Digging Deep for Geothermal Energy
One way to draw renewable energy from the earth is to literally draw energy from the earth. Geothermal energy takes advantage of the fact that the deeper you go into the earth’s crust, the warmer things get. In geothermal reservoirs up to two miles below ground, the heat of underground water can get up to 700 degrees. Hot water or steam is piped up to the surface to generate electricity (usually by turning turbines), with the cooled water often pumped back down to the source to replenish it.
Many geothermal sites eventually may cool down, especially if extraction systems overburden the site. However, these places can recover their heat if left alone to do so.
Even though non-geothermal energy is required to power the pumps that move the water from one place to another (and depending on the source of this energy, it may emit greenhouse gases), harvesting geothermal energy still uses much less energy than harvesting other energy sources, and they don’t produce greenhouse gases. One drawback, however, is that some water sources contain hydrogen sulfur that can be harmful to workers at geothermal plants; however, systems have been developed to filter that out.
Another drawback to a geothermal reservoir system is that a community needs to be close to the reservoir in order to take advantage of the heat’s energy. Systems that run on shallower systems using heat pump technology can be more flexible.
Geothermal energy is already in use in many parts of the country, including Boise, Idaho, where it was first used in 1893. These older sites tended to rely very much on natural geography to provide easy access to the heat; today, more advanced technology, such as heat pumps, allows much wider application of geothermal energy.