What to Know About Geothermal Ground Loop Design
Wherever you live, the temperature beneath your home remains constant regardless of the season. This constant temperature is provided by the sun's natural solar energy absorbed by the ground. Geothermal systems use a sealed ground loop filled with circulating water to act as a heat exchanger and utilize this energy to heat and cool your home.
In the winter, the earth is your source of heat.
Water circulating in the ground loop absorbs heat from the earth and carries it to the geothermal heating and cooling system, where it is concentrated and sent as warm, comfortable air.
In the summer, the earth is your source of cooling.
The proper geothermal ground loop design for your home is one that provides a cost effective installation and delivers maximum efficiency. No matter which type of ground loop is installed, homeowners benefit from the most comfortable system available, while saving money on operating costs and helping to save the environment. No matter what temperature is outside, the ground loop system is always taking advantage of the mild ground temperature year-around.
The geothermal system absorbs the heat from the air in your home and transfer it to water circulating in the ground loop where it is absorbed by the earth. This provides cool dehumidified and comfortable air throughout your home.
Geothermal Ground Loop Design and Closed-Loop Systems
Closed loop systems use a continuous loop of special polyethylene plastic pipe to serve as a heat exchanger in the earth. The pipe is connected to the geothermal system and forms a sealed, underground loop through which water is circulated.
These ground loop systems can be installed vertically, horizontally, or in a pond. Each installation has advantages and disadvantages and is dependent on available land space, cost of installation, and performance.
Vertical or drilled closed-loop systems take up the least amount of land or yard space. Since the heat exchange takes place along the vertical drilled (bore) hole walls, only a small 4" hole is required. Typically 150-300 feet per ton of equipment is required. Minimal spacing required between bore holes is 10 feet for residential applications. The hole is sealed with a special grout that ensures maximum contact with the earth for heat exchange. Their compact layout makes a geothermal closed-loop application possible for any home. Loops can even be installed underneath the foundation of the home.
Horizontal or trenched closed-loop systems take up more land area than any other type of ground loop, they are used where space permits. Trenches are normally 4-6 feet in depth and extend 200-350 feet per ton of equipment. Trenches are spaced a minimum of 10 feet apart. For rural installations, horizontal loops can be very cost effective.
Pond closed-loop systems are usually very economical to install. If a 1/2 acre pond or lake of at least 8-10 feet in depth is available, they can utilize the water (rather than soil) for heat transfer. A coil of special polyethylene piping is submerged into the pond, while trenches from the heat pump to the pond are used to connect the system.
Open loop systems use groundwater from a conventional well as a heat source in the winter and a heat sink in the summer. The groundwater is pumped through the heat pump where heat is extracted (winter) or rejected (summer), then the water is disposed of in pond or other suitable manner. Open-loop systems run higher operating costs due to the well pump usage. Typically a well pump is of 1.5 HP to 2 HP, closed-loop systems utilize 1/16 HP pumps to circulate the water through its piping.