The term Geothermal Energy is derived from the Greek words "geo", meaning earth and "thermal", meaning heat.  Not far below the surface of the earth, the temperature is a stable 45-60 degrees.  With Geothermal heating systems we are able take advantage of this heat source by sending water underground to be heated and then returned to our homes.

The concept and design of a residential geothermal system is quite simple.  It consists of a heat-transfer unit (or geothermal heat pump) located inside the home and is connected to a series of pipes that are located in the ground.  A water/antifreeze mixture is continuously circulated back and forth between the heat pump and the pipes.  As the liquid travels through the system underground, it gains heat.  The hot water then returns to the home and is directed to radiators, forced air units, under-floor units, etc. The ground pipes are placed into the earth in one of several ways.

Horizontal Closed-Loop System
At a depth of about 3-6 feet, a continuous loop pipe is buried in trenches or in a pit. This system requires plenty of land which you feel comfortable excavating.

Horizontal "Slinky" Closed-Loop System
This system requires less excavation and works similar to the horizontal closed-loop method.  In this scenario however, more pipe is needed as the pipe is formed into a slinky-pattern; overlapping loop-over-loop.

Vertical Closed-Loop System
A narrow continuous-loop pipe with a "u" bend at the bottom is placed in a vertical hole and extends down to about 150-450 feet.  Much less space is needed and less pipe is required than the horizontal systems but this option is more expensive.

Pond Closed-Loop System
A pond system is the horizontal closed-loop system that we saw above but it is placed in water at a depth of about 6 - 8 feet; typically a pond.

Vertical Open-Loop System
This open-loop system is quite similar to the vertical closed-loop system.  However, there are two boreholes.  Ground water is pumped up through one of the pipes, moved through the heat pump, and then sent back down the other hole.  If conditions allow, the exiting water can be pumped away from the home into an open field or a water source such as a pond, river, or stream.