Artificial geothermal and earthquakes

2009-07-01

in Science, The environment

Rusty fire hydrant

Apparently, artificial ‘enhanced’ geothermal sites may cause earthquakes. The concept (mentioned here before) is to drill shafts down into hot rock formations, pump in cold water, and generate steam to drive turbines. It would considerably increase the number of regions where geothermal power could be used.

According to Swiss government seismologists and officials on the Basel project, an artificial geothermal project caused an earthquake in Basel in 2006 and was subsequently shut down. Even after the shutdown, thousands of smaller earthquakes occurred in the following years. Now, there are concerns about a project that AltaRock Energy wants to undertake in California. Google’s philanthropic arm is investing $6.25 million in the project. The proposed site already experiences as many as a thousand small earthquakes per year. This video has some further details.

Obviously, the earthquake risk needs to be assessed and managed. It may be that not as many sites are suitable for enhanced geothermal as previously assumed. Perhaps such projects will only prove viable in sparsely populated regions. In any case, it is an unfortunate blow to an otherwise promising looking type of renewable generation.

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{ 5 comments… read them below or add one }

R.K. July 1, 2009 at 12:38 pm

Big dams also cause earthquakes.

So can extracting oil and mining for coal.

There is a good chance CCS will cause some earthquakes, too.

prometheuspan July 1, 2009 at 1:39 pm

http://issues.ni4d.us/index.php?title=Geothermal_Power_Responsible_Versus_Irresponsible_Technologies

There are several different ways to go about obtaining geothermal energy or drilling Geothermal wells. The only means which I personally advocate is exclusive to other technologies and is in some senses probably somewhat more expensive over the short term. However, the alternatives will prove to be more expensive over the long term, and to have assorted negative consequences. The only good way to do geothermal power is to drill a conventional well using conventional standard drilling technologies, and then to build closed circuit double loop systems. What this means is that firstly, an actual linear well is drilled straight down into the earth, secondly, that the water which is heated to power the system never leaves the piping which contains it, and thirdly, that water is circulated down on one circuit or loop and rises as steam on a second circuit or loop.

The Alternative being now explored is to use water as an explosive, and to drill non linear wells by pumping water into rock. This creates many small fractures or fissures in the rock, rather than a straight down conventional well. It also can cause earthquakes,is prone to the problem of erosion, and is likely to create a geothermal system which cools very quickly, especially when compared to closed circuit double loop. Claims made about such systems that they are closed systems are obviously false, if the water leaves the tubes then there is obviously potential for that water to leave the geothermal system. Another issue to consider is that a closed circuit double loop system never loses water and never loses pressurization. The systems which they are now creating are highly entropic, and while they may for the time being demonstrate properties of a closed system, they are certainly not truly closed.

. October 26, 2010 at 10:44 am

While drilling wells in Yellowstone might not be a great idea, geothermal energy in general is very promising. According to recent life-cycle analyses by Argonne National Laboratory, geothermal power plants emit between 18.7 grams to 103 grams of CO2-equivalent per kilowatt-hour—polite little hiccups compared with the 1,234.9 g/kWh belched out by coal or the 487 g/kWh by natural gas. (Those figures include building and running the power plants as well as extracting the fuel.) Unlike conventional coal-fired plants, geothermal plants emit very little sulfur dioxide and no nitrogen oxides, which are the precursors of acid rain. And unlike wind or solar power installations, geothermal power doesn’t fluctuate with the weather. Last year, the United States’ 77 geothermal power plants produced 15.2 billion kilowatt-hours of electricity, or about 0.4 percent of the U.S. total—more than any other nation in the world. (Wind machines generated 70.8 billion kWh of electricity, and solar 0.8 billion kWh.)

But as with any big industrial project, geothermal energy production also carries some environmental risks. The biggest issues revolve around water. Brackish waters drawn from deep underground are sometimes laced with toxic substances like mercury, so power producers have to be very careful with how they store and dispose it. To cool their working fluid, some geothermal power plants withdraw large amounts of surface water. In areas where fresh water is scarce, these plants may compete with farms and homes that need water for irrigation, bathing, and the like—but that’s a problem for other kinds of power plants, as well.

. October 26, 2010 at 10:48 am

The potential for geothermal projects to cause earthquakes has received a lot of attention in recent years. Most of the concern has been focused on projects known as enhanced geothermal systems, or EGS. There are plenty of underground zones that get scorching hot but remain dry, because the rock there is so dense. Without water to carry that thermal energy to the Earth’s surface, you can’t generate electricity. (Not yet, at least.) In EGS applications, high-pressure water is injected into those impermeable, rocky areas to create a network of small fractures. Pumping surface water into the now-porous rock creates a brand-new hydrothermal reservoir. That fracturing process produces microearthquakes—small tremors that can be detected with a seismometer but generally aren’t felt at the Earth’s surface. To avoid creating more damaging earthquakes, EGS projects must steer clear of active fault lines and monitor seismic activity very closely. In the United States, EGS projects are still in the research and development phase, with none yet online.

. September 13, 2014 at 1:01 am

Geothermal is a minnow among power sources. America has the world’s highest installed capacity of geothermal generating plants—3.4 gigawatts’ worth at last count (see first chart)—but they generate only 0.4% of its electricity (see second chart). New “enhanced geothermal systems” (EGS), however, look set to make geothermal a bigger contributor—and potentially as controversial as shale.

The industry may dislike the comparison, but EGS is geothermal fracking. Millions of gallons of water and chemicals are injected into mostly vertical wells at relatively high pressure, and the combination of cold-meets-hot, pressure and chemistry shears the deep, hot rock. This creates new “fracture networks” through which water can be pumped, heated and sent back to the surface to generate power. Conventional geothermal wells cost at least $5m to develop, and about half fail. The new technique can reduce the failure rate and extend the size and life of existing geothermal fields. In time, think EGS fans, it will allow geothermal fields to be established wherever there is suitable hot rock.

Mr Hollett calculates that EGS adds capacity to existing fields at a cost of 2-5 cents per kilowatt-hour; for low-cost natural gas the equivalent is 6-7 cents. The department reckons that with EGS techniques, geothermal could eventually meet 10% of America’s electricity needs.

The sticking-point, says Susan Petty, AltaRock’s founder, is commercialisation. Geothermal is a steady source of energy (unlike windpower), has very high capacity-utilisation rates, zero fuel costs and near-zero greenhouse-gas emissions. The trouble is that successful existing geothermal plants do not need EGS, and for many failed wells it is uneconomic to introduce it. So with the help of an as-yet unnamed partner, AltaRock plans to buy up existing fields that it thinks it could make profitable using its version of EGS. That way it will avoid the costs of new infrastructure while demonstrating its technology’s viability.

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