Geothermal energy has the potential to be an always-on power source for countries around the world. However, it hasn’t been the hottest renewable energy option because drilling deep enough into the earth to reach sufficiently high temperatures is difficult and costly. Yet, a startup has recently unearthed a solution that might solve this problem: A heat ray to melt rocks (sort of). I know it sounds like a Star Wars remake, but we’re not talking about the Death Star here. This is actually a well-established technology from nuclear fusion research that is being reapplied to geothermal energy. Could it unlock the true potential of geothermal energy and make it better than solar and wind? Let’s see if we can come to a decision on this. Spoiler: it’s pretty cool … or should I say hot?

I’m currently in the process of building a new net zero home and am scoping installing a geothermal heating and cooling system. The idea of tapping into the earth as a stable heat source for a heat pump system is really enticing for our homes, but we can also tap deeper into the earth for a consistent super hot heat source to power turbines to generate electricity for our cities and towns.

Unlike solar and wind, geothermal energy could provide a more stable supply of clean power while taking up barely any land. On the other hand, current drilling techniques can’t affordably reach the hottest spots of the Earth to unlock that potential. In fact, penetrating deep into hard rock is a tricky and expensive process. Along with exploration, digging wells accounts for 40% of the total upfront cost of a geothermal plant.1 That’s why scientists are turning to a death ray … again, not really … I’ll get to this killer technology in a minute, but first let’s have a brief recap on geothermal energy.

This source of power has been on our planet for ever. Well, actually inside it. The Earth’s inner core is about as hot as the sun, which is why it’s often nicknamed, “the sun beneath our feet”.2 Good news is that it will take billions of years for the Earth to cool down.3 Fueled by residual heat from our planet’s creation and the decay of radioactive elements, this underground sun gave rise to natural hydrothermal reservoirs.4 Basically, the Earth’s nucleus heat pushes water up through permeable rocks until it hits a wall, a.k.a. impermeable caprock. Trapped, the water pressure rises and can sometimes break through. Think of Roman baths relying on hot springs.5 Or perhaps Icelanders toasting bread over geysers.6 Aside from enabling carbon-free hot baths and outdoor barbecues we can use subsurface hot steam to drive a turbine and produce electricity.

There are several plant configurations that may be able to convert this thermal energy into electrical energy.7 Out of all options, binary cycle power plants are the newest and most sustainable ones, and offer the most promise for geothermal power. Unlike other designs, binary plants don’t use the underground hot water to generate steam. To be more specific, after extracting it and further heating it up to max 400°F (ca. 204 C)8, they run it through a heat exchanger. Here, the geothermal water transfers its heat to a secondary liquid with a much lower boiling point. This then generates the steam that will spin the turbine. The plant includes a condenser to convert steam back into a liquid and reuse it. Leveraging this closed-loop binary system, you won’t boil off the geothermal fluids which, other than water vapor, contain carbon dioxide, hydrogen sulfide and other toxic compounds.9 You can probably see why this is a greener and preferred alternative to dry and flash steam plants.

The overall geothermal potential is huge. According to AltaRock Energy, harvesting only 0.1% of the planet’s heat could satisfy the world’s energy hunger for 2 million years.10 Given how cool that is (or hot), why did geothermal energy account for only 0.55% of our global electricity generation as of 2018?11 Mainly because the accessible part of that heat is scattered across the Earth’s crust. In fact, most hydrothermal reservoirs such as volcano fumaroles, springs and geysers are only found along tectonic plates.12 In addition, the water filling shallow geothermal pockets isn’t hot enough to make energy harvesting cost-effective. Not to mention the technical and economic hurdles of reaching hotter spots using current drilling technologies. Yet, thanks to new drilling technology, the true potential of geothermal power could be closer than ever. This innovation could get us below 10 km (ca. 6 miles) in a more cost-effective fashion. Down there, geothermal sources have much higher temperatures and are more widespread.

A ground-breaking tech

While being cost-effective, the potential of solar and wind farms is undermined by their intermittency. Instead, a 24/7 green energy source like geothermal could give us an extra powerful weapon against global warming. Speaking of weapons, let’s dig deeper into how death rays (again, not a real death ray) could push geothermal energy to a new level.

