An Overview of Photovoltaic Power Systems

The United States is supporting a very aggressive research and development program in the field of photovoltaics. The goals of this program are to reduce the cost of solar cell arrays to a capital cost of 50¢/peak watt by the year 1986. The long-term goals are to achieve 10 to 30¢/peak watt by 1990 or 2000. The photovoltaic community is optimistic that the 1986 goals will be met with the use of silicon solar cells. The longer term goal may require the development of new thin film photovoltaic devices. As the price of solar cell arrays continues to decrease; the number of applications that are economically justified increases. The present production rates of photovoltaic arrays are close to 1 MW of production per year. The maximum expected efficiencies of 20 to 25 percent have already been achieved. Thus, cost reduction must come about through producing cells per unit area more cheaply. A separate alternative for producing low cost electricity from solar cells is to concentrate sunlight onto the cell, thus reducing the area of the cell per unit electrical output. Concentration systems also make available the option of using multiple cells to increase the overall conversion of sunlight to electricity. One two-cell concentration system has already demonstrated 28.5 percent efficiency.