Startup Utilizing Liquid Tin to Store Energy Receives Support from Bill Gates’ Breakthrough Energy

A new thermal storage startup is receiving support from Bill Gates’ Breakthrough Energy Ventures, as the company expands its investments in long-duration power backup.

Fourth Power converts renewable electricity into heat and stores it for future use. A thermal battery based on liquid tin transfers heat at very high temperatures to carbon block stacks, which can later be discharged as electricity through thermoelectric cells. This could help solve the periodicity problems of renewable energy sources.

Investor DCVC led the Series A with $19 million, with participation from Breakthrough and Black Venture Capital Consortium. Fourth Power plans to build a prototype plant in Boston that can store the equivalent of one megawatt hour of energy, enough to power about 1,000 homes.

Läpimurto has supported several other thermal energy storage startups, including Antora Energy, Malta and Rondo, in an effort to help emerging companies scale to develop low-cost utility renewable grids. Fourth Power’s technology can be up to 10 times cheaper than other approaches to long-term energy storage, said Carmichael Roberts, who chairs Breakthrough’s investment committee.

“Thermal energy storage needs to be there for the promise of a true renewable grid, but it’s not yet fully developed,” he said. “We see it as kind of an open field where we can make a big difference.”

Lithium-ion batteries are currently the most common form of energy storage. However, most lithium-ion batteries only have a storage capacity of a few hours. The need for long-life storage technologies increases as renewable energy brings more electricity to the grid. This helps to build up renewable energy stores for use when solar power plants and wind turbines are not producing. Saving energy as heat is one of the options that can help store a significant number of hours or days.

“Thermal storage is an attractive technology because it can be deployed flexibly, is relatively energy-dense and can provide additional services,” BloombergNEF analyst Stephanie Diaz said. According to data compiled by BNEF, startups using this technology raised $96 million in the three months ending in September, the most for any quarter this year.

Breakthrough has also supported startups exploring other long-term power storage technologies, including ESS and Form Energy. Both companies rely on electrochemical processes.

“We try to look at early-stage things where the founders are very talented, but with some help they can develop something significant,” Roberts said. “We’re just as excited about things outside of heat.”