Soaking up excess clean power with heat batteries
The holy grail for thermal storage — the thing that will make it broadly cost-competitive with fossil-fueled heating — is tapping into cheap, clean power.
That’s because the cost of electricity is ultimately what dictates whether a thermal battery makes financial sense. But unlike fossil fuels, electricity prices vary not just from week to week, but from hour to hour. That makes it tricky for would-be customers to evaluate whether to stick with a gas boiler or to make a bet on an electricity-powered system like Rondo’s.
Solar and wind, however, reliably generate power at a very low cost. In some parts of the U.S. and the world, the amount of renewable energy available exceeds electricity demand for hours at a time, driving wholesale power prices to zero or even negative.
Storing this excess carbon-free electricity as heat can significantly cut costs for owners of thermal storage systems, O’Donnell said. The challenge for providers of the tech is to get utilities, regulators, and energy-market operators to allow industrial customers to access those low or negative energy prices, O’Donnell said. Today, most industrial sites buy their electricity from utilities at retail rates that don’t pass through these wide wholesale fluctuations.
This is especially true in California, where thermal batteries are “in many ways the perfect solution,” said Teresa Cheng, California director at Industrious Labs, an advocacy group focused on cutting emissions from heavy industry.
Solar power is close to overtaking fossil gas as the state’s predominant source of electricity. Much of it is generated at times when there isn’t enough demand for electricity to use it or enough battery capacity to save it for later, forcing the state’s grid operator to curtail increasing magnitudes of solar.
Thermal batteries could soak up that cheap renewable energy while helping industries decarbonize, Cheng said. But “to make this work, we need state leaders to fix industrial electricity rates so they actually reward companies for using cheap, clean power instead of letting it go to waste.”
Holmes Western Oil Corp. is in an unusual position of owning enough land surrounding its facility to build its own 20-MW solar array without connecting to the grid. That “islanded” system allows the company to self-supply solar power at a cost that justifies the project, O’Donnell said.
But that’s a rare occurrence. Most industrial customers will need to source power from the grid — and opportunities for them to access electricity at wholesale prices are few and far between.
Doron Brenmiller, cofounder and chief business officer of Israel-based thermal energy storage provider Brenmiller Energy, said Europe is moving more quickly than the U.S. to support heat batteries, including a number of projects his company is building. He cited the European Commission’s upcoming $1.2 billion pilot auction to fund efforts to decarbonize industrial process heat.
“The utilities in Europe are also very engaged in this space,” he said. Brenmiller has partnered with German energy-trading firm Entelios to integrate its growing roster of industrial thermal storage projects into a variety of “short-term flexibility markets” for specialty grid services like frequency regulation and demand response.
But getting the first large-scale projects up and running remains the most important next step for the industry, he said. Brenmiller expects its first industrial-scale project, a 32-megawatt-hour thermal storage unit at a beverage-processing plant in Israel, to start operations before the end of 2025. A second 30-megawatt-hour system at a pet-food factory in Hungary is scheduled to begin running in 2026.
“All the eyes of clients and investors are on these first few big projects,” he said. “We’ve done pilots, even at scale. But these are the real thing.”