Thermal energy storage—TES for short—isn’t flashy. It doesn’t trend like AI, electric vehicles, or quantum computing. But in the background of the global energy transition, it’s becoming absolutely essential. That’s because while the world has made progress in decarbonizing electricity, it has barely scratched the surface of decarbonizing heat.
And the numbers are staggering: more than 20% of global greenhouse gas emissions come from industrial heat processes—most of which can’t be electrified with batteries or standard solar panels. They need dependable, high-temperature heat delivered when and where it’s needed. That’s where thermal energy storage comes in.
From food and beverage manufacturers to cement kilns, hydrogen electrolysis, and even AI data centers and cloud computing infrastructure, the ability to store energy as heat and dispatch it precisely when needed is no longer a luxury. It’s a prerequisite for deep decarbonization. And that’s why the biggest names in venture capital and institutional energy investment are pouring money into thermal storage companies like Rondo Energy and Antora Energy, whose private valuations now exceed hundreds of millions of dollars. They’re betting that TES isn’t just the next big thing—it’s the necessary one.
But for public market investors, the opportunity has always been frustratingly out of reach. Until recently, there were only two pure-play publicly traded ways to invest in TES: Heliogen Inc. (OTCQX: HLGN) and Brenmiller Energy Ltd. (NASDAQ: BNRG).
Now, there’s only one.
Heliogen’s Exit Exposes The Remaining Listed TES Pure Play
On May 29, 2025, Zeo Energy Corp. announced its acquisition of Heliogen in an all-stock deal valued at approximately $10 million. For a company that once captured headlines with AI-powered heliostat arrays and solar towers meant to generate hydrogen and industrial steam, it marked the end of a turbulent chapter. Heliogen had already spent most of 2024 winding down operations, cutting staff, and canceling projects, including the much-publicized Capella Project with Woodside Energy.
Although the company reported $23.2 million in 2024 revenue, much of that was due to accounting adjustments tied to project cancellations, rather than active deployments. Despite a reported net income of $78.9 million, the underlying reality was stark: Heliogen’s core business was no longer viable on its own. It was a high-concept story that didn’t materialize or scale in the real world as expected.
Zeo’s acquisition salvages the brand and some of the intellectual property. But it also removes Heliogen as a standalone TES investment from the public markets.
Brenmiller Energy Has Quietly Built What Others Hope To
And it leaves Brenmiller Energy as the last publicly traded pure-play thermal energy storage company, and perhaps more importantly, the only one that allows retail traders to compete for the same expected rewards as well-heeled institutional and high-net-worth investors.
Headquartered in Israel and listed on the NASDAQ, Brenmiller Energy took a different path from other TES players. It didn’t pursue hype-driven narratives or raise capital through a speculative special purpose acquisition company (SPAC). Instead, it built its technology the hard way—through mutually beneficial collaboration, industrial pilots, and engineering-first execution.
Brenmiller’s flagship product, the bGen™ system, converts renewable electricity or off-peak grid power into stored heat using crushed rocks—then releases that heat on demand 24/7/365 for industrial or district heating applications. It’s modular, scalable, containerized, and critical to the comparisons made— already in operation.
As of mid-2025, Brenmiller has active projects deployed or in development in Spain, the United States, Israel, Germany, and Hungary. These include industrial decarbonization systems at Tempo Beverage in Israel, Partner in Pet Food in Hungary, and the Wolfson Medical Center in partnership with ENEL.
In the U.S., a deployment with the New York Power Authority is already live, showcasing Brenmiller’s ability to serve public-sector infrastructure with flexible and dispatchable clean heat. In Spain, the company plays a key role in the SolWinHy Project, a hydrogen initiative backed by the European Hydrogen Bank. Brenmiller has been awarded £7 million in funding to support its thermal storage deployment as part of the project, further validating its technology and strategic importance in Europe’s push for industrial decarbonization.
In other words, Brenmiller Energy isn’t a company pitching what’s possible. It’s a company delivering what’s needed.
Clean Industrial Heat Is Here and Priced In Hundreds of Millions
Ironically, despite having high seven-figure sovereign-funded commitments, global partners, and a revenue-generating product in the market, Brenmiller trades at just $5.45 million in market capitalization before this morning’s market open. That’s less than a single private funding round for companies like Rondo or Antora—both of which are still navigating the myriad early-stage deployments.
To be clear, those companies are impressive. Rondo’s brick-based heat battery and Antora’s carbon block storage paired with thermophotovoltaics are both promising technologies with long-term potential. But they are, as noted, inaccessible to the vast majority of retail investors. Unless you’re writing institutional or personal checks in the tens of millions, you’re not getting into those deals.
That’s what makes Brenmiller Energy’s public listing so unique—and so mispriced.
While investors crowd into concept-stage battery storage companies with billion-dollar dreams and minimal revenue, Brenmiller Energy already has the technology, partnerships, and government support to justify a significantly higher valuation. Yet it remains under the radar, likely due to its lean capital structure, non-U.S. origin, and the broader market’s lagging awareness of TES as a category.
But for those who do see it, the setup is rare: a first-mover, revenue-generating clean energy company operating in a validated sector with massive addressable demand—and trading at a tiny fraction of its tangible project pipeline value, which the company estimates to be $500 million today.
The BNRG Valuation Gap Is Stunningly Flagrant
Importantly, Heliogen’s sale shouldn’t be seen as a failure of TES—it should be seen as a market signal. Don’t misinterpret the message—Heliogen entered the market to achieve great things, and their intention to contribute to a rapidly changing energy market is commendable. The problem they faced is that the era of overcapitalized, over-engineered concepts is coming to an end. Investors are seeking companies that can deploy now, scale realistically, and meet the industrial heat demands that ESG mandates.
Brenmiller Energy fits that mold. And now, it’s the only public company we know of that does. Why is that important to the retail investor?
Because governments are pushing harder for carbon reductions, and industrial clients are seeking alternatives to gas boilers and fossil-fueled heat. That combination should create demand for what Brenmiller Energy already offers, not hopes to. In other words, with capital flowing, Brenmiller Energy is in the right place with the right product at the right time. And,as a result, once the market connects the dots between trillion-dollar decarbonization challenges and the handful of companies actually solving them, Brenmiller’s share price trajectory may more than steepen—it could go parabolic.
Sources and references:
https://thundersaidenergy.com/2021/02/18/industrial-heat-the-myth-of-electrify-everything/?utm_source=chatgpt.com
https://tes-h2.com/green-cycle/step-2-green-hydrogen
https://finance.yahoo.com/news/heliogen-inc-announces-fourth-quarter-201500054.html
https://bren-energy.com/projects/
https://bren-energy.com/press-releases/
https://app.dealroom.co/companies/antora_energy
https://forgeglobal.com/rondo-energy_stock/
https://finance.yahoo.com/news/zeo-energy-corp-acquire-heliogen-103000845.html
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