A San Francisco nonprofit has published a detailed road map of the experiments, studies, and infrastructure that it says would be needed to make informed decisions about the use of solar geoengineering, MIT Technology Review can reveal.

Scientists have now spent half a century exploring the possibility that we could counteract climate change by releasing reflective particles into the stratosphere, mimicking the cooling effects of volcanic eruptions. 

But even after at least hundreds of studies on the concept, known as stratospheric aerosol injection (SAI), big gaps remain in the scientific understanding of how well it would work and what else it might do—and there has been no systematic plan for clearing up that uncertainty.

Reflective, a research organization that funds studies on solar geoengineering, has today attempted to fill that gap with the release of its SAI Research Roadmap.

“Our mission is to equip the world with the data and tools required for informed decision-making about sunlight reflection fast enough to matter,” says Dakota Gruener, the organization’s cofounder and chief executive. “Our sense is the world may need to make very consequential decisions on timelines far shorter than our research system is prepared for.”

The hope is the exercise will guide scientific efforts and encourage philanthropies or government agencies to fund high-priority work and “responsibly accelerate research,” says Gruener.

If all the work is done in a coordinated way, it would take about a decade and cost around $370 million—and if it’s not, it would require roughly 20 years and nearly $1.4 billion, the report estimates.

While Gruener stresses that Reflective doesn’t advocate using this form of solar geoengineering, the report does make the case for conducting outdoor experiments, which would release successively larger amounts of sulfur dioxide (or materials that would convert into it) in the stratosphere to observe what happens.

That is a controversial standpoint. Since 2002, hundreds of academics have signed an open letter calling for a ban on outdoor experiments and an “international non-use agreement,” arguing that such a powerful technology could never be governed in a globally equitable way. And some signatories argue that more studies can never address one of the biggest questions about using solar geoengineering: Who gets to do it.  

“The first-order questions, from my perspective, are not technical,” Aarti Gupta, co-initiator of the non-use initiative and professor of global environmental governance at Wageningen University in the Netherlands, told me in a recent on-stage interview. 

“The core question is: Who would control a planet-altering technology like stratospheric aerosol injection? Who would develop it, and who would deploy it, and to what end? To serve what purposes, and whose purposes? Those questions are very fundamental, because this planet-altering technology will have winners and losers.”

‘Fast enough to matter’

Since Gruener incorporated Reflective in late 2023, the nonprofit has quickly become an important  player in solar geoengineering research. It has now raised more than $20 million from a number of prominent charities and individuals, and it’s provided around $4 million to several dozen research groups. Reflective has also undertaken a handful of its own projects to promote research, including the development of an open-source solar geoengineering simulator and an online hub for collaborative research.

Earlier this year, Reflective released its SAI Uncertainties database, which identified a long list of scientific unknowns and  engineering obstacles that would need to be addressed before even a small-scale solar geoengineering effort could move ahead. (I wrote about the specific scenario and the unknowns in this earlier piece.)

Some of the biggest uncertainties involve what gas or particles would make the most sense to use and what would happen once they were released in the dry stratosphere. It’s not clear, for example, whether they’d spread out in a way that maximizes the reflectivity—or clump together and quickly fall out into the troposphere, the lowest layer of Earth’s atmosphere. 

The road map builds upon the database, highlighting the path to addressing most of those questions. 

The road map

The initial phase in Reflective’s road map, labeled “foundational knowledge,” includes additional computer simulation studies and lab experiments designed to shed light on the potential impacts on different regions, ecosystems, and phenomena, including ocean circulation patterns, ice sheets, and crop yields. 

The report also notes the need to begin developing more observational tools during this phase to improve understanding of the baseline conditions of the stratosphere—and, in turn, our ability to assess any effects from the eventual release of materials.

This first stage would last two to three years and cost $30 million to $75 million, though some of the analysis and observational work would continue into subsequent phases. 

The next stage would include using modified aircraft to release 10 metric tons of sulfur dioxide into the stratosphere, four times over the course of two seasons. The full research stage could take four to eight years and cost $70 million to $150 million, the report says. The work during it may reduce uncertainty about the “cooling efficacy” of solar geoengineering, or how much the planet would cool per ton of sulfur released, by about 25%.

The experiments during the next phase would step those levels up dramatically, releasing 25,000 tons of sulfur dioxide over the course of one season, at least once but possibly twice. That research stage, which includes other work as well, would last four to 11 years, run $270 million to $1.1 billion, and decrease efficacy uncertainty by around 66%, according to the road map.

The final phase of research would be ongoing monitoring of full-scale solar geoengineering, if the world goes ahead with it. The goal would be to gather real-life data on the technology in action, update estimates of the effects in models, and spot any “unexpected or undesired consequences.”

Gruener says that the road map is intended as a Version 1, meant to be “concrete enough for people to argue with.” But Reflective intends to update the plan as it receives additional reactions from researchers and other observers, and it will invite such feedback through a mechanism on the site.

She also notes that there are firm “stage gates,” set up between the latter stages—in other words, research shouldn’t proceed to the next phase if the experiments suggest that the releases don’t have the hoped-for impact, show worrisome downsides, or fail to resolve crucial uncertainties.

“Our road map has these gates precisely because there may be points where the answer is ‘You should stop,’” she says.

Termination shock

Most observers I spoke to about the report agree that these studies could reduce uncertainty about the effectiveness of solar geoengineering and our technical ability to carry it out. 

But highlighting the scientific importance of outdoor experiments won’t necessarily make them any easier to move ahead with. Several earlier proposals to carry out such experiments, including Harvard’s SCoPEx and the UK-based SPICE project, were ultimately halted amid opposition from environmentalists or policymakers.

In addition, not everyone agrees that experiments at those scales will get us to the point where we’re capable of making an “informed decision.” 

Wil Burns, a research professor and legal scholar at American University and a signatory to the International Non-Use Agreement, fears that scientists won’t be able to understand the extent of the potential downsides, including impacts on the protective ozone layer and changes to regional precipitation patterns, until we’re carrying out full-fledged solar geoengineering.

“The research would give you some answers,” he says. “I just don’t think it gives you answers that are that relevant. To get to those relevant answers, you have to deploy at scale—and I just don’t think that’s ever tenable.”

That’s because, in his view, using the technology would violate principles of intergenerational equity: If the world continues emitting greenhouse gases, increased levels of solar geoengineering would merely mask the continued warming of the planet. Burns says that means future generations—people who had no say in its use—couldn’t turn it off without triggering a sudden surge of warming, known as termination shock. 

“What that would do, in my mind, is put a sword of Damocles over future generations,” he says. “So even if you could, quote-unquote, ‘prove it works,’ I don’t think from an intergenerational perspective it would ever be tenable.”

(Some researchers, however, have argued that the risks of termination shock are less likely than often assumed—and that solar geoengineering could be slowly dialed down over time.)

‘The right approach’

Ilan Gur, the former CEO of the Advanced Research and Invention Agency (ARIA), the UK research department that funded 21 geoengineering research projects last year, applauds Reflective’s road map. 

“Whether you’re a scientist or a policymaker or just a concerned citizen, our goal should be as quickly and efficiently as possible to answer the biggest questions scientifically that would tell us [whether] this is an approach that might work or that would never work,” he says. “We should all want to spend the effort and money to buy down that uncertainty, so my view is 100% the approach that Reflective is taking is the right one.”

Sebastian Eastham, an associate professor in sustainable aviation at Imperial College London who is leading an ARIA-funded research project exploring another approach to engineered cooling, agrees that the outdoor experiments described in the Reflective road map can’t resolve all the unknowns. But he says the map helps begin a conversation about how to make decisions concerning the use of a tool with potential benefits and risks, in the face of escalating climate dangers.

“Every hard decision that has ever been taken has been in the context of unresolved uncertainty,” he says. “That’s just the nature of things.”

Eastham adds that it’s become essential to move beyond computer simulations to address some of the key questions, arguing that appropriately designed and executed outdoor experiments can teach us so much more than millions of hours of computational processing time “that it almost becomes irresponsible to say, ‘Well, there cannot be ever any experiment.’”

The risk is “that we spin our wheels running the same computational simulations over and over and over again,” he says. That could prevent researchers from learning essential things about the effectiveness or the dangers of stratospheric aerosol injection. 

Weighing the risks

Gruener says the risks that solar geoengineering could exacerbate inequality need to be considered, but notes that unchecked warming also threatens to disproportionately harm developing regions.

She also acknowledges that outdoor experiments won’t fully address the scientific unknowns but stresses that they can answer a lot—and carry little environmental risk. She notes that 10 tons of sulfur dioxide is less than 2% of the amount that the global aviation industry releases into the atmosphere each day.

“Some people will be uncomfortable with any discussion of any outdoor experiment, but if we want decisions made on good science … then these are questions that an experiment will be necessary to address,” Gruener says.

She fears that the rising dangers of climate change will put growing pressure on nations and other actors to move forward with solar geoengineering, even if no one has done the necessary research to reduce scientific uncertainty and sort out the technical challenges.

“We don’t think the alternative is decisions not happening at all,” she says. “We think the alternative is decisions being made in a panic or on lack of evidence.”

The US is hitting records for the rapid growth of its energy storage market. That’ll go a long way to shoring up the grid, increasing reliability and also cutting emissions, since batteries can help store energy from intermittent renewables like wind and solar.

Crucially, this is all happening with the help of cheap Chinese batteries, though there’s been a concerted effort to reduce the US’s reliance on them. Most recently, in an executive order in late August, the Trump administration declared a national emergency that essentially bans Chinese batteries from being used in grid-scale energy storage systems.

