The Potential for Geothermal Energy in Supporting Hydrogen Production Technologies

As the global push for decarbonization intensifies, hydrogen is emerging as a versatile energy carrier capable of decarbonizing hard-to-abate sectors such as heavy industry, long-haul transport, and power generation. However, the environmental benefits of hydrogen are entirely dependent on how it is produced. Green hydrogen—produced via water electrolysis powered by renewable energy—is the cleanest route, but its scalability requires reliable, low-cost, and continuous electricity. Among renewable sources, geothermal energy offers a unique combination of baseload availability, high capacity factors, and low lifecycle emissions. This synergy makes geothermal-powered hydrogen production a compelling solution for regions with geothermal resources. This article explores the technologies, economic drivers, current projects, and future potential of coupling geothermal energy with hydrogen production.

Understanding Geothermal Energy

Geothermal energy originates from the Earth’s internal heat, generated by radioactive decay and residual heat from planetary formation. This heat is stored in rocks and fluids beneath the surface and can be tapped for electricity generation and direct use. Geothermal power plants typically draw hot water or steam from underground reservoirs at depths of 1–5 kilometers. The three main types of geothermal power plants are dry steam, flash steam, and binary cycle, with binary plants able to exploit lower-temperature resources (below 150°C).

One of geothermal energy’s most valuable attributes is its consistency. Unlike solar and wind, which are intermittent, geothermal power operates at capacity factors of 80–95%, providing steady baseload power around the clock. The global installed geothermal capacity exceeded 16 GW in 2024, with significant untapped potential in the Ring of Fire, East African Rift, and other tectonically active areas. Enhanced Geothermal Systems (EGS) are expanding the resource base by engineering reservoirs in hot dry rock, potentially making geothermal accessible far beyond traditional hydrothermal fields.

Hydrogen Production Technologies

Hydrogen can be produced from a variety of feedstocks and energy inputs. The color code distinguishes carbon intensity: grey hydrogen from natural gas reforming (high CO₂), blue hydrogen with carbon capture (low CO₂), and green hydrogen from electrolysis using renewable electricity (near-zero CO₂). For a fully sustainable system, green hydrogen is the target, and electrolysis is the key technology.

Electrolysis Pathways

  • Alkaline Electrolysis (AEL) – A mature, low-cost technology using a liquid potassium hydroxide electrolyte. It operates at 60–80°C and achieves efficiencies of 60–75% (LHV). AEL is well-suited for large-scale, steady-state operation, making it a natural match for geothermal baseload power.
  • Proton Exchange Membrane (PEM) Electrolysis – Uses a solid polymer membrane and operates at higher current densities, enabling rapid ramping. PEM systems are more compact and efficient (up to 80% LHV) but require pure water and noble metal catalysts (platinum, iridium). Their flexibility can complement geothermal’s steady output if hydrogen demand is variable.
  • Solid Oxide Electrolysis (SOEC) – Operates at high temperatures (700–850°C) and can utilize both electricity and heat to split water. When integrated with geothermal heat, SOEC can achieve efficiencies exceeding 90% (LHV). This high-temperature route is particularly synergistic with geothermal because many geothermal reservoirs produce fluids at 150–300°C, offering a source of industrial heat that reduces the electrical input needed for electrolysis.

Beyond electrolysis, thermochemical water-splitting cycles—using heat directly to produce hydrogen—are in research stages. Geothermal heat could drive such cycles at moderate temperatures (500–1000°C), though EGS systems are needed to reach the highest temperatures.

The Role of Geothermal Energy in Supporting Hydrogen Production

Integrating geothermal energy with hydrogen production offers several distinct advantages over pairing hydrogen with solar or wind alone:

Reliable Baseload Power for Electrolysis

Electrolyzers operate most efficiently at constant load. Solar and wind farms force electrolyzers to cycle or require costly battery storage to smooth output. Geothermal provides inherent baseload power, allowing electrolysis plants to run at maximum capacity for thousands of hours per year. This high utilization rate dramatically lowers the levelized cost of hydrogen (LCOH) because the capital cost of the electrolyzer is amortized over more operating hours.

Combined Heat and Power (CHP)

Geothermal plants can be designed to deliver both electricity and low- to medium-grade heat. For example, after generating power, spent geothermal brine (typically 70–120°C) can provide process heat for preheating feedwater in electrolysis, improving system efficiency. In a SOEC plant, geothermal steam can directly replace electrical heating, reducing the electricity requirement by 25–30%. Some geothermal sites also produce significant volumes of steam, which can be fed into high-temperature electrolyzers without additional energy for steam generation.

Reduced Carbon Footprint

Geothermal power has lifecycle greenhouse gas emissions of only 10–40 g CO₂-eq per kWh—similar to wind and lower than solar PV when accounting for manufacturing. Geothermal electrolysis thus yields hydrogen with a carbon intensity of 0.5–2 kg CO₂ per kg H₂ (depending on grid mix for auxiliary loads), compared to 8–10 kg for grey hydrogen and 4–6 kg for blue hydrogen. This clean profile qualifies geothermal hydrogen for green hydrogen certificates and carbon credits.

Economic Viability

Geothermal electricity costs have fallen to $50–80/MWh in high-quality resources (e.g., Kenya, Indonesia, the U.S. West). For each $10/MWh reduction in power price, the LCOH from a dedicated electrolysis plant drops by approximately $0.30–0.40/kg. At a power cost of $60/MWh and an electrolyzer utilization of 95%, geothermal hydrogen could be produced for $3–4/kg today, with potential to fall below $2/kg as electrolyzer costs decline and geothermal technology matures. This is competitive with solar-wind hybrid hydrogen in many markets, especially when storage penalties are factored in.

