Contents1. Introduction1.1 About the Book1.2 PV overview and history1.3 SPV at CEL1.2 Why Solar?1.3 Energy Requirements1.4 Demystify the Myths1.5 Characteristics of Solar Energy1.5.1 Solar energy an outline1.5.2 Cost effectiveness1.5.3 External costs of conventional electricity generation

2. Solar Energy Solutions and Systems2.1 Applications of solar energy as a renewable source2.1.1 Solar thermal energy2.1.2 Solar photovoltaic energy2.2 Insolation spread2.3 Capturing and harnessing Solar Energy2.1.1 Solar photovoltaic effect2.1.2 Solar cell2.1.3 Balance of systems2.4 Types of PV systems2.4.1 Stand-alone systems2.4.2 Grid Connected Systems2.5 Operation

3 System Components3.1 Photovoltaic system components3.2 The Solar panel3.2.1 Types of Modules3.2.2 Solar panel parameters3.3 Battery3.3.1 Battery Bank3.3.2 Types of Batteries3.3.3 Temperature effect3.4 Power charge regulator3.5 Converter3.5.3 DC-DC converter3.5.4 DC-AC converter3.5.5 Additional features of inverter3.6 Equipment or Load3.7 Power conditioning unit3.8 Junction Boxes3.9 Wiring3.10 Balance of system standards

4 Design4.1 Introduction and basic principles4.2 System type selection4.3 Home Appliances4.4 Illustration and Flowchart for design of habitat PV system4.5 Design process4.5.1 Load estimation4.5.2 Inverter rating4.5.3 Daily energy supplied by the inverter4.5.4 System voltage4.5.5 Battery capacity4.5.6 Consider for battery autonomy4.5.7 Daily energy generated by panels4.5.8 Solar radiation, capacity and number of panels4.6 Wire sizing4.7 Factors affecting performance of a PV system

5. Installation and commissioning5.1 Safety5.1.1 Electrical5.1.2 Chemical5.1.3 Handling5.1.4 Points to check before wiring.5.1.5 Points to check when selecting the installation location5.2 Assembly5.2.1 Configuration5.2.2 Mounting5.2.3 Connection5.3 Battery5.3.1 Site5.3.2 Connection5.3.3 Earthing5.4 Control Equipment5.4.1 Inverter connections5.4.2 Wiring5.5 System Commissioning5.5.1 Visual Check5.5.2 Connections5.5.3 Testing output of solar panel5.5.4 Applying Power5.5.5 Recommissioning5.6 Parts and Tools5.6.1 Standard parts5.6.2 Roof tile parts5.6.3 Measurement5.6.4 Tool kit

6. Application6.1 Habitat application6.1.1 Solar lanterns6.1.2 Domestic Habitat lighting and fan6.1.3 Outdoor and street lighting6.1.4 Water pumping6.2 Industrial application6.2.1 ONGC offshore power6.2.2 Low power TV transmitter6.2.3 Obstruction warning light at airport6.2.4 Railway signalling(supplementary power)6.2.5 Telecom towers6.3 Defence Use6.3.1 Lightweight foldable solar charger for Manpack Radio Equipment6.3.2 Lightweight foldable solar charger for Manpack WirelessCommunication Equipment SCU-01

7. Maintenance and Troubleshooting7.1 Light units not glowing and no low battery indication on charge controller7.2 No charging indication on the charge controller7.3 Low duration7.4 Incident switch off7.5 Breakage7.6 Lamp flickering7.7 Lamp semi glow7.8 Lamp blackening7.9 No indication7.10 Water entry or insect entry

List of figureFig.1.1 SPV module for unmanned offshore applicationsFig.1.2 SPV module with screen printed liquid cast encapsulation techniqueFig.1.3 SPV modules of different types of solar cellsFig. 1.4 SPV modules during 90s with increased efficiencyFig. 1.5 mono crystalline SPV moduleFig.1.6 Solar insulation over IndiaFig. 1.7 Indias energy balance India has had a negative energy balance for decades Which has forced the purchase of energy from outside the country?Fig: 1.8 Energy consumption in power sector (2005)Fig: 1.9 Per capita Residential Electricity demand (kWh/per person)Fig 1.10 Indias electricity use breakdown in commercial and residential buildingsFig 1.11 Actual power production capacity of a solar PV systemFig 1.12 sustainable energy solutionFig 1.13 Various layouts for panel grafting on urban households.Fig 1.14 Evolution of competitive solar technology.Fig 1.15 Azure Power's 2-megawatt photovoltaic plant in the state of PunjabFig 1.16 A 5-megawatt solar photovoltaic power plant has been installed at village Rawara, Taluka Phalodi, in RajasthanFig. 2.1 An example of a solar water heating system (antifreeze is used so that the Liquid does not freeze if outside temp. drops below freezing)Fig 2.2 Electricity in a typical solar cellFig 2.3 Process of production of electricity in a solar power plantFig 2.4: 10-MW solar power plant in Barstow, California.Fig 2.5 Solar radiation map of IndiaFig 2.6: Flow of energy in a solar PV systemFig 2.7(a) p-n junction silicon semiconductorFig 2.7(b) A solar cell connected to an ammeter showing a deflection when exposed to light.Fig 2.8: photovoltaic solar cell to photovoltaic solar arrayFig 2.9 A PV system showing the balance of componentsFig 2.10 A Lead Acid batteryFig 2.11(a) Discharging process of a lead acid batteryFig 2.11(b) Charging process of a lead acid batteryFig 2.12 Nickel Cadmium BatteryFig 2.13 Charge ControllerFig 2.14 Solar invertersFig 2.15(a): A circuit diagram of solar installation with DC and AC loadsFig 2.15(b) Flow chart of a stand-alone systemFig 3.1: A basic solar PV system.Fig 3.2: A working model of the basic solar PV system at CELFig 3.3: The connection of cells to form a solar panel.Fig 3.4: Different IV Curves. The current (A) changes with the irradiance, and the voltage (V) changes with the temperature.Fig 3.5: The different components of a solar panel.Fig 3.6: The solar panel parameters and their role in efficiency calculation.Fig 3.7: Interconnection of panels in parallel. The voltage remains constant while the current duplicates.Fig 3.8: A 24V, 150Ah battery interconnection at CEL.Fig 3.9: The specifications of a Valve Regulated Lead Acid Battery.Fig 3.10: The specifications of Rechargeable Lead Acid Tubular Positive Plate Battery.Fig 3.11: Circuit diagram of a charge controller.Fig 3.12: A realization of the inverter with a transformer with a movable switch and a current source.Fig 3.13: The output achieved from the inverter with the subsequent harmonics.Fig 3.14: A Single phase transistor bridge inverterFig 3.15: 500 kW, 3 phase inverterFig 3.16: The components of a power conditioning unit.Fig 3.17: The cable requirementsFig 3.18: A three-panel solar array diagram.Fig 3.19: A directly connected solar power dc pump diagram.Fig 3.20: Battery-backed solar powerdriven dc pump.Fig 3.21: Stand-alone hybrid solar power system with standby generator.Fig 3.22: Grid-connected hybrid solar power system with standby generator.Fig 4.1: Indias first two megawatt grid connected project, commissioned in the state of West Bengal in east India.Fig 4.2: Some of the appliances which can be run by solar PV systemFig 4.3 Series and parallel connection of batteries to supply the required energy to the load considering 2 days autonomyFig 4.4: Series and parallel connection of PV modules with their ratings that are required to supply the energy to the load.Fig 4.5 Complete design of solar PV system to fulfill the required load as described in the exampleFig 4.6: Suns path during summer and winterFig 4.7: The effect of temperature on the IV characteristics of a solar cell.Fig 4.8: Solar panels with dirt and dust settled on itFig 4.9: Amorphous solar panelFig 4.10 Polycrystalline solar cellFig 4.11 Mono crystalline solar cellFig 5.1: Chemical handling apparatusFig 5.2 PV module safetyFig 5.3 Examples of poor roof conditionFig 5.4 Azimuthal angleFig 5.5: Wind pressureFig 5.6 A schematic diagram of the proposed system.Fig 5.7 Module MountingFig 5.8: picture of EXIDE solar batteryFig 5.9 Schematics showing electrical connectionsFig 5.10: Picture of a charge controllerFig 5.11: Inverter for 1MegaWatt power station

List of flowchart

Flowchart 1.1: Technology & types of PV cell.Flowchart 2.1: the processes involved in the production of a solar cellFlowchart 2.2 Flow chart of a grid tied systemFlowchart 2.3 operation with AC & DC loadFlowchart 4.1: design of habitat PV systemFlowchart 5.1 an overview of the entire process of installation of solar panelsFlowchart 5.2: Going ahead with installation of PV systemFlowchart 5.3 Creating a Stand-Alone MountFlowchart 5.4 Roof MountingFlowchart 5.5 making electrical wiring connectionsFlowchart 5.6: Inverter connectionsFlowchart 5.7 testing process flow

List of table

Table 1.1 Conversion efficiencies of various PV module technologiesTable 1.2: Overview of the usage of SPV systems in IndiaTable 3.1: The BoS items / components with BIS Standards specificationsTable 4.1 Power rating of some home appliancesTable 4.2 illustrative habitat appliance use in a dayTable 4.3: Calculation of load in Watt-hrTable 4.4: Illustrative power (watt) use per dayTable 4.5: Tilt angle as per geographic latitude

1. Introduction

1.2 PV overview & historyPV cells are made of light-sensitive semiconductor materials that use photons to dislodge electrons to drive an electric current. There are two broad categories of technology used for PV cells, namely- Crystalline silicon, as shown which accounts for the majority of PV cell production; Thin film, which is newer and growing in popularity.

