Energy production dependent on fossil fuels releases approximately 36 billion tons of carbon dioxide annually, accounting for roughly 80 percent of global carbon emissions and driving rising sea levels, severe pollution, and melting glaciers. In an evaluative review published in Carbon Neutral Systems, researchers Drashti Solanki, Manan Shah, and Mitul Prajapati investigate how non-conventional renewable energy sources, specifically geothermal and wind power, can produce green hydrogen to replace depleting fossil fuels. Increasing global electricity consumption has accelerated power generation across thermoelectrical plants burning diesel and fossil fuels, exacerbating environmental damage. Although hydrogen is the universe’s most abundant element and performs efficiently in internal combustion engines, its production currently costs three times more than fossil fuel energy. Synthesizing thermodynamic cycle analyses and field data, the authors demonstrate that integrating geothermal heat and wind turbines with water electrolysis provides a viable low-carbon pathway to help mitigate projected temperature increases of 1.25 to 5.4 degrees Celsius between 2025 and 2100.
Global industry consumes roughly 55 million tons of hydrogen annually, with demand expanding by 6 percent each year. Hydrogen serves as a critical resource for transportation, steam-driven power generation, fertilizer manufacturing, petroleum refining, and aerospace propellants. Because it can be transported and stored as compressed gas, solid hydride, or cryogenic liquid, hydrogen provides versatile operational utility. However, conventional fossil fuel methods dominate production due to low costs and established infrastructure. Natural gas provides 50 percent of global hydrogen, petroleum supplies 18 percent, coal yields 18 percent, and water electrolysis contributes only 3.9 percent. The World Bank notes that 98 percent of current hydrogen stems from natural gas and coal, generating approximately 3 percent of global carbon emissions. Conventional processes like steam methane reforming, partial oxidation, and autothermal reforming release harmful pollutants, including carbon dioxide, carbon monoxide, sulfur dioxide, and hydrogen sulfide, which cause respiratory ailments and reduce agricultural crop yields.
To eliminate emissions, researchers are turning toward green hydrogen produced through renewable water electrolysis, which supports limiting atmospheric temperature rise to 2 degrees Celsius. The review explores several renewable alternatives, including solar energy, biomass, and microalgae. Solar water splitting encompasses photovoltaic water electrolysis alongside photochemical, semiconductor, photobiological, and hybrid methods. While photovoltaic systems offer low maintenance and minimal emissions, high capital costs, radiation intermittency, and heat-induced panel degradation present operational hurdles. Biomass gasification provides an economical, carbon-neutral pathway that captures atmospheric carbon during biological growth. However, its conversion efficiency reaches only about 50 percent, and tar formation clogs processing equipment while biomass structural complexity introduces gas impurities. Plasma-assisted gasification and tight pressure controls help mitigate these drawbacks. Additionally, microalgae photo-fermentation yields biohydrogen under moderate temperatures and pressures through light-dependent biophotolysis, where photosynthetic enzymes split water into hydrogen and oxygen, while algal glucose can undergo thermochemical processing.
Geothermal energy provides clean, continuous energy extracted from deep subsurface heat, where core temperatures reach approximately 5500 degrees Celsius at 6437.4 kilometers depth and radiate heat at 59 megawatts per square meter. The Earth’s crust stores roughly 5.4 billion exajoules of heat, meaning that tapping only 0.1 percent could satisfy global energy demand for 13.5 years. Producing virtually no atmospheric emissions, geothermal resources supply baseload electricity for electrolysis while supporting direct heating, fish farming, and aquaculture. Prior investigations demonstrate that integrating geothermal heat into water electrolysis decreases electrical work consumption for electrolysis by 16 percent and liquefaction by 2 percent. Combining geothermal steam at 200 degrees Celsius with high-temperature steam electrolysis like the HOT ELLY system, which operates between 800 and 1000 degrees Celsius, reduces hydrogen production costs by about 19 percent. Regional analysis indicates that 12 states in the Western United States possess significant geothermal resources, with 11 states generating 22,990 megawatts of power.
Geothermal hydrogen generation uses closed thermodynamic cycles to drive turbines that supply power to electrolyzers. In binary power plants using the Rankine cycle, working fluid choice depends on operating temperature: isobutane delivers optimal net output and efficiency below 160 degrees Celsius, whereas isopentane performs best above 160 degrees Celsius. Geothermal water exiting the heat exchanger preheats feed water for proton exchange membrane electrolyzers, reducing power consumption. Research indicates that such Rankine systems achieve a thermal efficiency of 11.4 percent, an exergy efficiency of 45.1 percent, and overall system energy and exergy efficiencies of 6.7 percent and 23.8 percent, respectively, with power expanding from 3810 kilowatts at 160 degrees Celsius to 5575 kilowatts at 180 degrees Celsius. Alternatively, the Kalina cycle utilizes an ammonia-water working fluid across absorption refrigeration loops, exploiting different boiling points to enhance thermodynamic efficiency. Operating with a 10 Kelvin inlet temperature difference, the Kalina cycle achieves thermal and exergy efficiencies of 22.28 percent and 21.37 percent, producing hydrogen at 29.29 dollars per gigajoule.
