Could earthquakes help slake humanity’s thirst for for free energy? “Conceivable” but “utterly impractical,” five top U.S. earthquake experts told Discovery News.
It's not hard for an expert to imagine how one might convert earthquake motion into electricity. Ross Stein of the U.S. Geological Survey in Menlo Park, Calif., offered these examples:
You could sew up fault zones with lines that are wrapped around turbines like the pull-starter on a lawn mower or outboard motor. When the quake eventually struck, the lines would accelerate the turbines, briefly generating electricity. You could make a reservoir on the up-thrown block of a thrust fault. When the quake uplifts the block, you could let water flow through turbines to the down-dropped side, generating electricity. Many earthquakes increase groundwater flow and create geysers at the surface; you could use this water flow to turn turbines. You could install a turbine system on a breakwater in a tsunami-prone area, and the water of the tsunami could be forced to turn turbines. There is much more energy to be gained in this system, and there are even experimental energy systems in place designed to harness tidal energy.
But all of these ideas have problems, Stein points out, and the power source is utterly unpredictable.
"Only the largest earthquakes that have a significant amount of energy — and most of the largest events are beneath the oceans,” explained Richard M. Allen, director of the Berkeley Seismological Laboratory and an innovator behind California’s early warning system.
So, you have to wait 100 years, or even 200 or 300 years, for a big earthquake, and you never know where the next one is going to strike. “You would need to deploy it in all earthquake-prone regions, in order to capture the big earthquakes,” Allen says.
Next problem: Big earthquakes produce a huge amount of energy, so how would you store it? James Dieterich of the University of California, Riverside mused on this point. His colleague, David Oglesby, also at Riverside, followed with a related concern: Would you really want to deal with storing a huge power surge at the same moment that seismic shaking may be ripping the power grid apart?
Yet another issue is that the majority of the energy produced in an earthquake is released as heat due to the sliding of the fault against friction. “That means that the seismic waves that cause the ground to shake really aren't carrying all that much of the energy of the earthquake (a good thing, too!)," Oglesby says.
He posed the possibility of harvesting that heat energy but advised against it. "We could inject fluid into the fault zone and use it like a geothermal source, but pumping fluids down to a fault zone sounds like a good recipe to generate another (potentially damaging) earthquake," Oglesby warned.
The USGS’s Malcolm Johnston, also based in Menlo Park, put earthquakes far down on the list of the most available free energy sources:
“The most available free energy source is solar, followed far behind by wind energy and ocean wave energy. Harnessing plate motion is further behind again and harnessing earthquakes (you could do it practically, reliably and are willing to wait 300 years before you next turn your lights on), behind still further.”
Johnston’s bottom line: "If you want a free, sustainable, non-polluting energy source, go solar.”
Ocean energy distribution forecast map for the 2011 Sendai earthquake. (NOAA)