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Of all human discoveries, fire has been among the most awesomely useful — empowering manufacturers from ancient blacksmiths to modern cement plants. But has the time finally come for industry to stop burning stuff?
A small crop of start-ups, developing thermal batteries for industrial heat, think so. If they’re right, they could soon start making an impact on one of the biggest — and least well appreciated — drivers of climate change. Read on. — Simon Mundy
Thermal battery sector starts to heat up
Transport an 18th-century English factory owner into a modern manufacturing plant, and he might be bewildered by the profusion of robots and advanced electronics. But one aspect of today’s industrial economy would feel rather more familiar.
From chemicals to cement to textiles, manufacturing often requires huge amounts of heat. Since the industrial revolution, that heat has been provided mainly by burning fossil fuels — and this currently accounts for about 10 per cent of global carbon dioxide emissions.
Given the huge contribution of industrial heat to the climate crisis, it’s received strikingly little attention. Even when these emissions are discussed, they’re often airily labelled “hard to abate” — perhaps implying a need for expensive, unproven carbon-capture systems.
For Californian start-up Rondo Energy, this looks like an opportunity for lucrative disruption. Rondo today announced a $60mn funding injection to scale up its thermal battery technology, which converts electricity into industrial-grade heat that can be used immediately or stored until it is needed.
Among the investors are some hefty industrial carbon emitters: Rio Tinto, which belches large volumes of carbon dioxide from its aluminium smelters; the giant oil producer and refiner Saudi Aramco and its chemicals affiliate Sabic; and cement companies Titan and Siam Cement Group.
If Rondo chief executive John O’Donnell is to be believed, these companies could wipe out the vast bulk of their operational carbon emissions by deploying his “almost embarrassingly simple” technology.
Rondo’s approach combines two basic technical approaches, neither of them obviously revolutionary. The first is much like a giant toaster, with electricity conducted through a metal wire, which heats up thanks to electrical resistance. That heat then radiates into a complex array of bricks, a version of a system developed for use alongside blast furnaces about two centuries ago. The bricks are heated to about 1,500°C — and conserve this heat energy for days, with daily loss rates of just 1 per cent.
The integrated system is intended to offer factories a steady supply of carbon-free industrial heat from renewable energy that keeps flowing after the sun goes down or the wind stops blowing.
“One of the greatest compliments we get sometimes is, ‘this is kind of boring,’” O’Donnell told me. “And, you know, boring is not bad when you want to go build infrastructure rapidly.”
For all its limited sex appeal, the system as a whole has proved hard to get right. O’Donnell says Rondo had to go through 74 iterations, largely tinkering with the layout of the brick array, 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 still has to prove the system at scale. Rondo has been operating a pilot project at a biofuels plant in California, with a miniature version of its system providing 2MW of heat. It’s now building its first commercial plant, a 130MW unit that will come online next year, said O’Donnell, declining to share further details including the name of the industrial client.
Rondo is not the only runner in the thermal battery race. Fellow California start-up Antora has developed a process using electricity to heat blocks of solid carbon to industrial temperatures. Norway’s EnergyNest has secured partnerships with fertiliser maker Yara and adhesive producer 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, added to its stake in Rondo’s new funding round, and has also invested in Antora. Carmichael Roberts, who co-leads Breakthrough’s investment committee, told me it is hoping to galvanise funding in the industrial heat space, which has seen limited interest among investors despite its massive role in the climate challenge.
The thermal battery makers are not yet in a position to cover the landscape in this field. The maximum temperatures that their systems can deliver — currently about 1,500°C — are insufficient for some industrial processes, including in metal production. They are also not suitable — at least not yet — for processes requiring very precise temperatures, such as oxyacetylene welding, noted the think-tank Energy Innovation in a recent report. But these represent only a small portion of industrial heat, it added, estimating that thermal batteries could in theory displace about 75 per cent of fossil fuel usage for US industrial energy.
And the application of thermal batteries need not be limited to industrial heat. One of the most pressing concerns in the energy transition is how to handle the intermittency of solar and wind energy, balancing out peaks and troughs in generation.
By converting grid electricity to heat at peak generation times, and converting it back at times of high demand, thermal batteries could prove 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 from dirt,” he said. “Dirt is available at scale.”
This relatively low supply chain risk was an attraction for Microsoft, another investor in Rondo’s latest round, said Brandon Middaugh, senior director of the technology giant’s Climate Innovation Fund.
But the scale of the wider task for Rondo and its competitors remains enormous. O’Donnell estimates that about 9,000GW of renewable electricity would be needed to decarbonise all industrial heat with thermal batteries. As of the end of 2022, total worldwide renewable generation capacity — for all purposes — stood at 3,372GW. “This is not the low-hanging fruit of decarbonisation,” Middaugh told me. (Simon Mundy)
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