The biggest drawback to any real or proposed sources of clean, renewable energy is their intermittency: the wind doesn’t always blow, the sun doesn’t always shine, and so the power they produce may not be available at the times it’s needed. A major goal of energy research has been to find ways to help smooth out these erratic supplies.
(Image: Professor Donald Sadoway and Materials Processing Center Research Affiliate David Bradwell observe one of their small test batteries in the lab. The battery itself is inside the heavily insulated metal cylinder at center, which heats it to 700 degrees Celsius. Photo: Patrick Gillooly)

Results from an ongoing research program at MIT show a promising technology that could provide a long-sought after way of levelling the load — at far lower cost and with greater longevity than previous methods. The system uses high-temperature batteries whose liquid components, like some novelty cocktails, naturally settle into three distinct layers because of their different densities. These layers form the positive and negative poles of the battery, as well as a layer of electrolyte in between. All three are composed of materials that are abundant and inexpensive, explains Donald Sadoway, the John F. Elliott Professor of Materials Chemistry at MIT.

To reach this discovery, Sadoway and his team have gradually scaled up their experiments over the last three years. Their initial tests used batteries the size of a shot glass; they then progressed to cells the size of a hockey puck, three inches in diameter and an inch thick. Now, they have started tests on a six-inch-wide version, with 200 times the power-storage capacity of the initial version.

The electric utility companies that would ultimately be the users of this technology, Sadoway says, “don’t care what the stuff is made of, or what the size is. The only question is what’s the cost of storage” for a given amount of power. “I can build a gorgeous battery to a NASA price point,” he says — but when cost is the primary driver, “that changes the search” for the best materials. Just based on the rarity and cost of some elements, “large sections of the periodic table are off limits.”

The team is continuing to work on optimising all aspects of the system, including the containers used to hold the molten materials and the ways of insulating and heating them, as well as ways of reducing the operating temperature to help cut energy costs. “We’ve discovered ways to decrease the operating temperature without sacrificing electrical performance or cost,” Sadoway says.

While others have researched similar liquid-battery systems, Sadoway says he and his team are the first to produce a practical, functional storage system using this approach. He attributes their success in this partly to the unique mix of expertise in a place like MIT: “People in the battery industry don’t know anything about electrolytic smelting in molten salts. Most would think that high-temperature operation would be inefficient.”

Sadoway and Materials Processing Center Research Affiliate, David Bradwell, have founded a company to bring this technology to commercialisation. Sadoway is on sabbatical this year to work with the company, Liquid Metal Battery Corp. “If this technology succeeds,” he says, “it could be a game-changer” for renewable energy.

For more information please visit MIT News