The Power of the Earth
On the future of geothermal energy
Tom Ough writes about next generation geothermal power for Issue 13. Read it online here.
The deepest hole humanity has ever dug is the Kola Superdeep Borehole. Soviet scientists, hoping to learn about the composition and geophysics of the Earth’s crust and upper mantle, began drilling on the Kola Peninsula, in the country’s extreme northwest, in 1970. After more than two decades, they reached a depth of 12 kilometers: a slender borehole three times the length of Central Park, and 113 times the depth of the world’s deepest metro station (Arsenalna in Kyiv).
The hole is less than 0.2 percent of the way to Earth’s core, whose center is thought to be 5,200 degrees Celsius. That temperature isn’t far off being twice as hot as the temperature necessary to vaporize iron. Knowing this, the scientists expected the bottom of their 12-kilometer hole to be 100 degrees Celsius, hot enough to boil water. Instead, it was 180 degrees Celsius, the heat of an oven.
At those depths, the drilling was pushing the limits of technological possibility. It’s difficult to get good performance out of a drill bit that far from the surface. It’s hard to dispose of ‘cuttings’ – the rock torn up by the drill – and harder still to keep replacing those drill bits, which quickly get gnarled up, without the swapping process leading to increasing inefficiency as the wellbore deepens. In these extreme conditions, granite behaves more like plastic than rock. It became more and more challenging to drill, and the project ran out of money. In 1995, the nine-inch borehole was welded shut.
The borehole remains stoppered. But the promise remains that by digging deep under the Earth, deeper than the Kola Superdeep Borehole, clean, reliable energy could be brought to the surface in vast quantities. Nuclear fission, so far, has been kneecapped by regulators; renewables have made great progress, but due to their intermittency they cannot currently solve our energy requirements; fusion continues to elude us. Energy is still hugely important for human advancement, and a lack of it may help explain our society’s post-1970s relative economic stagnation. How might we not only meet our current demands for energy but exceed them? The answer is under our noses.
Fossil fuels were formed hundreds of millions of years ago, but geothermal energy is billions of years in the making. Earth was formed 4.5 billion years ago from the collision, accretion, and compression of space rocks. The residual heat from this process, alongside the heat produced by the decay of radioactive elements such as thorium, uranium, and potassium, is the ultimate source of the furnace-like temperature of the planetary core, which accounts for 15 percent of Earth’s volume but – as a result of the hellish pressure of the weight of a planet – 30 percent of its mass.
It is an excellent source of free energy, and one that humans have always sought to take advantage of. Roman bathhouses made use of hot springs near volcanoes, where magma is close to the Earth’s surface. In drizzly southwest England, the hot springs in Bath, Somerset, atop which the Romans built a complex of temples, derive their heat from deep within the Earth’s crust. Rainwater percolates down through limestone aquifers to as deep as nine kilometers and is heated by the hot Earth. Pressurized, the water is forced back upward, picking up minerals from the limestone as it goes. And the Romans were late to this party. The archaeological record suggests that Native Americans were using hot springs more than 10,000 years ago.
It might have looked in the early twentieth century that geothermal power was on an exciting trajectory. In 1904, Piero Ginori Conti, a Tuscan who ran a boric acid extraction firm, used natural dry steam geysers to power a dynamo – an early generator – that lit five lightbulbs. (Dry steam, as opposed to wet steam, is so hot that it doesn’t carry any water droplets in it: it is 100 percent gas rather than partly liquid.)
Larderello, the Tuscan village where Conti lit those lightbulbs, still produces electrical power from geothermal energy. The dry steam geysers of California, which are similar to Larderello’s, have supported power plants since 1960. In 2022 they produced five percent of California’s in-state electricity generation, doing so by pumping water into the Earth and using the steam that subsequently arises to turn a turbine that drives a generator and, ultimately, creates electricity. After the US, the present day’s biggest producers of geothermal energy are Indonesia, the Philippines, Turkey, and New Zealand. Kenya and Iceland get most of their electricity from geothermal plants, though these are countries taking advantage of quirks of geology. They sit at the meeting points of tectonic plates, which allows them to access geothermal heat (and thus power) without massive drilling – and which also explains why each of these countries is speckled with volcanoes. Thanks to those countries, geothermal contributed 15.7 gigawatts of worldwide electrical power in 2020: enough to power 200 million lightbulbs. It is an amount that Conti, the Tuscan inventor, could hardly have dreamed of, yet it is a sliver of global energy production: an estimated 0.35 percent. The figure seems even more meager when one considers that an infinitesimal fraction of the Earth’s geothermal heat – a tenth of one percent of that heat, goes the calculation – would power humanity’s current outgoings for 20 million years.
