Over the past 12 weeks, the California startup Rondo Energy runs what he calls the world's largest thermal battery. Rondo's system converts low-cost, renewable electricity into heat that can be used on demand in industrial processes.
This is different from most next-gen devices. energy storage strategies that provide power to the grid in the absence of sun and wind. Instead, Rondo's system aims to help decarbonize high-emitting industries such as steel and cement.
The system works like a toaster crossed with a blast furnace. Electricity from solar panels heats iron wires like those used in a toaster. They heat hundreds of tons of refractory bricks to temperatures of up to 1500 °C. After four to six hours of charging per day, the heat can be released as air or steam without combustion or emissions.
To remove the heat, a circulation fan is turned on to force air through the stack of bricks and heat it to over 1000°C before being released through the outlet. The rate of heat delivery can be controlled by adjusting the air flow. The battery can produce steam instead of heat by injecting water into an attached chamber through which heated air passes before leaving the battery through an outlet.
The real problem in thermal energy storage is not keeping it warm; According to him, it is able to charge quickly and then continuously release heat at the same temperature. John O'DonnellDirector of Innovation at Rondo Energy. Rondo's thermal battery structure, which O'Donnell describes as a “three-dimensional chessboard of bricks and open chambers,” maintains a constant temperature and allows fast charging. “We can turn charging circuits on and off as quickly as you turn a toaster on and off,” says O'Donnell. “This way we can be flexible.”
In Rondo's first project, its 100-megawatt-hour battery provides heat enhanced oil recovery a facility operated by Holmes Western Oil Corp. in Kern County, California. The battery, about the size of a small office building, is powered by a 20 MW off-grid solar array built for this purpose. It converts clean electricity into heat and then generates steam, which is injected into oil wells, heating the oil so that it liquefies and becomes easier to flow, increasing production.
Holmes Western Oil had previously achieved this with a gas boiler. Reducing it would save Holmes just under 13,000 tons of CO2.2 According to Rondeau, annual emissions as well as lower costs. “Oilfield steam production is the second largest share of industrial heat in the state,” O'Donnell says.
Rondeau's decision to use his first commercial-scale, emissions-reducing battery to extract fossil fuels. caused some controversy. Critics say the deployment clean technologies improving or prolonging fossil fuel production is counterproductive.
Thermal Batteries for clean industrial heat
Some other companies developing thermal batteries for industrial use. Antora Energy makes it modular Carbon thermal batteries the temperature of which can reach more than 1500 °C, and they are used in pilot industrial sites. Energinest is conducting early commercial installations of its concrete-based thermal modules and is collaborating with Siemens The energy will be scaled across Europe. Kalectraultra-high temperature systems are at an experimental stage, and EarthEn Energy launched its modular low-temperature thermal batteries in July.
These companies focus on heat because it plays a central role in the production of staples such as steel, cement, food and chemicals. Many of these manufacturing processes operate continuously and maintain high temperatures for weeks or months, ranging from 72 °C for milk pasteurization up to more than 1000 °C for steel production or cement.
The cheapest and most effective way to obtain constant heat has long been to use fossil fuel; nothing burns as slow and hot as coal or natural gas. Their energy densityreliability and low cost made them difficult to replace. However, the share of industrial heat accounts for about 18 percent from greenhouse gas emissions and more than 20 percent world energy consumption. Thus, innovators seeking to decarbonize these industrial sectors have a difficult time.
But solar energy becomes cheaper. In 2024, California's sunny fields created almost the same amount of electricity as gas plants. “Thanks to advances in the wind and solar industries, we now have volatile grid prices that are cheaper than fuel in many places in the world,” O'Donnell says. In some places, so much clean energy is generated that the grid cannot absorb it all, causing negative effects. electricity prices for several hours a day.
How can thermal batteries scale?
Thermal batteries that provide heat face a number of problems. To achieve scale, industrial customers must buy wholesale electricity from renewable sources at times of day when it is cheap, requiring real-time dynamic pricing. Many states allow industrial customers to purchase electricity only at fixed daily rates. “We really want to see the regulatory framework modernized,” O'Donnell says.
The price of natural gas also plays a role. It's relatively inexpensive in United States thanks to slate gas from hydraulic fracturingbut if its price rises due to exports or other factors, batteries like Rondo's could provide a cheaper source of heat. This is already the case in European countries such as GermanyWhere natural gas price has increased sharply over the past three and a half years.
Additionally, thermal batteries can be difficult to integrate into existing industrial infrastructure. Not every facility has the space for an office building-sized battery and a separate solar panel. The high upfront costs of batteries and the fact that they are still a largely unproven technology will make some potential customers reluctant to try them.
However, thermal batteries like Rondeau's are a promising solution for decarbonizing the industrial sector. ” thermal storage The market is absolutely capable of accelerating to have a significant impact,” says Blaine Collison, chief executive Joint work on renewable thermal energya coalition focused on decarbonizing thermal energy. “When I look at some of the fundamental characteristics of the technology—relatively simple materials, the ability to use renewable electricity, modularity—I see scale.”
This article was updated on October 31, 2025.
Articles from your site
Related articles on the Internet
