4.44

Fig. 4.45 Fig. 4.46 Fig. 4.47 Fig. 4.48 Fig. 4.49

Cumulative distribution chart of total annual electricity consumed by urban residential users in six cities in Jiangsu Province . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of average annual household electricity consumption in each percentile group of residential buildings in six cities in Jiangsu with average annual household electricity consumption in other countries . . . . . . . . . . Electricity consumed by key appliances in family A and family B (kWh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Daily power curve of electric cooker in family A (W) . . . . . . . . . Daily power curve of smart toilet seat (W) . . . . . . . . . . . . . . . . . . Power curve of the water dispenser for 2 h in a real situation (W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sales volume of China’ kitchen appliances . . . . . . . . . . . . . . . . . . Sales volume of China’s household appliances. Note Microwave oven and dishwasher sales were 100 units in 2014, induction cooker, the sales volume of electric cooker and electric oven were 100 units in 2013. The sales volumes of the air purifier and water purifier were 100 units in 2014. The sales volumes of vacuum machines, smart toilet seats and floor cleaning machines were 100 units in 2013. Source Industry online. . . . . . . . . . . . . . . . . . . . . . . Power curve of a single washing cycle of a washing machine (W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Residential cooling energy consumption in urban areas of China, 2000–2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Statistics on the form of air-conditioning systems in residential buildings in China, 2015 . . . . . . . . . . . . . . . . . . . . . Histogram and statistical pie chart of the simultaneously working hours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air-conditioning usage modes in urban residential buildings in China. The future of cooling in China, 2015 . . . . . . .

xxi

88

89 90 92 92 93 95

95 96 100 101 102 103

List of Tables

Table 2.1 Table 3.1 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9 Table 4.10 Table 4.11 Table 4.12 Table 4.13 Table 4.14

Table 4.15

GWP values for several common refrigerants . . . . . . . . . . . . . . China building energy use (2019) . . . . . . . . . . . . . . . . . . . . . . . . K-values for residential building envelopes under different energy-efficient design standards (unit: W/(m2 K)) . . . . . . . . . . Heat demand of buildings in Beijing under different energy saving scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Average heat consumption per unit area before and after temperature correction . . . . . . . . . . . . . . . . . . . Basic forms of the building envelopes tested . . . . . . . . . . . . . . . Heat consumption per unit area after temperature corrections of different locations of the buildings (GJ/m2 ) . . . . Locations and methods used in the upgrading of buildings . . . . Construction cost for the upgrading . . . . . . . . . . . . . . . . . . . . . . Technical costs and static payback periods for each upgrading method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Estimates of gas consumption for cooking in typical households . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Estimated gas consumption for domestic hot water in a typical household . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of operating expenses of each type of water heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Basic information of the selected families . . . . . . . . . . . . . . . . . Electricity consumption of urban households . . . . . . . . . . . . . . . Statistical indicators of electricity consumption per square meter for cooling in the three climate zones in 2019 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A comprehensive comparison table of multi-split systems and split air conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 42 65 65 66 68 69 70 71 71 79 83 84 90 98

101 103

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Chapter 1

Introduction

Founded in 2005, the Building Energy Research Center of Tsinghua University (BERC), has worked continuously on China’s buildings sector, to comprehensively analyses the current status, unique features and key issues of China’s buildings energy use. The aim of BERC’s research is to understand and reveal the experiences and lessons from global buildings energy comparison, and then to recommend future energy technology and perspectives on China’s buildings energy conservation work as well as provide best practice project demonstration. Since 2007, BERC has published Annual Report on China Building Energy Efficiency, flagging this on-going research work and key data for China’s buildings sector. Those annual reports (2007–2021) show key data for China’s buildings energy use, discuss key issues of technical developing trends, indicate potential policy and technology perspectives and demonstrate best practices in the buildings sector. As China has become increasingly important to global energy strategy and climate change, greater attention both nationally and internationally has been paid to China’s buildings sector. From 2016, BERC released an English version of this annual report, for international researchers who are interested to know about China’s building sector. In this report, China’s building energy and emission status and trend were discussed and updated every year. Four categories of China’s building energy use were defined according to their own characteristics, and every year one category was selected to the topic. In 2021, the topic was urban residential building. Specifically, carbon neutrality pathways for China’s building sector were highlight of this report. Therefore, an individually chapter were discussed on this topic. Therefore, this report includes three parts: Chapter 2 discussed carbon neutrality pathways for China’s building sector, this chapter discussed building sector’s direct emissions, indirect emissions from heat and power, building construction related emission, and non-CO2 emissions, and finally point out future pathways. Chapter 3 updated China’s building energy use and emissions in construction phase and in operation phase. Detailed data on China’s building sector including © China Architecture Publishing & Media Co., Ltd. 2022 S. Hu et al., China Building Energy Use and Carbon Emission Yearbook 2021, https://doi.org/10.1007/978-981-16-7578-2_1

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1 Introduction

population, building stock, total amount and intensity of energy and emissions could be found in this chapter. In this report, the updated data is 2019, limited by national statistics. Chapter 4 is the section focus on one specific building energy use category. As mentioned above, urban residential building is the topic of this report. In this chapter, building stock and envelope performance, gas and electricity use intensity and distribution, and occupant behaviour were analyzed with support from a variety of data sources.

Chapter 2

Carbon Neutrality Pathways for China’s Building Sector

China’s central government has announced the mid- and long-term climate targets of carbon peaks by 2030 and carbon neutrality by 2060. Low-carbon development is not only the task for the energy sector but also for all sectors. It will be the largest influencer for socioeconomic development for the next four decades in China. The building sector, as one of the three largest energy consumers (industry, transportation and building sectors), is responsible for reducing indirect and direct carbon emissions. Reducing carbon emissions in the building sector will lead to a revolution of the overall building sector in terms of methods and modes for building construction, operation, maintenance and retrofitting processes. China’s carbon emissions will hit the carbon peak target by 2030, and the emissions will subsequently decline year by year. The total carbon emission value equals per unit GDP carbon emission multiplied by the GDP value. China’s GDP will continue to increase alongside its socioeconomic development, and the per unit GDP carbon emissions will gradually decrease. Specifically, if GDP grows faster than the per unit GDP carbon emission reduction, then total carbon emissions will increase. Moreover, if the rate of per unit GDP carbon emission reduction is higher than that of GDP increase, then the total carbon emission will decrease. Therefore, the carbon peak occurs when the speed of per unit GDP carbon emission reduction is in tandem with GDP growth. According to the carbon peak timeline, China will also embark on a pathway features high quality, energy efficiency and low carbon development. Currently, China’s GDP growth has reduced to approximately 6%, and it would be difficult to return to 10% per year. However, the energy consumption per unit GDP continues to decrease, and it has been 5–7% since 2014 (see Fig.2.1). As the energy revolution bogs down and the share of zero-carbon energy (nuclear, wind, hydro, solar) increases, the value of per unit GDP carbon emissions equals per unit GDP energy consumption times the carbon emissions on a per unit energy use basis, so the carbon peak indicator can be defined as follows: Carbon peak index = GDP growth rate × Per unit GDP energy reduction × Per unit energy use carbon emission reduction.

© China Architecture Publishing & Media Co., Ltd. 2022 S. Hu et al., China Building Energy Use and Carbon Emission Yearbook 2021, https://doi.org/10.1007/978-981-16-7578-2_2

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120

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20 0 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

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Per unit GDP energy use reduction GDP growth Per unit energy use carbon reduction Carbon peak index

Fig. 2.1 China’s per unit GDP energy use and per unit energy use carbon emissions

If the carbon peak index is above 0, then carbon emissions increase. If it is 0, then carbon emission has peaked. If it is below 0, then carbon emission decreases. The annual GDP since 2010, the trend of per unit GDP energy use and the carbon emissions per unit energy consumption can be found in Fig. 2.1, and it can be concluded that the carbon peak index has been decreasing year on year. Carbon emissions per unit energy use will continue to decline alongside the transformation of the energy sector, and it can be expected that the carbon peak index will reach zero or even below very soon. However, in regard to carbon neutrality, the total carbon emissions should be equal to or less than the total carbon sink. According to research, China’s total carbon sink would probably remain below 1.5 billion tons of CO2 in the future. This is one-seventh of the total CO2 emissions in China. For some sectors, combustion and subsequent CO2 emissions are unavoidable. Therefore, the carbon sink index is mainly used for industries that cannot achieve zero-carbon emissions. Carbon neutrality, for most other sectors, means zero-carbon emissions. Zero emissions shall also be the fundamental target for the building sector to reach carbon neutrality. Compared with the easier target of the carbon peak, it is a huge challenge for the building sector to reach carbon neutrality. Therefore, to realize the dual carbon targets, we shall on the one hand, follow the trend of social, economic and technological

2 Carbon Neutrality Pathways for China’s Building Sector

5

development, and on the other, meet the expectation of the society, market and the people as a whole. Then, we shall look at the optimal and the most appropriate pathway towards carbon peaks and carbon neutrality. What does zero-carbon imply in the building sector? This means that greenhouse gas (GHG) emissions (including CO2 emissions) in the building sector are zero. The building sector in this report can be divided into four categories based on carbon emission research and its definition. The four types of buildings are as follows: 1. 2. 3. 4.

Direct carbon emission of building operation Indirect carbon emission of building operation Embodied carbon emissions of building construction and maintenance Non-CO2 GHG emission of building operation.

2.1 Director Carbon Emission Direct carbon emissions refer to CO2 emitted from coal, oil and gas and other fossil fuel energy during building operation. Electricity and heat are also the main energy sources of buildings, but because these two type of carbon emissions occur outside of buildings, they are called indirect emisson. Currently, there are 64 billion square meters of building space in China’s rural and urban areas. Carbon emissions can be generated though the following methods within the building parameters (including CO2 emissions from fossil fuel combustion):

2.1.1 Cooking Gas-fired stoves have been the major cooking method in urban residential buildings, corporate canteens and restaurants. Whereas in rural areas, the most frequently used cooking fuels are natural gas, coal and firewood-burning stoves. The CO2 emitted from firewood-burning stoves shall not be included in the carbon emission category since it uses biomass as the energy source. Each 1 GJ of heat generated from coal firing produces 92 kg of CO2 , and the amount is 50 kg of CO2 if the heat comes from natural gas boiler. There are 200 million tons of CO2 emitted from cooking each year in China, accounting for approximately 2% of the national total CO2 emitted from the energy sector. Electrification are the best way for the cooking sector to achieve zero-carbon emissions. In recent years, electric stoves of various types have emerged alongside a new round of electrification transformation. Small egg cookers, electric saucepans and frying pans for dining hall kitchens are compatible with different culinary skills while producing the same tasty Chinese food. Based on the amount of caloricity, 0.50 RMB/kWh of electricity is equivalent to 5 RMB/Nm3 of natural gas. Normally, the thermal efficiency of electrified cooking devices can reach over 80%, which is far higher than that of natural gas devices (approximately 40–60%). Therefore, based on the current pricing scheme, the cost of fuel will remain the

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2 Carbon Neutrality Pathways for China’s Building Sector

same after electric cooking devices replace natural gas devices. Hence, the culture of cooking holds the key to successful cooking electrification in China. There should be no major setback to the electrification process once innovation and related education have been in place.

2.1.2 Domestic Hot Water (DHW) The use of DHW is commonplace in urban areas of China. Apart from DHW from solar heating, the shares of gas-fired DHW and electrified DHW are approximately the same. Currently, China’s CO2 emissions for producing DHW have been approximately 80 million tons, close to 1% of the total carbon emissions. Electrification should be the inevitable course for DHW production to achieve low carbon development. There are two kinds of electric water heaters, namely, direct electric water heater and electric heat pump water heater. There are many domestic manufacturers that are capable of producing reliable heat pump water heaters, and their average annual COP values are over 3. Therefore, it takes 48 RMB/GJ to produce 1 GJ of DHW by an electric heat pump water heater (when the electricity price is at 0.50 RMB/kWh), and 86 RMB/GJ to produce 1 GJ of DHW by natural gas (when the gas price is 3 RMB/Nm3 ). As the former method is cheaper than the latter, this will facilitate the process of “switching from gas to electricity”. The cost for electric water heater is 1.6 times higher than that of natural gas. However, the overall cost of electric water heaters is still less than that of natural gas. The main reason is fast hot water production, low cold-water consumption and low pipeline heat loss of electric water heater. Thanks to promotion and avocation, the future for electric water heaters to replace gas heaters is just around the corner.

2.1.3 Heating There are two major types of heating, gas boilers and coal-fire boilers. The latter is often used in rural and suburban areas. Five percent of the Northern Urban Heating (NUH) uses a wall hung gas boiler, and it was used in some of the villages in China’s Northern region as clean heating transformation program. Additionally, more than 70% of the rural residential buildings in the northern part of China are still using coal-fired boilers, which emit 300 million tons of CO2 each year. These are the key to eliminating direct CO2 emissions in the building sector. Apart from those regions where the outdoor temperature could reach as low as −20 °C, the majority of other regions in China are capable of using decentralized air source heat pumps for heating. Air source heat pumps has seen great improvement due to the effort and cooperation from enterprises and research institutes, and it can basically meet most of the heating needs. With the right terminal radiator, the air source heat pump is comparable to the wall hung gas boiler in terms of indoor comfort creation, and the operation cost and

2.1 Director Carbon Emission

7

initial cost. For a few extreme cold regions where the air source heat pump is not applicable, then the operation fee of instant electric heating would be 0.5–1 times higher than that of the gas boiler. Government subsidies are recommended in this case to facilitate the “switching from gas to electricity” for the low-income group.

2.1.4 Gas Boilers and Others Natural gas-driven steam boilers and hot water boilers are used in hospitals, commercial buildings and public buildings. Most of the time, air source heat pumps can replace gas steam boilers as a cheaper alternative. Only a small portion of steam generated from the steam boiler is necessary for disinfection, dry cleaning and cooking purposes, and the rest of the steam is converted to hot water for other DHW scenarios. Therefore, it is reasonable to minimize the hot steam demand and promote the use of hot water produced by a heat pump system. Small electric steam generator can be used for other less frequent steam applications. Downsizing and decentralizing steam generators could lead to a reduction in steam transmission loss and steam leakage. Even though the cost of fuel for electric steam generation is 0.5–1 times higher than that of gas, the actual operation cost will not be as high due to less steam loss. Some of China’s public buildings are still using gas-fired absorption chillers because of the undersupply of power in the past. It produces CO2 directly with a higher operational cost than electric CO2 . Meanwhile, since the COP of the gas-fired absorption chiller is less than 1.3, when the gas price reaches 3 RMB/Nm3 , the cost of cooling is 0.23 RMB/kWh. When the electricity price is at 0.80 RMB/kWh, then the cost of cooling would be less than 0.15 RMB/kWh. Therefore, it would be a huge benefit to reduce direct carbon emissions and lower the operational cost if we could replace the gas-fired direct absorption chiller with an electric chiller. Currently, there are 600 million tons of direct CO2 emissions for China’s building sector. Our previous analysis suggests that the economic and technological challenge for zero direct carbon emissions within the building parameter is virtually nonexistent. Moreover, zero-carbon emissions often lead to low operation costs and sound economic returns. The key here is to shift the paradigm of thinking as well as the culture of cooking. It is important for policy makers and public to be clear that natural gas consumption can also lead to carbon emissions, and the policy of “switching from gas to electricity” is the only way forward to realize zero-carbon emissions in the building sector.

2.2 Indirect Carbon Emission from Electricity and Heat Currently, electricity is the main power source for building operation. In 2019, the aggregate electricity use in China’s building sector was 1890 TWh. Currently, China’s zero-carbon electricity, i.e., nuclear, hydro, wind and solar power, accounts for 30%

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2 Carbon Neutrality Pathways for China’s Building Sector

of the total power production, and the remainder is coal-fired and gas-fired power. In 2019, the CO2 emissions in China were 0.577 kg CO2 per kWh of consumption. Therefore, the indirect carbon emission of building electricity use was 1.1 billion tons of CO2 . District heating is the widely used heating method for NUH, and the heat sources are combined heat and power generation (CHP) and centralized coal-fired and gas-fired boilers. CO2 emissions from coal-fired and gas-fired boilers are indirect carbon emissions. The carbon emissions of CHP are distributed according to the amount of exergy from the generation of power and heat. Hence, the aggregate indirect CO2 emissions from district heating in China’s urban area stood at 450 million tons. In total, there are 1.55 billion tons of indirect CO2 emissions each year from building electricity use and building energy consumption for heating, accounting for 16% of China’s total CO2 emissions. As electricity has been replacing other fuels, the total power consumption will continue to increase. According to the estimation, by 2040, China’s population will plateau at 1.4 billion, with an urban population of 1 billion and 400 million rural residents. The building floor space will reach 75 billion m2 . The building floor space for NUH will be 20 billion m2 , which will lead to power and heat increases for building operation. As a result, indirect CO2 emissions will surge. Indirect carbon emissions caused by power and heat supply in the building sector are the mainstay in building-related carbon emissions. Therefore, we need to give top priority to indirect carbon emission reduction and zero-carbon emission or carbon neutrality in the building sector. We must change the way we produce electricity and heat, and strive to reach zero-carbon emissions and carbon neutrality. The target of carbon neutrality can be achieved for future electricity production, if zero-carbon power (nuclear, hydro, wind, solar and biomass power) became the mainstream, and coal-fired and gas-fired electricity as the supplement, with technologies such as carbon capture and carbon storage used for CO2 treatment. Then, let us look at the possibility for China to reach zero-carbon electricity production in the future.

2.2.1 The Zero-Carbon Electricity Production Landscape and the Importance of Energy Conservation Currently, there is 60 GW of nuclear power in the eastern coastal area of China. Based on China’s future plan for nuclear power, the maximum capacity is going to be less than 200 GW, with 1500 TWh of annual power generation capacity. Therefore, nuclear power plants can be found in every possible location along the cost, stretching from Yangjiang Nuclear Power Station and Daya Bay Nuclear Power Plant in the South of Guangdong province to Hongyanhe nuclear plant in the North of Dalian province. China boasts abundant water resource. However, China’s installation capacity for hydropower projects is approaching the upper limit of 500 GW (excluding the

2.2 Indirect Carbon Emission from Electricity and Heat

9

Tibetan Plateau), or 2500 TWh of annual electricity production. Currently, it stands at 400 GW with 2000 TWh of annual electricity production. Biomass energy development in China is still insufficient. Only millions of tons of coal equivalent of biomass energy products have been produced and consumed each year. According to statistics, the aggregate biomass energy in China could reach 1 Gtce. As the only zero-carbon fuel source in future energy systems, we need to prioritize industries that need fuel the most. Biomass can generate 0.3–0.4 Gtce for electricity production, generating 1000 TWh of power annually. The celling for reliable and efficient nuclear and hydropower would be 700 GW, generating 4000 TWh of electricity. With the addition of biomass power in the future, China’s zero-carbon electricity could reach 900–1000 GW, producing 5000 TWh of power each year. In 2019, China’s total power supply registered at 7200 TWh. If we can secure 5000 TWh of zero-carbon electricity in the future, then the remaining 2200 TWh of power can be produced through wind (including offshore wind power) and solar power. Currently, the total capacity of wind power and solar power in China all surpasses 200 GW, with 1200–1500 h of running time each year, so the total power generation from wind and solar power would be approximately 600 TWh. The 2200 TWh zero-carbon power gap can only be filled with at least 1500 GW of wind and solar capacity. The greatest challenge towards wind and solar power would be the issue of adjusting the load. Based on the current power structure and regulation mechanism and the randomness of wind and solar power, we need at least 70% adjustable wind and solar power to meet the balance between power supply and demand. This means that of all 1500 GW of power, we need 1000 GW as reserve power to deal with possible peak and valley regulation. Due to the low economic nature of nuclear operation as a peak regulating power supply, it should only be considered as a base load of power supply. Although hydropower is an ideal way to this end, its total amount is only 500 GW. Even if we can find an additional 100 GW of power from pumped hydro plants, we still need 400 GW from thermal plants using biomass, with a 2000-h annual running time. Once we can give full play to nuclear, hydro, pumped hydrostorage, wind, solar and biomass power plants, it would be possible for us to generate enough zero-carbon electricity to meet the 7200 TWh of demand. However, it would be a challenge if the total electricity demand increases significantly. Nuclear, hydrobiomass thermal power is already reaching its limit, so wind and solar power are the only hopes to meet the extra demand. However, the difficulty of bringing the capacity of wind and solar to the next level can be described as follows: The first is the space resource limitation of wind and solar power. As low-density energy sources, the energy densities of wind and solar power are approximately 100 W/m2 . The annual 8000 TWh of wind and solar demand in the future requires more than 6000 GW of installation capacity with 60 billion square meters of land, which equals 60,000 km2 of land. It is not difficult to find such an amount of land in the desert region of West China. However, a large amount of adjustable power capacity is required to balance the power supply and demand. Long-distance transmission is

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2 Carbon Neutrality Pathways for China’s Building Sector

also required for a large amount of power. However, as we mentioned before, there are only 1000 GW of zero-carbon electricity potential for us to tap, which is far from the 6000 GW of adjustable power capacity. As a result, we have yet to find an appropriate solution to develop large amounts of wind and solar power in remote areas. On the other hand, we could only arrange 500–1000 GW of wind and solar power in the northwest region of China and leverage thermal power based on biomass and abundant water resources for power capacity adjustment. In coastal areas, 500 GW of offshore wind power is developed. Then, we could use rooftop PV panels to generate electricity, as well as a few other vacant spaces in the mid- and western regions of China for wind and solar power. There is 25 billion m2 of available rooftop space for China’s building sector. Therefore, with an additional 25 billion square meters of land in other areas of China, which equals 25,000 km2 of land, we can develop enough solar and wind power in different forms. If wind and solar power are developed on buildings’ rooftops and in vacant space, then it is possible for us to develop distributed power storage and flexible power load to counter the random nature of wind and solar power and subsequently solve the issue of mismatch between demand and supply. While the power load variation and the ups and downs of wind and solar are partially overlapping, if we can change the current mode of integrated generation, transmission and distribution, and switch to distributed generation, self-generation and consumption, distributed regulation, then it is possible for us to decrease the power demand for wind and solar from 70 to 40 to 50%, or relaying on daily power storage equivalent to 70% of wind and solar power generation. If we can have 5000 GW of distributed wind and solar power in the midand eastern regions of China with 7500 TWh of annual power generation, then we would have 2500–3000 GW of power for load regulation, coupled with 20 TWh/day of power storage capacity, and then the issue of wind and solar variation can be solved. As China is ramping up the development of electronic vehicles (EVs), if there are 200 million EVs with an average battery capacity of 50 kWh in the future in China, this would mean that we would have 10 TWh/day of power storage and 2000 TWh of charge–discharge power. If distributed batteries and PV, energy storage, direct current and flexible power use can be equipped to 30 billion µm of building floor areas in China, we would have 600 GW of power for load regulation. With a number of additional interruptible industrial consumers, we can basically provide 5000 GW of distributed wind and solar power for load regulation. In this scenario, it is possible to reach 13,000 TWh of annual power generation from nuclear, hydro and biomass, together with 6000 GW of wind and solar capacity (1000 GW from the west, 5000 from the mid- and eastern regions), producing 8000 TWh of power. However, it is still a very challenging task because we have to tap the full potential of all the resources; otherwise, it would be impossible to reach the 13,000 TWh target. The goal of zero-carbon electricity will be even harder to achieve if the power demand increases significantly. Due to the insufficient water resources and biomass thermal power for peak and valley regulation, we need various methods for power storage, such as chemical storage, electrolysis of water to store hydrogen to cope with daily variations in wind and solar power, and wind and solar

2.2 Indirect Carbon Emission from Electricity and Heat

11

shortages caused by weather changes. We also need enough power for load regulation in the winter due to wind and solar shortages in this season. Biomass is the most reasonable method to cope with the seasonal variation in thermal power and the basis for load regulation between and within different seasons. The energy storage demand for cross-seasonal load regulation is dozens of times higher than the energy storage demand for daily load regulation. Therefore, large-scale battery storage and hydrogen storage technology are not suitable for cross-seasonal load regulation. It is difficult to tap into the already limited biomass energy for load regulation. The 0.4 Gtce of thermal power from biomass was the upper limit. However, if the annual wind and solar power demand is 10,000 TWh and the total electricity consumption is 15,000 TWh per year, then the current energy structure is unable to cope with such demand. One of the possible solutions is to find more space for wind and solar installation to meet the power demand for winter, which will also lead to the curtailment of wind and solar power in spring, summer and autumn. Consequently, the return on investment of extra wind and solar power for winter consumption is very marginal. Another solution could be thermal power reserves by using largescale carbon capture and storage (CCS) and carbon capture utilization and storage (CCUS) to retrieve the CO2 emitted from the thermal power generation process. However, this requires considerable investment, and there is no feasible way of storing a large quantity of CO2 underground or capturing it with building materials. The method of thermal + CCS or renewable curtailment leads to extremely low returns, which should be considered the last resort. Based on the existing conditions of hydro, nuclear and biomass, if we can contain annual electricity consumption within 12,000–13,000 TWh through advanced energy efficiency methods, then it is unnecessary for us to turn to the last resort methods. It is totally possible for China to reach a high level of modernization and become a more powerful country with 12,000 TWh of annual electricity consumption by improving energy efficiency and changing the way we live and work. More detailed research at our center will be published and reviewed in the near future. The most important precondition for carbon neutrality in the building sector, as one of the three largest energy consumers (industry, transportation, building sector), is to improve energy efficiency. Under the energy efficient mode, rural and urban buildings would consume 3500 TWh of the total 12,000 TWh of power in the future, which means that there is still 80% more potential left for the building sector to grow, given that the building sector consumed 1900 TWh of power in 2019. This will facilitate full electrification for China’s building sector (excluding NUH). It will also cover various additional power demands due to the increase in urban demographics from 800 million to 1 billion (25%), the policy of “switching from gas to electricity” (30%) and additional electricity demand stemming from livelihood and building service improvement. The future population of China will be approximately 1.4 billion, which means that the per capita building operation power use will be 2500 kWh. Allocating the total amount into different sectors: the per household power consumption of residential buildings should be 3500 kWh/hh, and the electricity intensity of public buildings of different types will be 60 kWh/m2 . This is significantly lower than the energy intensity in US, Japan, western and northern European countries but still far higher

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2 Carbon Neutrality Pathways for China’s Building Sector

than the status quo of China. To usher in the development of ecological civilization, we need to plan the future of the building sector scientifically and rationally. It is important to uphold the “part time and part space” energy saving model and refrain from wasting building energy. These should be the fundamental principles for our modernization endeavor and carbon neutrality in the future.

