WONDERS OF SOLAR: Solar PV Guide: Design, Installation & Maintenance

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Solar PV Handbook Design, Installation & Maintenance

About Book This book presents the explanation of the theory and design of PV solar cells and systems. It is written to address several audiences: engineers, technicians, students who desire an introduction to the field of photovoltaic, students interested in PV science and technology, and end users who require a greater understanding of theory to supplement their applications. The book is effectively sectioned into five main blocks: section 1-5. Section-1 is a general introduction to the field, covers the basic elements of photovoltaic the individual electricity producing cell. The reader is told how PV cells work. Section-2 cover the designs of the PV system. It includes the sample system design considering the losses involved in the system. Section 3-4 cover the installation and maintenance guidelines for the PV system. In addition, chapter 5 have some MCQs. SECTION-1................. INTRODUCTION 1.1 What is solar energy? 1.2 Why to choose solar energy? 1.3 Types of solar energy 1.4 Advantages and disadvantages of solar panel 1.5 Solar photo voltaic (SPV) module 1.6 Solar panel 1.7 Main components of solar photo voltaic system 1.8 Types of solar cell 1.9 Factors affecting output SECTION-2..................DESIGNING OF SOLAR PHOTOVOLTAIC SYSTEM 2.1 Definitions 2.2 Primary phases of designing an SPV system 2.3 Sample system design SECTION-3.....................INSTALLATION OF SOLAR PANEL 3.1 Introduction 3.2 Testing before installation 3.3 Installation guidelines SECTION-4......................MAINTENANCE & TROUBLESHOOTING 4.1 Maintenance 4.2 Troubleshooting

SECTION-5......................... MCQ

SECTION-1 INTRODUCTION 1.1 What is solar energy? The energy coming out from the 'Sun' is known as 'Solar Energy'. Every day the sun radiates an enormous amount of energy in the form of heat and light. Where does all this energy come from? It comes within the sun itself. Like other stars, the sun is a big gas ball made up mostly of hydrogen and helium. The sun generates energy in its core in a process called nuclear fusion. During nuclear fusion, the sun's extremely high pressure and hot temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy. It takes millions of years for the energy in the sun's core to make its way to the solar surface, and then just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,282 miles per second, the speed of light. Only a small portion of the energy radiated by the sun into space strikes the earth, one part in two billion. Where does all this energy go? About 15 percent of the sun's energy that hits the earth is reflected back into space. Another 30 percent is used to evaporate water, which, lifted into the atmosphere, produces rain-fall. Solar energy also is absorbed by plants, the land, and the oceans. The rest could be used to supply our energy needs. Energy can be harnessed directly from the sun, even in cloudy weather. Solar energy is used worldwide and is increasingly popular for generating electricity or heating and desalinating water. 1.2 Why to choose solar energy? Solar Energy is available in abundant. It is the prototype of an environmental friendly energy source. It consumes none of our precious energy resources(oil, gas etc), makes no contribution to air, water, or noise pollution, does not pose a health hazard, and contributes no harmful waste products to the environment.

There are other advantages too. Solar energy cannot be embargoed or controlled by any one nation. And it will not run out until the sun goes out. The sun releases energy at a mass–energy conversion rate of 4.26 million metric tons per second, which produces the equivalent of 384.6 septillion watts (3.846×1026 W). To put that in perspective, this is the equivalent of about 9.192×1010 megatons of TNT per second, or 1,820,000,000 Tsar Bombs – the most powerful thermonuclear bomb ever built!

Some facts of the sun Mean distance from the Earth: 149,600,000 km (the astronomic unit, AU) Diameter: 13,92,000 km (109 times that of the Earth) Volume: 13,00,000 times that of the Earth Mass: 1.993 x 1027 kg (3,32,000 times that of the Earth) Density (at its center): >105 kg /m3 (over 100 times that of water) Pressure (at its center): over 1 billion atmospheres Temperature (at its center): about 1,50,00,000 K Temperature (at the surface): 6,000 K Energy radiation: 3.8 x 1026 W The earth receives: 1.7 x 1018 W 1.3 Types of solar energy: Basically the solar energy can be harnessed by two methods which are explained below:

i) PV system: This is the technology in which the pv(photo-voltaic) cells are utilized to convert the solar energy directly into electricity. When the sun shines onto a solar panel, photons from the sunlight are absorbed by the cells in the panel, which creates an electric field across the layers and causes electricity to flow. ii) CSP system: The second technology is concentrating solar power, or CSP. It is used primarily in very large power plants and is not appropriate for residential use. This technology uses mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat, which can then be used to produce electricity. In this book we are going to discuss about the solar pv systems throughout.

1.3.1 Solar PV(photovoltaic) technology: Photovoltaic comes from the words photo meaning "light" and volt, a measurement of "electricity". Sometimes photovoltaic cells are called PV cells or solar cells for short. You are probably already familiar with solar cells. Solar-powered calculators, toys, and telephone call boxes all, use solar cells to convert light into electricity. A photovoltaic cell is made of two thin slices of silicon sandwiched together and attached to metal wires. The top slice of silicon, called the N-layer, is very thin and has a chemical added to it that provides the layer with an excess of free electrons. The bottom slice, or P-layer, is much thicker and has a chemical added to it so that it has very few free electrons. When the two layers are placed together, an interesting thing happens-an electric field is produced that prevents the electrons from traveling from the top layer to the bottom layer. This one-way junction with its electric field becomes the central part of the PV cell. When the PV cell is exposed to sunlight, bundles of light energy known as photons can knock some of the electrons from the bottom P-layer out of their orbits through the electric field set up at the P-N junction and into the Nlayer. The N-layer, with its abundance of electrons, develops an excess of negatively charged electrons. This excess of electrons produces an electric force to push the additional electrons away. These excess electrons are pushed into the metal wire back to the bottom P-layer, which has lost some of its electrons. This electrical current will continue flowing as long as radiant energy in the form of light strikes the cell and the pathway, or circuit, remains closed. 1.4 Advantages and disadvantages of solar panel Advantages Fuel source for solar panel is direct and endless so no external fuels required. Sunlight - free of cost. Unlimited life of solar modules, fast response and high reliability. Can operate under high temperature and in open. Inherently short circuit protected and safe under any load

condition. Pollution free. Minimum maintenance Independent working Operation is simple and no electrochemical reaction and no liquid medium. Noise free as there are no moving parts. No AC to DC conversion losses as DC is produced directly. No transmission losses as installed in the vicinity of the load. Suitable for remote, isolated and hilly places. Suitable for moving loads/objects. Since it is in modular form, provision of future expansion of capacity is available. It can generate powers from milli-watts to several mega watts. It can be used almost everywhere from small electronic device to large scale MW power generation station. It can be installed and mounted easily with minimum cost. Disadvantages Initial cost is high Dependent on sunlight Additional cost for storage battery. Climatic condition, location, latitude, longitude, altitude, tilt angle, ageing, dent, bird dropping, etc. affect the output. It has no self-storage capacity. Manufacturing is very complicated process. 1.5 Solar photo voltaic (SPV) module The power generated by a single cell is small and therefore several cells are interconnected in series/parallel combination to get the required voltage and current. When a number of solar cells are connected in series to get a specific voltage the unit so formed is called as solar module. Charging batteries is the primary use of SPV module. Therefore normally 36 cells are joined in series to form a standard module, which is capable of charging 12 volts battery. A terminal box is provided on the backside of the module for external connections. A bypass diode is connected across +ve and –ve in the terminal

box. Cathode of the diode will be at +ve terminal and anode will be at –ve terminal of the module.

This diode protects the module cells from overheating due to shadowing of the module or any cell breakage, generally the rating of bypass diode is 1.5 times of the maximum current of module. The repetitive reverse peak voltage Vrrm of the diode should be double the string open voltage. 1.6 Solar panel A solar panel consists of a number of solar modules, which are connected in series and parallel configuration to provide specific voltage and current to charge a battery. A diode is connected on the +ve terminal of such string in forward bias. This is called blocking diode. This diode is provided so that in daytime current can flow from module to battery, but at night or in cloudy day current should not flow back from battery to module or from one string to another string drawing shown in figure below illustrates a solar panel.

1.7 Main components of solar photo voltaic system The solar power system consists of the following components: i) Solar array. ii) Battery Bank. iii) Solar Charge Controller. iv) Inverter. v) Field Junction Box. vi) Solar Module Mounting Structure. vii) Earthing kit. viii) Cables. 1.7.1 Solar array Solar array consists of series/parallel combination of modules, which are mounted on the metallic structure in sunny and shadow free area at a fixed angle as recommended by designer. Cables from the array area will come to the control and battery room through junction boxes from panels of modules. Solar panels should always face true south if you are in the northern hemisphere, or true north if you are in the southern hemisphere. True north is not the same as magnetic north. If you are using a compass to orient your

panels, you need to correct for the difference, which varies from place to place.

1.7.2 Battery bank The battery bank is one of the most complicated and costly components of any off-grid power system. Your battery storage needs to be large enough to supply power year-round. Nothing is more frustrating than suffering a power outage because your battery bank doesn’t store enough charge. On the other hand, too much battery capacity means your system won’t be able to fully recharge. If your battery bank is too large, your batteries can’t get the full charge, which can ruin the batteries. Dialing in on the right battery bank is an important step to designing your off-grid system. A battery bank can be composed of a single battery, or multiple interconnected batteries that are wired to work as one large battery at a certain voltage and amp-hour capacity. The Sun is not always available and it is not regular. However, loads are to be fed any time of the day. Therefore power should be stored in a battery bank. The capacity of this battery bank is given in Ampere-Hour (AH) and bus bar voltage. The bus-bar voltage is decided by the voltage requirement of the load. There are mainly two type of solar battery. If you are installing a solar system with solar battery than you should know about its type and models. It is also important for their evaluation purpose. Let’s have a look over the

types of solar battery. i) Tall tubular solar battery ii) Lithium-ion solar battery When it comes to evaluating solar battery than you should compare some of their specifications such as their technology, solar brand, life cycle, and maintenance etc. Here is mentioned everything about the criteria you should use to compare energy storage options, as well as different types of solar batteries. Tall tubular solar battery Lead acid tall tubular solar battery is the upgraded version of normal batteries that used at home and other places. These solar battery is specially designed as per solar application requirement. Solar tubular batteries are fully tested and reliable solar batteries that has been used in off grid solar system, hybrid solar system, solar home lighting system and solar street lights since decades. A lead acid tall tubular solar battery require to top-up with water in every 3 to 6 month. For solar application, these batteries required to be charge on low ampere. So, tall tubular solar batteries are C-10 rated batteries for slow charging capabilities. These solar batteries can store more power than any other battery. But if we compare than these solar batteries have comparatively short life and lower DoD(measure of amount of energy that we can draw from the battery, usually expressed in terms of %). Tall tubular battery is the most success, oldest and reliable technology in batteries. Mostly, you will need either 12V 150AH solar battery for home. Pros – Advantage High efficiency solar batteries i.e. 1500 life cycles. Long estimated working life around 5-7 years. Cost effective solar product. Easy to maintain, install and access. No need of heavy maintenance Very low repair/maintenance cost. Cons – Disadvantage