The main reason geothermal does not account for more of the Earth’s energy production is that most countries lack ready access to subterranean high heat. With no recourse to volcanoes, hot springs, and fumaroles, developers are left with challenging options such as deep drilling. As scholars of the Kola Superdeep Borehole will know, deep drilling requires colossal up-front capital expenditure and is extremely technically challenging: not only in terms of the drilling itself, but also in terms of working out where to drill.
As well as that, geothermal projects have a record of causing tremors. These tremors are caused not by the drilling itself, but by the use of high-pressure fluids to force open underground pathways. (Most commonly used to extract shale gas, this is similar to the hydraulic fracturing used by the oil and gas industry and better known as ‘fracking’, but at lower pressure.) The pathways create a network through which water can pass, allowing engineers to pump it down though one well, then draw the same water, now heated, back up a neighboring well. This combination of hurdles – the cost, the uncertainty, the risks – have made geothermal projects much more difficult and expensive than drilling for gas. There was a crack of hope for geothermal in the 1970s, when the worldwide energy crisis compelled governments to look into alternative power sources, but fossil fuels retained their primacy. Even in the race to net zero, governments and environmentalists have preferred wind and solar energy, a preference so far requiring subsidies, massive investment, and a kind regulatory environment. The world’s production of geothermal power has been inching upward rather than rocketing.
This is a missed opportunity. The planet contains many orders of magnitude more energy than humanity currently requires – and more energy than we will require anytime soon. And where fossil fuels produce emissions, geothermal is clean. Where solar and wind are intermittent, and diffuse, needing many new transmission lines, battery storage parks, and long-term storage, geothermal power plants produce electricity 24/7 and can go almost anywhere. Nuclear reactors, like geothermal, produce clean energy on a continuous basis, but they carry unmerited stigma. Moreover, some reactors use highly enriched uranium, which fuels reasonable worries about proliferation of nuclear weapons.
In principle, then, geothermal offers superior energy security: it is an attractive enough proposition that the US Department of Energy announced an initiative to reduce the cost of enhanced geothermal systems, which use the fracking style outlined above, from $450 per megawatt-hour to $45 by 2035. (The median coal plant produces energy at $36 per megawatt-hour; solar energy has become similarly cheap when the sun is shining.) This could be achieved through incremental technological progress, but there are several ongoing attempts to create game-changing new geothermal technologies. If any one of those attempts succeeds, geothermal could become the biggest single power source in the world. Some policy thinkers are extremely excited: Alec Stapp, of the Institute for Progress, told me that things were coming together quickly enough for geothermal, relative to other existing and potential sources of energy, for him to predict that it could contribute anything from one third to two thirds of US baseload power in the coming decades.
Before we get to the technologies we might create in the future, let us first look at the current cutting edge. There is much excitement in the geothermal world around enhanced geothermal systems that use fracking-type methods. Think of it as geothermal that has been massively enhanced by expertise and technology derived from the hunt for shale gas. You can see this transmission of expertise in the career of Cindy Taff, formerly vice president of unconventional wells and logistics over Shell’s global operations and now the chief executive of Sage Geosystems, a Texan geothermal start-up that employs off-the-shelf oil and gas technology (as well as off-the-shelf oil and gas chief executives). On the day I spoke to Taff, her team had been running tests at an abandoned gas well. Taff said that the oil and gas sector, hitherto put off geothermal by the poor investment return relative to fossil fuels, was ‘watching and waiting for the industry to crack the nut on making geothermal more cost-effective’.
The signs are positive. The new generation of geothermal is making the Earth’s heat more accessible, even in countries where volcanoes were last active 50 million years ago. Take the UK, where those Roman baths remained, for 2,000 years, largely uncontested as the apex of national geothermal infrastructure. Cornwall, the county that forms the tip of Britain’s southwest peninsula, has, like the rest of the country, been untroubled by volcanoes since the Paleogene era: the interval between 66 million and 23 million years ago. To use the lingo, it has a relatively high geothermal gradient. This means that, as you go farther underground, it gets hotter faster than is typical. Drill a one-kilometer-deep borehole elsewhere in the UK, and the temperature at the bottom will be 20 degrees Celsius. Drill a hole of the same depth in Cornwall and the temperature will be close to 40 degrees Celsius. This is not because Cornwall has more exposure to the Earth’s core, but because the peninsula’s granite backbone contains radioactive potassium, thorium, and uranium. Over millions of years, these elements decay, and as they decay they produce heat. The bedrock acts something like a natural nuclear power plant. This makes Cornwall, a county of lush greenery and abandoned tin mines, one of the UK’s more promising venues for harvesting geothermal energy.
