Rondo Energy launches the world’s first 100 MWh solar-powered thermal battery
World’s First Commercial Thermal Battery of 100 MWh Launched in California
In California’s Kern County, the world’s first commercial thermal battery installation with a capacity of 100 MWh has begun operation. Unlike conventional systems that store electric energy, this installation stores heat. Developed by Rondo Energy, the system captures power from a 20 MW solar farm and converts it into high-temperature heat, which is then used to produce process steam for the Holmes Western Oil Corp. facility.
A Thermal Battery Instead of an Electrical One
Unlike traditional BESS (Battery Energy Storage Systems) that store energy chemically, Rondo’s solution stores it as heat within ceramic cells, also known as firebricks. This highly durable material, resistant to extreme temperatures and widely used in industrial furnaces and foundries, can be heated above 1,000°C through resistive heating.
According to company data, the battery achieves a round-trip efficiency above 97%, and the entire process requires no rare metals or toxic chemicals. Rondo describes its technology with the phrase “only brick and wire.”
The system is charged exclusively during the cheapest hours of the day, which in California typically occur around midday when solar generation is abundant. At that time, the battery converts electricity into heat, which can then be stored and used for hours or even days.
10,000 Times the Capacity of a Home Heating System
The 100 MWh system is equivalent to about 10,000 household heating installations. The heat is stored within a four-story building, similar in appearance to an office block, and is used to produce steam that replaces part of the gas boilers used in oil extraction processes.
While its application in the oil sector raises some controversy, John O’Donnell, Rondo’s co-founder, calls it a pragmatic step toward real emissions reduction:
“We need to decarbonize the world as it exists today. Since oil will continue to be extracted for decades, at least we can make the process cleaner.”
The company estimates that the project will reduce CO₂ emissions by about 13,000 tons per year.
Industrial Heat – The Missing Piece of the Energy Transition
Roughly 20% of global energy demand comes from industrial heat used in sectors such as metallurgy, chemicals, cement, glass, and food processing. Until now, most of this heat has been produced through the direct combustion of fossil fuels.
Thermal battery systems like Rondo’s could transform this paradigm by converting cheap renewable electricity into stable, dispatchable industrial heat.
Research from Stanford University suggests that firebrick-based heat storage could reach a total capacity of 2.6 TWh in the United States, with 170 GW of peak output — potentially making it a key component of a 100% renewable energy system.
Between Market and Policy
Rondo is targeting storage service costs of around USD 30/MWh, a level competitive with lithium-ion batteries. The company emphasizes that through standardization and mass production — with its Thailand facility capable of producing 2.4 GWh of batteries annually — future projects will be cheaper and faster to deploy than the California pilot.
However, tariff structures and regulations remain a challenge. In most countries, industrial consumers buy electricity at fixed retail rates, without access to dynamic wholesale pricing. Yet, the economics of thermal batteries depend precisely on the ability to utilize surplus, low-cost renewable energy when prices drop to zero or even negative.
As Teresa Cheng from Industrious Labs notes:
“California is producing more cheap solar energy than it can use. Thermal batteries can capture that surplus, but new tariffs are needed to reward companies for using clean, low-cost power instead of letting it go to waste.”
Global Outlook
Rondo is simultaneously developing several projects in Europe — in Germany (chemical plant), Denmark (green industrial park), and the Iberian Peninsula (food processing facility).
Europe, with its high gas prices and strict CO₂ regulations, has become a natural market for renewable heat technologies.
In the United States, the path is tougher. Cheap fossil fuels and limited government support (especially after the Trump administration canceled hundreds of millions of dollars in decarbonization grants) have slowed the adoption of thermal technologies.
Meanwhile, in Europe, the European Commission is preparing a USD 1.2 billion pilot auction to support technologies for industrial heat decarbonization. Companies such as Brenmiller Energy from Israel are already integrating heat storage systems into grid services, providing flexibility to power networks.