Tall tubular solar batteries are heavy in weight. You need to refill these solar battery timely. More space required compare to lithium-ion batteries. Lithium-ion solar battery There are different types in lithium-ion solar batteries. The best type of lithium ion battery for your solar power application is lithium iron phosphate (LiFePO4). LiFePO4 batteries are completely safe, not burnable, stable for 15 to 20 years and maintenance free. It has good electrical performance with low resistance. Lithium ion solar battery is generally used in all in one solar street light, solar power vehicles and mobile battery banks. The main advantage of this battery is the good thermal stability, increased safety, in addition to the high current rating and long cycle life if misused. Solar batteries for home with solar panel are increasingly focused on lithiumbased batteries, which have seen a steady reduction in costs in recent years. The biggest benefit of lithium-ion batteries is it’s extremely high life-cycle (up to 5000 cycles) and its high charge and discharge capabilities that help harvest more energy from your solar panel. They also lose less capacity at idle, which is useful in solar installations where energy is rarely used. For these reasons, lithium ion batteries are a good choice for any solar system whether it is small or large, off grid system or on grid system. The biggest disadvantage is its high price tag. Lithium-ion solar battery can cost 4 times more than a lead acid battery system. 1.7.3 Solar charge controller

Charge controller is the interface between array and battery bank. It protects the battery from overcharging and moderate charging at finishing end of charge of battery bank. Therefore it enhances the life of the battery bank. It also indicates the charging status of batteries like battery undercharged, overcharged or deep discharged through LEDs indications. Some switches and MCBs are also provided for manual or accidental cut-off of charging. In some charge controllers load terminals are also provided through a low battery charge cut-off device so that it can protect the battery bank from deep discharge. The technology adopted nowadays for manufacturing solar charge controller is MOSFET/IGBT technology. With this technology the idle current of the controller is less than 50mA depending upon the rating of the charge controller and its current. First the controller is connected to battery bank and then it is connected to solar array/solar module for sensing the voltage from the module. When the system is put into operation, the SPV modules starts charging the battery bank. Care should be taken that in no case the battery connections are removed from the controller terminals when the system is in operation, otherwise SPV voltage may damage the charge controller, since

the Solar voltage is always higher than the battery voltage. LED indications of Charge Controller Sr. LED Color Indication No. 1 Green Boost Charging (SPV1 & SPV2) 2 Yellow Float Charging (SPV) 3 Red Battery LOW 4 Red Battery REVERSE with Alarm 5 Red PV REVERSE with Alarm Types of charge controller i)PWM ii)MPPT PWM charge controller PWM solar charge controllers are the standard type of charge controller available to solar shoppers. They are simpler than MPPT controllers, and thus generally less expensive. PWM controllers work by slowly reducing the amount of power going into your battery as it approaches capacity. When your battery is full, PWM controllers maintain a state of “trickle”, which means they supply a tiny amount of power constantly to keep the battery topped off. With a PWM controller, your solar panel system and your home battery need to have matching voltages. In larger solar panel systems designed to power your whole home, panel and battery voltage aren’t typically the same. As a result, PWM controllers are more suited for small DIY solar systems with a couple of low voltage panels and a small battery. MPPT charge controller The maximum power point tracking (MPPT) charge controller takes the PWM

to the next level, by allowing the array voltage to vary from the battery voltage. By varying the array input, the charge controller can find the point at which the solar array produces the maximum power. The MPPT process works like this. Imagine having a battery that is low, at 12 V. A MPPT takes a voltage of 17.6 volts at 7.4 amps and converts it down, so that what the battery gets is now 10.8 amps at 12 volts. MPPT controllers takes the DC input from the solar panels, convert it to high frequency AC, and then change it once again to a different DC voltage and current. The point is the voltage will exactly adhere to the requirements of the battery. As the MPPT charge controller uses the negative line as a reference and then switches the positive line, they can be used in negative ground systems only. It is crucial to understand that voltage is a potential difference; the ‘difference’ refers to the difference between ground potential and some potential. This means that the starting point is below zero, but this is only used as a reference point. 1.7.4 Inverter Solar inverter also know as solar power inverter or solar energy inverter and this the heart of solar power system. It is an equipment that converts solar panel’s DC (direct current) power into AC (alternating current) power. This intelligent solar inverter also matches the required frequency, volt etc with electrical grid to run our load to be used at household and commercial premises. Apart from solar panel, the most important part of any solar system is solar inverter, because it converts power from the sun into useful energy. Before buying solar inverter, few points should be clear.

Types – On grid, Off-grid or Hybrid Technology – PWM or MPPT Feature – Remote or web monitoring Warranty – 2 years or 5 years Types of solar inverter The main roll of all types of solar inverters is to run the connected load on first priority. In the second priority, inverter exports the balance electricity in to battery or government grid. Type of inverter we choose as per situation, grid availability, power cut and load calculation. Accordingly, solar inverters are classified into three major types: i. ii. iii.

On grid solar inverter Off grid solar inverter Hybrid solar inverter On grid solar inverter On grid inverter also called grid tie or grid connected inverters, generally used with on grid solar system. This inverter works with grid or government electricity. On grid solar inverter will continue run your load and send power to the power grid when solar produce extra electricity.

These inverters are fully automatic and intelligent inverter with inbuilt protections which protect the complete solar system and solar panel from any fault. Generally, on grid solar inverter are used for home and commercial use in urban and industrial areas where electricity bills are high. Pros & cons of on grid solar Pros – Advantage Utilization of 100% solar power. No limitation of load. Export extra electricity to grid. Up to 70% subsidy on on-grid solar.

Less space for installation. Cons – Disadvantage Don’t work without grid. No electricity generation during power cut. No battery back-up. Off grid solar inverter

Off grid solar inverter also known as standalone solar inverter or solar battery inverter, are used in off grid solar system. These inverters draw DC power from solar battery & solar panel and convert into usable AC power. These systems place where no electricity is available such as in rural areas, off grid inverter based system is independent system. The major benefit is that power outages and other technical issues that the utility grid faces will no

longer be effective, as you have your own independent power system. Pros & cons of off grid solar Pros – Advantage Stand alone inverter and system. Work even without grid/electricity. No dependency on govt. electricity. Peace of mind with battery backup. Cons – Disadvantage Load limitation. Cannot export the electricity to grid. Costly compare to on grid solar. Hybrid solar inverter

Hybrid inverter is the combination of on-grid and off-grid solar inverter. This

inverter manage solar panel arrays battery storage and utility grid at the same time. These modern all-in-one inverter are generally highly versatile and can be used for grid-tie, stand-alone or backup applications. Pros & cons of hybrid solar Pros – Advantage Stand alone system. Can work without grid. Store electricity to batteries. Peace of mind with electricity backup. Export excess electricity to government grid. Cons– Disadvantage Expensive compare to on grid and off grid solar. Limitation of load. Solar inverter technologies PWM (Pulse width modulation) PWM is an old technology with a maximum output efficiency of 70%. This technology used in inverters to give a stable output voltage of 230V or 110V AC regardless of load. MPPT (Maximum power point tracking) MPPT is a latest solar technology with maximum efficiency up to 97%. Maximum power point tracking in RSC control can be realized by adjusting power or torque commands. Suppose the total power will be controlled from DFIG. The total power command will be generated through the MPPT control block. The input of the control section is rotor speed.

1.7.5 Field Junction box (FJB) FJB is the interface between solar panels and the charge controller. All the incoming/outgoing cables/wires from solar panel to charge controller are terminated at FJB. 1.7.6 Solar module mounting structure This is made up of galvanized iron frames and angles. In this structure flexibility is provided to change the module-mounting angle seasonally. This structure is grouted by small civil work and modules are mounted subsequently. Also, this mounting structure should be earthed suitably at several places if voltage of the array is more than 50 Volts. 1.7.7 Earthing kit

Earthing kit is provided to ground the mounting structure. When installing a solar photo-voltaic system (PV), it is extremely important all the equipment is grounded correctly. Failure to ground the entire system to include all the individual pieces, can be devastating, especially in an area that experiences lightning on a regular basis. Even if you seldom have electrical storms, all it

takes is one lightning strike or a single lose wire and all the equipment can be destroyed. Worse yet, it can start a fire and cause even more damage to your home. Electricity follows the path of least resistance, and while it’s almost impossible to know its exact path, we can take reasonable steps to try and direct the electricity someplace safe when a surge occurs. The way we do this is with an earth grounding system. Every electrical outlet, light socket, electrical device, gas line, copper pipe and service panel in your house is all tied together by a bare copper wire. Somewhere, this bare copper wire is either connected to a copper pipe which is literally buried in the earth, or it may be connected to a piece of re-bar in your home’s concrete foundation. This is where stray electric current is directed in the event of a lightning strike or short circuit. The same thing needs to be done to your solar PV system by connecting all the equipment together to include the solar panels, PV mounts, combiner box, inverter, charge controller and any other device that makes up your solar PV system. Here’s where some people make a major mistake: they don’t tie the grounding system of the solar panels to the grounding system of the house. Everything needs to be tied together to the same grounding system. This is called bonding.