The Cornish greenery is its lushest at the Eden Project, where two sets of latticed, transparent domes play greenhouse to thousands of species of plant. One of the sets of domes houses the largest indoor rainforest in the world; the other houses a Mediterranean ecosystem. The project, built in a reclaimed china clay pit, was opened in 2001, a time when humanity was rather less concerned about climate change than it is today. Eden, as it’s known, needs around 3.5 gigawatt-hours of electrical power per year, and around five gigawatt-hours of heat. Powering it, Eden’s managers decided, should be a geothermal energy project. The project broke ground in May 2021 and was switched on in June 2023. Its 3.8-kilometer-deep heat main now delivers 85-degree-Celsius water to heat the greenhouses and offices of the Eden project. It would also be providing electricity, but it is expecting to wait 13 more years for a connection to the grid.
Gus Grand, who leads Eden’s geothermal project, showed me the site late in 2022. Visible through the fence’s lattice was a set of spent drill bits. Battered, rusty, and lined up in a row, they looked like they had been left there as an example to any drill bits considering stepping out of line. The bits were designed for the oil and gas industry: three fat, studded wheels in a housing of chunky steel. The steel was now orange-brown; the studs, which are the teeth via which the drillers slowly grind through the granite, were made of ultra-tough tungsten carbide, but had been thoroughly worn down. When in use, each bit hangs off the end of a drill string that, in this case, had to go five kilometers deep. It’s hot down there, it’s wet, and it’s kilometers away from the team on the surface. If you drop the drill bit down the hole, Grand told me, ‘you’re really stuffed’.
All this goes to illustrate the technical challenge of deep drilling. It is not easy; and we’re only just beginning to master it. Another challenge is the dearth of clarity over regulation from the Health and Safety Executive (HSE), which is the UK government agency that oversees occupational risk. Because the HSE does not have specific geothermal regulations, Eden had to default to full oil and gas regulation, whose lack of suitability cost the project money and time. (For example, Grand’s team had to hire, and regularly test, a ‘blowout preventer’: a piece of kit that prevents the uncontrolled release of natural gas, or crude oil, from within a well. The geothermal well contained neither natural gas nor crude oil, and the hiring of the blowout preventer and its operators cost the project, Grand says, tens of thousands of pounds per day.) A similar lack of regulatory clarity affects the geothermal industry in many other places. In America, for instance, many states have not yet clarified who owns the mineral rights to the heat accessed by deep drilling.
The challenge most immediately relevant to public opinion, however, is that of avoiding tremors. Grand’s project targets an existing fault, and is gentler than the fracking practiced by the oil and gas industry: it needs merely to pump water through existing fissures, rather than blast rocks open. But at 9.20pm on a still night in March 2022, people up to three miles away from the drill site felt their homes shake.
‘It was a real bugger’, Grand said frankly. A small, underground movement of water, during a pressure test, had triggered a 1.5-magnitude earthquake, which was not big enough to cause any damage, but which did not escape locals’ attention – though there are hundreds of similar sized or larger earthquakes across the UK each year.1 Work was paused, and Grand was hauled up to explain herself on BBC Cornwall. ‘Because [the project] is a sort of greater-good thing, it was okay’, she told me. ‘But I don’t want to be doing that again.’
There has been no repeat. The site, nestled in countryside, is quiet, compact, and unobtrusive, taking up little more space than a couple of tennis courts. Alongside it is a well-trodden bridle path. Before the work started, said Grand, ‘we had everyone going: “Oh my God, the horses will be terrified by the drilling rig.”’ But the subterranean drilling produces little external noise. Grand said the project’s loudest recorded sound is from the dawn chorus in the neighboring wood, which is composed of oaks and willow.
