Closed Loop Systems:
Closed loop systems are another variation of geothermal energy systems. Closed loop systems like the name implies that the system is not open to the environment like open loop system. Many closed loop systems use a refrigerant or antifreeze like propylene glycol and tetrafluoroethane (r-134a). Refrigerants and antifreeze are used in closed loop systems because of there ability to vaporize at relatively low temperatures which the steam can then be used spins turbine or power a heating and air conditioning system.
Basic schematic of a closed loop system. [5]
There are also several configurations when it comes to ochestrating a closed loop system and they depend on the land situation. There are three main types of configurations, vertical, horizontal, or pond (coiled).
Vertical Closed Loop Systems:
Vertical closed loop systems are ideal if the amount of land available is small because the pipes are placed vertically in the ground. [6]
Horizontal Closed Loop Systems:
Horizontal closed loop systems are ideal if the property they are supplying energy to has a significant amount of land as they are shallower in depth than vertical systems. [7]
Pond Closed Loop Systems:
Pond closed loop systems are a great alternative to the previous setups if there is a body of water present near the structure the system is benefiting. [8]