100 MWh Brick Battery Uses Solar To Power Oil Production

Rondo Energy has commissioned its 100 MWh thermal battery, billed as the world's largest in capacity, power delivery, and round-trip efficiency. Powered by an on-site solar array, the Rondo Heat Battery (RHB) now operates alongside conventional gas-fired boilers, delivering continuous steam to the Holmes Western Oil Corporation facility in California.

Learn how the Rondo Heat battery works. Video used courtesy of Rondo Energy

Rondo's thermal battery technology offers an alternative storage mechanism for heat-intensive industrial processes. Unlike conventional electrochemical systems, the RHB converts electricity into high-temperature heat stored in dense refractory brick—without pressurized fluids or combustion-related emissions.

A 100 MWh industrial heat battery at Holmes Western Oil's facility in California. Image used courtesy of Rondo Energy

Rondo's Brick Storage Mechanism

Industrial heat pumps and boilers require a continuous electrical supply. The Rondo Heat Battery stores energy during low-cost periods and continuously releases it as high-pressure heat and steam. The system charges during the six cheapest hours of the day, drawing from either the grid or a dedicated solar photovoltaic (PV) array installed on-site at the California oil facility. Once charged, it delivers uninterrupted industrial heat, comparable in output to 10,000 home heating systems.

The RHB integrates easily into existing infrastructure, providing saturated or superheated steam required for a range of industrial processes. Holmes Western Oil Corp. operates multiple wells in Central California's oil region, producing about 1,962 barrels per day, according to ShaleXP data.

Built from brick and wire, the design uses abundant materials and eliminates the need for flammable or volatile components, reducing the risk of fires or toxic leaks. Inside the battery, thousands of tons of specially designed bricks are heated via thermal radiation to temperatures reaching 1,500°C, enabling storage for hours or days with less than 1% energy loss per day. The brick-based storage system enables efficient, emissions-free heat transfer that can replace fossil-fueled heat sources.

Graph of continuous heat from Rondo Heat Battery. Image used courtesy of Rondo Energy

Large-Scale Industrial Heat

The Rondo Heat Battery achieves a round-trip efficiency exceeding 97% and can store heat at temperatures over 1,000°C. It connects directly to existing steam flanges to deliver steam at pressures more than 100 bar (1450 PSI), according to Rondo Energy.

The company offers two commercial models: The RHB100, deployed at the Holmes Western Oil facility, provides 100 MWh of thermal storage and can discharge 7 MW of thermal power continuously. It accepts charging input up to 20 MWac, typically from the grid or an on-site solar source. The larger RHB300 model triples the storage capacity to 300 MWh, delivering up to 20 MW of continuous thermal output and charging at rates up to 70 MW. Like the smaller unit, it uses the same brick-and-wire storage architecture and high-temperature air circulation system.

Both models are designed for a lifespan of more than 40 years. Once charged, each unit supplies continuous, dispatchable heat, effectively replacing or supplementing fossil-fired boilers. The system also has the flexibility to operate in a combined heat and power setup, using steam turbines for both baseload electricity and zero-emission heat.

The heat battery process. Image used courtesy of Rondo Energy

Energy-intensive industries such as cement, steel, and chemicals are adopting thermal batteries like Rondo's to cut Scope 1 (direct) greenhouse gas emissions, without sacrificing uptime or overhauling existing equipment. The RHB provides dispatchable, fossil-free industrial heat, helping manufacturers meet carbon reduction targets while maintaining around-the-clock operation.

With no combustion byproducts, the RHB simplifies air permitting requirements and allows quicker deployment. In a case study with Calgren Renewable Fuels, the installation was commissioned without plant downtime and achieved a lower heat cost per MMBtu than the gas alternative.

Rondo Energy, backed by Bill Gates' Breakthrough Energy Ventures and several corporate investors, including Microsoft, currently has five full industrial-scale heat batteries in deployment worldwide, and is scaling its manufacturing capacity.