From Works in Progress, November 15, 2023:
The earth’s core is hot. So hot, that if we drilled deep enough, we could power the world millions of times over with cheap, clean energy, supporting renewables when the wind isn’t blowing and the sun isn’t shining. But getting there is tough.
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....
....MUCH, MUCH MORE
And for all the young people out there, kids you don't have to be smart to make money.
As Al Gore said when interviewed by Conan O’Brien:
Conan: ” …Can you, can you tell me, is this a viable solution, geothermal energy?”
Al: “It definitely is, and it’s a relatively new one. People think about geothermal energy — when they think about it at all — in terms of the hot water bubbling up in some places, but two kilometers or so down in most places there are these incredibly hot rocks, ’cause the interior of the earth is extremely hot, several million degrees, and the crust of the earth is hot”
http://www.youtube.com/watch?v=14kNtnJgXXM
Mr. Gore was brought in as a partner at Venture Capital firm Kleiner, Perkins, Caufield & Byers which is a major investor in geothermal tech company Altarock.
I’m guessing Mr. Gore was not brought in for his scientific expertise.
