SolarReserve: Salty Solar Thermal

Aerospace company Hamilton Sundstrand, a subsidiary of United Technologies Corp., today announced the formation of a new solar thermal venture, SolarReserve. Hamilton Sundstrand is working with private equity management company U.S. Renewables Group to use a molten salt heat storage technology developed by Rocketdyne, which United Technologies acquired in 2005. SolarReserve plans to have its first solar plant online by the end of 2010.

The technology solves the problem of solar power’s intermittent power-generation ability by storing energy in the form of heat in molten salt. Mirrors reflect and concentrate sunlight onto a central receiver that uses Rocketdyne’s heat transfer technology, which was originally developed for use in liquid-fuel rockets. The extremely hot salt is then piped through another heat exchanger, making steam that in turn powers traditional steam turbines. (The picture above is from eSolar, the solar thermal company Google is partnering with for its “RE Less Than C” program, but uses a similar setup as SolarReserve’s proposed plant design, with a central collection tower surrounded by heliostats.)

Last month, SkyFuel unveiled plans to use its “SkyTrough” technology to heat tubes filled with a molten salt in reflective parabolic troughs. Though different from SolarReserve’s approach, both technologies are classified as “concentrated solar power,” or CSP.

Rocketdyne’s concentrated solar power and molten salt storage systems were originally demonstrated over 10 years ago in a facility called “Solar II,” which was built in conjunction with the Department of Energy in Barstow, Calif. That facility was able to generate 10 MW of peak power; SolarReserve plans an installation that could generate as much as 500 MW of power.

Solar thermal, which with current technology can generate 20 to 40 percent efficiency levels (compared with photovoltaic’s current 15 to 22 percent efficiency), will see big gains in 2008 as numerous utility-scale installations are scheduled to come online. According to Emerging Energy Resource, the top five companies bringing on the most solar-power capacity this year are all solar thermal companies: Stirling Energy Systems, SkyFuel, Solel, Ausra and BrightSource, in that order. Emerging Energy Resource estimates that there are 5,800 MW of solar thermal installations planned worldwide right now and sees $20 billion in potential investment in solar CSP in the next five years.

The Southwest states all have minimum solar requirements in their renewable portfolio standards which will help solar thermal installers. Nevada requires 20 percent of its power to come from solar sources by 2015; Arizona, 15 percent by 2025; New Mexico, 20 percent by 2020; and Colorado, 20 percent by 2020. Solar thermal plants will be the only way for these states to meet those goals. SolarReserve, however, is getting into the game a little late; it will have to move quickly to secure these utility-scale contracts for which the aforementioned companies are all jockeying.