Alphabet Wants to Fix Renewable Energy’s Storage Problem — With Salt

https://www.bloomberg.com/news/articles/2017-07-31/alphabet-wants-to-fix-renewable-energy-s-storage-problem-with-salt

... In the first half of this year, California tossed out more than 300,000 megawatts produced by solar panels and wind farms because there's no good way to store it. That's enough to power tens of thousands of homes. About 4 percent of all wind energy from Germany was jettisoned in 2015, according to Bloomberg New Energy Finance. China throws out more than 17 percent...

...Two tanks are filled with salt, and two are filled with antifreeze or a hydrocarbon liquid. The system takes in energy in the form of electricity and turns it into separate streams of hot and cold air. The hot air heats up the salt, while the cold air cools the antifreeze, a bit like a refrigerator. The jet engine part: Flip a switch and the process reverses. Hot and cold air rush toward each other, creating powerful gusts that spin a turbine and spit out electricity when the grid needs it. Salt maintains its temperature well, so the system can store energy for many hours, and even days, depending on how much you insulate the tanks....

...The thermodynamic physics are well-known to anyone who studied it enough in college," Green said. "The trick is doing it at the right temperatures, with cheap materials. That is super compelling."...