Knowable Magazine ran an article by Katarina Zimmer on geothermal energy. Long regarded as just a small source, to be applied in selected places; but now more a versatile technology, able to complement sustainable sources. Thanks to new technologies.
A niche source of energy
Zimmer starts off with a description of Project Red, a site in the Nevada desert, that pumps water thousands of feet into the ground, ‘down where rocks are hot enough to roast a turkey’. And then, the structure sucks the heated water back up; it is hot enough to power generators.
For quite some time, geothermal energy has been a relatively niche source of electricity. It was largely limited to volcanic regions like Iceland, where hot springs bubble from the ground. But now, producing geothermal energy appears to be profitable in other regions as well. Thanks to enthusiasts who succeeded in driving the price down. Some experts hope that newer efforts like Project Red may now have become cheap enough to signal a turning point. Thanks to techniques that were developed in oil and gas extraction.
Driving prices down
At present, geothermal energy accounts for less than 1 percent of the world’s electricity. But it could develop into a valuable tool in transitioning the energy system away from fossil fuels: it can provide a continuous backup to intermittent energy sources like solar and wind.
But then, it needs to be cheap enough. For that, it requires hot rock, that is permeable enough to carry water. If the water or steam is hot enough — ideally at least around 150oC — it can be extracted from the ground and used to power generators for electricity. There are places where this is already done. Knowable Magazine signals that in Kenya, nearly 50 percent of electricity generated comes from geothermal. Iceland gets 25 percent of its electricity from this source, while New Zealand gets about 18 percent and the state of California, 6 percent.
It’s access that counts
But as easily accessible geothermal energy is running out, mankind needs to develop new techniques to tap this resource. And that is exactly what engineers have been developing over the past fifty years. Geothermal energy is there in major quantities – it’s access that counts. For that, dense rock needs to be ‘fracked’ in order for water to be able to permeate it and get heated up. The art of fracking has been developed in the oil and gas industry and is now ready to be applied in the geothermal field. Water is pumped at high pressure into wells, up to several miles deep, to blast cracks into the rocks. The cracked rock and water create an underground radiator; there, water heats before rising to the surface through a second well.
Over the past decades, many such wells have been drilled. Notably in the United States, Europe, Australia and Japan. Most of them were experimental and government-funded. Experiences were mixed. In South Korea there was a severe earthquake near one borehole. Probably, the fracking had promoted a nearby tectonic fault. The well was immediately closed down. Some other wells didn’t create enough fractures for good heat exchange. Some fractures travelled in the wrong direction and failed to connect the two wells.
Geothermal electricity
Some efforts, however, turned into viable power plants, including several German and French systems built between 1987 and 2012 in the Rhine Valley. There, engineers made use of existing fractures in the rock. But overall, there just hasn’t been enough interest to develop geothermal power into a more reliable and lucrative technology, says geophysicist Dimitra Teza of energy research institute Fraunhofer IEG in Karlsruhe, Germany. She helped develop some of the Rhine Valley EGS systems. ‘It has been quite tough for the industry.’
Geothermal electricity has long been limited to volcanic regions where underground heat is easily accessible. But the drilling and fracking methodology has improved by leaps and bounds, thanks to the boom in oil and gas extraction from shale rocks that began in the 2010s. For instance, engineers drilled almost 8,000 feet downward into the Nevada rock, reaching temperatures of nearly 380 degrees Fahrenheit. At the bottom, they drilled a 3,250-foot horizontal well to expand the area of hot rock that the system touches. This technique is used in oil and gas extraction in order to maximize yield. To this, they added fracturing of the surrounding rock at several sites, to create a more extensive web of cracks for water to trickle through.
Profitability
But then, how profitable will these new systems be in the long term? One advantage is that operators can plug exit wells. This will build up pressure and heat. The energy can then be released when it is most valuable. In combination with solar and wind energy, for instance, geothermal energy might be used on cloudy days without wind.
Still, geothermal systems will have to be scaled up to become profitable. In the US this may be advanced by an award of $60 million in funding to three demonstration projects. And ambitions are high. According to the American agency, geothermal power could represent around 60 gigawatts (60,000 megawatts) of installed capacity in the United States by 2050. This would generate 8.5 percent of the country’s electricity — a more-than-20-fold increase from today. This would add substantially to the move toward net zero carbon emissions by 2050.
More advanced technologies
More advanced technologies might play a part in this future. Some companies are exploring the feasibility of ‘super hot rock’ geothermal. This implies drilling down even deeper into Earth’s crust; to a depth where water reaches a supercritical vapor-like state that allows it to carry much more energy than either steam or liquid. A test with such a system is held in southern Germany.
And geothermal systems may carry other advantages. For instance, the brine that they haul out of the Earth may be rich in lithium and other critical minerals – materials used to build green technologies like solar panels and EV batteries. On the whole, geothermal energy is on the rise. Even oil and gas companies now think about diversifying into geothermal energy.
Interesting? Then also read:
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