A guide to geothermal energy
By Jessica Valatka
Definition of “geothermal”
The word “geothermal” comes from two Greek words: “geo” meaning earth, and “therme” meaning heat. Therefore, geothermal is the heat energy produced within the Earth. Heat is continuously produced by the earth, which makes it a reliable and renewable energy source.
How does geothermal work?
Geothermal energy is harnessed by using either geothermal power plants, or geothermal heat pumps.
-The power plants consist of wells that pump up steam or hot water (which becomes steam due to the change in pressure) from underground reservoirs deep within the Earth (usually about 1-2 miles). This steam is used to spin a turbine that is connected to an energy-producing generator. The steam then enters a cooling tower to become water again, and is pumped back underground.
– The heat pumps pump water or a refrigerant through a loop made of pipe just under the Earth’s surface where the temperature is generally constant (usually 50 to 60 degrees Fahrenheit). If it is a cold season, the water can be warmed by the earth when pumped through the loop, and be used to transfer heat into the building. In a warm season, the water can cool the building, and additional heat can be transferred to the ground.
Sustainability of geothermal power plants
According to the Office of Energy Efficiency and Renewable Energy (energy.gov/eere), “Using geothermal for electricity produces only about one-sixth of the carbon dioxide of a natural gas power plant, and little—if any—nitrous oxide or sulfur dioxide. Binary-cycle geothermal plants, which operate in a closed cycle, release essentially zero emissions.”
Sustainability of geothermal or ground source heat pumps
Implementing geothermal is a great way to repurpose the gas pipes, oil wells, and oil/gas fields that already exist. This includes the underground pipe systems that cities use to distribute fossil fuels.
Geothermal works well as a combination with other renewable energy sources. (The concept of connecting these energy sources is called “energy hybridization”.) Not only is it 24/7 energy production (which is good if the sun isn’t out or the wind isn’t blowing), but it can also act as a battery for extra energy produced.
Did you know?
Salem has a number of large geothermal systems! Plummer Youth Promise just installed one, and Salem State University Library does as well. The library is heated and cooled by a geothermal system of 48 wells drilled 500 feet into the ground below the library quad.
Sources
Jessica Valatka is a member of SAFE’s communications workgroup.