08-16-2017, 08:49 PM
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ADVANCEMENTS IN UTILIZATION OF SOLAR ENERG
Presented In:
Gokula Krishna College Of Engineering, Sullurpet
Abstract:
Solar energy is an inexhaustible resource. The sun Produces vast amounts of renewable solar energy that can be collected and converted into heat and Electricity.
Solar power is the generation of electricity from sunlight. This can be direct as with photovoltaics (PV), or indirect as with concentrating solar power (CSP), where the sun's energy is focused to boil water which is then used to provide power. Solar power has the potential to provide over 1,000 times total world energy consumption in 2008, though it provided only 0.02% of the total that year. If it continues to double in use every two to three years, or less, it would become the dominant energy source this century. The largest solar power plants, like the 354 MW SEGS, are concentrating solar thermal plants, but recently multi-megawatt photovoltaic plants have been built. Completed in 2008, the 46 MW Moura photovoltaic power station in Portugal and the 40 MW Waldpolenz Solar Park in Germany are characteristic of the trend toward larger photovoltaic power stations. Much larger ones are proposed, such as the 100 MW Fort Peck Solar Farm, the 550 MW Topaz Solar Farm, and the 600 MW Rancho Cielo Solar Farm.
Solar power is a predictably intermittent energy source, meaning that whilst solar power is not available at all times, we can predict with a very good degree of accuracy when it will and will not be available. Some technologies, such as solar thermal concentrators have an element of thermal storage, such as molten salts. These store spare solar energy in the form of heat which is made available overnight or during periods that solar power is not available to produce electricity.
India is both densely populated and has high solar insolation, providing an ideal combination for solar power in India. Much of the country does not have an electrical grid, so one of the first applications of solar power has been for water pumping; to begin replacing India's four to five million diesel powered water pumps, each consuming about 3.5 kilowatts, and off-grid lighting. Some large projects have been proposed, and a 35,000 km2 area of the Thar Desert has been set aside for solar power projects, sufficient to generate 700 to 2,100 gigawatts.
In July 2009, India unveiled a $19 billion plan to produce 20 GW of solar power by 2020.Under the plan, solar-powered equipment and applications would be mandatory in all government buildings including hospitals and hotels.
18 November 2009, it was reported that India is ready to launch its Solar Mission under the National Action Plan on Climate Change, with plans to generate 1,000 MW of power by 2013.
Present status
Installed capacity
The amount of solar energy produced in India is merely 0.4% compared to other energy resources. The Grid-interactive solar power as of June 2007 was merely 2.12 MW.
Government-funded solar energy in India only accounted for approximately 6.4 megawatt-years of power as of 2005. However, as of October 2009, India is currently ranked number one along with the United States in terms of installed Solar Power generation capacity.
Number of solar street lighting systems: 55,795
Number of home lighting systems: 342,607
Solar lanterns: 560,295
Solar photovoltaic power plants: 1566 kW
Solar water heating systems: 140 km2 of collector area
Box-type solar cookers: 575,000
Solar photovoltaic pumps: 6,818
Applications:
Rural electrification
Lack of electricity infrastructure is one of the main hurdles in the development of rural India. India's grid system is considerably under-developed, with major sections of its populace still surviving off-grid. As of 2004 there are about 80,000 unelectrified villages in the country. Of these villages, 18,000 could not be electrified through
extension of the conventional grid. A target for electrifying 5,000 such villages was fixed for the Tenth National Five Year Plan (2002-2007). As on 2004, more than 2,700 villages and hamlets had been electrified mainly using SPV systems. Developments on cheap solar technology is considered as a potential alternative that allows an electricity infrastructure comprising of a network of local-grid
Bangalore has the largest deployment of rooftop solar water heaters in India that will generate energy equivalent to 200 MW every day and will be the country's first grid connected utility scale project soon.