To help ensure the electric current can find its way into the earth, you want a good conductive earth ground so the path of least resistance is “obvious” for the lightning strike, faulty wiring or a short-circuit. It is actually preferable to have several copper pipes buried in the ground on a single bonded earth

grounded system, provided all the equipment and grounding pipes are securely bonded together. This lowers the electrical potential that can build on the grounding wire should a lightning strike occur. Therefore, one should drive multiple pipes deep into the ground, surround them with rock salt, and moisten the area. Each grounding pipe should be around 8 feet deep, but no less than 6 feet. The soil tends to stay moist the deeper you go, due to reduced evaporation. This increases conductivity between the grounding pipe and the earth. For the outside grounding wire, use thick enough bare copper wire to handle large electrical loads, such as lightning. I’d recommend nothing less than 6 AWG for all outside equipment. Check with your local permit agency. The theory gets long and complicated, and I’ll leave other websites to explain that in more detail, but in short, if you have two independent grounding systems on the same set of connected equipment (some equipment on one ground and some on another), that’s a problem. If lightning strikes one system and not the other, or if lightning strikes the ground nearby, an electrical differential between the two systems will be created. Let’s say there is a common earth ground for all the outlets in your home (as there should be), and your inverter is plugged into one of these outlets. You also have two thick copper wires, negative and positive, going from your inverter to your solar panel array outside that also has its own grounding system, but is not bonded with the house grounding system. If lightning were to strike the solar panels outside, the electric current may go into the panel grounding system if you are lucky, or it may travel along the positive and negative wires going back to the inverter inside your house. Once there, it could arc again to the house wiring and use its grounding system instead. The arcing is what could destroy your equipment or worse yet, start a house fire. Also remember, it doesn’t take a direct hit from a lightning strike to induce voltage on the wires. If the grounding systems of the house and the array are tied into together (bonded), there is a much greater probability that the electric current from the lightning strike would stay on the common grounding system and not arc to something else. There are probably many ways to do it and hundreds of opinions. My system is permitted and up to code per my city’s requirements. Each city and county

may be different and have their own rules for grounding systems. 1.7.8 Cables We require different types of cables to connect module to module, modules to charge controller, charge controller to battery, or connect battery to load as required. The cable size used for interconnection of SPV module, charge controller and battery shall be minimum 2 x 2.5 sq. mm Cu. cable. As far as some hardware is concerned the screws and bolts/nuts are of chrome plated, stainless steel and brass so that rusting should not be take place. 1.8 Types of solar cell Solar cell are based on two types of technology as explained below: i)Silicon based technology. ii)Thin film technology. 1.8.1 Silicon based technology There are two types of silicon based solar cells as explained below: i)Monocrystalline solar cell ii)Polycrystalline solar cell Monocrystalline solar cell As the name implies, the entire volume of the cell is a single crystal of silicon. Monocrystalline solar panels are made from PV cells sliced out of a silicon ingot grown from a pure single crystal of silicon. When the cylindrical ingot is sliced its circular shape is squared giving the cell a unique octagonal shape. This shape distinguishes the cells from the cells made of polycrystalline silicon.

Further, monocrystalline solar cells have a uniform black color across all the cells. The PV cells in the panel offer better collection surface because of the pyramid pattern of the crystal. With proper treatment and addition of other materials, these cells are durable for up to 30 years or even more and offer higher efficiency than the other two types of silicon solar panels. The efficiency of monocrystalline solar panels, between 15-20%, is the highest among all silicon based solar panels. These cells are also efficient in terms of space occupied for the same output among all silicon-based cells. Polycrystalline solar cell Polycrystalline solar panels are made from PV cells cut from multiple silicon crystals. Melted silicon is poured into square moulds. After the silicon cools in the moulds it is cut into squares. The perfect square/rectangular shape distinguishes the polycrystalline cell from the monocrystalline cell (which is octagonal in shape). These have the same properties as monocrystalline solar panels but offer lower efficiencies while converting solar energy into electric energy. These cells are cheaper to make than monocrystalline cells because there is less wastage of silicon.

1.8.2 Thin film technology Thin film solar cells are the new generation solar cells that contain multiple thin film layers of photo voltaic materials. The thin film solar cells (TFSC) are also known as thin film photo voltaic cell (TFPV). The thicknesses of thin film layers are very less as (few nano meters) compared to traditional P-N junction solar cells. According to the type of photo voltaic material used, the thin film solar cells are classified into four types. They are:

1)Amorphous silicon (a-Si) and other thin film silicon (TF-Si) 2) Cadmium Telluride (CdTe) 3)Copper indium gallium deselenide (CIS or CIGS) 4) Dye-sensitized solar cell (DSC) and other organic solar cells Thin film solar cells provide better ways to produce electricity from sunlight than any other method. We can implement these panels in forest areas, solar fields, traffic and street lights, and so on. The cost of this panel is very less as compared to the older silicon wafer cells. Structure of thin film solar cell The structure of thin film solar cell is shown in fig.1.8.2. The structure and functioning of thin film solar cells are almost same as that of normal silicon wafer cells. The only difference is, in the thin flexible arrangement of the different layers and the basic solar substance used. The thin flexible arrangement of the layers helps to produce very thin form of cells that is much more efficient than the conventional silicon wafer cells. The below table is a very brief comparison between silicon based technology and thin film technology. When choosing a technology, it’s important to do

further research on below topics. Cell Technology

Types of Technology

Crystalline Silicon Mono-crystalline silicon (c-Si) Poly-crystalline silicon (pc-Si/ mc-Si) String Ribbon

Thin Film Amorphous silicon (a-Si) Cadmium Telluride (CdTe) Copper Indium Gallium Selenide (CIG/ CIGS) Organic photovoltaic (OPV/ DSC/ DYSC)

Voltage Rating (Vmp/ Voc) (Higher is better as there 80%-85% is less gap in Voc and Vmp)


Temperature Coefficients


Lower (Lower is beneficial at high ambient temperatures)

I-V Curve Fill Factor (Idealized PV cell is 100%)



Module construction

With Anodized Aluminum

Module efficiency Inverter Compatibility and Sizing

Mounting systems DC wiring

Frameless, sandwiched between glass; lower cost, lower weight 13%-19% 4%- 12% System designer has to consider Lower factor such as temperature temperature coefficients, coefficient Voc-Vmp difference, isolation is beneficial resistance due to external factors Special clips and structures may Industry standard be needed. In some cases labor cost is significantly saved May require more number of Industry standard circuit combiners and fuses Residential/

Application Type

Required Area

Commercial/ Utility

Commercial/ Utility

May require up to 50% more Industry standard space for a given project size

1.9 Factors affecting output i) Standard test conditions: Solar modules produce dc electricity. The dc output of solar modules is rated by manufacturers under Standard Test Conditions (STC). These conditions are easily recreated in a factory, and allow for consistent comparisons of products, but need to be modified to estimate output under common outdoor operating conditions. STC conditions are: solar cell temperature = 25 °C; solar irradiance (intensity) = 1000 W/m2 (often referred to as peak sunlight intensity, comparable to clear summer noon time intensity); and solar spectrum as filtered by passing through 1.5 thickness of atmosphere (ASTM Standard Spectrum). A manufacturer may rate a particular solar module output at 100 watts of power under STC, and call the product a “100-watt solar module.” This module will often have a production tolerance of +/-5% of the rating, which means that the module can produce 95 Watts and still be called a “100-watt module.” To be conservative, it is best to use the low end of the power output spectrum as a starting point (95 Watts for a 100-watt module). ii) Temperature: Module output power reduces as module temperature increases. When operating on a roof, a solar module will heat up substantially, reaching inner temperatures of 50-75 °C. For crystalline modules, a typical temperature reduction factor recommended is 89% or 0.89. So the “100-watt” module will typically operate at about 85 Watts (95 Watts x 0.89 = 85 Watts) in the middle of a spring or fall day, under full sunlight conditions. iii) Dirt and dust: Dirt and dust can accumulate on the solar module surface, blocking some of the sunlight and reducing output. Although typical dirt and dust is cleaned off during every rainy season, it is more realistic to estimate system output taking into account the reduction due to dust buildup in the dry season. A typical annual dust reduction factor to use is 93% or 0.93. So the “100-watt module,” operating with some accumulated dust may operate on

average at about 79 Watts (85 Watts x 0.93 = 79 Watts). iv) Mismatch and wiring losses: The maximum power output of the total PV array is always less than the sum of the maximum output of the individual modules. This difference is a result of slight inconsistencies in performance from one module to the next and is called module mismatch and amounts to at least a 2% loss in system power. Power is also lost to resistance in the system wiring. These losses should be kept to a minimum but it is difficult to keep these losses below 3% for the system. A reasonable reduction factor for these losses is 95% or 0.95. v) Dc to Ac conversion losses: The dc power generated by the solar module must be converted into common household ac power using an inverter. Some power is lost in the conversion process, and there are additional losses in the wires from the rooftop array down to the inverter and out to the house panel. Modern inverters commonly used in residential PV power systems have peak efficiencies of 92-94% indicated by their manufacturers, but these again are measured under well-controlled factory conditions. Actual field conditions usually result in overall dc-to-ac conversion efficiencies of about 88-92%, with 90% or 0.90 a reasonable compromise. So the “100-watt module” output, reduced by production tolerance, heat, dust, wiring, ac conversion, and other losses will translate into about 68 Watts of AC power delivered to the house panel during the middle of a clear day (100 Watts x 0.95 x 0.89 x 0.93 x 0.95 x 0.90 = 67 Watts).

SECTION-2 DESIGNING OF SOLAR PHOTOVOLTAIC SYSTEM 2.1 Definitions The following definitions are very important in designing a solar photo voltaic system. i) Solar Cell The basic photovoltaic device, which generates electricity when exposed to sunlight, shall be called a “solar cell”.

ii) Solar Module The smallest complete environmentally protected assembly of interconnected solar cells shall be called “module”. iii) Solar Panel A group of modules fastened together, pre-assembled and interconnected, designed to serve as an installable unit in an array shall be called “panel”. iv) Solar Array A mechanically integrated assembly of modules or panels together with support structure, but exclusive of foundation, tracking, thermal control and other components, as required to form a dc power producing unit shall be called an “array”. v) Solar Irradiation On any given day the solar radiation varies continuously from sunrise to sunset and depends on cloud cover, sun position and content and turbidity of the atmosphere. The maximum irradiance is available at solar noon which is defined as the midpoint, in time, between sunrise and sunset. The total solar radiant power incident upon unit area of an inclined surface (Watt/m²) is called total solar irradiance. vi) Insolation Insolation differs from irradiance because of the inclusion of time. Insolation is the amount of solar energy received on a given area over time measured in kilowatt-hours per square meter (kW-hrs/m2) - this value is equivalent to "peak sun hours". vii) Peak Sun Hours Peak sun hours is defined as the equivalent number of hours per day, with solar irradiance equaling 1000 W/m2, that gives the same energy received from sunrise to sunset. Peak sun hours is of significance because PV panel power output is rated with a radiation level of 1000W/m2. Many tables of solar data are often presented as an average daily value of peak sun hours (kW-hrs/m2) for each month. 2.2 Primary phases of designing an SPV system The primary phases of designing a photovoltaic system consists of the

following steps: I. II. III. IV. V. VI. VII. VIII. IX. X.

