Solar thermal energy: The forgotten energy source

Solar thermal (ST) energy, using trough solar collectors, can be an environmentally friendly and economically competitive electric source for any part of the world (such as the USA) that includes large desert areas. Competitive ST involves trough solar collectors, which concentrate solar rays onto a flowing liquid able to sustain very high temperatures (⩾800°F) without exerting significant vapor pressure or decomposing. This allows the solar energy to be used to raise steam and drive turbines of electricity-generating plants directly, or to be harvested and stored as sensible heat in large underground ponds. The stored portion of the energy can be used instantaneously to meet variable power needs. This technology has been amply demonstrated by a 354 MWe modular plant (consisting of 9 ST units) that has been running in the Mojave Desert for the past 20 years. For intermediate loads (50% of the US electricity requirement) ST energy is already competitive with any new power plant, including old-fashioned coal power plants equipped with scrubbers. ST energy, using trough solar collectors, can become a major technical, financial, and political development.