The family tree gives an overview of these technologies available today. The type of silicon that comprises a specific cell, based on the cell manufacturing process. Each cell type has pros and cons. Mono-crystalline PV cells are the most expensive and energy intensive to produce but usually yield the highest efficiencies. The modules made from Polycrystalline silicon crystals are approximately 14% efficient and are extremely good value for money. Amorphous solar modules are not too susceptible to shading and are suited to low light levels.

Crystalline Silicon Technologies: Crystalline cells are made from ultra-pure siliconraw material such as those used in semiconductor chips. They use silicon wafers thatare typically 150-200 microns (one Fifth of a millimeter) thick.

Thin Film Technologies: Thin film is made by depositing layers of semiconductormaterial barely 0.3 to 2 micrometers thick onto glass or stainless steel substrates. Asthe semiconductor layers are so thin, the costs of raw material are much lower thanthe capital equipment and processing costs.

Conversion Efficiency: Apart from aesthetic differences, the most obvious difference amongst PV cell technologies is in its conversion efficiency

Apart from aesthetic differences, the most obvious difference amongst PV celltechnologies is in its conversion efficiency.

Evolving solar panels in India :The development of solar cells for terrestrial applications was initiated at CEL following Governments decision, in 1975, to mount concerted efforts in its high technology area. CEL has carried out Extensive in-house R&D work spanning a decade for developing the complete technology for the manufacture of silicon solar cells and modules and designing, engineering and operating a pilot plant for production of such cells and modules based on the process technology and production engineering so developed. The activity also so included the development of a whole range of SPV systems and undertaking large volume commercial production, supply, field installation and commissioning of such systems. Starting with processing of 38mm diameter hyper pure silicon wafers using vacuum metallization in 1978, CEL went through an evolutionary development process in terms of both different sizes of cells and the whole range of process technology from making them. It now manufactures, using technology completely developed inhouse, 100mm diameter n+-p junction solar cells starting CZ solar grid silicon wafer and employing low cost techniques of texturization, screen-printed silver metallization, antireflection coating and the state of art lamination technology

Fig.1.1 SPV module for unmanned offshore applications

The ONGC module is a pioneering intrinsically safe double glass module developed specifically for operation in explosion prone environments, such as on the offshore, oil production platforms of ONGC. These are the 1st modules in the world to be certified with Gr.I, Gr.IIA and Gr.IIB by Central Mining Research Station (CMRS), Dhanbad and accepter by international insurers, Lloyds of U.K.

Fig.1.2 SPV module with screen printed liquid cast

Encapsulation technique- The screen printing process for the metallization of silicon solar cells uses the thick film technique giving scope for more automation in manufacturing thereby increasing efficiency and reducing the processing cost to about 60% as compared to the conventional vacuum evaporation technique.

Fig.1.3 SPV modules of different types of solar cells

During 80s CEL has undergone rigorous technological innovation for increasing efficiency and reducing the cost of production of solar cells. The size and structure of solar cells varied, 4 diameter solar cell was introduced, Lamination technology bringing with it automation in manufacturing process.

Fig. 1.4 SPV modules during 90s with increased efficiency

NS POWER demonstrates the importance of entering an area of advanced technology at early stage in the evolution of technology and building indigenous capacity to convert science into technology and further for industrial and domestic use. CEL, working for more than four decades has built up an internationally recognised capability in SPV area of integrating Science, Technology, and Industry.

Fig. 1.5 mono crystalline SPV modulewith its commitment to harness the solar energy, has opened up new vistas in the field of solar photovoltaic. Backed by an integrated production facility to manufacture Mono-Crystalline Silicon Solar Cells and Modules with the state-of-the-art screen-printing technology, the company has supplied more than 1.5 Lakhs SPV Systems in India and abroad, covering both rural and industrial applications.

1.4 Why SOLAR?India is a tropical country, where sunshine is available for longer hours per day and in great intensity. Solar energy, therefore, has great potential as future energy source. It also has the advantage of permitting the decentralized distribution of energy, thereby empowering people at the grassroots level. India is endowed with vast solar energy potential. About 5,000 trillion kWh per year energy is incident over Indias land area with most parts receiving 4-7 kWh per sq. m per day. Theoretically, a small fraction of the total incident solar energy (if captured effectively) can meet the entire countrys power requirements.

Fig.1.6 Solar insolation over IndiaSource: http://www.esri.com/mapmuseumIt is also clear that given the large proportion of poor and energy unserved population in the country, every effort needs to be made to exploit the relatively abundant sources of energy available to the country and it is in this situation the solar imperative is both urgent and feasible to enable the country to meet long-term energy needs and also from an energy security perspective, solar is the most secure of all sources, since it is abundantly available.Hence both technology routes for conversion of solar radiation into heat and electricity, namely, solar thermal and solar photovoltaic, can effectively be harnessed providing huge scalability for solar in India. Solar also provides the ability to generate power on a distributed basis and enables rapid capacity addition with short lead times.

1.5 Energy RequirementsAlmost 400 million Indiansabout a third of the subcontinents populationdont have access to electricity. This power deficit, which includes about 100,000 unelectrified villages, places Indias annual per-capita electricity consumption at just 639 kilowatt hoursamong the worlds lowest rates.Since the 1980s, and still currently, India has encountered a negative balance in overall energy consumption and production. This has resulted in the need to purchase energy from outside the country to supply and fulfil the needs of the entire country. The Government is more sensitive to renewable energy potential and has started to put reforms and projects, incentives and legislation in place to convince investors and companies to make the shift.

Fig. 1.7 Indias energy balance (Source: U.S. Energy Information Administration)

India has had a negative energy balance for decades which has forced the purchase of energy from outside the country.The breakdown of energy sources for power production of India in 2005. India is a large consumer of coal, which makes up more than 57% of its total consumption.

Fig: 1.8 Energy consumption in power sector (2005)(Source: www.presidentofindia.nic.in)India relies heavily on coal energy to produce electricity. A strong second is hydro power, followed by natural gas. The consumption of all renewable energies represents fully one third of the total consumption. India now ranks third amongst the coal producing countries in the world. Being the most abundant fossil fuel in India till date, it continues to be one of the most important sources for meeting the domestic energy needs. It accounts for 55% of the countrys total energy supplies. Through sustained increase in investment, production of coal increased from about 70 MT (million tones) (MoC 2005) in early 1970s to 382 MT in 2004/05. Most of the coal production in India comes from open pit mines contributing to over 81% of the total production while underground mining accounts for rest of the national output(MoC 2005). Despite this increase in production, the existing demand exceeds the supply. India currently faces coal shortage of 23.96 MT. Stressing the need to find new energy sources, a top PSU official said India is likely to run out of its 60-70 billion tonnes of coal reserves by 2040-41 if the demand continues to grow at the present pace.The demand for coal will reach two billion tonnes mark by 2016-17. We need to grow at the rate of 17-18 per cent from the present 6-7 per cent to meet this growing demand, Coal India Ltd (CIL) Chairman Partha S Bhattacharyya said at the ICC Coal Summit.With coal reserves expected to run out in the next 45 years in the country, there is a greater need to switch to renewable sources of energy. Poor quality of power supply and frequent power cuts and shortages impose a heavy burden on Indias fast-growing trade and industry. The access gap is complicated by another problem more than three-quarters of Indias electricity is produced by burning coal and natural gas. With Indias rapidly-growing population currently 1.1 billionalong with its strong economic growth in recent years, its carbon emissions were more than 1.6 billion tons in 2007, among the worlds highest. The only light of hope is the fact that with harnessing of solar energy, the country can generate nearly 50,000 MW of solar power by 2050, the capacity of which could be further enhanced to over 75,000 MW.India has been facing electricity shortages in spite of appreciable growth in electricity generation. The demand for electrical energy has been growing at the faster rate and shall increase at higher growth rate to match with the projected growth of Indian economy.The map shown below shows the individual per capita demand of the individual states of the country.

Fig: 1.9 Per capita Residential Electricity demand (kWh/per person)(Source: CEA, 2009a)The demand is maximum in the states like Tamil Nadu, Kerala, Maharashtra, Gujarat and Rajasthan, the states which account for a major share in the unparalleled solar potential of India.

