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Practically every week brings a flood of climate tech funding news and announcements — startups raising a new round, a venture capital firm closing a fresh fund, and big projects hitting (and missing) milestones. Going forward, I’ll close out each week with a roundup of some of the biggest stories that I didn’t get a chance to cover in full.
This week, we’ve got money for electric ships, next-gen geothermal, and residential electrification in Europe. Yay!
Many say battery-powered cargo ships will never make sense — that batteries are too heavy, too bulky, and would take up too much valuable space. Fleetzero says it can make it work. Last Friday, the electric shipping startup raised a $43 million Series A round led by Obvious Ventures, with participation from other firms including Maersk Growth, the shipping giant’s corporate venture arm, and Breakthrough Energy Ventures. The funding will support production of the company’s hybrid and electric propulsion systems, as well as new manufacturing and R&D operations in Houston.
Ships’ bunker fuel is extremely polluting. It accounts for roughly 3% of global CO2 emissions and dirties the air with other pollutants such as sulfur and nitrogen oxides. Most players in the shipping decarbonization space want to shift to liquid fuels such as e-ammonia or e-methanol — a move that would require mulit-million-dollar engine overhauls and retrofits. Fleetzero says that battery electrification will prove to be cheaper and simpler. The company is building batteries large enough to hybridize — and potentially one day fully electrify — large container ships.
As Fleetzero’s CEO and co-founder Steven Henderson told my colleague Robinson Meyer on a 2024 episode of Heatmap’s Shift Key podcast, batteries are a relatively simple maritime decarbonization solution because “you can use existing infrastructure and build on it. You don’t need a new fundamental technology to do this.” And while the company has yet to provide any cost estimates for electrifying commercial shipping, as Henderson put it, “the numbers to do this are not outside the realm of possibility.”
The next-generation geothermal startup Sage Geosystems announced on Wednesday that it raised a $97 million Series B round, co-led by the renewable energy company Ormat Technologies and the growth equity firm Carbon Direct Capital. This came atop a hot week for geothermal overall. As I wrote already, the artificial intelligence-powered geothermal developer Zanskar announced a $115 million Series C round for its pursuit of AI-driven conventional geothermal, while Axios reported that the geothermal unicorn Fervo Energy has filed for an IPO.
Like Fervo, Sage uses drilling technology adapted from the oil and gas industry to create its own artificial reservoirs in hot, dry rock. The startup then pumps these fractures full of water, where it absorbs heat from the surrounding rocks before being brought to the surface as steam that’s used to generate electricity. Sage’s CEO, Cindy Taff — a former Shell executive — told Bloomberg that this latest investment will accelerate the company’s project timeline by a full year or two, allowing it to put power on Nevada’s grid sometime in 2027.
This latest funding follows Sage’s strategic partnership with Ormat, announced last year, and could help the startup make good on its agreement with Meta to deliver up to 150 megawatts of clean electricity for the tech giant’s data centers starting in 2027.
Berlin-based startup Cloover — which helps Europeans finance home electrification upgrades — announced a $22 million Series A round on Wednesday, alongside a $1.2 billion debt facility from an unnamed “leading European bank” that it can draw on. The company, which describes itself as both the “operating system for energy independence” and the “Shopify of Energy,” aims to help homeowners ditch fossil fuels by facilitating loans to cover the upfront cost of, say, buying and installing heat pumps, rooftop solar, or home batteries — something traditional banks struggle to finance.
Cloover’s fintech platform allows home energy installers to manage complex projects while offering loans for green upgrades to customers at the point of sale. The software’s AI-driven credit underwriting evaluates not just a customer’s credit score, but also the projected energy savings and performance of the upgrade itself, helping align the price and terms of borrowing with the anticipated economic value of the asset.
Forbes reports that Cloover has already financed roughly 2,500 home energy installations. The company says it’s profitable, generating nearly $100 million in sales last year. With this new funding, the startup plans to expand across Europe and is projecting $500 million in sales this year, anticipating an explosion in demand for distributed energy resources.
One of the oldest players in the race to commercialize fusion energy, General Fusion, has been candid about its recent funding struggles, laying off 25% of its staff last spring while publicly pleading for more cash. This Thursday, it announced a lifeline: a SPAC merger that will provide the company with up to $335 million, if all goes according to plan. Read more about the deal in our Heatmap AM newsletter.
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The spinoff of Lawrence Livermore National Lab has a new 10-point plan to get onto the grid by the 2030s.
One of fusion energy’s newest startups, Inertia Enterprises, is betting that the fastest route to commercial fusion runs through one of the field’s oldest ideas. The company, which raised a $450 million Series A earlier this year, plans to build a power plant based on the laser-driven fusion system pioneered at Lawrence Livermore National Laboratory’s — the only tech yet to have produced more energy from a fusion reaction than it took to initiate it. Now, Inertia has shared its commercialization roadmap exclusively with Heatmap, detailing the 10 near-term capabilities it must demonstrate before this landmark experiment can become a grid-scale power plant by the mid-2030s.