Planning Collection of information/data Load calculation Deciding battery capacity Selection of charge controller Deciding inverter capacity Selecting solar module. Module mounts Structure Wiring

2.2.1 Planning Before designing a solar photovoltaic system, several considerations are to be kept in mind such as The cost of the system should not be unusually high and at the same time the quality should also not suffer. Initial costs and lifetime costs shall also be taken into consideration. The system should be simple in design as far as possible with high reliability and efficiency. Whether central generation is beneficial or distributed is to be worked out. The system to be planned so as to cater for expected future growth. Prevention of improper load to be ensured. 2.2.2 Collection of Information/Data Following types of information are to be gathered i) Load/Application Voltage system e.g. AC or DC or both Operating voltage range of load Daily consumption Daily duty cycle Criticality of loads Monthly/weekly load profile

ii) Climatic conditions Insolation Latitude, Longitude Temperature Accessibility to site Terrain Local knowledge iii) User compatibility Understanding technical issues. Maintenance schedules and mentality. Whether the controls are field adjustable. Budget constraints. Understanding of managing energy budget. 2.2.3 Load Calculation For calculation of load first need to calculate the number of appliances in our home, their power ratings and number of hours they are running in a day. So let's begin with a sample example as shown below for a house. A house where the appliances, their power rating and their running hours are as follows: 5x LED Bulb, Power=15W, running hours=10hrs 3x Fans, Power=60W, running hours=12hrs 1x Refrigerator, Power=250W, running hours=12hrs 1xWashing Machine, Power=500W, running hours=1hrs 1xTV, Power=250W, running hours=5hrs Now we have the input data for calculation of load, lets understand how to calculate total load requirement of a house by below table: Total Power AC Running Total AC Sr. Quantity Rating, Appliances Hours Power,W Energy, No. (a) W Wh (c) (axb) (b) (axbxc)

1 2 3 4 5

LED Bulb Fans Refrigerator Washing Machine TV

5 3 1

15 60 250

10 12 12

75 180 250

750 2160 3000








5 250 1250 Total = 1255W 7660Wh The total load in a day for a particular house we have calculated as 7660wh. 7660wh=7.6 kwh or unit. 2.2.4 Deciding Battery Capacity For calculating the capacity and number of batteries, first the number of back up days are to be decided, based on number of consecutive sunless days. For example back up days for residential load = 3 to 5 days Back up days for industrial load = 7 to 14 days Back up days for poor weather = 7 to 14 days Check manufacturer’s recommended maximum depth of discharge (DoD) normally it is 80% for deep cycling 59% for shallow cycling. Check the temperature variations of site and determine the maximum DoD as per data given by battery manufacturer. Battery Capacity (In AH) = (AH rating X No. of back up days) / Max DoD No. of series Batteries = System DC Voltage / Battery Voltage No. of Parallel Batteries = Total AH Required / AH of Individual Battery If we use lead acid battery/tubular battery then the depth of discharge(DoD) will be 50%, but if we use Li-ion battery then depth of discharge will be 80% to 90%. From previous example we have energy requirement of 7.6kwh, now here comes a trick , we consider the 20% losses in inverter then the energy taken out from the battery by inverter will be 7.6kwh x 120% = 7.6 x 1.2 = 9.12 kwh. It is clear that we required 9.12kwh of energy from the battery to fulfill our load requirement. So the battery capacity for one day storage and 50% DoD is given by: Required battery capacity=9.12 x 1/0.5 = 18.24kwh.

Now suppose we are using 12V and 200 Ah batteries to store power then energy storage in one battery is 12v x 200 Ah=2400wh =2.4kwh Now number of batteries can be given by required capacity divided by energy storage in one battery as: Number of battery = 18.24/2.4 = 7.6 or 8 batteries So we requires 8 batteries of 12V and 200 Ah to fulfill our requirement of 7.6kwh/day. The fact is when battery stores charge then some power is lost in the battery in the form of heat, so to proceed for the calculation of charge controller and solar module we need to consider the energy lost in battery, we generally consider it as 15%. 2.2.5 Selection of Charge Controller Charge controllers are included in most PV systems to protect the batteries from overcharge and/or excessive discharge. The minimum function of the controller is to disconnect the array when the battery is fully charged and keep the battery fully charged without damage. The charging routine is not the same for all batteries. A charge controller designed for lead- acid batteries should not be used to control Ni-Cd batteries. Charge controllers can be used in parallel to add more modules to a battery bank. The charge controller consumes some power so the transfer of power is not 100%. The typical efficiency of charge controller is 85% to 95%. Salient feature of Charge Controller Power devices should be of solid state, high efficiency with two stage charging technique. Protection against transient/surge. Prevent discharge of battery through solar panel during night. Protection against overcharge of the battery. Protection against reverse connection of battery and module. Robust enclosure and cooling with heat sink. Control, temperature compensated set points and equalization. Suitable MCB’s provided at solar input of 100 Amp. 2.2.6 Deciding Inverter Capacity An inverter is called the heart of the system because all electronic management is done by the inverter. As inverter have electronic components which consumes energy so the efficiency of the inverter will never be 100%.

Typical efficiency of inverter is 80% to 90%. For good efficient inverter efficiency is 90% to 95%. For deciding inverter we first see the load. The capacity of inverter must be slightly above of the load requirement, lets assume for above sample example we have load of 1255 Watt, so we would consider an inverter of lets say 1500 Watt or 1.5kva. 2.2.7 Selecting Solar Module To make your technology selection, you must first be aware of several considerations. PV modules have standard power ratings and so in order to determine the amount of modules to be connected you must first establish the load that you want to feed in kw. NOCT and STC As a reference to compare performances of SPV modules, manufacturers establish the so-called standard test conditions (STC) and nominal operating cell temperature (NOCT) which have specific test conditions that allow you to compare the virtues of each module between them. STC assume 1kw/m2, 25°C of module operating temperature and 1.5 AM (Air Mass), while NOCT assume 800W/m2, 45°C operating temperature, 1m/s wind speed, 20°C ambient temperature and that the module has a ground mounted feature (for air circulation). Under these conditions you must evaluate: Open circuit voltage Short circuit current Nominal power and current Voltage and power at MPP Efficiency Crucial parameter to size your system, among each type of technology there are also variations in efficiency. This parameter is associated with the use of available space in m2 to supply the same amount of power. In other words, the higher your efficiency, the smaller your panel is to provide the same amount of DC power Temperature Coefficients Rising temperature values affect the performance of PV modules, they reduce the efficiency, voltage and current as well.

Although current temperature coefficients are generally provided in the datasheet, the most important ones are the voltage and efficiency temperature coefficients, as voltage is severely affected with elevated temperature values. Voltage As you know connecting modules in series would lead to higher voltages. Inverters have a range of voltage for MPPT (maximum power point tracking). You have to make sure that the operating voltage of your array (at 20°C and 60°C of temperature module) will be within the MPPT range of the inverter. Besides, there is another limitation in the voltage of the array, each string cannot exceed 600 Vdc according to American norms and 1000 Vdc according to European norms. Tolerance Manufacturing processes are not perfect. That is why manufacturers will provide a tolerance value for the nominal power output of the module. Less

the tolerance is, the more accurate your design will be. Solar Panel Dimension Finally, the ultimate consideration is to watch out for the panels dimensions, you must make sure that the width and length of the panel, suits your available space, whether it is on the roof or on the ground. Considering all these factors will reduce the chances that you need to change your module selection, nevertheless, sometimes you will need to iterate several solutions according to space, inverter selection and power demand. The losses in solar panel we consider as 25%. Suppose we need the load of 10kwh then we require solar panel of capacity 1.25x10=12.25kwh. Sample Example: In the trail sample example we have the energy requirement of 9.12kwh energy from the battery, now we'll add battery losses(15%) in it, so it will be 9.12+0.15x9.12 = 10.49kwh Now we add charge controller losses(5%) then it will be 10.49+10.49x0.05 = 11.015kwh We need 11.015kwh energy from the solar panel, Now considering the panel losses(25%) then we have 11.015+11.015x0.25 = 13.77kwh

Important point to consider is the value of solar power potential, means for how much time the sun is available for your location in a day. Fig2.2.7.6 below provides the clear picture of the available sun hours according to the world map. Now if we consider for India, we have 5 hrs of sunshine so the module power will come 13.77kwh/5hr = 2.75kw If we use solar module of 250Watt power then we require 11 module to fulfill the load requirement of 1255 W. 2.2.8 Module Mounts While mounting the modules, following points should be considered for getting maximum output from the solar modules: Modules should be oriented to face the Sun. The modules produce more power at STC 25°C. The mounting and color of the modules can sometimes be chosen

to blend with the architecture. Tracking the Sun increases the amount of power from an array. 2.2.9 Structure Select type of structure i.e. ground mount, rooftop mount, pole mount or tracker. A group of modules mounted on a single unit of structure and interconnected together is called panel. Module mounting structures are made of three types of materials. They are hot dip galvanized iron, aluminum and mild steel (MS). Galvanized Iron In galvanizing process, zinc coating is applied to iron or steel to prevent it from rusting. There are several methods of galvanizing. The most common method employed in module mounting structure is the hot dip galvanization. In hot dip galvanization, the material to be galvanized is submerged in molten zinc at a temperature of around 449 °C. The galvanized material (iron or steel) when exposed to atmosphere, the pure zinc reacts with the oxygen forming zinc oxide which further reacts with the carbon di-oxide in the atmosphere to form zinc carbonate. The zinc carbonate is dull grey colored and strong material. It gives protection to the material beneath the coating from any corrosion. In solar PV module mounting structure, iron is used for galvanizing process. Mild Steel Mild steel is made by melting iron ore and coal together in a furnace. Once the melting is done, it is moved to another furnace to burn of any impurities. It has very low carbon content ranging between 0.5% to 0.25% in weight. Mild steel is not used very often in case of solar PV module mounting. It is generally used in case of not so strong roofs, when there is a need for light weight structures. Mild steel has very less carbon. It is very flexible and can be made in to several shapes as it is machinable. Aluminum Aluminum is a silvery white, soft, flexible material. It is very resistive to corrosion and does not corrode easily. Compared to galvanized iron, this is light weight and cost-effective. Mounting Structure Base The mounting structure base has to be strong enough to carry the entire load

of the solar PV module mounting structure, solar PV module, other balance of systems that are placed below the solar PV module. In case of slope roofs and ground mounting, the base has to be drilled into the roof. In case flat roofs, the base can be drilled into the roof or can be concealed with a concrete. Direction of Solar Modules: The solar modules should be placed in such a way that most of the sunlight falls on them. The best direction to place the solar modules is the place them facing the equator. This means, in the northern hemisphere the solar PV modules should be placed facing true south as the equator is lying to the south of the northern hemisphere. In case of regions in the southern hemisphere, the solar PV modules should be placed facing the true north as the equator is lying to the north of the southern hemisphere. In case of India, which lies above the equator in the northern hemisphere, it is ideal to place the solar PV modules facing true south. In case of Australia, which lies in the southern hemisphere, the equator lies above it. Hence it will be ideal to place the solar PV modules facing true north in Australia. There are also installations where the solar PV modules are placed in wave form in east–west direction and claim to have little more better output when compared to traditional true south or true north installations.