There’s an argument to be made about reducing reliance on any single source of a crucial energy technology. But all this tension raises a broader question for me: How much should countries take advantage of cheap, available tech, versus cutting off major sources to force development of their own factories even if that comes at a higher cost?

This is hardly America’s first push to move away from Chinese influence in the battery supply chain. One of the major policy tools used in recent years is restricting the tax credits designed to incentivize use of the new technologies. Limiting the types of projects that are eligible can help reduce the cost of local technologies so they’re more competitive with otherwise cheaper imported options.

Back in 2022, the US government designed the tax credits that were part of the Inflation Reduction Act to restrict where a battery’s minerals could be mined, processed, or recycled, as well as where a battery and its components were assembled.

Those tax credits underwent a makeover in 2025, but the Trump administration has taken a similar tack. New legislation requires that starting in 2026, 55% of the cost of materials used for new energy storage projects must come from outside China and other restricted countries or the projects won’t qualify for tax credits. 

And we can’t forget about tariffs. Import taxes for batteries increased to 25% in January, up from 7.5%.

But the new executive order is a more drastic move. It bans the installation of “any foreign-produced bulk-power system electric equipment” that poses a national security risk. The order specifically calls out battery energy storage systems, as well as inverters and transformers.

“An outright ban was a bit of a surprise, and it does create a bit of concern for domestic players in the US,” says Shan Tomouk, energy storage and energy lead for Benchmark Mineral Intelligence, an energy industry analyst.

The move is likely to slow deployment of grid-connected energy storage projects in the near term, according to analysis from BloombergNEF, an energy consultancy. Projects could face delays as developers wait for clarity on the rules.

Depending on the detailed guidance from the Department of Energy, which is expected by the end of the year, some projects may need to find alternative sources for their cells, whether they’re domestically produced or imported from other countries. These will likely be more expensive than Chinese imports, says Isshu Kikuma, an energy storage analyst at BloombergNEF. “Worst case, those projects could get canceled,” he says.

Technically, the order applies even to existing energy storage plants, though it’s unlikely that they’ll be taken offline because of their batteries’ origin. Since most of these plants currently use Chinese batteries, enforcing the order to the letter would essentially mean removing most installed battery energy storage from the US grid, Kikuma says.

In the longer term, the US will eventually be able to meet its own demand for batteries. The country could have enough capacity by about 2030, though some factories may not ramp up or run at their full capability, meaning domestic supply won’t actually meet demand until later in the 2030s. 

New factories from LG Energy Solutions, Samsung SDI, Ford, and SK On are set to come online or ramp up by next year. In an ironic twist, a slowing EV market is helping, as some factories originally designed for vehicle batteries are retooling to build cells for grid storage instead. 

But it will come at a cost. Today, batteries produced in the US are still significantly more expensive than those made in China. Even switching to imports from other countries like South Korea would likely be more expensive.

This is a crucial issue that goes beyond the US and even beyond batteries. China is miles ahead of much of the rest of the world on technologies like solar panels and batteries. Through years of government support and experience with research and manufacturing, the nation is an energy powerhouse.

There’s a delicate political balance to maintain as the world figures out how to navigate this situation. There’s cheap technology on offer, which can help drastically reduce emissions and energy costs. But there can be risks associated with relying too much on any one player for crucial technologies.

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Battery installations hit a new record in the US in the second quarter of 2026. In total, 20.2 gigawatt-hours of new capacity came online, according to a new report. That’s enough to supply the daily electricity needs of about 700,000 homes.

The surge is putting the country on a trajectory to see 71 gigawatt-hours of batteries installed in 2026, a 20% increase over last year. This growth is being driven by a combination of cheaper batteries and an urgent need for more energy storage capacity as renewables such as solar and onshore wind power are added to the grid. 

Massive, utility-scale systems are leading the way; they’re responsible for most of the record-setting quarter. Seven new gigascale battery installations (those with a capacity of over one gigawatt-hour) came online during the three-month stretch, according to the report, published by Benchmark Mineral Intelligence and the Solar Energy Industries Association.

“It really came down to a handful of big projects,” says Shan Tomouk, energy storage and energy lead for Benchmark Mineral Intelligence.

But there was also growth in the category of so-called behind-the-meter batteries, which include both residential and industrial battery storage systems. These projects, generally smaller than utility-scale installations, are typically owned and operated by homeowners or businesses rather than utilities or power providers. 

In the behind-the-meter category, data centers led the way, making up about three-quarters of new batteries in the commercial sector. But residential batteries saw a sharp slowdown. These systems are often installed in homes to store power from solar panels or serve as a backup source in case of a blackout. Home installations are projected to drop by 16% in 2026 compared with last year, according to the report.

That drop happened largely because a tax credit that helped subsidize home battery systems ended in 2025, Tomouk says. Home installations should recover by the end of the decade, he adds. And tax credits for nonresidential batteries have largely survived.

Overall, batteries are a bright spot in energy right now. “This is one of the strong sectors in the US,” says Isshu Kikuma, an energy storage analyst at BloombergNEF, an energy consultancy.

As the battery market continues to grow, one major trend to keep an eye on is a move toward US-made technology. Today, nearly all the systems coming online use cells made in China, though some are put together into complete energy storage systems in the US.

Tariffs were already pushing the US energy storage industry toward domestic production. And beginning this year, energy storage tax credits required projects to limit their reliance on batteries imported from China. There’s a lot of manufacturing capacity set to come online in the US, though these factories probably won’t be able to meet demand until at least 2030 or so, Tomouk says, so prices could tick up.

The steel industry isn’t exactly known for innovation. Very little has changed about purifying iron ore since the process was invented and commercialized in the 1850s.

The majority of steelmakers melt solid iron ore at dizzyingly high temperatures inside blast furnaces, where the material reacts with gases to trigger chemical reactions that remove oxygen. It then undergoes further refining to purify it before it is made into products like rebar and car frames.

The process relies on coal, and it generates roughly 7% of the carbon emissions that drive climate change—about as much as the fashion industry. Decarbonization has proved difficult: Profit margins are tight and furnaces have long service lives, making investment tough to justify.

Now Laureen Meroueh may have found a way to clean up steelmaking without driving up the price. Meroueh, the founder of Hertha Metals, invented a new furnace that simplifies the chemistry behind the process. Her method turns iron ore into refined liquid steel in a single step, and it swaps coal for natural gas. Together, those changes slash emissions by at least half, she says, and cut costs by 25% compared with steelmaking business as usual.

If it catches on, the tech could be transformative. “There’s huge value in reducing the size of this production system,” says Iryna Zenyuk, director of the National Fuel Cell Research Center at the University of California, Irvine. “They’re massive. They’re inefficient and require a lot of energy input, so even if they just save energy efficiency, that’s already a big step.”

Hertha’s approach focuses on what it can fix about the steel industry now, as opposed to waiting around for a zero-carbon system.

Still, it’s a risky endeavor, but pushing limits isn’t new for Meroueh. At 12 she was accepted into a pilot program to take college-­level courses through Florida Atlantic University in lieu of a traditional secondary education. She was immediately drawn to engineering and explored topics including calculus and ocean wave energy.

Despite the rigorous coursework, she would spend hours sitting in trees and surfing, which fostered a deep appreciation for nature and a desire to safeguard it. “I don’t know how you can’t be drawn toward trying to help protect that,” she says. 

Now 34, Meroueh has let that passion inform her professional goals. After finishing her PhD in mechanical engineering at MIT, she led a green hydrogen startup before founding Hertha in 2022. A first-generation Lebanese-American from an entrepreneurial family, she saw starting her own company as a typical path. “Seeing how common it is to take that jump to start your own business is what made me feel like ‘This is normal,’” she explains on a video call from her office at Hertha’s pilot plant in Conroe, Texas, just north of Houston.

That facility can produce one metric ton of steel per day. “One ton per day is a big metric for steel,” says Rajesh Swaminathan, a partner at Khosla Ventures, one of the company’s investors. (Hertha had raised about $20 million in funding as of July 2026.) 

Swaminathan says the company’s scale-up is “impressive,” especially given how little the team has spent. Competitors, he notes, have created far less steel with $50 million or $100 million in funding.

Hertha’s approach focuses on what it can fix about the industry now, as opposed to waiting around for a zero-carbon system. While other approaches to making green steel center on using hydrogen to free oxygen from iron ore—a method that could one day cut or eliminate emissions—Meroueh says Hertha is content for the time being with a continued reliance on fossil fuels, mainly to keep costs down. The current Hertha plant could eventually switch to a fully decarbonized system without drastically changing the hardware, she says, if hydrogen becomes more affordable. 

In the meantime, plans are underway to expand into a new plant next to the existing one. The facility is slated to produce 10,000 metric tons of high-purity steel per year and should reach full capacity by the end of 2027. By 2030, Meroueh believes, Hertha can up its output to 500,000 metric tons per year with the addition of a third site. That’s only a fraction of the approximately 80 million metric tons of steel produced annually in the US, but Zenyuk says making even one metric ton is still an achievement.

In Meroueh’s mind, the world isn’t going to outgrow its need for steel, so she’s asking another question: “How can we be smarter about how we make things … so that it’s also not going to harm us in the long term?”

In June 2024, a small company called Zanskar purchased a geothermal power plant in New Mexico that was failing fast. The water coming from the underground reservoir was getting colder by the day, making the plant uneconomical to run.

Now, two years later, that plant is running at full capacity again, thanks to a new well. With the help of advanced modeling and modern drilling technology, the company was able to identify a better potential well site, drill down thousands of feet, and revive the entire operation.

