BrightSource Energy Inc. has released details of its latest large-scale solar thermal power plant design that utilises molten-salt technology for storing surplus energy, allowing plants to operate at night.
Generating electricity after dark and overcoming intermittency of supply is one of the biggest hurdles for the large-scale solar power sector worldwide. Molten-salt "batteries" are becoming increasingly common in solar thermal power stations as a way of addressing these issues.
Brightsource says their SolarPLUS solution offers a higher storage capacity and is more efficient than competing technologies, including concentrated photovoltaics (CPV) and wind energy.
BrightSource’s solar thermal plants follow a traditional design in which a field of mirrors, called heliostats, track the sun across the sky and focus sunlight onto a boiler mounted on a tower. Water inside the boiler is vaporised at a temperature of 540 degrees Celsius, and the steam drives a turbine to produce electricity.
In the SolarPLUS model, some of the steam is directed to a heat exchanger and directed to two tanks holding the molten-salts. The so-called "solar salts" are composed of 60% sodium nitrate and 40% potassium nitrate. By superheating the tanks during the day, they can be used to produce steam during the night, or when sunlight conditions are unfavourable.
"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 Dr. Udi Helman, Director of Economic and Pricing Analysis for BrightSource Energy.
BrightSource is currently contracted to deliver approximately 2.6 gigawatts of solar thermal technology. In April, search giant Google announced it was investing USD$168 million into BrightSource Energy’s Ivanpah Solar Electric Generating System (ISEGS) in the Mojave Desert in California.
