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Geothermal energy could save the planet. But watch for earthquakes

Burrowed 1.5 km beneath a valley in Ticino, a region of southern Switzerland close to the Italian border, the Bedretto Underground Laboratory for Geoenergies is part mechanics garage, part construction and excavation site. Inside the six-by-three metre cavern – which was once part of a railway tunnel – a team of researchers specialising in geology and seismology conduct their work wearing hard hats. This is one of the world’s leading research facilities in deep geothermal, a renewable energy source that has the potential to upend our reliance on fossil fuels.

“I’m sorry it’s a bit of a mess today,” says lab manager Marian Hertrich, referring to the motors, laptops, giant spools of fibre optic cables and drill rig that compete for space in the tight quarters. For a man who spends half his life underground, the German geophysicist is suspiciously tanned.

The lab is situated in an abandoned ventilation arm of the Furka base tunnel, operated by Swiss railway company Matterhorn Gotthard Bahn. One end disappears into inky blackness, the other to dimly-lit railway tracks, where a team dressed in high-viz overalls are ferried in and out to the southeastern exit of the five-kilometre-long tunnel on a custom-made trike that affixes to the steel rails. Half the adventure is getting here. The 40-minute walk in is unnerving, with pools of water underfoot and 16,000 volts running in cables overhead. On one part of the tunnel wall you can see where a mass of molten magma forced its way through a long rupture millions of years ago – a feature marked by a vertical join between two different rock types. One is Rotondo granite – an immense physical barrier which engineers tunnelled under 50 years ago.

“One of the reasons I chose Bedretto as a tunnel is because it has two exits. I don’t want to have a landslide or an avalanche,” says Domenico Giardini, professor of seismology and geodynamics at Swiss university ETH Zürich. “If you want to operate a lab under a mountain for 20 years, it needs to be very safe.”

A leading authority on deep geothermal energy, Giardini is the brains behind the pioneering underground rock lab, a collaboration between ETH Zürich and the Werner Siemens Foundation, which provides funding for research projects and is the lab’s main financial backer. Inaugurated in May 2019, the lab’s mission is to explore the potential of geothermal energy – a renewable energy source buried deep underground.

By inducing tiny artificial tremors known as micro-quakes and seeing how the underground rock behaves, the team hopes to finally crack how to make this overlooked, underutilised renewable safe and economically viable over the long-term, and to tap into a new supply of clean energy that could help Switzerland – and other countries – relinquish reliance on fossil fuels.

Marian Hertrich, the lab manager of the Bedretto Underground Laboratory for Geoenergies

Felix Wey

Described as the sun beneath our feet, geothermal (a portmanteau of ‘earth’ and ‘heat’ in Greek) is the residual heat from molten rocks formed within the Earth’s interior billions of years ago. Geothermal energy converts this natural heat percolating deep underground into electricity.

Humans have been tapping into geothermal for thousands of years. Ancient Romans harnessed its powers to heat rooms, bathe and even treat skin diseases in Pompeii. Today, the world’s oldest geothermal field, Larderello in Tuscany, still generates 10 per cent of the total global geothermal energy supply. The World Energy Council estimates that geothermal has the potential to deliver more than 8 per cent of the world’s electricity needs. But it still has the status of an outsider, accounting for only 0.3 per cent of globally installed renewable energy capacity, mainly due to seismic risk, the drawn-out experimental phase and high start-up costs.

On paper, geothermal sounds too good to be true. Our planet will most likely supply heat for millions of years to come, and, unlike solar and wind, geothermal doesn’t rely on the fickle climate above ground. “If you go one metre down, the rock doesn’t know if it’s night or day,” Giardini says. “If you go three metres down, the rock doesn’t know if it’s winter or summer. It doesn’t know anything at all because the rock is so efficient at retaining heat.”

Geothermal pulled clean energy innovator Iceland out of economic ruin in the 70s, by enabling the country to transition from expensive fossil fuel imports to generating 80 per cent of its own electricity and heating. Today, nine out of ten Icelanders live in geothermally-heated homes. But Switzerland isn’t a volcanic island where scalding hot water can be drawn out just a few hundred metres under your feet. In this land-locked, mountainous country, you need to go deep – around 3,000 metres into hard crystalline rock – to hit temperatures of 100 degrees Celsius.

