“Using thermophotovoltaic (TPV) cells, Fourth Power, supported by Bill Gates‘ venture capital business, has made significant progress in high-density thermal energy storage (TES).This technology, claimed to be 10 times more cost-effective than lithium-ion batteries, relies on Fourth Power’s patented liquid metal heat transfer system.
While TES has faced challenges in adoption, Fourth Power is addressing cost and scale issues with its innovative approach. The high-density TES system builds on the company’s Guinness World Record for achieving high temperatures in its liquid metal heat transfer system, operating at nearly half the sun’s temperature.
Fourth Power’s Chief Technology Officer, Asegun Henry, explained that the key lies in their liquid metal handling infrastructure, enabling heat transfer at significantly higher fluxes than traditional systems. This results in higher power density and lower costs.
The system converts renewable energy into heat within a fully enclosed space about half the size of a football field. Liquid tin is heated and circulated through a closed-loop piping system, heating stacks of carbon blocks until they glow white hot. TPV cells then convert the emitted light into electricity, using high-temperature graphite rather than sunlight. The entire system is sealed in argon gas to enhance longevity and safety.
Notably, the system is modular and scalable, allowing for the addition of more carbon blocks to increase storage duration. Fourth Power claims to meet both short-duration (five-hour) and long-duration (100-hour) energy storage needs, with the flexibility to discharge within seconds.
Asegun Henry emphasized their focus on replacing peaker plants with renewable electricity generation, targeting a roundtrip efficiency of 50% for power generation alone. The TPV cells have already set a world record at 41%, with plans to reach 50%. Co-generation efficiency is near 100%.
The company’s use of readily available and less expensive materials contributes to an overall system cost that is 10 times cheaper than lithium-ion batteries, estimated at $25/kWh-e compared to $330/kWh-e.
In a recent announcement, Fourth Power disclosed a $19 million Series A funding round to scale its TES technology. DCVC led the investment, with participation from Bill Gates’ Breakthrough Energy Ventures and the Black Venture Capital Consortium. The funds will support the construction of a 1 MWh-e prototype facility near Boston, set for completion in 2026, along with durability tests and expansion of the engineering team.”