As the world looks for more sources of emissions-free electricity that are available 24-7, Lightning Dock shows there’s still hidden potential deep beneath our feet. 

Conventional geothermal power plants rely on having the right underground conditions. Water flows through fractured hot rocks to harvest heat and then through a power plant to generate electricity. If the water isn’t hot enough or not enough flows, the power plant can’t work efficiently.

Lightning Dock came online in 2013, and the site historically had two production wells that were used to feed the power plant. It’s common to see temperatures drop at a well site over time, typically at a rate of 1 to 2 °F per year. In the period before Zanskar took over the site, Lightning Dock saw temperatures drop by 50 °F over five years, a rate of 10 °F per year. When the company purchased the facility, the water going into the power plant was just 250 °F, while the plant was designed to operate at temperatures of at least 310 °F. 

When Zanskar mapped the underground conditions at Lightning Dock using advanced modeling techniques, they discovered that the wells were only hitting the very top of the reservoir there. Those production wells were quite shallow (at just 2,500 feet deep) and not in the best location, says Joel Edwards, Zanskar’s cofounder and CTO.

The company’s modeling predicted that if the company were to drill another, deeper well in a new spot, the plant would be able to run efficiently. The team drilled a new well that reaches a depth of 8,000 feet and started operation in May 2025.

After a full year, the well is still flowing at more than 4,000 gallons per minute. The plant has “completely turned around,” Edwards says. “It looks really exciting.”

The data so far shows that the plant should be successful for years to come. “Ultimately you need to run these things for long time frames to get confidence in their performance over long time frames,” Edwards says.

The progress at Lightning Dock could be good news for other geothermal sites too. The conventional wisdom in geothermal energy is that the deeper you go, the hotter it gets. But there’s usually a trade-off: With those depths come rocks that are packed tighter together. So drilling deeper could mean the hot water can’t flow as effectively, a problem for anyone trying to use it to generate electricity in a power plant.

What the team found, however, was that the flow actually increased in the area where they drilled the new well. “That fundamentally changes how you think about not just Lightning Dock but all hydrothermal assets in America and what the potential can be for all of them,” says Ben Brenner, director of federal affairs at Zanskar. 

Over the past year of operation, Lightning Dock generated over twice the electricity it would have with the old wells. This is a relatively small power plant, with a capacity of 15 megawatts going to the local grid (about enough to power 11,000 US homes).

Oil and gas developers have chased resources deeper underground over the past few decades. Operations started relatively close to the surface, but oil and gas production can stretch down 20,000 feet or more today. “I think that arc is going to play out in geothermal,” Edwards says. While typical geothermal well fields range from 3,000 to 5,000 feet deep, it could become more common to go deeper in the future, he adds.  

The company plans to do further development at the Lightning Dock site: with a few years of development and an upgrade to the power plant, it could get even more electricity out of this area, Edwards says.

There’s been a lot of buzz and investment in enhanced geothermal systems—projects that aim to expand where geothermal resources can be used. Fervo Energy, for example, uses fracking techniques to open up rock that would otherwise be too closed off for traditional geothermal energy.

But there’s still plenty of “low-hanging fruit” in the geothermal world, Edwards says. Many of these conventional resources have plenty of potential—they just need a second look.

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Correction: A previous version of this article misstated the title of Joel Edwards. He is Zanskar’s CTO, not CEO.

On July 3, as a heat wave swept the region, New York State’s grid imported 52 gigawatt-hours of electricity from Canada—enough to meet about 9% of its total electricity demand that day.

Some of that power shuttled in on a 339-mile power line stretching from Quebec to Queens called the Champlain Hudson Power Express (CHPE). It opened in May and is officially the longest underground transmission line in North America.

An underground power line might not sound all that exciting, but this could be a big deal for the state’s grid planning, and for emissions. It could provide up to 20% of New York City’s electricity demand, largely with abundant hydropower from Quebec.

One wrinkle: The line has been down for most of this month, and some experts are concerned about how drought will affect the power supply feeding it. Let’s look at how the CHPE transmission line could help shape the future of our grid, and what barriers it needs to overcome to make a difference.

Planning for the CHPE (which is charmingly pronounced “chippy”) started 15 years ago, with the permitting process formally beginning in March 2010. The vision was to build infrastructure to better connect Quebec and southern New York.

Over 99% of Quebec’s electricity comes from renewable sources; most demand is met with hydropower, though the province’s wind capacity is growing quickly. New York has some hydropower of its own, as well as nuclear and wind, but the state still relies on fossil fuels for most of its energy generation.

Transmission Developers, a company owned by the alternative asset management firm Blackstone, and Hydro-Québec, the province’s manager of generation and transmission, partnered to build CHPE. Construction began in late 2022 and wrapped up earlier this year. The total cost for the privately funded project turned out to be  $6 billion.

The construction of this line was a feat. It’s made up of a bundle of two high-voltage direct-current power cables, each measuring roughly five inches across. Developers buried the bundle underground or underwater across the length of New York State. Much of the line was laid at the bottom of the Hudson River, requiring special boats that shot water jets deep into the sediment to create trenches for the cable.

Connecting grids together can help accelerate the transition away from fossil fuels. The ability to move electricity to where it’s needed could also help limit the amount of new capacity we need to build. Research has shown that interconnection can help cut emissions and lower system costs.

But CHPE is off to a slow start and has seen two outages so far. The first, on July 1, was reportedly caused by a trip at a converter on the Canadian side of the border. The second outage began on July 4, and the power line is still down as of the morning of July 22.

Some experts say this isn’t unusual for a new infrastructure project. Other power lines have seen similar startup challenges, and the equipment hasn’t really been fully tested until it’s in operation, Normand Mousseau, a physics professor at Université de Montréal, told the Gazette.

Officials traced the issue to a damaged section of cable on the US side of the border, and the company that manufactured the line sent experts to investigate the cause, according to reporting from RTO Insider, a trade publication. 

The damaged portion of the cable has been removed and replaced, says Lynn St-Laurent, a spokesperson for Hydro-Québec. “It is currently estimated that the remaining work, including necessary post-repair testing, will be completed by the weekend.”

Similar woes have afflicted the New England Clean Energy Connect line, which opened in January, stretching 145 miles from Quebec to Maine. That project has also seen outages, and very little additional energy has flowed into the Northeast.

The good news for New York is that the grid wasn’t relying on CHPE yet. “Our planning studies did not assume CHPE would be available this summer, and that was one reason the grid performed reliably during the heat wave earlier this month,” Kevin Lanahan, a spokesperson for the New York Independent System Operator, the state’s grid management company, said in a statement. “A core principle of reliability planning is not relying on any single project.” 

The idea is that eventually, states and regions will be able to rely—at least in part—on these projects, so there is pressure to get them working smoothly: Building massive transmission lines is a major long-term investment. In future years, as the equipment gets stress-tested and utilities begin to feel more confident in the projects’ reliability, they could play a bigger role on the grid.

One thing to keep an eye on moving forward is the condition of Quebec’s hydropower fleet: The region has seen intense drought for the past three years, eating into the water reserves used to generate electricity. That could mean there won’t always be abundant hydropower to ship across the border—even if the transmission lines are able to carry it. 

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

It feels as if it should be illegal to even think about heating appliances during the height of summer—seriously, these heat waves in New York have been brutal—but we need to talk about heat pumps.

The appliances use electricity for heating, they’re incredibly efficient, and they’re on the rise. (For what it’s worth, many heat pumps can also be run in reverse to cool buildings.) In the US, heat pump sales have doubled over the past 15 years, according to a new report. And they’re winning the heating race against fossil fuels, outpacing natural-gas furnaces by 32% during the first quarter of 2026.

These stats are especially striking at this moment, because a key tax credit for heat pumps just ended with the close of 2025. But you wouldn’t know it from looking at the data. Why are heat pumps still so hot?  

In case you need a quick refresher, heat pumps use electricity to essentially move heat from one spot to another. A refrigerant moves around a loop in the device, expanding and compressing, gathering and releasing heat at different points in the cycle. (For a more in-depth look at the thermodynamics, this explainer I wrote in 2023 still holds up.)

The result is an appliance that can be incredibly efficient. Once you pay for and install a heat pump, it’s generally significantly cheaper to run than a gas or oil furnace or other types of electric heating systems. And because they’re more efficient and don’t involve burning fossil fuels, heat pumps can be a major help in decarbonizing buildings.

One of the major hurdles to wider use of heat pumps is the appliances’ cost: They tend to be more expensive to buy and install than gas furnaces. For this reason, many governments offer incentives to encourage their adoption. In the US, people who installed heat pumps between 2023 and 2025 were eligible for up to $2,000 in tax credits.

Last year, though, the Trump administration slashed those tax credits, along with many of the other incentives that were part of the 2022 Inflation Reduction Act. Effective January 1, 2026, no more financial help for heat pumps.

I think I’ve seen this film before, and I didn’t like the ending. Tax credits of up to $7,500 for new EVs ended on September 30, 2025. In the quarter leading up to that deadline, sales spiked as people rushed to take advantage of the incentive. Then they fell off a cliff. Things are starting to normalize now, but clearly the tax credit’s sunset had a major effect.

But as it turns out, heat pumps are an entirely different story. In the first few months of 2026, sales have actually gone up, as Lucas Davis, an energy economist and UC Berkeley professor, points out in a new analysis.

Heat pump shipments were flat from December to January and have seen a gradual rise since then, according to data from the Air Conditioning, Heating, and Refrigeration Institute, a trade group that represents about 90% of the US market. This increase from winter into spring follows a seasonal trend seen in previous years—and it’s actually a bit stronger in 2026.