2.2.2 The Building Sector Should Change from an Energy Consumer into an Active Contributor to Wind and Solar Power Development. As mentioned previously, buildings are important space resources for developing wind and solar electricity. Distributed solar PV on rural and urban rooftops and other available areas can greatly solve the issue of space limitations. It should be a priority for building designs to fully leverage the building surface to develop PV, and the coverage rate of PV on the building surface should be considered as one of the criteria to determine green and energy efficient buildings. Apart from developing building integrated PV, the building sector also shoulders another important mission in the zero-carbon endeavor, which is consuming wind and solar power. One of the features of building PV power is that it changes in tandem with solar radiation during the daytime. Power generation in the middle and eastern regions of China also varies according to daily weather changes. These changes are not exactly in line with the shifting of power demand, which is the key reason to develop power storage capacity as a countermeasure. The powerful combination of buildings plus surrounding parking lots is fully capable of storing a large quantity of energy in a distributed fashion, which could be immensely useful in the future for zero-carbon development. Based on the principle of developing photovoltaics, energy storage, direct current and flexible use of power (PEDF), it is possible to match the daily supply of electricity from renewables with daily power demand. The basic principle of PEDF can be seen in Fig. 2.2. The distribution system is connected to the grid through an AC/DC converter. In this way, the power demand for the building sector can be met based on the integrated battery system connected to the batteries on the EV, which are connected to smart charging piles. The AC/DC converter is able to adjust the power transmission to buildings in real time. When enough electric vehicles are connected and enough batteries are equipped, any instant power from the external AC network can be adjusted from zero to the maximum power according to the requirements, which has no direct relation with the actual power demand in the building at that specific time. In this way, buildings with PEDF can be directly regulated by signals from wind and solar platforms, and the AC/DC of each building can be attended to at every moment based on the power in each wind and solar platform. If buildings with PEDF have enough storage and regulation capacity with grid connections through wind and solar power generation platforms at every moment of electricity consumption, it would be fair for us to extrapolate that

2.2 Indirect Carbon Emission from Electricity and Heat

13

Fig. 2.2 PEDF power distribution system

the electricity consumed by this building is entirely from wind and solar power and has nothing to do with the share of wind and solar power in the external power grid. There will be at least 200 million EVs (excluding taxi cabs) in China in the future. The battery in each existing EV in China is approximately 50–70 kWh per car. According to statistics, 80% of these EVs are in parking lots, and only 20% of these EVs are on roads at any given time. If all the parking EVs are connected to charging piles, which are also connected to the “PEDF” buildings close by, then this would mean a daily storage capacity of 10 TWh. If there is 45 billion m2 of floor space for a “PEDF building” in China, with a 10 kWh battery per 100 m2 , then we would have an additional 4.5 TWh of power storage capacity per day. The combination of building and charging piles can deliver 3000 GW of maximum daily charging capacity, which translates to 6 h of average charging time per day to ensure that the EVs are fully charged. Thus, the power demand of 200 million EVs across 45 billion m2 can be met. The annual electricity consumption for 200 million cars is approximately 400 TWh. 2000 TWh of electricity is consumed by 45 s each year, which will be approximately 35–40% of the total wind and solar power in the future. If 30% of our wind and solar power comes from the Gobi areas in China’s northeast regions, then it will be transmitted to the eastern region based on hydropower, in addition to meeting the local power demand in northeast regions. Another 70% of wind and solar power will be generated from the middle and eastern regions of China. The “PEDF buildings” and EVs in the parking space will consume half of those powers, which could be a solution to digest the large amount of residual wind and solar electricity. There will be 75 billion m2 of additional floor space in China’s building sector, among which 35 billion m2 will be urban residential buildings, 20 billion m2 will be rural buildings, 12 billion m2 will be office and school buildings, and 8 billion m2 for other commercial, transportation, cultural and sport buildings. It is suitable to promote PEDF in residential, rural buildings and office and school buildings. If two-thirds of those categories can be switched to PEDF, then the total floor space would be 45 billion m2 .

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2 Carbon Neutrality Pathways for China’s Building Sector

It is important to note that there is no power transmission from the PEDF buildings and the EVs to the grid under the current scenario. The PEDF buildings and EVs only act as a platform for distributed power storage using wind and solar power from the grid, sparing the effort and the additional impact of massive redesigning of the grid. Therefore, there is no need to create more distribution capacity to incorporate another 200 million cars with 2000–4000 GW of additional power. For cloudy days and windless days, the daily max–min load difference can be compensated by the 200 million additional cars and 500–600 GW of thermal power, and the CO2 can be captured through CCS. As China has ramped up the capacity of thermal power generation, it would be the most reasonable strategy to reserve a certain amount of thermal power for additional load regulation. In fact, hydro and solar power in China is abundant in summer and low in winter, and thermal power would be the most reliable and economic way to compensate for this seasonal difference. Meanwhile, the residual heat from thermal power consumption in the winter can be used for northern urban heating.

2.2.3 Methods to Achieve Zero-Carbon Heating There was 15 billion m2 of NUH demand in China in 2019. The ongoing development of urbanization will lead to continuous growth of demand for a better building environment. In the future, the floor space of NUH will reach 20 billion m2 . Currently, the average heat consumption for NUH buildings is more than 0.3 GJ/m2 . It means that 4.2 billion GJ of heat should be provided to accommodate this demand. At this time, 40% of the heat is supported by coal and gas boilers of various types, 50% comes from combined heat and power (CHP) plants, and 10% comes from electric heat pumps based on air, wastewater, underground water, soil and other low-level heat sources. At present, coal-fired and gas-fired boilers emit 1 billion tons of CO2 , and CHP plants and electric heat pumps also emit CO2 . We need to reduce heating-related carbon emissions in the future by a large amount with a priority given to lowering the heating demand. Currently, approximately 3 billion nonenergy efficient buildings were built in the 1980s and 1990s, with heating demands 2–3 times higher than that of energy efficient buildings in the same neighborhood. This is the main reason why the average heat consumption of NUH buildings is 0.3 GJ/m2 , far higher than the standard of energy efficient buildings, which is 0.2 GJ/m2 . Another reason is overheating. There are a number of buildings with a temperature over 25 °C in the winter, which is much higher than the standardized 20 °C. The heat consumption of a 25 °C room is 25% higher than that of a 20 °C room, while the outside temperature is 0 °C. To realize the target of 0.2 GJ/m2 average heat consumption, we need to introduce better regulatory measures and policies to avoid unnecessary heating for the 3 billion m2 buildings. In this way, we could reduce the heating demand of the 20 billion m2 NUH buildings to 4 billion GJ, which is significantly lower than the heating consumption for the existing 14 billion m2 buildings space. Thus, it can be proven that the key to achieving low-carbon heating is to lower

2.2 Indirect Carbon Emission from Electricity and Heat

15

the heating demand through energy efficiency methods and energy saving building operations. For over forty years of reform and opening up, basically all China’s NUH buildings have been equipped with district heating systems. Approximately 80% of the urban buildings in northern China are capable of connecting to the district heating network. China has been the largest country of district heating implementation in the world. However, the question we need to ask ourself is that is it possible to meet the heating demand by fully leveraging the existing network while retrieving the residual heat from the thermal plant and manufacturing process? Nuclear is the key to zero-carbon power generation. At present, there are 50 GW of nuclear plants in the coastal areas of China, generating nearly 400 TWh of power each year. In the future, approximately 100 GW can be situated alongside the coastline running from Lianyungang harbor to Dalian city in northern China. One hundred GW of nuclear power will produce 150 GW of low-grade waste heat. The existing waste heat is now discharged into the sea, which is one of the key reasons why we build nuclear plants close to the coastline. To effectively retrieve such wasted heat, i.e., collecting 1.2 kW of wasted heat for every kW of power, we will create another 360 TWh of power in the winter, which lasts approximately 3000 h, which also equals 1.25 billion GJ of heat. If cross-seasonal heat storage and CHP are implemented for nuclear development, while the wasted heat can be stored during non-winter seasons, then 3.2 billion GJ of heat can be retrieved, meeting 80% of the heating demand for northern regions. Therefore, there is huge potential for further developing nuclear power for zero-carbon heat in China. The approach that can be adopted is desalination of seawater using nuclear waste heat through distillation when prepared with hot freshwater at 95 °C. The most economical distance of transmitting heat and freshwater through a single tube to densely populated areas shall be within 150–200 km. The first station close to the urban area can cool the delivered fresh water to 10–15 °C by means of heat exchange, thus making it the source of fresh water for the city dwellers, while the heat released becomes the source of the central heating system of the city. When the temperature of sea water is 0 °C, and when such an approach is employed, 80% of the waste heat goes to the central heating system, 15% goes into the water supply system or is lost during transmission, and the remaining 5% goes back to the sea when the concentrated brine is discharged. In this way, 1 billion GJ of heat from nuclear waste will be provided in Northern China as a heat source in winter. Meanwhile, it will produce for each winter some 3 billion cubic meters of freshwater, close to the annual volume diverted through the already completed middle route of China’s South to North Water Diversion Project. This will play a significant role in alleviating the water shortage in the northern coastal areas. Because 80% of the residual heat from nuclear waste is reused as the heat source for city dwellers, the approach can be reasonably regarded as a zero-energy-consumption desalination solution because the energy consumed by the transmission pumps is only half of the current dual-pipe circulation systems. As a consequence, the economic transmission distance can be increased from 70 to 100 km to 150 to 200 km. Fresh water, however, takes a free ride on the transmission of heat. Another windfall is the study process of desalination

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2 Carbon Neutrality Pathways for China’s Building Sector

Turbine

Hot freshwater Desalination unit of seawater

Seawater

Large-scale cross-season heat storage

Separation of water and heat

Heat supply

Water supply

Fig. 2.3 Seawater desalination and water-heat co-generation system with cross-season energy storage function

of seawater. As the heat exchange capability required for hot fresh water systems is reduced by approximately 50%, the initial investment in the installations is at least 30% lower than what a conventional desalination system may cost. This means that the initial investment in this approach featuring a synchronous mechanism by which freshwater and heat are generated, transmitted and separated in one set of steps is less than 50% of that of the usual method in which desalination of seawater is done separately from the cogeneration of heat and electricity when utilizing nuclear waste heat. Furthermore, the heat thus consumed when generating the same volume of heat and freshwater is reduced by 30%. If large-scale cross-season heat storage systems near urban areas are to be built, utilizing given natural resources such as lakes or ponds, all the nuclear waste heat hence emitted throughout the year will be effectively used. Figure 2.3 illustrate the system with a cross-season heat storage unit. In seasons when no heating is required, the nuclear waste heat emitted is used to prepare hot freshwater, which, after being transmitted over a long distance, goes into the top of a large thermal energy storage reservoir. The hot freshwater then replaces the cold water (at the temperature of 10– 15 °C), which is then drained from the bottom of the reservoir before being sent to water service companies via pipelines B and C. By the end of the heating season, all the water in the reservoir turns cold. However, in a long course of heat exchange through spring, summer and autumn and when heating is required again in winter, all the water stored in the reservoir will be hot water at 90 °C. From the start of the heating season, hot fresh water prepared from the nuclear power plant continues to enter the top of the reservoir, while more hot water flows from the top through pipeline A into the heat exchanger, releasing heat via the water-heat separator to the circulating water on the other side. Some of the water thus cooled to a temperature of 10–15 °C and then returned to the reservoir through pipeline B when the rest went to the water service company via pipeline C. Since nuclear power plants typically operate between 7500 and 8000 h a year, this year-round operation with cross-season energy storage functions can provide 2.5 times the amount of fresh water and heat that of the traditional approach operating only in winter. Suppose there is a nuclear power plant with a capacity of 100 GW; it can provide 2.5 billion GJ of heat and 7.5 billion tons of fresh water year-round, which suffices the heating needs of all buildings and half of the freshwater needs of all urban areas with a total population of 0.2 billion within 200 km in the shoreline’s normal direction. For inland areas of northern China that are far from the coasts, waste heat can be utilized in a mode of co-generation of heat and electricity using coal-fired power

2.2 Indirect Carbon Emission from Electricity and Heat

17

plants, which are used as peaking plants in winter. A coal-fired power plant with a capacity of 1 kW can produce more than 1.3 kW of heat at the same time. In this way, suppose the total capacity of the peaking plants in northern China is 300 GW, and the total output of heat can be 350 GW. Again, supposing that the average operation hours in the whole winter are 2000 h, then the heat thus generated can be as high as 2.5 billion GJ, 80% of which, the heat requirements of a total of 10 billion square meters of buildings in Northern China, can be sufficiently met. For certain urban buildings that are difficult to connect to a centralized heating system, possibly accounting for 20% of the total urban buildings in the future, various heating sources of electricity-driven heat pumps can be used, including air-source heat pumps, ground-source heat pumps, sewage-source heat pumps, and ground source heat exchanger pumps at depths of 2000–3000 m. If the average COP of these heat pumps is 2.5, then some 90 Twh of electricity is to be consumed to generate 0.8 billion GJ of heat required for 20% of the total urban buildings in Northern China, namely, 4 billion square meters of buildings. This accounts for a mere 3% of China’s total electricity consumption in winter (approximately 3000 TWh), which will not cause too much burden on the winter-summer balancing of electricity consumption of the power systems.

2.3 Carbon Emissions from the Construction of Buildings Energy consumed in China’s manufacturing industry accounts for 65% of the country’s total energy consumption, and industry is the primary source of carbon emissions in China. Eighty percent of all the energy consumed in the entire industry sector goes to iron and steel, nonferrous metals, chemicals, and building materials. Part of the energy consumed in the chemical industry serves as a raw material itself, so no carbon emission ensues. That being so, the Big Three carbon emitters by industry in China are iron and steel, nonferrous metals, and building materials. These three industries in China boast huge production capacities. In 2019, China’s steel production exceeded 1 billion tons, making China the largest steel producer in the world, larger than that of the second to tenth largest countries combined. The production of cement and flat glass in China is even more than 50% of the world’s total production, thus leading to huge carbon emissions. Such production is due to strong domestic market demand. The main driving forces of China’s economic development since the turn of the century have been the construction of towns and cities and large-scale infrastructure projects brought about by rapid urbanization. The total number of urban residential buildings in 2019 was nearly four times that in 2000. The construction of expressways and high-speed railways started from zero 20 years ago, and now, the total mileage of highways and railways in China is number one in the world. Two decades of rapid development in terms of construction and infrastructure has dramatically changed the landscape of China and laid an important foundation for the realization of an even more beautiful China. However, this high speed of construction has led to an extremely strong demand for iron and steel, building materials

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2 Carbon Neutrality Pathways for China’s Building Sector

and nonferrous products. Seventy percent of China’s iron and steel products, 90% of construction material products, and 20% of nonferrous products are used for building and infrastructure construction, of which more than half are used for buildings. The production and transportation of these products lead to huge carbon emissions. The carbon dioxide emissions from the construction of civil buildings as a result of the production, transportation and construction of building materials have reached 1.6 billion tons, close to the carbon dioxide emissions of 2.2 billion tons from the operation of the buildings. The sum of the two amounts to almost 40% of China’s total carbon emissions, making it the sector with the largest share of CO2 emissions in society as a whole, as detailed in this chapter. Although the carbon emissions from the production and transport of these 1.6 billion tons of building materials are counted in the industry sector and transport sector, the responsibility for reducing this portion of carbon emissions should also be taken by the building sector. The reason is that industry and transport sectors would not produce and transport these building materials on such a large scale without a strong demand from the building sector. Should this high speed of housing construction be sustained? At present, China has constructed over 60 billion square meters of urban and rural buildings, with over 10 billion square meters of buildings still under construction. When all buildings under construction are completed, China will have over 70 billion square meters of buildings with a floor area of 50 square meters per capita. Then, urban residential buildings will exceed 35 square meters per capita and that of rural residential buildings will be even higher, while public and commercial buildings will also exceed 10 square meters per capita. In 2019, China’s per capita floor area already exceeded the current levels of Japan, South Korea and Singapore, three developed Asian countries, and was close to the levels of France, Italy and other European countries. The relative scarcity of land resources in China and the pattern of mid- or high-rise apartment buildings jointly leads to a smaller area of residential units than that of single-unit or duplex-type houses in Europe and the United States. According to some surveys and statistical studies, the current vacancy rate of urban housing in China is already over 20%. Considering the 10 billion square meters of buildings that will be completed in just three or four years (more than 60% of which are residential buildings), even with further urbanization and a further 25% increase in urban residents (from the current 800 million to 1 billion), the total housing stock will basically meet the demand of the future. The housing problem in China is simply a matter of housing allocation and no longer a matter of insufficient supply. In the spirit of “housing is for living, not for speculation”, further increases in the scale of housing will only increase the vacancy rate and create more “ghost towns”. The annual completions in the early 2000s were much greater than the annual demolitions, resulting in a net increase in total construction to meet the rigid demand for buildings. In recent years, however, the annual demolition of floor space has reached almost 2 billion m2 , although the annual total area of urban residential and public buildings completed has remained between 3 and 4 billion m2 in those urban areas. It also shows that the construction of houses in China has shifted from increasing the supply of houses to meet immediate needs to demolishing old ones

2.3 Carbon Emissions from the Construction of Buildings

19

and building new ones to improve building performance and functionality. The “Mass-Demolition-for-Mass-Construction” pattern has become the main mode of the construction industry. However, according to statistics, the average lifetime of a demolished building is just over 30 years, far shorter than the lifetime designed for the building. The main objective of the “Mass-Demolition-for-Mass-Construction” pattern is to improve the performance and functionality of buildings and to optimize land use. The big driving force behind this is the soaring land price. However, if such a demolition spree continues, it will make the construction of houses an ongoing industry rather than a periodical phenomenon. The resulting strong demand for iron and steel and building materials will then continue, as will their production. Carbon emissions thus caused and maintained will be difficult to reduce. Compared to such a mass demolition for mass construction patterns, the repair and renovation of buildings can also meet the need for functional upgrading, but a large amount of steel and cement will not be required if the main body of the structure is not involved, resulting in far less carbon emissions. Changing the mode from mass demolition for mass construction to repair and renovation can significantly reduce the consumption of building materials and thus also reduce the carbon emissions from the production of building materials. The construction industry should undergo a transformation, from building new houses to repairing old ones. Such a transformation will greatly reduce the heavy demand for building materials such as iron and steel and cement for housing construction, thereby reducing the production of such industries and transforming them accordingly. However, why do we prefer tearing down and rebuilding to repair and renovate? Surveys have shown that although demolition and reconstruction require a large amount of construction materials, the labor costs are much lower than those for repair and renovation. Moreover, demolition and reconstruction can also increase the floor space on the original land, thus bringing huge commercial benefits. Therefore, it is important to develop a scientific and reasonable policy mechanism from the perspective of ecological civilization to put an end to the phenomenon of massdemolition-for-mass-construction and to encourage a labor-intensive rather than a material- and carbon-intensive mode of housing renovation. Whether new construction or reconstruction occurs, the construction industry is still heavily dependent on cement. The cement production process emits large amounts of CO2 . A definitive solution to this problem requires a radical change in the way houses are currently built and in the form of building materials. Cement had never been used in China’s 5000-year-long history of house construction before the industrial revolution, when traditional craftsmanship was used for the construction of the Great Wall, giant palaces, and other magnificent time-testing buildings. Cement as a building material came to the fore only in the past 200 years and is now the basis of the current method of construction. Low-carbon development is likely to require a revolution in the construction industry, and the fundamental starting point is to replace high carbon emitting cement with new low-carbon or zero-carbon building materials and to develop new building structures and housing construction methods according to the characteristics of the new building materials.

