An introduction to the next clean energy frontier: Superhot rock geothermal and a vision for firm, global clean energy
This blog is part of a series exploring and explaining the science behind next-generation geothermal energy, with a special focus on superhot rock geothermal, through a curated tour of influential technical and academic papers. This blog highlights key features of CATF’s 2022 report, Superhot Rock Energy: A Vision for Firm, Global Zero-Carbon Energy.
Next generation geothermal systems, one of the few clean energy sources capable of delivering reliable, 24/7 baseload power, are finally having their moment in the spotlight. As we enter the new year, interest in next-generation geothermal is on the rise. In the U.S., momentum is growing in media and policy circles following the 2024 elections, with geothermal emerging as a promising bipartisan opportunity. Meanwhile, the European Union (EU) Member States, as well as the European Parliament, recently called for a dedicated action plan to accelerate the deployment of geothermal energy, including new innovative technologies. Adding to this wave of interest, the International Energy Agency (IEA) recently released its first special report on geothermal, underscoring its potential to meet up to 15% of global electricity demand growth by 2050, driven by continued technological advancements and cost reductions.
The IEA report also highlights the significant promise of superhot rock geothermal (SHR), a form of next-generation geothermal technology capable of tapping subsurface temperatures exceeding 400 °C to deliver substantially higher energy yields. Clean Air Task Force’s (CATF’s) modeling indicates that harnessing just 1% of global SHR potential could generate 63 terawatts (TW) of clean firm power—eight times more than the world’s current total electricity production.
Given this renewed focus on geothermal energy and the promise of SHR, it’s worth taking a step back to explore the big picture by revisiting key insights from CATF’s 2022 report, Superhot Rock Energy: A Vision for Firm, Global Zero-Carbon Energy. This report was an early wide-reaching overview of the key features that set SHR apart from conventional geothermal and lower temperature next-generation geothermal resources, and it outlines how SHR could play a pivotal role in scaling up reliable, carbon-free energy worldwide.
Today’s geothermal capacity is a fraction of its potential.
Today’s conventional geothermal systems have a global capacity of only 16 gigawatts (GW) of power (less than 0.4% of the total installed global power) and are geographically limited to regions where heat is concentrated near the Earth’s surface – like in volcanic regions or regions where the Earth’s crust is thin, such as the Basin and Range region (i.e., western U.S. and northern Mexico) or the East African Rift (i.e., from the horn of Africa, south to Kenya and Tanzania, and west to the Democratic Republic of the Congo). When limited to areas around the globe where shallow heat, water and fluid pathways are available, the industry has not had a lot of options for where geothermal energy can be produced.
Next-generation geothermal systems can significantly expand the global geothermal resource capacity.
With next-generation geothermal, we don’t need to focus just on localized regions where heat is concentrated near the Earth’s surface. Instead, in enhanced geothermal systems (EGS), a type of next-generation geothermal, hot dry rock at depth is enhanced to create a geothermal system. This is done by injecting water beneath the Earth’s surface to create fractures and then cycling water through the system to heat up the water and create steam for energy production (See Fig. 1). In another form of next-generation geothermal, known as closed loop geothermal systems (CLGS), fluids are circulated through a network of interconnected wellbore loops beneath the surface, forming a so-called “closed loop.”
The 2019 Department of Energy’s GeoVision report estimates that the U.S. could generate more than 5,000 GW of electricity, or around 5 times the 2016 U.S. installed utility-scale generation capacity, through next-generation geothermal energy resources.
Superhot rock geothermal could generate up to 10 times more energy than a typical geothermal well.
Superhot rock geothermal is a type of next-generation geothermal that focuses on regions where water can be heated to greater than 400 °C (see Fig. 2).
The 400°C temperature is the key aspect of the “super” in superhot rock, which causes water to be heated to its supercritical point. The supercritical aspect of SHR causes water to be extra energy dense, which allows more energy to be generated with fewer wells. Evidence from a test well drilled by the Iceland Deep Drilling Project suggests that an estimated 36-50 MW of energy could be produced from a single SHR well, which is approximately 5-10 times that of a typical commercial geothermal well.