This data isn’t what you’d expect to see if losing the tax credit were hurting demand. As Davis lays out in his post, it seems the credit wasn’t really convincing people to install heat pumps, or at least the case for doing so was sufficient without the added incentive.

“It appears that the U.S. market for heat pumps is strong enough that it does not depend on tax credits,” Davis writes.

In 2024, MIT Technology Review put heat pumps on our annual list of breakthrough technologies. “We’ve entered the era of the heat pump,” I wrote at the time.

While heat pump sales have been up and down over the last few years, the era is going strong. The appliances have outsold gas furnaces in the US for the last four years. It’s not just the US, either. Countries including China and Germany have seen strong movement to heat pumps in recent years.

There’s rarely a straight path to adoption for new technology, especially something that requires so many individual households to make a significant change. But it’s encouraging that a major decarbonization tool is going strong, even when roadblocks pop up.

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Solar geoengineering is often portrayed as a sort of emergency brake. Something along the lines of Pull in case of climate emergency to scatter light-reflecting particles to bounce sunlight out of the atmosphere and cool the planet.

But it might be less like a simple brake and more like a complicated, entirely unsolved puzzle.

Some researchers are starting to look into how nations or companies would go about trying to cool the planet—and there’s a lot to figure out. My colleague James Temple dug into these engineering challenges in his latest feature story. My biggest takeaway? This all might be a lot harder than I thought.

I’ll admit, I’ve always thought of geoengineering as a relatively low-tech solution. That’s partly because over the years we’ve seen some companies do their own low-cost guerrilla “experiments,” tossing balloons up into the atmosphere and claiming to have made some small dent in climate change.

But to actually actively cool the planet in a significant way, and to make sure we understand exactly what effect we’re having, there’s a lot that researchers still need to learn. 

First, there’s the problem of getting up into the atmosphere. Generally, the target for solar geoengineering efforts is the stratosphere, since the air there is drier and more stable, so particles deposited there would stay aloft and move around the planet, lowering temperatures over a wider area and for a longer time.

You can release the particles in balloons, but balloons may not go where you want them to. And at a large scale, you’d be leaving a lot of litter all over the planet. That leaves aircraft, but conventional planes aren’t suited to fly around in the stratosphere. (Commercial aircraft generally fly at around 12 kilometers above the Earth’s surface, while geoengineering would require reaching roughly 20 kilometers.) The air is thinner higher up, so aircraft with massive wings would probably fare better than more conventional designs.

One design, from a startup called Iris Aero, shows just how much rethinking of our current flight technologies might be needed—the plane is almost unsettling in its proportions. Its wings are so long, on a stubby little body. It reminds me of a water strider, those bugs that have super-long legs to scurry around on a pond’s surface.

And that’s just the beginning. There’s also the question of what, exactly, would be best to scatter up in the stratosphere. The idea behind geoengineering comes from volcanoes—after an eruption, sulfuric acid ends up floating around in the atmosphere, and it can temporarily cool the planet. But that chemical is sticky and would be heavy to carry, so scattering some sort of precursor to sulfuric acid would probably be better. Researchers, including some at the University of Chicago, one of the leading institutions in this field, are working to figure out the best formula. 

I’m struck by how complicated this turns out to be, and I’m also left with a big question: As research turns from modeling and simulations to the practical aspects of this incredibly controversial technology, what does it mean to be doing this work?

There are major concerns about what effects might come from large-scale attempts to cool the planet. The effects could be positive for some parts of the globe and negative for others. Established weather patterns, like the monsoon season in South Asia, could shift. There are major questions about what the governance for the use of geoengineering should look like, and who gets to decide whether to go ahead. 

Experts who champion research in geoengineering often draw a line between a desire to support learning more about the technology and a call to deploy it. Many would argue that we should understand it better, so we can make informed decisions.

But to me, there’s a clear difference between atmospheric modeling and detailed engineering work on an aircraft. If there’s public research that essentially amounts to a set of practical instructions, I can’t help but feel like it could enable any number of individual actors or nations to take geoengineering into their own hands. It also might normalize the idea of using the technology. 

Some experts shared concerns along these lines with James, arguing that the shift to practical engineering work requires more oversight. Some called research in this area dangerous.

One alternative perspective I found interesting came from Shuchi Talati, executive director of the nonprofit Alliance for Just Deliberation on Solar Geoengineering.

Rather than further practical research making a slippery slope slipperier, it could have the opposite effect, she told James. “The actual practice of R&D will be a sticky slope, because there will be more real-world problems that come up that we haven’t even thought of yet,” she says. Engineering research could challenge the “idealized notions” of how easy the technology would actually be, she adds.

It’s hard to argue against better understanding potential tools to address climate change. But if we draw a map towards a potential future, it might become difficult to control who follows it. 

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Most of Kenya’s power grid runs on renewables. But with 25% of communities lacking centralized electricity, the nation is looking to off-grid solar to hit its goal of delivering universal electricity access by 2030 without driving up emissions. The ever-­improving economics of solar technology have helped. A couple of years ago, a panel cost about $3 a watt; now it’s down to cents. 

On the margins of a bustling Nairobi, we wind past a mix of high-rises and hardware shops interspersed with small plots growing corn or potatoes. After a few minutes, we arrive at a street-side stall run by the bespectacled Milcah Wanjiru. She sells plenty of half-liter packets of milk, loaves of bread, and matches, but Wanjiru’s core business is a service: She mills corn flour for local residents, which they most often use in ugali—a common Kenyan dish that is similar to polenta, albeit less creamy. 

In the middle of her small shop, a milling machine stands on three adjustable legs. “Whenever customers came to mill their grain, they asked for other goods,” says Wanjiru, “and this is how I got to stock these other items.” 

Shops with a grain mill are common here in rural areas and most neighborhoods, especially low-income ones—even in the city. But most of these mills burn diesel fuel. Hers? It runs on either solar energy or electricity from the grid. 

Matt Carr, the CEO and cofounder of Agsol, the company that designed Wanjiru’s mill, is here with me, visiting to get her feedback on his product. One issue bothers her. “It can be slow,” Wanjiru tells Carr, explaining that grains can get stuck in the front chamber where they feed into the machine. Sometimes, the whole thing jams. 

Carr says the mill automatically reduces its speed if the grain is at all damp, so that the pulverizing hammers within can squeeze out as much flour as possible. That process can unfortunately lead to the problem she’s describing. 

Overall, Wanjiru seems happy with the machine, which she’s been using since December 2025. It makes running her business cheaper. About 40% of what shop owners who use diesel-powered mills charge customers goes toward paying for fuel, according to Carr, whereas operating Agsol’s solar-powered machine can be up to 80% more profitable once the initial cost (about $1,300) is paid off, which takes between six and 12 months. Wanjiru also likes the fact that—unlike diesel-burning models—her mill can handle very small amounts of grain, which has brought a few new customers her way.  

Carr launched the first Agsol product in 2018 in Kenya and has raised over $4 million of investment—much of that via a UK government program that supports clean energy projects in the region. Last year, Agsol sold 530 units. The company, which is based just outside Nairobi, has received orders from as far as Mozambique and Angola.

As we say goodbye to Wanjiru, she turns and bends over burlap sacks half full of peanuts, mung beans, rice, and millet, arranged neatly on wooden pallets on the cement floor. She lifts a scoopful from one of the sacks and dumps its contents on a scale. A customer waits to be served. 

Geoffrey Kamadi is an award-winning freelance journalist based in Nairobi, focusing on science, climate change, environment, technology, and development. 

Jim Franke pulls away the cover page of a presentation on the wraparound desk in his office, revealing an illustration of an odd-­looking aircraft with massive wings stretching out from a stubby fuselage.

The uncrewed plane is soaring thousands of meters higher than commercial jets fly—so high you can see the curvature of the Earth. It’s precisely the type of aircraft one would need to begin artificially cooling the planet. Those outsize wings would keep the plane and its payload aloft in the stratosphere, about a dozen miles (or 20 kilometers) above the surface, where the air is much thinner—as little as 5% the density near the ground. Once at altitude, the plane would release materials that could, after a few steps of chemistry, reflect sunlight back into space.

The concept came from volcanoes. Massive eruptions in the past have reduced temperatures worldwide by blasting sulfur dioxide and other compounds into the stratosphere, where they convert into sunlight-scattering particles. Hundreds of studies in recent decades have suggested that a human attempt to mimic this mechanism would work quickly and efficiently—at least within the confines of climate models.

But these computer simulations are approximations of how the real world works. They gloss over numerous challenges. Like the fact that aircraft capable of carrying the necessary loads to the necessary altitudes don’t exist. Or that we don’t know for sure how to release material so that most of it turns into tiny reflective aerosols instead of, say, clumping together and falling out of the sky. Or even what specific substance we would want to load onto an aircraft, given open questions about safety, cost, and effectiveness. 

Amid these compounding unknowns, more and more research on solar geoengineering is moving beyond computer simulations, delving into the detailed design and practical engineering work that would be needed before we could carry out a campaign to dial down temperatures. The tasks required range from inventing high-altitude aircraft to mastering the precise chemistry and delivery mechanisms for dispersing materials to building out the monitoring infrastructure that we’ll need in order to know if any of it actually works.

The question of whether we should geoengineer the planet has no clear-cut answer. It might save millions of lives by reducing the dangers of catastrophic heat waves, floods, droughts, and famines. But many fear it’s too dangerous to even consider, much less seriously study, arguing that we can’t possibly predict the spiraling consequences of manipulating such large, complex, interconnected planetary systems. 

