Superhot Rock Geothermal
An Energy Revolution in the Making
Superhot rock geothermal energy is a visionary technology deserving of investment, and yet almost entirely unrecognized in the decarbonization debate. It has the potential to meet long-term demands for zero-carbon, always-on power, and can generate hydrogen for transportation fuel and other applications. Unlocking the potential of this energy source could expand our options and potentially carve a path forward to replace fossil fuels.
Superhot rock energy could support rapid global decarbonization
Rapid energy innovation is clearly needed now to meet the immense climate challenge. Vast amounts of reliable and dispatchable (always available) zero-carbon power will be needed to support the demand for access to energy by the growing global population. At CATF, we envision a future where superhot rock geothermal could play a big role in transforming the energy system as a vital part of a prosperous, carbon-free global economy.
How does superhot rock geothermal work?
In a superhot rock system, water is injected deep into hot fractured rock, heated, and returned to the Earth’s surface as steam that can be used to produce power in electric turbines or to generate hydrogen using a high temperature process.
Superhot rock geothermal could have a few distinct advantages over other energy sources. It is projected to be affordable, requiring little area to produce large amounts of energy (high energy density) due to the very large amount of energy that can be produced per well. Superhot rock is expected to produce five to ten times as much energy as the power produced from one of today’s commercial geothermal wells.
- Superhot rock geothermal “mines” deep at very high temperature and heat in the Earth’s crust. This contrasts with today’s small (~15 GW globally) commercial geothermal industry that typically depends on upwelling of hot groundwater at locations with high near surface heat.
- Superhot rock geothermal injects water into superhot dry crystalline rock by opening existing fractures at a depth where water is so hot it possesses properties of both liquids and gasses, allowing injected water to travel rapidly through existing rock fractures and gather very large volumes of heat energy.
- Production wells bring this steam energy to the surface to produce power in electric turbines and/or to generate hydrogen.
For the last few years, CATF’s experts have researched this new zero-carbon energy technology and the opportunities we have to scale it in an affordable and broadly deployable way. We are working to build momentum behind this dispatchable, energy-dense resource, and to add it to the global decarbonization debate as a long-term strategy for meeting energy demand growth in a world without fossil fuels.
CATF’s vision is to rapidly scale superhot rock from demonstration to initial commercialization in this decade, and with parallel development of deep drilling methods, scale to “geothermal everywhere” in the 2030s. Superhot rock geothermal can be demonstrated today in areas with high near-surface heat, using existing technology, while adopting strategies and innovations from unconventional oil and gas development, such as intensive drilling campaigns, to accelerate deployment, scale and adoption. Future energy drilling innovations could allow accessing the superhot conditions in much deeper wells in mid-continental regions currently without geothermal resources.
The value of superhot rock geothermal
- Competitive power
- Endless Earth energy resource
- Dispatchable, meaning always on, baseload power
- Energy dense, high energy with a small surface footprint
- No fuel cost
- Zero greenhouse gases
- Pivots fossil energy to geothermal across the globe
- Potential to repower fossil power plants
- Generate carbon-free hydrogen without carbon as a transportation fuel
- Accessible worldwide with super deep drilling innovation
- Significant engineering advancements required but does not depend on scientific breakthroughs
- Energy security and modernization
Where can superhot rock be developed?
The map below shows where wells have been drilled into superhot conditions, as well as some global projects investigating superhot rock. The darker reddish areas are generally regions where superhot rock is shallower, in the realm of current drilling technologies, and could be initially demonstrated and commercialized. The remainder of the world should be able to tap into superhot rock as super-deep drilling innovation allows.
What are the opportunities and challenges?
Key innovations are needed to rapidly deploy superhot rock energy, including deep drilling and heat reservoir development. While technically challenging, these are achievable innovations that could be quickly developed with adequate funding. One key challenge is developing fractured heat reservoirs that injected water can pass through to production wells. This will require methods that identify existing fractures that can be stimulated and injected without causing seismic activity. Research is underway in Japan and in other laboratories worldwide to develop aseismic methods in this more plastic superhot rock.
Successful commercial energy drilling enables global access to superhot rock geothermal energy. In the photo, energy is transformed into a torch that can soften or melt rock without mechanical grinding. Successful development of these technologies off the potential tro significantly reduce the time-consuming removal of superlong drill strings from deep wells to change worn drill bits. Such additional oil and gas innovations as skid rigs that can successively drill multiple wells from from a single pad, and directional drilling provide further efficiencies, cost reductions and better targeting of resources.