Fig 1.10 Indias electricity use breakdown in commercial and residential buildings.(Source: Bassi, n.d.)In a typical commercial building in India, it is estimated that about 60% of the total electricity is used for lighting, 32% for space conditioning as well as 8% for heating ventilation and airconditioning.

1.6 Demystifying the Myths1. Myth: Solar is too expensive for widespread usage and will therefore never compete with conventional means of power generation.Facts: The cost of solar technologies has declined every year since they were first introduced onto the market in the 50s The reduction in cost has been driven by improved research and technology, and most of all by steady increases in sales volume. The average growth rate of PV manufacturing in India is 35 percent in the past 3 years Every ton of conventional, non-renewable energy used adds to an overall shortage and therefore makes this kind of energy more expensive to locate and to use Solar on the other hand is a renewable resource and an immense amount of solar energy strikes the Earth's surface every day2. Myth: Solar is not feasible for my energy needs.Facts: India receives solar energy equivalent to more than 5,000 Trillion kWh per year, which is far more than its total annual energy consumption The average solar insolation in India is 4-7 kWh/square meter. The peak power of a solar panel is estimated for 1000W/m2.

(It produces 2.3 kW power enough to operate 10 household lamps of 23W (example) for 10 hours.) The fixed and one time installation cost for 1kW SPV system is a mere amount of Rs2, 70,000* ((INR)(current rate under MNRE for standalone system), where as it will have a lifetime of 30 years with lowest of maintenance cost and one time free battery replacement by CEL**. For grid interactive hybrid SPV system the cost of installation is even a smaller amount of Rs 180* per Watt.(* The rate mentioned is not inclusive of subsidy or any relaxation. Subsidy may vary from state to state as well as in hilly and plain areas)(** Provided CEL is the SPV system installer)3. Myth: Solar systems is not a sustainable solution.Facts:Considering various perspectives individually:1. Self reliance The per capita average annual domestic electricity consumption in India in 2009 was 96 kWh in rural areas and 288 kWh in urban areas for those with access to electricity. The production capacity of solar systems can easily meet the above demands keeping in mind the rich solar potential of India. The average life of a solar system is 25years and hence a cost effective, long run and permanent setup unaffected by the ever changing conventional source market.2. Community upliftment At a fixed capital investment it can generate substantial revenues when setup as a hybrid grid connected system. In field regions, off-grid setups can meet the demands of agro pumping, water heating systems etc.3. National contribution It is a clean energy. It will cut down on the existing 20% of power losses in transmission and distribution by the provision of standalone systems in the rural and isolated areas. It will reduce the pressure on the environment.

All of the above together will build a sustainable solution

Fig 1.12 sustainable energy solution4. Myth: Solar power is not practical in urban areasFacts: Solar energy systems are installed at the point of use eliminating the need to trench underground and dig up asphalt No extra land space is needed making urban installation practical

Fig 1.13 Various layouts for panel grafting on urban households. Solar power systems give off no noise or pollution, making them the ideal renewable energy source in urban areas

5. Myth: Solar is not competitive with the conventional energy market.Facts:I. First generation cells consist of large-area, high quality and single junction devices.

Fig 1.14 Evolution of competitive solar technology.

II. The most successful second generation materials have been cadmium telluride (CdTe), copper indium gallium Selenide, amorphous silicon and micro-morphous silicon. These materials are applied in a thin film to a supporting substrate such as glass or ceramics reducing material mass and therefore costs. These technologies do hold promise of higher conversion efficiencies, particularly CIGS-CIS, DSC and CdTe offers significantly cheaper production costs.III. Third generation technologies aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.There are a few approaches to achieving these high efficiencies: Multi-junction photovoltaic cell (multiple energy threshold devices). Modifying incident spectrum (concentration). Use of excess thermal generation (caused by UV light) to enhance voltages or carrier collection. Use of infrared spectrum to produce electricity at night. Plummeting prices of polysilicon, a raw material used in solar modules, could make power from solar photovoltaic plants as cheap as Rs 5 a unit or less by 2015 against Rs 12 a unit as estimated today.

6. Myth: Solar energy and solar designs work well only in warm, sunny climatesFacts: Solar technologies can work efficiently and cost-effectively anywhere in India, even in cloudy communities

Energy-storage systems make solar technologies in less sunny regions practical Some photovoltaic systems store electricity in batteries so that energy can be retrieved later -- even after up to 30 consecutive days without sunlight

7. Myth: Solar electricity cannot serve any significant fraction of Indian electricity needs.Facts: With about 300 clear, sunny days in a year, India's theoretical solar power reception, on only its land area, is about 5 Petawatt-hours per year (PWh/yr) (i.e. 5 trillion kWh/yr or about 600 TW). The daily average solar energy incident over India varies from 4 to 7 kWh/m2 with about 15002000 sunshine hours per year (depending upon location), which is far more than current total energy consumption Assuming the efficiency of PV modules were as low as 10%, this would still be a thousand times greater than the domestic electricity demand projected for 2015

8. Myth: To collect enough solar energy a business needs to install large arrays of collectors requiring vast land area.Facts: There is sufficient roof space on most businesses to produce the total electricity needed using existing photovoltaic technology.

1.7 Characteristics of Solar Energy1.7.1 Solar Energy- An OutlineA new era for solar power is approaching. Long derided as uneconomic, it is gaining ground as technologies improve and the cost of traditional energy sources rises. Within three to seven years, unsubsidized solar power could cost no more to end customers in many markets, than electricity generated by fossil fuels or by renewable alternatives to solar.i. Indian SPV energy scenario Presently, India have over 17.5 GW (June 2010) of installed renewable energy (Wind =11.8 GW, Small Hydro =2.8 GW, PV installed=15 MW, Rest is mostly Biomass) capacity. Out of this installed PV, the grid tied and off grid tied share are 12.3 MW (less than 0.1% of grid tied renewable energy) and 2.9 MW (0.7% of off grid renewable capacity of India). Although, sun provides 10,000 times more energy, we daily consume and India being a tropical country receives adequate solar irradiance (Daily radiation ~ 4-7 KWh/m2, solar energy received= 5,000 trillion KWh/year, Sunny days/year = 250-300) which is a major driver for the SPV market in the country. Presently, SPV based applications usage in India is not in accordance with that in the global market (Globally, grid-connected PV applications account for 75% while in India it account only ~ 3% of the overall PV applications) as much of the country does not have an electrical grid. Table below shows the different mode of use of SPV systems in India.

India is gradually shifting focus towards its solar energy program as the use and implication of SPV is very low in the country. The Government is striving hard to push the SPV industry by introducing grid based incentives and concessions in various duties in the recent budget (2010-11) to make the country as a global leader. Driven by an increasing demand for electricity, wide gap between demand and supply and pressure to reduce greenhouse gas emission, India has targeted 22 GW (20 GW grid and 2GW off grid tied) of Solar Power by 2022 in its Jawaharlal Nehru National Solar Mission (JNNSM). Out of this, around 50 % will be produced through solar photovoltaic (SPV). Ministry of New and Renewable Energy (MNRE) is aiming to achieve 500 MWp grid-connected SPV capacities by 2017. It is estimated that the Indian solar energy sector will grow at 25% per year in next few years.

ii. Latest steps of Indian Market on the global front are India inaugurated Azure Power's 2-megawatt photovoltaic plant in the state of Punjab, the first privately owned, utility-scale power plant on the Asian subcontinent.

Fig 1.15 Azure Power's 2-megawatt photovoltaic plant in the state of Punjab

Built under a 30-year power purchase agreement with the Punjab State Electricity Board, the plant will help power 4,000 rural homes for 20,000 people. Farooq Abdullah, minister of new and renewable energy, said the plant showcases India's pledge to generate 20,000 megawatts from solar power by 2022 under the country's national solar mission. An Rs 67-crore, 5 megawatt solar photovoltaic power plant has been installed at village Rawara, Taluka Phalodi, in Rajasthan. The project, owned by Indian Oil Corporation, was commissioned by Rajasthan Electronics & Instruments Ltd under the Jawaharlal Nehru National Solar Mission, as stated by Ministry of Heavy Industries.

Fig 1.16 A 5-megawatt solar photovoltaic power plant has been installed at village Rawara, Taluka Phalodi, in Rajasthan

This power plant is designed to feed power to 33/132 kV grid sub-station at village Bap, which is situated 18 km from plant site Rawara. It is expected to generate energy of 67 lakh KWh a year. 1.7.2 Cost Effectiveness The decrease in manufacturing costs and retail prices of PV modules and systems (including electronics and safety devices, cabling, mounting structures, and installation) have come as the industry has gained from economies of scale and experience. This has been brought about by extensive innovation, research, development and ongoing political support for the development of the PV market. Reductions in prices for materials (such as mounting structures), cables, land use and installation account for much of the decrease in BOS costs. Another contributor to the decrease of BOS and installation-related costs is the increase in efficiency at module level. More efficient modules imply lower costs for balance of system equipment, installation related costs and land use. Electricity price evolution Costs for the electricity generated in existing gas and coal-fired power plants are constantly rising. This is a real driver for the full competitiveness of PV. Energy prices are increasing in many regions of the world due to the nature of the current energy mix. The use of finite resources for power generation (such as oil, gas, coal and uranium), in addition to growing economic and environmental costs will lead to increased price for energy generated from fossil and nuclear fuels.