Critics argue that the building momentum in this phase of research will make it ever more likely that someone, somewhere in the world, will eventually pull the trigger on geoengineering, no matter the remaining unknowns or the dangers for certain parts of the world.  

“I do think it’s very dangerous because of what we know about science and technology,” says Jennie Stephens, a professor of climate justice at Maynooth University in Ireland. “The more investment that’s made, the further the advances, the more likely it is that it will be deployed.”

But proponents of this practical research argue that playing out how we’d mount a solar geoengineering program will improve our understanding of the potential benefits and risks, helping to ensure that if anyone does try to tweak the climate, they might at least do so in an informed and potentially safer way.

It’s still very much a niche field. Much of the work now underway is happening at the Climate Systems Engineering Initiative (CSEi) at the University of Chicago, which formally launched in 2024 under the leadership of the prominent geoengineering researcher David Keith. 

Franke, a professional engineer before earning his doctorate in geosciences, is overseeing a series of overlapping research projects and collaborations aimed at resolving many of the engineering uncertainties. That includes working out the designs now on his desk—renderings of the type of aircraft that could be used in the initial phase of a geoengineering program. 

Franke argues that more computer simulations are simply not going to answer the big remaining questions in the field, including the most compelling one: the “boogeyman” of what could go wrong. 

“I’m kind of personally skeptical that additional model development or more simulations are going to satisfactorily resolve those things,” he says. “And so I’m not really that interested in turning the crank on more models.”

For Franke, it’s time for the next step: “We’re interested in seeing how you’d actually do this thing if you wanted to do it.”

What we don’t know

Solar geoengineering is often portrayed as a relatively cheap and easy fix for climate change. But as researchers take a harder look at the nuts and bolts, they’re finding considerable uncertainties, missing tools, and unbuilt infrastructure.

None of that may be a showstopper, but we’ll need time and money to develop the components necessary to implement even the early stages of a solar geoengineering program. What this research is about, at its core, is not actually launching something, but figuring out what it would take to do so. 

A young San Francisco nonprofit, Reflective, recently worked with scientists in the field to figure out just how much we still don’t know.

The process began by outlining what the organization, which pools money from donors to fund geoengineering studies, describes as a “well-managed, moderate” scenario: In 2035, some nation or group of nations begins a small-scale geoengineering deployment, spraying an equal amount of sulfur dioxide or hydrogen sulfide—gases that should convert into reflective aerosols in the stratosphere—near both the North and South Poles. The initial program would release enough material to reduce temperatures by about 0.1 °C, shaving off a fraction of the roughly 1.4 °C of worldwide warming that’s occurred since the start of the industrial era.

The poles figure prominently in this and other early-stage geoengineering scenarios, for a simple reason: The stratosphere starts as low as seven kilometers there—as opposed to around 18 to 20 kilometers at the equator. That makes it easier to reach, enabling existing aircraft, with some modifications, to carry sizable payloads up there. 

The wrinkle is that the cooling effect would be more pronounced in the northernmost and southernmost latitudes. That’s because, among other complicated mechanisms, higher temperatures in the tropical stratosphere would mostly prevent aerosols released around the poles from drifting toward the equator. So deploying geoengineering in those areas would likely have milder effects on the hotter and poorer nations around the tropics, which are also some of the areas most vulnerable to climate change.

To cool the world evenly—and fairly—you’d eventually want to add flights closer to the equator. Over the following decade or so, under Reflective’s scenario, the program would scale up, shift to novel aircraft flying above the subtropics, and release enough material to achieve global cooling of 0.5 °C. 

Among them: sorting out how hard or expensive it would be to retrofit existing aircraft to carry out the early stages of the project. Deploying at the poles could also require constructing new airports, establishing new shipping lanes or railways to transport supplies, and building facilities that could process raw materials—by, for example, combusting elemental sulfur to produce sulfur dioxide.

We would also need to build more instruments and send them up to the stratosphere aboard balloons, drones, or other aircraft to observe the baseline chemistry, reflectivity, and distribution of compounds there—and to track what changed once new materials were released.

Finally, the main satellites that observe the stratosphere from space are set to go out of commission in the coming years, creating the risk of an “imminent data desert,” as a 2025 paper in the Bulletin of the American Meteorological Society warned. Several new instruments are in development or available for launch, but there could be a gap in observations at a point where we’d want to have a clear picture of the baseline conditions, Reflective notes.

Dakota Gruener, the chief executive officer of the nonprofit, stresses that the organization isn’t advocating the use of solar geoengineering. But she says it’s important for the field to begin addressing engineering uncertainties now because it stress-tests the assumptions in climate models. It helps us determine whether the scenarios explored in silico are feasible in the real world.

It’s also important to do this, she says, because it may take a long time to resolve all these unknowns while the climate grows steadily warmer. “If we aren’t putting adequate attention to them now, we might be caught flat-footed,” Gruener told MIT Technology Review.

A 2024 analysis in the journal Earth’s Future highlighted just how expensive and time-consuming it might be to develop the aircraft and infrastructure required for an initial deployment. The study explored what it would take for a geoengineering program around the poles, capable of reducing temperatures by 2 °C in the northernmost and southernmost parts of the planet, to be up and running by 2040. The conclusion: It could require at least a decade of work and a $35 billion investment. 

Wake Smith, a research fellow at Harvard and lead author of the study, also says that researchers need to move forward with engineering studies now, because the urge to use the technology will likely grow stronger as climate change becomes increasingly catastrophic.

“The risk I worry about is needing it before we understand it and therefore doing it badly,” he says, later adding: “The sooner we get going with it, the better decisions we’ll be able to make a few decades hence in terms of whether to do it, how to do it, when to do it.”

A novel aircraft

The aircraft pictured on Franke’s desk, which is still just a concept, could reach just beyond the threshold of the stratosphere above the tropics when fully loaded. A fleet of 270 of them could disperse about a million metric tons of material per year, enough to ease global surface temperatures by about 0.26 °C. 

The CSEi outsourced the work of designing it to John Langford, a well-known aeronautical engineer and entrepreneur. Langford’s company, Electra.aero, had previously collaborated with the MIT Department of Aeronautics and Astronautics to develop autonomous, solar-powered aircraft that could carry out extended scientific missions in the stratosphere. He is now spinning out a new business, Iris Aero, to produce those planes, which are assembled from a single, continuous wing covered in solar panels and suspended above a tiny fuselage.

Langford expects the solar plane to find its main initial commercial applications in wildfire monitoring and forecasting. But by swapping in a different set of instruments, it could be used to monitor how materials dispersed in the stratosphere might alter conditions there, he says.

The novel aircraft is a variation on the observational plane, with the added space and thrust necessary to carry these materials to the stratosphere and release them. It has a wider wingspan and swaps out those solar panels for a pair of Rolls-Royce AE 3007 engines.

The aircraft would also include a detachable tank that would function something like a trailer on a semi. This would make it possible to load materials between flights and prevent any damage to the plane itself from those materials, some of which are corrosive, Langford says. 

He says he and his team have completed the initial designs and are now doing more detailed engineering and cost analyses. They intend to publish the findings when the effort is complete. 

“We’d love to build a prototype of such an airplane and feel we could do so relatively quickly,” Langford says. “But that all depends on what David’s group wants to do.”

The program

The university saw an opportunity to step up as a leader in a field that wasn’t getting adequate academic attention despite its potential to address the dangers of climate change, says Michael Greenstone, a climate economist and the founding director of the university’s Institute for Climate and Sustainable Growth.

Keith, 62, previously spent nearly 13 years as a professor of applied physics and public policy at Harvard, where he led the establishment of the university’s Solar Geoengineering Research Program. More famously, he strove to carry out what could have been the first solar geoengineering experiment to release material in the stratosphere, known as SCoPEx. But after years of work and multiple delays, the research team finally scrapped the project in early 2024, following mounting criticism from environmental and Indigenous groups and the eventual intervention of the Swedish government.

Keith has long argued that researchers should seriously study geoengineering because it might substantially reduce the dangers of climate change, alleviating death, destruction, and suffering on massive scales.

He says that the overarching goal of the Chicago initiative is to expand the field by bringing together “enough independent professors and other research professionals” to “build a community around climate engineering as a broad field of inquiry.”

“Solar geoengineering certainly has complex and potentially dangerous political consequences, but so do a host of other emerging ideas and technologies.”

David Keith, geoengineering researcher

The CSEi researchers are now exploring nearly every engineering challenge that Reflective highlighted in its analysis. In addition to the work on novel aircraft and in situ observations, the group is designing small “cube” satellites with optical sensors optimized for observing the stratosphere. It is also studying which materials might prove most practical to ship to the stratosphere and how best to release them.

The goal is “producing public information which can be independently assessed, critically assessed, so policymakers can understand more about what’s possible and not,” Keith says.

Normalizing a dangerous idea

The debate around solar geoengineering is quickly moving beyond the academic and theoretical realm. A handful of startups, some more serious than others, have begun testing technologies that could one day be used to cool the planet. 

Yet to critics, solar geoengineering is the peak of techno-solutionism, affixing a high-tech Band-Aid to a global crisis caused by earlier technologies instead of addressing the root cause. Further, they argue that there’s no way to deploy or govern it in a globally equitable way, because any use of it will prove more advantageous to some regions than others. 

Even if solar geoengineering succeeded in reducing the average global temperature by 1 °C or so, that would mean very different things in different regions.

It could keep farmers prosperous and cities safe across, say, much of the US and the world’s temperate zones. But the lower temperature might be too cool for Russia to boost its agricultural productivity, while it might still be too hot for subsistence farming in northern Africa. 

