Earth Coupling Options
Geothermal systems can be defined as either open loop, closed loop, or standing column well. Since open loop systems rely on wells, ponds, lakes and streams as water sources they are generally less costly to install. However, water composition and water flow are open loop system factors beyond our ability to control. Closed loop systems do not rely on these uncontrollable conditions.
Open Loop (a.k.a. Pump’n’Dump):
Uses a relatively high flow domestic water well to supply the heat pump with 2-3 gallons of water per minute per ton (1 ton = 12,000Btu/Hr). Water is then discharged to a second well, body of water, drainage ditch, or storm water sewer.
Uses a relatively high flow domestic water well to supply the heat pump with 2-3 gallons of water per minute per ton (1 ton = 12,000Btu/Hr). Water is then discharged to a second well, body of water, drainage ditch, or storm water sewer.
Pros: Relatively inexpensive, constant supply water temp.
Cons: Relies on both water quality and quantity
Horizontal Closed Loop:
Used where adequate space is available, and depth to ledge allows 6’ deep trenches. Special fusion welded HDPE pipe is buried in trenches. A mixture of water and food grade propylene glycol is circulated thru the pipes to moderate temperature (replace heat removed by heat pump). Options include pipe laid out straight, or coiled like a slinky (to reduce trench length).
Pros: Doesn’t rely on water quality or quantity, no maintenance.
Cons: Requires fairly large area for excavation.
Used where adequate space is available, and depth to ledge allows 6’ deep trenches. Special fusion welded HDPE pipe is buried in trenches. A mixture of water and food grade propylene glycol is circulated thru the pipes to moderate temperature (replace heat removed by heat pump). Options include pipe laid out straight, or coiled like a slinky (to reduce trench length).
Pros: Doesn’t rely on water quality or quantity, no maintenance.
Cons: Requires fairly large area for excavation.
Vertical Closed Loop:
Used where lack of space or ledge prevent horizontal configuration. Bore holes are drilled using conventional well drilling equipment, a HDPE pipe loop is then inserted, and the bore hole is sealed using a thermally enhanced grout solution to improve performance.
Pros: Can be used anywhere (no lot size or ledge limitations), no maintenance.
Cons: Relatively expensive vs. other options
Used where lack of space or ledge prevent horizontal configuration. Bore holes are drilled using conventional well drilling equipment, a HDPE pipe loop is then inserted, and the bore hole is sealed using a thermally enhanced grout solution to improve performance.
Pros: Can be used anywhere (no lot size or ledge limitations), no maintenance.
Cons: Relatively expensive vs. other options
Pond Loop:
Coils of HDPE pipe are submerged in a body of water.
Pros: Relatively inexpensive vs. other closed loop options.
Cons: Body of water must be nearby and of adequate size and depth.
Coils of HDPE pipe are submerged in a body of water.
Pros: Relatively inexpensive vs. other closed loop options.
Cons: Body of water must be nearby and of adequate size and depth.
Standing Column Well:
This is a “hybrid” of open and closed loop systems. Water is returned to the same well it was drawn. Relies on well depth rather than flow to regulate water temperature. (Generally 350’, or more, depth required)
Pros: Can also be used for domestic water supply.
Cons: Water must meet manufacturer’s quality standards.
This is a “hybrid” of open and closed loop systems. Water is returned to the same well it was drawn. Relies on well depth rather than flow to regulate water temperature. (Generally 350’, or more, depth required)
Pros: Can also be used for domestic water supply.
Cons: Water must meet manufacturer’s quality standards.