Geothermal energy could save the planet. But watch for earthquakes

The entrance to the Bedretto ventilation tunnel

Felix Wey

An enhanced geothermal systems (EGS), also known as “hot rocks”, is a type of deep geothermal system designed for less tectonically active regions such as Switzerland. EGS works by injecting water at high pressure into the Earth’s bedrock, where it absorbs the heat from these “hot rocks”, before being recovered via a shaft bored into the ground. Unlike conventional geothermal systems that harvest heat from porous rocks where hot water naturally flows, EGS has to artificially engineer permeability. The technology was first trialled in New Mexico half a century ago, but has only seen incremental gains in this time. EGS could, in theory, unlock untold stores of heat from almost anywhere in the world. The International Energy Agency (IEA) estimates that the heat flowing into the top few kilometres of the Earth’s crust amounts to more than two million times the world’s annual total energy consumption.

In 2050, every one of Switzerland’s 26 cantons is poised to run on partial geothermal power, with a view to phase out nuclear energy, which currently supplies 40 percent of Switzerland’s energy needs, and replace fossil fuels. According to the Swiss Federal Office of Energy, which invested £47 million into geothermal projects in 2020, Switzerland already has the highest concentration of heat pumps per square kilometre in the world, supporting almost 15 per cent of Swiss heating systems in homes and offices. But heat pumps fall under the umbrella of “shallow” geothermal, which harnesses warmth emanating from the Earth’s crust between 1.5 and 400 metres below ground. “Deep” geothermal projects like EGS, on the other hand, require drilling down to depths of 5,000 metres.

In this respect, Switzerland may have an unexpected ace up its sleeve – a vast network of underground tunnels. Built by the armed forces as part of the country’s now retired “Swiss Reduit” defence system, these alpine fortresses are how Switzerland came to bunker itself into the Alps during World War II. In the last few decades, some of the tunnels have been repurposed for high security storage – outfitted with bulletproof vaults to stow away gold. But the former military bunkers of the Saint-Gotthard Massif mountain range could also serve as portals to a green energy source ripe for harvesting.

“Underground labs are usually expensive affairs, because you need to reach them first,” Giardini says. “That’s where having a ready-made tunnel comes in handy.”

Geothermal energy could save the planet. But watch for earthquakes

Cables snake out of boreholes lined with sensors

Felix Wey

There’s one major issue with enhanced geothermal systems: earthquakes. The reputation of geothermal power in Switzerland nosedived in 2006, when the city of Basel was rocked by a 3.4-magnitude earthquake triggered by a pilot project. The uncontrolled tremors were a result of Geopower Basel pumping pressurised water up to 4.8km underground prospecting for geothermal. While there were no serious injuries, the quake shattered roof tiles and rendered cracks in buildings in the city of medieval cathedrals, which sits atop a 125-metre-long active fault (a natural earthquake along the fault in the 14th century flattened the city). Months after the plug was pulled on the operation, sensors recorded thousands of tiny quakes, which were attributed to the deep geothermal project.

The ground trembled again in 2013, this time 200 km east in the city of St. Gallen, during the drilling for a £135 million-funded EGS project that was shelved shortly after.

The Bedretto lab is running research and exploring techniques to try to make the most of deep geothermal without running the risk of another incident. In November 2020, Bedretto began its first full-scale stimulations, which are known to cause tiny levels of shaking (imperceptible without scientific measuring equipment), or “micro-earthquakes.” A stimulation involves creating a network of cracks in the granite by injecting a few tens of cubic metres of cold water through it. “When you run an experiment, there are maybe 10,000 small quakes, and you need to locate them in real time,” Giardini says.

The location of these experiments is a small pool excavated at the tunnel’s base, which could easily be mistaken for an underground spring. But rather than cave-dwelling fish, cables sprout out from two 22cm boreholes drilled 300 metres deep at 45-degree angles into the granite to access reservoirs – not the spectacular alpine kind that Ticino is known for, but heated underground ones, created artificially by pumping water at high pressure to prise open cracks (known as fractures) into less permeable areas of rock. These cracks act as a radiator, transferring heat in the rock to the water, which, in the case of geothermal plants, is then piped back up to the surface of the Earth, where it evaporates into steam. The steam rotates the blades of a turbine, in turn activating a generator which creates electricity that can be directly transported via conventional power lines. A renewable in the most literal sense, the condensed steam can even be pumped back underground, restarting the cycle.