2.2.10 Wiring Selecting the correct size and type of wire will enhance the performance and reliability of PV system. The size of the wire must be large enough to carry the maximum current expected without undue voltage losses. All wire has a certain amount of resistance to the flow of current. This resistance causes a drop in the voltage from the source to the load. Voltage drops cause inefficiencies, especially in low voltage systems (12V or less). Typical values of module current and voltages are provided by the manufacturer. Based on system voltage and current decide size of wire/cable to be used for module

interconnection. Calculate output current and voltage of the panel and decide specifications of wire/cable for panel interconnection. Always use minimum possible wire lengths. Always use suitable lugs, connecters etc for connection. Decide number and type of switches, fuses and circuit breakers as per load, system and user requirement. 2.3 Sample system design In solar system design: Find out the size of components(battery, panel etc). Match power and energy requirement of appliances. The designing of a system can be better understood by the following examples: 2.3.1 Example 1: Total Number of Daily Total S. Appliance AC AC AC appliances usage No. name Power(W) hours power energy (b) (a) (c) (a x b) (a x b x c) 1 Tube Light 40 3 6 120 720 2 Fan 55 2 10 110 1100 3 TV-32" 35 1 6 35 210 4 Refrigerator 120 1 24 120 2880 5 AC 1.5 Ton 1400 1 3 1400 4200 9110 1785 Total= Wh/day W As we know the 'current' in a solar photo-voltaic system always flows in order as shown below(for an AC system):

But for the designing purpose we consider the path in reverse order as shown

below (that means we first figure out the load requirement then we choose the inverter, then we go for solar batteries, then we look for charge controller and finally we decide the sizing solar panel):

Now we have calculated the total load in the table above as 1785W and energy requirement as 9110 Wh/day or 9.1kWh/day. Now the process for designing the solar system is given as below: 1) Inverter: For 1785W power requirement the inverter of capacity 2kW or 2kVA matches very well. As inverter converts power from dc to ac so there is power loss within the inverter in the form of heat so we consider the loss as 20%. So the energy required from the battery will be: = 9.1kWh +0.2x9.1 kWh = 10.9kWh 2) Battery: All energy stored in the battery is not available to us this is determined by the depth of discharge. There is two technology one is lead-acid which have 50% DOD and second is Li-ion which have 90% DOD. We are taking example of lead-acid then we have Battery Size = Energy Required/DOD Battery Size = 10.9kWh/0.5 = 21.8kWh So the energy storage will be 21.8kWh but we require energy per day is only 10.9kWh. Now remember batteries are available in the market in V & Ah rating. Suppose we have battery of 12V & 200Ah, then number of batteries required will be come out as No. of batteries required = 21.8kWh/(12V x 200Ah) = 9.08 If we round it off then the number of battery will be '9'. But it's difficult to connect 9 batteries together so we take 8 or/10 batteries or other option available is the different sizing of battery. We have calculated battery sizing for one day storage for 2 days storage we double the number of batteries. Now input given by charge controller to battery is 10.9kWh plus the losses in battery(15% battery loss): Input to battery = 10.9kWh + 10.9x0.15kWh = 12.5kWh

3) Charge Controller: The charge controller takes care of battery charging & discharging so it has some electronic components that consumes energy. Lets consider the losses as 4% then we have required energy from the panel as Input to charge controller = 12.5kWh + 12.5x0.04kWh = 13kWh

4)Solar Panel: Energy, panel should supply = 13kWh Losses within solar panel = 25% Total energy panel must generate=13kWh + 0.25 x 13kWh =16.25kWh per day Suppose we have 5.5 hrs of solar radiation per day then, Power of solar panel =16.25/5.5 = 2.95kW Suppose we take 250W panel from market(remember this is peak or maximum power rating) Number of panels required= 2950W/250W = 12 Panels

Solar system summary Load energy required = 9.1 kWh per day Inverter power rating = 2kVa Battery storage (1 day) = 21.8 kWh, 9 batteries, 12V, 200Ah Solar Panel = 2.95kW, 12 panel of 250 W. 2.3.2 Example 2:

S. No.

Appliance Name

1 2 3 4

Tube Light Fan TV-32" Refrigerator Washing Machine AC 1.5 Ton

5 6

40 60 35 130

4 4 2 1

5 12 5 24

160 240 70 130

Total AC energy (a x b x c) 800 2880 350 3120









1400 2400 W

2800 10750 Wh/day

Number AC of Power(W) appliances (a) (b)


Daily usage hours (c)

Total AC power (a x b)

Our load requirement comes out to be 2400W and energy requirement 10750Wh/day. Now we will design our system as shown below: 1) Inverter: Inverter Size = 2.5kW or 2.5kVa Input to inverter from battery = 10750 + Inverter Loss(20%) = 10750 + 0.2x10750 = 12900 Wh = 12.9kWh 2) Battery: Battery Loss = 15% = 0.15x 12.9 kWh = 1.94kWh Input to battery from charge controller = 12.9 + battery loss = 12.9 + 1.94 = 14.84kWh Battery Size = Energy required/ DOD

= 12.9/0.5 = 25.8kWh For battery capacity 12V and 200Ah we need following number of batteries: = 25800Wh/2400Wh = 10.75 The number of batteries in round figure is coming out to be '11', but for the ease of connection we can take it as '10' or '12'. 3) Charge Controller: Input to charge controller = 14.84kWh + charge controller loss = 14.84 + 14.84 x 0.04 = 15.43kWh

4) Solar Panel: Energy, panel should supply = 15.4kWh Losses within solar panel = 25% Total energy panel must generate = 15.4kWh + 0.25 x15.4kWh = 19.25kWh per day

Suppose we have 5.5 hrs of solar radiation per day then, Power of solar panel =19.25/5.5 = 3.5kW Suppose we take 200W panel from market(remember this is peak or maximum power rating) Number of panels required= 3500W/200W = 17.5 = 18 Panels Solar system summary Load energy required = 10.75 kWh per day Inverter power rating = 2.5 kVa Battery storage ( for 1 day) = 25.8 kWh, 11 batteries, 12V, 200Ah Solar Panel = 3.5 kW, 18 panel of 200 W.

SECTION-3 INSTALLATION OF SOLAR PANEL 3.1 Introduction Solar modules are to be installed firmly and permanently on metallic structures. The structures depend on the application and size of the system. For smaller systems like solar home systems, simple module mounting structures are used. For systems like solar streetlights, solar powered signal lighting, solar pumps etc. pole mounting module frames are used. For bigger systems like solar power plants and solar powered railway signaling installations, bigger array mounting structures are used. 3.2 Testing before installation Before installation the solar panels are tested at the manufacturing unit to check for the following parameters: Voc-open circuit voltage Isc-short circuit current Vmax- maximum voltage Imax- maximum current Pmax- maximum power at standard test conditions or peak power output.

The following table shows typical user’s specifications of different modules: Peak power output (Pmax)

Nominal Voltage

Open circuit voltage (Voc)

Short circuit current (Isc)

Max. Max voltage current (Vmax) at (Imax) at Pmax Pmax 4W 6V >11.5V >0.63A 8.5V 0.47A 4W 12V >21V >0.3A 16.7V 0.23A 8W 12V >21V >0.56A 16.7V 0.47A 10W 12V >21V >0.70A 16.7V 0.59A 12W 12V >21V >0.84A 16.7V 0.71A 18W 12V >21V >1.26A 16.7V 1.07A 35W 12V >21V >2.4A 16.7V 2.09A 40W 12V >21V >2.7A 16.7V 2.39A 50W 12V >21V >3.3A 16.7V 2.99A 65W 12V >21V >4.0A 16.7V 3.89A 70W 12V >21V >4.5A 16.7V 4.19A 75W 12V >21V >5.0A 16.7V 4.49A 90W 12V >21V >6.0A 16.7V 5.38A The above values are at standard testing conditions such as 25 °C cell temperature and 1000W/m2 solar radiation. "The output will be reduced as temperature rises and intensity of sunlight reduces." Although accurate power is measured with the help of module tester at supplier’s end, however to check working of module Voc and Isc can be measured at site as shown in Fig.3.2a (a) & (b) by simple multimeter in two different modes i.e. current mode and voltage mode when module is placed in sunlight. The solar panel is kept in such a position that it receives maximum sunlight.

The typical I-V curve of a 35-watt module with 36 series connected cells is illustrated in Fig 3.2b

3.3 Installation guidelines The installation of solar power system involves the following major steps: Civil foundation job Assembly and fixing of support structure. Mounting of solar modules on the support structure. Installation of battery bank.

Interconnection of SPV panel in series & parallel configuration, charge control unit and FJB Connection of battery bank and load Earthing of lightning protection unit. 3.3.1 Mounting the solar modules For mounting the solar panels first determine mounting method i.e. roof mount or ground-mount. While mounting the solar modules, following points should be considered for getting maximum output from the solar modules: Modules should be oriented south facing in northern hemisphere and north facing in southern hemisphere to receive maximum sunlight. The modules produce more power at low temperature and full sun. Tracking the sun increases the amount of power from an array The solar panels are generally installed in such a way that they can receive maximum direct sunlight without shade from any building/trees nearby falling on them at any part of the day. As we know that the sun rises in the east and sets in the west as a result of earth’s rotation around its own axis. Also the earth revolves around the sun. Due to these two movements there is variation in the angle at which the sun’s rays fall on earth’s surface over a year. At any particular place on earth this variation in angle in one year may be up to 45 degrees. Considering these facts the following guidelines are to be kept in mind while installing solar panels: 1. Solar panels should be installed at an angle of ‘(Latitude of the place + 10) degree’ from horizontal. For example, New Delhi has a latitude of 26 degree, hence any solar panel in New Delhi is to be installed at an angle of 26+10=36 degree inclined to horizontal. 2. Solar panels should be installed south facing in the northern hemisphere and north facing in the southern hemisphere. The directions north-south may be found with the help of magnetic compass. The picture given in Fig 3.3.1(a) illustrates this

3. Any obstruction (such as tree or building) should be avoided in East, West or South of the place of installation. The following is the criteria: I. II.

East or West: The distance between solar panel and obstruction should be more than double the height of obstruction. South: The distance should be more than half the height of obstruction.

4. The support for the solar panel need to be a robust one and should not be accessible to general public. It should be so installed that rainwater, bird dropping, leaves etc. do not accumulate and the top surface can be cleaned easily. 5. Calculate tilt of array 6. Calculate space between rows to avoid shadow. I.

Distance between adjacent rows of structures have to be


maintained so that the shadow can be avoided. Calculate or measure panel height H. Locate the PV site latitude. The minimum panel spacing W is given by the formula W = H X U Where H is the vertical height of the panel from the base as shown in fig 3.3.1(b) below. U can be determined from the table given below, corresponding to the latitude of PV site.

LATITUDE 0 10 20 28 30 32 34 36 38 39 40 41 42 44 46 50 55

U 0.614 0.885 1.259 1.699 1.842 2.001 2.195 2.404 2.667 2.818 2.972 3.166 3.359 3.844 4.499 6.547 14.520

3.3.2 Electrical interconnections I) Cables a) Cable and terminal connectors are provided with the system. b) Required length of cable shall be cut and terminals to be crimped. c) Crimping tool to be used for crimping terminal to cable. d) Wire size shall be increased as the length of the cable increases. e) All exposed wiring must be in conduits/capping-casing. f) Wiring through roof must be water proof. g) Where the wiring is through flammable materials like thatched roof, they must be in a metal conduit.

