In Search of Cleaner Fuel

Peter Malin’s Seismology Group Uses Earthquake Technology to Explore Sources of Geothermal Energy

by Monte Basgall

“It’s the public’s perception of earthquakes that really shuts down this kind of project in populated regions,” lamented Nicholas School graduate student Dan Kahn. “It is a good idea, Basel’s a great place for it, and the public might start out saying ‘We’re fine with earthquakes.’ Nevertheless, as soon as they feel something, all of a sudden it’s ‘We didn't sign on for this!’”

Kahn, who recently returned to Duke from Basel, Switzerland, had participated in the city’s attempt to tap a 5-kilometerdeep natural hot zone. Plans call for using pumped-in water, heated to 200 degrees centigrade in the underground fracture system, to drive a pollution-free geothermal power station on the surface.

Unfortunately, Basel’s Deep Heat Mining project ground to a halt when efforts to crack the buried hot dry rocks by piping down cold water—a necessary step to initiate the project—set off a magnitude 3.4 earthquake on Dec. 7.

Basel is one of four worldwide ventures where researchers from the Nicholas School’s Earth and Ocean Sciences (EOS) Division’s seismology group are helping explore potential sources of geothermal energy, an energy source that emits no greenhouse gases and offers a clean substitute for petroleum, gas or coal.

The seismology group has developed a special expertise in detecting and using “micro”earthquakes to assess underground structural features at places like California’s San Andreas Fault. It is now using those skills to help scout potential sources of hot underground water for environmentally friendly energy production in response to the needs of geothermal energy prospectors.

A new study, headed by researchers at the Massachusetts Institute of Technology, estimates that tapping stored heat within Earth’s crust could satisfy a noticeable fraction of the United States’ future energy needs at competitive prices without producing waste gases that induce global warming.

In Basel, the Swiss city’s citizens had been warned that earth tremors were an unavoidable byproduct of fragmenting the rock to allow water flow, but the quake so jarred them that authorities suspended the project and announced they would undertake a risk analysis, with a possible delay of up to four years.

Repeated cracking is necessary to create an underground network of fractures large enough to heat the injected water to supply the electric power plant’s turbines. The EOS group’s role was to help trace out the cracks by monitoring the seismic noise they produced.

“The project just needs another week to finish optimally cracking the rock,” said Kahn. “Then earthquakes won’t be felt anymore. But one has to get through this few-week period first.

“The clean energy would really be good for the community. And if they got the geothermal power plant up and running, similar installations could be put in other cities along the Rhine.”

page 1 | 2 | 3 | 4