Super-Efficient Cells Key to Low-Cost Solar Power

U.S. Department of Energy's National Renewable Energy Laboratory (NREL) developed New Solar Technology – Concentrated Photovoltaic or CPV Generator

Recently in U.S.A, the combined talents of a solar company, Amonix and the National Renewable Energy Laboratory (NREL) resulted with development of solar power concentrator that generates electricity at prices competitive with natural gas. The Amonix 7700 Concentrated Photovoltaic (CPV) Solar Power Generator, developed by Amonix and the U.S. Department of Energy's National Renewable Energy Laboratory, is the size of an IMAX screen but costs much less than comparable generators, partly because of the efficiency of its small solar cells. It delivers more "energy per acre" than anything yet available in the solar energy world. The 7700 uses acrylic Fresnel lenses to concentrate sunlight up to 500 times its usual intensity and direct it onto 7,560 tiny, highly efficient multi-junction PV cells.

The cells, originally developed by NREL scientists, can convert 41.6 percent of the sunlight that shines on them into usable electricity in a laboratory setting, a world record. But the multi-junction cells on the Amonix 7700 are achieving 31 percent efficiency at the module level and 27 percent at the system level in the field, the highest ever achieved for an operating CPV concentrator. Such unprecedented efficiency supports to reduce costs and reducing land use — both key for solar electricity to reach cost-parity with fossil fuels. Observing the potential for game-changing cost cuts, Amonix, with technical support from NREL's High-Performance PV Project and financial support through DOE and its Solar Energy Technologies Program, redeveloped its flagship CPV system using the multi-junction cells.

A six-inch square silicon wafer in traditional photovoltaic (PV) panels produces about 2.5 watts of electricity. That same-sized wafer, cut into hundreds of square-centimeter cells in the Amonix 7700, each teamed with a Fresnel lens, produces more than 1,500 watts. It reduces the required area for cells 500 times. The 7700 also keeps down costs by integrating the lenses, the cells and the mounting structure into a single unit that eliminates most of the parts and costs associated with other concentrator designs. The seven MegaModules that make up the 53-kilowatt system can be hauled on two flatbed trucks, then assembled in the field in hours, rather than weeks. The key breakthrough that lifted the 7700 to a 50 percent greater power output than previous generations of Amonix generators was the substitution of the multi-junction cells made of gallium indium arsenide and gallium phosphide for the more common silicon cells. Cells made from gallium, indium and other elements from the III and V columns of the periodic table are more expensive to produce today, but also can be more efficient at converting the sun's photons into usable electrons for electricity.

As per California’s Market Price Referent, the 7700 already has driven the price of electricity from solar down to the price of electricity from natural gas, which establishes a proxy price for electricity generated by a new state-of-the-art natural gas plant. Solar power is at or near price parity in six other states that share California's sunny and dry climates — Arizona, Nevada, Utah, New Mexico, Colorado and Texas.

Source:-           http://www.nrel.gov/features/20110216_low-cost_solar.html

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