Raphael Thys
The deeper we go into the ground, the better are energy output from geothermal setups.
Quaise Energy, a geothermal energy spin-off from the Massachusetts Institute of Technology (MIT), is preparing to extract up to 10 times more energy by tapping into rocks at 700 Fahrenheit (375 degrees Celsius).
Conventional geothermal setups, including engineered geothermal systems (EGS), currently work at temperatures not exceeding 392 Fahrenheit (200 degrees Celsius).
As countries look to phase out fossil fuels from their energy mix, technologies such as geothermal energy have received a major boost. Unlike wind and solar energy, geothermal energy is available 24/7 and can also be generated according to demand.
Quaise Energy first made headlines nearly two years ago when it suggested switching to an innovative new technology to tap into geothermal energy. Quaise’s approach involves using microwaves to vaporize the rock and access the geothermal energy.
“MMW Drilling is advantageous because the process operates mostly independent of depth, unlike conventional drilling, and is particularly optimized for the types of rock encountered in the deep basement of the crust where high-grade geothermal heat is expected,” Matthew Houde, co-founder of Quaise Energy told Interesting Engineering in a previous interview.
Digging 6 miles into the ground
A 2006 MIT research study found that tapping into just two percent of geothermal energy stored in rocks between two and six miles (3-10 km) below the ground would provide over 2,000 times the annual energy consumption in the US.
Quaise Energy is also looking to tap into these regions where the rock is superhot, sitting at over 700 degrees Fahrenheit (375 degrees Celsius). Water seeping in at these temperatures would become supercritical and carry 3-4 times more energy than regular hot water. When brought to the surface to run turbines, this would result in up to three times more electricity generation, Quaise said in a recent press release.
Since drills used by the oil and gas industry aren’t used to working at such temperatures and pressures, Quaise is relying on its MMW drilling to get the job done. However, that only solves half the puzzle.
How will water behave?
Since no geothermal energy system has tested these depths before, Quaise is unsure how water will behave when it is introduced to these super-high temperatures. The company is researching the best models for this.
Different concepts for engineered geothermal systems, including a new approach described in a recent issue of Geothermal Energy. (Trenton Cladouhos, Quaise Energy)
Conventional systems have two ways of injecting water into them. The first is a closed-loop system in which water is introduced through a pipe, heated through a series of horizontal pipes, and then rushes out through another pipe. The other uses two horizontal wells located within a system made up of hundreds of manmade fractures in the rock.
Trenton Cladouhos, Quaise’s vice president of geothermal resource development, said in the press release that Quaise plans to further this by using a more refined approach of introducing microcracks where the two wells are connected via a “large cloud of permeability rather than large fractures.”
Quaise intends to test its model at the Newberry volcano in central Oregon, where similar temperatures can be reached at shallower depths.
“This is a model. We don’t know if the permeability due to microcracking will be enough to connect two wells in the real world. Now we need to test it and other concepts of fracturing superhot rock in the field,” added Cladouhos. “In the end, a hybrid approach involving planar fractures, natural fractures, and microfractures may be needed.”
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Ameya Paleja Ameya is a science writer based in Hyderabad, India. A Molecular Biologist at heart, he traded the micropipette to write about science during the pandemic and does not want to go back. He likes to write about genetics, microbes, technology, and public policy.