Geothermal Biomass | Hydro | Hydrogen | Wind | Photovoltaics | Solar Heat | Passive Solar | Geothermal | Transportation The word geothermal literally means “earth heat.” We can capture the heat that is stored in the earth and use it to heat our buildings. The top 500 feet of the earth stores heat from solar radiation. Although the top 30 feet of the earth changes temperature with the seasons, below 30 feet, the ground stays pretty stable at the average yearly temperature of the air. For example, in Maine, the ground stays about 50 degrees Fahrenheit. As the earth absorbs the heat from the sun, that heat is transmitted downward to a depth of about 500 feet. Below this depth, the earth gets even hotter, but that heat is as a result of radioactive decay in the mantle and core of the planet. In Maine, there are no places where this deep heat comes to the surface through springs or vents. This type of geothermal activity and the heat that goes with it is much more common in the mountains of the western United States and other places with active tectonic boundaries. Many people in Maine can access geothermal heat through their wells. If a building has a well, the temperature in that well is about 50 degrees F all the time. This heat can be pumped up from the well, and concentrated to heat buildings. This concentration uses a heat pump, similar to the heat pump that keeps a refrigerator cold. In the case of a refrigerator, the heat pump works by pumping heat out of the fridge to the coils on the back or underneath. In a geothermal heat pump, the heat from the well water is taken and passed onto other water, reaching temperatures of up to 120 degrees. This water is them pumped around to heat the building. In the summer, the process can be reversed to cool spaces by taking the heat out and depositing it in water which goes back to the well. Additionally, the excess heat from the pump can be captured to heat water for domestic use. This actually improves the efficiency of the heat pump. Geothermal heating systems are a great way to heat our buildings and water in winter and cool them in summer. However, this technology, like all renewable energy sources, has its limitations. The only greenhouse gases associated with this heating system is the electricity needed to run the pumps. This problem could be solved by using another renewable source to generate this electricity. Geothermal heating systems are highly cost effective, if there is already a suitable well on site, they can pay for themselves in two to five years. Projects for Students Web Site Description Geothermal Education Geothermal Education Office online activities.   More Information Web Site Description Geothermal Information Geothermal information geared toward kids. Water Energy Distributers Local Maine business with great info specific to Maine about geothermal heating, including how it works, and why it's a great option for Maine. Geothermal Heat Pumps National Renewable Energy Laboratory on Geothermal Heat Pumps.   Resources for Teachers Web Site Description Online Activities Geothermal Education Office online activities. Chewonki Lessons Bring your class to Chewonki to learn about the alternative energy sources we use everyday. We can also come to your school to teach about Global Climate Change.

The Renewable Energy Poster is the latest in a series of educational materials called Pathways to a Sustainable Future created by the Chewonki Foundation.