I was waiting to hear this was going to happen

GREG LAUER

LONDON (Dec. 18) -- The Obama administration has a lot riding on geothermal energy, which it sees as a future source of clean, green and virtually unlimited electricity. Over the past year alone, the U.S. Department of Energy has invested some $440 million in projects trying to turn heat trapped in bedrock deep underground into electricity. But the trial this week of a Swiss geologist – accused of causing earthquakes during the construction of a geothermal power plant – has raised doubts about the safety of some geothermal schemes, and may have contributed to the collapse of one government-backed project in California earlier this month.



Worries about the link between this new power source and earthquakes came to the fore in 2006, when the building of a geothermal plant in the Swiss city of Basel triggered a series of tremors. Although no one was injured, the quakes caused $9 million in damage and seriously shook the locals. On Tuesday, Swiss prosecutors opened their case against Markus Haering – head of Geothermal Explorers, the firm behind the project – who they accuse of deliberately causing landslides and damage to property. He denies all charges and could face up to five years in prison if found guilty.



When construction of the geothermal plant began in 2006, few residents of Basel, a prosperous city on the border with France and Germany, would have believed it would end in earthquakes and court cases. Residents were told that a new, cutting-edge technology known as an enhanced geothermal system would be used to create enough power for 10,000 homes.

<img /> Manny Crisostomo, Sacramento Bee / ZUMA PressAn ambitious project to tap geothermal power at The Geysers in northern California was suspended after reports of earthquakes at a similar project in Switzerland.

Traditional geothermal plants tap water trapped in hot rocks relatively near the surface. The Basel project aimed to harness the energy from a hot layer located three miles below the city made of water-free, impermeable rock. To generate power, Basel would have to pump water down a deep borehole. On reaching the layer of superheated rocks, the water would turn to steam, race back to the surface and be used to spin electricity-generating turbines. Leftover hot water would heat nearby homes.



The first stages of the project went smoothly. By December 2006 the well had been drilled and Geopower Basel was starting to pump in pressurized cold water, which was supposed to open up fractures in the rock, creating pores for water to run through. It was then that Basel started to suffer the shakes -- the greatest of which was recorded at a house-moving 3.4 on the Richter scale -- forcing the company to stop pumping.



Paul Younger, a professor of energy and environment at Britain's Newcastle University, says that it's not unusual for much smaller tremors to be felt on the surface when pressurized water is forced into rock deep underground. But, he adds, the process is normally only carried out in seismically stable areas, as the shakes caused by hydro-fracturing can interact with existing deep faults and cause larger trembles.



And Basel is anything but stable. The city has a long history of quakes and was all but wiped out in 1356 by an estimated magnitude 6.5 earthquake – the largest ever known to have occurred in Western Europe. "What they were doing was actually fairly conventional," Younger says. "It's where they were doing it that was unconventional. If you go drilling and stimulating near a known active fault, you're asking for trouble."



The Basel plant, which was finally closed on Dec. 10, didn't just cause trouble in Switzerland. On Dec. 11, U.S. firm AltaRock Energy shut down a California geothermal project known as the Geysers that was based on a similar design as Basel. The Energy Department – which supplied $6 million in funding – had been investigating the project's safety following reports by federal officials that the company had failed to supply sufficient information about the Basel quakes when applying for the go-ahead. But AltaRock also had other serious engineering problems at the site: It couldn't break through shallow formations known as caprock to reach the hot strata.



Experts accept that the closure of Basel and the Geysers is a setback for geothermal power. But, says Colin Williams, a research geophysicist at the U.S. Geological Survey, neither closure "is a showstopper." He says the technology behind projects such as Basel is still at a relatively "early stage." And while he has no doubts it will eventually be advanced enough to use in urban areas, "it's wiser that we do this in less sensitive locations at the moment, so then we can build up a series of case histories."



Younger believes a key advantage geothermal holds over most green energy sources – that it can be on 24 hours a day – means new projects will continue to spring up around the world. "It's not dependent on wind, tide or sunlight," he explains. "That means that it can deliver baseload power much like an ordinary fossil-fuel power plant." Or possibly more. According to a 2007 Energy Department report, advanced geothermal power in the U.S. could – at least in theory – produce up to a staggering 60,000 times the country's current annual energy usage.



That explains why Switzerland and the United States still have the hots for geothermal, despite the Basel quakes. AltaRock has received some $25 million in U.S. government funding to start a new project in Oregon, and the Energy Department is backing more than 120 geothermal initiatives across several states. Engineers in Zurich, meanwhile, started drilling last month to see whether the area was suitable for a new scheme. Geothermal, it seems, could still shake up the world. But in a good way.