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2 Carbon Neutrality Pathways for China’s Building Sector

It is difficult for future energy systems to completely avoid the use of fossil energy. Using small amounts of fossil energy through combustion and separating carbon dioxide from flue gas emitted during combustion before solidifying and storing it, known as carbon capture and storage (CCS), will be an important way to achieve carbon neutrality. However, storing solidified or liquefied carbon dioxide is the most difficult problem in CCS. If, in some way, carbon dioxide is synthesized into new building materials, to make the building structure a storage space for carbon, it will not only address the problem of carbon dioxide emissions from the production of building materials but also make the building a carrier of carbon. This will make a significant contribution to achieving carbon neutrality in the future. The above discussion shows that the current construction boom in China is the main reason for the high production of iron, steel and other building materials, which in turn accounts for a major part of the total carbon emissions from industrial production processes. Avoiding the previous pattern of “Mass-Demolition-for-MassConstruction” and making building maintenance and renovation the main tasks of the construction industry, thus reducing the demand for iron, steel and building materials, will effectively reduce carbon emissions from industrial production processes. Research into new low-carbon building materials and low-carbon structural systems and construction methods is an important task for the construction industry to realize a low-carbon future. Using carbon dioxide separated from flue gas to produce new building materials, thus making buildings a carrier for carbon sequestration, could further transform the construction industry from its current high-carbon status to a carbon-negative status, contributing to the target of carbon neutrality.

2.4 Non-CO2 Greenhouse Gas Emissions In addition to the global warming caused by carbon dioxide, there are many other noncarbon dioxide gases that contribute to global warming when they are emitted into the atmosphere. The ratio of the greenhouse effect of one carbon atom from any of these gases to that of one carbon atom from CO2 is known as the global warming potential (GWP), and the GWP of these non-CO2 greenhouse gases (non-CO2 gases for short) can be as high as dozens to thousands. Thus, although the emissions of these gases are far less than those of carbon dioxide, their impact on climate change should not be underestimated. According to some preliminary analysis by a relevant institution, the non-CO2 gases emitted in China, by means of GWP, are equivalent to 20–30% of the carbon dioxide emitted from the use of fossil energy. Among them, hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), and other refrigerants that are commonly used in buildings for air conditioning and refrigeration are the main non-CO2 gases. Table 2.1 illustrates the GWP values for several refrigerants currently used. Refrigerants such as hydrofluorocarbons and hydrochlorofluorocarbons will not cause any greenhouse effect until they are emitted into the atmosphere. If, by

2.4 Non-CO2 Greenhouse Gas Emissions

21

Table 2.1 GWP values for several common refrigerants Type

Name

GWP values by Montreal protocol

HFCs (hydrofluorocarbons)

HFC-134a

1430

HFC-227ea

3220

HFC (hydrofluorocarbon mixtures)

R-404A

3922

R-410A

2088

HCFC-22

1810

HCFCs (hydrochlorofluorocarbons)

HCFC-141b

725

improving the sealing process, a leak-free air conditioning and refrigeration operation is achieved, zero emissions during such operations can be achieved accordingly. The technology level of refrigeration and air conditioning in China has seen great improvement in recent years, with significant reductions in the leakage rate during the operation of air conditioners, refrigerators and other types of refrigeration systems that use fluorine-based refrigerants. As long as the sealing process continues to be improved and strictly controlled, the elimination of leaks during the operation of nonmobile equipment is entirely achievable. For vehicle air conditioning systems, it would be difficult to give a 100% guarantee against any leakage because vehicles are subject to long-run and violent vibrations. Therefore, new types of Fgas-free air conditioning technologies should be developed. A significant amount of refrigerant emissions occurs during repair and demolition processes. In particular, decentralized air conditioning systems in residential buildings, when removed or abandoned, are often emptied with refrigerants discharged directly into the atmosphere. It also happens in the maintenance of chillers in central air conditioning and various types of medium- and large-scale heat pumps. A strict system of recovery of refrigerants through a rational policy mechanism to ban such emissions in various settings can effectively eliminate emission of non-CO2 gases. In recent years, a number of organizations have developed technologies to recover and reuse refrigerants removed from previous systems. Reuse technologies are rather difficult to develop and cost more, which in many cases result in the abandonment of recycling of these refrigerants. The results would be different if the starting point of policy design is to be changed. If we see it not from the angle of recycling but from how to avoid emissions, learning from what has been done with air and water pollution management, the measures and policies will be different. When the recovered refrigerants are difficult to deal with or reuse, they can be converted into CO2 through burning before being released, thus reducing the GWP to 1. Learning from successful experiences and approaches in the field of environmental governance to develop effective management methods for refrigerants can avoid non-CO2 emissions from such refrigerants. A further path would be to develop new Fgas-free refrigeration technologies, which would completely avoid the use of nonfluorinated refrigerants in certain situations where leakage cannot be avoided or is difficult to manage. A great deal of new technologies is currently available to enable refrigeration without gases. By

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2 Carbon Neutrality Pathways for China’s Building Sector

using indirect evaporation cooling technology in dry areas, cold water below the wet bulb temperature can be obtained to meet the needs for comfortable air conditioning and data center cooling, while power consumption by such cooling is significantly reduced. By taking advantage of low-grade heat emitted at approximately 100 °C and by means of absorption cooling, the cooling sources required for comfortable air conditioning and industrial air conditioning can be similarly obtained. As such cooling sources use nuclear waste heat, they save energy. New refrigeration technologies, such as thermoacoustic refrigeration, magnetic refrigeration, and semiconductor refrigeration, involve no refrigerants at all. Previously, these new refrigeration methods were considered to have small capacity and low energy efficiency and served only under special demands. In recent years, however, these methods have seen major theoretical and technical breakthroughs, with increased refrigeration capacity and efficiency, and are gradually penetrating into the building sector. The use of fluorine-free refrigerants is another technological pathway to address non-CO2 emissions. Carbon dioxide itself is a refrigerant. Since the three-phase critical temperature of CO2 is 31.2 °C, the working condition of the heat pump required to release heat is a variable temperature rather than a phase transition temperature as for other types of refrigerants, which makes it possible to match heat exchange between the refrigerants and the thermal transfer media, thus increasing the efficiency of the heat pump. Over the last two decades, heat pumps using carbon dioxide as a refrigerant have enjoyed great success. Due to the high working pressure of carbon dioxide, the required pressure-bearing capacity of compressors and systems is very high, and China still needs to make more efforts to improve its manufacturing technology in this regard. It is therefore a critical task to address non-CO2 gas emissions. Cooperation across industrial borders should be encouraged to tackle the key issues and to develop our own packages of technology and products as soon as possible. Another important direction that requires attention is ammonia refrigerants. This is the refrigerant that was used when man first adopted compression refrigeration. Later, due to safety issues, it gradually phased out. In considering alternatives to fluorine-based refrigerants, ammonia returns to the forefront of history. Through a number of innovative technologies, it is possible to overcome some of the original problems of ammonia systems, and it is likely that ammonia will gain a certain market share in the field of refrigeration, freezing, and air conditioning in the future. The issue of non-CO2 gases is as important as CO2 in affecting climate change and needs to be taken seriously by the building sector. A solution to the problem of non-CO2 greenhouse gas emissions, when made available, will lead to revolutionary changes in refrigeration, freezing, and air conditioning in buildings and will certainly bring about innovative breakthroughs in technology, which deserve the attention of the industry.

2.5 Eco-civilization Concept Should Be the Foundation

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2.5 Eco-civilization Concept Should Be the Foundation Thus far, we have discussed from a technological perspective how to achieve carbon neutrality and the pathway that the building sector may take to that end. However, achieving the ultimate goal of carbon neutrality along this path requires not only a technological revolution but also a concept of development focusing on ecocivilization in the fundamental issue of the relationship between buildings and occupants. The basic concept of creating the environment inside buildings should take into account the relationship between man and nature and the concept of sustainable development. The essence of industrial civilization, which began to take shape with the Industrial Revolution, is to exploit all the resources of nature to satisfy human needs. The concept of industrial civilization has promoted the great development of human society. However, human beings are known to be endlessly voracious, and their unending demands will never be sufficiently met in the face of limited natural resources. That is the undoing of everything, from resource depletion, environmental degradation to global warming over the years. The development concept of ecological civilization, on the other hand, is to pursue a balance between human development and the ecological environment and to achieve sustainable human development without changing the natural ecological environment. From this basic idea, many of the abovementioned controversial questions can be answered: How many more buildings should be built in the future? Are they to meet the basic needs of living and that of social, cultural and economic activities, or just to satisfy those luxury obsessions? Many debates have arisen over the years about the stock of residential units, offices, schools, and buildings and facilities for commercial, transport, cultural and sports purposes. It is difficult to set an upper limit on scale when we look at residents’ health, wellbeing, and social prosperity and, of course, capital operations. However, considering the constraints of natural resources such as land resources and carbon emission space, there is indeed an upper limit that constrains the unlimited expansion of building scale. Capping the total number of buildings, rationally planning the scale of various types of buildings under the total number determined, and avoiding expansion are the basic principles and requirements of the concept of development focusing on ecological civilization and are even more the basis for achieving carbon neutrality in the future. In what way should the indoor environment of buildings be created? It is another fundamental question of how to achieve the development of ecological civilization. The per capita energy consumption of urban buildings in our country is currently approximately one quarter to one fifth of that of the United States. The operating energy consumption per unit area is only approximately 40% of that of the United States. The large difference is due to the different concepts of the indoor environment. Traditionally, Chinese people tend to use buildings in a “part time part space” mode. This means that lighting, air conditioning and other energy-using devices are switched on only in occupied rooms. All energy-using devices are switched off when no one is around. This differs from Americans’ “Full time, full space’ mode, where

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2 Carbon Neutrality Pathways for China’s Building Sector

the indoor environment keeps operating 24 h a day as required, whether occupied or unoccupied. This is undoubtedly convenient for occupants, but as the actual use of each building space is only 10–60%, an all-day-long indoor environment creates a huge energy demand, making it extremely difficult to achieve zero carbon for building operations. In addition, the way in which the building is ventilated will result in a huge difference in the energy demand for building operation. Is it entirely mechanically ventilated or natural ventilation preferred wherever possible? Are the indoor temperature and humidity maintained at the lower level of comfort (lower temperature limit in winter and upper temperature limit in summer) or at the upper level (upper temperature limit in winter and lower temperature limit in summer)? Is it over-cooled or over-heated? Bearing in mind the concept of ecological civilization and adhering to China’s traditional economy-saving building operation model, we can achieve the goal of zero carbon in building operations at a low level of energy intensity. Once this traditional mode of operation is broken down and the energy intensity of building operation increases by three or more times from the current level as a consequence, the ideas proposed above on achieving zero-carbon goals will fail. Likewise, as discussed above, a “demand-side response” mode of operation for building equipment would also require appropriate adjustments to indoor electricity consumption in response to changes in renewable power on the supply side without affecting the basic needs of the occupants. This would to some extent affect the comfort of the occupants and the convenience of the services they receive. However, that would be a small price to pay to avoid the use of fossil energy and thus achieve zero carbon. That’s the balance we have to make between zero carbon and high building service level. In fact, as the concept of zero carbon has taken hold, developed countries have begun to rethink and advocate an energy-saving and low-carbon operation mode. Starting from the concept of ecological civilization and moving from the pursuit of ultimate enjoyment to the pursuit of a balance between human needs and the natural environment is a manifestation of the development and progress of human civilization and should be a development philosophy that we must adhere to.

2.6 The Pathway to Zero-Carbon China currently emits more than 2 billion tons of carbon dioxide annually in building operations, in addition to 1.6–1.8 billion tons from the construction sector indirectly generated via manufacturing areas such as iron and steel and other building materials. The goal of achieving carbon neutrality by 2060 is only 40 years away. What pathway should the building sector take in these 40 years to achieve its future goals? By clearly defining the goals for the forthcoming 40 years, the development path can be scientifically planned so that we can gradually approach the target while meeting the needs of achieving socioeconomic and cultural development. There was no need to resort to the old means of “crossing the river by feeling the stones”. We should avoid redundant projects and avoid twists and turns.

2.6 The Pathway to Zero-Carbon

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Faced with these challenges, there can be a variety of solutions. Some of them are intermediate processes leading to future carbon neutral scenarios, and some even run counter to that end. Should it then be the case that only those solutions that are consistent with future goals should be chosen as far as possible? For example, the current move to eliminate dispersed coal and to achieve heating with clean energy in the northern regions could either be a “coal to gas” approach or a “coal to electricity” approach. “ Shifting from coal to natural gas” solution can indeed eliminate the use of dispersed coal and achieve the goal of clean heating. However, from what we have discussed above, it is now clear that natural gas is also a fossil energy source, and the CO2 emissions from burning natural gas are approximately half of those from burning coal to produce the same amount of heat, so it naturally will be replaced in the future. Therefore, should we adhere to the “coal-to-electricity” approach, particularly “coal to heat pumps”, rather than gas first before shifting from “gas to electricity”? Since 2000, the world has been witnessing rounds of gas-powered trigeneration systems, also known as combined cooling, heat & power (CCHP), which serve as the main form of distributed energy to improve energy efficiency and to achieve the low carbon goal. However, this is still driven by natural gas, a fossil energy source, and inevitably emits CO2 . Since they are trigeneration systems, the highest efficiency is achieved only when the demand for heat and power or cooling and power are matched. For a building or a building community, it is difficult to match the demand for electricity with the demand for heat and cooling simultaneously. If the building is operating in a mode of “heat determined by power demand”, then a large amount of heat will be discharged when there is no heat demand; and when the “power determined by heat demand” mode is on, wind power and photoelectricity may fall prey to gas-fired power, thereby interfering with the future plan where wind power and photoelectricity should dominate the power systems. The larger problem with such trigeneration systems is a less desirable cooling mode. In fact, characteristically, the demand for cooling in buildings is in most cases expected to be a “part time part space” mode. Trigeneration systems, however, provide “full time, full space” cooling services, leading to an exponential increase in energy consumption at the customers’ end. Over the past 20 years, many CCHP systems have been built in China, but in actual operation, there has not been a single case of a real reduction in operational energy consumption and energy savings. Do we need to learn from such lessons and resolutely stop similar projects to achieve the goals of carbon neutrality? The development of photovoltaic power generation on building surfaces is a future trend. The cost of PV modules is now decreasing, and the cost of PV power is already lower than that of coal power. The development of PV systems does not have any negative impact on buildings, so why not use it in new buildings as soon as possible and add it to existing buildings? The main difficulty facing photovoltaic power generation is access and consumption. When buildings have yet to go through PEDF (Photovoltaic, Energy storage, Direct current and Flexibility) transformation, which will provide good access and consumption conditions for PV power, and when the power grid has not been profoundly transformed to create conditions for distributed access for renewable power, large-scale photovoltaic generation may have

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some adverse impact on the power grid. Thus, it may be a good choice to build PV and DC charging piles in car parks around buildings and have electric vehicles consume PV power by smart slow charging. This may serve as an important action in the path towards carbon neutrality of buildings, as it facilitates the promotion of electric vehicles and is in line with PEDF transformation in the future. This is a way of development that combines the long-term direction with immediate tasks. Adhering to the direction of green buildings and enhancing the functionality and service level of buildings through green technologies is the direction of development in China’s building sector. In design and construction, the building’s demand for cooling, heating and lighting provided by mechanical systems should be minimized through passive technology, and then its energy supply efficiency should be maximized through optimization of energy supply systems. This should remain the basic requirement for the future development of buildings and electromechanical systems. On this basis, together with the development of technologies and measures regarding energy storage and flexible energy consumption, we will be steadily marching towards the goal of carbon neutrality. In this chapter, we have introduced the objectives of climate change mitigation and carbon neutrality, as well as the four main tasks for the building sector: eliminating direct carbon emissions, reducing indirect carbon emissions from the use of electricity and heating, reducing carbon emissions from the production and transport of building materials for the construction and maintenance of buildings, and avoiding non-CO2 GHG emissions from the use of air-conditioning and refrigeration systems in buildings. The concept of ecological civilization is the basis for accomplishing these four tasks. To achieve carbon neutrality, revolutionary changes must be implemented in all four areas regarding types of energy, ways to use energy, building materials and structures, and cooling methods of air conditioning. Only through these fundamental changes will it be possible to eliminate or neutralize building-related GHGs. These revolutionary changes, in turn, are driving technological forces across the board. Thus, carbon reduction and carbon neutrality do not constrain economic development; rather, they break the deadlock in technological and economic development, opening up new frontiers that can feed disruptive technologies and facilitate leapfrogging across the industry. Seizing this opportunity for development brought about by these tasks and looking at the development of the industry from a new perspective will enable us to see many issues more clearly and thus develop completely different solutions to promote revolutionary changes.

Chapter 3

China’s Building Energy Use and GHG Emissions

3.1 Basic Situation of China’s Building Sector 3.1.1 Urban and Rural Demographic In recent years, urbanization has grown rapidly in China. In 2019, 848 million people lived in urban areas, while 654 million people lived in rural areas. The urbanization rate grew from 37.7% in 2001 to 60.6%, as shown in Fig. 3.1. Urbanization is fundamentally characterized by the massive migration of people from rural areas to cities. In China, urbanization means that people, for the most part, migrate to superlarge cities and county-level cities. According to Li Xiaojiang, former director of China Academy of Urban Planning & Design, from 2000 to 2010, 41% of urban population growth was contributed by megacities, superlarge cities and large cities, and 37% came from counties and towns.1 In recent years, overpopulated large cities with excessive entry limits have significantly dampened the speed of populated growth in cities. For instance, barring a slight decrease in Beijing, the number of permanent residents in Beijing and Shanghai has remained basically unchanged since 2016.2 On the other hand, rural residents migrate to counties and small towns, which is another characteristic of urbanization in China. Currently, approximately onefourth of the Chinese people live in small towns. Until 2016, there were 1483 counties, with 155 million people in the built-up areas. There were 20,883 designated towns with a total population of 195 million. Since 2001, the residential building stock in designated towns has doubled, from 2.86 billion square meters to 5.39 billion square meters.3 China will continue to support the development of 1

The Characteristics of Urbanization and the Formation of Urban System, LI Xiaojiang, ZHENG Degao. 2 National Bureau of Statistics of China, China Statistic Yearbook, 2019 and 2020. 3 Source Ministry of Housing and Urban–Rural Development of the PRC, China Urban and rural Construction Statistical Yearbook, 2006–2017. © China Architecture Publishing & Media Co., Ltd. 2022 S. Hu et al., China Building Energy Use and Carbon Emission Yearbook 2021, https://doi.org/10.1007/978-981-16-7578-2_3

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3 China’s Building Energy Use and GHG Emissions

Fig. 3.1 Population growth in China (2001–2019)

small towns during the new urbanization process. Currently, the design and planning, management and operation of small town infrastructures and energy systems are still relatively backward, which are the result of the limited scale of the economy and development. To keep the balance of the urbanization process and usher in continuous growth, we need to take the role of small towns seriously while pursuing urbanization and strengthening the planning and building of small towns.

3.1.2 Building Stock Rapid urbanization sustains construction sector development, and the scale of China’s construction sector is expanding. From 2007 to 2009, thanks to the rapid growth of building construction in China, the floor space greatly expanded in urban and rural areas. Specifically, from 2007 to 2014, the newly built building stock for civil buildings grew steadily from 2 billion m2 per annum to more than 4 billion m2 , among which urban residential and public and commercial (P&C) buildings accounted for 3.6 billion m2 (Fig. 3.2). Driven by the large number of construction projects, the demolished building stock of urban residential areas and P&C buildings increased rapidly from 700 million m2 in 2007 to a stable level of approximately 1.7 billion m2 . In 2019, the newly built building stock of civil buildings in China was 4.1 billion m2 , 80% for residential buildings, and 20% for nonresidential buildings. P&C buildings can be categorized into offices, hotels, shopping malls, hospitals, schools and others, and the share of newly built building stock for each category remained basically unchanged from 2001 to 2019. Shopping malls, offices and schools accounted for 75% of the total completed areas, 32, 24 and 18%, respectively, and hospitals and hotels accounted for only 5 and 3%, respectively (Fig. 3.3). Large-scale building construction activity has led to the rapid growth of China’s building stock. China’s total building stock was approximately 64.4 billion m2 in

3.1 Basic Situation of China’s Building Sector

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Fig. 3.2 Newly built and demolished building stock of civil buildings in China. Source The newly built building stock data of this report are based on the China Statistical Yearbook on Construction. Demolished building stock is estimated by the model, with data from the China Statistical Yearbook on Construction, 2018 Report of China Construction and Demolition Waste Disposal Industry, 2019 Outline on China Construction and Demolition Waste Recycle and Disposal Industry, and Annual Report on Comprehensive Utilization of Resources in China (2014)

Fig. 3.3 Newly built building stock of P&C buildings according to different functions (2001, 2019)

2019, in which urban residential areas accounted for 28.2 billion m2 , rural residential areas accounted for 22.8 billion m2 , and P&C buildings accounted for 13.4 billion m2 . (Fig. 3.4). The floor area for northern urban heating stood at 15.1 billion m2 . The difference in the per capita building stock of residential buildings between China and developed counties is decreasing. However, the per capita building stock of P&C buildings in China remains low, as shown in Fig. 3.5. In China, the per capita building stock of office buildings is relatively reasonable, with a low volume of per capita shopping malls, hospitals and school building stock. The rapid growth of ecommerce dampens shopping mall expansion, but there is potential for increasing the stock of hospitals, schools and other public utility buildings. Therefore, public utility buildings could be the main contributor to the next round of China’s P&C building

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3 China’s Building Energy Use and GHG Emissions

Fig. 3.4 China’s existing building stock (2001–2019)

construction. Additionally, transportation hubs, recreational and athletic buildings and other community-centered buildings could be the mainstay for P&C building construction.