The roadmap offers a route from the national lab’s impressive but commercially impractical fusion demonstrations to an economical power plant capable of producing electricity for the grid. At its core are a set of milestones — mostly aimed at developing cheap, mass-manufacturable components — that Inertia says it must clear before those individual systems can be integrated into a working plant. This road is not necessarily linear, however, as various teams will likely be working on many of these goals simultaneously.
At least the physics of Inertia’s approach are already proven, the startup’s CEO Jeff Lawson told me, pointing to the fusion experiments at Lawrence Livermore’s National Ignition Facility as a proof-of-concept. The lab’s demonstration of net energy gain caps more than six decades and $30 billion (in 2026 dollars) of U.S. fusion research. The remaining challenges, he argued, are all engineering-related, requiring “elbow grease, hard work, and smart people” rather than breakthroughs in fusion science.
"It seems to us like a startup or a commercial company of any variety should be focused on commercializing a proven scientific result, as opposed to actually trying to demonstrate the basic science to begin with," Lawson told me. Basic science, he argues, is better left to national labs and universities, where researchers can pursue "unbounded problems" that don’t align with the expectations and timelines of venture-backed startups.
Indeed, no fusion startup has yet achieved scientific breakeven, the milestone Lawrence Livermore first hit in 2022, and has since repeated numerous times. But leading players such as Commonwealth Fusion Systems and Helion Energy maintain that it’s only a matter of time before they validate the physics behind their own reactor designs, which they claim will be highly cost-competitive.
Lawson, on the other hand, readily acknowledged that Lawrence Livermore’s tech is uneconomical in its current form. His bet is simply that the more predictable path to a commercial reactor is to drive down the cost of the lab’s validated fusion approach, known as inertial confinement. This system relies on high-powered lasers firing at a millimeter-scale pellet of fusion fuel, compressing it to extreme temperatures and pressures until the atoms fuse. Today, the National Ignition Facility makes each individual fusion target by hand, a workable solution given that it only uses about a dozen per year.
That production model, however, isn’t remotely plausible for a grid-scale power plant. Because each fusion reaction lasts just a fraction of a billionth of a second, a commercial facility must fire its lasers at a fresh target about 10 times per second to generate continuous electricity — requiring the production of hundreds of millions of targets each year.
Scaling production to roughly a million pellets per day and making them inexpensive enough for commercial operation without compromising the strength or precision required for fusion ignition is central to Inertia’s roadmap. That includes goals five, seven, eight and nine — industrializing the manufacturing of the carbon shells that hold the fusion fuel, making the thin films that hold those carbon shells both durable and cheap, scaling up and automating fusion target assembly, and speeding up how fast targets are filled with the requisite deuterium-tritium fuel.
The other central focus of the roadmap is the laser system, which will ultimately consist of 1,000 individual units operating in concert to compress and heat the fusion fuel. Key priorities include reducing the system’s cost (goal two), dramatically increasing its firing cadence (goal three), and bolstering its durability to withstand high-intensity operations (goal four). Goal six also complements these efforts, calling for the development of a control system capable of tracking moving fusion targets to precisely align each laser shot.
Goals one and 10 bookend the journey with some broader milestones. The first focuses on increasing the fusion target’s energy gain — the ratio of fusion energy produced to laser energy delivered — to more than 25 times ignition. Today, the National Ignition Facility’s best-performing laser shot has yielded a gain of just over four times what it took to start the reaction. Goal 10 then zooms out to the ultimate objective: integrating all these technologies into a commercially viable power plant that can deliver either electricity or industrial heat to end customers.
To reach that point, Inertia has embarked on an industrial engineering hiring spree, recruiting folks with experience taking complex hardware systems from prototype to mass production, “not unlike the processes that are used in the semiconductor or consumer electronics world,” Lawson explained. The company has been making progress on its component development goals since the beginning of the year, he told me, and expects to announce the successful demonstration of a few of these milestones in the coming months. Lawson ultimately expects Inertia to complete the core components of its laser and target manufacturing systems by the middle of next year.
The team will spend the next two to three years integrating these individual pieces into two fully operational subsystems, a prototype laser system and a target manufacturing line. Around 2030, the company will begin combining those subsystems into a first-of-a-kind fusion power plant, which will also serve as the proving ground for the target chamber, tritium fuel breeding system, and power conversion system that turns fusion heat into electricity. By the middle of the next decade, Inertia aims to be generating power from this first plant, setting the stage for the company to build and connect additional grid-scale commercial power plants.
There are plenty of engineering trade-offs that the company will have to solve for. Take the decision around how to size the target chamber, for example. “If you make it bigger, your walls have an easier time and survive longer, but it’s more expensive. If you make it smaller, your walls have a tougher time because they’re closer to all the heat and energy that the fusion reaction is creating, but now your power plant costs less to build.”
But to Lawson, this represents exactly the type of problem Inertia was built to solve: complex engineering issues that come to the fore once scientists have demonstrated the fundamental physics are sound. He thinks other fusion companies may someday reach this stage, as well — though he’s unwilling to hazard a guess on exactly what approach or startup is best positioned to do so.
“There have been generations of scientists who’ve made their predictions about fusion energy and gotten it wrong,” he told me. “I’m not going to pretend to be smarter than them. All I’m here to say is, just knowing that one did work, we can commercialize it.”