One of the cleanest energy sources known is geothermal energy, tapping into underground steam to produce electricity.  The latest geothermal technology, Enhanced Geothermal Systems (EGS) or Hot Dry Rock technology has shown some disturbing safety risks.  In Switzerland and the United States, tapping into geothermal energy using Enhanced Geothermal Systems has resulted in earthquakes.

The New York Times reported that AltaRock Energy will be using the EGS technology.  This is the same technology that was used in Switzerland when it triggered an earthquake and the project was shut down.

EGS requires drilling down deep into hot rock that doesn’t contain any water.  Once a well is dug, pressurized water is forced down into the rock creating fissures and fractures that allow water to be turned into steam.  The steam is tapped into using a different well and that steam is used to generate power.

The fissures and fractures caused by the pumping of pressurized water into the hot rock can easily develop into earthquakes.  This is what happened in Switzerland and what is happening in several parts of California where existing geothermal plants are located.  Although the Swiss project was quickly shut down, minor earthquakes continued for months after.

Anderson Springs is a town located close to The Geysers, an existing geothermal power plant using shallower wells than AltaRock Energy is proposing to drill.  Over a 58 month period, Anderson Springs experienced 402 earthquakes.  The town posts a Pre-Application Form for Projects/Repairs/Small Claims on its Web site for such damage as cracked walls due to the earthquakes.

Both the Switzerland geothermal project and AltaRock Energy’s proposed projects require drilling much deeper than The Geysers.  The deeper drilling could mean bigger, more dangerous earthquakes.

AltaRock Energy told The New York Times that the company has has developed new safer methods and chosen its drilling site carefully to avoid the problems experienced in Switzerland.  The company has chosen to build its geothermal wells near Anderson Springs because there are no major faults nearby and the area has experienced only minor earthquakes.  Anderson Springs is skeptical.

Geothermal energy is expected to be a major source of future renewable energy in the United States.  The Department of Energy has released a study of The Future of Geothermal Energy.  The study looked at various methods of tapping into geothermal power including the EGS.  The study is very optimistic about the advances in that technology and sees it as a way of tapping into geothermal energy in all areas of the country.

Is geothermal energy safe?  It depends on who you ask.  The small earth quakes that frequently plague such areas and towns like Anderson Springs, have not been deadly although the quakes do result in ongoing property damage.  The technology used in those areas has required shallower drilling than the proposed project by AltaRock.  Fears are that with deeper drilling, more severe earthquakes will be triggered.

AltaRock Energy says that it has worked out the problems that shut down the Swiss geothermal project and AltaRock’s technology is safe.  We’ll see.

Related:

Entry was posted on Wednesday, June 24th, 2009 at 7:35 pm under Green Technology, Science and technology.

Read more entries by Susan Wilson.
Stumble It!