1.7.3 External costs of conventional electricity generationThe external costs to society incurred from burning fossil fuels or nuclear power generation are not currently included in most electricity prices. These costs are both local and, in the case of climate change, global. As there is uncertainty about the magnitude of these costs, they are difficult to quantify and include in the electricity prices. The market price of CO2 certificates remains quite low (around 14/tonne CO2 end of 2010) but is expected to rise in the coming decades.

BENEFITS OF SOLAR ENERGY OVER DISTRIBUTED GRID ENERGY

As a distributed energy resource available nearby load centres, solar energy could reduce transmission and distribution (T&D) costs and also line losses. According to World Resources Institute (WRI), Indias electricity grid has the highest transmission and distribution losses in the world a whopping 27%. Numbers published by various Indian government agencies put that number at 30%, 40%, and greater than 40%. Solar technologies like PV carry very short gestation periods of development and, in this respect, can reduce the risk valuation of their investment. They could enhance the reliability of electricity service when T&D congestion occurs at specific locations and during specific times. By optimizing the location of generating systems and their operation, distributed generation resources such as solar can ease constraints on local transmission and distribution systems. They can also protect consumers from power outages. For example, voltage surges of a mere millisecond can cause brownouts, causing potentially large losses to consumers whose operations require high quality power supply. Moreover, the peak generation time of PV systems often closely matches peak loads for a typical day so that investment in power generation, transmission, and distribution may be delayed or eliminated.

2. Solar Energy Solutions and systems

2.1 Applications of solar energy as a renewable sourceThere are two main applications:2.1.1 Solar thermal energySolar thermal energy (STE) is a technology for harnessing solar energy for thermal energy. Solar collectors capture the energy of the sun and convert it into heat. The basic idea of a solar collector is that the solar energy passes through a layer of glazed glass where it is absorbed by the underlying material resulting in heat. The glazing of the glass prevents heat from escaping, thereby effectively capturing the heat.

Fig. 2.1 An example of a solar water heating system (antifreeze is used so that the liquid does not freeze if outside temp. drops below freezing)

Solar thermal collectors are as low, medium, or high-temperature collectors. Low-temperature collectors are flat plates generally used to heat swimming pools. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use. The applications include solar drying and distillation. High-temperature collectors concentrate sunlight using mirrors or lenses and are generally used for electric power production. STE is different from photovoltaic, which converts solar energy directly into electricity.

2.1.2 Solar Photovoltaic energyPhotovoltaic (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. This is explained in more detail in the following sections.

Fig 2.2 Electricity in a typical solar cell

Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Solar photovoltaic is growing rapidly, albeit from a small base, to a total global capacity of 40 GW (40,000 MW) at the end of 2010.

Fig 2.3 Process of production of electricity in a solar power plantSource: Energy Information Administration: Schott Corporation.

Fig 2.4: 10-MW solar power plant in Barstow, California.

More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (building-integrated photovoltaic).

2.2 Insulation spreadWe receive energy from the sun in the form of solar radiation. Solar panels make use of this radiation to generate electricity. The amount of solar radiation that strikes a single location over a given period of time (usually one day) is called insulation.

Fig 2.5 Solar radiation map of India

As can be seen from the Solar Radiation Map of India - most parts are suitable for generating power from Solar Energy. The most suitable areas are Rajasthan, Gujarat, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Punjab, Haryana, Uttar Pradesh, Uttarakhand, Jharkhand, Tamil Nadu, Orissa, and West Bengal.In general major Geography of Country is suitable for Solar Energy Utilization.

2.3 Capturing and harnessing solar energy

Fig 2.6: Flow of energy in a solar PV system

Fig 2.7(a) p-n junction silicon semiconductor

The photovoltaic effect is the means by which solar panels or photovoltaic modules generate electricity from light. A solar cell is made from a semiconductor material such as silicon. Impurities are added to this to create two layers,i. n-type material, which has too many electrons.ii. p-type material, which has too few electrons.The junction between the two is known as a p-n junction. This process is known as doping.

Fig 2.7(b) A solar cell connected to an ammeter showing a deflection when exposed to light.

Do it yourself: Get p-n junction silicon semiconductor, connect one end of wire to the p-type and n-type. Now connect an ammeter to the other end and complete the circuit and place it in sunlight Light consists of packets of energy called photons. When these photons hit the cell, they are either reflected, absorbed or pass straight through, depending on their wavelength. The energy from those which are absorbed is given to the electrons in the material which causes some of them to cross the p-n junction. If an electrical circuit is made between the two sides of the cell a current will flow. This current is proportional to the number of photons hitting the cell and therefore the light intensity.

2.3.2 Solar cellA solar cell is any device that directly converts the energy in light into electrical energy through the process of photovoltaic. Fig 2.8: photovoltaic solar cell to photovoltaic solar array

The performance of a solar or photovoltaic (PV) cell is measured in terms of its efficiency at converting sunlight into electricity. There are a variety of solar cell materials available, which vary in conversion efficiency. Flowchart 2.1: the processes involved in the production of a solar cell

Solar cell plants like the one in CEL take the wafer through a high technology semiconductor processing sequence to create working solar cells. In c-Si, wafers typically undergo a process sequence of etching, diffusion, and screen printing steps before they are tested and graded for incorporation into modules. The final part of the overall manufacturing process is the solar system assembly and installation. First, an array structure is chosen for the mechanical integration of the solar module. This array structure will depend on the final location of the system, which could involve retrofitting onto a roof, integrating into building materials for roofs or vertical walls, or pole-mounting, ground-mounting, or attaching to an industrial structure.

2.3.3 Balance of systems

Fig 2.9 A PV system showing the balance of componentsIn addition to purchasing photovoltaic panels you will need to invest in some additional equipment (called "balance-of-system") to condition and safely transmit the electricity to the load that will use it The major balance-of-system equipments for systems are:1. BatteriesBatteries accumulate excess energy created by your PV system and store it to be used at night or when there is no other energy input. Batteries can discharge rapidly and yield more current that the charging source can produce by itself, so pumps or motors can be run intermittently. There are two types of batteries;i. Lead Acid Batteriesii. Nickel Cadmium Batteries

i. Lead Acid BatteriesLead Acid Batteries are made of five basic components: A resilient plastic container. Positive and negative internal plates made of lead. Plate separators made of porous synthetic material. Electrolyte, a dilute solution of sulphuric acid and water, better known as battery acid. Lead terminals, the connection point between the battery and whatever it powers.

Fig 2.10 A Lead Acid Battery

1. Discharging process

Fig 2.11(a) Discharging process of a lead acid battery

2. Charging process

2.11(b) Charging process of a lead acid batteryii. Nickel Cadmium Batteries

Fig 2.12 Nickel Cadmium BatterySource: Encyclopedia Britannica, Inc.The Nickel-cadmium battery uses nickel oxide in its positive electrode (cathode), a cadmium compound in its negative electrode (anode), and potassium hydroxide solution as its electrolyte. The Nickel Cadmium Battery is rechargeable, so it can cycle repeatedly. As the battery is discharged, the following reaction takes place:Cd + 2H2O + 2NiOOH > 2Ni(OH)2 + Cd(OH)22. Charge controllerA solar charge controller is needed in virtually all solar power systems that utilize batteries. The job of the solar charge controller is to regulate the power going from the solar panels to the batteries. Overcharging batteries will at the least significantly reduce battery life and at worst damage the batteries to the point that they are unusable.

Fig 2.13 Charge Controller3. InverterThe function of an inverter is to transform the low voltage DC of a lead acid battery into higher voltage AC which may be used to power standard mains appliances. An inverter is necessary where appropriate low voltage appliances are unavailable or expensive or in larger systems where it is necessary to distribute the power over a wide area

Fig 2.14 Solar invertersThe amount of equipment needed depends on what you want the use of the system is. In the simplest systems, the current power generated by is connected directly to the load. However, if the energy is required to be store batteries and charge controller are required. Depending on the needs, balance-of-system equipment could account for half of the total system costs. The system supplier will be able to tell exactly what equipment are needed.

2.4 Types of PV systems2.4.1 Stand Alone systemsThese systems are generally employed where there is no availability of grid power. The system operates autonomously and supplies power to the electrical loads independent of the electric utility. The energy created by the Solar Panel array is stored in batteries. Whenever electricity is a needed, the energy is drawn from batteries.