It all began with the work of Paul Woskov, a senior research engineer at MIT’s Plasma Science and Fusion Center (PSFC). In 2012, he demonstrated the use of a gyrotron to vaporize rock instead of grinding it.13 This high-powered vacuum tube generates a beam of millimeter-long radio-frequency (RF) waves14, directed through a waveguide, to heat up a plasma and control its temperature in fusion reactors for the last 50 years.15 Hijacking this fusion tech, Woskov envisioned drilling ultra-deep geothermal boreholes. So, how does that work? You would have a metallic tube embedding the gyrotron blasting high-frequency electromagnetic waves to fuse the underground rock. The system injects a gas for cleaning up the post-vaporization mess. To be more specific, the gas cools down the hot vapors, which condense into nanoparticles. These are then flushed out of the well by the high-pressure stream. This process might help drill deep holes, but you wouldn’t use this sophisticated drilling for the entire process. I reached out to Quaise’s CEO, Carlos Araque, the on-the-ground…or perhaps underground…arm of this geothermal revolution, who filled me in on that.

“So in geology you have the sedimentary rock and then below it, you have the basement. Sedimentary rock it’s unconsolidated, it’s easy to drill through. And it’s what mechanical drilling systems are very good at doing, so you drill that first portion conventionally, no difference there. But the second portion is very hard to do. So, in that second portion we use a millimeter wave drill.” -Carlos Araque

Based on his experimental results, Woskov figured out that millimetric waves would make the drilling process more cost-efficient. First, you wouldn’t be limited by temperature and rock hardness.16 On top of that, there’s no need to have downhole mechanical equipment that could get damaged. Thanks to a wavelength about 1,000x longer than that of a typical infrared laser17, the millimetric waves can travel through the incoming rock nanoparticles without being scattered significantly. Which means the beam doesn’t lose much energy before reaching the target surface. Also, the hot molten rock absorbs more energy when irradiated by a gyrotron compared to when hit by a standard laser. Overall gyrotrons are up to 5x more energy efficient than the best lower-wavelength laser you can get.18 But what about costs? Paul Woskov had some thoughts on that.

“I did look at the cost of electricity to vaporize a volume of rock. That’s the main consumable in direct energy drilling. I made estimates that for an eight inch diameter hole and about 10 kilometers deep, it would cost something like a half a million dollars of electricity to vaporize an equivalent volume of granite of that size and depth. When you look at those depths, the total cost of a mechanical drill well is somewhere in the order of $30 million.” -Paul Woskov

That’s crazy, right? If that verifies, we’re talking about saving tens of millions of dollars. But there’s another key economic benefit of using heat rays. When relying on mechanical processes such as rotary technology, you need a high-density fluid, a.k.a. drilling mud, to counter the surrounding pressure on the well and prevent it from collapsing. In contrast, millimetric waves don’t require drilling mud, but how would a gyrotron-drilled hole bear thousands of atmospheres worth of pressure without failing? As part of the process, some of the waves will strike the bore walls, causing it to vitrify, meaning the surface will transform into a glassy coating. . Apart from sealing any wall cracks, the heating process will increase the internal pressure, which balances the outer force. As a result, it will be possible to burrow deeper yet more stable boreholes without adding any drilling mud, which is another aspect that could make the whole process more profitable.

“You’re making a glass lined hole and that glass is very strong. And so in effect, we are casing at the same time that we’re drilling the hole, which is another big expense savings for making a hole.” -Paul Woskov

When factoring in all these extra costs, Woskow’s brainchild turns out to be way more cost-effective.

“I estimate that it could be maybe 10 times cheaper than a really deep mechanical drill wall.” -Paul Woskov

Aside from being costly, drilling mud doesn’t work at temperatures like 500°C (932 °F), which is where geothermal energy production is most efficient. Paul had some really nice insights on that.

“Drilling muds don’t function at those temperatures very well. The weight of the column begins to run out the deeper you go because the density of the mud is never close enough to the rock density. So eventually you can’t have enough drilling mud columns balancing the outward pressure. However, with direct energy drilling in high temperatures, we are always over pressured, no matter what depth.” -Paul Woskov

