What are the different types of geothermal wells?

Geothermal wells also known as geo exchange systems have 2 basic designs. They are:

• Open looped system: in an open looped system, ground water is pumped from water well into a heat exchanger located in a surface dwelling. The water drawn from the earth is then pumped back into the aquifer through a different well, or in some cases the same well. Alternatively, the ground water could be discharged to a surface of water body. In the heating mode, cooler water is returned to the earth, while in the cooling mode, warmer water is returned.
• Closed loop system: In a closed loop system, an opening (either borehole or trench) is made in the earth. A series of pipes are installed into the opening and connected to a heat exchange system in the dwelling. The pipes form a “closed loop”, and are filled with a heat transfer fluid. The fluid is circulated through the piping from the opening into the heat exchanger and back. The system functions in the same manner as the open looped system, except there is no pumping of ground water.