The solar power plant Abengoa Solar will build in Gila Bend, Arizona won’t rely on fancy photovoltaic panels. Mirrors focus the sun’s rays into tanks of heat-transfer oil, heating it to about 400°C, boiling water for a steam turbine.
The appeal of the system is its low cost and high scalability. MIT’s Technology Review says that, according to one expert, “solar thermal power will become cost competitive with other forms of power generation decades before photovoltaics will.” And even though solar thermal costs more than wind power (around 15 cents per kilowatt versus wind’s 8 cents per kilowatt), solar thermal energy, trapped in the form of heat, is much more easy to save up. Energy can be generated even when the sun isn’t shining—in the case of Abengoa’s Arizona plant, part of the heat doesn’t directly boil water but is transferred to molten salt tanks, where it can be stored to power the turbine for up to six sunless hours.