How Geothermal HVAC Works
A geothermal heating and cooling system (sometimes referred to as geoexchange or ground source heat pump) uses the constant temperature of the earth four to eight feet below ground to provide heating, cooling and hot water for both residential and commercial buildings.
In the winter months, a geothermal system transfers heat from the ground to your home. And during the summer months, the process is reversed as the system moves heat from your home to the earth.
Geothermal systems have three major components:
- A loopfield of polyethylene piping buried underground that's flushed with a heat transfer refrigerant to extract the earth's naturally existing heat.
- A geothermal heat pump
- A distribution system
In heating mode, the water circulating in the earth loop is colder than the surrounding ground. This causes the water to absorb energy, in the form of heat, from the earth. The water carries this energy to the heat exchanger in the pump. In the heat exchanger, refrigerant absorbs the heat energy from the water. The water now leaves the heat exchanger at a colder temperature, and circulates through the earth loop to pick up more energy.
The refrigerant gas, which contains energy gained from the earth loop, travels from the heat exchanger to the compressor. In the compressor, the refrigerant temperature rises to 160°. From the compressor, the superheated refrigerant travels to the air heat exchanger. Here, the heat pump's blower circulates air across the air coil, increasing the temperature of the air, which is blown through ductwork to heat the home. After refrigerant releases its heat energy to the air, it then flows to the earth loop heat exchanger to start the cycle again.
In cooling mode, water that circulates in the earth loop is warmer than the surrounding ground. This causes the water to release energy, in the form of heat, into the earth. The water, now cooler from traveling through the ground now flows to the heat exchanger in the heat pump. In the heat exchanger, hot refrigerant gas from the compressor releases its heat into the water. This causes the water to increase temperature, which it releases to the ground.
The refrigerant, which has released its heat energy and became a cold liquid, now travels to the heat exchanger. Here the heat pump's blower circulates warm, humid air across the cold air coil. The air is then blown through ductwork to cool the home. The refrigerant in the air coil picks up the heat energy from the air, and travels to the compressor. When the refrigerant leaves the compressor, it then flows to the earth loop heat exchanger to start the cycle again.