Ground source geothermal heat pump systems can run at efficiencies of up to 400%. This is achieved by using 75% of the energy required to heat or cool from the Earth itself and 25% from electricity to run the pumps and heat pump compressor.
The heat pump cycle transforms heat from a low temperature level heat into a high temperature level which can be used for heating purposes. The refrigerant evaporates at a very low temperature and takes a substantial amount of energy from the ambient heat exchange medium when changing from a liquid to a gas phase. In this case the medium is water that is piped into the earth using boreholes or laid into trenches. Pond, lake or well water can also be used either directly or with a heat exchanger.
The compressor then compresses this refrigerant gas and thus brings it to a high temperature level. The hot gas is then condensed in the condenser where it transforms into a liquid state and gives heat to the heating system. Then the refrigerant is passed through an expansion valve and expanded so the circular process can continue.
In Geothermal Cooling, the heat pump cycle is reversed and the hot refrigerant gas releases heat into the water and transports it to the ground, which is cooler. In this way the geoexchange medium, water, transports the heat from the hydronic heat transfer water or air coil into the earth, thereby cooling.
After the refrigerant has released its energy into the water it is again a cold liquid and is circulated through a heat exchanger where air is blown across a coil or hydronic water is cooled to be piped through the building and distributed with hydronic air handlers or radiant cooling ceiling panels.
Domestic hot water can be heated with a desuperheater that circulates domestic water through a heat exchanger and picks up heat from the superheated refrigerant gas in the heat pump cycle. This increases the efficiency of the heat pump operation and heats water as a no cost byproduct of heating and cooling operation.
Ground source geothermal heat pumps are the future of heating and cooling generation. With millions of applications in operation around the world and in the US the reliability and efficiency is well proven.
Ground source geothermal is the base of a highly efficient and carbon neutral building. With solar thermal domestic hot water, photovoltaic electric generation and a geothermal heating and cooling system net zero energy buildings are currently operating. Adroit Solar has as one of its projects an operating 8,000 square foot luxury residence in Rancho Sante Fe that is a net zero energy building.