Solar Two, a solar tower project in the Mojave desert at Daggett, California, is to close down after exhausting three years of sponsorship from the US Department of Energy (DOE) and a consortium led by Los Angeles utility Southern California Edison. However, the project has been judged a success, according to the US Energy Secretary.

Solar Two used nearly 2000 mirrors to focus sunlight onto a heat absorbing reservoir of a molten salt on top of a tower. This heat was used to drive a turbine and produce electricity.

The molten salt was able store massive amounts of energy, sufficient to allow the plant to operate through the hours of darkness. During its life it has generated 8500 MWh of power.

The 10 MWe pilot scale power plant received a total of $55 million in funding. The sponsors believe the demonstration project has shown the design to be commercially viable even though it is not immediately marketable in the USA. According to the DOE, other countries such as Brazil, Egypt and Spain have shown interest in the technology.

Solar Two was the successor to Solar One, the first pilot scale solar tower to operate at Daggett between 1982 and 1986. Solar one used a water/steam cycle which lacked the ability of the molten salt system to store energy effectively.