The path forward
Superhot rock technology development can begin today by drilling near existing geothermal fields where the Earth’s temperature is very hot near the surface. With success, intensive drilling campaigns can begin to develop superhot rock beyond commercial fields. From there, energy drilling technology can target deeper rock and ancient granites that are hot from radiogenic decay. As energy drilling matures, very deep systems can be tapped into, expanding superhot rock geothermal globally.
|Phase 1||Phase 2||Phase 3|
|Demonstration and Innovation
Superhot rock geothermal power production pilot projects using mechanical drilling methods in volcanic regions at depths of 3-7 km; development of methods, tools, and technologies for extreme heat and pressure conditions; energy drilling field demonstrations; parallel successes and learning in hot dry rock and sedimentary geothermal projects; possible high-temperature hydrogen cogeneration tests.
|Initial Commercial Deployment
expansion of superhot rock geothermal in hot crustal regions (e.g., the western U.S., Pacific Rim, sub-Saharan Africa); development of mid-depth systems (e.g. up to 10 km), commercialization of energy drilling.
Energy drilling unlocks super-deep geothermal across the globe at depths of 10-20 km.
Meet our experts in superhot rock geothermal
If you have questions or are interested in learning more about our Superhot Rock Geothermal program and some of the latest innovations in this space, or would like to support our efforts in advancing this new technology, contact Chief Geoscientist Dr. Bruce Hill.
Superhot rock geothermal FAQs
What is superhot rock geothermal?
Superhot rock geothermal is a high-energy-density, zero-carbon, always-available energy source that could potentially be accessed worldwide for baseload power, heat, hydrogen production and industrial process energy. Superhot rock geothermal could be economically competitive with most zero-carbon technologies and capable of being deployed rapidly in much of the world. Superhot rock geothermal promises a small environmental footprint and could potentially repower or replace many existing fossil fuel energy facilities.
Where can superhot rock geothermal be developed first?
Deploying superhot rock and “geothermal everywhere” globally will require innovative new technologies that can improve drilling rates and cost-effectively reach superhot resources in hard crystalline rock at depths of 7-15 km (~4-9 mi). Currently available mechanical drilling methods can and are being used to drill to depths of 3-7 km (~2-4 mi) to access relatively shallow superhot rock.
How is superhot rock energy different from commercial geothermal power?
Conventional geothermal power is produced from hydrothermal fluid at temperatures between 100-300°C. In contrast, superhot rock energy will inject water and circulate it through a fractured heat reservoir and pump it to the surface. This process will heat and utilize water that has reached conditions exceeding 400°C. Water above this temperature is in the “supercritical” state, which has different advantageous properties such as being much more fluid and carrying higher heat content such that superhot rock systems would bring far more energy to the surface. Superhot rock is widely considered to be the “holy grail” of geothermal energy!
What is geothermal energy and how has it evolved?
Geothermal energy is harnessed from the internal heat of the earth. Geothermal power is produced by drilling deep into the earth where it gets hotter as you go down. Where heat is shallow, such as regions with volcanic activity, groundwater is naturally heated and the resulting steam is captured and power generated by a turbine at the surface. Geothermal heat can also be used to provide hot water and district heating. Iceland is entirely powered by geothermal energy! The first geothermal power was created in Italy early in the 20th century. But as of 2018 there was only 15 GW of geothermal power in the world. That’s equivalent to the same number of large fossil plants. Today’s commercial geothermal industry is small because it is limited only to regions with shallow heat.
What is EGS?
Recent innovations in geothermal energy are beginning to move away from natural steam based systems toward engineered geothermal systems (EGS) in hot dry rock (HDR) will have a much wider geographic use. Early work on such systems began at Los Alamos National Laboratory in the 1970s.
Superhot rock geothermal will be engineered hot dry rock, but in “superhot” rock conditions above 400 degrees celsius. In superhot rock systems, fresh water will be pumped down an injection well , through natural fractures in crystalline rock and be produced in a production well, pumped through a turbine, condensed and reinjected as part of a largely closed loop system. No carbon dioxide will be emitted as part of this process.
Is supercritical geothermal energy the same thing as superhot rock geothermal?
Yes. The term “superhot rock” is a less technical term for engineered supercritical water based geothermal systems. Supercritical water exists in a superheated state and has more heat and is far more fluid than hot water or steam. Therefore it can bring far more heat to the surface– an estimated 5-10x today’s commercial wells– giving it the potential to be competitive with today’s costs for power.
This high energy potential has been demonstrated in Iceland where the Iceland Deep Drilling Project’s Krafla borehole produced natural superhot water at 452°C and an estimated 36 megawatts of energy (MWe) production potential. AltaRock Energy projects that 25-45 MWe could be produced from a single production well at its Newberry superhot rock geothermal project) In comparison, a typical commercial hydrothermal geothermal project produces about 7-8 MW per well. Also for comparison, the Reykjanes geothermal field in Iceland–perhaps the hottest producing field in the world at 290-320°C–has 12 wells producing a total of 100 MWe from 2 turbines. There are over 2 dozen wells that have drilled into superhot rock around the world, but no power has yet to be produced.
