PV-POWER IN INDIA
Large-scale deployment of solar generated power for both grid connected as well as distributed and decentralised off-grid provision of commercial energy services is a golden dream. Breakthroughs are expected in next five years[2015].
What are the Benefits of PV Power?
Considering the emission rate of 1.3 kg CO2 per kWh for diesel –generated electricity, each 100 kWp mini-grid has the potential of saving about 180 tonnes of CO2 emissions annually. There is no pollution through the use of a PV system – nor is there any heat or noise generated which could cause local discomfort
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India Has a Lot of Sunlight
In India, there are about 300 clear sunny days in a year and solar energy is widely available in most parts of the country, including rural areas. Cost is still a barrier, as is the potential for local manufacture, but there is enormous scope for widespread dissemination of PV, a simple, robust solar application.
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Dissemination of use of PV technology in India
There is a vast scope for and potential for the use of PV technology in India. There are still over 90,000 villages in the country to be electrified. Recognizing the importance of PV technology in the Indian context, the Government has been implementing a comprehensive programme covering R & D, demonstration, commercialisation and utilisation for more than 15 years.
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Three Laws of Energy Transition
The law of stable long-term energy costs-to income ratio Growth in economic productivity requires better quality of energy services The law of growing energy productivity Bashmakov, I., 2007, Three Laws of Energy Transitions, Energy Policy, Vol. 35, pp. 3583-3594
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Solar Radiation & Photovoltaics
Some theory discussion
The nature and availability of solar radiation
Solar radiation arrives on the surface of the earth at a maximum power density of approximately 1 kilowatt per meter squared (kWm-2). The actual usable radiation component varies depending on geographical location, cloud cover, hours of sunlight each day, etc. In reality, the solar flux density (same as power density) varies between 250 and 2500 kilowatt hours per meter squared per year (kWhm-2 per year). As might be expected the total solar radiation is highest at the equator, especially in sunny, desert areas.
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SUN LIGHT→ ELECTRICITY
Solar cells are made of silicon (microelectronics/semiconductors) Treated to be positive on one side and negative on the other. When light energy hits the cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric
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Photovoltaic system structures
Systems with fixed inclination - (fixed supporting structure) Systems with active tracking - single/double axis tracking systems (characterized by step by step motors and control electronics) Self contained systems or “stand alone” Network connected systems or “grid connected”
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Module & Panel: Array
Every single photovoltaic cell has small dimensions and generally produces a power between 1 and 3 watts and 0,5Volts. We connect several cells among themselves to create bigger units called modules. The modules are connected to constitute panels that produce the wanted power
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Types of solar cell modules
Mono-crystalline cell modules. The highest cell
efficiencies of around 15% are obtained with these modules. The cells are cut from a monocrystalline silicon crystal. Multi-crystalline cell modules. The cell manufacturing process is lower in cost but cell efficiencies of only around 12% are achieved. A multi-crystalline cell is cut from a cast ingot of multi-crystalline silicon and is generally square in shape.
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Types of solar cell modules
Amorphous silicon modules. These are made from
thin films of amorphous silicon where efficiency is much lower (6-9%) but the process uses less material. The potential for cost reduction is greatest for this type and much work has been carried out in recent years to develop amorphous silicon technology. Unlike monocrystalline and multicrystalline cells, with amorphous silicon there is some degradation of power over time.
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Components in a solar power system contribute to the initial cost
Solar modules, battery, inverter, charge controller, and other BOS (balance of system) / components. These four components incur more than twothirds of the total cost. Capital cost of thermal generation is as low as 40 000 rupees per kW. Compared to this, decentralized solar power generation is 285 000 rupees per kW or 3.5 times higher.
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Stand-alone system:
Stand-alone systems are virtually self sufficient and not interacted with grid. Such system may have some backup/storage system to run during the no sun or low sun hour. PV system without storage battery (Direct coupled PV system) DC system with storage battery DC systems powering AC load (with or without storage)
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Direct coupled PV systems:
This is the simplest and least expensive photovoltaic system designed to be used only during daytime. Here the electricity generated is directly and simultaneously used by the appliances. Through out the day, the insolation level is changing continuously and so the output. Examples of direct use systems include: Remote water pumping with a storage tank. Stand alone solar powered appliances such as calculators and toys.
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Simple intermittent dc load
When solar radiation strikes the PV module, DC (direct current) electricity is generated. During generation, power can be used in any DC load directly. But the generation exists till sun shines.
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DC Systems With Storage Batteries-1:
Basic components of this system include a photovoltaic module, a charge controller, storage batteries and appliances that represent the system's electrical load. But here the type of loads used should be of DC load as battery is capable of running DC load only.
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DC Systems With Storage Batteries-2:
Batteries are used to store the electrical energy generated by the photovoltaic modules. Power can be drawn from the batteries whenever required- during the day or night, continuously or intermittently. In addition, a battery bank has the capacity to supply high surge currents for a short time. This gives the system the flexibility to start large motors or to perform other high power tasks.
