Another Dawn For Solar Power

In this article, President Jimmy Carter held the first and only press conference on the White House roof. Atop the West Wing, he unveiled a $28,000 solar cell system that captured the sun's energy to provide hot water for the White House. He also launched a sweeping drive aimed at harnessing the sun, the wind, and other renewable resources to generate 20% of America's electricity by 2000. There are two basic concepts for tapping the sun's energy: collect its heat or convert its light. The solar-thermal approach uses mirrors to reflect the heat energy from a large area onto a small space, such as a pipe filled with a fluid like molten salt. Once the fluid's temperature has been raised to hundreds of degrees, it can be used to boil water and produce steam for a conventional generator. With the other approach, called photovoltaics, a semiconductor -- typically silicon -- absorbs the photons streaming from the sun and reacts by giving off a flow of electrons, or electricity.