Figure 2.15(a): A circuit diagram of solar installation with DC and AC loads

Fig 2.15(b) Flow chart of a stand-alone systemThe major balance-of-system equipments for stand-alone systems are: Batteries Charge controller Power conditioning equipment Safety equipment Meters and instrumentation

2.4.2 Grid Connected systemsA grid-connected system powers the home or small business with renewable energy during those periods when the sun is shining. Any excess electricity produced is fed back into the grid. When renewable resources are unavailable, electricity from the grid supplies your needs, thus eliminating the expense of electricity storage devices like batteries.Flowchart 2.2 a grid tied systemIf more electricity is used than the system feeds into the grid during a given month, the difference between what energy used and produced is to be paid.The balance of system components required are: Power conditioning equipment Safety equipment Meters and instrumentation. 2.5 OperationFlowchart 2.3 operation with AC & DC load

The solar modules convert solar energy directly into dc power which can be used directly by dc loads and also by ac loads with the use of an inverter. A battery charges and discharges according to the requirement of the household or establishment.

3. System Components

A basic photovoltaic system consists of five main components:i. solar panelii. Batteriesiii. Regulatoriv. Loadv. converter

The panels are responsible for collecting the energy of the sun and generating electricity.The battery stores the electrical energy for later use. The regulator ensures that panel and battery are working together in an optimal fashion. The load refers to any device that requires electrical power, and is the sum of the consumption of all electrical equipment connected to the system. It is important to remember that solar panels and batteries use direct current (DC).If the range of operational voltage of your equipment does not fit the voltage supplied by your battery, it will also be necessary to include some type of converter. If the equipment that you want to power uses a different DC voltage than the one supplied by the battery, you will need to use a DC/DC con-verter. If some of yourequipment requires AC power, you will need to use a DC/AC converter, also known as an inverter. Every electrical system should also incorporate various safety devices in the event that something goes wrong. These devices include proper wiring, cir-cuit breakers, surge protectors, fuses, ground rods, lighting arrestors, etc.

3.1 Photovoltaic system components

When all of the components are in balance and are properly maintained, the system will support itself for years.

Fig 3.1: A basic solar PV system

Fig 3.2 : A working model of the basic solar PV system at NS POWER.

3.2 The solar panelAn individual solar panel is made of many solar cells. The cells are electrically connected to provide a particular value of current and voltage. The individual cells are properly encapsulated to provide isolation and protection from humidity and corrosion.

Fig 3.3 : The connection of cells to form a solar panel.

There are different types of modules available on the market, depending on the power demands of your application. The most common modules are composed of 32 or 36 solar cells of crystalline silicon. These cells are all of equal size, wired in series, and encapsulated between glass and plastic material, using a polymer resin (EVA) as a thermal insulator. The surface area of the module is typically between 0.1 and 0.5 m2. Solar panels usually have two electrical contacts, one positive and one negative. Some panels also include extra contacts to allow the installation of bypass diodes across individual cells. Bypass diodes protect the panel against a phenomenon known as hot-spots. A hot-spot occurs when some of the cells are in shadow while the rest of the panel is in full sun. Rather than producing energy, shaded cells behave as a load that dissipates energy. In this situa-tion, shaded cells can see a significant increase in temperature (about 85 to 100C.) Bypass diodes will prevent hot-spots on shaded cells, but reduce the maximum voltage of the panel. They should only be used when shading is unavoidable. It is a much better solution to expose the entire panel to full sun whenever possible.

Fig 3.4 : Different IV Curves.

The current (A) changes with the irradiance, and the voltage (V) changes with the temperature. The electrical performance of a solar module it represented by the IV characteristic curve, which represents the current that is provided based on the voltage generated for a certain solar radiation. The curve represents all the possible values of voltage-current. The curves depend on two main factors: the temperature and the solar radiation received by the cells. For a given solar cell area, the current generated is directly proportional to solar irradiance (G), while the voltage reduces slightly with an increase of temperature. A good regulator will try to maximize the amount of energy that a panel provides by tracking the point that provides maximum power (V x I). The maximum power corresponds to the knee of the I-V curve.

3.2.1 Types of modules

Fig 3.5 : The different components of a solar panel.

Various module classifications are used commercially. The general term 'module' (or panel) is defined more precisely by highlighting the module's specific qualities.Modules can be classified according to:

Cell type:- Mono-crystalline modules;- Polycrystalline modules;- Thin-film modules (amorphous, CdTe and CIS modules). Encapsulation material:- Teflon modules;- PVB modules;- resin modules (the EVA classification module is not generally used). Encapsulation technology:- Lamination (with EVA, PVB or Teflon; see the following section on 'Laminates'). Substrate:- Film modules;- Glass-film modules (or glass-Tedlar modules);- Metal-film modules;- Acrylic plastic modules;- Glass-glass modules. Frame structure:- Framed modules;- Frameless modules. Construction-specific additional functions:- Toughened safety glass (TSG) modules;- Laminated safety glass (LSG) modules;- Insulating glass modules;- Insulating glass modules for overhead glazing;- Stepped insulating glass modules;- Laminated glass modules.

3.2.2 Solar Panel Parameters

Fig 3.6 : The solar panel parameters and their role in efficiency calculation.

Note:- The panel parameters values change for other conditions of irradiance and temperature. Manufacturers will sometimes include graphs or tables with values for conditions different from the standard. You should check the performance values at the panel temperatures that are likely to match your particular installation. Panel parameters for system sizing To calculate the number of panels required to cover a given load, you just need to know the current and voltage at the point of maximum power: IPmax and VPmax. You should assume a loss of efficiency of 5% in your calculations to compensate for the inadequacy of the panel to work at the maximum power point at all the times.

Interconnection of panelsA solar panel array is a collection of solar panels that are electrically inter-connected and installed on some type of support structure. Using a solar panel array allows you to generate greater voltage and current than is possible with a single solar panel. The panels are interconnected in such a way that the voltage generated is close to (but greater than) the level of voltage of the batteries, and that the current generated is sufficient to feed the equipment and to charge the batteries. Connecting solar panels in series increases the generated voltage. Connecting panels in parallel increases the current. The number of panels used should be increased until the amount of power generated slightly exceeds the demands of your load. It is very important that all of the panels in your array are as identical as possible. In an array, you should use panels of the same brand and characteristics because any difference in their operating conditions will have a big impact on the health and performance of your system.

Fig3.7: Interconnection of panels in parallel. The voltage remains constant while thecurrent duplicates.3.3 The batteryThe battery hosts a certain reversible chemical reaction that stores electrical energy that can later be retrieved when needed. Electrical energy is transformed into chemical energy when the battery is being charged, and the reverse happens when the battery is discharged. A battery is formed by a set of elements or cells arranged in series. For example, Lead acid batteries consist of two submerged lead electrodes in an electrolytic solution of water and sulfuric acid. A potential difference of about 2 volts takes place between the electrodes, depending on the instantaneous value of the charge state of the battery. The most common batteries in photovoltaic solar applications have a nominal voltage of 12 or 24 volts. A 12 V battery therefore contains 6 cells in series.

The battery serves two important purposes in a photovoltaic system: To provide electrical energy to the system when energy is not supplied by the array of solar panels, and To store excess energy generated by the panels whenever that energy exceeds the load.The battery experiences a cyclical process of charging and discharging, depending on the presence or absence of sunlight. During the hours that there is sun, the array of panels produces electrical energy. The energy that is not consumed immediately it is used to charge the battery. During the hours of absence of sun, any demand of electrical energy is supplied by the battery, thereby discharging it. These cycles of charge and discharge occur whenever the energy produced by the panels does not match the energy required to support the load. When there is sufficient sun and the load is light, the batteries will charge. Obviously, the batteries will discharge at night whenever any amount of power is required. The batteries will also discharge when the irradiance is insufficient to cover the requirements of the load (due to the natural variation of climatological conditions, clouds, dust, etc.)3.3.1 Battery Bank (A CEL Standard)

3.3.2 Types of batteries

Many different battery technologies exist, and are intended for use in a variety of different applications. The most suitable type for photovoltaic applications is the stationary battery, designed to have a fixed location and for scenarios where the power consumption is more or less irregular. "Stationary" batteries can accommodate deep discharge cycles, but they are not designed to produce high currents in brief periods of time. Stationary batteries can use an electrolyte that is alkaline (such as Nickel-Cadmium) or acidic (such as Lead-Acid). Stationary batteries based on Nickel-Cadmium are recommended for their high reliability and resistance whenever possible. Unfortunately, they tend to be much more expensive and difficult to obtain than sealed Lead-Acid batteries. Mounting Valve Regulated Lead Acid (VRLA) Rechargeable Lead Acid Tubular Positive Plate accelerates, which can cause the same type of oxidation that takes places during overcharging. This will obviously reduce the life expectancy of battery. This problem can be compensated partially in car batteries by using a low density of dissolution (a specific gravity of 1.25 when the battery is totally charged). As the temperature is reduced, the useful life of the battery increases. But if the temperature is too low, you run the risk of freezing the electrolyte. The freezing temperature depends on the density of the solution, which is also related to the state of charge of the battery. The lower the density, the greater the risk of freezing. In areas of low temperatures, you should avoid deeply discharging the batteries (that is, DoDmax is effectively reduced.) The temperature also changes the relation between voltage and charge. It is preferable to use a regulator which adjusts the low voltage disconnect and reconnect parameters according to temperature. The temperature sensor of the regulator should be fixed to the battery using tape or some other simple method. In hot areas it is important to keep the batteries as cool as possible. The batteries must be stored in a shaded area and never get direct sunlight. It's also desirable to place the batteries on a small support to allow air to flow under them, thus increase the cooling.

