Energy from the deep – the next big thing
In school, we all learned that Earth’s liquid core has a temperature of around
5,000 °C (9,000 °F), so it’s only logical that the deeper you drill the hotter it gets. But in many countries the utilization of this deep heat – primarily in volcanic regions – is still in its infancy. For instance, in Germany, a new-energies trailblazing country, there are just three such power stations in the Upper Rhine Plain using 97 °C (207 °F) hot water from a depth of 2,500 (8,200) to 3,500 meters (11,500 feet) to generate heat and electricity.
Attempts to tap into deeper and therefore hotter water-bearing beds have literally gotten stuck: In 1995, after twelve years, Germany’s most ambitious deep-drilling project had to be stopped at a depth of 9,101 meters (29,859 feet) because under the high ambient pressure and the prevailing temperatures of 260 °C (500 °F) there, the rock turns into a kind of viscous custard that puts up more and more resistance. Another project, on the Russian Kola Peninsula, was stopped as well, after nearly 20 years of work, at a depth of 12,289 meters (40,318 feet). All that’s left of it is a rusty bolted cover on the world’s – so far – deepest hole.
Geothermal energy completely rethought
Actually, using the incredible heat in Earth’s interior would pay off because just 0.1 percent of the presumed geothermal energy could cover the worldwide energy demand for 20 million years, according to calculations of the Massachusetts Institute of Technology (MIT).
That’s why “the next big thing” in terms of green energy is now being ushered in. Quaise appears on the stage: the people behind the MIT spin-off, all of them experts in plasma research and fusion energy, intend to unlock at least a tiny portion of this geothermal potential. In pursuit of this goal, they’ve completely reimagined geothermal and its application. Their plan is to access 500 °C (932 °F) hot water at a depth of 20 kilometers (12.4 miles) that’s in a supercritical state due to the extreme pressure and to bring it to the top.
of the entire energy consumption is fed into heat sources for houses, industry and other uses, according to the International Energy Agency (IEA). At the moment, only around 10 percent of the thermal energy is supplied by renewable sources – a percentage that will double by 2030, the IEA projects. Many scientists feel that such progress is too slow. They demand a ban on the installation of fossil-fuel heating systems to start as early as in 2024 if the German climate goals are to be achieved by 2045. Geothermal energy is a key to achieving these targets.
of its entire thermal demand (converted to 300 TWh) Germany, as an industrial country, could cover by using currently available or upcoming hydrothermal technologies for deep geothermal direct use alone or in combination with large-scale heat pumps. Estimated investment volume: 140 to 175 billion euros. Hot rock formations (petro-thermal geothermal), seasonal underground heat accumulators and surface geothermal energy for heating and cooling buildings in the construction and housing sectors offer additional thermal potential.
Source: Roadmap Tiefe Geothermie für Deutschland
An unexpected treasure
The fact that the deep water pumped for the three geothermal stations Landau, Insheim and Bruchsal in the Rhine Valley contains lithium has been known for a long time. Filtered out and densified, the metal can be used for traction batteries in the electric mobility sector. The lithium from these three sites might be able to cover eight percent of the European demand – without resulting in any additional environmental burden of the kind that’s incurred in lithium mining in Bolivia or Chile.
To tap into this humongous energy source, U.S. specialist Quaise is thinking along new lines, using previously known, extremely powerful microwave oscillator technology. By means of electromagnetic waves in the millimeter range and frequencies of up to 300 gigahertz these so-called gyrotons can generate temperatures of up to 150 million °C (302 million °F) – enough to pulverize even the hardest rock. Using argon gas, the particles are then blown upward while the rock around the “bore hole” fuses at these extreme temperatures and automatically seals off the shaft.
Since this technology, following short conventional drilling, basically just requires a pipe to be pushed down into the ground, there’s no need for extremely time-consuming handling of drill pipes. While it took the Russians 20 years to penetrate the rock down to 12 kilometers (7.5 miles) in the Kola project, Quaise plans to achieve that in about 100 days using a 1-MW gyroton advancing at a rate of 70 meters (230 feet) per hour and then continuing to work its way forward. By comparison, the German geothermal power station projects operating with maximum drilling depths of 3,500 meters (11,500 feet) merely scratched the surface.