Some studies also suggest that high levels of solar geoengineering could create new dangers in some regions, potentially altering monsoon rains, decreasing agricultural output, shifting the range of infectious diseases, and more. 

These complications raise a long list of thorny and divisive ethical questions. Even if solar geoengineering produced better conditions across most of the planet relative to a world with unchecked climate change, would it still be acceptable if it unleashed deadly famines or floods in a few regions? What kind of global consensus should be required to decide it’s okay to deploy it? And how should we determine where to set the planet’s temperature—and when, if ever, to shut the technology off?

Stephens argues that the answers, like so much else in the world, will come down to wealth and power. Countries, corporations, or even wealthy individuals with the resources to deploy such a system would have every incentive to tune it for their optimal benefit, no matter what it might mean for others. 

“It will be certain people who have a lot of wealth and power deciding when and how, and who should benefit and who will get screwed,” she says. “That’s the fundamental reason I think any advance in this technology is so dangerous.”

Duncan McLaren, an environmental researcher and political scientist, argues that the shift into practical engineering studies demands more oversight of the research field.  

For many critics of outdoor experiments like SCoPEx, he explains, the major concern wasn’t the environmental or safety risks, which were minimal; the issue was the normalization of a concept that could reduce pressures to cut greenhouse-­gas emissions. 

He says that any advance in research—whether it’s on paper, in the lab, or in the stratosphere—raises a similar risk: undermining progress on climate action by allowing the fossil-fuel sector and other business interests to say there’s an easier solution in development that doesn’t require overhauling our energy systems. A policy paper that the Texas Conservative Coalition Research Institute released in March advanced this very argument, citing the far lower costs of solar geoengineering relative to the “staggering costs” of a “forced transition.” 

Given this so-called moral hazard risk, design and engineering work should demand the same level of scientific supervision that outdoor experiments do, including ethical review, risk assessments, and public engagement, McLaren says.

“It ought to be more onerous,” he says. “There ought to be more barriers to researchers saying they want to do this.”

“The next ethical step”

Keith pushes back forcefully on that assertion, condemning as “profoundly illiberal” the idea that we should regulate open academic research posing no physical risks. 

“Solar geoengineering certainly has complex and potentially dangerous political consequences, but so do a host of other emerging ideas and technologies,” he said in an email. “The best chance to manage these challenges is to debate them openly and freely.”

Keith is all for keeping solar geoengineering technology in the public domain, and he agrees that the first line of climate defense must be rapid and deep reduction of greenhouse-gas emissions. But the world has made little progress in cutting climate pollution, carbon dioxide can persist for thousands of years in the atmosphere, and the planet is heating up fast. So, he argues, we may need to pursue other measures to temper the growing threats.

The bar for restricting research in this field should be “very high,” he says, given the potential promise of the technology. 

After visiting flood-devastated villages in Bangladesh, Keith underscored this point in an interview with the director of Plan C for Civilization, a recent documentary that profiles his work. “I think people have to take the next ethical step,” he said. “Because if you are really going to withhold access to and knowledge of a technology that could potentially save enormous numbers of lives—real lives, people we’ve met in the last few days—you’ve got to be very confident that that technology is going to be misused.”

The particles

Mingyi Wang, an assistant professor at the University of Chicago, leads me down the hall to a square, white lab room in the Henry Hinds Laboratory for Geophysical Sciences.

He pulls open the doors to a gray Haier biomedical freezer just inside the entrance, revealing a transparent flow tube hanging vertically and tapering at the bottom.

It’s a miniature stratosphere, chilled below −50 °C and filled with the same mix  of oxygen, nitrogen, and other air molecules you’d find 20 or so kilometers above us. A series of Teflon and stainless-­steel tubes run into the vessel, allowing Wang and his team to add various gases or particles and observe how they react.

Wang is an atmospheric scientist who studies how aerosols form, and he is now exploring what materials might be the most effective for reducing temperatures. 

Most modeling experiments focusing on solar geoengineering explore the impact of adding sulfuric acid to the stratosphere, because that’s what ultimately ends up there after a volcanic blast. 

But it would be costly and complicated to simply haul sulfuric acid up there and release it, because it’s heavy and sticky. So Wang and his team are conducting experiments in that chilly flow tube to determine what substances, including precursors to the acid, might do the best job of producing aerosols of the ideal size for reflecting away sunlight—and how best to prevent the materials from simply clumping together with existing particles and falling out of the stratosphere.

Wang, whom Keith refers to as a “young star,” has arrived at a novel solution to this problem, though he’s not ready to share the full details yet. He and his team are feeding the findings from their experiments into computer simulations of stratospheric plumes that they’ve developed. These, in turn, can be plugged into large-scale climate models to improve their simulation of smaller-scale effects—and thus enhance our understanding of stratospheric chemistry.

Wang says that it’s important to do this detailed research because until now, climate models simply assumed you’d wind up with the right aerosols of the right size. 

“Scientifically, we may understand it reasonably well, but on the engineering perspective—do we really know how to do it right?” he asks. “That’s a big question.” 

What’s next

As I began reporting on CSEi, I assumed that some of the engineering and design work would lead to new proposals for stratospheric experiments, picking up from where SCoPEx left off. 

Keith, though, insists he has no interest in reliving that experience, given the weight the experiment took on as the focal point for a broader societal debate over solar geoengineering. He doesn’t see any of the other “practical engineering” work at the initiative leading toward field experiments either, at least at this stage.

Much of the work, in fact, is focused on a step beyond that: exploring what it would take to start a geoengineering campaign, if a nation or group of them eventually decides to. Franke notes that we already have balloons and other aircraft that could get to the lower bounds of the stratosphere to release an experimental amount of, say, sulfur dioxide. 

“I think that this field needs to stop being so ashamed of using the ‘deployment’ word,” he says. 

After three years of record-­breaking heat, this one is set to be yet another scorcher. Air-conditioning? Not going anywhere. The International Energy Agency projects that the number of AC units will triple by 2050.

That’s good for health—one Lancet study estimated that AC prevented nearly 200,000 premature deaths in 2019 alone—but bad for the planet. Artificial chill already accounts for 7% of global electricity use and 3% of greenhouse-gas emissions, and if improperly disposed of, the units can leak refrigerants with more global-­warming potential than carbon dioxide.

Feeling the heat, a number of scientists and startups are hoping to amp up solid-­state cooling, which is currently used at a small scale for things like mini fridges, EV batteries, and some high-end gaming computers. Traditional ACs transfer heat by using a compressor and a fan to circulate a refrigerant and turn it from liquid to gas.

Solid-state systems, on the other hand, move heat through conductive materials like gadolinium and bismuth telluride—which could theoretically cool spaces and surfaces with fewer messy side effects. 

The catch is whether they can match the efficiency of conventional AC. “One of the key questions that remain is why are the solid-state coolers not as efficient as typical thermodynamic cycles?” says Pramod Reddy, a professor of mechanical engineering at the University of Michigan who studies heat transfer. 

Research and pilot programs are underway to test a range of approaches. Brooklyn-based Mimic Systems uses thermo­electric cooling, which passes a current through semiconductive materials to shift heat from one side to another. Its room-scale climate control system is being piloted in an apartment in Vancouver.

The German company Magnotherm is set to test its system, which relies on a magneto­caloric setup that transfers heat by magnetizing and demagnetizing materials, in a chain of supermarkets. A team in Hong Kong has announced that its elastocaloric device, whose material heats and cools as it expands and contracts, can dip below 0 °C. And the UK’s Barocal is betting on barocaloric systems, which change temperature in response to shifts in pressure. 

But experts, especially in thermoelectrics, have doubts about how well any solid-­state scheme can compete. For most modern HVAC systems, the coefficient of performance (COP) is 3, explains Jeff Snyder, a professor at Northwestern University who studies electrical and thermal conductivity. That essentially means the system moves three units of heat for every unit of energy that goes into it.

Thermoelectrics in particular tend to have a much lower performance at high levels of temperature change, Snyder says, which means they’re best suited for niche uses such as cooling the back of a car seat. 

Efficiency, however, isn’t everything, argues Lindsay Rasmussen, a manager at the Rocky Mountain Institute’s climate tech accelerator Third Derivative, which supports both Magnotherm and Mimic. In the US, most ACs currently in use employ a refrigerant called R410A, which has a global-­warming potential more than 2,000 times that of carbon dioxide. Plus, their moving parts can make them less durable, especially compared with a solid-state model that’s less mechanically complex.

Still, a dearth of units makes it hard to answer the efficiency question. To understand how well alternatives work, says Rasmussen, researchers need to compare their long-term energy consumption with that of conventional models instead of simply looking at COP. Mimic claims, for example, that its room-scale model should match the draw of a typical AC unit over the course of a year. Elastocaloric and barocaloric systems also have promise, Rasmussen adds, but room-scale prototypes are probably two to three years away. 

In the end, the likelihood that solid-state cooling could replace compressor-based AC is slim. But as the planet warms and places like India install tens of millions of new AC units over the next decade, supplanting even a small number could make a dent. “If [solid-state] could take over even a 5% market share,” Rasmussen says, “that is a really large potential impact.” 

Sara Kiley Watson is a science journalist specializing in climate and sustainability. She’s based in The Hague.

In 2018, after nearly two decades working in Big Pharma, chemist Tim Cernak was ready to put his skills to a new use. 