Lining the boreholes are different types of sensor, including acoustic and pore-pressure (which measure the force of the water as it runs through the cracks), as well as fibre optic cables and geophones (which detect ground velocity produced by seismic waves). Together, these monitor and record vibrations in the granite as the water is injected into sections of the borehole. This data helps to map out the rock’s permeability by revealing the fracture’s size, characteristics, quantity, direction and stress capabilities under different water pressures. Knowing to what extent the granite can be made ‘artificially permeable’ will inform whether a reservoir that stands up to geothermal extraction can actually be made.

Geothermal energy could save the planet. But watch for earthquakes

Scientists work at a borehole that has been drilled at a 45° angle

Felix Wey

For now, the lab is pumping in liquid at 17°C, with hot water experiments scheduled later in 2021, in conjunction with Bedretto tunnel’s second lab opening. Eventually, sufficient fractures will have been made in the rock to connect the two boreholes, creating a reservoir of heated underground fluid, where the full EGS process can be tested and studied.

By using long boreholes to create underground reservoirs at the 100 metre scale, Bedretto is conducting experiments under conditions that more closely mimic those of a geothermal power plant. And by dividing the boreholes into different sections, the team is able to conduct multi-stage stimulations, which should, in theory, limit the seismic risk by giving the researchers more control.

“I think the biggest event so far was -3.2 or something,” says Ben Dyer, a seismologist for Geo-Energie Suisse, one of Bedretto Lab’s partners. To put these numbers in context, magnitudes need to reach around 2.5 before they’re perceptible above ground. “I think to be honest, when you get beyond zero through the rock, we’d hear the cracks [in the lab],” Dyer says. Anything less than that is considered a micro-quake. These are scrutinised nonetheless, displayed in real-time as a series of squiggly lines or “seismic waves” on an ECG-like monitor.

Erring on the side of caution, Bedretto has installed five seismographs (devices which measure the movement of the Earth) in the tunnel’s interior: one at the entrance, one at the end, and three directly in the lab, as well as three new seismographs at the Furka, Nufenen and Gotthard Alpine passes. ETH’s own seismic risk study concluded there would be a 1 in 10 million chance of a magnitude 2-2.5 earthquake being triggered. But, as Giardini plainly says, “Small risk doesn’t mean zero risk. It’s really very difficult to introduce any new technology unless you really prove there is no risk.”

The line between inducing artificial tremors to yield sufficient data, and triggering an earthquake that could derail the entire project, is a fine one. Research at Bedretto has potential to drive down the costs and risks associated with the discovery of geothermal heat. But by the same token, any negative incidents could give pause to investors in geothermal projects. “The best thing that could happen to geothermal in Switzerland would be to have one project that finally works, with no snags,” says Elmar Grosse Ruse, a climate expert from World Wildlife Fund (WWF) Switzerland.

Geothermal energy could save the planet. But watch for earthquakes

Hazel Gibson, former postdoctoral researcher at Plymouth University’s Sustainable Earth Institute, has dedicated the past two years to finding out how to manage public trust in geothermal technology. “In the case of deep geothermal, not only is this space invisible, it’s also completely alien to most people, who don’t think about what is going on under their feet until they need to,” she says. “It’s unfamiliar technology, and unfamiliar risks are often subjectively judged to be more risky than familiar ones.” She adds that the language associated with geothermal – words like “fracture”, “fault”, “earthquake” and “seismic” – can be daunting.

But for the residents of Bedretto Valley, avalanches are a far more tangible threat than a minor quake. Bookended to the west by Nufenen, Switzerland’s highest paved alpine pass, and to the east by the town of Airolo in the southern foothills of the Gotthard Pass, the valley is streaked with steep gullies and meandering rivers, where a quartet of villages are bunkered into the hillside.

