The solar project will be constructed on approximately 1,500 acres of private land near Blythe. The project will use a concentrated solar power (CSP) design with molten salt storage technology from Pratt & Whitney Rocket
The California Public Utilities Commission (CPUC) approved a power purchase agreement (PPA) for PG&E Corp., the owner of California’s largest utility, to receive power from a 150-MW solar-thermal project in California’s Sonoran Desert.
The developer of the Solar Rice Energy Project is SolarReserve LLC., and the term of the PPA is 25 years, commencing June 1, 2016. SolarReserve originally announced the agreement with PG&E in December 2009.
The solar project will be constructed on approximately 1,500 acres of private land near Blythe. The project will use a concentrated solar power (CSP) design with molten salt storage technology from Pratt & Whitney Rocketdyne.
According to CPUC resolution, cost recovery for the amended PPA has been approved for three reasons: First, the price and value of the Amended PPA compare favorably against shortlisted bids resulting from PG&E’s 2009 RPS Solicitation. Second, the GCOD has been extended to June 1, 2016 which is in better alignment with PG&E’s RPS portfolio need. Third, the Rice Solar project will be utilizing molten salt storage technology, giving it the ability to strategically shift and optimize load based on changes in electricity demand and the potential need for grid stabilization.
It’s worth noting that CPUC has taken into account the technology to be developed in the plant, especially the molten salts thermal energy storage system, which provides dispatchable and stable energy to the grid. This is a key point as new projects to be deployed in California should aim to include thermal energy storage as a differentiatior with other renewable sources, including Concentrated Solar Power without energy storage.
Commissioner Mark J. Ferron stated "It’s critical that the State invest in technologies such as concentrated solar combined with molten salts storage", "In my personal view, projects like solar Rice will be important to demonstrate that we can form and shape intermittent renewables with clean technology, not just with fossil technologies".
In turn, Commissioner Michael Florio said "this is expensive, there’s no getting around it, but I think this technology is something that is worth investing in, using molten salts as the medium (…) rather than heating water (…) to reheat the salts, is hopefully more efficient technology, I thonk time will tell which is the best approach", " 8 to 10 hours of fully dispatchable storage is quite impressive and offers significant benefits to the system", in clear reference to the different tower technologies being deployed in the US; BrightSource’s technology, using water as Heat Transfer Fluid (HTF) (without energy storage, by now) and SolarReserve’s which uses molten salts as HTF and storage medium.
Although the approval by CPUC commissioners was unanimous, and it was presented as "probably one of the least controversial resolution in a while" by CPUC Energy Division Director, Edward Randolph, some protests where made. the Division of Ratepayer Advocates (DRA) asked the Commission not to approve the amended PPA maily due to "uncompetitive price" and that "PG&E lacks portfolio need for the project". Californians for Renewable Energy stated in the same terms.
Thousands of mirrors will focus sunlight onto a central tower containing molten salt, which is heated from 500 to over 1,000 degrees Fahrenheit. When electricity is needed, day or night, the high-temperature molten salt flows into the steam generator, as water is piped in from the water storage tank, to generate steam. After the steam is used to drive the steam turbine to generate power, the steam is condensed back to water and returned to the water holding tank, where it flows back into the steam generator when needed.
Once the hot salt is used to create steam, the cooled molten salt is then piped back into the cold salt storage tank, where it will then flow back up the receiver to be reheated as the process continues.
The molten salt system includes as much as 10 hours of energy-storage capability. The estimated cost is approximately $600 million, and construction may begin early next year, according to the CEO of SolarReserve.
In September 2011, SolarReserve began construction in Nevada on a similar project, the 110-MW Crescent Dunes Project, which is scheduled to be completed late this year.