Geo-Energy: Millimeter-Wave Drilling to Unlock Deep Geothermal Power

Deep within the Earth lies a virtually inexhaustible source of clean energy, a thermal reservoir with the potential to power human civilization for millennia. This is the promise of geothermal energy, the heat generated and stored in the Earth's core and mantle. However, tapping into the most powerful forms of this energy, located deep within the planet's crust, has been a persistent challenge. Conventional drilling technologies, honed over decades in the oil and gas industry, falter in the face of the extreme temperatures and pressures found at these depths. Now, a revolutionary technology known as millimeter-wave drilling is poised to shatter these barriers, potentially unlocking a new era of abundant, clean, and accessible energy.

The Geothermal Imperative: A Vast, Untapped Resource

Geothermal energy originates from the radioactive decay of elements like uranium and thorium in the Earth's core, as well as residual heat from the planet's formation. This heat radiates outwards, warming the layers of the Earth's crust. For centuries, humans have utilized this energy where it naturally surfaces in the form of hot springs and geysers. Modern geothermal power plants harness this heat, typically by drilling into underground reservoirs of hot water or steam to drive turbines and generate electricity.

However, these conventional geothermal resources are geographically limited, confined to areas with specific geological conditions. The true prize lies deeper, in what are known as enhanced geothermal systems (EGS) and, even further, in superhot rock geothermal. The U.S. Department of Energy estimates that with technological advancements, geothermal energy capacity in the United States could grow from 4 gigawatts (GW) today to 90 GW by 2050, with some projections reaching as high as 300 GW. On a global scale, the potential is staggering. The International Energy Agency (IEA) suggests that the full technical potential of next-generation geothermal systems is second only to solar PV among renewable technologies and could meet global electricity demand 140 times over. Just 0.1% of the Earth's heat content could supply humanity's total energy needs for 2 million years.

Harnessing this deep geothermal energy offers significant advantages. Unlike solar and wind power, which are intermittent, geothermal energy provides a constant, baseload power source, available 24 hours a day, 7 days a week. Geothermal plants also have a small physical footprint, consuming less than 1% of the land area required by wind or solar for the same maximum output. This makes it a reliable and space-efficient solution for a clean energy future.

The Limits of Conventional Drilling

The primary obstacle to accessing this vast energy resource has been the limitations of conventional drilling technology. Traditional rotary drilling, which involves physically grinding through rock with a drill bit, becomes increasingly difficult and expensive at greater depths. The extreme conditions encountered in deep geothermal reservoirs—temperatures exceeding 300°C (572°F) and immense pressure—wreak havoc on drilling equipment.

Key challenges of conventional deep drilling include:

Extreme Temperatures and Pressures: At depths of 3,000 to 5,000 meters, temperatures can surpass 300°C, and pressures can reach hundreds of bars. This heat can damage sensitive electronic components in drilling equipment, such as Measurement While Drilling (MWD) sensors, and degrade the drilling fluids used to lubricate and cool the drill bit.
Hard and Abrasive Rock Formations: The crystalline basement rock found at these depths, such as granite and basalt, is incredibly hard and abrasive. This leads to rapid wear and tear on even the most durable drill bits, such as those made from Polycrystalline Diamond Compact (PDC). Consequently, drilling progress slows significantly, and frequent, time-consuming "trips" are required to replace worn-out bits.
Drilling Costs: The combination of slow penetration rates, equipment failure, and the need for specialized materials and fluids means that the cost of drilling increases exponentially with depth. Drilling can account for at least half the total cost of a geothermal project.
Wellbore Instability: The high temperatures and pressures can lead to wellbore instability, and managing the drilling process becomes increasingly complex.

These limitations have effectively capped the depth of most geothermal wells at around 2 to 3 kilometers, restricting access to lower-temperature resources and preventing the widespread adoption of geothermal power. The Kola Superdeep Borehole in Russia, which took 20 years to reach a depth of 12.3 kilometers, stands as a testament to the immense challenges of deep mechanical drilling.

A New Dawn: Millimeter-Wave Drilling

Enter millimeter-wave (MMW) drilling, a groundbreaking technology that promises to overcome the limitations of conventional methods. This innovative approach, born out of nuclear fusion research at the Massachusetts Institute of Technology (MIT), uses directed energy to vaporize rock rather than physically grinding it.

The core of the technology is the gyrotron, a device that generates high-power beams of millimeter waves—a portion of the electromagnetic spectrum between microwaves and infrared light. These energy waves, with frequencies between 30 and 300 gigahertz, are guided down a borehole through a metal pipe called a waveguide. When the MMW beam strikes the rock at the bottom of the hole, it heats the rock from within through a process called dielectric heating—the same principle used in a microwave oven. This intense, localized heating causes the rock to melt and vaporize, a process known as spallation.

A circulating gas, such as argon or nitrogen, is then pumped down the waveguide. This gas serves two critical functions: it cools the vaporized rock, causing it to solidify into fine, ash-like particles, and it then flushes these particles out of the borehole to the surface.

