Make Geothermal Great Again

19. ...With Nuclear Fusion Tech? Time to get technical. (8 min read)

Photo by Mark Kuiper on Unsplash

I am sure by now, that most of you have heard of the recently publicized progress on nuclear fusion power from the US Dept. of Energy. For the first time, scientists managed to get more power from the fusion experiment than what they put in, therefore theoretically showing signs of promise for unlimited clean energy from nuclear fusion.

There is a lot of detail and nuance in that experiment which makes the reality of nuclear fusion power a long way off, but there is something else in that experiment that might actually deliver on this promise sooner. Much sooner. Within this decade.

But not with nuclear energy - instead, we may have a real shot at an unlimited, yet untapped, source of energy available worldwide: Geothermal Energy. Now you’re thinking - wait, geothermal is nothing new. Its been around for ages in volcanic regions like Iceland. Why the hype now?

I believe there is good reason to hype this up, and I will attempt to explain why. Welcome to this week’s Climatonomics!

Classical Geothermal Power Plants 101

In my view, geothermal energy has been the unloved stepchild of the renewable energy family in the recent decades (Ok, I think hydro power gets even worse treatment, but that is a topic for another post). There is a good reason for it, because of how geothermal energy works:

First, you identify regions of the land where there has been a lot of volcanic activity, because the rocks underground are hot (The natural geysers are a consequence of this), and you drill a hole to reach them. Next, down this hole, you pump water, or any other fluid with attractive thermal properties, to reach these rocks. The water contacts the hot rocks and is vaporized into steam. The steam comes up through another hole, and is piped to a power plant where the it powers a turbine to generate electricity.

This plant is quite similar to a thermal power plant, where the steam is generated by burning fossil fuels. The key difference in geothermal is that the steam is generated by a renewable source.

The key parameter here is the depth of the holes: Most holes are less than 7 kilometers, because places with natural volcanic activity have hot rocks closer to the ground, and its therefore economical to drill these holes. The oil and gas industry has been drilling for a long time, and the technology is mature, which is readily extended here. This expertise is particularly abundant in the US, with the fracking revolution that made it abundant in cheap natural gas. Much like EGS, fracking needs drilling deep wells and injecting water into it.

But there’s a catch: This “traditional” technology for geothermal energy is only feasible where the hot rocks are closer to the surface. The list of places where this occurs is quite short: Iceland, the Pacific ring of fire and other regions where tectonic activity and faults allow magma to escape upwards. While this creates opportunities, it also has some serious issues preventing exploitation, as we will see soon. So adoption of geothermal remains geographically limited, much like oil and gas. Either you have it, or you don’t. Atleast that used to be the story for a long time.

… And Energy for All: Enhanced Geothermal Energy

In the past few decades, scientists have realized that nearly every place on earth can be suitable for geothermal wells, even if you don’t see obvious volcanic activity close to the surface. And whats more, the energy can be of much higher quality, and we can produce geothermal energy 10 times more than what we have now. And did I mention it can work anywhere? These are Enhanced Geothermal Systems (EGS).

Sounds too good to be true? It is true, but there is a catch: You have to drill deep. Like, really deep. While geothermal wells today are around 6-7 kilometers deep, we need to drill 15-20 kilometers to get access to Super Hot Rocks (SHR) - yes, that is the actual technical term - which are way hotter than anything you get close to the surface, and hence can provide an unlimited thermal energy source no matter where you live. SHR is often over 300 degree Celsius, while water becomes steam at 100 degree C. At 300 C, we instead get supercritical steam, which can carry 5-10 times more heat than just hot water. This makes the geothermal well extremely productive.

Unlike wind and solar, geothermal energy supply is always ON and does not need fossil fuels as base loads. A 2006 report from MIT and the US Government mentioned that the total energy capacity of EGS is enough to power the world for several millennia. Sure, the actual, economically exploitable power is lower than that… but it is still extremely high compared to our current capacity.

So why is this not mainstream yet? The biggest reason: Drilling deeper is more difficult and expensive, and often unreliable. The deeper you get, the harder the rock, which needs even harder drilling tools that can withstand extreme temperature, pressure and prolonged operating conditions. Wear and tear is extremely high, so drilling these wells is almost always uneconomical.

In the few places that it has been tried, it has been successful generating power consistently regardless of weather or season. Geothermal is an extremely reliable power source … if we can get to it.

And I am writing this post, because that may be about happen. Because some smart folks realized that you don’t always need to drill to make holes through rocks, if we can just, well…. zap them with lasers?

In the last few years, engineers realized it might just work, if you replace lasers with microwaves (Lasers were unsuccessfully tried in the 1990s). Yes, the same thing you used to heat that pizza leftovers from last night.

