Millimeter Wave Drilling: The Key to Clean Energy Abundance

Everywhere on Earth, deep beneath the surface, there is an untapped bounty of clean energy, enough to power civilization 24/7 for millions of years. This is the potential of deep geothermal energy, using the heat of the Earth to decarbonize society. But this ubiquitous source of clean energy, buried deep within the Earth’s crust, is largely inaccessible with modern drilling technology.

Enter millimeter waves (MMWs), a portion of the electromagnetic spectrum between microwaves and infrared. Named for their wavelength measuring 1-10 millimeters, MMWs are everywhere yet invisible to the naked eye. The fingerprints of the Big Bang still linger as MMWs all around us in the cosmic microwave background. And if you’re reading this on a phone, chances are it was transmitted by 5G using MMWs.

In 2008, MIT engineer Paul Woskov had a bold idea for MMWs to unlock the true potential of geothermal energy. In his lab at MIT's Plasma Science and Fusion Center (PSFC), Woskov worked with gyrotrons, a device that produces high-power MMWs for extreme heating.

“My experience with gyrotrons for fusion energy research made me recognize the potential for geothermal,” said Woskov.

For decades, gyrotrons have been used to reach temperatures far hotter than the sun to study fusion energy. But Woskov envisioned a new application for the gyrotron: making deep geothermal energy accessible by vaporizing rock.

Not just any rock, though—tough basement rock. Earth’s crust generally has a looser and softer layer near the surface, known as sedimentary rock. Modern technology is well-adapted and economical for drilling through the sedimentary layer, optimized by the oil and gas industry. Fossil fuels, some critical minerals, water, and lower-temperature geothermal energy are all extracted from the sedimentary layer.

But beneath sedimentary rock lies the tough, crystalline basement rock. Temperatures and pressures are higher there, and the rock is more ductile than brittle. Mechanical drill bits wear down quickly and are expensive to use in basement rock, requiring frequent, costly trips to the surface for replacement.

Woskov used his gyrotron at the MIT PSFC to vaporize blocks of basement rock, such as granite and basalt, to research the potential of MMW drilling. MMWs vaporize rock with dielectric heat, which is the same fundamental principle behind microwave ovens. The MMWs are sent down a special metallic pipe called a waveguide to bombard the surface of the rock. The MMWs melt and ablate the rock at high power densities, resulting in fine, volcanic-like ash. A circulating gas then flushes the ash downhole and sends it to the surface for removal.

“Subsequent support from the [MIT] Energy Initiative and Department of Energy led to studies and experiments that showed this potential to be very promising,” said Woskov.

After more than a decade of experiments, Woskov concluded that MMWs have the unique potential to make deep geothermal energy cost-effective and available almost anywhere on Earth. Deep geothermal is up to 10x more powerful than traditional geothermal energy and exponentially more accessible by drilling with MMWs.

MMW drilling succeeds where conventional drilling does not, and vice versa. MMW drilling transmits vast amounts of concentrated energy downhole, and the circulating gas is highly effective at removing small cuttings from extreme depths. Both tasks are tall orders for conventional drilling technology.

However, conventional drilling outperforms MMWs in sedimentary rock. This is why we are building a hybrid approach at Quaise: traditional drilling in the sedimentary layer followed by MMW drilling in the basement layer to achieve deep geothermal energy at higher temperatures and greater power densities.

As Woskov says, “It will be a significant game changer to the sustainable energy equation when Quaise achieves a deep borehole in the field.”

Deep geothermal could put the world on a true path to net zero within a generation by producing more power on less land while leveraging existing infrastructure to accelerate the clean energy transition. MMW drilling is how we get there, resulting in clean energy abundance for everyone.

Energy is everything. At Quaise, we look at the big picture to see where the world is and where it needs to go. Today, fossil fuels still dominate global energy by a long shot. A smoother transition to clean energy requires a bold new vision grounded in science, scale, and speed. Join us as we explore the future of energy and the power of deep geothermal.