For Merck, he’d developed precision therapies for cancer, HIV, and diabetes that could target disease while minimizing harm to healthy cells. But as a lifelong nature lover, he was increasingly concerned about the health of ecosystems and wondered whether his expertise could transfer. Animals, he learned, are often treated with pharmaceuticals formulated for humans, which affect them like old-school cancer drugs: Though intended to kill abnormal cells, they’re indiscriminate in the harm they cause. For instance, the standard of care for frogs infected with a deadly skin infection is itraconazole, an antifungal that is often lethal for the amphibian.

Cernak imagines a world where “the patient was always meant to be a frog in the first place, from the beginning to the end.” Now an associate professor at the University of Michigan, he’s worked on all types of creatures, from a Gila monster with a parasite to bald eagles with avian flu. Here’s what it takes to treat nature’s patients.

Experience with protein-modeling software 

Developing any type of drug is extremely expensive, failure-prone, and slow-going. But AI can speed up the entire drug-­design workflow, says Cernak. Google DeepMind’s AlphaFold model allows him to visualize a mutant protein’s three-­dimensional structure on a screen—rather than growing it on a plate, the traditional methodology—and then quickly generate possible new drugs that would latch onto that structure. The next step is to run a series of reactions and see which potential drugs may be effective; with the help of robots in the lab, he can speed through as many as 1,500 per day. 

Curiosity about creatures of all sizes

Cernak isn’t selective with his patients. For example, he worked on a treatment for loggerhead sea turtles after he was shocked to learn that the iconic species suffered from contagious tumors. He feels especially drawn to creatures that have helped humans, like the Gila monster, whose hormones have informed popular weight-loss drugs like Ozempic. And it’s not just animals; he’s also developing a precision insecticide to treat hemlock trees under attack from invasive species. 

A pioneering spirit

Cernak refers to this new discipline as “conservation chemistry.” It’s a combination of words with a loaded history, from DDT decimating US bald eagle populations in the 1960s, to cow painkillers killing millions of Indian vultures in the ’90s. He recognizes the risks, but Cernak feels that excluding chemists from conservation is a missed opportunity. 

“I’m just sick of looking at the chemical tools that are used in the conservation space, and they’re not cutting-edge,” he says. “It’s like, how do you have this super high-tech engine over here for making human medicines, while we’re living through a mass extinction?” 

Anna Gibbs is a journalist who covers the intersection between science and society.

It’s a tale of two nuclear industries.

In China, large reactors are coming together at a stunning pace. The country has nearly doubled its nuclear fleet since 2016, reaching nearly 60 gigawatts of total power capacity. The new facilities are nearly all gigawatt-scale pressurized-water reactors.

Meanwhile, the US has built just two reactors in that time—Unit 3 and Unit 4 at Plant Vogtle in Georgia. Smaller reactors are attracting a lot of excitement and investment, though. A microreactor developer just saw its reactor reach criticality in a new Department of Energy pilot program.

The world is racing to meet rising electricity demand, and many countries are interested in energy sources, like nuclear power, that don’t come with greenhouse-gas emissions. The key question: Which of these strategies will really pay off in terms of getting electrons on the grid quickly?  

Today, the US and France are known as leaders in the nuclear industry. The US has the world’s largest fleet, with France coming in second. France is heavily dependent on nuclear for its grid—about two-thirds of the country’s power comes from nuclear reactors.

But they have hardly added any new reactors to their fleets in recent years. The US can point only to Vogtle, and France connected its latest reactor to the grid in December 2024—the first in over 20 years. 

It’s incredibly difficult to build the massive projects that dominate the nuclear industry today. Up-front investment can run well into the billions, so investors need to wait decades to break even. Designs are complex and can often change during the regulatory process, tacking on cost and time. 

Many are hoping that the key to turning things around in these countries could be smaller reactors.

The idea is that shrinking the footprint of a reactor cuts down the initial investment needed to prove out the new technology. The reactors could even be put together in a factory rather than being built on-site, allowing for a lower price over time.

These smaller reactors are the target of tons of interest and investment in the US, including a new Department of Energy pilot program. The department set a goal last year of having three test reactors reach criticality by July 4, 2026, the nation’s 250th anniversary. (Criticality is the point at which a reactor achieves a self-sustaining chain reaction that can release energy.)

Last week, California-based Antares hit the milestone with its Mark-0 reactor. 

The company plans to eventually build microreactors, designed to produce between 100 kilowatts and 1 megawatt of electricity (large reactors on the grid today are at least 1,000 times that size). The core design is a sodium-cooled reactor, and it uses TRISO fuel, self-contained graphite-coated spheres of a more concentrated fuel than what most reactors use today. 

But there is still a long way to go before it can actually produce power—the Mark-0 doesn’t have any power conversion or heat removal systems. The company plans to produce electricity in late 2027 and deploy in the field by 2028, CEO Jordan Bramble told the Associated Press.

The private sector is interested—and invested—too. Big Tech companies are throwing money at new reactors they hope can help power data centers. 

But look to the other side of the globe, and others are sticking with the established blueprint: China is absolutely churning out large nuclear reactors. Construction started on six new reactors there in 2025, and two more got underway in the first five months of 2026. The country is on course to overtake both the US and the European Union in installed nuclear capacity by 2030.

The speed here is staggering. As of 2024, the average time to build a new reactor in China came in at between five and seven years. The global average is about nine years, and the two most recent reactors in the US took about 15 years.

One key to this speed is standardization: China has set up a uniform project management system to design, license, and build new reactors. They’re built in batches of six or more to take advantage of economies of scale.

It’s one of the ideas meant to give the edge to smaller reactors, but China is working to realize the same benefits for larger projects. A huge amount of government investment is certainly helping.

Larger reactors generally provide more electricity to the grid for a lower price, a key consideration in view of China’s steeply increasing electricity demand. While smaller reactors require less up-front investment than larger ones because of their size, they’ll actually be more expensive per unit of electricity produced. 

That’s not to say China is exclusively focused on big reactors: the country is also expected to see its first operational small modular reactor, the Linglong-1, start sending power to the grid this year.

But looking ahead, it’ll be interesting to see if smaller reactors can help the West keep building new nuclear power. At the moment, with China’s quick progress, it’s looking as if bigger might just be better. 

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Would you take a payment to ramp down your electricity use? Would it change anything if you were doing so to help power a local data center?

Google just signed a new deal to help pay for a virtual power plant (VPP) in the largest power grid in the US. The agreement is with Voltus, a leading VPP and distributed energy resources platform.

Voltus will set up the virtual power plant, grouping together devices like electric vehicles and smart thermostats. It’ll pay customers to participate, and the company will dial back power or use the stored energy during times when the grid is stressed. Google will foot the bill for setting it up, and the extra capacity generated by the project will help run its data centers in the region.

This is one of the most concrete examples so far of a tech giant using a VPP to help meet energy demand for data centers. But there are still some lingering questions about just how far this sort of program can go, and what the limits are.

Last year, it felt as if everyone was talking about data center flexibility. A high-profile study from Duke University found that if data centers agreed to decrease their energy demand for roughly 40 hours per year, a whole bunch of them (about 100 gigawatts’ worth) could come online without making new power plants or transmission equipment necessary.

The underlying reason is that our power grid is designed not for our average energy use, but for the absolute maximum: the brutally hot July evening when everyone is blasting their air conditioners, watching Love Island, and microwaving popcorn. If a data center is willing to refrain from pulling so much power during those high-stress times, the grid can happily support it the rest of the year.

One lingering question here is about incentives: How would you get data centers to agree to this? After all, they might not have a very flexible load, especially now that AI use is more widespread—training a model can easily be delayed or shifted, but customer demand is more immediate. Giving up computing capacity could mean losing revenue.

Regulation is one approach that could work here. One proposal in the US would allow new data centers to come online years sooner if they agree to lower demand when the grid is nearing its max.  And a new Texas law requires large users to switch to backup power or curtail their demand in emergency situations.

Another approach is for data center operators to pay for other people to be flexible.

Voltus announced a new program in September that allows data centers to finance flexibility on their local grid. The company calls it “Bring your own capacity.” Google is now the first named customer taking advantage of this program.

In the new agreement, Voltus will pay people who agree to participate in the virtual power plant. The plant will be part of PJM, the grid that covers much of the US East Coast. The company says it will be able to aggregate up to 100 megawatts of distributed energy resources each year. The plant should be operational in 2027, according to Voltus.

This isn’t Google’s first foray into flexibility; the company has agreements with utilities across the US to limit or shift its own energy demand, which can help free up grid capacity. As the company pointed out in a blog post earlier this year, though, there are limits on how flexible a data center can be, and not every facility will be able to ramp down its power demand.

“There is no one solution for expanding grid capacity and we’re continuing to explore all options, including the many avenues for load flexibility,” said Michael Terrell, Google’s global head of advanced energy, in an emailed statement in response to written questions.

Once again, I’m wondering about incentives here. These companies are asking homes and businesses to be flexible. Will they agree?

A recent study in California looked at local people’s willingness to participate in managed electric-vehicle charging. Essentially, the program pays people to give up control of when they charge their EVs. This is another way to help smooth out electricity demand and ease the burden on the grid.

The problem? Not many people signed up. With no economic incentive, only 1% of EV owners enrolled in managed charging. At $40 per month (about 15% of their power bill), only 4.6% did.

This is a different situation and a different region from the one in which Google is working with Voltus. (It’s worth noting that the companies aren’t sharing how much they plan to pay the participants, which will obviously be a big determinant in participation for this kind of project.) 

But this study shows that even with money on the table, people may not always jump at the chance to cede control of their electricity demand. And it certainly feels relevant that about 70% of Americans oppose AI data centers in their area, according to recent Gallup polling. 

Being flexible sounds like a great idea in theory, and these financed VPPs could provide an immediate route to meeting energy demand. But as we move from idea to implementation, it’ll be interesting to see whether trial runs work as intended.  

