US-based start-up Quaise Energy was founded in 2018 to develop a millimetre-wave drilling system for converting existing thermal power stations to use superdeep geothermal energy. The system repurposes existing gyrotron technology – vacuum electronic devices typically used in nuclear fusion research to heat plasmas – to drill 12 miles beneath the surface, where temperatures exceed 400°C (752°F). No fracking is required, avoiding the potential for earthquakes that have occurred in other geothermal systems. It is also hoped that drilling using the technique will be fast, with the aim to complete boreholes in 100 days using existing 1MW gyrotrons. Energy Monitor sat down with Quaise Energy co-founder and CEO Carlos Araque to discuss the technology’s development and the potential deep geothermal holds for the world’s energy transition.

Geothermal energy start-up Quaise Energy co-founder and CEO Carlos Araque headshot
Quaise Energy co-founder and CEO Carlos Araque. Credit: Quaise Energy.

Quaise Energy is developing technology that would smash the world record for the deepest-ever borehole, which currently stands at 7.6 miles, to tap geothermal power. How is the technology coming along?

We’re demonstrating a fundamentally new way to drill much deeper and much hotter. As we progress with that, we’ll eventually enter a project and develop a field, but that’s not until the latter part of this decade.

The technology was born at the MIT Plasma Science and Fusion Center under the scope of fusion research. I worked on it for about ten years before the company was born. In the four years since we started the company, we’ve now taken the technology out of the university into our own lab in Houston, and we’ve scaled what the technology can do by 100 times. It’s impressive, but we still need to scale it another 100 times. And to do that, we need to get into the field; we need to build field-deployable versions of the technology so that we can do it on a drilling rig or truck. If everything goes well, we should be talking about the first-ever field trials within a year from now.

What goals have you set for the technology’s development, and how much geothermal power – and at what levelised cost of electricity (LCOE) – will it be able to supply once operational?

We tell the forward story with three key years in mind: 2024, 2026 and 2028. 2024 is when we first demonstrate this in the field, 2026 is when we first extract steam from the ground (geothermal energy usually takes the form of hot water steam), and 2028 is when we want to do that next to somebody willing to buy that steam – it could be a power plant, for example, so they don’t have to burn the fossil fuel to make the steam. So the first real projects start in the second half of this decade – 2025 onwards – and culminate with the first end-to-end demonstration by 2028.

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That’ll be the first of thousands that need to be done to decarbonise industry. So, having proven the point a few times, you start having access to mainstream capital and getting into project development as a commercial entity. That will happen in the 2030s, but 2028 is the date where we want to say to the world “look, we powered a fossil-fired power plant without the fossil fuel!”

We’ve looked at potential LCOE extensively ourselves and we’ve used energy consultancies to validate our work. Subject to the technology working the way we intend it to work – meaning how fast and cheaply we can drill – we start talking about LCOE between $20 and $40 per megawatt-hour. The difference between the $20 and the $40 has to do with how deep we need to drill in different places and whether we need to build a power plant. If we need to build a power plant, then it's on the high side of that; if we don't need to, because there's an existing one that we're powering, it'll be on the lower side of the range. So we're trying to get very close to wind and solar prices.

The LCOE of wind and solar is typically between $20 and $100. We want to park ourselves on the lower end of that range to be competitive with the most competitive wind and solar, wherever they are – but to be able to do it in every location and 24/7. It's possible because we drill at a cost that doesn't increase exponentially with depth. It's also possible because we’ll start extracting a lot of energy from each well. When you go very hot [in other words, deep], that radically changes the power produced by factors of 10–20.

If successful, the technology could make geothermal power relevant to all countries rather than just those with high tectonic activity, correct?

Drilling for oil and gas hardly ever happens below three miles, but oil is relatively shallow compared to geothermal. The technology has been perfected for three miles, but for geothermal it only starts there. Countries like Iceland and Kenya are blessed with high geothermal gradients (geothermal at shallow depths), so they can simply borrow technology from the oil and gas industry and it’s good enough to do the job. Three to 12 miles is really the sweet spot for geothermal. That's a little bit too difficult for oil and gas technology. It can be done, but it's very, very expensive.

The difference between a place like Iceland and a place like New York is how deep you need to go to reach the temperatures that you want. We want to get to 300–500°C. In Iceland, you can get there in three miles; if you're in New York, you probably have to go eight miles. It doesn't sound like much, but it makes all the difference in the amount of heat we can extract and the amount of energy we can provide to that city. When you look at the entire world, the maximum depth you would need to drill to tap geothermal would be 12 miles. So, we really want to be able to go to 12 so the whole world will have access to geothermal power.

What are the challenges of drilling and extracting geothermal power from those depths, and what makes Quaise’s technology distinct?