Higher temperatures also significantly increase thermal efficiency, as shown by the Carnot cycle. As an example, geothermal systems operating at 150-180 °C achieve about 12% electricity conversion efficiency, while concentrated solar power (CSP) systems at 400 °C reach nearly 40% and CSP systems at 1,300 °C can achieve close to 60%. This increase in thermal efficiency translates to more economical operations by maximizing enthalpy per unit mass and generating more energy from the same mass flow rate.
This high energy density coupled with an increase in thermal efficiency also allows for SHR to have a smaller environmental footprint than many other sources of electricity including coal, natural gas, solar, and wind (see Fig. 3). Furthermore, fuels with a higher energy density enable the design of more compact power generation facilities. These high output, smaller plants can be more cost-effective to build and maintain, and they can be situated closer to demand centers, reducing transmission losses.
Furthermore, given the high energy density of SHR resources, it is expected to be cost competitive with other zero-carbon and dispatchable generation technologies (e.g., coal and natural gas) at $20-$35 per MWh, which is also below the U.S. average market power price of approximately $40 per MWh (See Fig. 4).
Although drilling and reservoir development costs are expected to be high for first-of-a-kind projects, costs are expected to decline through the development of Nth-of-a-kind projects, just as we saw with the deep cost reductions that occurred in the development of unconventional shale oil and gas projects and the development of wind and solar technologies.
Unlocking superhot rock geothermal is achievable through investment and innovation.
While no SHR projects have been successfully deployed in dry rock conditions, the global drilling and geothermal community has successfully reached 400 °C over two dozen times, demonstrating an ability to operate at these high temperature and pressure conditions. Furthermore, there are over 20 projects that have demonstrated the ability to extract heat from dry rock conditions. The future of SHR looks promising, provided we can achieve crucial engineering advancements that combine next generation geothermal practices in dry rock conditions with higher temperature resource targets. These include advancements in rapid ultra-deep drilling methods, heat resistant well materials, and deep reservoir development in hot dry rock—challenges that are primarily engineering in nature rather than scientific breakthroughs. To overcome these challenges, we will need to see collaboration between geothermal, oil and gas, and tech companies. We need successful pilot demonstrations, which will be key to attracting the large-scale investment needed to advance SHR deployment.
Progress has already been made to demonstrate the potential of next-generation geothermal and SHR since CATF’s 2022 report, including:
- Successful stimulation and circulation tests in 2024 at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) site
- Significant cost reductions from Fervo Energy’s drilling operations, which showed a 70% year-over-year reduction in drilling times at its Cape Station project
CATF also released a series of reports on where future research, development, and testing is needed to bridge the gaps to successful commercialization of SHR. The reports focus on heat extraction, power production, drilling, well design and construction, and siting and characterization.
What’s next?
Geothermal energy has made significant strides since CATF highlighted the potential of superhot rock geothermal in our 2022 report. With the innovative technology poised to play a transformative role in the global energy system, CATF is leading efforts to elevate SHR’s profile, accelerate its deployment, and create the right policy and market conditions for its success. Through these and other efforts, SHR could rapidly scale from pilot demonstrations to early commercialization in the 2030s and, with parallel advancement of deep drilling methods, achieve “geothermal everywhere” by 2050. Stay tuned for more from CATF as we push forward with bold research and initiatives to scale SHR and realize its full potential.
This blog is part of a series exploring and explaining the science behind next-generation geothermal energy, with a special focus on Superhot Rock Geothermal. Through a curated tour of influential technical and academic papers, the series aims to provide a fresh perspective from a geoscientist entering the geothermal industry. The goal is to share my learning journey and encourage collaboration around these groundbreaking solutions, which are critical to achieving a clean energy future. Whether you’re new to geothermal or looking to deepen your knowledge, I hope this series offers valuable insights into this fast-evolving field.