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PV with AC Loads :
Photovoltaic modules produce direct current (DC) electrical power and batteries store DC energy. However many common appliances require alternating current (AC) power. Direct current systems which power AC loads must use an inverter. Inverters provide convenience and flexibility in a photovoltaic system but also add complexity and cost. It is also possible to power the AC load without battery but in that case it would be confined only to daytime when solar radiation is sufficient to generate required electricity.
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Storage device and inverter
• Storage device is needed to run the system at night or in low sunshine hour; to run any AC (alternating current) load, an inverter has to be used to convert DC into AC.
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PV power: Cost considerations for India
Case studies
Energy Cost and Risk Management
Solar energy technologies are low-to-no-risk technologies –No price volatility for inputs – Low risk of government environmental regulations Adding solar to energy portfolio reduces portfolio risk – Photovoltaic (PV) devices generate electricity via an electronic process – “Electricity from your roof,” windows, dress, backpack
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The SPV (solar photovoltaic) plant 25 kWp
Each 25 kWp plant can cater to 150 service connections with an average load of 80 watts each to fulfil the domestic requirement and 80–100 watts for shops for illumination, photocopying, battery charging, etc. A consumer pays 500 rupees (11 dollars) or 1000 rupees (22 dollars) as security deposit with a monthly charge of 100–125 rupees (4–5.5 dollars) based on the demand for load.
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The following figure shows PV system with storage battery, powering AC load. It is also possible to power the AC load without battery but in that case it would be confined only to daytime when solar radiation is sufficient to generate required electricity
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Utility grid interconnected system:
A utility grid interactive photovoltaic system is connected to the utility grid. A specially designed inverter is used to transform the PV generated DC electricity to the grid electricity (which is of AC) at the grid voltage. The main advantage of this system is that power can be drawn from the utility grid and when power is not available PV can supplement that power. But again such grid interactive system is designed with battery or without battery storage.
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Hybrid Systems
System with more than one source of power is called Hybrid system. Since the supply of solar is very unpredictable, it is often desirable to design a system with additional source of power. The most common type of hybrid system contains a gas or diesel powered engine generator. Another hybrid approach is a PV/Wind system. Adding a wind turbine to a PV system provides complementary power generation. The wind often continues to blow at night and during low sun conditions. For even greater reliability and flexibility, an engine generator can be included in a PV/Wind system.
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Components of PV system
A PV system consists of following components. 1. Solar PV module 2. Battery 3. Charge controller 4. Inverter/converter 5. Mounting structure and tracking device 6. Interconnections and other devices
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Components & configuration
In every configuration all these components are not used. Components used depend upon the type of configuration, which in other way depend upon the application. For example: Storage battery is not used in case of direct coupled PV system, inverter is not used in case of DC load.
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Parameters influencing PV system operation
Solar irradiation: Power of a solar cell changes with solar radiation. which is different for different geographical location, tilt and orientation.. The change of power is almost linear with the solar radiation. There is a very little change in open circuit voltage (Voc) of the solar cell, but the short circuit current (Isc) varies almost linearly with the solar intensity.
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Parameters influencing PV system operation
Temperature: Power decreases with increasing solar cell temp. Voc decreases by a value of approximately 3mV/K for each degree rise in temp. A solar cell with Voc of 0.6 V at 250C reaches a value of 0.45V at 750C. Isc increases with rise of temperature but the reduction in voltage is much greater than the corresponding increase in current. This affects the power, which decreases at a rate of about 0.45% per degree rise in temp. The operating temperature of the battery should be nominal (25-35 degree C). Higher temperature may give a higher capacity of battery but at the same time it reduces the life of the battery.
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Aging effect:
Solar cells, which are properly encapsulated, have a very long life and power does not reduce in any significant manner. The effect of aging is more severe in amorphous Si solar cells.
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Shading effect:
Shading has a very bad impact on the performance of the PV system. Even a partial shading (on one or two cells) of the whole module can reduce the output drastically and if it persists for a longer period, it may damage the whole system. To protect the modules from such adverse effect, a bypass diode is used. The effect is more prominent in crystalline silicon solar modules. Amorphous silicon modules are less affected by shading.
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Other effect:
Mismatching of module in a string, resistance of wires and cables etc can drastically alter the performance of the PV system. Dust and dirt can reduce the PV output.
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LED lighting
Recently solar PV are coupled with Light Emitting Diodes (LEDs) to give energy efficient light. Recent advancements in LED technology have led to the development of white light emitting diodes (WLEDs). WLEDs provide a bright white light that’s ideal for domestic lighting. The advantage of using LEDs with solar PV systems is that the LED requires a much lower wattage (less than conventional high efficiency light bulbs), therefore the size and the cost of the solar system is much reduced for each household.
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Solar home systems (SHS): Stand-alone electrical systems. They consist of • a photovoltaic (PV) module; • a re-chargeable battery; • a charge controller, which prevents the battery from being over-charged or deep-discharged; • fluorescent lamps rated from 6 to 11 W; • wiring and fixtures. • The PV modules, are rated at 20 to 80 Wp with 50 Wp the most popular size.
