The archive · Climate & Energy · Strategic decision · 2020–2024
Rondo bets brick heat batteries replace gas boilers; first unit live since 2023
Rondo's brick heat batteries went commercial at Calgren in March 2023; Diageo, Eastman and a €75M Catalyst/EIB deal followed in 2024.
Rondo Energy
What the business is
Rondo Energy sells zero-carbon industrial heat: electric toaster-style elements heat refractory bricks past 1,000°C, and the stored heat becomes steam for ethanol plants, distilleries, chemical plants and cement kilns.
Starting capital：About $85M raised by October 2024 per MIT Technology Review, including a $60M Series B backed by Breakthrough Energy Ventures and Energy Impact Partners; strategic investors include Rio Tinto, SABIC, SDCL and Siam Cement Group.
How it started
Rondo Energy was founded in 2020 in the San Francisco Bay Area by John O'Donnell and Pete von Behrens, veterans of concentrating solar thermal, to decarbonize industrial heat, a source of roughly a third of global emissions. Instead of hydrogen or exotic materials, they bet on refractory bricks, a material steelmakers have used for a century, heated by toaster-style iron wires. In March 2023 the first commercial unit, a 2MWh Rondo Heat Battery, began supplying steam at Calgren Renewable Fuels' ethanol plant in Pixley, California, storing heat above 1,000°C and delivering it on a heat-as-a-service basis.
What happened
In 2024 Rondo announced projects at six industrial sites across the US and Europe: Diageo distilleries in Illinois and Kentucky, Eastman's Texas plastics-recycling plant, Covestro's German chemical plant, Denmark's GreenLab park and an undisclosed food-and-beverage facility. In June 2024 Breakthrough Energy Catalyst and the European Investment Bank committed €75M in project finance — a Catalyst grant plus EIB loan — for three of those first-of-a-kind installations, aimed squarely at the commercial valley of death between pilots and bankable scale. Canary Media reported EDP agreed to finance up to 2 GWh of heat batteries paired with up to 400 MW of wind and solar, and Siam Cement Group began building a cement-production pilot in Thailand.
How it ended up
Still running and scaling: MIT Technology Review reported in October 2024 that Rondo was producing brick for 2.4 GWh of storage a year with Siam Cement and planning 90 GWh a year, with food, beverage and chemical customers expected to start using commercial units between 2025 and 2027.
Background
Rondo Energy's bet is that factories will replace gas boilers with brick heat batteries — stacks of refractory bricks heated by electric toaster-style elements to over 1,000°C and discharged as steam — charged by cheap, intermittent renewable power. Founded in 2020 by John O'Donnell and Pete von Behrens, the startup chose century-proven refractory brick over engineered materials precisely so the technology could scale on today's supply chains.
The first commercial unit, a 2MWh Rondo Heat Battery at Calgren Renewable Fuels' ethanol plant in Pixley, California, entered service in March 2023, storing heat above 1,000°C and selling steam below the cost of gas-fired heat on a heat-as-a-service basis. In 2024 the company won projects at six industrial sites in the US and Europe — Diageo distilleries, an Eastman recycling plant, Covestro's chemical works, Denmark's GreenLab and a food-and-beverage plant — and Breakthrough Energy Catalyst plus the European Investment Bank committed €75M in grant-and-loan project finance for three of them.
The deal was explicitly designed to cross the commercial valley of death: infrastructure investors wouldn't underwrite first-of-a-kind plants, so a grant plus loan package paid for the proof. By October 2024 MIT Technology Review counted about $85M invested, named Rondo a 2024 Climate Tech Company to Watch, and reported plans to grow brick production from 2.4 GWh to 90 GWh of storage per year as food, beverage and chemical customers begin using commercial units between 2025 and 2027.
What has to be true
- Using century-proven refractory brick meant the core material was already produced cheaply at industrial scale, unlike competitors' engineered materials.
- Selling heat-as-a-service shifted first-of-a-kind risk from the customer to Rondo, removing the adoption blocker for risk-averse factories.
- Packaging a Catalyst grant with an EIB loan attacked the real bottleneck — project finance — rather than waiting for the technology to get cheaper.
- Anchoring on ethanol, food and beverage first gave the startup reference installations with simple steam requirements before tackling cement and chemicals.
What can be applied
The first-of-a-kind gap is a financing problem, not a technology problem: heat-as-a-service plus grant/loan project finance crosses it, and one bankable project unlocks the next.
Aftermath
As of 2026-09-02 Rondo continues to operate from Alameda, California, selling heat-as-a-service to industrial customers. Its first commercial battery has run at Calgren since March 2023; Diageo, Eastman, Covestro, GreenLab and EDP-backed projects were announced or under construction as of mid-2024, and Siam Cement began building a cement pilot in Thailand. Public reporting does not disclose project status or financing beyond mid-2024, so the 2025–2026 deployment record is not verifiable from these sources.
Sources
- Rondo Energy Announces World's Highest Temperature Thermal Energy Storage
- Rondo Energy funding shows a new way across the climate startup 'valley of death'
- Rondo's heat batteries will soon be cleaning up factories in US, Europe
- 2024 Climate Tech Companies to Watch: Rondo Energy and its hot bricks
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