3.4 The power charge regulatorThe power charge regulator is also known as charge controller, voltage regulator, charge-discharge controller or charge-discharge and load controller. The regulator sits between the array of panels, the batteries, and your equipment or loads. Significance - Remember that the voltage of a battery, although always close to 2 V per cell, varies according to its state of charge. By monitoring the voltage of the battery, the regulator prevents overcharging or over discharging. Regulators used in solar applications should be connected in series: they disconnect the array of panels from the battery to avoid overcharging, and they disconnect the battery from the load to avoid over discharging. The connection and disconnection is done by means of switches which can be of two types: electromechanical (relays) or solid state (bipolar transistor, MOSFET).Regulators should never be connected in parallel.In order to protect the battery from gasification, the switch opens the charging circuit when the voltage in the battery reaches its high voltage disconnect (HVD) or cut-off set point. The low voltage disconnect (LVD) prevents the battery from over discharging by disconnecting or shedding the load. To prevent continuous connections and disconnections the regulator will not connect back the loads until the battery reaches a low reconnect voltage (LRV). The most modern regulators are also able to automatically disconnect the panels during the night to avoid discharging of the battery. They can also periodically overcharge the battery to improve their life, and they may use a mechanism known as pulse width modulation (PWM) to prevent excessive gassing.As the peak power operating point of the array of panels will vary with temperature and solar illumination, new regulators are capable of constantly tracking the maximum point of power of the solar array. This feature is known as maximum power point tracking (MPPT).

Circuit implementation

Fig 3.11: Circuit diagram of a charge controller.Regulator Parameters When selecting a regulator for your system, you should at least know the operating voltage and the maximum current that the regulator can handle. The operating Voltage will be 12, 24, or 48 V. The maximum current must be 20% bigger than the current provided by the array of panels connected to the regulator.

Other features and data of interest include: Specific values for LVD, LRV and HVD. Support for temperature compensation. The voltage that indicates the state of charge of the battery vary with temperature. For that reason some regulators are able to measure the battery temperature and correct the different cut-off and reconnection values.

Instrumentation and gaugesThe most common instruments measure the voltage of the panels and batteries, the state of charge (SoC) or Depth of Discharge (DoD). Some regulators include special alarms to indicate that the panels or loads have been disconnected; LVD or HVD has been reached, etc.

3.5 ConvertersThe regulator provides DC power at a specific voltage. Converters and inverters are used to adjust the voltage to match the requirements of your load.

3.5.1 DC/DC Converters DC/DC converters transform a continuous voltage to another continuous voltage of a different value. There are two conversion methods which can be used to adapt the voltage from the batteries: linear conversion and switching conversion. Linear conversion lowers the voltage from the batteries by converting excess energy to heat. This method is very simple but is obviously inefficient. Switching conversion generally uses a magnetic component to temporarily store the energy and transform it to another voltage. The resulting voltage can be greater, less than, or the inverse (negative) of the input voltage. The efficiency of a linear regulator decreases as the difference between the input voltage and the output voltage increases. For example, if we want to convert from 12 V to 6 V, the linear regulator will have an efficiency of only 50%. A standard switching regulator has an efficiency of at least 80%.

3.5.2 DC/AC Converter or Inverter

Basic Principle: An inverter converts the DC electricity from sources such as batteries, solar panels, or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation.

THE GENERAL CASEInverters are used when your equipment requires AC power. Inverters chop and invert the DC current to generate a square wave that is later filtered to approximate a sine wave and eliminate undesired harmonics. Very few inverters actually supply a pure sine wave as output. Most models available on the market produce what is known as "modified sine wave", as their voltage output is not a pure sinusoid. When it comes to efficiency, modified sine wave inverters perform better than pure sinusoidal inverters. A transformer allows AC power to be converted to any desired voltage, but at the same frequency. Inverters, plus rectifiers for DC, can be designed to convert from any voltage, AC or DC, to any other voltage, also AC or DC, at any desired frequency. The output power can never exceed the input power, but efficiencies can be high, with a small proportion of the power dissipated as waste heat.Circuit description

Fig 3.12: A realization of the inverter with a transformer with a movable switch and a current source.Auto-switching device implemented with two transistors and split winding auto transformer in place of the mechanical switch.

OUTPUT

Fig 3.13 : The output achieved from the inverter with the subsequent harmonics.

Square waveform with fundamental sine wave component, 3rd harmonic and 5th harmonic. In one simple inverter circuit, DC power is connected to a transformer through the centre tap of the primary winding.. A switch is rapidly switched back and forth to allow current to flow back to the DC source following two alternate paths through one end of the primary winding and then the other. The alternation of the direction of current in the primary winding of the transformer produces alternating current (AC) in the secondary circuit. The electromechanical version of the switching device includes two stationary contacts and a spring supported moving contact. The spring holds the movable contact against one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary contact. The current in the electromagnet is interrupted by the action of the switch so that the switch continually switches rapidly back and forth.

Circuit Implementation

Fig 3.14: A Single phase transistor bridge inverter

Fig 3.15 : 500 kW, 3 phase inverterMechanism of Inverter- An Engineers ExplanationThe principal mechanism of dc-to-ac conversion consists of chopping or segmenting the dc current into specific portions, referred to as square waves, which are filtered and shaped into sinusoidal ac waveforms. Any power waveform, when analyzed from a mathematical point of view, essentially consists of the superimposition of many sinusoidal waveforms, referred to as harmonics. The first harmonic represents a pure sinusoidal waveform, which has a unit base wavelength, amplitude, and frequency of repetition over a unit of time called a cycle. Additional waveforms with higher cycles, when superimposed on the base waveform, add or subtract from the amplitude of the base sinusoidal waveform. The resulting combined base waveform and higher harmonics produce a distorted wave shape that resembles a distorted sinusoidal wave. The higher the harmonic content, the squarer the wave shape becomes. Chopped dc output, derived from the solar power, is considered to be a numerous superimposition of odd and even numbers of harmonics. To obtain a relatively clean sinusoidal output, most inverters employ electronic circuitry to filter a large number of harmonics. Filter circuits consist of specially designed inductive and capacitor circuits that trap or block certain unwanted harmonics, the energy of which is dissipated as heat. Some types of inverters, mainly of earlier design technology, make use of inductor coils to produce sinusoidal wave shapes.In general, dc-to-ac inverters are intricate electronic power conversion equipment designed to convert direct current to a single- or three-phase current that replicates the regular electrical services provided by utilities. Special electronics within inverters, in addition to converting direct current to alternating current, are designed to regulate the output voltage, frequency, and current under specified load conditions.Inverters also incorporate special electronics that allow them to automatically synchronize with other inverters when connected in parallel.

Note-Be aware that not all the equipment will accept a modified sine wave as voltage input. Most commonly, some laser printers will not work with a modified sine wave inverter. Motors will work, but they may consume more power than if they are fed with a pure sine wave. In addition, DC power supplies tend to warm up more, and audio amplifiers can emit a buzzing sound.

3.5.3 Additional Features of the InvertersAside from the type of waveform, some important features of inverters include: Reliability in the presence of surges. Inverters have two power ratings: one for continuous power, and a higher rating for peak power. They are capable of providing the peak power for a very short amount of time, as when starting a motor. The inverter should also be able to safely interrupt itself (with a circuit breaker or fuse) in the event of a short circuit, or if the requested power is too high. Conversion efficiency. Inverters are most efficient when providing 50% to 90% of their continuous power rating. You should select an inverter that most closely matches your load requirements. The manufacturer usually provides the performance of the inverter at 70% of its nominal power. Battery charging. Many inverters also incorporate the inverse function: the possibility of charging batteries in the presence of an alternative source of current (grid, generator, etc). This type of inverter is known as a charger/inverter. Automatic fall-over. Some inverters can switch automatically between different sources of power (grid, generator, solar) depending on what is available.

When using telecommunication equipment, it is best to avoid the use of DC/AC converters and feed them directly from a DC source. Most communications equipment can accept a wide range of input voltage. A special type of inverter, referred to as the grid-connected type, incorporates synchronization circuitry that allows the production of sinusoidal waveforms in unison with the electrical service grid. When the inverter is connected to the electrical service grid, it can effectively act as an ac power generation source. Grid-type inverters used in grid-connected solar power systems are strictly regulated by utility agencies that provide net metering.Some inverters incorporate an internal ac transfer switch that is capable of accepting an output from an ac-type standby generator. In such designs, the inverters include special electronics that transfer power from the generator to the load.