Melting Rocks with Millimeter-Wave Magic

Lets go back to the nuclear fusion experiment. One of the key aspects of the experiment is to quickly heat plasmas to millions of degrees, to kickstart the fusion process. Back in the 1960s at the height of the cold war scientific competition between the Soviets and Americans, the Russian scientists invented a device to do just that: The Gyrotron.

A Gyrotron at EPFL, Switzerland for Fusion Research

A gyrotron is effectively an electron gun that zaps high energy microwaves at a targeted location. These frequencies are extremely high, and therefore wavelengths are really small, usually in millimeters. This is also why any device emitting these frequencies are called “millimeter-wave” or mmWave. They can concentrate a large amount of energy very close to it. In contrast, lower frequencies (and higher wavelengths) are used in long distance radio communications.

We use mmWave everyday: The microwave oven, 5G devices, the body-scanner in the airport.. the list goes on. The US military even has a non-lethal mmWave weapon that heats up the skin within seconds, so that the person is forced to move away (And it is apparently harmless when the exposure stops). Here’s an interesting video showing soldiers, media and even generals trying it out on themselves. Its fascinating how much heat a targeted “mmWave canon” can generate in 2 seconds:

Long story short, mmWaves are directed energy canons. Can be used to quickly heat metals in fusion experiments, annoy people and in general, can be used anywhere you need a LOT of energy delivered quickly.

A few years ago, MIT researcher Dr. Paul Woskov, decided to try it to drill rocks. He reasoned that if Gyrotrons can indeed be so powerful, they should be able to vaporize and melt rocks without ever having to touch it. And just like that, the problem of wear and tear - the single biggest impediment in mechanical drilling is eliminated, and EGS can become reality. He brought commercially available gyrotrons and started zapping rocks in his laboratory, with interest from the US Dept. of Energy, which wanted to break into the SHR one way or the other. The entire scientific report is available here (and I enjoyed reading it way more than I expected!) I have selected some images of various types of rock that have been "drilled" through and obliterated without any contact, using high energy mmWave pulses:

Limestone Rock after exposure.

And here is my favorite. Complete disintegration of an entire slab of basalt

After these landmark experiments in 2014, there has been renewed interest in the industry to commercialize this technology.

There are now two startups: Altarock Energy which aims to build modern EGS systems and convert existing coal plants into EGS plants. The actual mmWave technology comes from the startup Quaise Energy, which has partnered with Altarock to build pilot projects in many locations in the USA, with a lot of financial and technological support from the US Dept. of Energy and its national labs.

Challenges… And Promise

Like any new tech, its not without challenges: controlling mmWaves in a precise path is difficult, and zapping rocks takes 4 times as much energy as drilling them, which raises economic feasibility concerns. But the tests so far have shown that, unlike nuclear fusion, this is a problem of engineering, and not battling fundamental physics. And thus, there is research at these startups to make the technology cheaper and reliable, since the proof of concept is functional.

And remember a lot of geothermal sites are close to the Pacific ring of fire? High volcanic activity often co-exists with seismic risk. Drilling for fracking has already led to mico-earthquakes in many parts of the US, though not significant enough to damage property. The same risk exists for drilling in EGS too.

Basel in Switzerland is a classic example, where an EGS project in 2007 caused several earthquakes, causing panic among the people and led to the much publicized cancellation of the project. Ironically, Basel already sits on a seismic fault and an earthquake destroyed the city in 1356 A.D. Unfortunately, the 2007 project did not sufficiently conduct a seismic risk study, and the expensive project was shelved in a hurry, with considerable scientific attention.

So… EGS is not really for everyone. If you are in an earthquake prone area, wind and solar are safer bets. Thankfully large parts of the world are not in this category.

The best part of mmWave EGS is that the rest of the infrastructure is exactly what coal and thermal plants already have. Unlike wind or solar, which need entirely new tech ecosystems to support their adoption, oil and gas industry already knows how to use geothermal. A lot of the talent and facilities can already be used, meaning lower costs. And speed. AltaRock plans to have converted the first coal plant to EGS in just 5 years from now, with projects that are already underway.

This makes the high cost of mmWave much more tolerable as an investor. And the US government is bullish and willing to throw money. The fracking industry already knows how to drill and build power plants. Now we may just get a way to quickly retrofit it into a renewable plant. I can’t imagine a faster, more effective method to decarbonization.

So… while we are gaping at solar, wind, batteries and the problem of baseload … geothermal might just quietly save us all. Who says nuclear fusion research has not paid off? ;-)

Until next week!