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here. 

Researchers say they’ve found a new way to extract lithium, a crucial metal used in the lithium-ion batteries that power electric vehicles and energy storage arrays. This new technique could be more environmentally friendly and cheaper than existing ones. 

The research was published today in Science, and a startup called Rock Zero is working to commercialize the process.

“At scale, we believe this will be the lowest-cost way of sourcing lithium in the world,” says Yet-Ming Chiang, one of the study authors, who is an MIT professor and a serial entrepreneur behind climate tech companies including Form Energy and Addis Energy.

The most economical way to get lithium currently is to extract it from brine, salty water that’s pulled the metal out of rock over the course of millennia. But this technique is geographically limited and currently requires vast tracts of land for massive evaporation pools. The more common tactic is hard-rock mining, where large bodies of ore are blasted apart, cooked at high temperatures, and processed using dangerous chemicals.

The researchers’ new method uses a weak acid to dissolve typically nonreactive silicate minerals. That frees not only the lithium but also other useful materials, including alumina and silica.

The origin story for this research, and the resulting company, came from another startup founded by Chiang, Sublime Systems, which makes cement using electrochemistry.

The team was trying to find a source of highly reactive silica in order to form stronger cement. One way to make reactive materials, which can bond easily with other materials, is to take a nonreactive material, dissolve it, and then allow it to become solid in a more reactive form. It’s not impossible to dissolve silicates, but the best-known way is to use hydrofluoric acid, an extremely dangerous chemical. Other fluorine-containing chemicals are candidates too, but some will produce hydrofluoric acid as a side product during reactions. 

Chiang drew inspiration from a previous home renovation project involving glass, which is made of silica. “I was remodeling a shower in Framingham, Massachusetts, about 25 years ago,” he says. “So when we started this project, I remembered that glass etching cream and thought, ‘What’s in that?’” 

The glass etching cream he remembered, which can be found on shelves at any craft or home improvement store, uses ammonium fluoride, a weak acid. And the MIT researchers discovered that in the right conditions, it can effectively dissolve silicate minerals without producing hydrofluoric acid in the process.

This chemistry could be useful for any silicate minerals—and there are a lot of them. But spodumene, the mineral that’s often mined for lithium, became a prime first target. (Chiang says a suggestion from Doug Wicks, one of the company’s advisors and a former ARPA-E official, pointed the team in spodumene’s direction.)

Today, a key step in processing spodumene ore is to roast it in a kiln at super-high temperatures. This causes a phase transformation, essentially puffing up the material and making the lithium more accessible.

By avoiding the need to reach these temperatures, you could save on energy costs and potentially reduce carbon emissions as well, says Camden Hunt, one of the authors of the study and the CEO and cofounder of Rock Zero.

Avoiding the kiln could also unlock the ability to use some ores that can’t be roasted properly, Hunt adds. Ore that contains too much iron won’t go through the phase change correctly, instead melting and turning into a glassy material.

The new process relies on simple stirred plastic tanks and takes place at temperatures up to about 95 °C (200 °F). The ammonium fluoride dissolves the silicates, which in earlier experiments allowed nearly all of the lithium inside the spodumene ore to be extracted within a couple of days. The researchers have since cut this time to under 12 hours, says Benjamin Mowbray, first author of the study and the CTO and cofounder of Rock Zero.  

The products (after some additional steps to clean them up) are lithium carbonate, which can be used to make batteries; alumina, which can go into a smelter to make aluminum; and cementitious silica, which can be added into concrete. And the acid can be reused in the same loop.

Chiang calls this “nose-to-tail” mining—using every part of the ore provided, like eating every part of a butchered animal.

The researchers are currently working to scale and optimize the process. The tanks in the lab in Cambridge, Massachusetts can handle three kilograms of spodumene concentrate in each batch. 

They have also estimated the cost of this process once fully scaled up. Assuming that the ammonium fluoride can be recycled at a high level, they should be able to extract lithium for less than $6,000 per metric ton. (They’ve identified a potential cheap industrial source of the acid as well, as an alternative to recycling it.) 

The total cost is projected to be lower than that of other processes used to extract lithium from hard-rock ore today, and it could be competitive with brine.

The team has designed a pilot plant and is looking for space to build it. The plan is to have construction done by the end of 2026 and start operating the facility in 2027. Talks are underway with potential partners in the mining industry.

One difficulty for new players in lithium extraction is the volatility of the market: Prices have seen huge swings in recent years, from a peak in 2022 to lows in late 2024 and a slow climb starting in early 2026. 

Rising prices might benefit new players like Rock Zero, but there are many projects that could come online if prices continue to rise, and that could bring the market right back down, says Simon Jowitt, chair of exploration geology at the University of Nevada, Reno. “People are waiting to see what happens with the lithium price,” he says. “It’s a crowded market, and there’s some big players out there.”

And even though batteries are driving up demand for lithium, the market is still relatively small, Jowitt adds: “That means it’s going to be volatile.” New lithium extraction technologies like Rock Zero’s will have to compete with methods used by existing giants, and there’s also the potential that technological alternatives, like sodium-ion batteries that don’t need lithium, could make the market more difficult to navigate, Jowitt says. He also thinks some of the company’s economic estimates could be optimistic.

For its part, Rock Zero’s team hopes not only to scale this technology for lithium, but to use it for other minerals in the future. As Mowbray says, “The Earth’s crust is made of silicates.”

This year, there’s been a wave of notable energy companies going public via IPO in the US.

The solar and battery company Solv Energy went public in February, to the tune of $6 billion. X-energy, which is building small modular nuclear reactors, did the same in April, and its stocks surged on its first day of trading to hit a $11.5 billion market cap. Most recently, the geothermal company Fervo Energy went public in mid-May, and its market cap is now about $12.4 billion.

Those are all success stories in the IPO world. And it certainly doesn’t feel like a coincidence that all these companies are racing to provide electricity in an era of rising demand (partly due to data centers). Let’s take a look at how these firms are doing, what this moment says about the grid, and what’s coming next. 

Let’s start with Fervo Energy, a company we’ve covered a lot over the years that’s working to develop enhanced geothermal energy. (We included it on our 2025 list of Climate Tech Companies to Watch.) While conventional geothermal requires finding specific spots with hot rock, water, and fractures to support a power plant, Fervo essentially uses fracking techniques to create the necessary conditions.

The company was founded in 2017, and it raised about $1.5 billion from investors over the years before its IPO.

Fervo’s first commercial project, Cape Station in Utah, is expected to have a capacity of about 500 megawatts. The first unit is set to start generating power for customers by October and the next two units by January 2027.

The new funding from the IPO could help the company scale. Fervo currently has over 600 megawatts’ worth of binding power purchase agreements. And it has leases for land that could together generate more than 40 gigawatts of electricity. (As of 2024, the entire US geothermal fleet had a capacity of just 4 gigawatts.)

The company also has an eye on cutting construction and drilling costs—its Cape Station plant is expected to cost about $7 per kilowatt, which is cheaper than new nuclear power plants but over twice the expense of building a new natural-gas plant in the US. 

X-energy also aims to provide reliable clean power: it’s part of the wave of next-generation nuclear companies working on small modular reactors. The company is building high-temperature gas-cooled reactors, which flow helium over self-contained pebbles of nuclear fuel. These reactors will each generate 80 megawatts of electricity, less than one-tenth the output of larger ones like Unit 4 at Plant Vogtle in Georgia, the most recent addition to the commercial nuclear fleet in the US.  

X-energy also saw its IPO go well, and prices surged in trading after the initial offering. One interesting tidbit here—the company had previously planned to go public in 2023 but decided against it because of difficult market conditions.

The company is still years away from demonstrating its technology in a commercial project. 

You may recall a story I wrote last year about its effort to build nuclear reactors at the site of a Dow Chemical plant in Texas. The company recently received a key environmental approval for that project, though it’s still waiting for the final green light from the Nuclear Regulatory Commission to start construction.

Finally, Solv Energy builds solar and energy storage projects, mostly for utilities and independent power producers. Solar and batteries are some of the cheapest and easiest technologies to add to the grid, so this one could get a lot of capacity online, quickly. The company already has 21 gigawatts’ worth of projects operational across 35 states.

Many companies in the energy sector are pinning their hopes on the rapid growth in data center construction and operation. The AI boom has transformed the energy landscape, pushing electricity demand higher in a country where it’s been relatively flat for the last decade or so. Solv Energy mentioned data centers over a dozen times in documents filed with the Securities and Exchange Commission before its IPO. 

And Fervo and X-energy are particularly connected to the tech giants driving AI. Google has been a longtime investor in Fervo and also pioneered what it calls its clean transition tariff with the company. Amazon is a client of X-energy as well as an investor; it reportedly owns close to 20% of the company.

Fervo and X-energy are also in industries that occupy a political sweet spot. President Trump and his administration have gone after wind power and other renewables, cutting off existing support and slowing approvals for new projects. Meanwhile, geothermal and particularly nuclear power have kept favor with the federal government and enjoyed continued tax credits and grant funding.

If a few big leaders cash through these IPOs, it could help investors feel more confident about supporting the energy sector, even if that money is concentrated in later-stage ventures like these rather than earlier-stage companies. 

We could see other firms, particularly in nuclear and geothermal, attempt a similar route in the year ahead.

A key thing to watch here will be whether Fervo and X-energy in particular can succeed in scaling up and deploying their technology. If either of these companies stumbles or misses a timeline, it could have ripple effects for those hoping to follow in these very lucrative footsteps. 

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.