Current Projects and Developments

Several pioneering projects are demonstrating the geothermal-hydrogen nexus:

Iceland – Geothermal Hydrogen Leader

Iceland benefits from abundant high-temperature geothermal resources. The HS Orka plant in Reykjanes operates a 100 MW geothermal facility and has partnered to produce green hydrogen for local industry and export. The country also uses geothermal heat for steam methane reforming with carbon capture (blue hydrogen) and is exploring direct geothermal hydrogen via high-temperature electrolysis. Iceland’s power prices are among the lowest in Europe, enabling hydrogen export feasibility.

United States – DOE and Industry Initiatives

The U.S. Department of Energy’s Geothermal Hydrogen Program funds research into coupling EGS with SOEC. In Idaho, the Idaho National Laboratory runs a pilot demonstrating low-temperature electrolysis powered by geothermal electricity. Additionally, the Imperial Valley in California hosts a 50 MW geothermal plant connected to a 5 MW PEM electrolyzer unit, producing hydrogen for blending into the natural gas grid.

New Zealand – Geothermal Heat for Industrial H₂

New Zealand’s Taupō Volcanic Zone supplies heat for multiple geothermal power plants. Contact Energy and Tuaropaki Trust have explored using geothermal steam to produce hydrogen for the domestic mobility sector. A 2023 feasibility study confirmed that combining geothermal heat with alkaline electrolysis could produce hydrogen at NZ$3.5–4.0/kg.

Enhanced Geothermal Systems (EGS) – Expanding the Map

EGS technology, such as the DOE’s FORGE site in Utah, is creating geothermal reservoirs in hot dry rock. EGS could unlock geothermal potential in areas without natural hydrothermal systems, including parts of the U.S. Midwest, Europe, and Australia. If EGS proves commercially viable, the geographic scope for geothermal hydrogen expands significantly, reducing dependence on volcanic regions.

Challenges and Opportunities

Despite the promise, several barriers must be overcome to scale geothermal hydrogen production.

High Upfront Capital Costs

Geothermal projects require $3–7 million per MW of installed capacity, largely for drilling exploration wells and reservoir stimulation. This high initial cost discourages investment compared to solar or wind, which have lower capital intensity. However, once built, geothermal has very low operating costs (the fuel is free) and a long asset life (30–50 years). Innovative financing models, including government loan guarantees and carbon contracts for difference, can mitigate this hurdle.

Resource Location and Transmission

Geothermal resources are often located in remote areas far from industrial hydrogen users. Transporting hydrogen via pipeline or truck adds cost. One solution is to co-locate data centers, ammonia production, or steel manufacturing near geothermal hydrogen plants. Another is to convert hydrogen into ammonia or methanol for easier shipping. Grid connection costs can be shared with other renewable projects.

Brine Chemistry and Environmental Issues

Geothermal brines contain dissolved minerals (silica, chlorides, heavy metals) that can corrode equipment and cause scaling. Advanced materials and brine treatment systems are needed to extend plant life. Also, geothermal fluid reinjection is required to maintain reservoir pressure and minimize land subsidence, which adds operational complexity. Proper reservoir management can make geothermal a sustainable, low-impact energy source.

Hydrogen Storage and Handling

Hydrogen has low volumetric energy density and requires compression or liquefaction for storage. Geothermal’s steady output could be paired with salt cavern storage or lined rock caverns to buffer supply and demand. Research into underground hydrogen storage in depleted geothermal reservoirs is another promising avenue.

Future Prospects and Research Directions

The future of geothermal hydrogen hinges on technological innovation and policy support. Key research areas include:

  • High-Temperature Electrolysis Optimization – Developing SOEC stacks that can accept geothermal steam directly, reducing electrical demand and increasing overall system efficiency to >85%.
  • Hybrid Geothermal-Solar-Wind Systems – Using geothermal as baseload firming for variable renewables, with excess solar/wind power also feeding electrolyzers to maximize hydrogen output during peak sun and wind hours.
  • Geothermal Direct Heat for Thermochemical Cycles – Advanced cycles such as the copper-chlorine or hybrid sulfur process could use geothermal-derived process heat at 500–800°C (achievable with EGS) to split water without any electricity, potentially producing hydrogen at lower cost than electrolysis.
  • Underground Hydrogen Storage in Geothermal Reservoirs – Injecting hydrogen into depleted geothermal formations could provide large-scale, low-cost storage, even as the reservoir continues to supply heat for power generation.
  • Carbon Capture and Utilization – Combining geothermal hydrogen with captured CO₂ to produce synthetic methane, methanol, or e-fuels could create a circular carbon economy.

Policy and Market Drivers

Governments worldwide are setting ambitious hydrogen production targets. The U.S. Hydrogen Earthshot aims to cut clean hydrogen cost to $1/kg by 2030. Geothermal can contribute by providing ultra-low-cost power in favorable regions. The European Union’s Renewable Energy Directive (RED III) sets greenhouse gas thresholds for green hydrogen that favor geothermal over grid-powered electrolysis. In Japan and South Korea, hydrogen import strategies often include geothermal-rich partners like Iceland and Indonesia.

Conclusion

Geothermal energy possesses inherent characteristics—baseload reliability, high capacity factor, low emissions, and co-generation potential—that make it an ideal partner for clean hydrogen production. While challenges of capital cost, resource location, and brine management remain, concerted research and early demonstration projects are steadily resolving them. The integration of geothermal and hydrogen technologies can deliver a scalable, dispatchable, and truly green hydrogen supply that complements the expansion of solar and wind. As drilling technology advances and EGS expands the resource base, geothermal hydrogen could become a cornerstone of the global energy transition, offering a firm, low-carbon bridge to a hydrogen economy. Policymakers, utilities, and investors who recognize this synergy today will be well-positioned to lead in the clean energy markets of tomorrow.