II) Connections to the solar module a) Open the junction box of the module and connect the module cable with correct polarity. b) Close the junction box and tie the module cable on the module frame.

(iii) Interconnections between charge controller and solar modules For interconnections between charge controller and solar modules, the following general installation guidelines shall be followed: For interconnecting the SPV/arrays with charge controller and battery bank, use minimum wire length so as to avoid the DC voltage drop in the line. At the same time care must be taken to ensure that no wires are hanged loose. Connect all modules in series & parallel connections. Use cable conductor size as given below to avoid voltage drop of the system: ➢

For series connection of modules – 1x2.5 mm2 PVC sheathed unarmored. ➢ For parallel connection of modules – 2x2.5 mm2 PVC sheathed unarmored. ➢ From FJB to charge controller and charge controller to battery

bank – 2x10 mm2 PVC sheathed unarmored. Open the junction boxes (FJBs) and remove the fuses provided inside the junction boxes Note: Switch OFF MCB of charge controller before any connection. Connect battery positive (+) and battery negative (-) of charge controller to the battery bank. Next connect SPV-1 negative(-) and SPV-1 positive(+) of charge controller. Note: Charge controller will be damaged if SPV array is connected first then the battery bank. Battery connections must be given first to charge controller. Insert and replace all the fuses of junction boxes after connecting all the cables to charge controller and to the battery bank. Do not short negative terminals of the system. All the positive (+) and negative (-) wires will run separately from the junction boxes Note: Switch ON MCB of the charge controller when all the connections are thoroughly checked and fuses are replaced in the junction boxes.

SECTION-4 MAINTENANCE & TROUBLESHOOTING 4.1 Maintenance Solar panels requires virtually no maintenance. However the associated equipments such as batteries and charge controller are to be maintained. Once a fortnight the surface of the panels should be wiped clean with wet rag to remove dust, fallen leaves, bird dropping etc. Only water to be used and no other cleaning agent.

With solar panel secondary battery maintenance becomes minimum. Still general periodical maintenance of battery should be carried out in usual manner and as per maintenance manual. For efficient working of SPV system certain precautions are to be observed as given below. 4.1.1 Precautions and preventive steps Please ensure that: a) SPV modules are connected in parallel and SPV panel output voltage is less than 25 volts under normal sunshine condition (for 12 V system/module) b) All connections are properly made tight and neat using the crimped red(for +ve) and black(for –ve) wires supplied by the manufacturer in order to avoid reverse connection. c) The rating of the fuse in the charge controller is not changed. d) The SPV panel is installed facing South for Northern hemisphere/North for Southern hemisphere and with the correct ‘angle of tilt’. e) There is no shadow on any part of the SPV panel at any time of the day, to get maximum power. f) SPV modules are protected against any act of vandalism and accidental strike or hit by heavy objects, like stone, hammer etc. If the SPV panel is installed on ground, it must be fenced properly to protect it from cattle and to prevent from any damage/theft. Fencing should be made in such a way that no shadow should fall on SPV panel at any time of the day. g) Battery bank is placed on a rack or platform insulated from ground and located in a well ventilated room and also sufficient clearance is there over the battery. h) First the battery bank, then SPV panel and then load is connected to SPV charge control unit and for disconnection reverse sequence is adopted. i) Battery terminals are never shorted even momentarily, as shorting will result in heavy spark and fire. (to avoid the same connect the cable at charge controller end ‘first’ and then battery end.) j) Never connect the load directly to the SPV panel as SPV panel may give higher/lower voltage than required by the load equipment and hence the equipment may be damaged permanently.

k) Blocking diode is provided at the array output for protection against reverse polarity. l) Make sure that the solar PV module gets direct sunlight throughout the day where you install it. m) The green indicator on charge controller is only an indication for charging. It will glow even at small amount of charging. So to ensure efficient charging, the availability of direct sunlight over the solar PV module for the maximum hours of the day should be ensured. n) It is not heat but light that produces energy. So let direct sunlight to fall on the module surface without shades.

4.2 Troubleshooting The SPV power source is reliable source of electrical energy. However, there may be rare instances, when the SPV power source is not able to drive the connected equipment. The diagnosis of the problem in such situations starts with the battery. Check the voltage of the battery bank. If the voltage of the battery bank is correct as indicated in charge controller, there may be problem in the inverter or switch between load and inverter i.e. either inverter is tripped or switch/load MCB is tripped or load fuse is blown off. If none of the above fault is observed then check the specific gravity of the electrolyte in the secondary cells of the battery. There may be two cases: a) If the specific gravity is above the level 1.2 (hydrometer reading 1200) value or as specified in the maintenance manual, it implies that the battery is in order and the problem would be either with the charge controller or load. Disconnect the load from charge controller and connect it directly to battery bank. If the equipment operates, the defect may be with the charge controller. Disconnect the charge controller and check as per troubleshooting instructions given in the manual supplied

with it or inform the manufacturer/supplier. b) If the specific gravity of the electrolyte is below the specified level and BATT/LOW (Red)) LED is glowing, the problem may be with any of the following: i.


Load: This may be drawing more current from the battery than required. In such case, battery is bound to get discharged, even if SPV panel is functioning properly. This would result in frequent tripping of the load. To avoid this, get the load equipment checked and replace any defective components. SPV panel: The SPV panel may not be producing required power for which the power source has been designed. In that case, check the SPV panel as given below: Check for any loose connection/breakage of wire in SPV module interconnections. If there is no such loose connection, clean the SPV modules with soft cloth. Whenever there is bright sunshine, measure the voltage and current of each module after disconnecting the wire. If any of the SPV modules gives low voltage/current output during bright sunlight (sun intensity 1000 W/m2) inform the manufacturer/supplier with module serial number along with the measurement taken, for necessary investigations.


Failure of blocking diode: Blocking diode fails in short circuit and open circuit mode. If it is failed in short circuit mode, voltage across its terminal will be zero in place of 0.7V while charging current flows through it. When it fails in open circuit mode, the current will not flow through the diode. The diode may be checked as per standard method of checking of diode by removing from the circuit.

Apart from these some possible complaints and troubleshooting methods for solar modules are listed in table below:

S. No.


Possible Failure


Probable Cause Conductor break Corrosion Loose connection Improper connection


No output Connector

Junction box

Charge controller None of the above


Output voltage OK, but


Defective connector Loose connection Pin loose Corrosion Improper fixing Mechanical damage Connection problem Electronic failure Internal problem



Replace cable

Verify the wire connections are tight, corrosion free and of correct polarity.

Replace connector

Return to factory for servicing Connect properly Replace charge controller Return to factory, if within warranty Return factory,

to if

no output current


Shading Solar module


No charging indication on the charge controller

Dirt accumulation

Module Cable

Module Charge controller

Breakage Corrosion Dry solder Loose connection Broken module Electronic failure


Solar module Dirt

within warranty Remove the shades or change the location of the module and ensure maximum sunlight to fall on the module. Clear the particles on the module

Replace cable

Replace module Replace charge controller Remove the shades or change the location of the module and ensure maximum sunlight to fall on the module. Clear




Output voltage for less duration

Improper installation

Module cable


Solar module

particles on the module Place the module in such a way that direct sunlight falls on the module for more hours.

Breakage Corrosion Loose connection Dry solder Corrosion

Replace cable

Insufficient charging

Charge the battery to full charge condition & check the output duration.

Low capacity, acid leakage, Replace battery terminal broken Remove the shades or change the location of the module and Shading ensure maximum sunlight to fall on the module. Clear the

Dirt accumulation



Insufficient charging

Solar module

Improper installation

Always low battery condition

Loose connection



Charge the battery to full charge condition and check the output duration. Place the module in such a way that direct sunlight falls on the module for more hours. Replace cable

Charge Controller

Electronic failure Corrosion

Fix the cable properly and ensure that the connections are tight with correct polarity. Replace the charge controller


Mishandling/ transportation

Unserviceable, replace

Module Cable

Front Glass broken No voltage Across blocking diode

particles on the module

Improper fixing

Diode failed in short Random circuit mode failure

Replace diode



Voltage high Across blocking diode

Diode failed in open Random circuit mode failure

Replace diode


SECTION-5 MCQ Q.1 What is the rating of power? 1. 2. 3. 4.

Joule. Watt-hour. Watt. Calorie.

Answer : Watt. Solution: The watt (symbol; W) is a unit of power. In the international system of units (SI) it is defined as a derived unit of 1 joule per second and is used to quantify the rate of energy transfer. Q. 2 What does the word photovoltaic means? 1. 2. 3. 4.

Sun-powered. Light-cells. Light-electricity. Solar-energy.

Answer: Light-electricity Solution: 'Photovoltaic' has two parts; photo, derived from the Greek word for light, and volt, from electricity pioneer Alessandro Volta. And that's exactly what photovoltaic systems do turn light into electricity! Q. 3 Who discovered the photovoltaic effect? 1. 2. 3. 4.

American physicist Enrico Fermi. Italian physicist Alessandro Volta. German physicist Heinrich Rudolf Hertz. French physicist Edmond Becquerel.

Answer: French physicist Edmond Becquerel. Solution: Edmond Becquerel was the first person to realize that sunlight

could produce an electric current in a solid material in 1839, but it took more than a century for scientists to fully understand this process and develop a practical solar cell. Q. 4 What are the most common photovoltaic cell used today? 1. 2. 3. 4.

Organic cells. Plastic cells. Polymer cells. Crystalline silicon cells.

Answer: Crystalline silicon cells. Solution: Unveiled by Bell labs in 1954, silicon cells were the very first successful photovoltaic (PV) technology, and they remain the most common PV cells in use today. Q. 5 Which of these is not considered a 'soft cost' of solar power? 1. 2. 3. 4.

Connection fees. Labor. Permits. Solar panels.

Answer: Solar panels. Solution: Solar soft costs are the expenses associated with customer acquisition, permitting, inspection, interconnection to the electric grid, installation, taxation, and system financing. These expenses represents up to 64% of the total cost of a solar photovoltaic(PV) system. Q. 6 What form of energy do concentrating solar power technologies use to generate electricity? 1. 2. 3. 4.

Static. Chemical. Thermal. Magnetic.

Answer: Thermal. Solution: Concentrating solar power technologies use mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat. This thermal energy can then be used to produce electricity via a steam turbine or heat engine that drives a generator. Q. 7 Which of the following is not a technology used in concentrating solar power? 1. 2. 3. 4.

Power tower. Linear Fresnel. Cathode ray tube. Parabolic trough.