Bangalore is also the first city in the country to put in place an incentive mechanism by providing a rebate, which has just been increased to Rs 50, on monthly electricity
Of Electrical
clusters with distributed electricity generation. That could allow bypassing, or at least relieving the need of installing expensive, and lossy, long-distance centralised power delivery systems and yet bring cheap electricity to the masses.
Agricultural support
Water pumping
Solar PV water pumping systems are used for irrigation and drinking water. The majority of the pumps are fitted with a 200 3,000 watt motor that are powered with 1,800 Wp PV array which can deliver about 140,000 liters of water/day from a total head of 10 meters. By 30 September, 2006, a total of 7,068 solar PV water pumping systems have been installed.
Harvest processing
Solar driers are used to dry harvests before storage.
Cooling
Another e.g. is the cost of energy expended on temperature control a factor squarely influencing regional energy intensity. With cooling load demands being roughly in phase with the sun's intensity, cooling from intense solar radiation could be an attractive energy-economic option in the subcontinent.
Solar water heaters
bills for residents using roof-top thermal systems which are now mandatory for all new structures.
Pune, another city in the western part of India, has also recently made installation of solar water heaters in new buildings mandatory.
Not Affordable In India:
Solar power is currently prohibitive due to high initial costs of deployment. To spawn a thriving solar market, the technology needs to be competitively cheaper i.e. attaining cost parity with fossil or nuclear energy. India is heavily dependent on coal and foreign oil a phenomenon likely to continue until non-fossil / renewable energy technology becomes economically viable in the country. The cost of production ranges from Rs 15 to Rs 30 per unit compared to around Rs 2 to Rs 6 per unit for conventional thermal energy. The parts of solar water heaters, like evacuated glass tubes, are still imported from other countries and adds to the bill of materials. Solar heaters available in China for under $200 costs $400 in India.
Photovoltaic Energy
Photovoltaic cells (PV) are used worldwide to convert sunlight into electricity. The PV cell contains two layers of semiconducting material, one with a positive charge and the other with a negative charge (Fig-1). When sunlight strikes the cell, some photons are absorbed by semiconductor atoms, freeing electrons that travel from the negative layer of the cell back to the positive layer, in the process creating a voltage. The flow of electrons through an external circuit produces electricity.
Since individual photovoltaic cells produce little power and voltage - they generate only about one to two watts per cell they are connected together electrically in series in a weatherproof module. To generate even more power and voltage, modules can be connected to one another to form a solar panel; solar panels are grouped to form an array. The ability to add additional modules as needed is a significant advantage of PV systems.
Several PV technologies are in use or in development. The silicon-based PV cell, made with the same silicon used in the semiconductor industry, has dominated the market and continues to do so. Solar Energy Industries Association (SEIA) reports that 94 percent of PV modules used today are made of crystalline silicon.
The search for cheaper Solar energy systems however, has spurred the development of thin-film PV cells that have semiconductor layers only a few millionths of a meter thick. Thin-film PV technologies are intended to reduce the amount of expensive materials needed to produce solar cells. For example, new methods are being used to produce solar cells that reduce or eliminate the use of high-priced silicon. The U.S. Department of Energy (DOE) estimates that U.S. production of Thin-film solar modules will exceed that of crystal-line silicon modules
by 2010.
Research scientists also are working on a new generation of solar cells that include nanomaterials, multijunction cells and various other research efforts that may produce "leapfrog" technologies offering considerably higher efficiency at a lower cost.
Nanotechnology, for instance, has attributes that, in theory, may triple the amount of energy produced by photons of sunlight. is technology also could result in PV cells that could be painted on homes and buildings. Research on inverted multi junction cells that capture more of the sun's energy also is ongoing, and already has produced a world-record 39.3 percent conversion efficiency.
