Talking About Green

Nearly all modern HVAC (Heating, Ventilation and Air Conditioning) systems incorporate some type of heat pump into one or more of their systems. A heat pump is simply a device that moves, or “pumps”, heat from one location to another. Air conditioners pump heat out of a building to cool it, and furnaces typically pump heat from a burning fuel supply or electric heating element into a building in order to warm it.

Most modern heating and air conditioning systems use large amounts of energy to create a temperature difference across which heat can be pumped. An air conditioner concentrates indoor heat into a refrigerant (which is simply a fluid that can quickly absorb or release large amounts of heat) via a radiator, and then releases it outdoors. This requires compression of the refrigerant, which requires a fairly large amount of power, especially since air conditioning is used on hot days, when an air conditioner must work hard to pump more heat into an already hot outside environment. However, if that environment was already cooler than the inside temperature of the building, cooling would be a simple matter of letting the refrigerant fluid get warm by absorbing building heat, and then moving it to the cool environment and letting the heat diffuse out of it. In fact, this would be so efficient that an environmentally-unfriendly refrigerant wouldn’t even be necessary. Water or antifreeze could be used.

This exact type of environment can be found underground. The Earth’s surface experiences large seasonal temperature swings in most areas, but it remains at a nearly constant temperature year round only a few feet underground.

Ground source heat pumps (or geothermal heat pumps) take advantage of this constant temperature by circulating water or antifreeze through a loop that connects to two heat exchangers, one above the ground in a building and the other below ground. During the summer, liquid is heated as it passes through a radiator (the heat exchanger) at the surface. It is pumped into the ground and releases its heat into the soil. The cooler liquid comes back to the surface, passes through a radiator and absorbs heat from the air. This warms the liquid again and cools the air, which is blown through the duct work by a fan.

The opposite of this process occurs during the winter. Liquid is chilled as it passes through the above-ground radiator. It is pumped into the warm soil, where it picks up heat and then circulates back to the surface. A fan blows cold air through the radiator, warming the air and cooling the fluid again.

This process does not burn fuel to create heat and it does not expend energy compressing a refrigerant. The only energy expended is the electricity needed to drive the pump that circulates the water, and this is usually minimal compared to the cost of operating a typical HVAC system.

Geothermal International are specialists in geothermal energy, offering support and products for a wide range of residential and commercial projects.