To be more specific, this mud-free drilling system could profitably withstand pressure-related stresses below 10 km, which is where geothermal access becomes universal. According to the US Department of Energy (DOE)’s GeoVision report19, leveraging these untapped subterranean heat sources could increase geothermal-based electricity 26-fold by 2050. In addition to a wider availability, when you go below 10 km (ca. 6 miles), you’ll find the so-called Super Hot Rock (SHR) geothermal resources20, with temperatures above 375°C (707 °F). Under these conditions a geothermal plant can tap into supercritical water, which is more energy dense than its non-supercritical counterpart. A well plunging into SHR would yield up to 10x more energy than a conventional enhanced geothermal system (EGS). Based on the technical and economic feasibility study conducted by AltaRock Energy on the Newberry Volcano site, SHR would reduce geothermal’s Levelized Cost of Electricity (LCOE) by 50%.21 On top of that, the company estimated that SHR-based geothermal could have a lower LCOE than onshore wind or even solar.22

Bringing geothermal energy to the lower level

Clearly, Woskov’s design holds promise for bringing our geothermal power supply to a higher level (or lower depth I guess), which means our energy grid would become much less reliant on fossil fuels. His fusion-inspired drilling tech is not just confined to the lab space. Last February, an MIT spin-off, Quaise, raised $40M23 to develop this ground-breaking tech. They graduated from using a 10-kilowatt gyrotron to drill a 10-centimeter-deep hole in palm-sized stone to using Oak Ridge lab’s megawatt-sized gyrotron. The company bore 3-foot-deep holes into much larger rocks. Quaise is partnering with AltaRock to create their first pilot project where they’re aiming to drill a 3,300-foot-deep hole near the Newberry Volcano, which was chosen as an ideal testing site. In fact, AltaRock believes this crater could be one of the largest unused geothermal resources in North America. The presence of a shallow magma body makes the rock down there much hotter than other places, which is why AltaRock could reach super hot temperatures (above 400°C or 752 F) at a quarter the depth you would need to dig down to in other places.24 It’s a good testing ground.

Looking ahead, Quaise is planning to build its first full-scale hybrid drilling rig in 2024.25 Based on this setup, Quaise would first use conventional rotary drilling to go down to the basement rock, which is where they would activate their gyrotron-powered rock-vaporizing system to reach 20 km (ca. 12 miles) to reach temperatures as high as 500°C (932 °F). The company touts that they could get down to that depth in 100 days using a 1-MW gyrotron.26 Just to give you a sense of scale, the Kola Superdeep Borehole, the deepest hole ever dug on Earth27, went down to 40,230 foot-deep (12.2 km) and took 20 years to complete. I can hear you already. Is 100 days even possible? Carlos shed some light on this.

“When you’re five kilometers down in a 10 day window, you may spend 30 hours drilling, that’s the life of the drill bit before it needs replacement.” -Carlos Araque

“10 days is 240 hours, so you spend seven eighths of the time running the pipe in and out of the hole to replace that drill bit. 10 days is a million dollars of break time. We don’t talk about drilling a hundred meters per hour, we talk about drilling a very consistent five meters per hour. It just goes because there’s nothing to replace.” -Carlos Araque

“Now, if we can hit a drilling cost of a thousand dollars per meter regardless of depth, your LCOs are in the 1 to 3 cents per kilowatt hour, so cost parity with wind and solar, but firm, and always on.” -Carlos Araque

So, in theory, it sounds like Quaise has got some chances to achieve their goal. In practice, we should wait for real-world tests in the field. Nevertheless, the company has a clear and clever long-term vision. They aim to retrofit existing fossil fuel plants which will eventually be decommissioned during the low-carbon transition. Making the most out of this ready-to-use infrastructure, they could simply swap coal or natural gas generated steam with round-the-clock underground hot vapor to spin the turbines.

“Steam can come from the ground, so that idea gets a lot of traction with power project developers, because they have these power plants that they’re losing their social license to operate and they’re increasingly less in the money, so there’s very few alternatives for these power plants to continue to operate. Those are the people that are most interested in what we’re trying to propose and trying a pilot with them.” -Carlos Araque

A pilot plant sounds exciting, but looks like it’ll still take some time for it to…pick up steam…

“We’re still more than three, four years away because we still need to do the technology demonstration before we even get to that.” -Carlos Araque

Along their geothermal drilling path Quaise may encounter some other issues. The deeper you drill, the more energy that is required during drilling and operations. As it stands, making up for this power loss means stealing electricity from the grid or running diesel generators. On the other hand, Quaise’s CEO claims that fossil fuels consumed by their drilling system would be less than 1% of the renewable energy generated by their well over its lifetime. But their system needs to account for gas pressure losses too. That’s because of the friction between the gas and the pipe walls. The further down the gas travels, the higher its pressure drop, the bigger the pump you need to circulate it in and out of the well. That’s one of the reasons why Quaise estimated that 20 km may be the lowest depth they could get to. Another drawback of ultra-deep digging might be earthquakes. Creating wells could destabilize geological layers, which can trigger seismic activity. This has cooled down some geothermal enthusiasts in different countries after power plants were forced to close.28 29 Carlos had a different take on this.

