How geothermal works:

Heating Cycle
The heating process involves the extraction of heat energy from the

ground, and moving it into the building. Transferring the heat from the

earth to the building involves a cycle of evaporation, compression,

condensation and expansion. A refrigerant is used as the heat transfer

medium. The heating cycle starts as cold, liquid refrigerant passes

through a water-to-refrigerant heat exchanger and absorbs heat from the

low temperature source (earth loop fluid).
 

The refrigerant evaporates into a gas as heat is absorbed. The gaseous

refrigerant passes through a compressor where the refrigerant is

pressurized, raising its temperature to over 180 degrees F. The hot gas

then circulates through a refrigerant-to-air heat exchanger where heat is

removed as the cooler return air passes over it.

Now heated, this warm air is delivered into the building by way of the

blower and the duct system. Upon releasing its heat energy into the

air, the refrigerant returns to the water-to-refrigerant heat exchanger where

the process is repeated continuously during the heating process. A by-

product of the heating function is the production of hot water that is

delivered to the water heater by way of a small pump.

 

Cooling Cycle
The cooling process involves the extraction of heat energy from the

air in the building, and moving it into the earth. Transferring the heat

from the air in the building to the earth involves a cycle of expansion,

condensation, compression, condensation and evaporation. A refrigerant

is used as the heat transfer medium.

The cooling cycle starts as the compressor delivers refrigerant to the

water-to-refrigerant heat exchanger. Heat from the refrigerant is absorbed

by (rejected into) the low temperature source (earth loop fluid) resulting

in the refrigerant turning cold. The cold refrigerant passes through a

refrigerant-to-air heat exchanger.

As warm, humid air from the return air duct system is passed over the

cold air coil, the air is cooled and dehumidified the returned into the

building, cooling the space. The heat from the warm air that returns to the

unit is absorbed by the cold refrigerant, turning the refrigerant into a hot

gas. The hot refrigerant is returned to the compressor where the process

is repeated continuously during the cooling process.

A portion of the heat returning to the compressor (from the hot return

air) is diverted to another refrigerant circuit that generates hot water and

delivers it to the domestic water heater by way of a small pump.

Adapted from  WaterFurnace.com

 

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