The flash tank is at a much lower temperature, causing the fluid to quickly “flash” into steam. The steam produced powers the turbines. The steam is cooled and condenses into water, where it is pumped back into the ground through the injection well.

This second liquid is heated into steam, which powers the turbines that drives a generator. The hot water from the earth is recycled into the earth through the injection well, and the second liquid is recycled through the turbine and back into the heat exchanger where it can be used again.

There are four types of pumps, three closed-loop systems and open-loop systems. Each depends on the type of soil, climate conditions and land available.

In closed loop systems, a water/antifreeze mixture circulates through a loop of pipes underground (or beneath a body of water) and into a building. In the winter (as shown above), the temperatures underground are warmer than the air, so the fluid pumping in is warmer. Then the electric compressors and heat exchangers transfer the heat through ducts in the building.

In the summer, the pipes draw heat away from the building and it is absorbed into the earth or water. Since the fluid is already cool in the summer and warmer than the air in the winter, the heater/AC system doesn’t have to work nearly as hard.

These four types of geothermal heat pumps can be used all over the country due to the constant temperature below the surface, but they vary in efficiency and cost savings.