You won’t believe how this ’embarrassingly simple’ method tackles industrial emissions!

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Of all human discoveries, fire has been among the most extraordinarily useful, empowering producers from ancient blacksmiths to modern cement factories. But is it finally time for the industry to stop burning stuff?

A small crop of start-ups developing thermal batteries for industrial heating think so. If they’re right, they could soon start having an impact on one of the most important and least appreciated drivers of climate change. Read on. —Simon Mundy

The thermal battery sector starts to heat up

It transports an 18th-century English factory owner to a modern manufacturing facility and might be baffled by the profusion of robots and advanced electronics. But one aspect of today’s industrial economy would seem quite familiar.

From chemicals to cement to textiles, manufacturing often requires enormous amounts of heat. Since the Industrial Revolution, that heat has been supplied primarily by burning fossil fuels, and this is currently the case accounts for about 10% of global carbon dioxide emissions.

Given the huge contribution of industrial heat to the climate crisis, it has received surprisingly little attention. Even when these emissions are discussed, they are often glibly labeled “hard to abate,” perhaps implying the need for costly and unproven carbon capture systems.

For California start-up Rondo Energy, this looks like an opportunity for a lucrative disruption. Rondo today announced a $60 million funding injection to scale up its thermal battery technology, which converts electricity into industrial-grade heat that can be used immediately or stored until needed.

Investors include a few large industrial carbon emitters: Rio Tinto, which spews large volumes of carbon dioxide from its aluminum smelters; giant oil producer and refiner Saudi Aramco and its chemical subsidiary Sabic; and cement companies Titan and Siam Cement Group.

If Rondo’s CEO John O’Donnell is to be believed, these companies could wipe out the majority of their operating carbon emissions by implementing his “almost embarrassingly simple” technology.

Rondo’s approach combines two basic technical approaches, neither of which is obviously revolutionary. The former is very similar to a gigantic toaster oven, with electricity conducted through a metal wire, which is heated by electrical resistance. That heat then radiates into a complex array of bricks, a version of a system developed for use in conjunction with blast furnaces about two centuries ago. The bricks are heated to approximately 1,500°C and retain this heat energy for days, with daily loss rates of just 1%.

The integrated system is intended to offer factories a constant supply of carbon-free industrial heat from renewable energy that continues to flow after the sun goes down or the wind stops blowing.

“One of the biggest compliments we get sometimes is, ‘this is kind of boring,’” O’Donnell told me. “And, you know, boring isn’t bad when you want to build infrastructure quickly.”

For all its limited sex appeal, the system as a whole has proven difficult to fix. O’Donnell says the Rondo had to go through 74 iterations, largely tinkering with the brick array layout, to find a design that could deliver reliable performance. (One risk with this approach is that too much heat can build up in one part of the brick structure, causing it to crack.)

And the company has yet to demonstrate the system on a large scale. Rondo ran a pilot project at a biofuel plant in California, with a miniature version of his system providing 2 MW of heat. It is now building its first commercial plant, a 130MW unit due to go online next year, O’Donnell said, declining to share further details including the name of the industrial client.

Rondo isn’t the only runner in the thermal battery race. Connect a California start-up Antora developed a process that uses electricity to heat blocks of solid carbon to industrial temperatures. of Norway EnergyNest has partnered with fertilizer maker Yara and adhesive maker Avery Dennison for its thermal battery system, which uses parabolic mirrors to heat liquids with reflected sunlight.

Breakthrough Energy Ventures, founded by Bill Gates and backed by several fellow billionaires, has added to its stake in Rondo’s new funding round and has also invested in Antora. Carmichael Roberts, who co-heads Breakthrough’s investment committee, told me he hopes to galvanize finance in the industrial heat space, which has seen limited interest among investors despite its huge role in the climate challenge.

Thermal battery manufacturers are not yet able to cover the landscape in this field. The maximum temperatures their systems can deliver – currently around 1,500°C – are insufficient for some industrial processes, including metal production. They are also not suitable – at least not yet – for processes that require very precise temperatures, such as oxy-acetylene welding, the think-tank Energy Innovation noted in a recent report. But these account for only a small fraction of industrial heat, he added, estimating that thermal batteries could in theory replace about 75 percent of US industrial energy use of fossil fuels.

And the application of thermal batteries should not be limited to industrial heating. One of the most pressing concerns in the energy transition is how to manage the intermittency of solar and wind energy, balancing peaks and troughs in generation.

By converting grid electricity into heat during periods of peak generation and converting it back during periods of high demand, thermal batteries could prove to be a powerful grid-level storage system. They offer much better energy conversion efficiency than hydrogen fuel cells and have much cheaper (and more abundant) inputs than large-scale lithium-ion batteries, O’Donnell pointed out. “Brick is basically made of dirt,” she said. “Dirt is available on a large scale.”

This relatively low supply chain risk has been an attraction for Microsoft, another investor in Rondo’s latest round, said Brandon Middaugh, senior director of the tech giant’s Climate Innovation Fund.

But the scale of the larger task for Rondo and its competitors remains enormous. O’Donnell estimates that approximately 9,000 GW of renewable electricity would be needed to decarbonise all industrial heat with thermal batteries. At the end of 2022, the world’s total renewable generation capacity – for all purposes – was 3,372 GW. “This is not the fruit of low-impact decarbonization,” Middaugh told me. (Simon Mundy)

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