Written by Brad Crawford
Geothermal heat pumps use the constant temperature of the ground to exchange heat between the inside and outside of your house. It pulls heat from the ground to heat your home in the winter, and pulls heat from your house and leaves it in the ground in summer.
A geothermal system can reach efficiencies of up to 600 percent. Compare that to even the most energy efficient furnace, which can’t convert all of its energy into heat for your home. Air source heat pumps typically achieve heating efficiencies of up to 250 percent, though that’s still far less than a geothermal heat pump.
The primary component of a geothermal heat pump system is the ground loop, which is either open or closed. In a closed loop system, the pipe typically runs horizontally, between 4 and 6 feet deep, or vertically between 100 and 400 feet. In North Texas the average depth required for a good heat transfer is 250 feet per well loop. The pipes are filled with an environmentally safe antifreeze and water solution that acts as a heat exchanger. In the less-common open loop system, surface water is used as a heat transfer medium.
When considering your options for geothermal installations, it’s important to factor in your location. Your property type will determine which type of ground loop you’ll use. Your geothermal HVAC contractor will look at the geology, hydrology and landscape to decide.
The composition of your soil and rock affects the rate at which heat is transferred. For example, soil with good heat transfer properties will require less piping. Areas with shallow soil or lots of rock may require vertical ground loops.
The availability of ground or surface water can help determine what type of ground loop to use. Certain bodies of surface water can be used as a source of water for an open-loop system, or in a closed-loop system as the location for coils of piping. Ground water can also be used as a water source for open-loop systems, provided the water quality is suitable.