If the effort to tap the extremely hot deep water proves successful it will be followed by the application stage – in the form of an amazing re-powering plan. Quaise’s concept involves a comprehensive advantage, a revolution of green energy generation, because the utilization of the super-hot deep water doesn’t require the construction of new powerplants. The idea is to convert existing facilities and to continue using their technology for power generation.
Whether they’re fossil, nuclear or solar, powerplants are actually nothing but hot-water boilers. They generate heat and use it to turn water into steam driving power-generating turbines. Quaise’s plan – aside from technological challenges yet to be mastered in the field – is intriguingly simple: hot water pumped up from great depths would be fed directly into any available powerplant and drive the turbines there. That would make coal, gas, oil and uranium rods superfluous and the energy per se would be completely carbon-neutral. Theoretically, any power station previously heated by conventional fuel could have its own source of deep water for emission-free generation of electricity and heat.
Obviously, in volcanically active regions very hot water could be accessed in much simpler ways and much closer to Earth’s surface, like Iceland has been doing. But in most cases, such quasi-natural hot water sources are too far away from consumers, whereas driving an ultra-deep hole into the ground should be feasible anywhere with Quaise’s technology. It’s assumed that this would apply to 70 percent of Earth’s surface.
The realization of Quaise’s concept would result in several advantages. Electric power would be produced not only with zero emissions but conventional oil-, gas- or coal-fired powerplants that would have to be shut down for climate protection reasons could continue to operate. Because these plants are already integrated into power grids, there’d be no need for establishing corresponding infrastructure either, as required, for instance, for hydrogen as an energy source.
In response to critics, the utilization of ultra-hot deep water can score in terms of a totally different aspect as well. Unlike with solar farms or wind farms, the space required for unlocking this potential is minimal. Nothing would impair the landscape, which should clearly simplify approval processes. Another crucial advantage of geothermal over solar and wind energy is its baseload capability – Earth’s heat is not subject to any fluctuations. The risk potential that the utilization of geothermal power entails is minimal as well. What’s critical is the actual drilling operations that may cause geological shifts in the ground. “If the drilling has been successful, geothermal energy should be assessed very positively not only from an economic but also from an environmental point of view,” writes Lars Jaeger in his book “Wege aus der Klimakatastrophe” (“Ways out of the Climate Catastrophe”). Quaise even excludes this potential hazard for its microwave drilling operations.
"If the drilling has been successful, geothermal energy should be assessed very positively not only from an economic but also from an environmental point of view."Book author Lars Jaeger (“Ways out of the Climate Catastrophe”)
In an extensive report, the World Bank points out another issue: Some geothermal power stations that are operating already have a worse climate gas footprint than coal-fired powerplants because drilling into the Earth may cause carbon dioxide and methane that’s bound there to escape. That’s another challenge to be mastered by Quaise and other pioneers in this field.
To accomplish the move toward a new geothermal future from pure theory and research into the tough reality of field operations, Quaise raised funding in the amount of 63 million US dollars at the beginning of 2022. The U.S. Department of Energy is on board as well. Any support is as welcome as it is necessary because gyroton drilling projects are “very difficult technological undertakings” , says Quaise’s co-founder Carlos Araque. To his surprise, he’s also found support in the oil and gas industry. “These companies are starting to understand that they need to embrace the [green] energy transition,” he told “MIT Technology Review”.
A joint roadmap of the German Fraunhofer Societies and the Helmholtz Association also recommends a broad alliance of the political, business and academic communities for deep geothermal, like in the case of driving hydrogen technologies. That includes balancing the risks for private-sector companies and local governments tackling the exploration of deep geothermal energy. In addition, capital investment grants for key technologies are necessary, including drilling systems and pumps, high-temperature heat pumps and large-scale heat accumulators. Moreover, large-scale utilization of geothermal energy requires cross-sector integration and broadly designed combined heat networks.
In spite of all challenges Quaise continues driving its idea: initial demonstration drillings down to depths between 100 (328) and 1,000 meters (3,280 feet) are planned to start in 2024. Provided that they produce the expected success, the conversion of the first power station to deep geothermal energy is targeted for 2028. It remains to be seen whether that facility will be able to deliver energy at market-prices. Hence the road toward using deep geothermal energy is still as long as it’s deep.