A lot of the challenges are the same as for oil and gas. The subsurface is an uncertain environment. The deeper you go, the more extremes you have, but we've come a long way with the oil and gas industry to develop a whole suite of technologies, techniques and measurement systems to minimise that risk. The main challenge is maintaining wellbores from closing in on themselves as you go deeper. There's a lot of pressure in the rock and these holes eventually will collapse. The way we answer that is by creating a glass wall in the rock as we burn it. When our technology vaporises the rock, it creates a glass wall and that remains on the walls and prevents the hole from collapsing.

The next challenge is simply the engineering effort behind using technologies that are meant for the fusion laboratory, like gyrotrons and waveguides, in a drilling rig in the middle of nowhere. There is a lot of engineering behind that to make things reliable.

We’ve seen a lot of activity in geothermal recently. Everybody's talking about shallow geothermal and low-temperature geothermal, and there's a lot of innovation in trying to do a little bit better without having to invent new technology. That certainly will have a good outcome and many companies will succeed, but in respect to the scale of energy transition, it will make very little difference. We’re working on something very different. We're working on truly deep, hot, industrial-grade geothermal. When we look at that space, we can only find one other company in the world, out of hundreds, that does this. It's a company in Slovakia called GA Drilling, and they really are talking about drilling deeper and hotter to get a better geothermal grade. They're further along than us and will get into the field before we do. Their technology will be relatively useful in the 5–10km range, or 3–7 miles, but the technology won't be able to go beyond seven miles simply because of the way the technology is designed. However, going seven miles is pretty good. It actually does open geothermal quite a bit in many places.

Geothermal has been around for a long time but has yet to really catch on as a clean energy technology. Why is that, and what are its pros and cons in comparison with other technologies?

There are two big aspects to that. If you look at places like Iceland, Kenya or Indonesia, where you have the heat close to the surface, they do already have geothermal as a very significant part of their primary energy supply. In Iceland, for example, 30% of its electric energy comes from geothermal and about 70–80% of the energy for heating. Kenya gets about half of its electricity from geothermal. So, for those places where the heat is closer, geothermal is a no-brainer, and it's allowing these countries to gain tremendous advantage with respect to their energy transition and energy security.

The reason it hasn't scaled beyond that is because there hasn't been the need. Oil and gas is the industry that's best positioned to scale geothermal, and deep geothermal requires a significant investment from the industry. As long as they don't have to make that investment, because they're happily operating oil and gas fields, it won’t happen. What I'm trying to do with Quaise is to dramatically change the economics of developing geothermal so that oil and gas has a very strong reason to take it on and do it at scale. I come from oil and gas myself, so I know very well how they think and what they're looking for in a project.

Can you explain the rapidly growing interest in the technology?

The amount of investment going into geothermal in the past two years is far greater than the last 30. So yes, there's been a massive increase and it's because the world is trying to transition out of fossil fuels and geothermal is a resource that can clearly help achieve that. However, a lot of the investment is going into relatively shallow geothermal – people are not willing to take big risks – and while there is a lot of investment going into geothermal, it's still tiny compared with wind and solar.

Geothermal still produces some greenhouse gas emissions, releasing gases trapped underground. In countries like Italy and Turkey, the CO₂ emissions of geothermal power plants can reach 1,300g per kilowatt-hour, surpassing even the emissions of coal-powered stations. How do you ensure the technology is as green as possible and not adding to the problem via certain low-quality projects?

Geothermal today is 100% hydrothermal, which means you drill a hole, there's a water aquifer that's hot down there and you extract that water. The geothermal we're developing has very little to do with that because those aquifers don't exist widely in the world. If we were trying to tap into hydrothermal, we wouldn't be able to scale in the way we intend to scale. Instead, what we're doing is going into hot rock that doesn't have water and putting in the water ourselves: water goes in, heats up and comes back out. All of that happens within an hour. So the amount of solid and gas that water will carry is drastically different. We're really talking about two very, very different things.

It has been projected that geothermal energy will provide around 800–1,300 terawatt-hours per year by 2050, contributing 2–3% to global electricity generation. Do you agree with that estimate? What role do you believe geothermal energy will play in the energy mix by then?

When you look at the different pathways that different organisations have proposed, you will see that the geothermal content is relatively small. It's usually in the range of 1–5% of total primary supply. It's small, but it's significant compared with what it is today. Today, it's 0.5%. So that would be a 10x scale-up.

However, that assumes no radical new technological innovation. I don't believe in that; I'm not doing the company I'm doing and spending my life force doing it for a 1–5% piece of the pie. I think if we succeed with breaking down the technological barriers, geothermal can be upwards of 50% of total primary energy supply.

I'm confident because the externalities that come with wind, solar and batteries, which are the other top candidates, are too large to bear at multi-terawatt scale: too much land, too many minerals, too much labour per unit of energy. Geothermal is very different: it is more like fossil fuels without the carbon. It's more like nuclear – except fusion doesn't work yet and fission is controversial.