Scarcely 500 metres from Bedretto Tunnel’s south east entrance is the chocolate-box hamlet of Ronco (home to just four permanent residents) and 3 km down the road, 13th century hamlet Villa – which went as far as to remodel its church bell tower to serve as an avalanche breaker. The days of being evacuated on mule-drawn sleighs may be long gone, but Agnese Leonardi – who lives here with her two teenage sons and husband Marco – recalls how snowdrifts came right up to the second floor of their larch timbered home one winter, rendering them snowed in, in the most literal sense. They run the nearby Cioss Prato ski lift and a grotto at its base, which is ornamented with 15-million-year-old crystals, dredged from the depths of the Gotthard by Agnese’s crystal hunter father-in-law, Gilberto Leonardi. The family know more than most about the unusual properties of the ground beneath their feet, and yet look blank at the mention of Bedretto Lab, despite it being on their doorstep.

The lab says it’s been fully transparent about its activities. At its unveiling in May 2019, more than 300 people from the public (including Bedretto Valley’s residents) were invited to visit and chat one-to-one with the team’s researchers. But with Covid-19 hitting pause on these tours for the best part of 2020, some residents remain in the dark.

“The idea that if scientists provide more information then people will automatically feel more comfortable with a scientific idea is not really true,” Gibson, who is not directly involved in the Bedretto project, says. “What is more important to help people connect to new scientific ideas is the way we communicate.” Social solutions, she says, are just as important as technical ones.

Getting a community of 106 like Bedretto onside is one thing, but convincing a city with a population of 200,000, like Geneva, is another. People have an inherent fear of earthquakes. “All of our system is based on the fact that everything below us is stable, otherwise we feel sick immediately,” Giardini says. “It’s not so different from the fear of sharks. You are on the beach, and say there is a dolphin, everyone comes to take a picture. You say there is a shark and people fly out of the water, even if the two are equally dangerous.”

But despite incidents like that at Basel, “geothermal still has an image of a clean, silent source of energy in Switzerland,” Grosse Ruse says.

The environmental community is also generally onside with geothermal, despite controversy over some projects imperilling freshwater resources, like New Mexico’s Lightning Dock plant. “Although engineered geothermal does involve some processes that are similar to fracking, they don’t require the addition of possibly hazardous chemicals below ground,” explains energy expert and author Chris Goodall.

Geothermal energy could save the planet. But watch for earthquakes

Currently, geothermal is a bit-player in Switzerland’s energy production, alongside wind and solar, which account for 8.5 per cent of total energy consumption, and hydropower, which generates 60 per cent of the country’s domestic electricity production.

Often referred to as the water tower of Europe, Switzerland is primed for hydropower, thanks to its mountainous terrain and high levels of annual rainfall. But Grosse Ruse says there is a need for something new. “There’s not much potential left for ‘more’ hydropower in Switzerland. Those projects have such a high detriment on the rivers and biodiversity,” he says. “And with hydropower, we know that even if receding glaciers continue at the pace they are at the moment, the capacity would still be very limited in the next two decades.”

Different countries may have different reasons to opt for geothermal over other renewables. “It is possible that geothermal may never become cost competitive with solar and wind in somewhere like the UK,” Goodall says. “Whereas, say, in Kenya, it is a real competitor because temperatures close to the surface are so much higher.” Giraffes and geothermal happily co-exist in Hell’s Gate National Park in the Great Rift Valley, where steam generates close to half of the East African country’s electricity. When it comes to surface footprint, geothermal plants also take up considerably less space than solar or wind farms, and their underground reservoirs serve a dual purpose – hoarding both energy and carbon dioxide.

But despite the list of pros, many geothermal projects never make it past the exploratory phase, which only pays off if sufficiently hot and abundant water reservoirs are uncovered. Australia’s flagship geothermal developer, Geodynamics Limited, learned this lesson the hard (and expensive) way, investing £110m drilling five-kilometre-deep wells into South Australia’s Cooper Basin that are now plugged with concrete.

Even at Bedretto’s modest 1,500-metre depths, the early engineering challenges – before stress levels in the rock were even measured – were hairy, lab manager Hertrich recalls. “We drilled and drilled (into the rock) and metre by metre it was completely dry,” he says of their preliminary excavations. “We left it open for two weeks and not a single drop of water came out. I was really concerned. Then all of a sudden we drilled through a fracture zone, and then the fun began.”