Geothermal source temperature strongly governs thermodynamic performance and economic viability. Heating geothermal liquid from 130 to 200 degrees Celsius elevates exergy efficiency from 38 to 64 percent, while raising proton exchange membrane electrolyzer temperature from 60 to 85 degrees Celsius increases hydrogen production by 5 percent. Higher operating temperatures improve system thermal efficiency and decrease hydrogen synthesis costs, making unit cost inversely proportional to efficiency. Sensitivity analyses using Engineering Equation Solver software demonstrate that higher geothermal temperatures increase net work output by 75.81 percent and hydrogen production by 72.94 percent, maintaining steady output at 590.4 kilowatt-hours and hydrogen rates of 6.06 kilograms per hour across seasonal variations. In enhanced geothermal systems, injecting carbon dioxide with water yields higher thermal recovery and economic gains, with an optimized 110 kilograms per second injection rate and 20 percent carbon dioxide ratio achieving a net present value of 42.4 million dollars. Furthermore, electrolyzing hydrogen sulfide at 150 degrees Celsius within geothermal plants produces hydrogen and sulfur, increasing exergy efficiency from 52.3 to 61.9 percent between 273 and 323 Kelvin.
Wind energy captures kinetic motion from atmospheric currents, transforming rotating blade energy into electricity across environments ranging from deserts to metropolitan regions. Because wind turbines generate alternating current that fluctuates in magnitude and frequency, power converters transform this electricity into direct current for electrolysis. Wind-based hydrogen systems frequently utilize alkaline electrolyzers with concentrated alkaline solutions to split water into hydrogen at the cathode and oxygen at the anode. The hydrogen is then compressed and distributed via local pipelines, central networks, or underground geological storage. Life cycle assessments evaluating wind-powered water electrolysis demonstrate exceptionally low carbon footprints, calculating greenhouse gas emissions at 0.68 plus or minus 0.05 kilograms of carbon dioxide equivalent per kilogram of hydrogen produced. Over an estimated 22-year operational lifespan, this clean hydrogen can be transported across 400-kilometer dedicated pipelines to supply industrial bitumen upgrader plants, verifying that wind-driven electrolysis ensures low greenhouse gas emissions across both production and transmission phases.
Implementing wind-powered hydrogen production requires accurate meteorological modeling and grid integration, especially when operating within weak electrical grids. Assessments show that low-pressure water electrolysis provides the highest operational efficiency, absorbing surplus wind generation to balance grid loads. Wind potential calculations frequently employ the Weibull distribution method, evaluating speed data at 10-meter heights within a 7.5-kilometer radius. Multi-criteria regional studies evaluating 13 Iranian cities via Data Envelopment Analysis, Analytical Hierarchy Process, and TOPSIS identified Izadkhast as the optimal site, producing 21.9 tons of hydrogen annually with a 900-kilowatt turbine. Economic analysis across Ardebil province showed that 100-kilowatt turbines achieved 5-year payback periods in high-density areas like Namin and Ardebil, compared to 6.1 to 10.2 years in Khalkhal and Meshkinshahr. Suburban modeling utilizing artificial intelligence demonstrated that Long Short-Term Memory algorithms outperformed Support Vector Regression, accurately predicting 6.76 kilograms per day of hydrogen production from a 1.5-megawatt turbine located 500 meters above sea level.
Despite clear decarbonization advantages, scaling renewable hydrogen faces substantial spatial, economic, and safety constraints. Land availability limits wind farm expansion because large installations require extensive communal land that is difficult to secure. Intermittent wind speeds and uneven geographical distribution also degrade electrolyzer efficiency. Geothermal projects can disrupt local ecosystems, damaging wildlife breeding grounds, interfering with migration patterns, and endangering native species. Financially, commercial green hydrogen systems require large capital investments of approximately 5 million dollars, with high upfront drilling costs creating severe barriers in regions lacking infrastructure. Furthermore, standard electrolysis processes like proton exchange membrane and alkaline water electrolysis exhibit low conversion efficiencies under variable loads. Storage introduces acute physical risks because hydrogen is a highly combustible gas with low density and wide flammability limits. These safety challenges were tragically demonstrated by the 1937 Hindenburg airship disaster, where an electric spark ignited leaking hydrogen during landing, killing 36 passengers and injuring a ground crew member.
To overcome these obstacles and facilitate a carbon-free transition, researchers propose several innovative engineering and policy solutions. Geothermal development costs can be mitigated by retrofitting abandoned oil wells, circulating working fluid through a closed U-tube loop to extract reservoir heat without incurring new drilling expenses. To address hydrogen storage hazards, compressing gas between 350 and 700 bar or refrigerating it to cryogenic liquid states around minus 253 degrees Celsius significantly reduces chemical reactivity and prevents catastrophic ignition. Power grids can also adopt renewable energy banking frameworks, which store surplus electricity during peak generation periods to power electrolyzers during resource shortfalls. Furthermore, government policies, infrastructure funding, and targeted economic subsidies are essential to derisk private investments and support green hydrogen scaling. By combining optimized closed-loop geothermal cycles and wind-driven water electrolysis with strategic energy banking, renewable hydrogen production provides a technically feasible and environmentally sound foundation for replacing fossil fuels and advancing global decarbonization goals.
Subject of Research: Geothermal and wind energy integration for sustainable green hydrogen production
Article Title: The role of geothermal and wind energy in hydrogen production: towards a carbon-free future
Article References: Solanki, D., Shah, M., & Prajapati, M. (2025). The role of geothermal and wind energy in hydrogen production: towards a carbon-free future. Carbon Neutral Systems, 1(1), Article 9. https://doi.org/10.1007/s44438-025-00008-w
Image Credits: AI Generated
DOI: 10.1007/s44438-025-00008-w
Keywords: Green Hydrogen, Geothermal Energy, Wind Energy, Water Electrolysis, Thermodynamic Cycles, Renewable Energy, Decarbonization, Clean Technology, role, geothermal, wind, energy