“When you drill for geothermal today, you’re mostly drilling near tectonic boundaries because that’s where the heat is closest to the surface, so you are very intentionally drilling near problematic zones with very young and unstable geology. When you have the luxury to go deeper without an exponential increasing cost, you move away from those instabilities. I would even argue that maybe 95% of the business case for our drilling is away from tectonic boundaries. We’re actually trying to make geothermal available no matter where you are. And most of the world is actually not on a tectonic boundary.” -Carlos Araque

Earthquakes aside, Quaise will need to keep an eye on budget. As reported by the International Renewable Energy Agency (IRENA) in 201930, setting up a geothermal plant would cost nearly $4,000/kW. This is roughly 4x more than what you need to spend for installing a solar farm. However, as mentioned by Carlos and Paul earlier, gyrotron-powered drilling could save money compared to a mechanical process.

I don’t know if Quaise’s geothermal approach is the panacea for our energy transition, but it should definitely be thrown into the mix. Relying on multiple clean electricity sources is the sustainable way forward. Carlos’ view seems to align with mine on this.

“When I think of renewables, they’re trying to do more with much, much more, so I don’t think that’s sustainable. And I think everybody forgets that, right? I’m not saying we shouldn’t do renewables, I think we should, but we should not forget that things like this and things like fusion, they need work because they are the ones that can actually get us to where we need to be as a species.” -Carlos Araque

I’m really excited by the potential of this. It’s also really cool to see a technology from fusion research getting reapplied in such a unique way. The development of fusion-inspired drilling would let us tap into plenty of super hot fluids by overcoming geographical and geological limitations. It could unleash a perpetual spring of geothermal power for a zero-carbon energy-independent world. However, although heat rays are based on solid tech, there are still economic barriers and testing to go through before reaching an industrial scale.

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  2. “Geothermal energy is poised for a big breakout – Vox.” 
  3. “How Much Longer Until the Core of the Earth Runs Out of Fuel?.” 
  4. “Where geothermal energy is found – EIA.” 
  5. “Geothermal hot springs used in Roman times could heat Bath Abbey ….” 
  6. “Why cook over an Icelandic geyser? Because you can – The ….” 
  7. “Geothermal Energy Explained – A Not So Hot Solution?.” 
  8. “Binary Cycle – an overview | ScienceDirect Topics.” 
  9. “Binary Power Plants – Stanford University.” 
  10. “AltaRock Energy – ARPA-E.” 
  11. “Renewable capacity highlights – IRENA.” 
  12. “Where geothermal energy is found – EIA.” 
  13. “Reaching underground resources | MIT Energy Initiative.” 
  14. “Rock, drill bit, microwave: Paul Woskov explores a new path through ….” 
  15. “Fusion tech is set to unlock near-limitless ultra-deep geothermal ….” 
  16. “Fusion tech is set to unlock near-limitless ultra-deep geothermal ….” 
  17. “Reaching underground resources | MIT Energy Initiative.” 
  18. “Reaching underground resources | MIT Energy Initiative.” 
  19. “GeoVision | Department of Energy.” 
  20. “Path to SuperHot Geothermal Energy Development.” 
  21. “AltaRock Energy Initiates Development of First SuperHot Rock ….” 
  22. “Super Hot EGS – ARPA-E.” 
  23. “Geothermal startup Quaise raises $40M for ultra-deep drilling.” 
  24. “How a breakthrough in geothermal could change our energy grid.” 
  25. “Quaise Energy.” 
  26. “Fusion tech is set to unlock near-limitless ultra-deep geothermal ….” 
  27. “The deepest hole we have ever dug – BBC Future.” 
  28. “Tremor around geothermal plant in France puts spotlight on safety.” 
  29. “Geothermal energy could save the planet. But watch for earthquakes.” 
  30. “Renewable power generation costs in 2019 – IRENA.” 

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