Closed loop vs. open loop systems
With geoexchange, the energy used for heating and cooling can be extracted from the earth by using either a closed loop or open loop system.
In a closed loop system, polyethylene piping is placed in the ground or a body of water to circulate a fluid that is used to transfer energy. This fluid never actually leaves the pipes so only the heat is transferred, not the fluid. The heat extracted is considered low grade heat and isn't substantial enough to meet full heating requirements; therefore, a heat pump is used to upgrade the heat by collecting it from the ground and transferring it to either a hydronic system or forced-air distribution system.
Replenishing the ground heat and providing cooling in the summer months are accomplished by extracting heat from the building space and passing it over colder coils to create an air conditioned environment. The heat removed from the space is then released into the earth through the ground loop.
In an open loop system, water is extracted from nearby water wells or a body of water. The water passes through a heat exchanger that transfers heat to a heat pump and then the water is released back to its source.
Waste heat sources
Geoexchange systems can also incorporate waste heat from a variety of close proximity sources when a larger load is required. Waste heat sources can include refrigeration from ice rinks and grocery stores, waste water effluent and sewer exchange. The heat is recovered by placing a series of pipes around various heat sources and transporting the heat to the buildings that require the energy.
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