This is a miniature marvel of a power station. Its running will be cheap, but, at £24 million, its construction was expensive. The 11 gigawatt-hours of heat it can produce – the equivalent of heating about 900 homes – is therefore costly compared to conventional forms of power generation. Grand and the project’s various funders, however, see Eden Geothermal as a research endeavor: one that will help the cost of geothermal follow a similar (rapidly downward) curve to the cost of wind and solar, ultimately becoming competitive with other forms of energy.
Cornish geothermal offers a tantalizing glimpse into another potential upside of deep drilling. The water that emerges from geothermal systems is called brine, and Cornish brine is extremely high in lithium: 260-odd parts per million, reports United Downs, Cornwall’s other geothermal project. United Downs, a commercial plant whose parent company aims to generate electricity for £119 per megawatt-hour, finished its drilling in 2021 and is currently finalizing the design of its power station.2 The project’s leadership has not yet disclosed the potential value of the lithium it stands to harvest, but its hope is that the metal will further strengthen the economic case for deep geothermal heat and power. Lithium is essential for the lithium-ion batteries that power green technology such as electric cars. Although there have been several recent discoveries of significant deposits, it remains a metal in short global supply. But it is not the only metal that can be mined, as the terminology goes, from the brine.
Jonathan Blundy, a professor of earth sciences at the University of Oxford, would like to mine that brine from the flanks of dormant volcanoes. Lithium, gold, silver, and manganese are among a broad portfolio of metals that lurk in the fluid extracted by deep geothermal. Sitting at his desk, with rocks lining the bookshelves, Blundy explained to me that magma and volcanoes are ‘the main transport agent bringing these minerals from the Earth’s interior to the surface’.
This means that geothermal projects, if sited by those dormant volcanoes, could bring up extremely valuable metals. Sprinklings of Cornish lithium are one thing; the treasures of volcanoes are another. Through such projects, Blundy said, we could defray a huge fraction of the cost of geothermal power, reducing the net cost ‘by a factor of easily two, maybe ten’. This would not only offset the cost of drilling, but also reduce our dependence on the corrupt and illiberal governments that often control the supply of these valuable metals.
It is difficult to harvest these metals. Extracting them from the ‘unholy sludge’, as Blundy memorably put it, requires cutting-edge chemistry and a lot of trade secrets. Turning his monitor, he showed me a picture of a pipe so scaly that you’d think it came from Triton’s lavatory. The more mineral-rich geothermal fluids are highly corrosive, Blundy said, and liable to scale the wells’ interior. Understandably, geothermal engineers prefer having less salty fluid in their pipes, so Blundy is working on designing novel materials that prevent the formation of scale. He is also working on existing or prospective mine-the-brine projects in places such as Japan and Montserrat. Blundy explained why we get mineable clusters of individual ores, a story that starts with the elements’ creation in exploding stars and continues with the slow but ineluctable activity going on within the Earth even today. Different minerals respond differently to heat, pressure, and their chemical environment, melting or dissolving in some places and floating around, only to precipitate somewhere else. For 4.6 billion years, Blundy said, the Earth has been like ‘some crazy librarian, slowly but surely putting all the lithium here, and all the mercury there, and so on’. It is to this process that we owe everything we’ve ever mined.
The subterranean sorting process also explains why there is, according to Blundy’s estimate, enough valuable metal beneath every volcano to make these reserves comparable in value to major conventional mines. The idea wouldn’t apply to places like Cornwall, and it wouldn’t be financially viable on its own, but brine-mining is a plausible way of making conventional geothermal, which is expensive to get going, a little more financially attractive.
Left to its own devices, enhanced geothermal will make an increasingly large contribution toward baseload power. This is already happening in Continental Europe, where countries including France, Germany, and the Netherlands are quickly improving their capacity to harness geothermal power. Ten years ago, Germany’s geothermal sector had an installed capacity of 200 megawatts; ten years later that capacity is now 400 megawatts. It is projected to approach 850 megawatts by 2030 (albeit still significantly less than one percent of German energy consumption). Worldwide, further advances might come from closed-loop geothermal, in which sideways drilling – which is a technically difficult modern innovation – allows drillers to create a radiator-like network of subterranean pipes. When a geothermal project pumps water through a closed loop, it loses less heat than when it pumps water through the network of fractures created in enhanced geothermal. This method also makes tremors much less likely in the process of construction. Eavor, a start-up from the Canadian province of Alberta, is a pioneer of the closed-loop system, and has begun work on a power station in Germany.