Fig. 3.5 Per capita building stock in China and other countries. Source IEA Buildings Summary, World Bank WDI database, Odyssee Mure database(2018), ERI database, US, NRCA, Canada, Energy Use Data Handbook Tables (2017), Database of Ministry of Land, Infrastructure, Transport and Tourism, Japan, Summary of architectural statistics for 2018, South Korea, Satish Kumar (2019), India

3.2 Global Energy Use and gGHG Emissions in the Building Sector

31

3.2 Global Energy Use and gGHG Emissions in the Building Sector The energy use and emission of the building sector occurs during building construction, operation, demolition, etc. However, the majority of energy use and GHG emissions take place during building construction and operation, which are the focus of this report (see Fig. 3.6). There are two types of building-related energy use: building embodied energy from building materials during construction and energy consumed during building operation. The first refers to the energy consumption of building material exploration, production, transportation and on-site construction. According to general statistical standards, the construction sector contains civil building construction, production building (non-civil building) construction and infrastructure construction. Based on BERC statistics, this report demonstrates the embodied energy/emissions of the construction sector as well as the embodied energy/emissions of civil buildings (see Sects 3.3.1 and 3.4.1). Energy consumed during the operation phase refers to heating, ventilation, air conditioning, cooking, domestic hot water (DHW) and other energy use activities in residential buildings, offices, schools, shopping malls, transportation hubs, recreational buildings, etc. While studying building operation energy use, many international research institutions have divided it into energy use for residential and nonresidential buildings. However, it did not reflect the true features of China’s situation. Thanks to our long-term research on building energy use in China, this report will analyze China’s building energy use in the following four aspects, namely, urban

Construction phase

Building sector

Embodied energy from building materials

Direct emission from building material production

Construction

Indirect emission from energy use

Urban residential

Direct emission from energy use

Rural residential

Operation phase

Public building Northern urban heating

Indirect emission from energy use

NON-CO2 GHG emission

Fig. 3.6 Types and boundaries of energy use and greenhouse gas (GHG) emissions in the building sector

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Fig. 3.7 Global terminal energy use and CO2 emissions in the building sector (2019). Source International Energy Agency, 2019 Global status report for buildings and construction. The construction sector includes civil buildings, production buildings and infrastructure construction

residential building energy use, rural residential building energy use, P&C building energy use and northern urban heating (NUH) energy use; see Sect. 2.3 for more information. Based on different emission sources, GHG emissions in the building sector can be divided into four categories: direct carbon emissions during operation, indirect carbon emissions during operation, embodied carbon emissions of building construction and maintenance, and non-CO2 GHG emissions during operation; see Chap. 1 for more definitions, existing situations and emission reduction methods. According to the International Energy Agency’s (IEA) calculation of global energy use and emissions of the building sector (see Fig. 3.7), in 2019, terminal energy use4 during the global building construction stage (including building and infrastructure construction) and building operation accounted for 35% of the total global energy consumption, in which the terminal energy use of construction accounted for 5% and the energy consumed during the operation stage accounted for 30%. In 2018, global CO2 emissions during the building construction stage (including building and infrastructure construction) accounted for 10% of the total, and 28% of the global CO2 emissions came from building operation. According to BERC’s calculation of China’s building energy use and emissions, in 2019 (Fig. 3.8), China’s embodied energy use and operational energy use in the building sector5 accounted for 33% of the total social energy use, close to the global level. However, the building embodied energy use was 11%, higher than 5% of the global level. Building operational energy use accounted for 22%, lower than the global average. The share of China’s building sector energy use will continue to grow with the development of economic and living standards. On the other hand, the

4

Terminal energy use refers to the aggregation of heating, electricity and other energy use in the building sector. The calculation of energy use of building operation and building construction using terminal energy use method, smaller on the number compared with primary energy consumption method. 5 Heating and electricity were converted to primary energy use and then combined with other terminal energy use case.

3.2 Global Energy Use and gGHG Emissions in the Building Sector

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Fig. 3.8 China’s building energy use and CO2 emissions (2019). Source Building Energy Research Centre, Tsinghua University. The construction sector refers to civil buildings, production buildings and infrastructure construction

CO2 emissions of building construction and building operation were 38% of China’s total, 16% for building construction and 22% for building operation. As China’s urbanization is still ongoing, the major share of energy use and emission has come from building and infrastructure construction. The share of energy use from building construction is higher than that of the global average and higher than that of other OECD countries, which have already completed the urbanization process. However, compared with other OECD countries, China’s building operation energy use and related emissions are at a lower level. As urbanization becomes slower in China, energy use and related emissions of building operation will take a larger proportion. Figure 3.9 illustrate the comparison of energy use per capita and energy use per square meter of building operation in different countries. The different power structures among countries means that we cannot simply combine electricity and fossil fuel altogether. As shown in Fig. 3.9, the electricity and fossil fuel consumption of buildings are demonstrated on the horizontal and vertical axes, respectively. The size of the bubbles represents the total primary energy use of building operation in that specific country. The bubble chart demonstrates that the total energy use of building operation in China was closing up with the US, but the energy intensity remained at a low level. The energy use per capita and per floor area in China were far lower than those in the US, Canada, Europe, Japan and South Korea. China’s per capita electricity consumption was one-sixth that of the US and Canada and one-third that of France and Japan. China’s per capita fossil fuel consumption was one-third of that of the US and Canada, half of the level in France and Japan. Our per floor area energy use in the building sector was merely one-third that of the US and Canada. As shown in the figure, the closer the bubble is to the horizontal axis, the larger the ratio of electricity among total building energy use, which means more advanced electrification adoption. China’s electrification development was still lagging behind that of countries such as the US and France. China’s low carbon emission and energy efficiency targets in the building sector demand avoiding the copy of developed countries, and we should embark on a different path of development. This would

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Fig. 3.9 Comparison of building operational energy use between China and the world. Source IEA World Energy Statistics and Balances, IEA Buildings Summary, World Bank WDI database, Odyssey Mure database (2018), ERI database, US, NRCAN, Canada, Energy Use Data Handbook Tables (2017), database from the Ministry of Land, Infrastructure, Transport and Tourism, Japan, Summary of architectural statistics for 2018, South Korea, Satish Kumar (2019), India. The electricity consumption of different countries was converted to primary energy use based on the coal consumption of generating stations of different countries

pose a significant challenge to China’s low carbon and sustainable development in the building sector. Meanwhile, there are many developing countries that were transforming their building energy use, and China could be their reference point for future building energy use development. By comparing per capita carbon emissions and per floor area carbon emissions of buildings of different countries (as shown in Fig. 3.10), it could be found that due

Fig. 3.10 Comparison of carbon emissions from building operations between China and the world (2018). Source Result from 2018 IEA CO2 emissions from fuel combustion database, and 2019 BERC model-based estimation

3.2 Global Energy Use and gGHG Emissions in the Building Sector

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Fig. 3.11 Comparison of per capita carbon emissions of different countries (2018). Source Results of the 2018 IEA, CO2 emissions from the Fuel Combustion 2019 Highlights 2019 database, and 2019 BERC model-based estimation

to the low level of operational energy use, the carbon emission intensity of building operation in China was lower than most of the counties in the world. However, the carbon intensity of France is lower than that of China because low carbon electricity accounted for a large share of France’s building electricity use. Per capita carbon emissions and total carbon emissions in the building sector of different countries can be found in Fig. 3.11. China’s per capita carbon emissions were clearly higher than the global average, and per capita carbon emissions in the building sector were slightly higher than the global average, significantly higher than those of Indonesia, India, etc., and much lower than those of most developed countries. In recent years, China has been facing increasing pressure from climate change, which calls for the building sector to realize low carbon development and reach a carbon peak as soon as possible. It would remain a huge challenge for the building sector to meet the target. Please turn to chapter one for more information on how to reach carbon neutrality for China’s building sector.

3.3 Energy Consumption of China’s Building Sector 3.3.1 Embodied Energy of Building Sector As urbanization continues, the energy consumption of civil building construction in China also increases. A large quantity of building materials is needed, the production process of which requires a great deal of energy and carbon emissions. This is one of the key reasons for the continuing growth of energy consumption and carbon emissions in China.

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Fig. 3.12 Embodied energy use of China’s civil buildings (2004–2019). Source BERC Tsinghua University. Only for civil buildings

According to the estimation from the Building Energy Research Centre (BERC) of Tsinghua, embodied energy use amounted to 0.54 gigatonnes of coal equivalent (Gtce) for China’s civil buildings in 2019, 11% of China’s total energy consumption. The embodied energy use of civil buildings in China grew from 0.24 Gtce in 2004 to 0.54 Gtce in 2019, as shown in Fig. 3.12. Due to the slow decrease in the newly built building stock of civil buildings in recent years, its embodied energy use has also dropped gradually since 2016. In 2019, the embodied energy use of urban residential, rural residential and P&C buildings accounted for 69, 7 and 23%, respectively. In fact, the construction sector consists of not only civil buildings but also buildings for production purposes and infrastructures such as motorways, railways, and dams. The embodied energy us of the construction sector mainly includes all types of energy use related to the construction of buildings and infrastructures. According to the calculation of BERC, the total embodied energy use of China’s construction sector in 2019 was 1.4 Gtce, 29% of the primary energy consumption of the whole society, as shown in Fig.3.13. Embodied energy from building materials is the mainstay of the total embodied energy use of buildings, in which iron and steel and cement production consume more than 80%. Rapid urbanization in China has been driving the demand for energy consumption, and it has also resulted in a heavy industry-dominated industrial structure. This was also the key reason for the high per value added energy consumption of China’s industry sector. In 2017, the per value added energy consumption of the manufacturing sector in China was 6.4 tce/ten thousand yuan (2010 USD constant), but it was lower than the 2 tce/ten thousand yuan (2010 USD constant) in France, Germany, Japan and the UK. For the US and South Korea, it was 3.1 tce and 4.5 tce (2010 USD constant), respectively, which were still lower than that of China (Fig. 3.14). As demonstrated in Fig. 3.15, the energy consumed by the iron and steel, noferrous and building material sectors in 2017 accounted for 54% of the total energy

3.3 Energy Consumption of China’s Building Sector

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Fig. 3.13 Embodied energy consumption of China’s construction sector (2014 ~ 2019). Source Calculation from BERC, Tsinghua University. Construction sector, including civil building, production building and infrastructure construction

Fig. 3.14 Total energy use and per value added energy use of the manufacturing sector in

consumption of the manufacturing sector in China. It was 38% in Japan, approximately 27% in France, Germany and South Korea, which was only half of China’s level. It was 18 and 11% in the UK and the US, respectively. According to Fig. 3.16, the per value added energy use of the iron and steel, nonferrous and building material industries was far higher than that of the electronic and mechanical device manufacturing sector (inclu. general apparatus, professional equipment, automobile, computer and communication manufacturing, etc.), and higher than light industry and food industry. Large-scale constructions have been the key foundation for China’s industry structure today. In 2017, 850 million tons of iron and steel and 2.13 billion tons of cement, or 82 and 91% of the total consumption of these two materials in that

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Fig. 3.15 Energy use structure of the manufacturing industry in China and selected developed countries6

Fig. 3.16 Per value added energy use of selected subindustries of the manufacturing industry7

year, were consumed by China’s construction sector, which led to massive energy consumption of building material production. There was 1.2 Gtce of industrial energy used for producing building material in 2018. Between 2013 and 2018, building materials accounted for approximately 40% of the total industrial energy consumption (Fig. 3.17). The fast pace of urbanization in China drove the demand for building materials, which was the key reason why the higher percentage of total energy consumption was represented by iron and steel, building materials and other traditional heavy industries. As urbanization and infrastructure development have achieved initial progress in China, the transformation of the construction mode is ongoing. In 2019, the per capita floor area for urban residential buildings was 33 µm in China, which was close to 6

The data came from IEA world energy balance database, and was converted based on the scale of China’s energy balance. 7 Source National Bureau of Statistics, China Statistic Yearbook 2018.

3.3 Energy Consumption of China’s Building Sector

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Fig. 3.17 Energy consumption for building material production8

that of some developed countries in Asia, such as Japan and South Korea, but still far lower than that of the US. The reason was that during China’s urbanization, the main type of building in the urban communities was apartments instead of single houses, such as that of the US. The utilization ratio of P&C buildings was high in China because of the high-density large city mode of development. In the future, there will be no more rapid growth of iron and steel, building materials and other high energy consumption industries, so long as there is less demolition and the building life cycle can be properly maintained. Therefore, for the next round of urbanization, the demolition of buildings that have not reached the end of life shall be abolished. Technologies to extend the building life cycle shall be invented. Buildings and infrastructures should be properly repaired, and the building life cycle should be extended to facilitate industry transformation and total energy control.

3.3.2 Energy Use During Building Operation This report focuses on the energy consumed during civil building operation, including residential buildings, office buildings, schools, shopping malls, hotels, transportation hubs, recreational facilities and other nonindustrial buildings. Based on our longterm research on the energy consumption of civil building operation, considering the difference in the heating method in the winter, the difference in lifestyle and types of buildings of urban and rural areas and the difference in activities and devices that consume energy in Northern China and Southern China, building energy use could be divided into four categories: northern urban heating (NUH), public and P&C buildings (excluding NUH), urban residential buildings (excluding NUH) and rural residential buildings. More details can be found as follows. 8

In this report, building materials mainly consider steel, cement, aluminum, glass and architectural ceramics.

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3 China’s Building Energy Use and GHG Emissions

1.

Energy use for NUH Refers to the energy use of various provinces, autonomous regions and municipalities such as all urban areas in Beijing, Tianjin, Hebei, Shanxi, Inner Mongolia autonomous regions, Liaoning, Jilin, Heilongjiang, Shandong, Henan, Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang autonomous region and part of Sichuan province that uses district heating methods in winter. Heating is also needed for the cold winter in the Tibetan autonomous region, Western Sichuan and part of Guizhou provinces. However, the situations in Tibet, Western Sichuan and Guizhou are quite unique and thus should be treated independently. The reason for taking NUH energy use as an independent category is that district heating has been the main heating method in northern urban areas. This is the area where we would see many heat supply networks in cities and communities. Different from other types of building energy use, in which the calculation is based on the consumption of a single building or single households, the energy use for NUH depends mainly on the structure and the operation mode of the heating system, and the calculation of the heating energy use for northern urban areas is based on the heating system as a whole, which is why we regard the energy use of this area as an independent category. Based on heat sources and the scale of heating, centralized heating methods include largeand mid-scale combined heat and power generation (CHP), small-scale CHP, district coal-fired boiler, district gas-fired boiler, community-level coal-fired boiler, community-level gas-fired boiler, and centralized heat pump. Decentralized heating methods include household gas furnaces, household coal furnaces, air conditioners and direct electrical heating. The energy use considered in this report includes the primary energy consumption at the heat source and the power use of various related equipment (fan, water pump). The energy consumption can also be divided into transitional heat loss from heat sources and heating stations, heat loss from pipelines and transmission processes, and heat gain for buildings. Urban residential building energy use (excluding NUH) This refers to residential building energy use in urban areas excluding NUH. It includes energy use for household appliances, air conditioners, lighting, cooking, domestic hot water (DHW), and winter heating of the hot summer and cold winter (HSCW) climate zone. The energy types mainly include electricity, coal, natural gas, liquefied petroleum gas, etc. The main winter heating method in HSCW areas was decentralized, and the heat source included an air source heat pump, direct electrical heating, and local heating methods such as coal-fired pans, electrical heating blankets, and electrical handwarmers. Public and commercial building energy use (excluding NUH) Refers to buildings for public and commercial purposes, including offices, commercial buildings, tourism buildings, buildings for educational purposes, buildings for communication and buildings for transportation in urban and rural areas. Apart from NUH energy use, the energy use of P&C buildings includes air conditioning, lighting, electricity sockets, elevators, cooking, and winter

2.

3.

3.3 Energy Consumption of China’s Building Sector

41

heating in the HSCW zone. Electricity, natural gas, oil and coal are the main energy sources for P&C buildings. Rural residential buildings energy use This refers to the energy consumed by rural households, including cooking, heating, cooling, lighting, domestic hot water, household appliances, etc. Electricity, coal, LPG, natural gas and biomass energy (straw burning, firewood) are the major energy sources. Biomass was not included in national energy statistics, but it will be an independent category in this report.

4.

This section will explore the primary energy use situation of building operation. Electricity will be converted into primary energy use based on the national average coefficient of coal consumption for power supply in China. According to Standards for energy consumption of building GB/T 51161–2016, the fuel will be allocated in proportion to the power and heat exergy generated from CHP. The data of this report came from the China Building Energy Model (CBEM) from BERC, Tsinghua University, which delineated the status quo of China’s building energy consumption and its transformation between 2001 and 2019. From 2001 to 2019, the sum total building energy use increased dramatically, as shown in Fig. 3.18. In 2019, the total commercial energy use during the building operation stage amounted to 1.02 Gtce, accounting for 22% of the national energy consumption. The energy use of all building-related products and biomass was 1.11 Gtce (0.09 Gtce of biomass), and detailed information is presented in Table 3.1. The sum of the energy consumption and intensity of the four building types can be found in Fig. 3.19, in which the building floor area is represented by the horizontal axis and the energy intensity per square meter is represented by the vertical axis. The size of the square refers to the total energy use of the building. From the aspect of building stock, urban residential and rural residential were the biggest, and building stock with the NUH accounted for one fourth of the total, and P&C building one fifth of the total. Regarding energy intensity, P&C buildings and NUH occupied a higher percentage of the total. Therefore, it is fair to conclude that each category of building type occupied approximately one-fourth of the total energy use. Since the building

1,200

Energy consumption (Mtce)

Electricity consumption (PWh)

2.4

1,000

2.0

800

1.6

600

1.2

400

0.8

200

0.4

0

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

Commercial energy consumption

0.0

Electricity consumption

Fig. 3.18 Primary energy consumption and total electricity use for building operation in China (2001–2019)

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3 China’s Building Energy Use and GHG Emissions

Table 3.1 China building energy use (2019) Types of energy

Activity data (Floor space or number of households)

Electricity (TWh)

Commercial energy (Mtce)

Primary energy use intensity

NUH

15.2b m2

61.1

213

14.1 kgce/m2

UR buildings (Excluding NUH)

28.2b

m2

537.4

242

792 kgce/hh

P&C buildings (Excluding NUH)

13.4b m2

993.2

342

25.6 kgce/m2

RR buildings

22.8b m2

305.4

222

1527 kgce/hh

Total

1.4b people 64.4b m2

1897.2

1020

stock and energy intensity of P&C buildings have increased rapidly in recent years, P&C buildings have become the largest building energy consumer in the Chinese building sector. The shift of total energy use and energy intensity between 2008 and 2019 can be found in Fig. 3.20. While biomass energy use in rural areas decreased, energy use for all types of buildings increased significantly. The characteristics of the energy intensity of each type of building can be found as follows: • Although the energy intensity of NUH is relatively large, it has been decreasing in recent years, which was the result of energy efficiency improvement. • Energy intensity continued to increase for P&C buildings. The increasing energy demand of different kinds of end users (air conditioners, devices, lighting, etc.) was the major cause of the increase in building energy intensity. In recent years, many large-scale P&C buildings have been constructed, with much higher energy intensity than other P&C buildings. • The energy intensity of urban residential buildings increased continuously because there was more demand for domestic hot water, air conditioners, and household appliances, which led to more energy consumption. There was also a debate about heating methods in the HSCW zone. There was not too much increase in the energy use of lighting in residential buildings because of the adoption of energy-efficient illumination devices. The cooking energy intensity also remained basically unchanged. • Commercial energy intensity for rural residential buildings also increased. As the number of rural households and rural population slowly decreased, commercial energy use in rural areas basically remained stable. However, as household appliances became more popular and the policy of “switching from coal to electricity” in rural areas, the power consumption intensity has increased dramatically in recent years. Meanwhile, the use of biomass has dropped continuously, and the total energy use for rural residential buildings has declined slightly in recent years.

8.6

kgce/m2

14.1

25.6 kgce/m2

kgce/m2

152

m2

Floor area

Biomass 0.1 billion tce

0.22

22.8 billion m2

RR commericial billion tce

P&C (exl. NUH) 0.34 billion tce

13.4 billion m2

NUH 0.21 billion tce

UR exl. NUH 0.24 billion tce

Fig. 3.19 Energy use of building operation in China (2019)

Energy intensity

28.2 billion m2

4

kgce/m2

kgce/m2

9.3

3.3 Energy Consumption of China’s Building Sector 43

Energy intensity exl. NUH

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3 China’s Building Energy Use and GHG Emissions

300

25 20

200

400

30 25

300 20

15

200

15

10

100

5

0

0 2001

2003

2005

2007

2009

2011

Primary energy consumption(Mtce) left axis

2013

2015

2017

10 100

5 0

0 2001

2019

2003

2005

2007

2009

2011

Primary energy consumption(Mtce) left axis

Energy intensity(kgce/m2) right axis

(a) Northern urban heating

2013

2015

2017

2019

Energy intensity(kgce/m2) right axis

(b) Public and commercial building

300

1,000

800 200

400

2,000

300

1,500

200

1,000

100

500

600

400

100

200 0

0 2001

2003

2005

2007

2009

2011

Primary energy consumption(Mtce) left axis

2013

2015

2017

2019

Energy intensity(kgce/hh) right axis

Energy

(c) urban residential

0

0 2001

2003

2005

2007

2009

Biomass (Mtce) left axis Commercial energy intensity(kgce/hh) right axis

2011

2013

2015

2017

2019

Commercial energy (Mtce) left axis Biomass energy intensity(kgce/hh) right axis

(d) Rural residential

Fig. 3.20 Trend of total energy use and energy intensity for different subsectors (2001–2019)

1.

NUH energy use In 2019, the total energy consumption of NUH was 0.213 Gtce, 20% of the national total building operation stage. Between 2001 and 2019, the floor area of NUH tripled from 5 billion m2 to 15.2 billion m2 , but the total energy consumption increased by less than doubling. Thus, the increase in energy consumption was less than the increase in building floor area, which resulted in successful energy efficiency improvement. The energy intensity of NUH was 14.1 kgce/m2 in 2019, a significant decline from 23 kgce/m2 in 2001.

Specifically, the main reason for less energy use was because of the improvement of insulation, which resulted in the heat demand decrease of buildings, as well as a higher percentage of efficient heat source and building operation improvement. • Better building insulation. In recent years, the Ministry of Housing and Urban– Rural Development of the People’s Republic of China (MOHURD) has adopted various methods to improve building envelope insulation, including building energy efficiency standard systems covering different climate zones and types of buildings, special investigations of energy efficiency since 2004 and retrofitting programs on existing buildings during the Thirteenth Five-Year Plan. These methods have greatly enhanced building insulation and lowered the actual heating demand, and more detailed information can be found in Sect.3.2. • The share of efficient heat sources has been increasing. Overall, high energy efficiency heating methods such as CHP, district heating, and district boilers have been replacing small coal-fired boilers and single-family stoves, which resulted in a rapid decrease in the shares of the two latter heating methods. Various heat pumps have become exponentially popular, and there has been more gas heating.

3.3 Energy Consumption of China’s Building Sector

45

Moreover, the system efficiency has also been increasing notably in recent years, which drove the overall efficiency of various district heating methods. 2.

Urban residential building energy use (excluding NUH) Urban residential building energy use (excluding NUH) in 2019 was 0.242 Gtce, 24% of the total commercial energy use in the building sector. Electricity consumption was 537.4 Twh. With economic development and living standards improvement, urban residential building energy use grew by 8%, and the terminal electricity consumption in 2019 was 4 times higher than that in 2001.

Apart from NUH, cooking, household appliances and lighting consumed the most energy in urban residential buildings. Thanks to various national programs for improving the energy efficiency of cooking, household appliances and lighting, the terminal energy consumption of these three categories was kept under control, and the total energy consumption has undergone a slower increase in recent years. Improving energy efficiency and lowering stand-by energy consumption should be the optimal methods to limit cooking, household appliances and lighting energy use. For example, the promotion of energy-saving light bulbs significantly improved the lighting efficiency of residential buildings. Energy efficiency standards and behaviour need to be upgraded to lower the energy wasted from long stand-by time and frequent re-heating and restarting. The production standard needs to be improved to lower the energy use when televisions, water coolers and electric toilet seats are in stand-by mode. Improving the controllability of set-top boxes, the insulation capacity of water coolers and smart control toilet seats could also result in lower energy consumption. Subsidizing policies or encouragement should not be implemented to encourage people to buy dryers or other appliances that may lead to an energy consumption jump. Even though the energy use for winter heating, summer cooling and domestic hot water (DHW) accounts for a smaller percentage in hot summer cold winter (HSCW) regions on a per unit household basis, it has been growing rapidly. The annual average growth rate of energy consumption in these regions could be well over 50%. Therefore, saving terminal energy use for those three categories in residential buildings should be our priority in the future. We should avoid the massive application of centralized systems and promote decentralized systems in residential buildings with high energy efficiency standards. Improving the indoor service level while avoiding drastic energy consumption increases. 3.

