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How Europe can benefit from a promising clean energy source you’ve never heard of

May 15, 2024 Work Area: Superhot Rock Energy

Superhot rock energy is an untapped resource that can help Europe meet its twin goals of energy security and climate neutrality.   

Europe’s energy crisis has shown that overreliance on a single energy supplier and a narrow set of technology options is not a viable path for the region. This new geopolitical context, which threatens Europe’s position as a climate leader, has underscored the need for an accelerated energy transition – moving away from external fossil fuel dependencies towards a more self-reliant, energy-secure future that puts decarbonisation at its core. This can only be achieved by pursuing an options-based climate strategy that embraces a diverse set of clean firm energy sources, including next-generation geothermal technologies that can harness superhot rock energy (SHR). Given proper support, SHR has the potential to strengthen Europe’s energy system, ensuring clean, renewable, always-on power and heat produced locally in the continent.  

What is superhot rock energy?   

Superhot rock energy is a next-generation geothermal energy source that aims to produce power from deeper and hotter conditions than current next-generation geothermal projects and today’s conventional geothermal systems. Superhot rock energy technology takes advantage of the “supercritical” state of water (above 400°C approx.) which has properties of both a liquid and a vapor at the same time.   

In superhot rock systems, water is injected to depths where the rock temperature exceeds 400°C and then is returned to the surface to generate power. This process leverages next-generation geothermal technologies, such as enhanced geothermal systems (EGS) or closed loop geothermal systems (CLGS) to circulate the fluid in regions without a natural source of hydrothermal fluid or permeability. In research settings, geothermal systems above 400˚C and 220bar are often referred to as “supercritical geothermal systems.” The production of water above 400˚C is expected to produce 5-10 times the energy of a conventional geothermal well.   

The depth required to reach 400°C rock varies – in some parts of the Earth’s crust the heat is shallow (2-5 km), and elsewhere it is deeper (10-20 km). Superhot rock systems can be demonstrated with today’s technology where heat is relatively shallow (4-7 km). Several EU-funded projects have already reached supercritical conditions. Reaching the depth required for “geothermal everywhere” will require technological advancements. Maturing tools and methods to operate in extreme heat and pressure conditions would mean that we could access heat resources practically everywhere.  

Why does Europe need superhot rock energy?  

With strategy and robust funding, superhot rock energy could provide terawatts of locally sourced zero-carbon baseload power within a few decades, importantly contributing to Europe’s climate and energy security objectives.  

Pursuing this clean, firm, and literally inexhaustible energy source would help Europe transition away from being dependent on foreign fossil fuels. The energy density and energy per well of this energy generation pathway means that it could be cost-competitive with other energy sources once it reaches commercial scale. Generating both electricity and heat, superhot rock energy could also contribute to producing significant amounts of clean hydrogen that several sectors will need to decarbonise.  

In addition, superhot rock energy systems have minimal land use and above-ground structure requirements, which is particularly relevant in the context of limited land availability in Europe.  Operations surrounding superhot rock energy systems could also generate a significant number of jobs, including leveraging the skills of the existing energy workforce.  

Relative magnitude of surface area used for different energy sources to meet the total energy demand of Italy.  

What is the state of superhot rock energy in Europe?  

First-of-a-kind modeling from Clean Air Task Force and the University of Twente estimated superhot rock energy potential around the world. This modeling represents preliminary estimates of superhot rock potential, rather than confirmed resources. Nevertheless, it suggests that Europe is well-endowed with superhot rock resources.  

CATF’s model finds superhot rock energy potential across about 9% of Europe’s land area — amounting to nearly 900 thousand km2 — at depths below 12.5 km. With a concerted focus on deep drilling research and technology innovation, Europe should be able to access superhot rock across the continent.  

Just 1% of Europe’s superhot rock resource has the potential to provide 2.1 terawatts of energy capacity, which could generate nearly 18,000 terawatt-hours (TWh) of electricity. Though these numbers are only preliminary, their scale is enormous. To provide perspective, the city of Berlin consumed 12.5 TWh in 2022, so Europe’s superhot rock energy resource capacity could theoretically satisfy the annual electricity demands of over 1,400 additional cities equivalent to Berlin.  

Europe is already a leader in researching engineered geothermal and superhot rock systems, with projects in the Upper Rhine Valley, Italy, Iceland and elsewhere. Several projects funded by the EU Horizon programme (DEEPEGS, DESCRAMBLE, GEMex) have already reached supercritical conditions.  Others (IMAGE, HITI, DEEPEN) have made notable advancement in adjacent research. which is also conducted by private companies, for instance in drilling technologies. All these efforts need to be coordinated, followed up and scaled up to demonstrate superhot rock energy and deploy it at scale in the EU and beyond.  

What does Europe need to do to be able to benefit from superhot rock energy?  

  1. Develop a strategy for geothermal energy  

    The EU needs a comprehensive strategy for a wider uptake of geothermal energy. Superhot rock energy should be a key component of this strategy, providing a pathway towards demonstration and deployment at scale.  

    Some countries may benefit from developing national geothermal strategies as well. Alternatively, National Energy and Climate Plans can be used to plan for superhot rock energy development and demonstration.  Moreover, CATF’s  public polling across six European countries shows that, despite initial low awareness levels of superhot rock energy, after reading a description of the technology, respondents demonstrated strong support for its rollout across all surveyed countries (with 63% showing support, 30% feeling neutral and only 7% showing rejection). 
  1. Fund a bold research agenda  

    Funding for pilot demonstrations is key at this stage. Superhot rock technology development can begin today by drilling near existing geothermal fields where the earth’s heat is close to the surface.  

    More funding should also be allocated to research aimed at maturing system components, so that they can operate under high-temperature and high-pressure conditions.  

    Public funding has a role to play in early-stage R&D that would lower the risk for, and so attract, private investment. Both EU and national funding instruments could be used for this purpose. Public polling indicates that 65% of respondents are in favour of their governments investing in superhot rock.  
  1. Connect stakeholders  

    The demonstration and commercialisation of superhot rock energy will require stakeholder collaboration, knowledge-sharing and creation of consortia. These processes could be facilitated through the creation of national and EU stakeholder platforms, so as to enable collaboration at all levels. These platforms should consider and undertake specific workstreams related to superhot rock energy.  
  1. Set up an EU data repository  

    Subsurface data is critical for helping companies survey for heat and reduce the risk of well failure. National governments can play a role in funding geothermal resource mapping and exploratory drilling where such data is lacking. Data should then be harmonised and collected in a centralised EU portal that is accessible to all.   

While various EU-funded projects have already drilled to temperatures above 400˚C, the milestone of creating an end-to-end enhanced geothermal system in this environment remains unclaimed. By crafting a clear strategy, investing in R&D, bringing key stakeholders together, and making subsurface data widely available, Europe can lead the race to harness this immensely promising clean energy source.   

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