A geothermal system uses solar energy stored in the ground to heat and cool your home or building. The earth absorbs 47% of the sun’s energy (heat) all year round. Even in the winter, when a blanket of snow covers the ground, the earth’s temperature remains approximately 10°C (50°F) six feet below the surface. This means that you have a steady supply of energy to keep your house or building warm during the winter and cool in the summer.
Geothermal or geo-exchange, heating / cooling is a ground source system that makes use of the largest source of energy available – the ground beneath your feet.
There are 3 main components of a geothermal system: a ground loop, a heat pump and a distribution system.
The Ground Loop
When the building requires heat the geothermal system extracts heat stored in the ground from the sun’s solar energy; when cooling is required the geothermal system extracts heat from the building and stores it in the ground until it’s required for heating. In order to transfer the heat energy between the earth and your house or building, the system requires a heat exchanger, the ground loop.
A series of pipes (ground loop) is buried under your yard, filled with an anti-freeze solution which is circulated through the pipes, making the loop a highly efficient conductor of energy. In the winter, the solution absorbs the heat from the ground and is pumped through the geothermal unit in your home. In the summer, the process is reversed. The fluid in the pipes leaves the home or building in a warm state, and after it circulates through the ground loop, it returns cooler.
The ground loop can take several different configurations: horizontal, vertical, pond/lake or open loop. Each project is evaluated to determine which configuration is best suited for the application.
The Heat pump
The heat pump is the heart to the geothermal system, however the ground loop and distribution system are equally important. When the building requires heating the fluid in the ground loop is circulated through the heat pump, where the heat is extracted from the fluid and transferred into the building. The fluid is then recirculated through the ground loop and returns back to the heat pump, warmed by absorbing the energy stored in the ground. To cool the building the heat pump works in reverse, extracting heat from the building warming the fluid as is passes through the heat pump, and storing the heat energy in the ground.
There are two main configurations of geothermal heat pumps: Water to Water (Hydronic) units, which create hot and chilled water for hydronic heating and chilling (In-Floor, Fan coils, Pools etc.), and Water to Air (Forced Air) units which create hot and chilled air, similar to a conventional furnace and air-conditioning unit.
Technical explanation on how a heat pump is able to extract heat from the ground to heat your home or building: Heat pumps transfer heat by circulating a refrigerant through a cycle of evaporation and condensation. A compressor pumps the refrigerant between two heat exchanger coils. In one coil, the refrigerant is evaporated at low pressure and absorbs heat from its surroundings. The refrigerant is then compressed in route to the other coil, where it condenses at high pressure. At this point, it releases the heat it absorbed earlier in the cycle.