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Houston founder on driving the future of geothermal energy, storage

In a recent Energy Tech Startups Podcast episode, Cindy Taff discussed the evolution of Sage GeoSystems, the challenges of scaling hard tech solutions, and the opportunities presented by geothermal and pumped hydro energy storage. Photo courtesy of Sage

Cindy Taff, co-founder and CEO of Sage GeoSystems, has emerged as a visionary leader in the energy transition, recently named to Time magazine’s 100 Most Influential Climate Leaders in Business for 2024. Under her leadership, Sage is not only advancing geothermal energy innovation but also redefining how energy storage can support a renewable-powered grid.

In a recent Energy Tech Startups Podcast episode, Taff discussed the evolution of Sage GeoSystems, the challenges of scaling hard tech solutions, and the opportunities presented by geothermal and pumped hydro energy storage. Her insights reflect the unique perspective of a founder bridging oil and gas expertise with renewable energy innovation.

- YouTubeCindy shares how Sage Geosystems is leveraging its oil and gas expertise to develop groundbreaking subsurface pumped hydro ...

Breaking Boundaries with Geopressured Geothermal Systems

Sage GeoSystems is at the forefront of next-generation geothermal energy, advancing Geopressured Geothermal Systems (GGS) that can be deployed in a wide range of geographies. Unlike traditional geothermal systems, which rely on natural water reservoirs near volcanic activity, Sage’s engineered reservoirs allow geothermal energy to be tapped almost anywhere.

“Geothermal energy is no longer restricted to specific conditions,” Taff explained. “Our systems are flexible, scalable, and capable of meeting the needs of energy-intensive applications like data centers—including a recent deal with Meta to deliver 150 megawatts of geothermal power for their facilities.”

This adaptability sets Sage apart, offering a path to reliable, clean energy that can complement intermittent sources like wind and solar. Sage also secured a win in the Energy Transition Business category alongside notable finalists like Amperon and Tierra Climate, underscoring its leadership in innovative energy solutions.

Pivoting Toward Subsurface Energy Storage

While initially focused solely on geothermal, Sage uncovered a transformative opportunity in subsurface pumped hydro energy storage during field trials. Dubbed “upside-down pumped hydro,” the solution provides long-duration energy storage capable of balancing the grid for 17+ hours—far surpassing the capabilities of lithium-ion batteries for extended periods.

“Pumped storage hydropower is a critical piece of the energy puzzle,” Taff emphasized. By storing energy during off-peak times and releasing it when solar and wind aren’t producing, Sage is helping bridge the intermittency gap in renewables. This approach positions pumped storage as a game-changer for a reliable, clean energy grid.

Lessons from the Founder’s Journey

Taff’s transition from a 35-year career at Shell to geothermal entrepreneurship offers valuable lessons for founders in capital-intensive industries:

  1. Leverage Expertise, but Stay Open to New Solutions:
    Taff’s oil and gas background enabled her to approach geothermal with deep technical knowledge, but Sage’s pivot to energy storage illustrates the importance of staying adaptable during development.
  2. Educate Financial Stakeholders:
    Securing funding for hard tech remains a challenge. “Investors often lack the subsurface knowledge needed to understand our technology,” Taff explained. She emphasized the need to bring on team members who can translate technical innovation into financial terms.
  3. Be Ready for Capital-Intensive Scaling:
    With geothermal plants costing millions to build, startups must carefully manage capital and timelines. Taff encourages founders to seek strategic investors, like Chesapeake Energy, who understand the challenges and potential of scaling infrastructure.

Beyond Geothermal: A Call for Pumped Storage Hydropower

In addition to geothermal, Taff champions pumped storage hydropower as an underutilized climate solution. “While lithium-ion batteries get a lot of attention, pumped storage hydropower offers long-duration storage that can stabilize the grid for days, not just hours,” she said.

By storing excess energy during off-peak times and releasing it when solar and wind aren’t producing, pumped storage hydropower can play a critical role in balancing renewables. Sage GeoSystems is uniquely positioned to integrate this technology into a broader energy strategy, offering sustainable and scalable solutions for energy-intensive industries.

A Vision for Geothermal and the Energy Transition

Looking ahead, Taff sees geothermal energy and storage as critical components of a sustainable energy mix. “We’re still in the early stages, but geothermal is following a trajectory similar to wind and solar 15 years ago,” she said. Sage’s innovative approaches are paving the way for geothermal to become a scalable, competitive solution, capable of powering industries and data centers while providing energy storage that stabilizes the grid.

With her recognition by Time magazine and a recent deal with Meta, Sage GeoSystems is proving that geothermal energy can be a powerful ally in achieving global decarbonization goals. The company’s innovative Geopressured Geothermal Systems and subsurface storage solutions are laying the groundwork for a reliable and sustainable energy future.

Listen to the full episode with Cindy Taff on the Energy Tech Startups Podcast here.

Energy Tech Startups Podcast is hosted by Jason Ethier and Nada Ahmed. It delves into Houston's pivotal role in the energy transition, spotlighting entrepreneurs and industry leaders shaping a low-carbon future.


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A View From HETI

The funding will support the construction of the Hertha Chalyx plant. Photo courtesy Hertha Metals

Conroe-based Hertha Metals has closed a $133.65 million Series A round that includes a $65 million equity investment from the Pentagon. The startup uses a one-step process to convert iron into molten steel or high-purity iron.

Khosla Ventures and Doerr Capital co-led the round, with participation from CEV, Pear Ventures, Gates Frontier, Niterra SUISO no MORI Fund, Toyota Ventures, and Siemens Financial Services.

The federal investment came from the U.S. Department of Defense’s Industrial Base Analysis and Sustainment program. The program aims to strengthen and modernize the U.S. Defense Industrial Base, a network that researches, designs, builds, and maintains military weapons, equipment, technology, and services.

The Series A funding will finance construction of Hertha Chalyx, a plant that will be capable of producing 10,000 metric tons of steel-grade and magnet-grade high-purity iron.

Hertha says Chalyx will provide U.S.-made material for manufacturers of rare-earth magnets. Today, China controls more than 90 percent of the global manufacturing of rare-earth magnets.

Rare-earth magnets can be found in fighter jets, smart bombs, submarines, satellites, drones and other military hardware. These magnets are also key components in electric vehicle motors, wind turbines, computer hard drives, smartphones, headphones, cordless tools and an array of other products.

“Every electric vehicle, aerospace platform, radar system, and data center depends on domestic iron and magnet feedstock suppliers,” Laureen Meroueh, founder and CEO of Hertha, said in a press release.

“Hertha Chalyx closes that gap,” she added. “We are building the supply chain this country needs, and we are doing it by providing a domestic cost-competitive option for manufacturers while unlocking safer and cleaner production.”

Hertha says Chalyx, alongside its Pi100 pilot project, will be the first modern-day “iron and steel innovation complex.” The startup expects to break ground on Chalyx this year.

Since its founding in 2022, Hertha has raised more than $150 million from investors.

This spring, Hertha led the manufacturing category on Fast Company’s list of the World’s Most Innovative Companies of 2026.

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