So far, there has been little talk in the industry about using geothermal energy to produce hydrogen. Due to the technical advancement of the installations and lower costs, projects have focused primarily on solar and wind energy. Nonetheless, one of the first consortiums to produce hydrogen from geothermal was announced last year.
What is geothermal energy?
Geothermal energy is defined as the Earth’s internal heat. The total amount of heat stored in the Earth’s crust is about 5.4 billion EJ. In 2006, experts at Iceland GeoSurvey indicated that if we could use even 0.1% of this, it would become possible to meet the world’s energy consumption for the next 13,500 years. Sounds good, right?
What is possible, however, is to use the heat accumulated in so-called hydrothermal or petrothermal systems. In the case of hydrothermal systems, the sources of energy are geothermal vapors and elevated-temperature waters, which are heated by heat from the Earth’s interior. They are defined as waters whose temperature at the outlet of the intake is not lower than 20°C.
Geothermal resources are found all over the world. In particular, along the borders of major tectonic plates, where most volcanoes are located. For the most part, they are hydrothermal systems. The heat of the rocks is exploited in only a few regions of the world, including Italy. It is a constantly developing technology with high potential. In Poland, there are mainly low-temperature deposits. Here, the waters filling the porous rocks occur on average at a depth of 700 to 3,000 meters and reach temperatures of 20-80°C, rarely reaching about 100°C.
Geothermal energy for hydrogen production
Geothermal energy is widely used in the food industry (processing), refrigeration, and manufacturing, as well as in animal husbandry and the recreational sector. The exploitation of geothermal sources for heating applications is also prevalent in Poland. There are already eight geothermal heating plants in the country, including those in Pyrzyce, Stargard Szczeciński, and Uniejów.
Geothermal energy can also be used to produce renewable hydrogen. For this purpose, we can exploit different technologies, the common part of which remains the conversion of the mechanical energy of vibrating particles (heat) into the mechanical energy of the rotary motion of the turbine blades. Interestingly, experts also point to another method, which is the extraction of hydrogen directly from geothermal gases in power plants, but at this point, it is not as widespread and cost-effective as the electrolytic production method.
Geothermal energy – advantages of the use
Geothermal heat is naturally formed deep beneath the Earth’s surface and is the largest potential source of renewable energy. It is estimated that up to 70% of geothermal resources have yet to be discovered. On the other hand, documented reserves of geothermal water and steam are held by more than 80 countries. 72 countries use geothermal energy directly, and 24 countries use it to generate electricity. Of these, China, Sweden, Iceland, the US, Turkey, Italy, and New Zealand are in the lead.
In countries with a high share of geothermal energy in the energy mix, it is possible to produce renewable hydrogen using grid power. An example is Iceland, where electricity generated from geothermal at competitive prices could be used to produce hydrogen to meet the needs of the entire transportation sector. Of course, this is assuming a reduction in the cost of the technology and thus the price of hydrogen.
A significant advantage of geothermal in Poland is the fact that regions with favorable geothermal conditions are located near heavily industrialized areas and those with a high density of urban agglomerations.
Moreover, unlike photovoltaics and wind farms, geothermal offers a stable and reliable supply of energy around the clock, regardless of the season, day, or current weather conditions. This means that hydrogen production would take place via continuous electrolysis.
Geothermal energy for hydrogen production – first projects
One of the first projects focused on using geothermal energy to produce hydrogen has been announced for 2022. It is a collaboration between CeraPhi Energy and Climate Change Ventures.
The companies have teamed up to develop and implement a scalable method for producing zero-emission green hydrogen using electricity extracted from geothermal sources to drive the electrolysis process. According to CeraPhi, the basis of the project will be a proprietary closed-loop technology with a system designed to provide the continuous electrolysis process with the necessary baseload power. As part of the announced collaboration, the British power company is to provide its closed-loop operating technology.
While geothermal is not a viable method of hydrogen production at this point, the potential for geothermal sources is enormous, indicating that they may well become important to the global hydrogen industry soon.
[1] O. G. Flovenz, Geothermal Energy, an option for hydrogen production?, 2006
[2] Ibid.