3.6 Equipment or loadIt should be obvious that as power requirements increase, the expense of the photovoltaic system also increases. It is therefore critical to match the size of the system as closely as possible to the expected load. When designing the system you must first make a realistic estimate of the maximum consumption. Once the installation is in place, the established maximum consumption must be respected in order to avoid frequent power failures. Home AppliancesThe use of photovoltaic solar energy is not recommended for heat-exchange applications (electrical heating, refrigerators, toasters, etc.) Whenever possible, energy should be used sparingly using low power appliances.Here are some points to keep in mind when choosing appropriate equipment for use with a solar system: The photovoltaic solar energy is suitable for illumination. In this case, the use of halogen light bulbs or fluorescent lamps is mandatory. Although these lamps are more expensive, they have much better energy efficiency than incandescent light bulbs. LED lamps are also a good choice as they are very efficient and are fed with DC. It is possible to use photovoltaic power for appliances that require low and constant consumption (as in a typical case, the TV). Smaller televisions use less power than larger televisions. Also consider that a black-and-white TV consumes about half the power of a colour TV. Photovoltaic solar energy is not recommended for any application that transforms energy into heat (thermal energy). Use solar heating or butane as alternative. Conventional automatic washing machines will work, but you should avoid the use of any washing programs that include centrifuged water heating. If you must use a refrigerator, it should consume as little power as possible. There are specialized refrigerators that work in DC, although their consumption can be quite high (around 1000 Wh/day).

3.7 Power Conditioning Unit

Fig 3.16: The components of a power conditioning unit.

The Single phase Power Conditioning Unit (PCU) provides single-phase AC power to the specified loads. The Power Conditioning unit mainly comprises of MPPT, PWM Solar Charge Controller and a single phase inverters (02 Nos.). The MPPT Charger is microprocessor based system designed to provide the necessary DC/DC conversion to maximize the power from the SPV array to charge the battery bank. The charge controller is equipped with necessary software that allows precise charging of the battery bank. Many protection features are also included to ensure that no abnormal or out of range charge conditions are encountered by the battery bank. The system incorporates a front to panel display with LEDs and a switch to indicate the "operational status" and "fault status" of the system, reset system faults and implement various operating modes. The high efficiency inverter converts the DC power available from the Array/Battery back into single phase AC, by incorporating IGBT devices for power conversion. During day time when the solar power is available, the charge controller charges the battery by transferring as much as solar current to battery as required. During this time the battery voltage is monitored continuously. When in the night time, the solar energy is not available the system enables the battery to deliver the current through inverter to meet the demand for powering the street lights. The microprocessor controlled inverter incorporates Pulse Width Modulation (PWM) technology and incorporates all the desired safety features.

Important features/protections in the PCU:

Maximum Power Point Tracking (MPPT) Array ground fault detection. LCD keypad operator interface menu driven. Automatic fault conditions reset for all parameters like voltage, frequency and/or black out. MOV type surge arrestors on AC & DC terminals for over voltage protection from lightening induced surges. PCU operation from -5 to 55 C, All parameters shall be accessible through an industry standard communication link. Over load capacity (for 30 sec.) shall be 150% of continuous rating. Since the PCU is to be used in solar photovoltaic energy system, it shall have high operational efficiency > 92%. The idling current at no load shall not exceed two percent of the full load current. In PCU, there shall be a direct current isolation provided at the output by means of a suitable isolating transformer.

Common Technical Specifications:Type: Self commuted, current regulated, high frequency IGBT baseOutput Voltage Waveform: 1cp, 240VAC (5%)Output Frequency: Pure Sine wave: 50 Hz 3 HzContinuous Rating: As per tableNominal DC Input: 48/120 VDCTotal harmonic Distortion : 92%

3.8 Junction BoxesThe junction boxes shall be dust, vermin, and waterproof and made of FRP / ABS / Thermo Plastic (iP65) must be of Hansel or any equivalent reputed make. The terminals shall be connected to copper bus bar arrangement of proper sizes. The junction boxes shall have suitable cable entry points fitted with cable glands of appropriate sizes for both incoming and outgoing cables. Suitable markings shall be provided on the bus bar for easy identification and cable ferrules shall be fitted at the cable termination points for identification.

The junction boxes shall have suitable arrangement for the following: Combine groups of modules into independent charging sub-arrays that shall be wired to the controller. Provide arrangement for disconnection for each of the groups. Provide a test point for each sub-group for quick fault location. To provide group array isolation. The rating of the JB's shall be suitable with adequate safety factor to inter connect the Solar PV array. Metal oxide variestors shall be provided inside the Array Junction Boxes.

3.9 Wiring

An important component of the installation is the wiring, as proper wiring will ensure efficient energy transfer. Issues specific to solar power relate to the fact that all installations are of the outdoor type, and as a result all system components, including the PV panel, support structures, wiring, raceways, junction boxes, collector boxes, and inverters must be selected and designed to withstand harsh atmospheric conditions and must operate under extreme temperatures, humidity, and wind turbulence and gust conditions. Specifically, the electrical wiring must withstand, in addition to the preceding environmental adversities, degradation under constant exposure to ultraviolet radiation and heat. Factors to be taken into consideration when designing solar power wiring include the PV modules short-circuit current (Isc) value, which represents the maximum module output when output leads are shorted. For the electrical installation of a photovoltaic system, a distinction is made between module or string cables, the DC main cable and the AC connection cable. The electrical connecting cables between the individual modules of a solar generator and to the generator junction box are termed 'module cables' or 'string cables'. These cables are generally used outdoors. In order to ensure earth fault and short-circuit proof cable laying, the positive and the negative poles may not be laid together in the same cable. Single-wire cables with double insulation have proven to be a practicable solution and offer high reliability.

Fig 3.17: The cable requirements

AC connection cableThe AC connection cable links the inverter to the electricity grid via the protection equipment. In the case of three-phase inverters, the connection to the low voltage grid is made using a five-pole cable. For single-phase inverters, a three-pole cable is employed.

3.10 The Balance of System Standards

The BoS items / components of the SPV power plant must conform to the latest edition of IEC/ equivalent BIS Standards as specified in the table.

Table 3.1: The BoS items / components with BIS Standards specifications

3.11 Solar Power System Configuration and Classifications

There are four types of solar power systems: Directly connected dc solar power system Stand-alone dc solar power system with battery backup Stand-alone hybrid solar power system with generator and battery backup Grid-connected solar power cogeneration system

3.11.1 Directly connected dc solar power systemAs shown in Fig 3.18, the solar system configuration consists of a required number of solar photovoltaic cells, commonly referred to as PV modules, connected in series or in parallel to attain the required voltage output. Fig 3.19 shows four PV modules that have been connected in parallel.The positive output of each module is protected by an appropriate over-current device, such as a fuse. Paralleled output of the solar array is in turn connected to a dc motor via a two-pole single throw switch. In some instances, each individual PV module is also protected with a forward-biased diode connected to the positive output of individual solar panels.

Fig 3.18: A three-panel solar array diagram.

Fig 3.19: A directly connected solar power dc pump diagram. An appropriate surge protector connected between the positive and negative supply provides protection against lightning surges, which could damage the solar array system components. In order to provide equipment-grounding bias, the chassis or enclosures of all PV modules and the dc motor pump are tied together by means of grounding clamps. The system ground is in turn connected to an appropriate grounding rod. All PV interconnecting wires are sized and the proper type selected to prevent power losses caused by a number of factors, such as exposure to the sun, excessive wire resistance, and additional requirements that are mandated by the IEC. The photovoltaic solar system described is typically used as an agricultural application, where either regular electrical service is unavailable or the cost is prohibitive. A floating or submersible dc pump connected to a dc PV array can provide a constant stream of well water that can be accumulated in a reservoir for farm or agricultural use. In subsequent sections we will discuss the specifications and use of all system components used in solar power cogeneration applications.

3.11.2 Stand-alone dc solar power system with BATTERY BACKUPThe solar power photovoltaic array configuration shown in Fig, a dc system with battery backup, is essentially the same as the one without the battery except that there are a few additional components that are required to provide battery charge stability.

Fig 3.20: Battery-backed solar powerdriven dc pump.

