New drilling tech could tap Earth’s geothermal energy by melting through rocks

An abundant source of geothermal energy exists far, far beneath our feet, but accessing it isn’t exactly easy. Ordinarily, drilling methods are unable to break through the dense rock and high-pressure conditions encountered when trying to dig down that far. However, a new type of “enhanced” drilling system may be able to help.

As detailed by IEEE Spectrum, the Seattle-based company AltaRock Energy is developing futuristic drilling technology that could “melt and vaporize rocks” using millimeter waves. These specially designed high-frequency microwave-beam generators could enable drillers to penetrate rocks faster, at greater depths, and — every bit as importantly — at a lower cost than existing conventional drills.

According to AltaRock, a miniscule 0.1% of Earth’s heat content could handle humanity’s total energy requirements for around 2 million years. But tapping these extreme temperatures, which can reach 10,800-degrees Fahrenheit (6,000-degrees Celsius) at Earth’s core, is tough. The majority of geothermal projects drill down to depths no greater than 3 kilometers due to financial and technical challenges. As a result, geothermal energy currently makes up only around 0.2% of Earth’s global power capacity.

“Today, we have an access problem,” Carlos Araque, CEO of AltaRock affiliate Quaise, told IEEE Spectrum. “The promise is that, if we could drill 10 to 20 kilometers deep, we’d basically have access to an infinite source of energy.”

AltaRock has received a $3.9 million grant from the United States Department of Energy’s Advanced Research Projects Agency–Energy (ARPA-E) division. This covers a three-year initiative, during which scientists will test and demonstrate the high-frequency microwave beam technology at a series of ever-increasing scales. They will reportedly start with small “hand-size” samples and proceed to “room-size” slabs.

A project page for the initiative notes that: “[Research and development] will include benchtop testing, as well as larger scale demonstrations of directed [millimeter wave] drilling at unprecedented borehole lengths and power levels. A detailed modeling and simulations campaign carried out with the experimental work will provide the basis for the design of larger, commercial-scale systems.”

Partners in the project hope that it will be possible to begin drilling at real-world test sites before the grant ends in September 2022.

Hey, maybe while they’re down there they could retrieve the quadrillion tons of diamonds that reportedly exist some 100 miles below our planet’s surface — deeper than any previous drilling expedition has been before.