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40+ climatetech startups join Greentown, including a dozen from Houston

green team

Twelve local startups have joined Greentown Houston, along with others from around the world. Photo courtesy Greentown Labs.

More than 40 climatetech startups joined the Greentown Labs Houston community in the second half of 2025. Twelve hail from the Bayou City.

The companies are among a group of nearly 70 that joined the climatetech incubator, which is co-located in Houston and Boston, in Q3 and Q4.

The new companies that have joined the Houston incubator specialize in a variety of clean energy applications, from green hydrogen-producing water-splitting cycles to drones that service wind turbines.

The local startups that joined Greentown Houston include:

  • Houston-based Wise Energie, which delivers turnkey microgrids that blend vertical-axis wind, solar PV, and battery storage into a single, silent system.
  • The Woodlands-based Resollant, which is developing compact, zero-emissions hydrogen and carbon reactors to provide low-cost, scalable clean hydrogen and high-purity carbon for the energy and manufacturing sectors.
  • Houston-based ClarityCastle, which designs and manufactures modular, soundproof work pods that replace traditional drywall construction with reusable, low-waste alternatives made from recycled materials.
  • Houston-based WattSto Energy, which manufactures vanadium redox flow batteries to deliver long-duration storage for both grid-scale projects and off-grid microgrids.
  • Houston-based AMPeers, which delivers advanced, high-temperature superconductors in the U.S. at a fraction of traditional costs.
  • Houston-based Biosimo, which is developing bio-based platform chemicals, pioneering sustainable chemistry for a healthier planet and economy.
  • Houston-based Ententia, which offers purpose-built, generative AI for industry.
  • Houston-based GeoKiln Energy Innovation, which is developing a new way to produce clean hydrogen by accelerating natural geologic reactions in iron-rich rock formations using precision electrical heating.
  • Houston-based Timbergrove, which builds AI and IoT solutions that connect and optimize assets—boosting visibility, safety, and efficiency.
  • Houston-based dataVediK, which combines energy-domain expertise with advanced machine learning and intelligent automation to empower organizations to achieve operational excellence and accelerate their sustainability goals.
  • Houston-based Resonant Thermal Systems, which uses a resonant energy-transfer (RET) system to extract critical minerals from industrial and natural brines without using membranes or grid electricity.
  • Houston-based Torres Orbital Mining (TOM),which develops autonomous excavation systems for extreme environments on Earth and the moon, enabling safe, data-driven resource recovery and laying the groundwork for sustainable off-world industry.

Other startups from around the world joined the Houston incubator in the same time period, including:

More than 100 startups joined Greentown this year, according to an end-of-year reflection shared by Greentown CEO Georgina Campbell Flatter.

Flatter joined Greentown in the top leadership role in February 2025. She succeeded former CEO and president Kevin Knobloch, who stepped down in July 2024.

"I moved back to the United States in March 2025 after six years overseas—2,000 miles, three children, and one very patient husband later. Over these months, I’ve had the chance to hear from the entrepreneurs, industry leaders, investors, and partners who make this community thrive. What I’ve experienced has left me brimming with urgent optimism for the future we’re building together," she said in the release.

According to Flatter, Greentown alumni raised more than $2 billion this year and created more than 3,000 jobs.

"Greentown startups and ecosystem leaders—from Boston, Houston, and beyond—are showing that we can move further and faster together. That we don’t have to choose between more energy or lower emissions, or between increasing sustainability and boosting profit. I call this the power of 'and,'" Flatter added. "We’re working for energy and climate, innovation and scale, legacy industry and startups, prosperity for people and planet. The 'and' is where possibility expands."

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Houston-based ENGIE to add new wind and solar projects to Texas grid

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Houston-based ENGIE North America Inc. has expanded its partnership with Los Angeles-based Ares Infrastructure Opportunities to add 730 megawatts of renewable energy projects to the ERCOT grid.

The new projects will include one wind and two solar projects in Texas.

“The continued growth of our relationship with Ares reflects the strength of ENGIE’s portfolio of assets and our track record of delivering, operating and financing growth in the U.S. despite challenging circumstances,” Dave Carroll, CEO and Chief Renewables Officer of ENGIE North America, said in a news release. “The addition of another 730 MW of generation to our existing relationship reflects the commitment both ENGIE and Ares have to meeting growing demand for power in the U.S. and our willingness to invest in meeting those needs.”

ENGIE has more than 11 gigawatts of renewable energy projects in operation or under construction in the U.S. and Canada, and 52.7 gigawatts worldwide. The company is targeting 95 gigawatts by 2030.

ENGIE launched three new community solar farms in Illinois since December, including the 2.5-megawatt Harmony community solar farm in Lena and the Knox 2A and Knox 2B projects in Galesburg.

