The Wackiest Climate Tech Bets of 2025

Not even 12 months of unceasingly bleak climate news could keep climate tech founders and funders from getting involved in some seriously sci-fi sounding ideas. While the first half of the year may have been defined by a general retrenchment, the great thing about about early-stage venture capital is that it very much still allows for — nay, encourages — the consideration of technologies so far beyond the mainstream that their viability is almost entirely untethered from current political sentiment.

Below are seven of the most fantastical technologies investors took a bet on this year, with almost all announced in just the past quarter alone. In an undeniably rough year for the sector, perhaps VCs are now ready to let their imaginations — and pocketbooks — run just a little bit wilder.

1. Terraforming robots

In November, the startup Terranova emerged from stealth with $7 million in seed funding and a plan to lift low-lying areas out of flood zones by deploying robots to inject a wood-based slurry deep underground, thereby raising the land above sea level. The lead investors were Outlander and Congruent Ventures.

“Terranova’s mission is nothing less than to terraform the earth and usher in a new era of resilience and societal abundance,” Terranova’s 24-year old CEO Laurence Allen said in a press release. He cofounded the company with his father, Trip Allen, who lives in the flood-prone Bay Area city of San Rafael.

The company says that its system, which consists of three robots and one “mothership,” can lift one acre by a foot per day, making it more cost-effective than other options for defending against climate change-driven flood risk, such as building a levee or a sea wall. Already the startup has quoted San Rafael $92 million to lift about 240 acres of land about four feet.

2. Space solar

Not one, but two space-based solar companies made headlines this year. Just this month, Overview Energy emerged from stealth with plans to deploy satellites that beam energy via lasers directly to Earth, targeting preexisting utility-scale solar farms. The company has already raised $20 million in seed funding in a round led by Lowercarbon Capital, Prime Movers Lab, and Engine Ventures, and is now raising a Series A expected to close next spring.

Back in April, another space-based solar startup called Aetherflux raised a $50 million Series A led by Index Ventures and Interlagos. That funding will support the startup’s first launch, targeted for next year, which will deploy a constellation of satellites into low-earth orbit — a far lower altitude than Overview is targeting. These satellites will also use lasers to transmit solar energy to ground stations on Earth, where the power will be stored in batteries for later use.

If these companies can prove that their tech actually works in space, they have the potential to turn solar into an always available, 24/7 resource. That’s not going to happen in the next few years, though. Overview’s CEO Marce Berte told me that the company is aiming to put megawatts of power on the grid by 2030 and gigawatts by the mid-2030s, with the ultimate goal of building a system that can deliver the equivalent of 10% to 20% of global electricity use by 2050.

3. Acoustic fire suppression

Did you know that low-frequency sound waves can extinguish a fire? It’s a relatively well-understood phenomenon, but now one company, Sonic Fire Tech, has raised $3.5 million to turn this hypothetical concept into a commercial firefighting tool. With a seed round co-led by Khosla Ventures, Third Sphere, and AirAngels, the startup hopes to launch pilots with homeowners, utilities, and firefighting agencies at the beginning of next year.

As Scientific American explained, the system emits low-frequency sound waves below the threshold of human hearing, which prevent and extinguish flames by displacing oxygen away from the fuel. This deprives a potential or existing fire of the air it needs to sustain combustion. The system can channel the soundwaves through ducts atop a building’s roof and beneath its eaves, or be installed on utility equipment. There’s even the potential for a “sonic backpack,” which would offer portable protection for firefighters.

The startup’s goal is to produce 500 units by the second quarter of next year, and it’s now seeking public-sector grant funding as well as partnerships with insurance companies for its novel “infrasound-based fire suppression.”

4. Solar geoengineering

My colleague Robinson Meyer broke the news in October that an Israeli geoengineering startup called Stardust Solutions had raised a $60 million round led by Lowercarbon Capital. The company aims to develop tech that would enable solar radiation management — an as-of-now hypothetical method of cooling the planet by injecting aerosols into the stratosphere to reflect sunlight away from Earth — by the end of the decade.

The tech is controversial, however. Many experts believe that solar radiation management systems, if they’re developed at all, should be built by governments after much public deliberation. Stardust, by contrast, is a for-profit company seeking patent protection for its proprietary sunlight-reflecting particle. While the company says that the particle meets certain standards for safety and reflectivity, it has not disclosed what those standards are or anything about its composition.

The company’s CEO, Yanai Yedvab, said that Stardust is farther along than any other research efforts, public or private. And while some dispute the viability of Stardust’s proprietary particle, the fact that the company received a vote of confidence from a prominent climate tech VC indicates that this tech is entering the mainstream. As Rob put it, “Stardust may not play the Prometheus here and bring this particular capability into humanity’s hands. But I have never been so certain that someone will try in our lifetimes.”

5. Fusion at sea

Though climate tech investors have poured millions into the long-held dream of fusion energy, we’re likely still a long ways away from connecting a commercial reactor to the grid. But one startup, Maritime Fusion, is already looking to put fusion reactors on ships. The company raised a $4.5 million seed round last month led by the transportation firm Trucks VC to do just that.

The startup is developing a low power-density tokamak reactor that requires less power and less uptime than grid-connected power systems. According to TechCrunch, the startup projects that its first reactor will be up and running by 2032 and will cost about $1.1 billion to build, a far lower price than reactors on land will likely command. Another potential advantage is that at sea, fusion won’t have to compete with low-cost solar and wind resources, but rather more costly green shipping fuels such as ammonia and hydrogen.

"Breakeven fusion is on the horizon, but the grid may not be the first place fusion achieves commercial success," said Maritime Fusion’s CEO Justin Cohen in a press release.

6. Underwater pumped hydro

Even with the rapid rise in grid-scale batteries, pumped storage hydropower still leads the world in total energy storage capacity. But traditional pumped hydro is costly to build and only feasible in specific geographies. One startup, Sizeable Energy, thinks it can overcome these constraints by building pumped hydro out at sea, raising $8 million in a round led by Playground Global to do so.

Traditional pumped-hydro systems store energy by using excess electricity to pump water into an elevated reservoir, then releasing it downhill through turbines when demand rises. Sizeable’s concept is the same, just offshore: One reservoir floats on the water’s surface, while the other — connected by a pipe and turbines — sits on the seafloor. When power is plentiful, brine is pumped into the upper reservoir; when it’s scarce, the brine gets released. And because that brine is heavier than the surrounding seawater, it naturally flows downwards to spin turbines.

Sizable is now working to deploy its pilot plant in Italy, with the goal of installing commercial projects at a variety of sites around the world next year.

7. Underground SMRs

This one’s a bit of a bonus. Technically Deep Fission, a startup planning to build tiny fission reactors in underground boreholes, raised its pre-seed round last year, But this year it went public via a curious SPAC merger on the lesser-known stock exchange OTCQB, raising $30 million in the process.

The idea is that building a reactor a mile underground will save costs and enhance safety, as it negates the need for the large pressure vessels and containment structures that are typically responsible for holding a reactor in place and preventing radioactive leaks. Instead, the company says that the surrounding rock will serve as a natural barrier and containment vessel.

But as Latitude Media pointed out, some are questioning whether the recent raise will be enough for the company to build what’s sure to be an expensive pilot by next July — as it aims to do — and to deploy reactors at the three project sites that it’s already announced. Next year certainly promises to be a reckoning for the hitherto unconsidered fortunes of the underground small modular reactor industry.