Unleashing Potential of the Solar Electric Power Date:   Monday , August 31, 2009 Every 60 minutes, the Earth receives enough sunshine to power the world’s electricity requirements for a year. Consumers, scientists and energy conservationists are looking for ways to harness this solar energy and spur growth in alternative energy sources such as bio-fuels and wind. Here is an overview of the processes and technologies required to produce solar electric power. In order to produce electricity power companies generally burn non-renewable energy sources such as coal, natural gas, and other fossil fuels, or rely on nuclear power. As these energy sources deplete, electricity may become more expensive. Another downside to using non-renewable sources is pollution. Therefore, researchers are pursuing more efficient, cost-effective, and nonpolluting renewable energy sources such as hydroelectric power, wind power, and solar power. If enough electricity can be generated through renewable sources, we can reduce our dependence on fossil fuels and lower the amount of pollution associated with today’s power generation methods. There are a variety of ways to convert sunlight into useful energy. Solar thermal conversion is one method. Water heaters use the sun’s radiation to directly heat water for swimming pools and for home use by circulating water through collection panels. Another method uses mirrors or lenses to concentrate sunlight on water to create steam. The steam can then be used to operate a steam turbine. The fastest growing market for solar energy is photovoltaics, the direct conversion of sunlight into electricity. The term 'photovoltaic' is a combination of 'photo', meaning light, and 'voltaic', meaning electricity. Solar panels are becoming common on rooftops in grid connected systems. Photovoltaic solar cells generate electricity when exposed to sunlight. Solar modules comprise many interconnected solar cells. Like computer chips, the majority of solar cells are built using silicon. The solar cell has the property of creating electric power when exposed to light. To enable this unique property, the silicon material and related components are carefully engineered for optimum performance. The processes used in the manufacturing of solar cells are adapted from some of those developed for the electronics industry, although the equipments used are different. The most common type of solar cell today is made from thin wafers or sheets of crystalline silicon. To build a crystalline silicon solar cell, the surface of the wafers is first roughened to improve their light trapping ability. The next step is to introduce small amounts of impurities, called n-type or p-type dopants, to create doped layers with atomic structures that have either extra or missing electrons. Next, a non-reflective coating is deposited on the surface of the wafer to reduce the amount of sunlight reflected off. This increases the amount of light reaching the interior of the solar cell. Finally, metal conductors are applied to collect the electricity and feed it to the next cell, in a way similar to hooking up batteries in series. When numerous solar cells are combined, wired together, and encased in a weatherproof housing almost like an automobile windshield, the solar panel is complete and ready to produce direct current, or DC electricity, for decades. The quality of a solar cell is measured by its 'power conversion efficiency', which indicates the fraction of the power in the sunlight that is transformed into electricity. The higher the cell efficiency, the more electric power a cell can produce in a given amount of area, increasing the overall cost effectiveness of any system. The electricity generated by a photovoltaic system is proportional to the size, i.e. the surface area, of panels in it. When the DC output of the system is connected to an inverter, the electricity is transformed to alternating current, or AC electricity, for use in our homes and businesses or to feed the local power grid. While solar power is helping to meet the world’s increasing energy needs, there are manufacturing challenges to overcome in lowering the cost per watt. One way to reduce the cost per watt is to increase the cell efficiency, which means production of more electricity by each module. The cost per module must be reduced to make the system more competitive with other methods of electricity generation. Depending on the cell technology, solar panels convert eight to twenty percent of the sun’s energy into electricity, which can make solar energy competitive with peak power rates available from electric grids in certain places. With increased cell efficiency and reduced manufacturing costs, solar energy will be able to provide electricity at or below the rate of traditional energy sources, especially during sunny afternoons, which are peak power production periods. The author is Group Head - Display and SunFab Solar Group - Applied Materials, India