An expansion of geothermal is underway, then, and it will continue even if governments continue to sit on their hands. But that expansion should be accelerated. First of all governments must ensure geothermal power plants can be swiftly connected to the grid, to avoid expensive drilling projects being unable to contribute their electricity. Governments that have not yet outlined health and safety regulations for geothermal drilling should do so. They ought to tailor those regulations to the geothermal industry rather than copying and pasting them from oil and gas. Governments must also clarify mineral rights, ensuring that drilling companies know where they stand and are incentivized to break ground. Finally, governments and industry would be serving their own interests by providing more research dollars – many more – toward the development of drilling methods that will help us get many kilometers deeper than is currently possible. These drilling methods are the difference between a global geothermal industry that improves incrementally and a global geothermal industry that revolutionizes the world’s energy supply.
At the same time as the Soviets were drilling the Kola Superdeep Borehole, Paul Woskov was trying to crack nuclear fusion. He’d been trying for some time. He was 20 years into his career as a senior research engineer at Massachusetts Institute of Technology, but the holy grail, endless clean energy, seemed little closer. The fusion reaction occurs within superheated plasma, and Woskov’s lab heated that plasma by firing millimeter waves at it. Within the electromagnetic spectrum, millimeter waves lie between the super high frequency band and the far infrared band. Classified as ‘extremely high frequency’, they have wavelengths from one to ten millimeters; hence the name. Millimeter waves, in other words, are high-powered beams of energy that are similar to the wavelengths commonly used in telecommunications, but of a higher intensity.
To produce these beams, Woskov’s lab used a gyrotron, a complex assembly of Soviet-invented machinery that uses a strong magnetic field to create highly concentrated millimeter waves. Gyrotrons are costly to build, costly to run, and difficult to maintain. But they are the best technology available for heating plasma to the 100 million degrees Celsius that is necessary for the fusion reaction to occur on Earth. (The Sun has the slightly unfair advantage of having a huge gravitational field that holds the ionized gas together, hence achieving fusion at a balmy 15 million degrees Celsius.)
In 2008, when an MIT energy initiative announced that it was looking for technology that would improve drilling, Woskov realized he might have an answer. The most common types of bedrock are basalt and granite, so Woskov brought a lump of each into the lab. As he heated a sample in the gyrotron’s test chamber, he heard the rock fracturing. Sometimes fragments of rock would rattle around the chamber, and the process often created the smell of hydrogen sulfide: quick-dissipating, but eggy.
This opened an intriguing possibility. It has been known since experiments with lasers in the 1990s that drilling with heat could be much faster than conventional drilling. But lasers quickly get neutered by the dust produced by the drilling process, which absorbs so much light that the lasers can’t get past it. The microwaves produced by a gyrotron, on the other hand, can be guided for kilometers and are unaffected by dust, making very deep wells possible.
Could geothermal in the future learn from fusion, just as geothermal today has learned from shale extraction?
This proof of concept would mean little if the process was ruinously expensive, but Woskov set about trying to prove mathematically that atomizing rocks with microwaves could be economically efficient. First he had to find how much heat was needed to reduce those rocks to fine dust: a difficult number to identify, because not many people had tried it before. But according to Woskov’s calculations, the process would be many times cheaper than the conventional method. Where a mechanically drilled eight-kilometer well typically costs about $50 million to drill, to create a similar well through the gyrotron method would be much cheaper. To do so using millimeter-wave-based technology, Woskov later told me, would use between 916 and 5,750 megawatt-hours of electricity, equivalent to 11,000-70,000 charges of a Tesla Model 3.3 At $120 per megawatt-hour (about how much electricity costs in Texas), this would only cost between $110,000 and $690,000, depending on whether the rock was melted, which would be cheaper, or vaporized – more convenient, but more energy-intensive. While this estimate excludes labor and capital costs, Woskov says these would be much lower than in conventional drilling, owing to the simplified process.
In that same year, 2008, Woskov and his MIT colleague Daniel Cohn filed a patent for what he called a millimeter-wave drilling system. There were many technical challenges to overcome, notably those concerning this novel use of gyrotrons. In principle, a powerful gyrotron should be able to fire continuously for 24 hours a day, seven days a week – rather than the current record of an hour at a time for an 800 kilowatt model, and eight continuous hours for a 200 kilowatt model – but to direct that power several kilometers into the Earth was an endeavor never before attempted, let alone successfully executed.