P&C building energy use (excluding NUH) In 2019, the total floor space of China’s P&C building was approximately 13.4 billion m2 , with 0.342 Gtce of energy consumption (excluding NUH), 34% of the building sector. Electricity use of the P&C building stood at 993.2 TWh. The total floor space and the proportion of large P&C buildings were all on the rise, which led to an increase in energy demand. Energy intensity grew rapidly from 17 kgce/m2 in 2001 to over 26 kgce/m2 , and the total energy consumption surged as well. This was the result of the installation of centralized cooling systems in newly completed large P&C buildings in recent years, and its

46

3 China’s Building Energy Use and GHG Emissions

energy intensity was over 100 kWh/m2 . Compared with some smaller schools, offices and stores with approximately 60 kWh/m2 of power intensity, the average electricity consumption will continue to increase as increasingly similar large P&C buildings come into place. China’s rapid urbanization led to substantial growth of the P&C building stock. Since 2001, the newly built building stock of P&C buildings amounted to almost 8 billion m2 , approximately 79% of the current stock. This means that one-third of P&C buildings were built after 2001. This was because there were more new commercial buildings, such as office buildings and malls. On the other hand, China is building a well-off society in an all-around way by improving public service, perfecting public infrastructures and building more public service buildings such as schools, hospitals, sports stadiums, etc. While the stock of P&C buildings is growing, the number of large-scale P&C buildings is also increasing, of which the energy intensities of cooling systems, ventilation, lighting and elevators are far higher than those of normal P&C buildings. This was the key reason why China’s P&C building energy intensity continues to grow. 4.

Rural residential building energy use

In 2019, the commercial energy consumption of rural residential buildings was 0.222 Gtce, 22% of the total. Electricity consumption was 305.4 TWh, and biomass (straw and firewood), 0.09 Gtce. As urbanization developed, the rural population declined from 800 to 550 million between 2001 and 2019, and the rural residential floor space was maintained at approximately 23 billion m2 . Owing to the higher availability of electricity in rural areas, higher income for rural residents and more household appliances in recent years, per household electricity consumption has increased rapidly. For instance, the number of air conditioners per hundred households in rural areas increased from 16 in 2001 to 71 in 2019, which led not only to the growth of power consumption but also to the longer peak power load in rural areas during summer. Since the development of “switching from coal to electricity” in northern regions, winter heating electricity use and peak power load have been growing significantly. Moreover, biomass energy in rural areas has been gradually replaced by dispersed coal and other commercial energy sources, which led to a noticeable reduction in biomass consumption for day-to-day activities in rural areas. As one of the key methods for carbon reduction, the role of biomass and renewable energy will be more important in rural residential buildings. According to the Energy Technology Innovation Plan of Action (2016–2030), eco-energy farms, biomass and energy crops will be further developed in rural areas. The goal of biomass energy use was clearly delineated in the 13th Five-Year Plan, which was “promoting the use biomass pellets during cooking and heating in rural areas” while ensuring that biomass became the new industry for rural development. Meanwhile, China released the Work Plan for the Implementation of the PV Poverty Alleviation Project in 2014, in which the PV industry will be the key method to alleviate poverty in rural areas. To give full play to the abundant renewable energy resources in rural areas,

3.3 Energy Consumption of China’s Building Sector

47

improving rural livelihoods while keeping energy consumption under control by adopting comprehensive solutions and improving noncommercial energy efficiency hold the key to enhancing energy efficiency in rural residential buildings. It is also important to energy sustainability for China. In recent years, we have made more progress in smog control and clean heating in the eastern regions of China. Governments at all levels have made huge investments to improve the power supply, build gas pipelines and shift small household coal-fired stoves into emission reduction devices, which has led to increases in electricity and gas consumption. The change in rural energy structure will lead to a fundamental transformation of rural energy use patterns, which will facilitate urbanization in rural areas. It is essential for us to leverage this opportunity with a scientific strategy to revolutionize the relations of energy supply and demand. In this way, we will be able to usher in a brand-new energy system with renewables as the mainstay for rural residents, as well as facilitate China’s energy revolution.

3.4 GHG Emission of Building Sector 3.4.1 Embodied CO2 Emission of Building Sector The construction of buildings and infrastructures consumed a colossal amount of energy and emitted a huge amount of CO2 . In addition to energy-related emissions, the other major CO2 emitter was industry process emissions of cement.9 In 2019, the total embodied CO2 emissions of civil buildings amounted to 1.6 GtCO2 , and it has been declining since 2016 on an annual basis. The majority of embodied carbon emissions came from the manufacturing and transportation of building materials and the industrial process emissions of cement, registered at 77% and 20%, respectively (Fig. 3.21). Embodied carbon emissions from civil buildings accounted for 40% of the total embodied carbon emissions of the construction sector in China. In 2019, China’s total carbon emissions of the construction sector stood at 4.3 billion tons of CO2 , almost half of the total volume of society as a whole (Fig. 3.22).

3.4.2 CO2 Emission During Building Operation The CO2 emissions of building operation could be impacted by the growth of total building energy consumption and the change of energy structure. Electricity, coal and gas were the major energy sources for building operation. Electricity accounted for 70% of the total energy use in urban residential buildings and P&C buildings, 9

Refers to carbon emission from chemical reaction (excluding combustion) for producing cement.

48

3 China’s Building Energy Use and GHG Emissions

Fig. 3.21 Embodied carbon emissions of civil buildings. Source BERC Tsinghua University. Only for civil building

Fig. 3.22 Embodied carbon emissions of the construction sector in China (2004–2019). Source BERC Tsinghua University. The construction sector includes civil buildings, production buildings and infrastructure

in which CO2 was indirectly emitted. The adoption of CHP in NUH could also lead to indirect CO2 emissions. The percentage of coal consumption was higher than that of electricity for NUH and rural residential buildings, accounting for 80 and 60%, respectively, which led to massive direct CO2 emissions. As the percentage of zero-carbon electricity has increased in China, the average emission factors10 have declined tremendously, at 577 gCO2 /kWh in 2019. The share of electricity 10

National average per kWh emission factor can be found in the Annual Report of China Electric Power Industry compilated by China Electricity council.

3.4 GHG Emission of Building Sector

49

Carbon emission(GtCO 2) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 2001

2003

2005

Direct emission

2007

2009

2011

Indirect emisison(heat)

2013

2015

2017

2019

Indirect emission(electricity)

Fig. 3.23 CO2 emission of building operation (2019)

consumption has gradually increased during building operation as well. These are the reasons to facilitate the low carbon trend of building operation. In 2019, carbon emissions from China’s building operation energy consumption amounted to approximately 2.2 billion tons of CO2 , as shown in Fig. 3.23, in which direct carbon emissions were approximately 29% and indirect carbon emissions from electricity use and heating were 50 and 21%, respectively. In 2019, the per capita carbon emissions of building operations in China were 1.6 t/cap, and the per unit floor area carbon emissions were 35 kg/m2 . The shares of carbon emissions according to the four building types were 23% for rural residential buildings, 30% for P&C buildings, 26% for NUH and 21% for urban residential buildings. Figure 3.24 demonstrates the scale of carbon emissions, carbon intensity, and the total carbon emission volume according to the four building types. The horizontal axis represents building floor space, the vertical axis represents per square meter carbon emission intensity, and the size of the box represents the amount of carbon intensity for four building types. As illustrated by the figure, the carbon emission intensities of the four building types did not exactly correspond to the energy consumption. Due to the highest energy intensity of P&C buildings, the per unit floor area carbon emissions were also the highest at 48 kgCO2 /m2 . The carbon intensity of NUH ranked second due to its high percentage of coal combustion, at 36 kgCO2 /m2 . There was no apparent correlation of energy intensity between rural and urban residentials. However, owing to low electricity consumption and high coal combustion for rural residential buildings, the carbon intensity was higher than that of urban residential buildings. The per unit floor area carbon intensity for rural residential buildings was 23 kgCO2 /m2 , and it was 16 kgCO2 /m2 in rural residential buildings.

3 China’s Building Energy Use and GHG Emissions 28.2 billion m2

13.4 billion m2

22.8 billion m2

P&C

Co2 emission intensity

48

16 kgCO2/m2

kgCO2/m2

(exl. NUH)

0.65 billion tCO2

UR exl. NUH 0.46b billion tCO2

36 kgCO2/m2

RR 0.52 billion tCO2

23

kgCO2/m2

CO2 emission intensity exl. NUH

50

NUH 0.55 billion tCO2

152

m2

Floor area

Fig. 3.24 CO2 emissions from China building operation (2019)

3.4.3 Other GHG Emission in Building Sector Apart from CO2 emissions, the leakage of refrigerants from the use of cooling units, air conditioners, and refrigerators during building operation could also lead to GHG emissions and global warming. Therefore, non-CO2 GHGs could also be emitted during building operation. Because HFCs have zero ozone-depletion potential, they are regarded as the ideal replacement refrigerant to avoid ozone depletion. However, the global warming potential (GWP) value of HFCs is relatively high, and HFCs have become the major source of non-CO2 GHG emissions in the building sector. HFCs are mainly used as a refrigerant resource for air conditioners in the building sector, which is why HFCs are the second largest non-CO2 GHG polluter in China. According to Prof Hu Jianxin’s research from Peking University, the annual GHG emissions caused by HFC consumption for domestic and commercial ACs were approximately 100 million to 150 million tons of CO2 -eq,11 and they have been growing rapidly in recent years. It is worth noting that the amount of refrigerant in air cooling devices did not correspond with the total emission amount. This is because over 30% of China’s air-cooling devices were exported alongside its refrigerant. Meanwhile, the leakage of refrigerant in China’s air-cooling devices was much lower than the total refrigerant filled in the same year. This is because the number of installations for air-cooling

11

Hu Jianxin, Report on China’s HFCs emission reduction analysis.

3.4 GHG Emission of Building Sector

51

devices has been increasing annually. However, the amount of total leakage of refrigerant in China’s buildings should be the same as its total filling amount after an installation number remained stable in China. As China’s AC and refrigerator installation growth have been slowing down, coupled with a low replacement rate and newly found solutions for the problem of refrigerant leakage, there could be more room for non-CO2 GHG reduction in the building sector.

Chapter 4

Urban Residential Buildings Energy and Emissions

4.1 Urban Residential Buildings At the beginning of this chapter, we will explain the basic situation of urban areas, urban residential buildings and their energy consumption. Urban area consists of city areas and county. The former refers to the areas centering neighborhood committees where municipal government and district governments locate. The latter refers to areas outside of the city, centering neighborhood committees where county-level government locates.1 Urban residential buildings refer to buildings in city areas as well as in county areas. The energy use of residential buildings refers to the energy consumed by residents from air conditioning, heating (i.e., distributed heating, excluding district heating in northern urban areas), cooking, DHW, lighting and household appliances to meet the demands of living, studying and resting. The main energy sources are electricity and gas. China is undergoing rapid urbanization, and the population is growing by leaps and bounds. The population has been growing by 16 million in urban areas annually. From 2000 to 2019, the urban population grew from 459 to 771 million. The traditional family structures in China have also transferred in the midst of urbanization and social and economic development. Traditionally, a typical Chinese family consists of a husband and a wife with their offspring, and it is commonplace to see three to four generations, sometimes even five generations of family members living under the same roof. However, after reform and opening up, the traditional large and complex family structure has been morphed into a more simplified and smaller one to adapt to new ways of living. A smaller, simpler and more diverse family structure has become the main feature of a typical Chinese household since then. According to the China Statistical Yearbook, the number of people per Chinese household dropped from an average of 3.89 in 1985 to 2.82 in 2019.

1

Statistical review of urban–rural division, approved by the State Council of the People’s Republic of China on July 12th, 2008, [2008] No.60.

© China Architecture Publishing & Media Co., Ltd. 2022 S. Hu et al., China Building Energy Use and Carbon Emission Yearbook 2021, https://doi.org/10.1007/978-981-16-7578-2_4

53

54

1.

4 Urban Residential Buildings Energy and Emissions

The development of urban residential building construction

With the rapid development of urbanization, many residential buildings have risen up in urban areas to meet the demand of accommodation from new residents in cities. Between 1990 and 2000, most of the residential buildings in China were multistoried with small floor space, around 60–70 m2 , and the highest building was below 7 floors. This is one way to meet the huge demand for accommodation during urbanization. On the other hand, economic growth and the improvement of people’s livelihood have called for larger living space. From 2000 to 2010, the purpose of new residential buildings changed from meeting basic demand for accommodation to providing moderate space and a living environment in middle and high-rise buildings. During this period, most of the rooms in the building were approximately 80–90 m2 , with 60–70 m2 of floor space. More high rises can be seen during this period, as shown in Fig. 4.1. In recent years, rapid urbanization in China has led to fast population growth. On the other hand, as urban land resources have been declining, the cost for overall development has increased. Developers tried to improve returns by building high-rise high-density residential buildings. These are the reasons why high rises are the mainstay for urban residential buildings. In the meantime, the plot ratio and the elevation of high rises in China are increasing as well (Fig. 4.2). 2.

Area of urban residential household

The main types of units for existing residential buildings in China are small- and medium-sized apartments with 60–80 m2 and 80–100 m2 per household, respectively, as shown in Fig. 4.3 According to the national demographic census in 2015, the average space per household in city areas was 92 m2 , and the median was 80 m2 .

Fig. 4.1 Urban residential building floor space in different years (1990–2019)

4.1 Urban Residential Buildings

55

Fig. 4.2 Urban residential building floor numbers in different years (1990–2019) 100% 90% 80%

Frequency

70% 60% 50% 40% 30% 20% 10% 0% 0

20

40

60

80

100 120 140 160 180 200 220 240 260 280 300 Building floor area (m 2)

Fig. 4.3 Unit space for China’s residential buildings in urban areas (based on the demographic census conducted in 2015 on 1% of the population, sample size: 155,158 households)

The unit space per household for city area was smaller than that of county area and rural area, which were 118 and 119 m2 , respectively (Fig. 4.4). The number of floors for China’s residential buildings has been increasing, which is a reflection of increasing contradiction among land resources, demographics and ecology and the environment. With the rapid growth of China’s economy, urbanization has been greatly enhanced, which leads to a higher concentration of population in cities. On the other hand, people’s livelihood has been improving, and they begin to ask for better living conditions. Therefore, demand spikes from a quantity and

56

4 Urban Residential Buildings Energy and Emissions 300

Building floor area (m2)

250 p25

200

p5 150

p50

100

mean p95

50

p75 Beijing Tianjin Hebei Shanxi Inner Mongolia Liaoning Jilin Heilongjiang Shanghai Jiangsu Zhejiang Anhui Fujian Jiangxi Shandong Henan Hubei Hunan Guangdong Guangxi Hainan Chongqing Sichuan Guizhou Yunnan Tibet Shaanxi Gansu Qinghai Ningxia Xinjiang

0

Fig. 4.4 Unit space for China’s residential buildings in urban areas in different provinces (based on the demographic census conducted in 2015, sample size: 155,158 households)

30

billion m2

25 20 15 10 5 0 2000

2002

2004

2006 NUH

2008

2010

2012

2014

2016

2018

Others

Fig. 4.5 Total floor space of China’s urban residential buildings (2000–2019)

quality perspective. However, most of the cities in China are experiencing the crisis of resource shortages posed by rising populations and diminishing land resources and ecological challenges. Admittedly, populous cities with high building density will become commonplace for years to come in China, which is unavoidable and needs to be embraced. Therefore, the unit space of residential buildings in China should be properly contained, and the volume of urban residential buildings needs to be controlled.

4.1 Urban Residential Buildings

57

Fig. 4.6 Scaling up of China’s urban residential buildings (2001–2019)2

3.

Scaling up of urban residential buildings.

In the midst of urbanization, the total floor area of urban residential buildings grew from 7.1 billion m2 to 28.2 billion m2 from 2001 to 2019, an increase of nearly threefold. In 2019, the total floor area of urban residential buildings was 28.2 billion m2 , with 9.7 billion m2 for NUH and 39% of the total national urban residential floor area (Fig. 4.5). The living standards for urban residents have been greatly enhanced as well. The per capita residential floor area (total residential floor area divided by total urban population) in China increased from less than 20 m2 in 2001 to 33 m2 in 2019, as demonstrated in (Fig.4.6). According to the China Statistical Yearbook, the per capita floor area per household for urban residential buildings increased from 24.5 to 34 m2 in 2015 as a result of the national demographic census. This figure does not include student and military personnel and other groups who do not have houses. The data illustrated above are evidence showing the improvement of living standards of urban residents. The recent development of urbanization in China is gradually meeting the demand of urban residents. According to research conducted by Southwest University of Finance and Economics in 2017 on Chinese household financial status, the home ownership rate (the share of homeowners among all households) in 2017 was 90.2% for urban households, and the self-owned rate (the share of households who owned property rights among all households) was 80.8% for urban households, which was leading the world. In 2017, the ratio of complete urban residential housing to the 2 The data of total floor space and per capita floor space for urban residentials comes from CBEM, the data of per capita floor area per household for urban residential buildings comes from China Statistic Yearbook.

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4 Urban Residential Buildings Energy and Emissions

total number of households was 1.18, and the ratio of self-owned complete housing to total households was 1.155, meaning that there was at least one house per house. In recent years, vacant residential houses in urban areas have become a phenomenon that has attracted much attention. The vacancy rate of second-tier and third-tier cities is higher than that of first-tier cities. There are two kinds of vacant houses. The first refers to houses that remained uninhabited once the construction has been completed. These houses are the reason for financial risks and are subject to study by the Ministry of Housing and Urban Development of the PRC (MHURD). The second kind of vacant house refers to the empty houses among all the houses that have been sold. The vacant residential houses in this report refer to the latter. There are two reasons for this phenomenon: one is because of those who have one home and migrated to other places for work, and the other is those who possess multiple houses and do not rent out the house to others. China has yet to provide official data for the number of vacant residential houses in urban areas. According to research conducted by Southwest University of Finance and Economics in 2017 on Chinese household financial status, the vacancy rate of urban residential buildings was 18.4% in 2011, 19.5% in 2013, 20.6% in 2015 and 21.4% in 2017. It can be extrapolated that there were 65 million empty urban residential houses in 2017. Based on related studies, the natural vacancy rate of China’s urban residential buildings was 9.8%. The existing vacancy rate is clearly higher than the natural vacancy rate, and it is even higher in tier two and tier three cities. The large number of vacant houses has consumed a large amount of home loans and dampened the desire for consumption. Meanwhile, it also leads to increasing energy consumption for building material production, construction, decoration, and unnecessary household maintenance (e.g., basic water, electricity and heating device maintenance). These are the problems we need to tackle to reach carbon peaks and carbon neutrality. Therefore, the total floor area of China’s urban residential housing has reached 28.2 billion m2 , and the ratio of complete urban residential housing to the total number of households was 1.18, with 33 m2 of per capita floor area, which is close to the level of developed countries, as shown in Fig. 4.7. This also means that urban residential buildings can basically meet the demand of their residents, and we should focus on balancing the distribution of houses in the future in urban areas. As urbanization develops, there will be more than 1 billion Chinese people living in urban areas. Based on 35 m2 /cap of floor area, we need an additional 7 billion m2 of floor area to accommodate housing demand for urban residents, which would bring the total floor area of urban residential buildings to 35 billion m2 . There are 1–1.2 billion m2 of new urban residentials each year in China. Therefore, by 2030, the total floor area of China’s urban residential buildings will peak at 35 billion m2 and remain stable at this level. 4.

Analyzing the year of completion for existing urban residential housing

According to our analysis of the existing urban residential housing, we found that over half of the buildings were established after 2000. Based on the national census on 1% of the population and the survey against 432,447 households, 155,158 were

4.1 Urban Residential Buildings

59

Fig. 4.7 Building floor area between China and other countries. Source Odyssee Mure database, US Energy Information Agency database, database of Ministry of Land, Infrastructure, Transport and Tourism of Japan, IEA Buildings Summary, Satish Kumar (2019),3 NRCAN Energy Use Data Handbook Tables, Canada 100% After 2010

80%

2000-2010 1990-2000

60%

1980-1990 40%

1970-1980

1960-1970 20%

1949-1959 Before 1949

0% City area

Town area

Rural area

Fig. 4.8 China’s residential housing completion year distribution (2015 census)

households living in city areas, 107,228 households in town areas and 17,006 households in rural areas. We analyzed the year of completion for existing urban residential buildings based on the census results and the classification of city, town and rural areas. The results showed that over 90% of the residential buildings in China were completed after 1980, both in urban and rural. Meanwhile, more than half of all the residential buildings were built after 2000, as demonstrated in Fig. 4.8. Overall, the age of China’s urban residential housing is distributed between 10 and 40 years, the average age of residential buildings is 15 years, and the age of rural buildings is slightly higher than that of city and town areas. The detailed distribution 3

Satish Kumar et al. (2019). Estimating India’s commercial building stock to address the energy data challenge. Building Research & Information, 2019, 47, 24–37.

