The most common type of geothermal loops used for geothermal installation is a closed loop system. The heat exchanger - a loop of piping filled with fluid - is buried underground.
In a closed loop system, the fluid circulates continuously inside the buried pipe, absorbing heat from the earth during the winter for use inside your home or business. In warmer months, the fluid takes heat from indoors and transfers it back into the earth.
of closed loop systems
Types of closed loop systems
A central closed loop system has all heat pumps in a central room; air or water is ducted and circulated to the heated or cooled rooms. Commercial applications include chiller or rooftop unit retrofits.
Distributed systems use a central water pump and heat pumps serving individual rooms and areas. Types of buildings served included offices and schools, both new construction and retrofits.
Since multiple units are heating and cooling simultaneously, the distributed system can provide heat recovery from core zones that have excess heat to perimeter zones that require heat.
A distributed system also permits location of relatively small individual units in restricted areas, such as historic districts.
Modular systems have dedicated heat pumps, water pumps and loops. This type of system allows for independent individual control, operation and maintenance.
Types of buildings suitable for a modular approach include schools, with modules serving individual classrooms, and other buildings where usage and environment are clearly separated.
A hybrid system uses a cooling tower or other means to reject excess heat not needed for winter heating. The cooling tower reduces the size of the ground heat exchanger and the cost of installation.
Geothermal Loops: Horizontal Loops
If adequate land area without hard rock is available, a horizontal closed loop installation is usually the most economic. Horizontal loops are often used for newly constructed homes and commercial buildings.
A horizontal system uses a number of trenches. The piping can be configured in the trenches in several ways:
Geothermal Loops: Vertical Loops
If the land area available is limited, a vertical closed loop system may be installed for the geothermal piping.
Vertical installations might also be used where the land is too rocky for trenching, for existing buildings, and for large commercial or educational facilities.
To install a vertical loop, a contractor will bore holes into the ground. Long, hairpin-shaped loops of pipe are then inserted. The hole is backfilled, plugged or grouted, and the pipes are connected to headers in a trench leading back to the building.
The drilling depth is determined by the lowest total cost based on the conditions at the job site. A typical borehole depth is 150 to 250 feet.
The objective of a vertical borehole is to install a specific amount of pipe, not to reach a certain depth. If 1,200 feet of pipe are required, three 200-foot boreholes are acceptable and may be more cost-effective.
Drilling boreholes for geothermal loops is much simpler than drilling to find well water. The borehole is generally smaller, which reduces drilling time, and no casing is required because the hairpin-shaped loop is the casing.
Geothermal Loops: Slinky Coils
An increasingly popular approach, especially in residential systems, is a "slinky" coil closed loop system.
A slinky is a coil of plastic tubing spread out and overlapped in a trench and buried. Slinky coils are installed horizontally at the bottom of a three-foot-wide trench.
This method concentrates the heat transfer surface into small volume, requiring less land area and shorter trenching - a big plus for homeowners.
A compact slinky will reduce trench length by about two-thirds; an extended slinky will reduce trench length by about one-third. Specific design lengths will vary with the climate, soil and the heat pump's run fraction.
Need more information on Geothermal…
Geothermal is a natural way to tap into the earth’s natural energy to efficiently and economically heat and cool your home. For more information on geothermal heating and cooling contact the experienced geothermal experts at K. Kelly at 920-469-3500 to get all your geothermal questions answered.
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