One knowledge gap that still needs to be filled is where the best sites are for developing large-scale EGS. Production-scale deep drilling remains the ultimate test of a geothermal prospect. “The problem was getting a drill to fit in here,” Hertrich says. In the end, the team commissioned a Swedish company to manufacture a drill rig from scratch tailor-made to the tunnel’s exact specifications. Whilst he won’t disclose the cost, the geophysicist says that hiring a geothermal drilling rig can set companies back £100,000 a day. The vast majority of EGS projects are stalled by the capital costs; generating backing for the lab was swift by industry standards. Bedretto’s main sponsor, the Werner Siemens Foundation, invested £3.3 million in the lab infrastructure alone, while a raft of other investors, including the Federal Office of Energy and European Research Council, contributed a further £6.5 million. A significant cost saving has been rent-free-premises, thanks to the Matterhorn-Gotthard-Bahn, which granted ETH Zurich unlimited use of Bedretto tunnel for the next decade.

Another of the Bedretto lab’s main challenges (shared by other deep geothermal energy projects) is a technological one; namely data acquisition and realtime analytics. “Currently, the independent software for analysing hundreds of data streams of seismic data, sampled with as high frequencies as 1 MHz, in real time, doesn’t exist,” Bedretto’s Head of IT, Philipp Kästli, says. To deal with this, the Bedretto team has written its own.

“This isn’t the kind of data you can put on a stick,” Giardini says, referring to the 12TB of uncompressed data generated by the lab on an average day. “We are metres away from the borehole, so what we see is extremely high frequency. This frequency would usually be taken away by the friction inside the earth so you wouldn’t see it.” This seismic data is read and transported back to ETH’s headquarters in Zurich in real-time – the only way to send it, since the cumulative amount would simply overwhelm the system. “We need to transfer continuously in order to bring this data back from this remote mountain area to Zurich, without re-cabling the landscape,” Kästli says.

Geothermal energy could save the planet. But watch for earthquakes

These ten-centimetre-diameter cores of granite were excavated in 2019

Felix Wey

The most important thing if deep geothermal is to become more mainstream is understanding the geology. Hertrich and his team have committed to learning the behaviour of Rotondo Granite inside out, under every possible rock stress scenario. “Usually you drill in the dark. You drill, you install (boreholes) and then you stimulate,” he says. Not at Bedretto. Propped up against the tunnel’s exposed walls are dynamite-like crates containing 10cm diameter cores of granite excavated from experimental boreholes in May 2019. These salt-and-pepper samples have been scrutinised for every vein, pore, joint and fracture for nine months, by some of the industry’s keenest eyes. The drilled cores are being used to learn where and how to create fractures for Bedretto’s heat reservoirs, so the team can manipulate the rock’s behaviour in the way they want to. Such a level of geological, geophysical and geochemical surveillance is nudging geothermal into new territory.

In reality, it’s still a long and expensive process to get from lab to plant. The Bedretto lab has no intention of building a commercial geothermal plant on site, although next summer it hopes to extricate hot water from the experimental research reservoir for heating and electricity generation (depending on the temperature), in conjunction with a regional electricity provider.

Whether or not a world in the throes of a climate and energy crisis can afford to wait for geothermal to commercially mature remains to be seen. Whilst shallow geothermal covers 1.3 per cent of Switzerland’s heating needs at the moment, that’s not nearly enough to fill the 40 per cent energy shortfall that nuclear will leave behind in 2050. The Bedretto lab is slated to run until 2024, so electricity isn’t going to be generated overnight, and presently, there are no operational deep geothermal plants in Switzerland. The planning and construction of a typical heat-and-power geothermal plant can take up to six years and their outlay can be in the region of £50m.

But the patience and investment could pay off, especially if companies can identify areas where drilling is more likely to hit geothermal pay dirt. This is something Bedretto’s research will directly inform in other regions of Switzerland, as well as Scandinavia, which shares a similar rock geology.

If the hard data retrieved from in-situ stimulations like Bedretto can bolster public and investor confidence, it has the capacity to spark an energy revolution, starting with fast-tracking the deployment of geothermal power in its home country.

Giardini is well aware that success or failure here could well determine the fate of deep geothermal energy in Switzerland, and possibly beyond. “Usually failures are the ones that end up in the newspaper,” he says. “If you have a 2.5 magnitude earthquake, everyone will know.”

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