Woskov is now an advisor to a start-up, Quaise, that was spun out of MIT Plasma Science and Fusion Center in 2018. Quaise’s plan is to use millimeter waves to vaporize bedrock, which is the solid rock that lies beneath soil. This method, if feasible, would make it possible to create holes as deep as 20 kilometers. At those depths, rock is 500 degrees Celsius: superhot rock, as it’s called. Pumping water into superhot rock gives us supercritical water, water pressurized and heated beyond 373 degrees Celsius, at which point it has the low viscosity of a gas, the high density of a liquid, and an energy density not far off from that of fossil fuels. Supercritical water is so energy-dense that a successful attempt to commercially harness it would be, in the words of the volcanologist and petrologist Mike Cassidy, a ‘complete game changer’.
Quaise claims that by 2026 it will be able to produce 100 megawatts of thermal energy from ‘a handful of wells’. Perhaps half of those megawatts, depending on the efficiency the company can achieve, would become usable electrical power. A typical American nuclear plant, for context, produces one gigawatt of energy (1,000 megawatts). But in Quaise’s vision, new wells could be created far more easily than new nuclear power stations, and in much greater numbers, even replacing the gas- or coal-fired boilers of existing power plants to provide steam to their turbines.
Is Quaise’s plan feasible? Experts I spoke to explained that Quaise would need to overcome a succession of technical challenges. Millimeter waves require a high concentration of energy: how would that energy be transmitted several kilometers down the wellbore? And how well would the technique work in unfamiliar subterranean territory? High-temperature rock, a geologist told me, tends to perform in a ductile rather than a brittle fashion, meaning that it slowly shifts rather than staying rigid and snapping; would the wellbore close over time?
There are other questions, too. What happens when bedrock vaporizes? Does it condense back into ash, falling back down the wellbore? A literature review turned up nothing, Quaise’s CEO, Carlos Araque, told me. ‘Nobody has gone to vaporize rocks for a living.’ There are the logistical challenges of setting up the rig and obtaining the right gyrotron (this is Woskov’s current quest). Where gyrotrons normally run for no more than an hour a day, this gyrotron will need to run 24/7, with all the power transmission and cooling that that requires. Although gyrotrons are designed to operate continuously, Woskov said, nobody has demonstrated it before. And these problems, though difficult, are – as it were – surface-level. Quite what it’s like 20 kilometers down, even if they make it that far, is anyone’s guess. ‘We’re going to a place nobody’s ever been,’ said Araque. ‘How do you know what it’s made of? It’s like man touching down on the Moon for the first time.’
In the first week of March 2023, Araque’s team hit a significant milestone. With the help of a millimeter wave, they vaporized a hole 100 times deeper than its diameter, reaching a depth of ten meters. It’s a long way from 20 kilometers, but it was 100 times deeper than Woskov’s earliest holes, and it was the landmark the team needed to reach before taking their work into the field.
In the race to reliably access superhot rock geothermal, Quaise is the front-runner. But their method is one of several that might work, and humanity needs only one to be successful. Sometime soon, drill bits like those I saw in Cornwall will be as useful for deep drilling as the ox is to modern farming. We can’t know which method will render those drill bits obsolete, but one of them will. Work is underway to penetrate kilometers of rock by blasting it with plasma, battering it with ball bearings, or burning it with a flame jet. Encouragingly, work on some of these ideas have had funding from the US government’s Advanced Research Projects Agency for Energy (ARPA-E), which has also part-funded Quaise. Other funders would be wise to make similar investments.
These novel drilling methods would need to be complemented by progress in related technical areas. One of those is the scanning of subterranean materials and temperatures – which AI is already helping with. Another is the improvement of downhole technology – the kit that isn’t a drill but still needs to go deep into the bedrock. Such kit includes sensors that can tell rig operators what’s going on down there – sensors that, in superhot rock geothermal, will need to operate at high heat, under high pressure, and when caked in the ‘unholy sludge’ of corrosive subterranean minerals. Luckily, many of those technologies are being developed to help frackers exploit the USA’s abundant shale oil.
Crack the nut of geothermal power and it will feed us for billions of years: the Sun will engulf us long before the Earth’s core stops providing us with heat. In the here and now, a successful geothermal industry would mean a neat repurposing of oil and gas infrastructure and expertise; little prospect of Putin-style energy blackmail; and, most importantly, abundant clean energy, available 24/7, regardless of geography. Perhaps equally thrillingly, we would have drilling that would make the Soviets’ Arctic Circle record breaker look like a hobbit hole.