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4 Urban Residential Buildings Energy and Emissions

can be seen in Figs. 4.9, 4.10 and 4.11. There is little difference in the construction age distribution of residential buildings between different provinces in China, but the proportion of buildings constructed after 2000 is higher in the northern region 100%

25

80%

20

60%

15

40%

10

20%

5

0%

0

After 2010 2000-2010 Average age

Share

1990-2000 1980-1990 1970-1980

1960-1970 1949-1959

Before 1949

NUH regions

Yunnan

Guizhou

Hainan

Sichuan

Chongqing

Guangxi

Guangdong

Hubei

Hunan

Henan

Jiangxi

Anhui

Fujian

Jiangsu

Zhejiang

Shanghai

Ningxia

Xinjiang

Gansu

Qinghai

Tibet

Shaanxi

Shandong

Jilin

Heilongjiang

Liaoning

Inner Mongolia

Hebei

Tianjin

Shanxi

Beijing

Average age

Other regions

Fig. 4.9 Construction year distribution of residential buildings in China’s city area (2015 census, city) 100%

25

80%

20

60%

15

40%

10

20%

5

0%

0

After 2010 2000-2010 Average age

Share

1990-2000 1980-1990 1970-1980

1960-1970 1949-1959

Before 1949

NUH regions

Yunnan

Sichuan

Guizhou

Chongqing

Hainan

Guangxi

Guangdong

Hunan

Hubei

Henan

Jiangxi

Anhui

Fujian

Zhejiang

Jiangsu

Shanghai

Ningxia

Xinjiang

Gansu

Qinghai

Shaanxi

Tibet

Shandong

Heilongjiang

Jilin

Liaoning

Inner Mongolia

Shanxi

Hebei

Tianjin

Beijing

Average age

Other regions

Fig. 4.10 Construction year distribution of residential buildings in China’s town area (2015 census, town) 100%

25

80%

20

60%

15

40%

10

20%

5

0%

0

After 2010 2000-2010 Average age

Share

1990-2000

1980-1990 1970-1980

1960-1970 1949-1959 Before 1949

NUH regions

Yunnan

Sichuan

Guizhou

Chongqing

Hainan

Guangxi

Guangdong

Hunan

Hubei

Henan

Jiangxi

Anhui

Fujian

Zhejiang

Jiangsu

Shanghai

Ningxia

Xinjiang

Gansu

Qinghai

Shaanxi

Tibet

Shandong

Heilongjiang

Jilin

Liaoning

Inner Mongolia

Shanxi

Hebei

Tianjin

Beijing

Average age

Other regions

Fig. 4.11 Construction year distribution of residential buildings in China’s rural area (2015 census, rural)

4.1 Urban Residential Buildings

61

than in the southern region. Some regions started the process of urbanization later than others (e.g., Tibet). To enhance the performance of the building envelope, China promulgated the first design standard for the energy efficiency of residential buildings in 1986. The “JGJ 26-1986 Design Standard for Energy Efficiency of Civil Buildings (Residential Buildings with Heating demand)” was issued mainly for residential buildings in severely cold and cold areas in northern China where district heating is required. The energy efficiency standard for houses in cold and severely cold areas was subsequently enhanced in 1995 and 2010. The energy efficiency standard for residential buildings in hot summer and cold winter (HSCW) areas was also released and improved in 2003 and 2012. One of the keys of energy efficient design is to improve the performance of building envelopes to lower the heating demand in winter, which is especially relevant in NUH areas. The variation in heating demand could be as high as over threefold based on different design standards. Among the 28.2 billion m2 of existing urban residential buildings, approximately 4.9 billion m2 was constructed before 1990 with inferior envelope performance, of which 1.9 billion m2 was built in the NUH area, as demonstrated in Fig. 4.12. In addition, 8.3 billion m2 of urban residential buildings were built between 1990 and 2000, and 3.3 billion m2 was built in the NUH areas, where the insulation quality of the building envelope is relatively low. The heating demand of those buildings was significantly higher than that of other buildings that adopted the 2010 design standard for energy efficiency. In general, approximately 5.2 billion m2 of buildings needed energy efficiency improvement in the performance of envelopes. This will greatly improve insulation and conserve energy for heating. Since the 11th Five-Year Plan, China has carried out heat metering and building envelope energy efficiency renovation in the north. The detailed plans were delineated in the 11th and 12th Five-Year Plans for energy conservation of buildings. By 2016, over 1.3 billion m2 of floor areas completed energy-saving reconstruction in urban areas, among which 1.24 billion m2 was in the NUH area. Figure 4.13 shows Fig. 4.12 The distribution of the year of completion for urban residential buildings in China (2015, model estimation)

Before 1949 1%

1949-1959 1%

After 2010 12%

2000-2010 37%

1960-1970 1% 1970-1980 4%

1980-1990 16%

1990-2000 28%

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4 Urban Residential Buildings Energy and Emissions

Fig. 4.13 Building floor areas for energy-saving reconstruction in northern China during the 12th Five-Year-Plan period

the completion of building energy-saving reconstruction in northern China during the 12th Five-Year-Plan period. There was 5.2 billion m2 of floor area that needed renovation, and 4 billion m2 had yet to complete the job. Reasonable policies and technologies should be adopted to promote this work.

4.2 Envelope Retrofitting of Northern Urban Residential Buildings 4.2.1 Distribution and current heating demand According to our analysis, by 2015, there were approximately 1.9 billion m2 of buildings in the NUH area that were built before 1990, and 3.3 billion m2 of buildings were constructed between 1990 and 2000. According to the 13th Five-Year Plan, all the available residential buildings in the NUH area will be retrofitted for better energy efficiency by 2020, and the proportion of energy-saving buildings in the existing urban residential buildings will exceed 60% nationwide. Based on this target and the existing stock of unmodified urban residential buildings, the total retrofit demand for the NUH area would be 1–2 billion m2 during the 13th Five-Year-Plan period.4

4

Based on MHURD’s 13th Five-Year-Plan on Energy Efficiency and Green Development for Building Sector. For the actual data of unremodified building floor areas and the actual remodification areas, please refer to the 14th Five-Year-Plan.

4.2 Envelope Retrofitting of Northern Urban Residential Buildings

63

Fig. 4.14 Average heat demand per unit area of different types of residential buildings in some cities

Therefore, 3.2–4 billion m2 of buildings still need energy-saving retrofitting in the NUH area in China. According to data from some of the heat exchange stations of NUH residential housing between 2019 and 2020, the actual heat rate of different types of buildings in various regions and the distribution of heat demand per unit area of unmodified residential housing and the “third stage energy efficiency housing” (housing with energy efficiency level increased by 65% compares with buildings in 1981) can be seen in Figs. 4.14 and 4.15, respectively. Based on the HDD18 ranking, Qingdao has the lowest HDD (1907), and Harbin has the highest HDD (4696). The results of various surveys show that the average heat consumption of residential buildings where the initial stage- (1980s–1990s)/second stage- (1995–2005) or the third-stage energy-efficient standard is adopted is significantly lower than that of buildings with no energy-efficient approaches. Among others, buildings constructed under the third-stage standard saw a decrease of 14–40%. It is obvious from Fig. 4.15 that the distribution of heat consumption in nonenergy-efficient buildings varies significantly from place to place, with the highest examples in certain areas being approximately two to three times higher than the average figure of those constructed under the third-stage energy-efficient standard. The heat consumption rate in some nonenergy-efficient buildings reaches a surprising 1 GJ/m2 or even higher. As seen from the huge differences in the actual heat consumption of various types of buildings, strengthening the insulation on the building envelope, especially improving the insulation of old residential buildings with no energy-efficient approach, is an important way to reduce energy consumption for heating in northern China.

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4 Urban Residential Buildings Energy and Emissions

Fig. 4.15 Distribution of heat demand per unit area in some cities with no energy-saving standard and the energy-saving standards for third-stage buildings are adopted

4.2.2 Standards and Significance of Building Envelope Retrofit The classification of nonenergy-saving buildings and one/two/three-step energysaving buildings in northern heating areas is based on a series of standards, such as China’s “Design Standard for Energy Efficiency of Residential Buildings in Severe Cold and Cold Areas (JGJ26)”, which was first promulgated in 1986 and updated three times in 1995, 2010 and 2018. Such standards follow the concept of “energy saving percentages”, taking the heating energy consumption of buildings in Northern China built in the early 1980s as a benchmark, with the four standards corresponding to 30, 50, 65 and 75% energy saving targets for district heating systems. Some northern regions have even proposed fourth-stage energy-efficient design standards for residential buildings before 2018 (e.g., Beijing DB11/891-2012). The series of energy efficiency design standards for buildings in severely cold and cold regions set out limits for various types of building envelope thermal performance parameters, with different regulations for various northern cities and different building characteristics (e.g., number of stories, area ratio of window to wall, etc.), subject to heating degree days. Taking Beijing (B subregion of the cold zone) as an example, the standards for the thermal performance of the envelopes in each stage are shown in Table 4.1, as follows: In addition to heat dissipation from various types of envelopes, infiltration of cold air also plays an important role in the heating load of buildings. As the heat transfer coefficient of the external envelope decreases, the heat load by cold air infiltration

4.2 Envelope Retrofitting of Northern Urban Residential Buildings Table 4.1 K-values for residential building envelopes under different energy-efficient design standards (unit: W/(m2 K))

65

Exterior wall Window Roofing Benchmark building (1980s) 1.57

6.4

1.26

Save by 30% (JGJ 26-1986) 1.28

6.4

0.91

Save by 50% (JGJ 26-1995) 1.16

4.7

0.8

Save by 65% (JGJ 26-2010) 0.6

3.1

0.45

Save by 75% (JGJ 26-2018) 0.45

2.2

0.3

Note The data given in the table are the design specification limits for buildings with 4 or more stories and a window-wall ratio of 0.3 or less in Beijing

Table 4.2 Heat demand of buildings in Beijing under different energy saving scenarios

Type of building

Heat consumption (GJ/m2 )

Benchmark building

0.34

Save by 30% (initial stage)

0.27

Save by 50% (second stage)

0.22

Save by 65% (third stage)

0.17

Save by 75% (fourth stage)

0.14

accounts for an increasingly high proportion. In this regard, the JGJ26 series of standards imposes requirements on the airtightness of doors and windows. The three standards prior to 2010 required the air infiltration rate of doors and windows to be ≤2.5 m3 /(m h) per meter of crack per hour, while the latest standard (JGJ26-2018) updated the limit to ≤1.5 m3 /(m-h). However, as cold air infiltration is also influenced by the behaviour of residents, such as opening windows and doors, the air change rate is not specifically stipulated in the standard. Only a 0.5 h−1 air change rate is provided as a reference. Relevant literature5,6 has defined the percentage of energy savings of buildings in design standards where the building envelope significantly reduces the heat demand of buildings. Taking Beijing as an example, the heat demand of buildings under different energy saving scenarios is given in Table 4.2. The theoretical heat demand per unit area of buildings meeting the third-stage energy efficient standard in Beijing is only 0.17 GJ/m2 (with 2041 heating degree days), while that of the buildings meeting the fourth-stage energy efficient standard is only 0.14 GJ/m2 . The average heat demand of buildings in Beijing in the 2019–2020 heating season is 0.24 GJ/m2 . With the application of energy-saving technologies, the management and operation

5

LANG Si-wei. Pegged to 65%—some thoughts about revising the energy-saving design standard for residential buildings in Northern China [J]. Construction Science and Technology, 2003(08):14– 15. 6 LIN Hai-yan, LANG Si-wei. Description of several issues in energy-saving design standards for buildings [J]. Construction Science and Technology, 2007(06): 58–59.

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4 Urban Residential Buildings Energy and Emissions

of most heating enterprises have been significantly improved, but the existence of not energy efficient buildings has left the average heat demand per unit area relatively high. To further understand the differences in the actual heat demand of various types of buildings, we tested the heat demand and average indoor temperature of several buildings in Chifeng, Inner Mongolia Autonomous Region. The test results in Table 4.3 show that the indoor temperature of the buildings constructed under the third stage energy-efficient standard is basically above 22 °C, while the nonenergy efficient buildings are generally approximately 18 °C, indicating the significant influence of envelope insulation on the quality of heating. By correcting the room temperature to a uniform 20 °C, the actual heat demand of the building at the designed indoor temperature is obtained, as shown in Table 4.3 and Fig. 4.16, with the average heat demand of a nonenergy efficient building being 1.8 times higher than that of a building constructed under the third stage energy efficient standard, and the average heat demand of the bungalows being five times higher than that of buildings of the third stage energy-saving standard. Whether from the design standard or from the actual heat consumption, insulation retrofitting of a nonenergy-efficient building envelope has a huge energy-saving potential, and the heat consumption reduction effect is obvious. At present, a small number of buildings are so poorly insulated that their heating demand is several times greater than the others, seriously impacting the heating reform, which takes the heating metering fee as the breakthrough. Although the reform from a planned economy to a market economy was initiated 20 years ago, huge differences in the insulation performance of the building envelopes have led to huge differences in the heat consumption per unit area. If residents are billed according to the actual heat they consume, those who live in nonenergy-efficient buildings built in the early years would pay 2–3 times more than those living in well-insulated commercial residential buildings built in this century. Table 4.3 Average heat consumption per unit area before and after temperature correction Building of third stage energy-saving standard Average room 23.4 temperature (°C)

Building of second stage energy-saving standard

Non-energyefficient buildings

Non-energyefficient bungalows

23.0

18.0

19.4

Actual average heat consumption (GJ/m2 )

0.35

0.50

0.48

1.39

Corrected average heat consumption (GJ/m2 )

0.29

0.43

0.53

1.46

4.2 Envelope Retrofitting of Northern Urban Residential Buildings

67

Fig. 4.16 Comparison of actual heat demand in different types of buildings in Chifeng

Most of the residents in non-insulated buildings belong to the low-income group compared to those in commercial residential buildings, so if the heating bills are issued strictly according to the heat metering, the low-income group living in noninsulated buildings with low room temperatures will have to pay several times more for the same floor area. The majority of such dwellers do not choose to live in old buildings but as a result of inheritance or housing reform. These low-income groups cannot afford to pay the high prices and have to continue to live in the housing allocated to them by the companies they used to work for. The heating cost exceeding the necessity shall not be borne by the occupants. Therefore, some local governments have proposed that “the excess of the cost should be settled according to the area”, but that is to hold the heating enterprises responsible for such excess of cost. As profit-oriented, enterprises find it difficult for them to take the initiative to assume this part of social responsibility. This has resulted in heating enterprises resisting the “heating reform” in various ways, making it very difficult to make any obvious progress for the past twenty years. The extreme imbalance in heat demand is the root cause of the difficulty in promoting heating reform. Determination to carry out retrofitting of these noninsulated buildings, which account for approximately 30% of the total urban residential buildings in northern China, is also the key to promoting heating reform based on heat metering. Therefore, retrofitting the envelopes of nonenergy efficient buildings not only saves energy and reduces heat consumption but also solves the current dilemma encountered in heating reform.

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4 Urban Residential Buildings Energy and Emissions

4.2.3 Upgrading Techniques of Building Envelopes and Upgrading Results To further explore the differences in the envelopes between nonenergy efficient buildings and well-insulated energy efficient buildings, as well as to analyze the effects and costs of such upgrading efforts, the results of field tests on the heat consumption of some buildings in Chifeng City, Inner Mongolia Autonomous Region, are taken here as examples. The heating period in the field is from October 15 to April 15, for a total of 183 days, with an average outdoor temperature of −4.5 °C during the heating season. The buildings tested in the field include those constructed under the third-stage energy-efficient standard (4 buildings), those under the third-stage energy-efficient standard (4 buildings), not energy-efficient buildings (4 buildings) and bungalows (6 buildings). The third-stage buildings are mainly new high-rise buildings built after 2010, the second-stage buildings were built around 2000 and were upgraded during the 12th Five-Year Plan period, and the non-energy efficient

Fig. 4.17 Photos of the buildings tested

Table 4.4 Basic forms of the building envelopes tested Type of building

Exterior wall

Outer window

Building of third stage energy-saving standard

200 mm reinforced concrete + 80 mm Polystyrene Insulation board

Triple glazed uPVC 120 mm reinforced windows or aluminum concrete + 140 mm alloy windows polyphenylene board

Roof

Building of second stage energy-saving standard

370 mm Hollow Brick + 50EPS insulation module

Double glazed uPVC windows

Non-energy-saving buildings

370 mm hollow or solid Double-glazed steel brick, some upgraded windows, some with insulation upgraded to double-glazed uPVC windows

Concrete floor with no insulation

Non-energy-saving bungalows

370 mm hollow or solid Mostly double-glazed brick steel windows

Concrete floor with no insulation

Flat roof + insulation Shed roof (remain as it is)

4.2 Envelope Retrofitting of Northern Urban Residential Buildings

69

Table 4.5 Heat consumption per unit area after temperature corrections of different locations of the buildings (GJ/m2 ) Location

Building of third stage energy-efficient standard

Building of second Non-energystage energyefficient efficient standard buildings

Non-energyefficient bungalows

Exterior wall

0.11

0.10

0.19

0.55

Outer window

0.12

0.17

0.15

0.28

Roofing

0.01

0.07

0.08

0.52

Stairwell

0.00

0.01

0.09

0.00

Ventilation or air exchange

0.18

0.23

0.16

0.34

−0.14

−0.16

−0.14

−0.23

0.29

0.43

0.53

1.46

Heat gained Total heat consumption

Note The heat gains include radiation and heat originating from people and equipment

buildings were mainly built between 1980 and 2000. Figure 4.17 and Table 4.4 are overviews of the buildings tested. The composition of the heat load for the different types of buildings was obtained through on-site tests and converted into the actual heat consumption for each part, as shown in Table 4.5. Overall, as the level of insulation increases, the heat consumption per unit area of the building decreases gradually. In energy-efficient buildings, the proportion of heat loss through ventilation is greater because the insulation of the envelope is improved, but the building still maintains a certain amount of ventilation, even more so when the room temperature is high because residents may open windows for ventilation. For nonenergy-efficient buildings, heat loss through external walls, roofs and floors occupies the most significant part. Especially for not energy efficient bungalows, roof heat transfer has a greater impact on the total heat consumption due to the large shape coefficient. Tests on the heat transfer coefficient of the main external walls of each building found that energy-efficient buildings using external insulation structures of different thicknesses result in a heat transfer coefficient of 0.5–0.6 W/(m2 K), while nonenergyefficient buildings that mainly use 37 mm hollow bricks result in a heat transfer coefficient of approximately 1.1 W/(m2 K). In nonenergy efficient buildings, some users have their own external walls retrofitted. The heat transfer coefficient can also be reduced to approximately 0.5 W/(m2 K) by wrapping polystyrene foam. The heat transfer coefficient of roofs can be controlled to approximately 0.4 W/(m2 K) in buildings constructed under the third-stage energy-efficient standard and approximately 1 W/(m2 K) in other types of buildings. Most of the new buildings and renovated buildings for energy saving purposes use double glazed uPVC windows or aluminum alloy windows with a heat transfer coefficient of approximately 2.5 W/(m2 K). Compared to traditional steel windows with a heat transfer coefficient of 4 W/(m2 K), such windows can not only significantly

70 Table 4.6 Locations and methods used in the upgrading of buildings

4 Urban Residential Buildings Energy and Emissions Location

Method

Exterior/basement ceiling/balcony wall

Install 50 mm EPS insulation board

Outer window

Replace with uPVC windows

Roofing

Install 50 mm EPS insulation board + waterproof layer

Stair door

Replace with an insulated security door and a door closer

reduce the heat transfer but also greatly enhance the airtightness and effectively reduce the heat dissipation from ventilation and air exchange. For energy-efficient buildings, the indoor temperature is generally high, and a large number of users involved in the field research phenomenally open windows to “cool down”. Although the buildings themselves are airtight, the actual air change rate is 0.4–0.9 h−1 due to user habits. In contrast, the actual air change rate in not energy-efficient buildings is less than that in energy-efficient buildings due to the low indoor temperature, which is distributed between 0.3 and 0.6 h−1 . Again, we take some non-energy-efficient buildings in Chifeng City as an example to analyze the cost input and energy-saving benefits that upgrading such buildings can cause. Sintered bricks with a thickness of 37 mm were used to build the external walls with single-sided plastering. The external windows were originally singleglazed steel windows, the roof was made of 200 mm reinforced concrete, and the heat consumption per unit area of the building was 0.48 GJ/m2 before upgrading. Table 4.6 shows the locations and the methods used in the upgrading. The most significant cost incurred is the construction cost, which includes the cost of main materials, auxiliary materials and construction expenditures. The construction cost is based on the current market price, referring to the typical upgrading cases included in Energy Efficiency Upgrading Guidelines for Existing Residential Buildings (Tables 4.7 and 4.8).7 The energy savings generated by each means are shown in Fig. 4.18, and the local heating cost is approximately 25 yuan/GJ, resulting in a static payback period for each upgrading method in this case scenario. Among the various upgrading methods, the upgrading of stair doors, balcony walls and outer windows results in obvious energysaving effects and economic benefits as less space is involved, with lower construction difficulty and shorter static payback period. As evidenced in the field research, we found that many users of not energy-efficient residential buildings upgraded their balcony walls and outer windows on their own. However, in this case, the heating cost is the cost after the subsidy, and if the heat price is set at approximately 50 yuan/GJ according to the actual operating cost, the payback period for the upgrading efforts will be between 5 and 15 years, and the economic benefits of energy-saving upgrading are obvious. Therefore, to set a scientific pricing mechanism at the user end so that 7

LIU Yue-li, Energy Efficiency Upgrading Guidelines for Existing Residential Buildings [M]. 2012, Beijing: China Building Industry Press.

4.2 Envelope Retrofitting of Northern Urban Residential Buildings

71

Table 4.7 Construction cost for the upgrading Item

Main materials

Ancillary materials

Labor

EPS insulation

350 yuan/m2

Binding mortar 3.6 yuan/m2 Crack-resistant mortar 3.6 yuan/m2 Mesh fabric 5 yuan/m2 Other 2.7 yuan/m2

Construction 20 yuan/m2 Demolition10 yuan/m2

Outer window replacement

Hollow glass casement window 240 yuan/m2

Auxiliary materials 10 yuan/m2

Construction 10 yuan/m2

Roof

350 yuan/m2

Binding mortar 3.6 yuan/m2 Crack-resistant mortar 3.6 yuan/m2 Other 10 yuan/m2

Construction 20 yuan/m2 Demolition10 yuan/m2 Renovation 10 yuan/m2

Stair door

Manufacturing and installation of thermal insulating door 3000 yuan/set

Table 4.8 Technical costs and static payback periods for each upgrading method Upgrading cost per unit area (Yuan/m2 ) Stair door

Static payback period (Year)

5.6

10.3

Balcony wall

11.3

14.5

Outer window

52.9

17.0

Roofing

22.3

17.3

External wall

28.1

28.1

Basement ceiling

18.5

34.1

Fig. 4.18 Energy savings per unit area for each upgrading method

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4 Urban Residential Buildings Energy and Emissions

the measured heat price can truly reflect the costs of upstream production, purchase and delivery is also the key to promoting energy-saving upgrading of the building envelopes. With the improvement of energy efficiency upgrading technology and the promotion of such projects, the material costs thereof do not vary greatly from region to region, with the main differences being in the labor costs and the costs of preliminary design and later maintenance. However, the static payback period varies greatly from region to region due to differences in the current heat consumption of nonenergy efficient buildings and the cost of centralized heating systems in Northern China. The higher the heat consumption of existing nonenergy efficient buildings before upgrading and the higher the local heating costs, the shorter the static payback period for envelope upgrading. For nonenergy efficient buildings with different heat consumption statuses, the theoretically calculated heat consumption q0 for a building constructed under the third-stage energy efficient standard is used as a benchmark, and the payback periods for energy efficiency upgrading are shown in Fig. 4.19 for each building type (heat consumption of 2.5q0 /2 q0/ 1.6q0/ 1.3 q0) in terms of outdoor parameters in Harbin City and Zhengzhou City. When the heat consumption of nonenergy efficient buildings reaches more than two times that of the building of the third stage energy-efficient standard, the payback period for the upgrading is all within 40 years, and for Harbin, where the heating season lasts for six months, the payback period is only 10–15 years.