One of the key figures in the development of this technology is Dr. Paul Woskov, a senior research engineer at MIT's Plasma Science and Fusion Center. After more than a decade of experiments, Woskov and his team demonstrated that MMWs have a unique potential to make deep geothermal energy cost-effective and accessible almost anywhere on Earth. An unexpected discovery from these experiments was that hot molten rock absorbs MMW energy far more efficiently than it does the infrared radiation from lasers, another form of directed energy drilling that has been explored. This superior energy absorption makes MMW drilling a more efficient and potentially more economical option.

The Quaise Energy Revolution

The commercialization of millimeter-wave drilling is being spearheaded by Quaise Energy, a startup spun out of MIT in 2018. Quaise's mission is to unlock the vast potential of superhot geothermal energy by drilling deeper than ever before. The company plans to drill boreholes up to 20 kilometers (about 12.4 miles) deep, reaching temperatures of up to 500°C (932°F).

At these depths and temperatures, water enters a supercritical state, where it is neither a liquid nor a gas but possesses properties of both. Supercritical water can carry up to ten times more energy than the hot water used in conventional geothermal plants, dramatically increasing the power output of a geothermal well. This would allow a single geothermal plant to generate hundreds of megawatts of power, rivaling the output of large fossil fuel power plants.

Quaise Energy is developing a hybrid drilling approach. Conventional rotary drilling will be used to penetrate the upper layers of sedimentary rock, where it is more efficient. Once the drill reaches the hard, crystalline basement rock, the system will switch to millimeter-wave technology to continue drilling to the target depth.

This hybrid system offers several advantages:

Increased Speed and Reduced Cost: MMW drilling is expected to be significantly faster than conventional drilling in hard rock, with the potential to increase drilling speeds by a factor of ten or more. This would drastically reduce the time and cost associated with drilling deep wells, with Quaise aiming to complete boreholes in about 100 days. The cost of MMW drilling is expected to increase linearly with depth, not exponentially like conventional methods.
No Contact, No Wear: Because MMW drilling is a non-contact method, there are no drill bits or other downhole mechanical components to wear out and replace, eliminating the need for frequent and costly "trips".
Vitrified Wellbore: As the MMW beam vaporizes the rock, it also melts the walls of the borehole, creating a glassy, vitrified lining. This lining seals the borehole, preventing fluid loss and improving well integrity. This vitrification could reduce operational costs by up to 30%.
Leveraging Existing Infrastructure: A key part of Quaise's strategy is to repurpose existing fossil fuel power plants. The company plans to drill geothermal wells on the sites of these plants and use the geothermal steam to power the existing turbines and connect to the established grid infrastructure. This approach could accelerate the transition to clean energy by reusing valuable assets and reducing the need for new construction.

Quaise has been making significant progress in demonstrating the viability of its technology. In 2025, the company announced that it had successfully drilled to a depth of 100 meters using its proprietary millimeter-wave technology at a field site in Texas. While this is just a fraction of the target depth, it represents a major milestone, proving the technology's ability to operate in real-world conditions and at a speed ten times faster than previous tests. The company has plans for a full-scale drilling rig and aims to have its first superhot enhanced geothermal system, rated to 100 MW of thermal energy, operational by 2026, with the first repowered fossil fuel plant coming online by 2028.

Challenges and the Path Forward

Despite the immense promise of millimeter-wave drilling and deep geothermal energy, there are still challenges to overcome.

Technological Hurdles: While Quaise's recent success is promising, scaling the technology to drill to depths of 20 kilometers is a significant engineering challenge. This includes ensuring the efficient transmission of high-power millimeter waves over long distances through the waveguide and managing the complex physics of plasma generation at the drilling front.
High Upfront Costs: Geothermal projects, particularly those involving new technologies, have high upfront capital costs for exploration, drilling, and power plant construction. Securing financing for these projects can be challenging due to the perceived risks.
Induced Seismicity: A concern with some forms of enhanced geothermal systems that rely on hydraulic fracturing to create underground reservoirs is the potential for induced seismicity, or minor earthquakes. However, Quaise's approach, which aims to tap into naturally permeable rock formations or create a closed-loop system, may mitigate this risk.
Public Perception and Regulatory Frameworks: As with any new energy technology, gaining public acceptance and establishing clear regulatory frameworks will be crucial for the widespread deployment of deep geothermal energy.

To address these challenges, continued investment in research, development, and demonstration projects is essential. Government support, in the form of incentives and streamlined permitting processes, can also play a vital role in accelerating the commercialization of these technologies.

The Future is Bright and Hot

Millimeter-wave drilling represents a paradigm shift in our ability to access the Earth's internal heat. By overcoming the physical barriers that have long hindered deep drilling, this technology has the potential to unlock a clean, reliable, and universally accessible energy source. Deep geothermal energy, made possible by MMW drilling, could provide the baseload power needed to complement intermittent renewables like solar and wind, creating a truly stable and resilient clean energy grid.

The implications of this technological leap are profound. It could lead to a future where every nation has the potential to achieve energy independence, powered by the heat beneath their feet. It could dramatically accelerate the transition away from fossil fuels, helping to mitigate the impacts of climate change. With companies like Quaise Energy pushing the boundaries of what is possible, the prospect of a world powered by the clean, abundant energy from the Earth's core is no longer a distant dream, but an increasingly tangible reality. The journey to unlock this "El Dorado of clean energy" is well underway, and it promises to reshape our energy landscape for generations to come.