Is Geothermal Ready to Rock?

I’ve posted recently on the efforts, through various schemes, to jump start nuclear power. I do wish them luck.

That said, nuclear will face keen competition, not only from cheap-and-getting cheaper solar, wind and batteries, but often ignored Geothermal technology, which is right now reaching the place where fracking was in about 2007, where solar was in about 2014, and where batteries were about 2 years ago – in other words, poised, perhaps, for a major, market changing breakout.

Economist:

 Geothermal Energy may be approaching its Mitchell moment. George Mitchell, a scrappy independent oilman, is known as the father of fracking. Nearly three decades ago, he defied Big Oil and the conventional wisdom of his industry by making practical the hitherto uneconomic technique of pumping liquids and sands into the ground to force out gas and oil from shale rock and other tight geological formations. The enormous increase in productivity that resulted, known as the shale revolution, has transformed the global hydrocarbon business.

Now Fervo Energy, another scrappy Texan upstart, is applying such hydraulic fracturing—alongside other techniques borrowed from the petroleum industry—to the sleepy geothermal sector. Should it succeed, it would mean this relatively fringe source of energy could, in time, become a major player in the energy mix.

The motivation behind geothermal energy is to harness Earth’s abundant subsurface heat for useful ends. This is ordinarily done by tapping into underground reservoirs of hot water or steam. As these are only found in limited areas, this greatly limits the potential of conventional geothermal power. In contrast, “enhanced geothermal systems” (egs), like the one deployed by Fervo, use hydraulic stimulation to create channels in hot rocks just about anywhere. One well pumps in water into those channels, where it is heated naturally to 200°C or higher. Another well then brings that hot water to the surface, where it is used to generate electricity in a turbine.

The approach has its challenges. For one thing, reaching sufficiently hot rocks can involve drilling for four or more miles underground, which gets expensive and technologically complex—and takes time. In addition, as with all fracking projects, there are localised risks of minor earthquakes (one egs experiment conducted in Switzerland in 2006 led to a tremor with a magnitude of 3.4). And because egs introduces water from the surface rather than relying on pre-existing pools underground, it can contribute to water stress in dry regions.

Despite the challenges, the hot shots of hot rocks are finding success. Last year Fervo successfully completed a pilot project in Nevada, and secured Google as an early customer. In June it confirmed that Southern California Edison, a big power utility, had agreed to buy 320 megawatts of power from its much bigger new project in Utah, which aims to apply mass-manufacturing methods to scale the pilot technology. The deal is the largest-ever power purchase agreement for geothermal energy.

On September 10th Fervo revealed yet more good news. Despite needing to drill much deeper at its Utah site, it was able to do so in just 21 days, slashing its drilling time by 70% relative to the Nevada site. It was also able to drill the fourth of its wells at half the cost it took to drill the first, mainly thanks to “learning by doing”. The firm has already outpaced the targets America’s Department of Energy (DOE) set for geothermal energy producers to reach by 2035.
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How big could egs get? Big enough. Though doe analyses suggest only around 40gw of conventional geothermal resource exist in America, new techniques expand the theoretical potential to a whopping 5,500gw across much of the country, with strong potential in over half of states. The heat is definitely on

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Alternative to Fervo’s “Enhanced Geothermal”, another horse in the technology race is “Advanced Geothermal”, which does not involve fracturing rock, but instead on precision drilling to create something that looks like a deep rock radiator, that can transmit heat to water in the drilling loop.

Anthropocene:

There are two major schools of thought. One category includes efforts like Eavor’s, known as “closed-loop” or “advanced” geothermal systems (AGS). Their goal is to drill a circuitous borehole that is filled with water and conducts heat to the surface. “We’re hermetically sealed,” Redfern explains. “We have no water going in or out of our system into the rock.” The challenge is in transferring enough heat from the rock, which will cool in turn, until its heat is replenished from the fiery depths. To make a sustainable system, you need a lot of surface area and thus, to lay a lot of pipe.

In the other category, enhanced geothermal systems (EGS) rely on two deep parallel holes that are drilled out then “fracked” with a high-pressure blast of water. This cracks open fissures in the rock between the two holes. Engineers are often fans of this approach because it’s an efficient way to create lots of surface area for water to come into contact with hot rock—so much area that the water can be pumped through the system much faster without cooling the surrounding rocks too much. Unlike fracking for oil and gas, the water is typically recycled after each use. Historically, though, EGS has been hampered by the challenges of precisely engineering those fractures. Some projects failed when water disappeared into hidden faults and never returned to the surface, others when the fracking produced damaging earthquakes.

“There’s this big debate, and sometimes it gets pretty intense,” says Koenraad Beckers, a geothermal researcher at the National Renewable Energy Laboratory. “Some people say AGS is the holy grail but others say it’s EGS.” Recently, he adds, EGS has taken a clear lead, especially in the U.S., where it is the darling of both government research efforts and investors, with startups like Fervo building out large-scale systems in the American West. Because they don’t require drilling such vast distances, EGS also has the benefit of being more cost-efficient to drill in very hot rock, where drilling even a small distance is especially challenging and expensive. That’s a key advantage for producing power, because the hotter the water is, the easier it can be converted into electricity.

Hence closed-loop AGS as the “other idea,” in more senses than one. Roland Horne, a professor of earth science at Stanford University, has watched people attempt closed-loop ideas for about a half-century. He was recently part of a DOE-backed analysis that found that making all the extra pipe required of deep closed-loop systems worth it would require drilling costs to drop by half. Consider him skeptical. “If they do it, it would be a tremendous advance,” he says.

Then again, drilling costs are falling more rapidly than anyone in the industry imagined. In 2022, the DOE set a goal of shaving 90% off the cost of EGS technology by 2035, which seemed ambitious at the time. Fervo recently reported that costs were falling faster than required to reach the agency’s ambitions. “If you’d asked me two years ago if it would be possible, I would have said no,” Horne says of closed-loop efforts. Nowadays—maybe.