By enabling the storage of solar energy for later use, BrightSource says the SolarPLUS system makes it possible for utilities to tap sun power to produce electricity later in the day and after the sun sets, when demand is higher. The option of storing solar energy also helps to make renewable power more affordable, offers utilities greater flexibility for meeting demand and provides balancing capabilities that can make the grid more stable, according to BrightSource.
The company claims SolarPLUS is also more efficient and cost-effective than parabolic-trough solar thermal technologies because the system can reach higher temperatures and higher pressure operating levels: up to 540 degrees C and 140 bar of pressure, compared to 400 degrees C and 100 bar of pressure of parabolic trough plants.
“Electricity markets with high penetration levels of intermittent resources are starting to place significant value on those resources that can provide clean energy as well as operational flexibility and reliability services to the grid,” said Udi Helman, director of economic and pricing analysis for BrightSource Energy.
The SolarPLUS system directs solar power-generated steam to a heat exchanger, where molten salts — sodium nitrate and potassium nitrate — are heated up even more to store energy for future use. Later, when the stored energy is needed, the heat from the molten salts is used to generate steam to run a steam turbine that generates electricity.