These emerging technologies have the potential to produce higher efficiencies more cost-effectively. Some companies are developing faster and more efficient ways to manufacture thin- film solar cells at lower costs. HelioVolt, an Austin-based company, has developed FASS T, which it claims is a low-cost manufacturing process for applying copper indium gallium selenide, a thin-film PV coating, to construction materials such as roofing, steel and flexible composites in 80 to 98 percent less time than conventional processes. This would position the company to bring economical building products featuring integrated PV cells to the market.
The Photovoltaic Cell
Fig-1
Transmission
Solar energy differs from most energy technologies In that it can be generated on site, reducing Or eliminating fuel transportation and electricity Transmission and distribution costs. Solar Water heating and space heating devices are "Stand-alone" systems that are not connected to the electric grid. A PV system provides electric Power directly to a user and can be used either as A "stand-alone" power source or connected to the Electricity grid. Systems offering this flexibility sometimes are Called distributed power generators. By contrast, Utility-scale concentrating solar power plants use Centralized power plants and transmission lines to Distribute electricity to customers.
Fig2
A home or business with a PV system that is connected to the electric grid has the option of supplementing its energy needs with electricity from the local utility company and delivering excess electricity to the grid.
Solar Thermal Energy
Flat-plate collectors large, insulated metal boxes with glass or plastic covers and dark heat absorbing plates are the most common collectors used for home solar water and space heating (Fig-3). Other common varieties are evacuated-tube collectors and integral collector-storage systems. All three types gather the sun's energy, transform it to heat and then transfer that heat to water, a heat-transfer
The most powerful large-scale solar thermal technology, however, is concentrating solar power (CSP). While CSP can be PV-based, it generally refers to three solar thermal systems parabolic troughs, solar dish/engines and power fluid or air. Flat-plate collectors typically are mounted on the roof. Evacuated-tube collectors are sometimes used to heat water, but also have useful commercial and industrial applications where higher temparatures are required.
Solar thermal energy refers to technologies that use the sun's energy to heat water and other heat-transfer fluids for a variety of residential, industrial and utility applications. Simple and widely used applications of solar thermal energy include solar water heating, swimming pool heating and agricultural drying. In the U.S., solar pool, water and space heating are currently the major applications of thermal energy.
towers each of which is in use or under development today. These systems use mirrors or reflectors to focus sunlight to heat a fluid and make steam, which then is used to generate electricity.
At present, only parabolic trough CSP systems are in commercial use in the U.S., with three installations in three states capable of generating 419 MW of electricity in all.Trough systems consist of a linear, parabolic-shaped reflector that focuses the sun's energy on a receiver pipe, heating a transfer fluid flowing through the pipe; the transfer fluid then generates superheated steam which is fed to a turbine and electric generator to produce electricity. The troughs track the sun from East to West during the day so that the sun is continuously focused on the receiver pipes
(Fig-4).
Solar power towers use a large field of sun-tracking mirrors called heliostats to concentrate sunlight on a receiver located on the top of a tower. The receiver heats a heat transfer fluid such as molten nitrate salt that is then used to generate steam to power a turbine-generator to produce electricity operating periodically from 1996 to 1999.
Fig 5
The molten salt reaches about 1,050 degrees Fahrenheit in the receiver before being stored in a tank where it can retain its heat for several hours. In the U.S., two large-scale power tower demonstration plants Solar One and Solar Two located in the Mojave Desert near Barstow, California have generated 10 MW of electricity each. Solar One operated off and on from 1982 to 1988 and used water as its heat transfer fluid, while Solar Two used molten nitrate salt for heat transfer,
A solar dish/engine system consists of a solar concentrator glass mirrors in the shape of a dish that reflect sunlight onto a small area and a power conversion unit that includes a thermal receiver and a generator (Fig-5). The thermal receiver includes tubes for the transfer fluid usually hydrogen or helium that transfers heat to a generator to produce electricity.
Europe's first commercial solar power tower went online in Spain in late 2006 and currently generates 11 MW of electricity, enough to power just under 6,000 homes. More fields of mirrors are being added to this plant. Solucar, its developer and operator, plans two more power towers at other locations in Spain.