Bill Gates’ VC backs thermal energy storage startup: Bill Gates’ Breakthrough Energy Ventures is backing US-based thermal energy storage startup Fourth Power, Bloomberg reports. The USD 19 mn Series A funding round was led by DCVC along with Breakthrough Energy and Black Venture Capital Consortium. The capital will be channeled toward expanding the firm’s engineering team, research and development, and establishing a 1 MWh e-thermal plant in Boston in 2026.

What does Fourth Power do? The company stores excess renewable power as thermal energy in an enclosed liquid metal heat transfer system roughly the size of half a football field, and then stores it in a thermal battery system to be used when needed. Liquid tin is then pumped through a closed-loop plumbing system to transport the energy throughout a utility-scale battery.

Storing the sun in a box: Fourth Power uses thermophotovoltaic panels to turn the light emitted by the plumbing system — which reaches up to 2.4k°C — into power for the grid. “At almost half the sun’s temperature, we are essentially storing the sun in a box,” the company notes.

Ten times cheaper than lithium-ion batteries: Fourth Power’s thermal battery system can store for over a month excess power from renewables that would have otherwise gone to waste, discharging it over a period from a few hours to a few days, according to Business Wire. The energy is stored at a cost of USD 25/KWh, which is 10 times cheaper than lithium-ion batteries, the company explains.

Potential to 20x storage capacity: “By adding graphite blocks to increase storage duration, we provide a modular, scalable solution that can meet today’s short-duration (5-hour) needs and the long-duration energy storage (100-hour) needs of tomorrow,” the company notes.

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