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Blasting Rock With Microwaves Could Unlock The Key To Geothermal Energy

A new drilling technology could unlock the key to almost limitless geothermal energy, potentially helping to wean the world off its use of fossil fuels which are contributing to the heating of the planet.

The deepest hole drilled to date – the Kola borehole – went 7.6 miles down. It took 20 years to complete because conventional equipment like mechanical drill bits can’t withstand the conditions at those depths.

Massachusetts-based Quaise Energy has been developing a technology to blast rock with microwaves that could make it easier to drill the deepest holes on Earth.

Speaking at a TEDX event in Boston, the firm’s co-founder Matt Houde said: “The total energy content of the heat stored underground exceeds our annual energy demand as a planet by a factor of a billion.

“Tapping into a fraction of that is more than enough to meet our energy needs for the foreseeable future.”

According to Quaise Energy, if holes could be dug ten miles down, temperatures can be accessed that could be used to economically produce energy everywhere on the planet.

Even deeper holes would allow facilities to heat water to temperatures where it becomes supercritical, a steam-like phase that will allow a “step change improvement in the power production per well and so cheapen the cost of energy,” Houde said.

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For the world to cure its addiction to fossil fuels, however, there will need to be hundreds of boreholes to scale up the geothermal energy facilities that will be needed.

Crucially, they can provide baseload energy which can help balance out the intermittent flows of wind and solar.

Geothermal is also “the perfect energy source to take advantage of the largest workforce in the world, the oil and gas industry,” Houde added. That industry has “11 million jobs in the US alone and a skill set that is exactly what’s needed for geothermal to rapidly scale.”

Quaise is working to replace conventional drill bits with millimetre-wave energy which can melt and then vaporise rock to create ever-deeper holes.

The technique was developed at MIT over the last 15 years. In the lab, scientists have demonstrated that millimetre waves could drill a hole in basalt. The gyrotron machine that produces the millimetre-wave energy is not new and has been used for around 70 years in research toward nuclear fusion as an energy source.

The Quaise technique also takes advantage of the conventional drilling technologies developed by the oil and gas industry. The company will use these to drill down through surface layers to basement rock before switching to the millimetre wave technology that can power through from that point on.

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Houde explained that millimetre waves “are ideal for the hard, hot, crystalline rock deep down that conventional drilling struggles with.” They are not as efficient in the softer rock closer to the surface, but “those are the same formations that conventional drilling excels at.”

The firm said it still needs a better understanding of rock properties at great depths and the supply chain for gyrotrons needs to be improved.

The equipment currently available is optimised for specialised one-off projects in fusion research, but for deep geothermal applications they must be produced in quantity and be robust and reliable in a field environment.

Source: E&T


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