Rondo Energy is building a battery business around an industrial material that predates the electricity grid: refractory brick. Its heat batteries buy electricity when it is available and economical, store it as high-temperature heat, and supply steam or hot air when a factory needs it. The California-based company now has operating references in the United States and Thailand, a chemical-industry installation under construction in Germany, and a larger Australian refinery project entering engineering. That progression makes Rondo worth watching for a reason beyond decarbonization: it is testing whether flexible electricity consumption can become a dependable industrial utility service. AI-generated editorial illustration of brick-based thermal storage, not a photograph or engineering rendering of a Rondo facility. Rondo at a glance Product: Rondo Heat Battery, an electric thermal energy storage system. Leadership: CEO Eric Trusiewicz; founders John O’Donnell, chief innovation officer, and Pete von Behrens, chief technology officer. Operating reference: 100 MWh thermal storage installation in California, announced commercially operational in October 2025. Latest milestone: front-end engineering and design for a proposed 360 MWh thermal / 30 MW discharge project at Rio Tinto’s Yarwun refinery, announced October 21, 2026. Project ratings and performance claims below come from the cited announcements. Proposed capacity is not operating capacity; thermal megawatt-hours are not interchangeable with electrical megawatt-hours. A company built around the steam bill Most battery businesses sell a way to move electricity through time. Rondo starts with the customer’s final requirement instead. A chemical plant, fuel producer, or food processor often needs steam rather than electricity. Converting cheap power into heat, storing that heat, and delivering it directly avoids the need to turn all the stored energy back into electricity. That distinction defines its commercial identity. Rondo is not primarily an electric-vehicle cell supplier or a conventional grid battery integrator. It is an industrial energy equipment and services company. Its competition includes fossil-fueled boilers, electric boilers, other thermal storage systems, and, for suitable lower-temperature applications, heat pumps. The relevant purchase decision is the cost and reliability of useful heat at the factory boundary. The company’s current leadership page lists Eric Trusiewicz as CEO and identifies John O’Donnell and Pete von Behrens as founders. That leadership structure places technology development alongside the task of delivering industrial projects. Public announcements establish California as the company’s base, with teams serving several international markets. For a private supplier, operating references carry more weight than a large addressable-market claim. Customers need confidence that a new heating asset will fit into a production process, meet agreed steam conditions, and receive support over a long service life. Rondo’s central challenge is to turn a persuasive thermal-storage principle into that kind of repeatable supplier relationship. How the brick battery works Rondo’s technical overview describes resistance heating elements converting electricity into heat. Thermal radiation heats refractory bricks, which hold the energy inside an insulated enclosure. When heat is needed, air passes through the brick stack and transfers that energy to the customer’s process, either as hot air or through steam production. The company describes brick temperatures up to 1,500°C and heat losses below 1% per day. Those are supplier specifications, not independent field measurements supplied for this profile. Actual delivered temperature, usable capacity, standby loss, charging power, and duty cycle depend on the installation and its operating conditions. The attractive part is the use of established industrial materials rather than a new electrochemical cell chemistry. Refractory materials and resistance heating already have industrial supply chains. Rondo’s engineering value lies in how those components are arranged, controlled, insulated, and integrated with the steam system. A familiar material does not make the complete plant trivial, but it changes the manufacturing and raw-material risks. A battery that charges for only a few hours needs enough charging power to cover the entire day’s energy demand, including losses. That makes the electrical connection important. A factory may have an excellent thermal application yet still face expensive network upgrades, electricity tariffs, or a long wait for the required connection. The storage enclosure is only one part of the installed project. Rondo also describes combined heat and power configurations using steam turbines. These require careful comparison with direct heat delivery. A high electricity-to-heat efficiency does not imply an equally high electricity-to-electricity round-trip efficiency: producing electricity from stored heat adds a conversion stage with its own losses. Buyers should ask for the efficiency and useful output of their specific configuration. What the operating projects establish In its October 16, 2025 announcement , Rondo said a 100 MWh heat battery in California had entered daily automatic commercial operation. The installation charges from an on-site, off-grid photovoltaic array and supplies continuous high-pressure heat and steam to a fuel production facility. The customer was not named in that release. Rondo reported that the project had met operating milestones after ten weeks and cited round-trip efficiency above 97%. This is meaningful as a supplier-reported electricity-to-heat result, but it should not be treated as a claim about electrical storage efficiency. Nor does ten weeks of operation establish decades of equipment life. Long-term availability, maintenance costs, and customer economics remain the more demanding evidence. The California example matters because it connects a variable renewable resource with a continuous industrial load. It also operates alongside gas-fired boilers rather than requiring the customer to redesign the whole facility. That kind of partial substitution can reduce the consequences of an early outage and give a customer a measured path toward expansion. A second operating reference tests a different configuration. In a November 2025 announcement with SCG Cleanergy , Rondo described a 33 MWh unit at an SCG cement plant in Saraburi, Thailand. The companies said it was delivering 2.3 MW of continuous thermal output as steam, charging from the grid and a nearby floating solar farm. The Thai installation supplies superheated steam to a turbine integrated with the plant’s heat-recovery system. Its stated 2.3 MW thermal output must not be reported as 2.3 MW of electricity. The project is useful evidence of integration with an existing industrial power system, while the release does not provide a complete electrical round-trip efficiency or a public project cost breakdown. SCG and Rondo also said the unit was built in Thailand with extensive local sourcing. That is strategically important: a design that can use regional industrial suppliers may scale differently from one tied to a single specialized cell factory. The remaining test is whether localization preserves quality, delivery schedules, and guarantees as deployment spreads. Germany and Australia are different stages, not delivered backlog At Covestro’s Brunsbüttel chemical site, Rondo is moving into a demanding European steam application. The January 19, 2026 groundbreaking announcement describes a 100 MWh installation intended to supply roughly 10% of the site’s steam and save up to 13,000 tonnes of carbon dioxide annually. Commissioning was planned for the end of 2026. Those emissions savings and steam shares are project expectations, not operating results. The announcement says Breakthrough Energy Catalyst and the European