The new Venture Capital (VC) firm Breakthrough Energy Ventures (BEV) only invests in technologies they vet as both “scientifically feasible at scale” and with the potential to reduce “at least half a gigaton of greenhouse gases every year.”
Along with Alfa Laval and Concord New Energy Group, BEV has invested $26 million in early stage funding for Malta, a storage start-up incubated by X.-company (formerly Google X) to build a standalone thermal energy storage pilot.
Malta’s technology concept is simple. Thermal energy storage is charged with electricity from the grid the same way as any battery, stored cost-effectively in steel tanks and discharged as electricity back to the grid when needed later.
“We plan to build a pilot plant with 10MW power and at least 6 hours of storage duration, depending on customer specifications,” Malta engineer Sebastian Freund told SolarPACES this week. As the first step towards commercialization, Malta expects to be able to attract enough investors over the next three years to complete their 80MWh thermal energy storage pilot.
Standalone thermal energy storage
The technology is based on CSP’s long-proven low-cost thermal energy storage using molten salts. A mix of sodium nitrate and potassium nitrate is heated by the sun in a CSP plant, raising the temperature from a warm liquid at 290C to a heat of 565C, with the heat driving a power block.(How CSP storage works)
Because of the low cost compared to battery storage, the idea of building standalone thermal storage is not new. The world’s largest steel producer, Arcelor Mittal has already begun to decarbonize steel making using thermal storage in slag and German research institute DLR has proposed siting thermal “batteries” of molten salt at decommissioned coal plants.
DLR’s proposed thermal storage would generate and receive and deliver power back to the grid by utilizing the former coal plants existing infrastructure: its steam cycle and transmission in and out. But when thermal storage is converted to electricity, the steam cycle in coal plants has efficiency limits in the 40% range. So Malta goes one step beyond the DLR concept of repurposing decommissioned coal plants.
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