Bloomberg’s Mark Bergen reports:

Alphabet Inc.’s secretive X skunk works has another idea that could save the world. This one, code named Malta, involves vats of salt and antifreeze.

The research lab, which hatched Google’s driverless car almost a decade ago, is developing a system for storing renewable energy that would otherwise be wasted. It can be located almost anywhere, has the potential to last longer than lithium-ion batteries and compete on price with new hydroelectric plants and other existing clean energy storage methods, according to X executives and researchers.

Where does the salt and antifreeze come in?

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.

Molten salt is the medium used for several high capacity solar energy production facilities, so it is a somewhat proven technology. Should be interesting to see what the real-world data shows as far as efficiency goes once this system goes online.

One very interesting tidbit from the article states that California discarded more than 300,000 megawatt hours of solar energy due to a lack of viable storage options.