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of silicon, a very abundant element. The efficiency of conversion of the power in solar radiation to electricity has increased from 1 percent, for the first cells produced in 1976, to almost 12 percent for modest-area laboratory modules and almost 14 percent in 1987 for small-area laboratory cells. Higher efficiencies, estimated at 18 to 20 percent, may be attained in a few years with multilayer cells, each layer tuned to a different part of the solar spectrum.

Commercial Photovoltaics

The Alabama Power Company has a 100-kW amorphous-silicon generating field in operation at present. Efficiencies of currently available commercial photovoltaics range from 5 to 7 percent. Present-day manufacturing facilities are typically of modest capacity, on the order of 1 MW/yr, at a cost of $1.50 to $1.60 per peak watt. Within a few years, plants of 10-MW capacity per year may be on line. These plants are expected to produce cells of 6 percent efficiency for about $1.00 per peak watt. A 50-MW power plant to sell electricity to the Southern California Edison Company (Chronar Corporation, anticipating a photovoltaic cost of $1.25 per peak watt) and a 70-MW/yr production plant (ARCO Solar, Inc.) are in the planning stage. Looking to the end of the 1990s and the possibility of production levels of many hundreds of megawatts per year, Ogden and Williams (1989) project that costs could drop to the range of $0.20 to $0.40 per peak watt, based on reduced outlays for specialty glass, labor, and depreciation, together with commercial efficiencies increasing to 12 to 18 percent. Allowing for electrical wiring losses and for dirt and dust on the modules would reduce their overall efficiencies by an estimated 15 percent, that is, to 10.2 to 15.3 percent. Land costs, site preparation, array wiring, support structures, and other construction represent additional area-related costs that would come to about $50/m2 with present technology, but economies of scale might bring these down to $33/m2.

On the other hand, these figures are pertinent for the U.S. Southwest, and supplying power to other parts of the country means finding means other than electric power lines for energy transport. Also note that these costs are much lower than that used in the Mitigation Panel's analysis as described in Appendix J. Rather than using projections of cost, the panel made a deliberate decision to use only current cost in estimating the cost-effectiveness of different energy options.

Hydrogen Costs

The cost for the electrolytic production of hydrogen depends on the capital cost of the electrolyzer and the cost of the DC electricity to run it. There



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