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Fourth Power, a venture capital firm backed by Bill Gates, has developed a high-density thermal energy storage (TES) system based on thermophotovoltaic (TPV) cells. The technology, which is reportedly 10 times cheaper than lithium-ion batteries, is based on the American companys patented liquid metal heat transfer system.
To date, TES technology has struggled to get off the ground, but US-based Fourth Power is taking a new technology approach to solve some of the cost and scale issues. Its high-density TES system builds on its achievement of the Guinness World Record for high temperature in its patented liquid metal heat transfer system, which allows operation at nearly half the temperature of the sun.
“Until this innovation, I dont think there has been an innovation in thermal fluid infrastructure in almost 100 years,” he told pv magazine Fourth Power Chief Technology Officer Asegun Henry. “Using PVC pipes, steel or nickel alloys has been around for a long time, and thats what everyone does.”
He said Fourth Powers approach is based on knowledge of the struggles other TES companies have faced when trying to scale the technology.
“The key is our liquid metal handling infrastructure, which allows us to transfer heat at flows more than an order of magnitude higher than traditional thermofluid systems,” explains Henry. “This leads to higher power density and lower cost.”
Fourth Powers system converts renewable energy into heat, or thermal energy, in a totally closed system about the size of half a football field. The thermal battery heats liquid tin and moves it through a closed-loop piping system to heat stacks of carbon blocks until they glow red-hot.
The system then exposes the TPV cells to light and converts it into electricity. It is similar to traditional solar generation, but uses light from very hot graphite - up to 2,400ºC - instead of sunlight to produce electricity. The battery is sealed in an argon gas warehouse to maximize system life and ensure safety.
The system is modular and scalable by adding more carbon blocks to increase storage duration, allowing it to grow with the grid as renewable generation increases. Fourth Power claims it can meet current short-duration (five hours) and future longer-duration (100 hours) needs. The company considers its flexibility of downloading in a matter of seconds unique.
“We mainly focus on electricity and industrial heat,” explains Henry. “To be more concrete, we aspire for our technology to replace peaking plants in combination with the generation of renewable electricity.”
For electricity generation alone, Fourth Powers round-trip efficiency target is 50%.
“Our POS cells have already set a world record at 41%, and we have designs to reach 50%,” says Henry. “For cogeneration, efficiency approaches 100%.”
Finally, by using cheaper and more readily available materials, the total system cost is lower, allowing for energy storage that is 10 times cheaper than lithium-ion batteries ($25/kWh-e vs. $330 /kWh-e), according to the company.
On Tuesday, Fourth Power announced it had received $19 million in Series A funding to expand its TES technology. The investment round was led by the venture capital company DCVC, with participation from Bill Gates Breakthrough Energy Ventures and the Black Venture Capital Consortium.
“After more than 10 years of research and development, we are grateful to reach this crucial milestone in our journey thanks to our funding partners who recognized the innovation and potential of Fourth Powers thermal battery technology,” said Henry, who developed Fourth Powers thermal battery technology while a professor at Georgia Tech.
The funds will also finance the construction of a 1 MWh-e prototype facility outside Boston, scheduled for completion in 2026. Additionally, it will facilitate rigorous durability testing and expand the companys engineering team.
“Following the successful completion of the 1 MWh-e prototype facility, we plan to partner with utilities to conduct pilot projects designed for commercialization throughout 2026 and 2027,” Henry said. “We plan to reach our goal of installing 100 MWh-e systems at full scale in 2028.” |
