In many parts of the world, it’s cheaper to build new renewable-energy projects than fossil-fuel power plants. To fully replace carbon-based fuels, however, we need solutions to store large amounts of energy for when the sun doesn’t shine and the wind doesn’t blow.
A model of Malta’s 10MW pilot system.
The Boston-based startup Malta thinks it has one answer in the form of heat pumps, chilled chambers, and molten salt. On Dec. 19, it graduated from Alphabet’s secretive X lab and raised $26 million toward building its first full-scale pilot plant. The funding round was led by Breakthrough Energy Ventures, which was set up by Bill Gates with support from the likes of Jeff Bezos, Michael Bloomberg, Jack Ma, and Mukesh Ambani.
The idea is to use excess electricity from solar panels and wind turbines to run a large heat pump. “It’s essentially a refrigerator on steroids,” says Adrienne Little, the startup’s technical lead on heat exchangers. It extracts heat from a chamber full of antifreeze-like chemicals, lowering the temperature to –70°C (–94 °F). That heat is dumped in another chamber where salt—not exactly table salt, but similar—is heated to as high as 565°C (1,050°F). These insulated chambers hold the energy until it’s needed. That’s when a heat engine—essentially like a steam turbine inside a power plant—is used to convert the heat and the cold back to usable electricity. MORE