Taken from: Earthlinked - About Geothermal Heat Pumps

Why Use Geothermal?

A Geothermal (sometimes referred to as Direct Exchange or DX) heat pump system is not only something that makes you feel comfortable, it is a technology that you can feel comfortable about. Because it is lowest in greenhouse emissions, geothermal is the most environmentally responsible heating and cooling alternative available today, according to the Environmental Protection Agency.

Geothermal systems are highly energy-efficient since they only require a relatively small amount of electricity to harness the renewable energy in the earth. These units typically deliver much more energy than they consume, so you save on your monthly energy bills when compared to other types of heating and cooling systems.

By focusing attention on advanced product design, solid construction and installation flexibility, geothermal heat pumps are capable of fully utilizing the natural heat storage ability of the earth as a primary source for heating and cooling your home.

How It Works

No matter where you live, the underground temperature remains relatively constant all year, even though outdoor temperatures may vary widely. Geothermal systems utilize this stable resource as a renewable energy source for your home.

Every geothermal system has three major subsystems or parts: 

• An earth loop for transferring heat in the earth
• A heat pump compressor unit to concentrate and move the heat
• An indoor heat distribution system.

(A water-based geothermal heat pump also has a water pump to move water through its water loop in the ground and a water-to-refrigerant heat exchanger.)

In the Winter heating mode, heat is extracted from the earth by using that heat to evaporate the refrigerant (any temperature above -40°F is sufficient) which then passes through the compressor where its pressure and temperature are increased. The hot refrigerant then gives up its heat by heating cool air that passes through the fan coil in the air handler (or by heating the water that is flowing through a radiant hydronic system). Having given up its heat, the refrigerant condenses into a liquid and returns to the earth loop to take on more heat.

In the Summer cooling mode, the process is reversed. The liquid refrigerant passing through the fan coil in the air handler (like the coils in an air conditioner) is evaporated and passes through the compressor where its heat is concentrated and increased. The hot refrigerant vapor then gives up its heat as it circulates in the earth loop, condenses into a liquid, then returns to the building to take on more heat.

(A water-based geothermal heat pump relies upon a water loop to extract heat from the earth and transport it to a heat exchanger adjacent to the heat pump, where the heat is transferred into the heat pump system, and the cycle is reversed in the summer.)

An Investment in Savings

A typical homeowner can save in the range of $600 to $1,200 annually (actual savings vary depending on usage, weather and local utility rates) with the installation of a geothermal system. How? The use of geothermal loops allow geothermal units to use only a relatively small amount of electricity. The unit merely transfers heat to and from the earth, rather than creating it from fossil sources like conventional systems. With geothermal you will enjoy savings up to 60% over conventional systems, and a short investment payback.

Plus, governments and utilities often offer tax credits and rebates for the installation of geothermal heat pumps.

Click here to find out more about Canadian Tax Rebates for energy efficient systems.