Heavy industry is known to be one of the hardest sectors of the economy to decarbonize. Production of materials like steel and cement requires a lot of continuous heat and cannot be met by the variability of renewable power, which is playing an increasingly larger role on the nation’s power grid.  Enter Rondo Energy, a company taking a novel approach to this challenge by using low-cost wind and solar electricity to generate and store industrial heat.

C3 Solutions’ President Drew Bond recently sat down with John O’Donnell, Rondo’s CEO, to talk about the company’s unique thermal energy storage technology on C3’s Tech Voices interview series.

Rondo draws its name from the musical theme where pieces of a score repeat to pay homage to the company’s team, which has worked together in various sectors and startups in the past. Its solution, as O’Donnell explains, is “storing intermittent electricity by heating material and delivering continuous energy.” By converting excess renewable electricity into high-temperature thermal energy that can be stored, Rondo provides a way to capture and utilize power that would otherwise be curtailed or wasted.

The company’s secret? Clay bricks. 

At the core of Rondo’s technology is a modern take on the centuries-old concept of the Cowper stove used in iron production. These large brick structures absorbed excess heat from furnaces and released it later to preheat incoming air. Rondo has adapted this idea, using renewable energy and specialized electric heaters to heat up large brick thermal storage units. 

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The stored thermal energy can then be used to replace fossil fuels in industrial processes like cement production, refineries, pulp and paper mills, and food manufacturing – sectors that O’Donnell says collectively account for about 25% of global fuel consumption. The company primarily sells its storage solution via an electric boiler or by directly inserting the thermal heat into kilns. When hot, each of these bricks can store more energy than a Tesla Model X. 

One of Rondo’s key advantages is the ability to integrate seamlessly into existing industrial facilities without major modifications. As O’Donnell points out, “We drop in, connecting to that steam network somewhere alongside all of that infrastructure. You’ll just turn down those boilers, you’ll burn less fuel.”

The company’s innovative solution has garnered attention from several major investors including Bill Gates-back Breakthrough Energy Ventures and Rio Tinto—one of the world’s largest mining companies.

For the past year, Rondo has been working with Cargen Renewable Fuels to create low-carbon ethanol for sustainable aviation fuel at Cargen’s facility in Pixley, California. The partnership has yielded impressive results, allowing Cargen to lower production costs, reduce local air pollution, and cut the CO2 footprint of its ethanol by 50%. 

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Recently, the Department of Energy awarded up to $75 million to Rondo through the agency’s recent funding round for industrial decarbonization. Together with Diageo Americas Supply—a prominent spirit and drink producer—Rondo will deploy its brick boilers at two of Diago’s facilities in Shelbyville, Kentucky and Plainfield, Illinois. The project is expected to reduce CO2 emissions from Diageo’s production process by as much as 17,000 metric tons annually.

Rondo is also going global, deploying 90 gigawatt-hours worth of its batteries at Siam Cement Group’s facility in Thailand. Once this project is completed, the facility will be the largest battery factory in the world. 

With its simple yet innovative solution, Rondo’s thermal storage technology could be a potential disruptor in the race to cost-effectively decarbonize industrial operations.

The views and opinions expressed are those of the author’s and do not necessarily reflect the official policy or position of C3.