Asger Risom
Heavy industry runs on massive volumes of natural gas-fired steam that cannot be economically replaced by lithium-ion batteries. By using cheap off-peak wind and solar power to superheat stacks of refractory firebricks up to 1,000°C, thermal batteries can store surplus clean energy as raw heat and deliver round-the-clock industrial steam directly through a factory’s existing pipe infrastructure.
When we picture the green energy transition, we tend to imagine sprawling fields of solar panels, offshore wind turbines, and massive warehouses lined with lithium-ion battery racks. We think in terms of electrical current.
Walk inside a commercial paper mill, a cardboard factory, or an industrial food processing plant, and you quickly realize electricity is beside the point. What actually runs heavy industry is steam. Vast, uninterrupted torrents of scalding, high-pressure steam, generated around the clock by roaring natural gas boilers.
If that steam cuts out for even a few minutes, molten liquids solidify in the pipes, packaging lines jam, and millions of dollars of raw material ruin in an instant. This thermal demand makes up roughly a quarter of all global energy consumption, and it is the single dirtiest reason our supply chains remain married to fossil fuels.
Plugging those factories into chemical batteries is an economic dead end. A lithium-ion battery system large enough to boil industrial water for three days straight would cost more than the factory itself.
To solve the problem, clean energy engineers decided to stop overcomplicating things. Instead of building futuristic battery chemistry, they are filling insulated steel containers with thousands of tons of ordinary dirt-cheap bricks, heating them until they glow white-hot, and tapping that heat on demand.
The absurdity of boiling water with chemical batteries
The hurdle with decarbonizing factory heat is that heavy industry needs continuous, high-temperature thermal energy at rock-bottom prices.
Solar and wind power are now the cheapest forms of electricity on Earth, but they are intermittent. The sun goes down, the wind dies down, and a factory floor cannot afford to take a nap. If you try to store that clean electricity in lithium-ion packs and discharge it through an electric boiler, the economics fall apart. Lithium cells degrade every time they cycle, require heavily mined minerals like nickel and cobalt, and store electricity as chemical potential rather than heat.
Converting renewable electricity into chemical energy, storing it, turning it back into electricity, and then running that current through a heating coil wastes energy and capital at every step of the chain.
The simpler answer is to eliminate the middleman: take cheap clean power, turn it straight into heat the second it is generated, and trap that heat inside an object that refuses to melt.
Modernizing a nineteenth-century blast furnace trick
The secret to a thermal brick battery is a material steelmakers have relied on since the Industrial Revolution: refractory firebrick.
Refractory bricks are dense, ceramic-like blocks made from everyday minerals such as alumina, silica, and magnesium oxide. They were originally engineered to line the inside of blast furnaces and molten iron crucibles because they can sit in blistering temperatures without cracking, melting, or chemically breaking down. They are essentially artificial volcanic stones designed to soak up heat and hold it.
Companies like Rondo Energy took that century-old metallurgy technology and mechanized it into a modular battery.
The concept works like an oversized toaster. When the regional grid has an excess of cheap solar at noon or surplus wind at 3 a.m., that low-cost electricity is routed through heavy-duty electrical resistance elements threaded between stacks of thousands of tons of refractory bricks. Over a few hours, the elements superheat the brick core to temperatures north of 1,000°C (over 1,800°F).
Once the bricks reach temperature, they glow vivid yellow-orange inside an airtight, heavily insulated steel shell. Because the container is engineered to eliminate thermal bridging, the outer skin stays safe to touch while the core holds thousands of megawatt-hours of heat for days with less than 1 percent daily energy loss.
Plumbing into the existing factory floor
Storing heat is only half the battle; the real engineering feat is getting that energy back out as predictable, steady industrial steam.
The brick stacks are manufactured with continuous vertical and horizontal airways running through the lattice. When a production line calls for steam, an automated intake pulls in ambient air and forces it through the channels in the glowing brick core. The air heats up to furnace temperatures in seconds.
That superheated air is then blown across water pipes in an adjacent heat exchanger, flash-boiling the water into pressurized steam. By adjusting a simple set of air dampers, the system can dial in the exact temperature and pressure the factory needs—whether that is gentle 150°C steam for baking bread or 500°C heat for curing chemicals.
Because there are no delicate chemical reactions or expanding anodes, thermal bricks do not suffer from capacity degradation. While a lithium battery pack starts fading after five to seven years of continuous daily cycling, a stack of refractory bricks can cycle from cold to white-hot every single day for forty years without losing performance. Better yet, round-trip efficiency for delivering heat sits at over 90 percent.
The drop-in path away from the boiler room
The primary reason factory owners are actually signing contracts for these units is that they do not require retrofitting the entire assembly line.
Plant managers do not have to throw away their existing manufacturing equipment or spend hundreds of millions redesigning their production floors. The thermal battery sits outside in the parking lot or rail yard, plugged into an electrical connection on one side and the factory’s existing steam manifold on the other. When gas prices spike, or when carbon tariffs kick in, the factory opens the valve to the brick battery and throttles down the fossil burner.
We spent two decades convinced that fixing industrial emissions would require a technological miracle—like building a global hydrogen pipeline network or building small modular nuclear reactors on factory campuses. It turns out the fastest way to wean heavy industry off fossil gas might just be a very hot pile of bricks.