Fig. 4.19 Static payback period for energy efficiency upgrading methods at different heating costs for various types of residential buildings

4.2 Envelope Retrofitting of Northern Urban Residential Buildings

73

4.2.4 Recommendations for the Future A comprehensive view of existing policies shows that the relevant authorities have been promoting the upgrading of existing nonenergy efficient residential buildings not only by issuing design codes as technical standards but also corresponding financial subsidies. In 2007, the Ministry of Finance issued the Interim Measures for the Management of Incentive Funds for Heat Metering and Energy-saving Upgrading of Existing Residential Buildings in Northern China, which stipulates subsidies for heat metering and energy-saving upgrading of existing residential buildings in severely cold and cold areas at benchmarks of 55 yuan/m2 and 45 yuan/m2 , respectively. The subsidies apply to upgrading the building envelopes, upgrading the metering of indoor heating systems and temperature control, and upgrading the heat source and heat balance between heating pipe networks. The subsidies are hence allocated at a ratio of 6:3:1. Some provinces, such as Shanxi, Inner Mongolia and Qinghai, have implemented matching funds with central financial subsidies at a ratio of 1:1. With the support and impetus of relevant policies, a total of 180 million m2 of building areas underwent energy-efficient upgrading during the 11th Five-Year Plan period in Northern China where heating was necessary, and by the end of 2015, the figure reached a total of 990 million m2 for the 12th Five-Year Plan period, which was 1.4 times the planned target. Although the results of the upgrading work have been remarkable, given the current stock of the nonenergy efficient buildings in the northern regions and the aim of promoting heating reform, there is still a need to improve the relevant mechanisms to promote the upgrading efforts for nonenergy efficient buildings. The uneven quality of building insulation and the financial capability of households are major obstacles to the implementation of heat metering reform in northern China. Most of the nonenergy efficient buildings were built before 2000, and their heat consumption was much higher than that of new energy efficient buildings in the same area. Such buildings were built in the background of the planned economy, although property rights are now owned by households. When they were built, the funds came in a planned manner, and the dominating purpose was to have people settled in, with little attention given to the building insulation, which is a historical legacy. With the reform of the energy system, it is now appropriate to promote the upgrading of envelope insulation while making full use of market mechanisms. It is therefore recommended that a special energy efficiency fund for existing buildings be set up, financed and managed by a third party unrelated to heating enterprises and residents and used exclusively to subsidize buildings with high heat consumption built before 2000, subject to the age of the building and the actual heat consumption. At the same time, reform on the metering of heat consumption should be carried out simultaneously to enable heat supply enterprises to operate in a fully market-oriented manner. The independent special fund should be put aside specifically to cover the part of the heat cost of the old blocks that exceeds the heat costs calculated on the basis of the total area or as a one-off investment to bring the heat consumption of the buildings up to the standard by upgrading the envelopes,

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4 Urban Residential Buildings Energy and Emissions

after which the heat cost should no longer be subsidized. Through such a change in mechanism, the social responsibility for ensuring heating in non-energy-efficient buildings rests with the said independent social fund, the heating service enterprises operate at a profit, the heating metering charges will then gain support from all sides involved, and the reform can proceed smoothly.

4.3 Natural Gas Use in Urban Residential Buildings 4.3.1 Household Natural Gas Use and Distribution in Urban Residential Buildings For urban households in China, the demand for natural gas comes mainly from heating, domestic hot water and cooking. In addition to cooking, the demand for natural gas for heating and domestic hot water varies considerably from household to household and can be divided into four main categories: gas heating + gas boiled hot water, non-gas heating + gas boiled hot water, gas heating + non-gas boiled hot water, and non-gas heating + non-gas boiled hot water. Due to the greater energy intensity of heating in northern China, the heating method can have a greater impact on total household gas consumption than domestic hot water and cooking. Therefore, this chapter introduces the research results on the average household natural gas consumption and the distribution in urban areas of Beijing based on different methods of heating. A total of over 100,000 households have been surveyed.

Fig. 4.20 Comparison of natural gas consumption between self-heating and non-self-heating households in Beijing

4.3 Natural Gas Use in Urban Residential Buildings

75

Fig. 4.21 Histogram of the distribution of average household gas consumption in non-self-heating residential buildings in Beijing8

Comparing the gas use of self-heating and non-self-heating households, as shown in Fig. 4.20, it can be seen that the total gas consumption in self-heating households is much higher than that of non-self-heating households. The average annual consumption of natural gas in self-heating households is 666 m3 /year, with a median level of 635 m3 /year. For households with district heating, the average consumption is 119 m3 /year, and the median level is 103 m3 /year. On the basis of the above data, assuming that the average amount of gas consumed for cooking and hot water in both types of households is similar, the annual heating gas consumption of those selfheating households is approximately 550 m3 /year. Assuming the average household floor area is 90 m2 , the heating intensity is approximately 6 m3 /m2 . Further statistical analysis of the distribution of gas consumption in non-selfheating households is performed, as shown in Figs. 4.21 and 4.22. For the majority of residential buildings, the average household consumption of natural gas is between 50 and 150 m3 per year. Only 135 residential buildings in the sample have an average household gas consumption above 200 m3 /year, meaning that close to 90% of residential buildings consume less than 200 m3 of natural gas on average each year, as shown in Fig. 4.21. In addition, further analysis was carried out for the nonself-heating buildings with data sampling from 2015 to 2018, and the results are shown in Fig. 4.23. There is a rather marked polarization in the consumption of gas in residential households, and the difference in terms of gas consumption between the upper quartile and the lower quartile gradually widens, mainly due to changes in residents’ lifestyles. On the one hand, as household income increases, the penetration rate of water heaters and the amount of domestic hot water used in some households are on the rise, 8

This chart is a statistical analysis of the average gas consumption of households in different buildings on a building-by-building basis.

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Fig. 4.22 Distribution diagram of the distribution of average household gas consumption in nonself-heating residential buildings in Beijing9

Fig. 4.23 Changes in gas consumption in non-self-heating buildings

leading to higher gas consumption for domestic hot water. On the other hand, due to the change in lifestyle, the proportion of residents cooking at home has decreased, and the proportion of electric cookers has increased as a result of the renewal of cooking appliances. These factors lead to a year-on-year decrease in cooking energy consumption. 9

The figures in this chart represents a statistical analysis of the average gas consumption of households in different buildings on a building-by-building basis, excluding certain buildings where the statistics are missing.

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4.3.2 Electrification of Cooking 1.

Types of cooking energy use

In terms of cooking energy, as shown in Fig. 4.24, taking Beijing as an example, the majority of households use piped gas as the main cooking energy source, accounting for 74% of the total number of households. In addition, 13 and 11% of households mainly use electric cookware and LPG, respectively. These three energy sources together account for 98% of the total, which are the three main cooking energy sources currently used by Chinese households. From a nationwide perspective, according to the data released in the China Urban and Rural Construction Statistical Yearbook, the penetration rate of natural gas in cities, counties, designated towns and rural areas all showed an upward trend during the period 2005–2018. Natural gas penetration rates in cities and counties rose markedly, reaching 97.3 and 86.5%, respectively, in 2018, while the gas penetration rates in designated towns and villages were still low, at 52.4 and 25.6%, respectively (Fig. 4.25).

4.3.2.1

(2) Gas Consumption Intensity in Cooking

To understand the energy consumption intensity of typical households, a questionnaire survey was conducted on the cooking habits of households in Beijing, and the results are shown in Fig. 4.26. It can be found that eating at least one meal (supper) at home every day is the lifestyle of the vast majority of households, accounting for 56%, while 26% of households eat all three meals at home every day, and 16% of households eat at home no more than seven times a week. Fig. 4.24 Distribution of household cooking energy use in Beijing (2018)

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Fig. 4.25 China’s gas penetration rate (gas-using population/resident population)10

Fig. 4.26 Cooking habits of Beijing households (2018)

To further estimate the energy intensity, a typical household that occasionally eats at home was selected, their cooking habits were surveyed, and the results are shown in Table 4.9. According to their cooking habits, the household’s annual consumption of natural gas for cooking is approximately 65 m3 .

10

Source China Urban and Rural Construction Statistical Yearbook.

4.3 Natural Gas Use in Urban Residential Buildings Table 4.9 Estimates of gas consumption for cooking in typical households

Average number of meals at home per week

10a

Average time used when cooking a meal (min)

20

The number of gas burners used per meal

1

Thermal power of gas stove kW

4 m3

0.38

Annual cooking gas consumption m3

65.6

Natural gas consumption per hour

4.3.2.2

79

(3) Electrification of Cooking Methods

Low-carbon energy systems based on renewable energy are the inevitable direction of energy transformation in China. The main sources of zero-carbon energy are nuclear power, hydropower, wind power, photoelectricity and biomass energy, and the direct form of energy output is shifted from fossil energy to electricity. The low-carbon energy transition requires the energy demand side to also be fully electrified, which will lead to a huge change in the way energy is used at the end of the building sector. In fact, most energy-using equipment in buildings is now electrified, and cooking is one of the few end-uses that still requires fossil energy. To achieve a zero-carbon transition in the residential building sector, we need to promote the electrification of cooking methods in households. In fact, electrification of cooking methods has been an important trend in China’s urban households over the past decade. First, the annual sales of various types of electric cookware in China are large, as shown in Fig. 4.27. The annual sales volumes of electric cookers, induction cookers, microwave ovens and other electric cookware in the past five years were maintained at approximately 50 million units, 30 million units and 10 million units, respectively, indicating that the demand for electric cookware in China’s residential households is huge.

Fig. 4.27 Domestic sales of various types of electric cookware in China

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Fig. 4.28 Main uses of energy in Beijing households

Second, the ownership of electric cookware in China’s urban households is also at a high level, with a high penetration rate of electric rice cookers, for example. As early as 2012, electric rice cookers owned by every 100 urban and rural residents exceeded 100 units. According to the data released by the National Bureau of Statistics, microwave ovens owned by every 100 urban households also rose from 50.6 units in 2013 to 55.7 units in 2019. Third, the cooking habits of residents are changing too. Comparing the research results in 2012 and 2018, the number of households in Beijing that use electric cookware as their main cooking tool rose from 7 to 13% (Fig. 4.28). At present, electric cooking technology is also continuously progressing. Apart from traditional rice cookers, electric cookers, microwave ovens, and other electric cookware, new types of cooking utensils, such as electric flame stoves that suit the traditional cooking habits of Chinese residents, are also emerging, which will also play a role in the electrification of cooking methods in China.

4.3.3 Electrification of DHW (2) DHW use and its future With the improvement of people’s living standards, the popularity of domestic hot water is growing rapidly, and the number of water heaters owned by every 100 urban households in China grew rapidly from 80.3 units in 2013 to 98.2 units in 2019, as shown in Fig. 4.29, a near 100% penetration rate in urban households. In 2001, however, the figure was only 52. Figures 4.30 and 4.31 show the distribution of hot water equipment for household use in Beijing and Shanghai in 2018. At present, electric water heaters and gas water heaters are the most commonly used domestic hot water equipment in urban households, but there are differences in their distribution in northern and southern China.

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Fig. 4.29 Ownership of domestic hot water equipment in Beijing

Fig. 4.30 Distribution of domestic hot water equipment in Beijing

The main water heating equipment used by Beijing residents is electric water heaters, accounting for 51%, while the main water heating equipment used by Shanghai residents is gas water heaters, accounting for 61%. In addition to the above two types of water heaters, solar water heaters and electric heat pump water heaters are also commonly seen in households. Electric heat pump water heaters have gained a rather promising momentum of development in recent years but are still in the early market stage and currently account for a relatively small share.

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Fig. 4.31 Distribution of domestic hot water equipment in Shanghai

4.3.3.1

Energy Intensity of DHW

In general, the difference in water consumption is one of the most important factors affecting the energy consumption of hot water in households. Taking Beijing as an example, a survey on the main domestic hot water usage of urban residents in China is shown in Fig. 4.32, and it can be found that the most important domestic hot water usage of urban households is showering, followed by washing face and hands as well as washing dishes. Only approximately 30% of the total households will use domestic hot water for bathtubs.

Fig. 4.32 Domestic hot water usage in Beijing in 2018

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Fig. 4.33 Comparison of water consumption between Chinese and foreign households (L/household/day)11

Table 4.10 Estimated gas consumption for domestic hot water in a typical household

Average domestic hot water consumption (L/household/day)

50

Set temperature of gas water heater (°C)

45

Average tap water supply temperature (°C)

10

Gas water heater efficiency

90%

Annual gas consumption for domestic hot water (m3 )

82.8

The abovementioned domestic water use habits are also the main reason why China’s household domestic water use is much lower than that of developed countries. Urban residents in China are mainly accustomed to showering, while developed countries such as Japan prefer baths. According to studies performed by the Building Energy Research Centre, Tsinghua University, the average household domestic hot water use in China is 50 L/household/day, approximately 25% of the average in Spain, 18.5% in the United States and 22.2% in Japan, as shown in Fig. 4.33. Based on the abovementioned usage of domestic hot water, we estimated the annual gas consumption of domestic hot water for a typical family using a gas water heater. The basic assumptions and results are shown in Table 4.10, and the annual domestic hot water consumption of a typical family is approximately 80 m3 .

11

Source Deng Guangwei. Study on the impact of usage models on the technical suitability evaluation of centralized systems [D]. Beijing University of Technology, 2013.

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Electrification of DHW

To achieve zero-carbon transformation in the building sector, it is also necessary to promote the overall electrification of domestic water heating methods in households. Existing electricity-based water heaters can be divided into two main categories: instantaneous water heaters and water heaters with heat storage. Water heaters with heat storage, on the one hand, enjoy a much lower heating power than instantaneous water heaters, with relatively fewer requirements for power distribution and a smaller impact on the power grid. On the other hand, its thermal storage capacity can also become a way of demand response in future buildings, thus promoting the flexible use of electricity in buildings. Therefore, water heaters with heat storage should be taken as the main development direction for the future. In recent years, electric heat pump water heaters (also known as air-source heat pump heaters) have gradually emerged in China’s water heater market. According to relevant market data, the total sale of heat pump water heaters in China increased from 520,000 units in 2014 to 1.23 million units in 2019, and the market size is still maintaining a rising trend. When comparing electric heat pump water heaters with ordinary electric water heaters with heat storage, we can see that electric heat pump water heaters enjoy higher energy efficiency: the thermal efficiency of electric water heaters is generally approximately 95%, while electric heat pump water heaters can generate 3 units of heat out of just 1 unit of electricity, with a thermal efficiency up to 300%. With the same water consumption, it is much more energy-efficient than normal electric water heaters. A comparison of the initial investment and operating expenses of gas water heaters, storage-type electric water heaters and electric heat pump water heaters is shown in Table 4.11. With the same amount of water used, electric water heaters are more expensive to operate than gas water heaters, but electric heat pump water heaters are less expensive to operate than gas water heaters. Even when the heat loss of the storage tank of the heat pump water heaters is considered, the annual operating cost of the heat pump water heaters is comparable to that of the gas water heater. Currently, the price of electric heat pump water heaters is significantly higher than that of normal gas or electric water heaters, but it will certainly decrease gradually as Table 4.11 Comparison of operating expenses of each type of water heater

Gas water heater

Electric water heater

Electric heat pump water heater

Annual water 50L*365 days = 18,250L consumption L Thermal efficiency (%)

90

95

300

Energy consumption

82.8 m3

784 kWh

248 kWh

376.5

119.2

Energy 248.4 expense (yuan)

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85

its market share expands in the future. From the perspective of China’s zero-carbon transition and for the purpose of energy conservation and emission reduction, electric heat pump water heaters should be vigorously promoted to achieve the electrification of supplying domestic hot water.

4.4 Electricity Use in Urban Residential Buildings 4.4.1 The Total Electricity Consumed by Urban Households With economic and social development and the improvement of living standards in urban areas, various types of electrical appliances are becoming increasingly popular in urban households, and a series of electronic information equipment and electric cookware have also emerged in recent years. The demand for air conditioning in the summer and heating in the winter have similarly greatly increased at the same time, leading to a significant increase in the total energy and total electricity consumption in urban dwellings. Echoing the significantly rising level of electrification, the share of electricity in primary energy consumption in urban residential areas increased from 64% in 2001 to 70% in 2019. In 2019, the total electricity consumed by urban households nationwide reached 537.4 TWh, more than four times the total electricity consumed in 2001, as shown in Fig. 4.34. However, in fact, the largest driving force behind the total electricity consumption of urban households is the increase in the urbanization rate. The increases in both the average and the per capita electricity consumption of urban households are actually relatively flat. From 2011 to 2009, the average and per capita electricity consumption of China’s urban residential households increased by approximately 1.5 times, as shown in Fig. 4.35. In 2019, the average electricity consumption of urban residential households in China was approximately 1.786 kWh/year, which is still low compared 60 Heating in HSCW

50

Electricity (GWh)

DHW 40

Cooking

Cooling

30

Lighting 20

Appliance

10 0 2001

2003

2005

2007

2009

2011

2013

2015

2017

2019

Fig. 4.34 Total urban residential electricity consumption in China (2001–2019)

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Energy use intensity (kgce/hh) 2000 1600 1200 800

400 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

Electricity per household

Electricity per capita

Fig. 4.35 Urban residential electricity consumption per capita and per household (2001–2019)

to the household electricity consumption in developed countries in Europe and the United States. Household appliances such as freezers, electric ovens and dishwashers, which are highly used in Europe and the United States, are currently relatively rare in China. Therefore, the overall level of electricity consumption in China is still lower than that in Europe and the United States.

4.4.2 Per Household Electricity Consumption Generally, the electricity consumption per household in China’s urban area is not high, but individual electricity consumption varies greatly. To understand the distribution of electricity consumed by individual households of urban residents in China, the statistical parameters of the annual electricity consumption distribution of urban residential users in six cities in Jiangsu Province were obtained based on the data of a random sample of 83,243 urban residential households in 2014, as shown in Fig. 4.36. The statistics show that the average annual household electricity consumption in the six cities ranges from 2200 to 2600 kWh/per household per year, and the median annual electricity consumption ranges from 1700 to 2200 kWh/per household per year. The average annual household electricity consumption of the sample is 2320 kWh/per household per year, and the median is 1900 kWh/per household per year. The following figure gives the distribution of total annual electricity consumption of urban residential buildings in six cities in Jiangsu. As seen from the distribution chart, the total annual electricity consumption of most users is in the range of 1000–3000 kWh per household per year. Low-energy users with annual electricity consumption lower than 1000 kWh per household per year account for 15– 20% of each city. High-energy users with annual electricity consumption higher than 5000 kWh/per household per year also account for approximately 5%, among

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Fig. 4.36 Parameters of total annual electricity consumed by urban residential users in six cities in Jiangsu Province (total sample size: 83,243 households)

which super high-energy users with annual electricity consumption higher than 8000 kWh/per household per year account for approximately 2%. The proportion of high energy users is also increasing significantly, partly due to the continued presence of high energy-consuming appliances in households (Fig. 4.37). Residents in the six cities in Jiangsu were divided into 10 groups by their average annual electricity consumption from lowest to highest to calculate the average electricity consumption of each group and to compare the data with the national average annual household electricity consumption of Japan, Korea, the United States and France (see Fig. 4.38). The overall electricity consumption of residential users in China is significantly lower than that of Japan, South Korea, France and the United States. However, for the top 10% of electricity users in China (group 10), their average household electricity consumption has exceeded the average electricity consumption levels of Japan, Korea and France. With the development of China’s economy and society and people’s aspiration for a better life, the electricity consumption of urban residents will further increase. However, those high energy consumption users, which account for a significantly higher proportion than other households, should not represent the development path in the future of China’s urban residential buildings. However, to pursue the development concept of ecological civilization, maintaining a green lifestyle to realize the low-carbon and sustainable development goal in China’s urban households should be taken as the future direction of China.

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a) Nanjing

b) Wuxi

c) Lianyungang

d) Nantong

e) Taizhou

f) Xuzhou

Fig. 4.37 Cumulative distribution chart of total annual electricity consumed by urban residential users in six cities in Jiangsu Province

4.4.3 Difference in Lifestyle The main reason for the difference in electricity consumption between different households is the difference in lifestyle The reasons that lead to the high electricity consumption include the various using behavior of different types of household appliances, long standby time of appliances, and different ways of using air conditioner and heating devices. There are many kinds of household appliances, and the use behavior of owners varies as well. As people’s living standards have been improving, new types of household appliances continue to emerge in urban households, which is also accompanied by new lifestyle changes. Apart from essential appliances such as television, refrigerators, air conditioners and washing machines, the ownership of some highly

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Fig. 4.38 Comparison of average annual household electricity consumption in each percentile group of residential buildings in six cities in Jiangsu with average annual household electricity consumption in other countries12

energy-consuming appliances is also gradually increasing, such as freezers, dishwashers, sterilized cupboards, drying machines, water dispensers, and smart toilet seats. These new appliances are the reasons for different power usage behaviors and have a significant impact on electricity consumption in urban residential housing. To explore the reason for electricity consumption differences among various households, two typical families were selected to represent households with high power consumption and households with low power consumption. The electric power of appliances and the lifestyle of the two households were surveyed. The results show that the family with high electricity consumption, which was located in Changsha, Hunan Province, consumed 6995 kWh of electricity in 2019. The family with low power consumption was from Beijing, and they had consumed 999 kWh of electricity in 2019. The basic information of the two households is shown in Table 4.12. We collected data on electric appliances’ power consumption and surveyed the lifestyles of the two families. Figure 4.39 the annual electricity consumption of different appliances in these two families. 12 Source of data on the number of residential users in the United States: U.S. Energy Information Administration, electricity data [DB/OL]. https://www.eia.gov/electricity/data/browser/#/topic/56? Agg=0,1&geo=g&endsec=VG&freq=M&start=200101&end=202011&ctype=linechart<ype= pin&rtype=s&pin=&rse=0&maptypE=0. Source of data on the number of residential users in Japan: Statistics Bureau of Japan, Statistical Handbook of Japan 2020 [M/OL]. https://www.stat.go.jp/english/data/handbook/c0117.html. Source of data on the number of residential users in France: European Commission, Eurostat [DB/OL]. https://ec.europa.eu/eurostat/databrowser/view/lfst_hhnhwhtc/default/table?lang=en. Source of data on the number of residential users in South Korea: Statistics Korea, 2017 Population and Housing Census [M/OL]. http://kostat.go.kr/portal/eng/pressReleases/8/7/index.board? bmode=read&bSeq=&aSeq=370993&pageNo=1&rowNu.

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Table 4.12 Basic information of the selected families Family A

Family B

Annual energy consumption (kWh)

6995

999

Family location

Changsha, Hunan province Beijing

Building floor area (m2 )

100

160

Family members

2 middle age adults + 1 student

2 middle age adults + 1 student

Frequently used appliances Air con Split air conditioner*3 Heating Electric heater

Split air conditioner *3 District heating

DHW

Gas water heater + small electric water heating device

Gas water heater + centralized domestic hot water supply

Others

Refrigerator, washing machine, projector, stereo, treadmill, smart toilet seat, sweeping robot, range hood, electric cooker, etc.

Refrigerator, washing machine, television, stereo, range hood, electric cooker, electric kettle, etc.

