Using the Earth's heat below ground one can access a free battery to heat and cool your home. One can take summer's hot air and cool it and winter's cold air and warm it using geothermal energy exchange. Earth's temperature is a mostly constant temperature about eight to fifteen feet below the soil surface. Temperature changes in the soil occur slowly because gains or losses ten feet below the earth's surface are so slow to react that the season is changing and several months have transpired. In Northern America the temperature will be a constant 45 to 50 degrees F. and in the South the soil temperature ranges from 50 to 70 degrees. By taking advantage of these soil temperature constants one can heat and cool their home for one third less money by using the same technology that refrigerators and air conditioners utilize: a heat exchanger. With buried tubing filled with water and environmentally friendly antifreeze heat can be exchanged in a way that is advantageous based on the season. In the winter the tubing loops absorb heat from underground and warm air is sent throughout the house via the air ducts. When temperatures are hot outside in the summer months the tubing sends heat into the earth and returns colder air back to circulate in the house. The water and antifreeze mixture causes the heat from the tubing to flow to where it is colder. By using a geothermal unit we can compress the air to higher pressure and run it through a second heat exchanger where the heat is sent to the house. When the temperature outside is hot the process is reversed. The three phases where heat is exchanged is underground to water; water to Freon; and finally Freon to air or water. This process is a very good use of resources, some estimate up to 400%.
Authors Rex Ewing and Doug Pratt explain in their "Got Sun? Go Solar" book that, "The ground surrenders four units of heat energy for every one unit of electrical energy you use to extract it." The only external energy needed for Geothermal heating and cooling is the small amount of electricity to operate the heat pump, ground loop pump and distribution fan. Money can be saved on installation if open tubing can be utilized, which depends on your soil type and property location. Tubing can be coiled tightly or installed vertical or horizontal depending on the property's available space. Tubing can be placed under driveways or sidewalks if care is taken to avoid damaging the existing concrete. Depending on your latitude, soil type, and how much land you own one can use a geo-exchange system, which are eligible for a 30% federal tax credit. Geothermal systems range from $3,000 to $5,000 per ton, depending on available ground water and the type of soil you have. A system of this size will heat and cool about seven hundred square feet per ton of capacity.
According the EPA, "Geothermal systems are the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available." Most people report how "unnoticeable" the system is because it is so quiet. One family reported that the only time they realized that the heater or air conditioning was running was when a family member is near a vent when it turns on. The overall energy bill is about two-thirds lower, or $100 on average. This cost savings helps the system to pay for itself in energy savings in as little as six years on average.
Sarah Fallin
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