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How secure are geothermal power plants? Take a look at these eco-friendly science images!
iStockphoto/ThinkstockMain Points to Remember
- Geothermal power plants tap into the Earth's internal heat to generate electricity, providing a generally safe and eco-friendly energy option.
- The primary risks associated with geothermal energy involve the potential release of harmful gases and seismic activity, though these are usually far less significant than those posed by other energy sources.
- Effective site selection, ongoing monitoring, and proper regulation ensure that geothermal power plants are safe and environmentally sustainable.
Despite ongoing concerns about the oil supply, you might be surprised to learn that the answer to reducing our reliance on fossil fuels lies beneath our feet. In regions such as California, Nevada, Idaho, Alaska, and Hawaii, geothermal energy—hot rocks, steam, and superheated water—can be harnessed to generate power. Advocates of geothermal technology, like Google, argue that this carbon-free, limitless energy resource could supply 15 percent of the U.S. electricity demand by 2030.
Using Steam Effectively
The simplest form of a geothermal power plant is a dry steam plant, where a well is drilled into rock to reach a steam reservoir. The steam escapes under high pressure, which is used to spin a turbine and produce electricity.
Since steam reservoirs are less common than hot water and hot rock deposits, the most efficient geothermal technology is the binary-cycle power plant. This system circulates hot water from a deep well through a heat exchanger, where it transfers heat to a secondary liquid with a lower boiling point. As the secondary liquid vaporizes, the steam produced is captured to drive turbines.
The Risk of Deep Drilling
Unfortunately, geothermal power plants can have an unexpected and potentially hazardous side effect: earthquakes. Drilling deep into the Earth and extracting materials—be it steam, water, or hot rock—releases pressure, causing the ground above to shift. What's more, the richest geothermal energy sources are often located in seismically active areas. Some experts believe that drilling near fault lines could even trigger earthquakes.
In 2006, a geothermal power plant in Basel, Switzerland allegedly triggered a series of minor tremors along a fault line that was responsible for a devastating earthquake back in 1356. In August 2009, similar reports of small earthquakes near a geothermal facility in Germany led to government safety assessments and raised concerns in the local community. Additionally, in California, a geothermal test site called The Geysers has been associated with an unusual cluster of small seismic events near its location.
Up until now, none of these tremors have exceeded a magnitude of 3; most go unnoticed by the general public. However, if geothermal energy is to become the game-changer that alternative energy advocates envision, it will need to address and overcome its unsettling link to seismic activity.