Does superhot rock geothermal produce CO₂?
It does not. It will be an entirely carbon free form of energy.
Is superhot rock geothermal a renewable resource?
Yes, for the purposes of human energy production the Earth’s heat is infinite (although scientists predict that the world’s geothermal heat will run out in about 5 billion years!) Earth’s geothermal heat is a huge potential zero-carbon energy resource – Alta Rock Energy predicts that just 0.1% the earth’s internal heat could sustain the world’s energy demand for the next 2 million years. A 2007 report by MIT researchers estimated that the U.S. geothermal resource is 2,000 exajoules– two thousand times U.S. primary energy production.
Geothermal heat is a consistent dispatchable “baseload” source of energy. This means that unlike other renewable resources, geothermal energy doesn’t require the use of battery storage or fossil fuel supplementation and is consistently available for distribution. Deep drilling could provide the opportunity to access superhot rock geothermal worldwide for modernization and energy security.
Can superhot rock geothermal produce hydrogen?
Superhot rock high temperatures could facilitate generating hydrogen, an alternative fuel that could help decarbonize mobility, space heating and some industrial processes. Hydrogen is also a potentially promising feedstock and energy source for producing zero-carbon ammonia—which is emerging as a major global zero-carbon liquid fuel. A Lucid Catalyst analysis produced for Clean Air Task Force estimates that SHR energy could produce hydrogen competitively.
How much do we expect superhot rock geothermal to cost?
Clean Air Task Force commissioned Hot Rock Energy Research Organization (HERO) and Lucid Catalyst to preliminarily estimate the “levelized cost of energy” for future mature (“nth of a kind”) power plants . Results suggest mature SHR will be competitive at $20-35 per MWh (Levelized cost of energy (LCOE) is a standard measurement in the energy industry that is used to compare the cost of energy sources, and is calculated by dividing the lifetime cost of a power plant by the total energy produced by that plant.)
What’s needed to speed the development of superhot rock geothermal?
Key innovations are needed to deploy superhot rock energy widely, including deep drilling and reservoir development in very high temperature and pressure conditions. While technically challenging, these are achievable innovations that could be developed relatively quickly with adequate funding—as was the case with unconventional fossil resource development. Indeed, oil and gas expertise should play a major role in commercializing and rapidly deploying superhot rock geothermal. An intensive drilling and resource development program by well-funded consortia that include oil and gas industry players could provide the knowledge and innovation needed to develop and rapidly commercialize superhot rock geothermal across the world.
What is energy drilling?
Deploying superhot rock and “geothermal everywhere” globally will require innovative new technologies that can improve drilling rates and cost-effectively reach superhot resources in hard crystalline rock at depths of 7-15 km (~4-9 mi).
Energy drilling should significantly improve drilling speed and economics, thus further enabling economic access to greater depths. Laboratory tests demonstrate that such non-mechanical energy drilling methods can soften or melt rock through energy directed downhole.
Two principal energy drilling methods are currently being tested: plasma drilling and millimeter wave drilling (see box). GA Drilling (Slovakia) is preparing to test its Plasmabit drill in the field in the coming year, while Quaise (USA) is developing a millimeter wave drill. ENN (China) has evaluated both plasma and millimeter wave energy drilling methods in its superhot rock geothermal laboratory.
What are the next steps?
A key first step to commercial superhot rock geothermal will be moving three to five superhot rock geothermal power demonstrations forward in the next five years. Successful proof-of-concept power production demonstrations will “wake up” the energy community and spur investment in commercial demonstrations. To evolve superhot rock to “geothermal everywhere”, initial demonstrations should take place in shallow hot dry rock settings without natural hydrothermal steam resources. One such superhot rock geothermal project (by AltaRock Energy) is being planned in Oregon.
Following successful pilot demonstrations, commercial demonstrations must then begin producing power at grid scale (e.g., 100+ MW). These projects must also move to progressively deeper resources to realize the promise of geothermal everywhere. The innovations needed to make deeper resource extraction may be accelerated by intensive drilling campaigns designed to catalyze rapid learning-by-doing. Then as next-generation superdeep drilling methods (energy drilling) are commercialized, superhot rock geothermal can progress from shallow hot regions to deep continental areas.
Commercializing superhot rock geothermal will require the resources of the geothermal industry, government laboratories, academic institutions and the oil and gas industry. Substantial early government investments can “jumpstart” the process of commercializing superhot rock geothermal energy by providing drilling campaign incentives in promising superhot rock geothermal locations that differ in depth and geology, as well as by enhancing cross-pollination among international projects. The goal should be to learn as much as possible through actual well and reservoir development activities in different subsurface conditions and so on as soon as is practical.