Both concentrated solar energy projects use the molten-salt power tower technology developed by Pratt & Whitney Rocketdyne.
SolarReserve, a developer of utility-scale solar power projects, says it is proceeding with purchases of long-lead materials and equipment as it advances in financing arrangements with the U.S. Department of Energy’s (DOE) loan-guarantee program for its Crescent Dunes Solar Energy Project in Tonopah, Nev., and Rice Solar Energy Project in Riverside County, Calif. Both projects are set to break ground in 2011 after receipt of final environmental permits and completion of the DOE financing activities.
Both concentrated solar energy projects use the molten-salt power tower technology developed by Pratt & Whitney Rocketdyne. The technology features integrated energy storage to generate electricity on demand, even after daylight hours.
The 110 MW Crescent Dunes Concentrating Solar Power project has been designated by the U.S. Department of the Interior (DOI) as a fast-track applicant for right-of-way use of federal lands managed by the Bureau of Land Management. The project, which secured a 25-year power purchase agreement (PPA) with NV Energy in 2009 and was approved by the Public Utility Commission of Nevada in July, has completed its environmental impact study and is expected to receive a record of decision from the DOI before the end of the year.
The 150 MW Rice Concentrating Solar Power project is currently under review by the California Energy Commission, with a final decision also anticipated before the end of the year. The project has secured a 25-year PPA with Pacific Gas & Electric Co. that was approved by the California Public Utilities Commission in September.
SolarReserve applied for participation in the loan-guarantee program under the DOE’s July 2009 solicitation for innovative renewable technologies pursuant to Section 1705 of the Energy Policy Act of 2005. Both projects successfully advanced through Parts I and II of the DOE’s extensive application-review process. The DOE and SolarReserve are advancing the arrangements for the financing terms and conditions available under the Section 1705 program.
SolarReserve was formed to solve two of the fundamental barriers of renewable energy: scalability and storage. Unlike hydroelectric, geothermal, biomass, and other renewable energy technologies that use limited renewable fuel sources, SolarReserve’s power plants draw their heat from the sun – earth’s ultimate source of clean energy. And unlike wind and photovoltaics, SolarReserve’s power plants can deliver power whenever it is needed, either 24 hours per day or only during "peak" demand. By overcoming these two key barriers, SolarReserve enables utility-scale, clean, renewable electricity generation.
One might guess that such revolutionary technology is an unproven, unrealistic concept dreamed up by optimistic scientists. Actually, this technology has been proven and demonstrated by one of the world’s leading technology conglomerates, United Technologies. United Technologies’ subsidiary, Rocketdyne, demonstrated the technology at the Solar One and Solar Two power plants in Southern California. United Technologies has granted SolarReserve the proprietary technology know-how and an exclusive worldwide license to develop power plants using this proven technology.
SolarReserve’s other founding partner is US Renewables Group, a $575 million private equity firm exclusively focused on renewable power and clean fuel projects. US Renewables Group has extensive experience developing successful renewable power projects, such as the Bottle Rock geothermal power plant and the Niagara biomass power plant. US Renewables Group will provide SolarReserve with the financing and development expertise to successfully implement this revolutionary technology worldwide.
With technology and engineering support from United Technologies and development and finance support from US Renewables Group, SolarReserve is poised to revolutionize the electricity industry. In addition to its backers, SolarReserve has assembled a strong team to achieve its objectives, including former executives at United Technologies, head engineers from Solar Two, leading renewable power developers, and the legal and financial experts required to build projects of such magnitude.
SolarReserve will build power plants designed as Solar Power Towers. This configuration captures and focuses the sun’s thermal energy with thousands of tracking mirrors (called heliostats) in a two square mile field. A tower resides in the center of the heliostat field. The heliostats focus concentrated sunlight on a receiver which sits on top of the tower.
Within the receiver, the concentrated sunlight heats molten salt to over 1000 degrees Fahrenheit. The heated molten salt then flows into a thermal storage tank where it is stored, maintaining 98% thermal efficiency, and eventually pumped to a steam generator. The steam drives a standard turbine to generate electricity.
This process, also known as the "Rankine cycle" is similar to a standard coal-fired power plant, except it is fueled by clean and free solar energy. Other than the few unique components noted below, SolarReserve’s power plants are comprised of available materials, such as mirrors, and established technologies, such as steam generators and turbines. This will enable SolarReserve to provide electricity at or below prices from traditional sources such as coal or natural gas.
The unique components in SolarReserve’s power towers are the molten salt storage loop and the power tower central receiver. The molten salt storage loop enables the plant to generate electricity whenever it is needed – 24 hours per day or during "peak demand" periods. Molten salt is an efficient and inexpensive medium to store energy.
The salt used in the process is an environmentally friendly mixture of sodium and potassium nitrate, the same ingredients used in garden fertilizer. The other unique component is the power tower central receiver. This high heat flux hardware represents a unique blend of liquid rocket engine heat transfer technology and molten salt handling expertise. United Technologies has decades of experience with these technologies in both land-based and space applications, and its support will be invaluable to SolarReserve in developing power plants utilizing this revolutionary technology.