The company's 600-megawatt Swenson Ranch Solar project near Abilene, Texas, is expected to go online in 2027 and will provide power for Meta, the parent company of social media platform Facebook. Late last year, ENGIE also signed a nine-year renewable energy supply agreement with AstraZeneca to support the pharmaceutical company’s manufacturing operations from its 114-megawatt Tyson Nick Solar Project in Lamar County, Texas.

Houston geothermal company raises $97M Series B

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Houston-based geothermal energy startup Sage Geosystems has closed its Series B fundraising round and plans to use the money to launch its first commercial next-generation geothermal power generation facility.

Ormat Technologies and Carbon Direct Capital co-led the $97 million round, according to a press release from Sage. Existing investors Exa, Nabors, alfa8, Arch Meredith, Abilene Partners, Cubit Capital and Ignis H2 Energy also participated, as well as new investors SiteGround Capital and The UC Berkeley Foundation’s Climate Solutions Fund.

The new geothermal power generation facility will be located at one of Ormat Technologies' existing power plants. The Nevada-based company has geothermal power projects in the U.S. and numerous other countries around the world. The facility will use Sage’s proprietary pressure geothermal technology, which extracts geothermal heat energy from hot dry rock, an abundant geothermal resource.

“Pressure geothermal is designed to be commercial, scalable and deployable almost anywhere,” Cindy Taff, CEO of Sage Geosystems, said in the news release. “This Series B allows us to prove that at commercial scale, reflecting strong conviction from partners who understand both the urgency of energy demand and the criticality of firm power.”

Sage reports that partnering with the Ormat facility will allow it to market and scale up its pressure geothermal technology at a faster rate.

“This investment builds on the strong foundation we’ve established through our commercial agreement and reinforces Ormat’s commitment to accelerating geothermal development,” Doron Blachar, CEO of Ormat Technologies, added in the release. “Sage’s technical expertise and innovative approach are well aligned with Ormat’s strategy to move faster from concept to commercialization. We’re pleased to take this natural next step in a partnership we believe strongly in.”

In 2024, Sage agreed to deliver up to 150 megawatts of new geothermal baseload power to Meta, the parent company of Facebook. At the time, the companies reported that the project's first phase would aim to be operating in 2027.

The company also raised a $17 million Series A, led by Chesapeake Energy Corp., in 2024.

Houston expert discusses the clean energy founder's paradox

Guest Column

Everyone tells you to move fast and break things. In clean energy, moving fast without structural integrity means breaking the only planet we’ve got. This is the founder's paradox: you are building a company in an industry where the stakes are existential, the timelines are glacial, and the capital requires patience.

The myth of the lone genius in a garage doesn’t really apply here. Clean energy startups aren’t just fighting competitors. They are fighting physics, policy, and decades of existing infrastructure. This isn’t an app. You’re building something physical that has to work in the real world. It has to be cheaper, more reliable, and clearly better than fossil fuels. Being “green” alone isn’t enough. Scale is what matters.

Your biggest risks aren’t competitors. They’re interconnection delays, permitting timelines, supply chain fragility, and whether your first customer is willing to underwrite something that hasn’t been done before.

That reality creates a brutal filter. Successful founders in this space need deep technical knowledge and the ability to execute. You need to understand engineering, navigate regulation, and think in terms of markets and risk. You’re not just selling a product. You’re selling a future where your solution becomes the obvious choice. That means connecting short-term financial returns with long-term system change.

The capital is there, but it’s smarter and more demanding. Investors today have PhDs in electrochemistry and grid dynamics. They’ve been burned by promises of miracle materials that never left the lab. They don't fund visions; they fund pathways to impact that can scale and make financial sense. Your roadmap must show not just a brilliant invention, but a clear, believable plan to drive costs down over time.

Capital in this sector isn’t impressed by ambition alone. It wants evidence that risk is being retired in the right order — even if that means slower growth early.

Here’s the upside. The difficulty of clean energy is also its strength. If you succeed, your advantage isn’t just in software or branding. It’s in hardware, supply chains, approvals, and years of hard work that others can’t easily copy. Your real competitors aren’t other startups. They’re inertia and the existing system. Winning here isn’t zero-sum. When one solution scales, it helps the entire market grow.

So, to the founder in the lab, or running field tests at a remote site: your pace will feel slow. The validation cycles are long. But you are building in the physical world. When you succeed, you don’t have an exit. You have a foundation. You don't just have customers; you have converts. And the product you ship doesn't just generate revenue; it creates a legacy.

If your timelines feel uncomfortable compared to software, that’s because you’re operating inside a system designed to resist change. And let’s not forget you are building actual physical products that interact with a complex world. Times are tough. Don’t give up. We need you.

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Nada Ahmed is the founding partner at Houston-based Energy Tech Nexus.

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