'World's largest' industrial heat battery runs purely on solar energy
Rondo Energy has officially launched commercial operations of what it calls the world’s largest industrial heat battery.
The 100 MWh system is now running at a Holmes Western Oil facility in California, powered entirely by an onsite solar array.
The project shows how renewable energy can supply continuous high-pressure heat and steam to power-heavy industrial processes, a step forward in decarbonizing one of the most energy-intensive sectors.
A breakthrough for industrial heat
The Rondo Heat Battery stores solar energy during the day and delivers consistent thermal energy to the facility around the clock. Over a 10-week testing period, the system achieved more than 97 percent round-trip efficiency while maintaining temperatures above 1,000 °C (1,832 °F).
According to the company, the 100 MWh unit produces as much heat as 10,000 household heating systems.
“The Rondo Heat Battery is now proven at industrial scale,” said Rondo CEO Eric Trusiewicz.
“We’re already developing and operating heat batteries across four continents and five industries. Our customers are improving their competitiveness and slashing their carbon emissions at the same time.”
The system operates directly alongside gas-fired boilers and feeds steam through the same infrastructure without requiring any modifications. By using locally produced solar energy to replace natural gas, Holmes Western Oil can reduce exposure to volatile energy markets and regulatory carbon costs.
How it works: Just bricks and wires
Industrial heat production is one of the biggest contributors to global energy consumption, accounting for roughly 25 percent of total use. From cement kilns to chemical plants, these processes rely on steady, high-temperature heat that has traditionally come from fossil fuels. The firm’s approach offers a cleaner alternative with a simpler design.
Unlike heat pumps or electric boilers that require constant electricity, the new system only needs to be charged for about six hours each day using the cheapest available electricity, such as from off-grid solar or low-cost grid power. Once charged, it can supply heat continuously.
“Just as electric vehicles opened up transport to renewable power, heat batteries will open up the industrial heat market,” stated Andy Lubershane, partner at Energy Impact Partners. “It’s another global inflection point for solar and wind.”
Rondo’s heat battery relies on ordinary materials—bricks and wires—to store energy. This design eliminates the need for rare minerals, avoids fire risks, and prevents toxic leaks.
It can deliver steam at pressures above 100 bar (1,450 psi) and can be installed beside existing industrial equipment, simplifying the transition to renewable power.
A new path toward clean industry
Rondo Energy, backed by Breakthrough Energy Ventures, the clean-tech fund established by Bill Gates, and Energy Impact Partners, a utility-backed investor group, is expanding its technology globally.
The company has ongoing projects in North America, Europe, Asia, and Australia.
The firm says its heat battery design can scale quickly because it uses widely available industrial materials rather than specialized components.
That scalability is key for industries looking to cut emissions while maintaining reliability and output.