Stand-alone PV system arrays are connected in series to obtain the desired dc voltage, such as 12, 24, or 48 V; outputs of that are in turn connected to a dc collector panel equipped with specially rated over current devices, such as ceramic-type fuses. The positive lead of each PV array conductor is connected to a dedicated fuse, and the negative lead is connected to a common neutral bus. All fuses as well are connected to a common positive bus. The output of the dc collector bus,which represents the collective amperes and voltages of the overall array group, is connected to a dc charge controller, which regulates the current output and prevents the voltage level from exceeding the maximum needed for charging the batteries. The output of the charge controller is connected to the battery bank by means of a dual dc cutoff disconnect. As depicted in Fig 3.20, the cut-off switch, when turned off for safety measures, disconnects the load and the PV arrays simultaneously. Under normal operation, during the daytime when there is adequate solar insulation, the load is supplied with dc power while simultaneously charging the battery. When sizing the solar power system, take into account that the dc power output from the PV arrays should be adequate to sustain the connected load and the battery trickle charge requirements. Battery storage sizing depends on a number of factors, such as the duration of an uninterrupted power supply to the load when the solar power system is inoperative, which occurs at nighttime or during cloudy days. Note that battery banks inherently, when in operation, produce a 20 to 30 percent power loss due to heat, which also must be taken into consideration. When designing a solar power system with a battery backup, the designer must determine the appropriate location for the battery racks and room ventilation, to allow for dissipation of the hydrogen gas generated during the charging process. Sealed-type batteries do not require special ventilation. All dc wiring calculations discussed take into consideration losses resulting from solar exposure, battery cable current derating, and equipment current resistance requirements.

3.11.3 Stand-alone hybrid AC SOLAR POWER SYSTEM with generator and battery backup

A stand-alone hybrid solar power configuration is essentially identical to the dc solar power system just discussed, except that it incorporates two additional components, as shown in Fig 3.11.4. The first component is an inverter. Inverters are electronic power equipment designed to convert direct current into alternating current. The second component is a standby emergency dc generator.

Fig 3.21: Stand-alone hybrid solar power system with standby generator.

3.11.4 Grid-connected solar power COGENERATION SYSTEM

With reference to Fig 3.11.5, a connected solar power system diagram, the power cogeneration system configuration is similar to the hybrid system just described. The essence of a grid-connected system is net metering. Standard service meters are odometer-type counting wheels that record power consumption at a service point by means of a rotating disc, which is connected to the counting mechanism. The rotating discs operate by an electro physical principle called eddy current, which consists of voltage and current measurement sensing coils that generate a proportional power measurement.New electric meters make use of digital electronic technology that registers power measurement by solid-state current- and voltage-sensing devices that convert analog measured values into binary values that are displayed on the meter bezels by liquid crystal display (LCD) readouts. In general, conventional meters only display power consumption; that is, the meter counting mechanism is unidirectional. Net metering The essential difference between a grid-connected system and a stand-alone system is that inverters, which are connected to the main electrical service, must have an inherent line frequency synchronization capability to deliver the excess power to the grid. Net meters, unlike conventional meters, have a capability to record consumed or generated power in an exclusive summation format; that is, the recorded power registration is the net amount of power consumedthe total power used minus the amount of power that is produced by the solar power cogeneration system.

Figure 3.22 : Grid-connected hybrid solar power system with standby generator.

Net meters are supplied and installed by utility companies that provide grid-connection service systems. Net metered solar power co-generators are subject to specific contractual agreements and are subsidized by state and municipal governmental agencies. When designing net metering solar power cogeneration systems, the solar power designers and their clients must familiarize themselves with the rebate fund requirements. Essential to any solar power implementation is the preliminary design and economic feasibility study needed for project cost justification and return on investment analysis.Grid-connection isolation transformer In order to prevent spurious noise transfer from the grid to the solar power system electronics, a delta-y isolation transformer is placed between the main service switchgear disconnects and the inverters. The delta winding of the isolation transformer, which is connected to the service bus, circulates noise harmonics in the winding and dissipates the energy as heat. Isolation transformers are also used to convert or match the inverter output voltages to the grid. Most often, in commercial installations, inverter output voltages range from 208 to 230 V (three phase), which must be connected to an electric service grid that supplies 277/480 V power. Some inverter manufacturers incorporate output isolation transformers as an integral part of the inverter system, which eliminates the use of external transformation and ensures noise isolation.

4 DESIGN

Design of a solar PV system is the process of estimation of load, sizing of the batteries and sizing of the solar modules that are used in the PV system.

4.1 Introduction and basic principles

The function of a PV system is to power electrical loads .The loads maybe AC loads or DC loads. The solar array produces DC power only during sunshine hours. So if the loads are to be powered during non-sunshine hours energy storage devices are required. Lead acid batteries and Nickel cadmium batteries serve this purpose. To feed the AC loads an inverter is required. Also auxiliary power sources such as diesel generator, wind generator or by connecting the PV system to the grid.Accordingly, PV systems maybe:(a) Stand-alone PV systems(b) Grid-connected PV systems(c) Hybrid PV systemsAs explained in the second chapter a stand-alone system is the one which is not connected to the power grid. In contrast, the PV systems connected to the grid are called grid-connected PV systems. Hybrid PV systems could be stand-alone or grid connected type, but have at least one more source other than the PV.

Fig 4.1 Indias first two megawatt grid connected project, commissioned in the state of West Bengal in east India.Source: pv-magazine.com

Some of the basic Principles to Follow When Designing a Quality PV Systemi. A packaged system should be selected that meets the owner's needs. Customer criteria for a system may include reduction in monthly electricity bill, environmental benefits, desire for backup power, initial budget constraints, etc. The PV array should be sized and oriented to provide the expected electrical power and energy.ii. It should be ensured that the roof area or other installation site is capable of handling the desired system size.iii. Sunlight and weather resistant materials for all outdoor equipment should be specified.iv. Array should be located to minimize shading from foliage, vent pipes, and adjacent structures.v. System should be designed in compliance with all applicable building and electrical codes.vi. The system should be designed with a minimum of electrical losses due to wiring, fuses, switches, and inverters.vii. The battery system should be properly housed and managed, should batteries be required.viii. It should be ensured that the design meets local utility interconnection requirements.PV systems are designed and sized to meet a given load requirement. PV system sizing and design involves:1. PV system design involves a decision on which configuration is to be adopted to meet the load requirement as explained above.2. Once the system configuration is decided the size or capacity of the various components is determined.

A PV system design and sizing process passes through the following two stages depending on the level of details used in components sizing:1. Approximate design2. Precise designIn the approximate design, several simplifying assumptions are made with respect to the component performance (without referring to the actual data sheets), solar radiation data, seasonal variation in the load performance variation of PV panel with season, etc. In the precise design, however, attention is given to accurate details of all the above factors.

4.2 System type selectionOne has to determine the configuration of PV system and which components (PV panels, load, battery, controllers, diesel generator, etc.) are to be connected in a system. The configuration and design of the system will change depending on1. The type of the load (AC or DC, light or heavy, etc.),2. The load requirement (critical/non-critical, reliability, cost, etc.)3. Its geographical location (wind resources, solar resources, proximity with grid, etc.).

A solar PV system configuration can be very simple, incorporating only two components (load and the PV panel), or it can be very complex, containing several power sources, sophisticated controllers and multiple energy storage units to meet stringent load requirements. In the previous chapter the various configurations of a PV system are explained. The establishment or household owner has to choose from these configurations while keeping in mind the following parameters Load requirements Resource availability Performance of the system Reliability of the system Cost of the system

4.3 Home AppliancesThe use of photovoltaic solar energy is not recommended for heat-exchange applications (electrical heating, refrigerators, toasters, etc.) whenever possible, energy should be used sparingly using low power appliances.

Fig 4.2Some of the appliances which can be run by solar PV system

Here are some points to keep in mind when choosing appropriate equipment for use with a solar system:i. The photovoltaic solar energy is suitable for illumination. In this case, the use of halogen light bulbs or fluorescent lamps is mandatory. Although these lamps are more expensive, they have much better energy efficiency than incandescent light bulbs. LED lamps are also a good choice as they are very efficient and are fed with DC.ii. It is possible to use photovoltaic power for appliances that require low and constant consumption (as in a typical case, the TV). Smaller televisions use less power than larger televisions. Also consider that a black-and-white TV consumes about half the power of a colour TV.iii. Photovoltaic solar energy is not recommended for any application that transforms energy into heat (thermal energy). Use solar heating or butane as alternative.iv. Conventional automatic washing machines will work, but one should avoid the use of any washing programs that include centrifuged water heating.v. If one must use a refrigerator, it should consume as little power as possible. There are specialized refrigerators that work in DC, although their consumption can be quite high (around 1000 Wh/day).The estimation of total consumption is a fundamental step in sizing the solar system. Here is a table that gives a general idea of the power consumption that one can expect from different appliances.Table 4.1 Power rating of some home appliances

4.4 Illustration and Flowchart for design of habitat PV system

Flowchart 4.1 SCHEMA A Illustration and Flowchart for Design of Habitat PV System

Part A of the flowchart refers to load estimation, part B refers to sizing of batter and part C refers to sizing of PV modules. These processes are explained in detail in the following topics.

4.5Design processThe process is explained with the help of an example. A solar PV system is to be designed wherein the load consists of a CFL, TV, fan, and refrigerator and computer. The system should allow the use of loads in the nonsunshine hours. The operating hours and the power rating of these loads are

Table 4.2 illustrative habitat appliance use in a dayThe formulae for calculations are marked in RED and the calculations done for the solar PV system to be designed is