Answer: Cathode ray tube. Solution: Parabolic trough, linear fresnel and power tower are all types of concentrating solar power systems. They may look very different, but they operate on the same principle, focusing the sun's rays on a central receiver. Q. 8 About how many mirrors are used at Ivanpah Solar Electric Generating System, the largest concentrating solar power facility in the U.S.? 1. 2. 3. 4.

350,000 3500 350 35,000

Answer: 350,000 Solution: Spanning 3,500 acres of Southern California desert, Ivanpah's 173,500 'heliostats'(each made up of two mirrors) focus the sun's rays on three 459 foot tall, heat collecting 'power towers.' Water circulated through these towers turns to steam, driving turbines that can generate up to 377 megawatts of electricity enough to power 140,000 homes in California. Q. 9 A module in a solar panel refers to. 1. Series arrangement of solar cells.

2. Parallel arrangement of solar cells. 3. Series and parallel arrangement of solar cells. 4. None of the above. Answer: Series and parallel arrangement of solar cells. Q. 10 The efficiency of solar cell is about. 1. 2. 3. 4.

25 % 15 % 40 % 60 %

Answer: 15% Solution: The efficiency of a solar cell is determined as the fraction of incident power which is converted to electricity and is defined as:

Where: Voc is the open-circuit voltage; Isc is the short-circuit current; FF is the fill factor and η is the efficiency. The input power for efficiency calculations is 1 kW/m2 or 100 mW/cm2. Thus the input power for a 100 × 100 mm2 cell is 10 W and for a 156 × 156 mm2 cell is 24.3 W Q. 11 What is the maximum possible output of a solar array? 1. 2. 3. 4.

300 W/m2 100 W/m2 250 W/m2 500 W/m2

Answer: 250W/m2

Q. 12 The current density of a photo voltaic cell ranges from. 1. 2. 3. 4.

10-20 mA/cm2 40-50 mA/cm2 20-40 mA/cm2 60-100 mA/cm2

Answer: 40-50mA/cm2 Q. 13 A 'pyranometer' is used for the measurement of. 1. 2. 3. 4.

Diffuse radiations only. Direct radiations only. Both direct and diffused radiations. None of the above.

Answer: Both direct and diffused radiations. Q. 14 Reflector mirrors used for exploiting solar energy are called. 1. 2. 3. 4.

Mantle. Heliostats. Diffusers. Ponds.

Answer: Heliostats. Solution: Heliostat is an apparatus containing a movable mirror, used to reflect sunlight in a fixed direction. Q. 15 The function of a solar collector is of converting solar energy into. 1. 2. 3. 4.

Radiations. Electrical energy directions. Thermal energy. All of these.

Answer: Thermal energy. Solution: The energy that comes from the temperature of the heated

substance is called thermal energy. Q. 16 What are 'pyrheliometers'? 1. 2. 3. 4.

Instruments measures beam radiations. Diffuse radiations. Direct radiations only. None of the above.

Answer: Instruments measures beam radiations. Solution: A pyrheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal voltage is converted via a formula to measure watts per square meter. Q. 17 Temperature attained by cylindrical parabolic collector is of the order of. 1. 2. 3. 4.

50-100 °C 100-150 °C 150-200 °C 200-300 °C

Answer: 200-300°C Q. 18 In a solar collector, why is the transparent cover provided for? 1. 2. 3. 4.

Protect the collector from dust. Reduce the heat losses from collector beneath to atmosphere. Transmit solar radiation only. All of the above.

Answer: All of the above. Q. 19 There are three types of solar cells.

1. True. 2. False. Answer: True. Solution: There are three types of solar cells. Single crystal, polycrystalline, and amorphous silicon cells are the major types. Q. 20 Series and parallel combination of the solar cell is known as. 1. 2. 3. 4.

Solar array. Solar light. Solar sight. Solar eye.

Answer: Solar array. Solution: Series and parallel combination of the solar cell is known as solar array. Shunt diodes are used to avoid the circulating current. Q. 21 Full form of 'FF' in the solar field is. 1. 2. 3. 4.

Form factor. Fill factor. Face factor. Fire factor.

Answer: Fill Factor. Solution: FF stands for fill factor. It is the ratio of the maximum obtainable power to the product of the open circuit voltage and short circuit current. Q. 22 Calculate fill factor using the data: Pmax=15 W, Voc=18 V, Isc=4 A. 1. 2. 3. 4.

0.65 0.59 0 .20 0.98

Answer: 0.20

Solution: Fill factor is the ratio of the maximum obtainable power to the product of the open-circuit voltage and short circuit current. FF=Pmax÷(Voc×Isc)=15/72=0.20 Q. 23 The output of solar cell is of the order of. 1. 2. 3. 4.

1 W. 5 W. 10 W. 20 W.

Answer: 1W. Q. 24 The voltage of a single solar cell is. 1. 2. 3. 4.

0.2 V. 0.5 V. 1.0 V. 2.0 V.

Answer: 0.5V. Q. 25 A house has appliances of 3 numbers of LED bulbs of each 5W and 2 numbers of ceiling fans of each 70W. What is the total power of their house appliances? 1. 2. 3. 4.

70 W. 155W. 15W. 140W.

Answer : 155 W. Solution : Total power of house =(3x5W)+(2x70W) =15W+140W =155W. Q. 26 What is the unit of 'energy'? 1. Volt.

2. Watt-hour. 3. Watt. 4. Ampere. Answer : Watt-hour. Solution : Energy = Power x time Unit of energy = Unit of power x unit of time Unit of energy = W x h = Wh. Q. 27 A fan of power 50W is used 8 hours per day and a TV of power 40W is used 6 hours per day. What is the energy consumption of a fan and TV per month of 30 days. 1. 2. 3. 4.

640Wh. 12000Wh. 7200Wh. 9200Wh.

Answer : 19200 Wh. Solution : Energy consumption for 1 day = Power x Time Energy consumption for 1 day = (50W x 8h)+(40W x 6h) = 400 Wh + 240 Wh =640Wh Energy consumption for 30 days = 640 Wh x 30 = 19200 Wh Q. 28 Can we can run load directly through solar panel. 1. True. 2. False. Answer :Yes by matching voltage & current of the solar panel and load. Solution : Voltage and current both are important components to run various loads directly through solar energy. Q. 29 If the storage of the medium is electricity grid and battery, the solar system is called.

1. 2. 3. 4.

Off-grid system. Hybrid system. On-grid system. None of these.

Answer : Hybrid system. Solution : If the storage of the medium is electricity grid and battery, the solar system is called hybrid system. In this type of system, we can give extra generated electricity units to the grid or can store the electricity in battery and can use them as and when required. Q. 30 Can '250 Wp ' solar panel available in the market? 1. True. 2. False. Answer : True. Solution : 250 Wp solar panel is available in the market. Q. 31 A solar panel has a Vm of 17.2V and Im of 2.32A. What is the power of the solar panel? 1. 2. 3. 4.

40 Wp 19.52 Wp 17 Wp 2 Wp

Answer : 40 Wp Solution : Power = Voltage x current = Vm x Im = 17.2V x 2.32A = 39.9VA = 39.9W ~ 40W Q. 32 The life of the solar panels is. 1. 5 Years.

2. 10 Years. 3. 25 Years. 4. 15 Years. Answer : 25 years. Solution : The life of the solar panels is 25 years. Most of the solar panel manufacturer today also gives the performance warranty of 25 years. Q. 33 The requirement of the house is 2 kW and the efficiency of the solar panel is 18%. Total solar panel installation area =..... 1. 2. 3. 4.

6.66 square meter. 11.11 square meter. 10 square meter. 20 square meter.

Answer : 11.11 square meter. Solution : If the efficiency of solar panel is 18% then the solar module will produce 180W per square meter. Total solar panel installation area = 2 kW/180W per square meter = 2000W/180W per square meter = 2000/180 square meter = 11.11 square meter Q. 34 Four batteries of 12V, 200Ah are connected in series. What will be the energy stored in the battery? 1. 2. 3. 4.

4.8 kWh 9.6 kWh 2.4 kWh 960Wh

Answer : 9.6 kWh Solution : Energy stored in the battery = Power x time x no. of batteries = Voltage x ampere x hour x nos. = 12 V x 200Ah x 4Nos.

= 9600 VAh = 9600 Wh = 9.6 kWh Q. 35 Two commonly used technologies in batteries are. Answer : Lead acid batteries, lithium ion batteries. Solution : Two commonly used technologies in batteries are lead-acid batteries, lithium-ion batteries. Q. 36 If the actual requirements of a house is 1200Wh & DoD is 50% then how much energy we need to store in the battery? 1. 2. 3. 4.

1.2kWh 2.4kWh 4.8kWh 0.6kWh

Answer : 2.4 kWh Solution : Useful energy = Storage capacity of battery x DoD Storage capacity of battery = Useful energy/DoD = 1200 Wh/50% = 1200 Wh/0.5 = 2400 Wh = 2.4 kWh Q. 37 Role of electronic management for the battery is. Answer : Protect battery from overcharge and full discharge. Solution : The role of electronic management for the battery is to protect battery from overcharge and discharge. The battery is a very delicate part of the solar system and it has to be managed well. Q. 38 The efficiency of the charge controller is. Answer : 85% to 90%. Q. 39 A charge controller maximum input is 12V and 5A. Its maximum output is 6V and 9A. What is the efficiency of the charge controller? Answer : 90%. Solution : The efficiency of charge controller = Output/input = (6V x 9A)/(12V x 5A) = 54VA/60VA

= 0.9 = 90% Q. 40 The efficiency of DC Motor is. Answer : 85% to 95%. Q. 41 Solar radiation is represented in. Answer : kWh/m2/day. Solution : Solar radiation is radiant energy emitted by the sun from a nuclear fusion reaction that creates electromagnetic energy. Solar radiation is represented in kWh/m2/day. Q. 42 The solar panel installation angle is the same for all locations. Answer : False. Solution : The solar panel installation angle is not the same for all locations. It changes as per the latitude of the location. Q. 43 The cost of the DC appliances solar system is more than the AC appliances solar system. Answer : False. Solution : The cost of the DC appliances solar system is less than the AC appliances solar system. As the energy consumption of DC appliances is less than that of AC appliances it requires less quantity of solar panels and battery. And hence the overall cost of the system in the DC appliances solar system is less than the cost of the system in the AC appliances solar system. Q. 44 If a house requires AC load daily energy is 1 kWh. Inverter losses are 15% and battery DoD is 50% what is the battery energy required. Answer : 2.3 kWh Solution : AC load = 1 kWh per day Inverter losses = 15% Loss at inverter = 15% of 1 kWh = 0.15 kWh Output from battery = 1 + 0.15 = 1.15 kWh Battery capacity = Output from battery/DoD = 1.15/50% = 1.15/0.5 = 2.3 kWh

Q. 45 Calculate the battery energy and solar panel power required for the DC loads of 500 Wh per day. Battery DoD is 80%, battery losses are 15%, controller losses are 5%, inverter losses are 15%, solar radiation is 5.25 kWh/m2/day, solar panel losses are 25%. 1. 2. 3. 4.

