Scientists said on Thursday that because the Swiss report focused narrowly on the Basel project and also contained positive findings, it would not prove fatal to advanced geothermal energy as a whole.The California project was shut down for its quake hazards as well.
For example, while the report concluded that residents of Basel would have felt from 14 to 170 earthquakes over the 30-year life of the project, few if any of those earthquakes would be likely to cause bodily harm, according to an English summary of the report provided by Rudolf Braun, the Swiss scientist who led the work.
The report also concluded that the Basel project was very unlikely to activate one of the major faults around Basel and generate a huge quake like the one that devastated the city in 1356. On the other hand, the report also found a 15 percent chance that the project could set off an earthquake that could cause over half a billion dollars in damage. Every year, the project would probably produce some $6 million in damage, the report found.
“As for Basel, it is clear that this project has been buried,” said Nicholas Deichmann of the Swiss Seismological Service.
But Mr. Deichmann said advanced geothermal energy might still work in less populated areas, depending on the precise design and other factors.
In addition to a $6 million grant from the Energy Department, AltaRock had attracted some $30 million in venture capital from high-profile investors like Google, Khosla Ventures and Kleiner Perkins Caufield & Byers.Some of these issues come with any new technology, but if this kind of process for tapping geothermal power results in frequent earthquakes, the likelihood that it will gain any kind of adoption is remote.
“Some of these startup companies got out in front and convinced some venture capitalists that they were very close to commercial deployment,” said Daniel P. Schrag, a professor of geology and director of the Center for the Environment at Harvard University.
Geothermal enthusiasts asserted that drilling miles into hard rock, as required by the technique, could be done quickly and economically with small improvements in existing methods, Professor Schrag said. “What we’ve discovered is that it’s harder to make those improvements than some people believed,” he added.
In fact, AltaRock immediately ran into snags with its drilling, repeatedly snapping off bits in shallow formations called caprock. The project’s safety was also under review at the Energy Department after federal officials said the company had not been entirely forthcoming about the earthquakes produced in Basel in making the case for the Geysers project.
The results of that review have not yet been announced, but the type of geothermal energy explored in Basel and at the Geysers requires fracturing the bedrock then circulating water through the cracks to produce steam. By its nature, fracturing creates earthquakes, though most of them are small.
On Friday, the Energy Department, which has put some $440 million into its geothermal program this year alone, said that despite the latest developments, it remained confident of the technology’s long-term prospects. Many geothermal methods do not require drilling so deep or fracturing bedrock.
“The Department of Energy believes that geothermal energy holds enormous potential to heat our homes and power our economy while decreasing our carbon pollution,” said Stephanie Mueller, a spokeswoman.
AltaRock has also received some $25 million in federal money for a project in Oregon, and some scientists speculated on Friday that after the spate of problems at the Geysers, the company wanted to focus on a new site.
But the company, whose project at the Geysers was located on land leased from the federal government by the Northern California Power Agency, has held information about its project tightly. Not even the power agency has been informed of AltaRock’s ultimate intentions at the site, said Murray Grande, who is in charge of geothermal facilities for the agency.
“They just probably gave up, but we don’t know,” Mr. Grande said. “We have nothing official from them at all.”