Fig. 4.39 Electricity consumed by key appliances in family A and family B (kWh)

By comparing the two families, it can be found that air conditioners consumed 745 kWh of electricity per annum in family A, which is the largest energy consumer among all appliances in this family. In family B in Beijing, air conditioners consumed only 100 kWh a year. In addition to the issue of climate differences in different regions, one of the key contributors to power use differences is the use habits of air conditioners in different families. There were two air conditioners in the two living rooms of family A, and they were used from June to September, while the air conditioner was not used in family B until the hot weather was unbearable for several weeks in July. In addition, family A was in Changsha city of Hunan Province

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without a district heating system. Therefore, the electric heater used in family A had an annual electricity consumption of 430 kWh. Aside from air conditioning, there are also several other appliances in family A that consumed more electricity than other families, such as small electric water heating devices, projectors, electric cookers and smart toilet seats. The long stand-by time of these devices all led to a great waste of energy. Among all the appliances, the small electric water heating device consumed the highest amount of electricity. The purpose of this device is to heat the water when washing hands and vegetables. The DHW in family A was produced by a gas water heater and a 10 L small electric water heating device. The total monthly power consumption was 20 kWh in summer and 60 kWh in winter, and its annual power consumption for family A was 518 kWh, which was even higher than their annual electricity consumption for heating. In addition, family A also has other high energy-consumption appliances, such as projectors, electric cookers and smart toilet seats. Each of these appliances uses at least 200 kWh every year, which is similar to the energy consumption of a refrigerator. The following passages discuss the use behavior of several high energy consumption appliances. The combined electricity consumption of the projector and stereo in family A was 481 kWh, which was similar to TV. The projector was used for 3–5 h per day at 300 W operational power and consumed 1.3 kWh of electricity per day. The average standby power for the projector was 1.3 W, so it can be calculated that the annual electricity consumption during standby was 11.4 kWh. The total annual electricity consumption of TV in family B was 63 kWh, which was based on 256 W of operational power and 40 min of operation time on average per day. Therefore, the main reason that the projector consumed a larger amount of electricity is its higher frequency and longer use time. The electric cooker in family A also consumed a large amount of power of 385 kWh per year, which was 11 times higher than family B’s electric cooker. A 4 L electric cooker for a family of three people usually consumes 0.189 kWh of power for one meal, and the annual electricity consumption would be 140 kWh if the electric cooker is used twice a day. According to our test, family A not only used an electric cooker for normal meals but also preset the cooker for three hours from 3 to 6 am to cook porridge every day; each time, the cooker consumed 0.68 kWh of power (as shown in Fig. 4.40). The standby power of the electric cooker is 7.2 W, so the total standby power consumption of the electric cooker would be 50 kWh per year. Therefore, the difference in electricity consumption of the same household appliance could be as high as 10 times. Smart toilet seat was another high energy consumption appliance in family A, which consumed 241 kWh a year, equivalent to refrigerators in the average families. As demonstrated in Fig. 4.41, there are two scenarios that consume electricity. In the first scenario, electricity is used to heat the water instantly during cleaning, the heating power is approximately 1300–1600 W, and the cleaning cycle is approximately one minute. In the second scenario, electricity is used for heating to keep the seat warm during the winter season. The heating power is between 35 and 40 W during standby

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Fig. 4.40 Daily power curve of electric cooker in family A (W)

Fig. 4.41 Daily power curve of smart toilet seat (W)

mode, and the average daily electricity consumption during this scenario is approximately 0.84–0.96 kWh. On a typical day, there was 1.03 kWh of power consumed by the smart toilet seat, of which 0.864 kWh of power was used to maintain the temperature of the seat, accounting for 84% of the total power consumption, and 0.166 kWh was used for water heating, accounting for 16% of the total. Apart from the above appliances, the annual electricity consumption of the treadmill, stereo and Wi-Fi routers of family A could not be ignored and were 111, 94 and 87 kWh, respectively. The Wifi router operates 24 h a day, and its average operation power was 9.9 W. Treadmill and stereo were used almost every day, and they consumed power even during the standby period. The standby power of the treadmill was 4.2 W, and the annual electricity consumption was 34 kWh, which was 30% of the total electricity that the treadmill consumes. The standby power of stereo was 1.8 W, and its annual electricity consumption was 16 kWh, accounting for 17% of the total. Based on our analysis, we conclude that in addition to the different use behaviors towards heating devices and air conditioners, the high electricity consumption of household appliances was attributable to three main reasons. First, the long standby time and repeat heating cycle of heating appliances, small electric water heating devices, water dispensers and smart toilet seats, which could consume large amounts of electricity each year, cannot be underestimated. Second, even though high energy

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93

consumption appliances such as electric dryers, dish washers, electric dish sterilizers, electric wine cabinets, and electric ovens have not been very prevalent in urban households, energy efficiency policies need to be promulgated to lower the power consumption for these devices. Third, power consumption during the standby period, such as washing machines, TVs, etc. In family A, when appliances such as projectors, electric cookers, treadmills and stereos were not operating, they were usually in standby mode, which consumed 111 kWh of electricity in a year. Standard power consumption was not unacceptable for individual appliances, but the accumulation of a small amount of standby electricity for all appliances is something we cannot ignore. These new kinds of appliances can be seen in an increasing number of Chinese households, which is one of the key reasons for the increasing electricity consumption in China. We should attach special focus on the following three types of appliances that consume high power. The detailed electricity consumption and energy efficiency potential analysis can be seen as follows: 1.

Appliances that require continuous heating

Applications such as electric water heaters, small electric water heating devices, smart toilet seats, etc., which are operated in constant heating mode to maintain the water temperature or surface temperature, could also consume a large amount of electricity for heating. The purpose of constant heating is to ensure that the appliance can meet urgent hot water demand in households. According to our research, the “effective” power use for water heating only took a small share of the total amount, and the majority of the power was used to maintain the temperature of the water tank to offset the heat loss. Therefore, it can be regarded as “ineffective” power. There are two types of appliances that require continuous heating. The first type of appliance is equipped with a water tank, such as an electric water heater, small electric water heating device, and water cooler. These appliances operate on a constant heating cycle to maintain the temperature of the water tank and stop heating when the set temperature is met. Figure 4.42 shows the power curve of the water cooler during the 2-h standby period. The water tank of the water dispenser was heated every Fig. 4.42 Power curve of the water dispenser for 2 h in a real situation (W)

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20 min to sustain the temperature, which consumed 0.015 kWh of power. Based on our calculation, the average ineffective power use of the water dispenser was 46 W, which means that its daily standby electricity consumption was 0.97 kWh, higher than the daily power consumption of a refrigerator in an average household. The high electricity consumption of these appliances is mainly caused by poor insulation of the water tank. Therefore, we can conserve more electricity by improving the insulation performance of the tank. Additionally, one of the most popular water heating devices in the market today is the tankless water heater. It would only take approximately less than a minute to heat up the water, which is a healthier way to meet hot water demand in households while conserving almost 1 kWh/day of power. The second type of appliance is tankless without insulation. Appliances such as smart toilet seats need to maintain the temperature of the seat at all times, and thermal insulation is unable to offset the heat radiation from the seat. Currently, smart toilet seats on the market are mainly equipped with instantaneous water heating functions due to hygiene, safety and energy efficiency requirements. The power of the electric water heater is approximately 1600 W, the power of heating the seat is between 40 and 50 W, and the power of the electric dryer is 340 W. Based on the use behavior on the electric toilet seat of family A, the total electricity consumption should be approximately 0.84–0.96 kWh to achieve 24 h of constant heating of the seat, which is 84% of the total power use, higher than that of the refrigerator. Smart control technology would be useful to reduce the high electricity consumption of these kinds of appliances. Meanwhile, some of the smart toilet seats are equipped with timers, which can be automatically turned on or off according to the user’s habits. It can stop heating when no one is at home during the day and turn it on again when occupants need to use it again to lower the ineffective electricity consumption for heating. 2.

Unnecessary high energy consumption appliances

As society and the economy continue to develop and people’s livelihoods have improved in recent years, the number of appliances and their energy consumption are increasing. Conventional household appliances have recently enjoyed steady sales volumes, while the sales of unconventional appliances are rocketing. For example, sales for kitchen appliances such as microwave ovens, induction cookers, and electric cookers are plateauing, while new appliances such as electric ovens and dishwashers have enjoyed fast growth of sales in the last five years (Fig. 4.43). Among all household appliances, vacuum machines, water purifiers and air purifiers are enjoying steady growth, while sales for smart toilet seats and floor cleaning robots have surged significantly (Fig. 4.44). Among all the newly added appliances, dishwashers, smart toilet seats, wine cabinets, and washing machines with hot water functions are all high-energy appliances in households. Recently, the sales volume of washing machines has increased rapidly. The operation cycle of the washing machine can be divided into heating and cleaning, disinfection and drying cycles. The operation duration of each cycle was between 60 and 100 min. The disinfection temperature of most of the washing machines available on the market is approximately 70–80 °C, followed by high-temperature blow drying

4.4 Electricity Use in Urban Residential Buildings

95

Sales index 200 150 100 50

0 2013

2014

2015

Microwave oven Electric oven

2016

2017

Induction cooker Dishwasher

2018

2019

Rice cooker

Fig. 4.43 Sales volume of China’ kitchen appliances

Sales index 400 350 300 250

200 150 100 50

0 2013

2014

Air purifier Smart toilet seat

2015

2016

2017

Water purifier Floor mopping robot

2018

2019

Vacuum machine

Fig. 4.44 Sales volume of China’s household appliances. Note Microwave oven and dishwasher sales were 100 units in 2014, induction cooker, the sales volume of electric cooker and electric oven were 100 units in 2013. The sales volumes of the air purifier and water purifier were 100 units in 2014. The sales volumes of vacuum machines, smart toilet seats and floor cleaning machines were 100 units in 2013. Source Industry online.

of the dishes. Therefore, the standard operation cycle of a washing machine would consume 0.64–1.6 kWh of power and 300–500 kWh of power in a year, which puts the washing machine in the high energy consumption appliance category. The wine cabinet operates similarly to the refrigerator in a way that it also leverages a compressor to control the temperature and humidity of the atmosphere within the cabinet. Normally, the maximum and minimum temperatures of wine cabinets are 4–22 °C. The amount of energy consumed is in tandem with the volume of the cabinet itself. Under normal circumstances, a wine cabinet would be able to contain 30–150

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bottles of wine, which would consume 0.3–0.8 kWh of power per day. For a larger wine cabinet, its electricity consumption is similar to that of a refrigerator. The power consumption of a washing machine with a water heating function is notably higher than that of a normal machine. As demonstrated in Fig. 4.45, the washing cycle of a washing machine with a water heating function can be divided into three main steps, i.e., heating, washing and spin-drying. The total electricity consumption for a single washing cycle is 0.131 kWh. During the 200 s of water heating, the power consumption reaches 1900 W, consuming 0.112 kWh of power, which is equivalent to 85% of the electricity consumption of a single washing cycle. As a result, the electricity consumption of a washing machine with a water heating function is five times higher than that of a normal machine. Temperature adjustment is a commonplace function in all kinds of washing machines, and a low/normal temperature washing cycle conserves electricity for the washing machine. 3.

Appliances with long standby cycles

For example, the yearly electricity consumption of appliances such as projectors, electric cookers, and treadmills during a long standby cycle in family A could be 111 kWh. Apart from refrigerators and WiFi routers, which are switched on at all times in households, there are other appliances with long standby cycles, such as TV, PC, air conditioners, washing machines and electric water heaters. The standardized standby power of these kinds of appliances is between 0.5 and 5 W, with 4–40 kWh of power consumption per year per single appliance. From the previous analysis, it can be concluded that there are several main reasons contributing to the high electricity consumption of urban households in China. We need to pay special attention to the power consumption of household appliances with a constant heating function. Policies need to be promulgated to enhance the energy efficiency of these appliances. Smart control technologies need to be introduced to

Fig. 4.45 Power curve of a single washing cycle of a washing machine (W)

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avoid unnecessary reheating and heat loss. A green and energy-saving lifestyle needs to be promoted among users to reduce the waste of energy from using these types of appliances. Policy subsidies shall not be given to those that may lead to a drastic shift in lifestyle, such as dryers and other kinds of household appliances, to avoid the surge of sales, which otherwise will lead to a huge waste of electricity. Energy efficient technologies of all kinds shall be introduced to upgrade appliances with long standby cycles to ensure that the device can be switched to an energy saving mode during off time to reduce power use. An energy-saving lifestyle should be promoted among the populace to remind people to turn off appliances when unnecessary.

4.4.4 The Future of Electricity Consumption in Urban Residential Housing Chinese people have been exercising frugality since time immemorial. Small and medium-sized apartment buildings have always been the main type of residential building in China due to land resource limitations, and the Chinese people usually try to refrain from leaving appliances in a standby mode to reduce the waste of energy. Under the current economic environment in China, the Chinese people are able to afford an American lifestyle with enough discretionary income in their pocket. However, the majority of Chinese households are maintaining the traditional way of life with low energy consumption, even though they have earned more money. Therefore, it can be concluded that energy consumption improvement is not limited by the level of their income but a traditional way of life and behavior inherited from the past. From the previous analysis of electricity consumption of urban households, we found that there is still room for energy efficiency improvement and energy consumption reduction for all kinds of new appliances, especially for appliances with a standby mode, such as water dispensers, electric toilet seats, set-top boxes and other low-power appliances. Together with the amount of power consumption during its standby cycle, some of these appliances consumed similar amounts of electricity as refrigerators and other necessary devices at home. It remains an important task to introduce energy efficient standards targeting these kinds of appliances, as well as new technologies, energy saving modes and smart control mechanisms to lower electricity consumption during its standby cycle. On the other hand, subsidizing policies shall not cover these high-energy appliances. Instead, green lifestyle and energy saving behaviour should be promoted among the general public to avoid the surge of electricity consumption after the virality of these appliances. In fact, based on the improving living standard of urban households and the electrification of cooking, heating and DHW supply, the annual electricity consumption of urban households in the future would be 3600–4200 kWh, which is enough for a happy life in China. According to our study, 3600 kWh/(hh a) of annual

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power consumption is sufficient to support a family of three with high living standards in a 100 µm house with full electrified appliances, as shown in Table 4.13. While the real-world data in the third column in Table 4.13 came from a certain Table 4.13 Electricity consumption of urban households Electricity consumption

Family of three (kWh)

Real-world data (kWh)

Family situation

2250

Family with five people

Annual electricity consumption Family without heating 3600 Family with heating

4200

Category Air conditioner

700

110

Beijing family, 3 air-cons, part time part space

Electrification of HSCW regions

800

400

Average 3–5 kWhe /m2 in HSCW region

Electrification of DHW 600

710

Beijing family, five people, consumed 710 kWh of power, which was equivalent to 426 kWh of power consumption for a family of three

Electrification of cooking

114 m3 natural gas

Beijing family Beijing family

600

Lighting

300

427

Electric appliances

1400

1003

Refrigerator

200

130

2 TVs

300

263

PC and entertainment facility

300

300

2 PCs

Electric cooker

160

70

Level on energy efficiency standard

Kitchen ventilation device + fan

40

20

Microwave and other electric cooking devices

100

73

Washing machine

200

90

Water dispenser or electric water heater

100

57

200L, level one energy efficiency standard

Drum type, with level on energy efficiency standard

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professor’s family at Tsinghua University, the average electricity consumption was merely 2250 kWh/(hh a), lower than the target. The annual electricity consumption would be 4200 kWh if we include an additional 800 kWh/(hh a) of electric heat pump in HSCW regions, which was a calculation from doubling the 4 kWh/m2 average in the same year. Therefore, 3900 kWh/(hh a) of average power consumption can fully support all Chinese urban households to lead a relatively high standard of life. Given that electrification will be the future of urban household development in China, in which DHW supply and cooking will be handled through electricity use, 1 billion urban residents, or 380 million urban households in the future, will require only 1500 TWh of power to support urban residential buildings for its energy demand. To realize low-carbon and sustainable development for urban households, we need to have a firm grasp on the status quo and its characteristics. The main tasks should be: 1.

2.

3.

4.

5.

6.

Scope control: Reasonably plan the amount of floor area of residential housing and control the per unit area of each household. The per capita floor area and the aggregate urban residential building floor area should be contained within 35 m2 and 35–36 billion m2 , respectively. Change of lifestyle: To promote and maintain green lifestyle and the principle of frugality. Promote “part time, part space” to avoid “full time, full space” due to the limit of building types, energy systems and service modes. To promote electrification for cooking, DHW supply and heating in HSCW regions. The goal of zero-carbon emissions can be achieved when there is full electrification in urban households, and renewables are the mainstay for our power grid. To find a comfortable lifestyle based on the building type and renew our effort to promote residential buildings with windows and allow natural ventilation. A large area centralized system for heating, air conditioning and DHW should be avoided in HSCW regions. The existing decentralized system should be promoted while improving its terminal flexibility, adjustability and energy efficiency to avoid electricity spikes while improving service levels. For household appliances, the key task is to improve energy efficiency while improving manufacturing standards for appliances with long heating and standby cycles, such as small electric water devices, smart toilet seats, water coolers and other high-energy appliances. For instance, we could enhance the controllability of the set-top boxes and improve the insulation capacity of water coolers to avoid wasting energy. Policy subsidies and promotion plans shall not cover appliances such as drying machines, which may result in significant changes in lifestyle, and we should be aware of the energy spikes of these high-energy appliances. Policy mechanism and measures: Further improve and implement energy efficient policy standards and mechanisms, such as Standard for energy consumption of building, multistep electricity price, minimum energy efficiency standard for all types of appliances, labeling system for energy efficient appliances, etc. A market-oriented approach should be adopted to guide the general public towards

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an energy-saving lifestyle and improve their behaviour to conserve energy to ensure that energy efficiency could be a widespread concept among all people.

4.5 Multi-split Air Conditioning Systems in Urban Residential Areas 4.5.1 The Use of Multi-Split Air Conditioning Systems in Urban Residential Areas Electricity consumption for cooling in urban residential buildings accounts for 21% of urban residential electricity consumption, and it is increasing rapidly. From 2000 to 2017, electricity consumption for urban residential cooling increased approximately tenfold and is of increasing concern to society (as shown in Fig. 4.46). Among them, variable refrigerant multi-split air conditioning systems (multi-split systems) are increasingly used in actual projects due to their flexibility, controllability, subdivisional metering and good part-load performance. As shown in Fig. 4.47, it has become an important form of air conditioning system in urban residential buildings. The ownership of multi-split systems has continued to grow in recent years, so there is a need to have a deeper understanding of the current use of multi-split systems in urban dwellings. For that purpose, this report employed big data on the operation of multi-split systems from the Survey and Study Report on the actual operation conditions for air conditioning products in China to statistically analyze the operation data of multi-split systems used in cold zones, hot summer cold winter zones, and hot summer warm winter zones from June to October 2019 to calculate

Fig. 4.46 Residential cooling energy consumption in urban areas of China, 2000–2017

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Fig. 4.47 Statistics on the form of air-conditioning systems in residential buildings in China, 2015

and obtain information on the energy consumption intensity as well as the usage patterns of such systems. Based on the operational data from June to October 2019, calculations were made to obtain the energy consumption intensity of multi-split air conditioning systems in different climate zones. By comparing the data from the three climate zones, it can be seen that the electricity consumption per square meter in cold zone and hot summer cold winter zone is close to each other, and the average electricity consumption per square meter for cooling in hot summer warm winter zone is the highest, which is 2.2 times higher than the first two zones (Table 4.14). Users of multi-split systems in urban residential buildings tend to switch on the units in their own individual rooms rather than the entire system. According to the operating statistics of 325 multi-split systems, the simultaneous working hours of the indoor units are given in Fig. 4.48. It can be seen that 87% of the total working hours see no more than 2 indoor units switched on simultaneously, of which 61% of the working hours see only 1 indoor unit switched on. Only 0.4% of the working hours see 5 indoor units switched on simultaneously. The results are due to the “part-time, partspace” (use only when it is necessary) use habits of the residents. It is rather rare to see all indoor units in all rooms switched on at the same time. The usage pattern of “part-time, part space” makes the systems run at low loads for long periods of time, which can lead to reduced system energy efficiency. Table 4.14 Statistical indicators of electricity consumption per square meter for cooling in the three climate zones in 2019

Electricity consumption for cooling (kWh/m2 ), June–October 2019

Average value

Cold zone

Hot summer cold Hot summer winter zone warm winter zone

5.49

6.83

14.75

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Fig. 4.48 Histogram and statistical pie chart of the simultaneously working hours

4.5.2 Comparison of Multi-split and Split Air Conditioning in Urban Residential Buildings For the air conditioning of urban dwellings, most residents currently use traditional split air conditioning for cooling in summer. This section will compare multi-split systems with traditional split air conditioning in terms of energy consumption, residents and economy. Table 4.15 provides a comprehensive comparison of multi-split systems with split air conditioning: From the perspective of energy consumption, the electricity consumption per square meter of air conditioning in the cooling season is higher for multi-split systems than for split air conditioning. In terms of user usage behavior, both systems see a “part-time part space” usage mode (Fig. 4.49). According to the data analysis, it was found that for multi-split systems, only 1–2 indoor units will be switched on for 87% of the total working hours, and as multi-split systems for residential buildings are to meet the cooling needs of 4–5 indoor units by 1 outdoor unit, they run at low loads for a rather long time. Studies have shown that when the load rate is below 20–30%, the COP of the systems will be significantly reduced, and the cooling energy efficiency is only 1.74.13 Split air conditioning systems, on the other hand, supply the cooling needs of 1 indoor unit with 1 outdoor unit. The users’ “part-time, part space” mode does not affect the cooling load rate of such a single split air conditioner, so it can run efficiently. From the perspective of energy efficiency control, multi-split systems have many control links, and the actual operational energy efficiency of the system is always subject to the design and installation of refrigerant piping and the capacity of the system. All this makes it more difficult to control the energy efficiency of multi-split systems, while traditional split air conditioners are proven to enjoy easy-to-control

13

Won A, Ichikawa T, Yoshida S, et al. Study on Running Performance of a Split-type Air Conditioning System Installed in the National University Campus in Japan [J]. Journal of Asian Architecture & Building Engineering, 2009, 8(2):579–583.

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Table 4.15 A comprehensive comparison table of multi-split systems and split air conditioning Comparison content Energy consumption

From the resident’s perspective

From the economic perspective

Multi-split systems

Traditional split air conditioning

Electricity consumption in cooling season

5.5–14.8 kWh/m2

2.3–6.3 kWh/m2

Difficulty level of controlling the energy efficiency of the systems

Difficult (many control links; complex refrigerant piping; capacity design affects the system’s energy efficiency)

Simple (few control links; simple refrigerant piping; only the quality of the equipment needs to be controlled)

User usage mode

Indoor units can be switched on and off and adjusted individually; “part-time and part space” mode

Indoor units can be switched on and off and adjusted individually; “part-time and part space” mode

Outdoor unit

Single outdoor unit

Multiple outdoor units

Indoor noise

Some fan coils are pretty noisy

No noise

Outdoor noise

Pretty noisy outside

Pretty noisy outside

Initial investment

Large initial investment Small initial (installation of investment refrigerant line)

Operating expense

Low operation expense Low operation expense (only electricity bill) (only electricity bill)

Fig. 4.49 Air-conditioning usage modes in urban residential buildings in China. The future of cooling in China, 2015

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energy efficiency because they have fewer control links and simple refrigerant piping, with the quality of the equipment being the only concern. From the residents’ point of view, the initial purpose of installing a multi-split unit is to beautify the outer appearance of the building, and a single outdoor unit of a multi-split system has less impact on the appearance of the building than those multiple units of a traditional split air conditioning system. However, these days, sufficient space is reserved for the outdoor unit of each room during the design phase of the building, and the space thus reserved goes very well into the design of the building; therefore, the multiple outdoor units of traditional split air conditioners have no adverse impact on the appearance of the building. Judging from an economic angle, both multi-split systems and split air conditioning systems incur electricity fees during the operation phase. However, at the initial investment phase, multi-split systems require the installation of a more complex refrigerant pipeline, so the initial investment in the system is higher than that for traditional split air conditioning. Therefore, for urban residents who are accustomed to the “part-time, part-space” mode of air conditioning usage, a split air conditioning system is more favorable because its energy efficiency is easier to control, and the air conditioning outdoor unit has been well integrated into the building architectural design. Traditional multi-split systems are more suitable for small office buildings where all indoor units need to be switched on at the same time during working hours. However, for multi-split systems used in urban residential buildings, it is necessary to optimize the efficiency of the part-load operations under the “part-time, part-space” mode. For example, solutions such as the design of a double-cylinder compressor with variable capacity and optimization of the ordinance rate of multi-split system outdoor units should be considered.