718 Wh, 165 W 656 Wh, 150 W 1050 Wh, 150 W 1150 Wh, 165 W

Answer : 656Wh, 150W Solution : DC Load = 500Wh per day Charge controller losses at load side = 5% of 500Wh = 25Wh Battery output = 500 + 25 = 525Wh Battery capacity = Battery output/DoD = 525/80% = 525/0.8 = 656.25Wh Battery losses = 15% of 525Wh = 78.75Wh Input for battery = 525 + 78.75 = 603.75Wh Charge controller losses at panel side = 5% of 603.75Wh = 30.19Wh Output from solar panel = 603.75 + 30.19 = 633.94Wh Losses at panel = 25 % of 633.94Wh = 158.48Wh Input at panel = 633.94 + 158.48 = 792.42Wh Solar radiation = 5.25 kWh/m2/day Solar panel requirement = Input at panel/sunshine hours =792.42/5.25=150.93W~150W Q. 46 Calculate the solar panel size in watt, battery in kWh and charge controller in watt for the following appliances. Consider losses are 5% controller losses, 80% battery DoD, 15% battery losses, 25% solar panel losses, solar radiation is 5 kWh/m2/day appliances: bulb (4 Nos. of 10 W running for 5 hours), fan (2 Nos. of 25 W running for 12 hours), TV (1 No. of 20 W running for 6 hours). 1. 2. 3. 4.

580W, 1.2kWh, 120W 290W, 0.6kWh, 60W 290W, 1.2kWh, 120W 120W, 0.966, 120W

Answer : 290W, 1.2 kWh, 120W Solution : Total load of appliances =Nos of appliances x Power rating of appliance x Running hours =(4x10x5)+(2x25x12)+(1x20x6) = 920 Wh/day Total Load = 920 Wh per day Charge controller losses at load side = 5% of 920 Wh = 46 Wh Battery output = 920 + 46 = 966 Wh Battery capacity = Battery output/DoD = 966 / 80% = 966 / 0.8 = 1207.5 Wh = 1.2 kWh Battery losses = 15% of 966 Wh = 145 Wh Input for battery = 966 + 145 = 1111 Wh Charge controller losses at panel side = 5% of 1111 Wh = 55.55 Wh Output from solar panel = 1111 + 55.55 = 1166.55 Wh Losses at panel = 25 % of 1166.55 Wh = 291.64 Wh Input at panel = 1166.55 + 291.64 = 1458.19 Wh Solar radiation = 5 kWh/m2/day Solar panel requirement = Input at panel/sunshine hours = 1458.19/5= 291.63W ~ 290W Size of charge controller = {Nos of appliances x Power rating of appliances} = (4x10)+(2x25)+(1x20) = 110W Charge controller capacity should be little higher than the requirement so the capacity can be taken as 120 W. Q. 47 How much solar energy reaches the earth's surface at any given moment? 1. 2. 3. 4.

173 terawatts. 1.73 terawatts. 17,300 terawatts. 173,000 terawatts.

Answer: 173,000 terawatts. Solution: Solar energy is the most abundant energy source on the planet. Enough sunlight hits the Earth's surface in 1.5 hours to power the entire world's electricity consumption for a year!

Q. 48 Solar cells are made from bulk materials that are cut into wafer of..... thickness. 1. 2. 3. 4.

120-180μm 120-220μm 180-220μm 180-240μm

Answer: 180-240μm Solution: Solar cells are made from the bulk materials that are cut into wafers of thickness 180-240μm. Many currently available cells are cut into wafers. Q. 49 .......photo voltaic devices in the form of thin films. 1. 2. 3. 4.

Cadmium Telluride. Cadmium oxide. Cadmium sulphide. Cadmium sulphate.

Answer: Cadmium Telluride. Solution: Cadmium telluride is the photo voltaic devices in the form of thin films. Those are used to absorb and convert the sun light into electricity. Q. 50 .....is a direct band gap material. 1. 2. 3. 4.

Copper Indium Gallium Selenide Copper Selenide Copper Gallium Telluride Copper Indium Gallium Diselenide

Answer: Copper Indium Gallium Selenide Solution: Copper Indium Gallium Selenide is a direct band gap material. It has the highest efficiency among the film materials. The efficiency is about 20%. Q. 51 Dye-sensitized solar cells are made from..........organic dye.

1. 2. 3. 4.

Ruthium melallo Aniline Safranine Induline

Answer: Ruthium melallo Solution: Dye-sensitized solar cells are made from Ruthium melallo organic dye in the form of mono layer of light absorbing material and mesoporous layer of nano particles. Q. 52 Quantum dot solar cells are based on...... 1. 2. 3. 4.

Gratzel cell Solar cell Voltaic cell Galvanic cell

Answer: Gratzel cell Solution: Quantum dot solar cells are based on the Gratzel cell or dye sensitized solar cell. In dye-sensitized solar cell the nano particulate is titanium dioxide that amplifies the surface area greatly. Q. 53 The quantum dot used are....... 1. 2. 3. 4.

Cds CdTe PbO GaAs

Answer: Cds Solution: The quantum dot used is generally is Cds. The other quantum dots that are used is cadmium selluroide, PbS etc. Q. 54 Organic polymer solar cells are made from Polyphenylene. 1. True 2. False

Answer: True Solution: Organic polymer solar cells are made from organic semi conductors. Some of them are Polyphenylene, Vinylene, Carbon fullerenes. Q. 55 In real case, the charging current for 200Ah battery would be....? 1. 2. 3. 4.

20-22 A 14-16 A 12-14 A 10-12 A

Answer: 20-22A Solution: Charging current should be 10% of the Ah (Ampere hour) rating of battery. Therefore, Charging current for 200Ah battery would be = 200Ah x (10/100) = 20A. But due to losses, the charging current for 200Ah battery should be 20-22A. Q. 56 In real case, the charging time for 200Ah battery would be.......? 1. 2. 3. 4.

5 hours 10 hours 11 hours 12 hours

Answer: 11 hours Solution: Suppose for 200 Ah battery, First of all, we will calculate charging current for 200 Ah battery. As we know that charging current should be 10% of the Ah rating of battery. So charging current for 200Ah Battery = 200 x (10/100) = 20 Amperes. But due to the losses, we can take 20-22 Amperes for charging purpose. suppose we took 22 Amp for charging purpose, Then charging time for 200Ah battery = 200/22 = 9.09 Hrs. But this was an ideal case… Practically, this is noted that 40% of losses ( in case of battery charging) Then 200 x (40/100) = 80 …..(200Ah x 40% of losses) Therefore, 200 + 80 = 280 Ah ( 200 Ah + Losses) Now Charging Time of battery = Ah/Charging Current 28/22 = 12.72 or 12.5 Hrs ( in real case)

Therefore, a 200Ah battery would take 12 Hrs for completely charging (with 22A charging current). Q. 57 The commercial lead acid cell has 13 plates. The number of positive plates would be........... 1. 2. 3. 4.

6 7 8 9

Answer: 6 Solution: The number of negative plates in a lead acid cell is one more than the number of positive plates; the outside plates being negative. So the number of positive plates would be 6. Q. 58 A lead acid cell has 15 plates. In absence of manufacturer’s data, the charging current should be.... 1. 2. 3. 4.

3A 6A 7A 13A

Answer:7A Solution: The charging current for battery should be 1A for every positive plate of a single cell. Also we know that The number of negative plates in a lead acid cell is one more than the number of positive plates; the outside plates being negative. therefore, the number of negative and positive plates would be 8 and 7 respectively. thus, the charging current for this battery would be 7A. Q. 59 A battery is a series or parallel combination of electrolytic cells. 1. True. 2. False.

Answer: True. Solution: An electrolyte cell consists of a positive electrode and a negative electrode separated from each other by an electrolyte. The electrolyte can be concentrated aqueous solutions like acids, alkalis or salts, or ionic conductors like organic salt solutions, polymers, ceramics etc. The electrolyte is a good conductor of ions, but a bad conductor of electrons. Two or more such cells connected together in series or in a series-parallel array forms an assembly called battery. Q. 60 In a single cell, the two electrodes are separated from each other by 1. 2. 3. 4.

1mm. 1cm. 0.5mm. 0.5cm.

Answer: 1mm. Solution: In a single electrolytic cell, the positive electrode and negative electrode have minimum distance between them, about 1mm, so that the internal resistance is as low as possible. Typical value of this resistance is of the order of mill-ohms, so that voltage drops between the electrodes is minimum when drawing huge amount of current Q. 61 A primary dry cell is called so because.. 1. 2. 3. 4.

The electrolyte used is completely dry. The electrolyte used is a moist paste. Dry electrodes are used. None of the above.

Answer: The electrolyte used is a moist paste. Solution: A primary dry cell, also known as Leclanche cell, consists of a moist paste as its electrolyte. The paste is usually mixture of substances like ammonium chloride, manganese dioxide, powdered coke, graphite and water. The paste is contained in a zinc container, which acts as the cathode or the negative electrode. The container is lined with a non- conducting material to separate zinc from the paste.

Q. 62 Specific Gravity of a electrolyte in a single cell or a battery is always.... 1. 2. 3. 4.

Equal to 1.0 Greater than 1.0 Less than 1.0 None of the above

Answer: Greater than 1.0 Solution: Specific gravity of a substance is defined as the ratio of its weight compared to the weight of same amount of pure water. This term is used to determine the amount of active ingredient in an electrolyte, to ensure smooth operation of the cell. Since the electrolyte is a solution of water, the amount of active ingredient cannot be measured directly. Any substance which floats on water will have specific gravity less than that of pure water, i.e. less than 1.0. Since the active ingredient used must sink or dissolve in water, the specific gravity is usually greater than that of pure water, i.e. greater than 1.0. Q. 63 The current in a chemical cell is a movement of 1. 2. 3. 4.

Positive ions only. Positive and negative ions. Negative ions only. Positive hole charges.

Answer: Positive and negative ions. Q. 64 What is C-rating of battery and what does it mean? Answer: C-rating measures how fast a battery can discharge its energy. Higher the C-rating the faster the power can leave the battery to turn motors, power a light bulb etc. Some electronics can use batteries with lower Crating(most flashlight, radios, remote control etc.) while others need high Crating batteries(electric vehicles, drones etc.) The C-rating number is the number of times the battery can discharge in one hour without overheating or damaging the battery. For example, a battery with 1C can discharge its entire capacity in 1 hour, while 6C battery can in 10 minutes, 10C battery can in 6 minutes.

In solar PV system we generally use 10C rating batteries.

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