Geothermal energy utilized by ground-source heat pumps doesn’t actually produce heat. Instead, it transfers household heat to or from a consistent heat exchange source, usually the ground right under your feet.
Five feet below the surface here in northern Michigan, the Earth maintains a steady temperature of about 55 degrees all year long. Geothermal systems utilize loops of buried pipe to circulate heat transfer fluid from the heat pump through the ground. During summer, heat extracted from your home is transferred to the cooler Earth. In winter, latent heat is absorbed from the ground, intensified by the heat pump compressor, then transferred back into the home. Effective planning for geothermal depends upon the varying characteristics of each site.
Horizontal geothermal installations incorporate 500-foot closed loops of pipe laid in a horizontal orientation in 250-foot-long trenches. These are the least expensive installations, but require the most land for the loop field. While the size of the loop field depends upon the capacity of heating and cooling for the home, as a rule of thumb a horizontal loop field requires a footprint about three times the size of the house. The best average residential candidate for horizontal installation is a one-acre property free of boulders.
Vertical geothermal installations insert the pipe loops into the ground vertically, in holes at least 150 feet deep. This permits a smaller loop field footprint but necessitates extensive drilling. Though vertical loops can be installed almost anywhere and are suitable for sites with restricted space, land with thick bedrock near the surface may have higher installation costs due to the expense of drilling.
Soil conditions influence the efficiency of heat transfer from the buried loops. Dense soils such as clay transfer heat well. Loam mixtures have intermediate properties while loose, sandy soils are the least efficient and require the largest loop fields. Also, the wetter the soil of any type is from groundwater or other sources, the better it transfers heat.
Team Bob’s Heating Cooling Plumbing started serving Grand Traverse homeowners in 1980. For more advice on planning for geothermal at your residence, give us a call.
Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems). For more information about geothermal systems and other HVAC topics, download our free Home Comfort Resource guide.
|Geothermal image via Shutterstock|