THE PHOTOVOLTAIC OPTION - WHAT IS NEEDED? A power satellite which gathers its energy through the use of large fields of solar cells also is an attractive option — if certain technological breakthroughs occur. Basically, there are three interdependent areas in need of technological advances in excess of those seen under existing technological growth curves. Each affects costs of a power satellite system. They are: 1. Conversion efficiency. The efficiency of present solar cells dictates an orbiting field of collectors far larger than the field of reflectors needed for a thermal engine system. 2. Cell thickness and weight. The efficiency of solar cells presently is relative to the cell's thickness. Additionally, these cells must be covered while being transported through the Van Allen belt to geosynchronous orbit. The weight of covered thick cells would have a serious impact on the power satellite's transportation system. 3. Cost. Solar cells now are custom-made in small numbers. Dramatic advances in manufacturing technology must be made if they are to be made in the large numbers needed in a power satellite system. These two charts show the existing technology in solar cells in terms of mass, efficiency and lifespan.
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