In a first, cement giant to tap thermal batteries for cleaner heat

Making the cement that holds together our buildings and streets is a highly carbon-intensive process — one that involves burning lots of fossil fuels to blast materials with searing heat. But startups are developing technologies that could use clean electricity to produce cement instead, and a Boston-based firm is about to put its system to the test.

Electrified Thermal Solutions said on Tuesday that it will deploy two of its heat batteries at a facility run by global cement giant Holcim. The units will provide heat to a high-temperature chamber inside the plant, marking the first time a thermal-energy storage system has been used in such a way, said Daniel Stack, Electrified Thermal’s CEO and co-founder.

If the project goes as planned, it will be ​“a step change in what’s been done to actually electrify cement and concrete production,” Stack said.

The companies didn’t say which of Holcim’s many global facilities will house the heat batteries, which are set to come online early next year. Stack also declined to say how much the project would cost to develop, though he said the heat batteries have a ​“very compelling cost profile” when operating in the European markets and in areas where electricity costs less than natural gas.

Electrified Thermal’s announcement comes nearly nine months after the MIT spin-out unveiled its first commercial-scale thermal battery at the Southwest Research Institute in San Antonio. The system has logged more than 1,000 hours of operation, providing the proof points needed to move ahead with the Holcim project. 

Cement is responsible for about 8% of all global carbon dioxide emissions. About 60% of that planet-warming pollution comes from the chemical reactions of the raw materials that go into cement kilns — namely, limestone, which breaks down into its constituent parts of calcium oxide and carbon dioxide when baked.

The industry’s remaining emissions result from burning natural gas or coal to heat kilns and other furnaces. That’s where Electrified Thermal’s technology will come into play for Holcim.

The startup’s battery runs electricity through insulated stacks of metal-oxide firebricks, which heats them up. The system taps the grid during the cheaper off-peak hours — when wind, solar, and other carbon-free sources are often most abundant. The company can discharge that stored-up heat by flowing air over the firebricks, then piping the resulting hot gas directly into the industrial equipment.

In San Antonio, Electrified Thermal’s battery can store 20 megawatt-hours of heat at temperatures of up to 1,800 degrees Celsius (3,270 degrees Fahrenheit). At the Holcim plant, the units will have the same capabilities for providing heat during the calcination process, which typically requires temperatures of between 900℃ and 1,500℃, Stack said.

“Electrifying high-temperature industrial heat is one of the advanced technologies we are incorporating in our decarbonization strategy, and this deployment allows us to evaluate its potential,” Ram Muthu, Holcim’s head of operational excellence, said in a statement.

Holcim, which is one of Electrified Thermal’s investors, is also backing a handful of other clean-cement startups, including Sublime Systems, another MIT spin-out. Sublime is working to replace cement kilns altogether through an electrochemical process that avoids the need for scorching heat.

When it comes to thermal storage, Electrified Thermal is among around two dozen startups developing systems that can supply clean industrial heat, or store and discharge electricity back to the grid. California-based Antora Energy raised a whopping $550 million in July to build and deploy more of its toaster-like heat batteries. Six other firms raised at least $53.7 million combined in venture capital and equity funding so far this year, according to the consultancy Cleantech Group.

The heat-battery developer Rondo Energy is also working to decarbonize cement production. Last November, the California-based company began operating a 33-megawatt-hour unit at a cement plant in Thailand that charges up from the grid and a nearby floating solar farm. Rather than directly supplying heat, the system produces superhot steam to drive a turbine, which then generates electricity.

Zainab Gilani, an energy and power research associate at Cleantech Group, said that many criteria can determine how well a thermal-energy storage project will fare in a given market, including natural gas prices, local decarbonization policies, the availability of renewable energy, and electricity costs.

“These factors, in addition to the specific demand for power and heat by industrial customers, all contribute to how successful projects will be,” Gilani said.

Electrified Thermal said the project with Holcim marks its third industrial partnership. The startup is teaming up with another one of its investors, ArcelorMittal, to test the heat battery at the steelmaker’s R&D facility in Spain. Stack didn’t name his firm’s third partner, though Electrified Thermal is also backed by the Brazilian iron-ore producer Vale.

“We see the road map for how we can electrify every portion of the cement industry,” Stack said. ​“We’re looking forward to walking that path with Holcim and with our partners in the other major industrial verticals that have so far been unachievable with electric heat.”