For thermal battery startups, the median post-money valuation is up 81.9% year over year

Batteries have a wild history.

Don’t believe me? Consider this: The first real battery was invented by an Italian physicist in 1800, a time when people believed electricity could exclusively be generated by organisms. Inspired by galvanism—an idea made famous by Mary Shelley's Frankenstein—Alessandro Volta stacked some zinc and copper discs with cardboard in-between, stuck it in some saltwater, and prototyped a technology that today still underpins much of our lives.

So, the relationship between batteries, life, and the natural world has perhaps always been close. Accordingly, it perhaps makes sense that there’s a battery-specific climate tech subsector—thermal batteries. PitchBook recently released a report on the space, which is starting to produce some notable companies, and could be an area that garners more investment from VCs moving forward.

But first, what exactly are thermal batteries?

“What thermal batteries essentially do is take some sort of material, and heat it up a ton,” PitchBook analyst Ali Javaheri told Term Sheet. “And then they store that heat energy in that material, so it can then be used as heat or electricity.”

Now, one of the key issues with wind and solar energy is a pretty straightforward one: If you have wind or sun, you’re just fine. If the weather’s not in your favor, that gets tricky fast. Thermal batteries can help bridge this gap in industrial settings and may prove adaptable to existing systems.

“It might be able to blend well with existing power grid infrastructure, whether it's connected to geothermal plants or to solar thermal energy,” said Javaheri.

Some key statistics, per PitchBook: Thermal battery startups have had a $35.4 million median post-money valuation over the last 12 months, up 81.9% year over year. In that same time, there’s been $309.1 million in capital invested, up 103.6% year over year. Compared to say, AI, that might seem modest, but it’s clearly a growing market.

Some key startups are beginning to emerge in the sector, namely Antora Energy, Fourth Power, and Malta. In December 2023, Fourth Power raised $19 million, while Malta raised a $21.6 million Series C, at a $130.4 million pre-money valuation.

And then there’s Antora, which raised a whopping $150 million Series B in February, with Decarbonization Partners leading the round. Other Antora investors include Temasek, Lowercarbon Capital, Overture VC, and Emerson Collective.

I got in touch with Justin Briggs, Antora's COO and cofounder, who agrees with Javaheri that the industrial electricity market is a good proxy for understanding what the total addressable market for thermal batteries could look like. And, for Briggs, the TAM is linked to the level of impact the technology could have on climate change.

“The industrial manufacturing sector is responsible for about 30% of global greenhouse gas emissions, the single biggest bucket of emissions on Earth,” Briggs told Term Sheet. “It’s bigger than transportation, bigger than the electric grid…Currently, that's a $1.1 trillion per year market for industrial energy.”

I’ve been hearing murmurs that climate tech has fallen out of vogue. And while I believe it anecdotally, the data doesn’t unequivocally bear out that it’s a sector stalled at all. Yes, last year, VC investment in climate tech fell 14.5% to $41.1 billion, according to PitchBook data. But that was true almost across the board last year, a tough one for VCs. And that’s still tens of billions flooding into climate tech, bolstered by government-backed incentives.

All this said, I’m not seeing there being a major bull market for thermal batteries any time soon. VCs got really burned in Clean Tech 1.0, and thermal batteries are still, well, batteries, not a product known for its sex appeal.

But this strikes me as a space that could beget some great companies. Batteries have a wild history, and there could be another chapter in the works.

We're reading...Tiger Global gathered about $2.2 billion for its latest fund—far less than the $6 billion target the firm set, as reported by Bloomberg.

Good news for IPOs…IPOs are starting to look like they’re back. Cybersecurity company Rubrik has filed to go public, and we now have an S-1 to peruse. For the year ending Jan. 31, Rubrik posted a net loss of $354.2 million (more than the preceding year), and subscription revenue of about $537.9 million (a jump of nearly 50% from the year prior). Rubrik will list on the New York Stock Exchange.

Elsewhere…The Trump Media & Technology Group, parent of Truth Social, reported a $58 million loss for 2023, and there's some amazing discussion about the performance metrics, or lack thereof, in its filing.

See you tomorrow,

Allie Garfinkle
Twitter: @agarfinks
Email: alexandra.garfinkle@fortune.com
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This story was originally featured on Fortune.com