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Solar home systems (SHS)
• A system based on a 20 Wp module can supply two or three 6 W lamps for about four hours per day: at the other end of the range, an 80Wp system can power four 8 W lamps and a black and white television set.
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Highlight of India's solar energy plan_Dream
incentives for production, installation and research and development
"National Solar Mission"
Plan spread over 30 years aims to scale up solar power generation from nothing at present to 20 GW by 2020. It is a three-phased plan that hopes to generate 1-1.5 GW of solar power by 2012, 6-7 GW by 2017 and the rest by 2020.
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India’s solar energy dream
Solar-powered equipment and applications will be mandatory for hospitals, hotels and government buildings, and villages and small towns will be encouraged with micro financing. The plan also outlines a system of paying households for any surplus power from solar panels fed back into the grid. The target would be to provide access to lighting for 3 million households by 2012. India will promote solar heating systems and use 4050 million sq meters of area to install solar collectors in domestic, industrial and commercial sectors.
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India’s PV dream
It is aimed to cut down production costs of solar panels and spur domestic manufacturing. Money will be spent on incentives for production, installation and research and development. The plan has a "near term" target of 100 megawatts, and 100 GW by 2030, or 10-12 percent of total power generation capacity estimated for that year.
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Among the elements of the action plan are the following aims:
Deployment of 400,000 solar lanterns as a substitute for kerosene lanterns rural electrification through PV systems covering 400 villages / hamlets a special programme on water pumping systems intensified R & D on technologies which can lead to a reduction in cost commercialisation of PV systems for applications by giving a market orientation to the programme and promoting manufacturing and related activities As a result of these measures India is among the leading countries in the world in the development and use of PV technology.
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PV power systems
Rural and remote areas applications
Lessons learned and applied in wide-scale dissemination
project design originating from participatory assessment of the energy needs and present energy expenses; establishment of rural credit mechanisms; establishment of infrastructure for distribution, installation, maintenance and repair of PV systems; training of solar technicians and solar dealers/micro-enterprises.
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Rural electrification
farms, schools, mountain refuge huts) low wattage fluorescent lighting is recommended power supplies for remote villages street lighting individual house systems battery charging mini grids
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Rural water pumping applications
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Application for small power pack
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Communications
radio repeaters remote TV and radio receivers remote weather measuring mobile radios rural telephone kiosks data acquisition and transmission (for example, river levels and seismographs)
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Transport aids
road sign lighting railway crossings and signals hazard and warning lights navigation buoys road markers
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Security systems & Miscellaneous
security lighting remote alarm system electric fences ventilation systems calculators pumping and automated feeding systems on fish farms solar water heater circulation pumps boat / ship power vehicle battery trickle chargers earthquake monitoring systems emergency power for disaster relief
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Manufacture in developing countries
In India, Central Electronics of Ghaziabad is not only the nation’s largest PV producer, but are the fifth largest producer of monocrystalline silicon solar cells in the world (D.V.Gupta cited in Garg et al, 1997). There are over 60 companies in India alone producing solar cells, modules and systems.
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PV Manufacturers in India
TATA BP BHEL CENTRAL ELECTRONICS LTD SELCO INDIA PHOTON ENERGY SYSTEMS LIMITED
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PV Manufacturers of INDIA
India’s primary solar PV producer is Tata BP solar, which expanded production capacity from 8 MW in 2001 to 38 MW in 2004. Central Electronics, Bharat Heavy Electrical, and WEBEL Solar are other leading solar cell/module manufacturers in India.
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Thin films & multi-junction cells and building integrated PV modules
Photovoltaic technologies have seen significant advances in thin films and multijunction cells. Building integrated photovoltaic like photovoltaic window glass or roof shingles. The rate of deployment of PVs in general is increasing at a significant annual rate worldwide.
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Sometime in the future....
Development in photovoltaics, keep improving the efficiencies and reducing the costs. Sometime in the future, maybe in the next 10-15 years, the costs will be low enough that you will not need any incentives for people to use PV. That will happen because of the thin film and multijunction developments.
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Text books on Solar Energy Engineering
1. D. Yogi Goswami, Frank Kreith, Jan. F. Kreider,
“Principles of Solar Engineering”, 2nd Edition, Taylor & Francis, 2000, Indian reprint, 2003 2. Edward E. Anderson, “Fundamentals for solar energy conversion”, Addison Wesley Publ. Co., 1983. 3. G. N. Tiwari and M. K. Ghosal, “Fundamentals of Renewable energy Sources”, Narosa Publishing House, New Delhi, 2007
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Text books on Solar Energy Engineering
4. Mukund. R. Patel, Wind and Solar Power Systems, 2nd Edition, Taylor & Francis, 2001 5. Roger Messenger and Jerry Ventre, Photovoltaic Systems Engineering, 2nd Edition, CRC Press, 2003
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Acknowledgements
This presentation is an edited and collected version of already available info on the web. It is published for the benefit of those who wish to educate themselves. Thanks to the original source providers.
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