| Geothermal Heat
The idea behind the geothermal heat pump is similar to that of a central HVAC system; both systems use an outside unit, called a condenser, and an inside unit, called an evaporator. However, while the central HVAC system uses compressed refrigerant to remove heat from the system, a geothermal heat pump uses the stable, consistent temperature of the earth to provide winter heating and potentially summer cooling. Studies have shown that geothermal heat pump systems are capable of reducing monthly heating and cooling bills by as much as 40 percent.
Geothermal heat pumps use a series of piping, installed below the earth's surface or submersed in a pond or lake, to form a loop through which water or another environmentally safe fluid is pumped. During the winter months, the fluid carries heat into the house, where a compressor and heat exchanger concentrate the earth's energy before releasing it into the home at a higher temperature. The heat is then distributed throughout the house. During the summer months, the fluid carries heat from the home, releasing it back into the earth or the water body in which it is submerged.
The length of the piping loop depends on several factors: the heating and cooling requirements of the home, climate and soil conditions, landscaping, and type of loop used. Horizontal ground closed loop systems are typically the most cost effective, assuming the lot size is sufficient. In a horizontal ground closed loop system, a series of parallel plastic pipe is buried three to six feet below the earth's surface, with a typical length of 400 to 600 feet per ton of heating and cooling. Piping can also be coiled in a slinky shape to increase the amount of piping that can be located in a given space. Fluid is then used to carry heat to and from the indoor exchange unit.
A vertical ground closed loop system is a more practical option for small yards or when you want to disrupt the landscape as little as possible. In this type of system, vertical holes 150 to 450 foot deep are drilled into the earth, and a single loop with a U-bend at the bottom is installed. Because the temperature of the earth is more stable as the depth increases, a vertical ground loop system typically requires less piping.
The centre of the earth is composed of molten rock with temperatures of between four and six thousand degrees Celsius. Hot substances transfer thermal energy to colder substances, so heat travels from the centre of the earth where it is hottest, to its surface.
The groundwater can be accessed by drilling a well, and this thermal energy can then be circulated through your heating solution. Where ground water is available it is can be used all year round as it generally has a temperature between 7-12°C in Ireland.
The main variants in common use are:
- Air to Air
- Water to Water
- Water to Air
- Air to Water
- Ground to Water
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Ground to Air
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