Later in the article: "Robert Laughlin, a Nobel prize-winning physicist whose research laid the foundation for Malta, is now a consultant on the project. He met X representatives at a conference a few years ago. They discussed the idea, and the lab ultimately decided to fund the project and build a small team to execute it. Laughin has signed off on the team's designs, and he said his theories have been working with the prototype."
"The system mixes an established technique with newly designed components. "Think of this, at a very simple level, as a fridge and a jet," said Julian Green, the product manager for Malta.Alphabet Wants to Fix Renewable Energy’s Storage Problem — With Salt - Bloomberg
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.
Scientists have already proven this as a plausible storage technique. Malta's contribution was to design a system that operates at lower temperatures so it doesn't require specialized, expensive ceramics and steels. "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.""