Jul 16, 2023

Next Big Thing In Long Duration Energy Storage: Hot Bricks

Hot bricks are calling, and investors are responding to the allure of low cost, long duration energy storage.



Hot bricks have been catching the eye of some of the world’s top clean tech investors, attracted by the potential for low cost, long duration energy storage systems. That sounds simple enough. Warmed-up bricks or blocks have been used for centuries to store energy. The challenge of today is getting them to hold enough heat to decarbonize industrial processes, which can require superhot temperatures. That has proved to be a little tricky, but several of these block-type thermal systems are finally moving towards the commercial market.

The US startup Rondo Energy grabbed the media spotlight last week, when it announced a $60 million round of funding for its “Rondo Heat Battery” technology from A-list investors and industrial stakeholders, including Rio Tinto, the Climate Innovation Fund of Microsoft, Aramco Ventures, SABIC, SCG, TITAN, Breakthrough Energy Ventures, Energy Impact Partners, SDCL SEEIT, and John Doerr.

Wait, John who? John Doerr is a US investor and chairman of the venture capital firm Kleiner Perkins. Doerr is best known for his early interest in Google and Amazon, among others. More recently, in February his affiliated firm Foris Ventures placed a $10 million bet on the turnkey solar installation company Complete Solaria.

Among the other investors, one familiar name is Breakthrough Energy Ventures. The Ventures group spun out of the Breakthrough Energy Coalition, which was shepherded into being under the wings of Bill Gates to coincide with the 2015 Paris Agreement on climate change.

Breakthrough Ventures launched in December 2016, with a high powered list of board members and investors, including Jeff Bezos, Michael Bloomberg, Richard Branson, and Vinod Khosla, among others.

Rondo’s thermal energy storage system is based on bricks infused with iron wire. The system deploys wind or solar power to run electric elements, like those in your toaster oven, to heat the bricks up to 1,500 degrees centigrade. The heat is transferred by superheated air, which can be used as-is for industrial processes or deployed to generate steam.

The company started up its first commercial operation earlier this year at a biofuel production facility in the US. The next step is a partnership with its investor SCG (the Siam Cement Group) to manufacture the specialized bricks at scale.

Aramco Ventures is not the only fossil-related energy investor to dabble in new block-based thermal energy storage technologies. In February, Shell’s GameChanger branch put up $400,000 to help accelerate the implementation of a demonstration facility for the Australian startup MGA Thermal Energy in Newcastle.

MGA has also caught the eye of the Australian Renewable Energy Agency, which has also provided funding for the project. Last year, AREA chipped in a little over $800,000.

Money comes to money. On August 3 MGA noted that its existing investors Main Sequence, Varley Holdings, Melt Ventures, and the Climate Venture Capital Fund of New Zealand have signed on to another round. The new round also attracted two new investors, Pollination Group and Understorey, for a total of almost $5.3 million. The dollars will go to complete the demonstration project and expand the MGA team.

“With the imminent completion of our production line, we’re on track to produce 1,000 blocks per day which can then be assembled into 24/7 renewable energy storage,” explained Erich Kisi, the company’s CEO.

The MGA blocks themselves consist of metal alloy particles dispersed through a matrix of graphite. When subjected to high heat from an electrical current, the alloy particles melt while the block retains its shape. CleanTechnica is reaching out to the company for more details on that alloy, but for now it appears to be a trade secret.

When assembled into an energy storage system, 3,700 blocks will take up a space about the size of a shipping container. MGA calculates that the unit can power more than 135 typical homes for 24 hours. In contrast, lithium-ion energy storage systems only last several hours.

“… TES systems are able to store millions of kilowatt hours of energy in a cheaper, safer and longer-lasting way compared to other dispatchable solutions,” MGA enthuses.

Kraftblock is another thermal energy storage company playing it close to the vest.

Kraftblock’s website doesn’t say much about the ingredients in its Kraftblocks, but it does state that recycled materials account for up to 85% of the storage material, and that no rare earths or environmental hazards are involved. The company told CleanTechnica know that steel slag is among the recycled materials. They also note that the blocks are “almost completely” recyclable.

With a lifespan of 15,000 cycles, the thermal system should last about 40 years under a once-a-day usage scenario. The system is containerized, stackable, scalable, and able to run on waste heat as well as electricity from renewable resources.

Kraftblock is already on the road to commercial use in Europe, where it caught the eye of PepsiCo and several utilities. On August 8, the company announced that it raised a total of €20 million in a Series B round from new investors and stakeholders including Shell Ventures and Finindus, which is backed by the leading steelmaker ArcelorMittal.

Note: The section on Kraftblock has been updated and corrected with information from the company.

The US startup Antora Energy launched in 2018 under the wings of the science and technology incubator Activate Energy. It has been on a roll ever since with an eye-catching thermal energy storage twist that deploys carbon blocks and a photovoltaic element at the output end of the system.

Activate notes that last year, Antora nailed down more than $50 million in new funding in a round co-led by Breakthrough Energy Ventures and Lowercarbon Capital. Also in the mix are Shell Ventures (again!), BHP Ventures, Grok Ventures, Trust Ventures, Overture VC, and Impact Science Ventures. The company’s existing investor Fifty Years VC also returned for that round.

That’s on top of a $7.9 million award provided by ARPA-E, the Energy Department’s cutting edge funding office, in 2019.

“To charge the battery, power from the grid will heat the blocks to temperatures exceeding 2000°C (3632°F) via resistive heating,,” ARPA-E explains. “To discharge energy, the hot blocks are exposed to thermophotovoltaics (TPV) panels that are similar to traditional solar panels but specifically designed to efficiently use the heat radiated by the blocks.”

“The team will develop a thermophotovoltaic heat engine capable of efficiently and durably converting high-temperature heat into electricity. It will seek to double panel efficiency through new materials and smart system design, potentially enabling a cost effective grid storage solution,” the office adds.

The ARPA-E funding timeline concludes next June. In the meantime, expectations are running high and the company is already taking steps to commercialization. As described by MIT News last week, Antora’s manufacturing facility in California will have an annual capacity of 2 megawatts and it is already working with several customers. They expect the first installation to be up and running as early as 2025.

And not a moment too soon. Republican office holders in the US have been doing their best to stem the tide of renewable energy investing, but the Earth is beginning to cook and the smart money is betting on survival.

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Image (screenshot): Thermal energy storage system courtesy of Rondo Energy.

Tina specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Views expressed are her own. Follow her on Twitter @TinaMCasey and Spoutible.

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