Types of Geothermal Loops

Closed Geothermal Ground Loops

The most typical geothermal installation utilizes a closed loop system.  In a closed loop system, a loop of piping is buried underground and filled with water or antifreeze that continuously circulates through the system.  There are four major types of closed loop geothermal systems:  horizontal loops, vertical loops, slinky coils and pond loops.

Horizontal Geothermal Ground Loops

If adequate soil or clay based land is available, horizontal geothermal ground loops are typically one of the more economical choices.  In horizontal geothermal ground loops, several hundred feet of five to six feet deep trenches are dug with a backhoe or chain trencher.  Piping is then laid in the trench and backfilled.  A typical horizontal ground loop will be 400 to 600 feet long for each ton of heating and cooling.  Because of the amount of trenching involved, horizontal ground loops are most commonly used for new construction.  Finally, because horizontal geothermal ground loops are relatively shallow, they are often not appropriate for areas with extreme climates such as the north or deep south.

source: U.S. Department of Energy

Vertical Geothermal Ground Loops

When extreme climates, limited space or rocky terrain is a concern, vertical geothermal ground loops are often the only viable option.  This makes them popular for use on small lots and in retrofits.  In vertical geothermal ground loops, a drilling rig is used to drill 150 to 300 foot deep holes in which hairpin shaped loops of pipe are dropped and then grouted.  A typical vertical ground loop requires 300 to 600 feet of piping per ton of heating and cooling.  Vertical loops are typically more expensive than horizontal loops, but are considerably less complicated than drilling for water.  Less piping is also required for vertical geothermal ground loops as opposed to horizontal loops as the earth’s temperature is more stable at depth.

Slinky Coil Geothermal Ground Loops

Slinky coil geothermal ground loops are gaining popularity, particularly in residential geothermal system installations. Slinky coil ground loops are essentially a more economic and space efficient version of a horizontal ground loop. Rather than using straight pipe, slinky coils, as you might expect, use overlapped loops of piping laid out horizontally along the bottom of a wide trench.  Depending on soil, climate and your heat pumps’ run fraction, slinky coil trenches can be anywhere from one third to two thirds shorter than traditional horizontal loop trenches.

Geothermal Pond Loops

If at least a ½ acre by 8 ft deep pond or lake is available on your property, a closed loop geothermal system can be installed by laying coils of pipe in the bottom of a body of water.   However, a horizontal trench will still be needed to bring the loop up to the home and close the loop.  Due to the inherent advantages of water to water heat transfer, this type of geothermal system is both highly economical and efficient.

Source: U.S. Department of Energy

Open Geothermal Ground Loops

With open geothermal ground loops, rather than continuously running the same supply of water or antifreeze through the system, fresh water from a well or pond is pumped into and back out of the geothermal unit.  Both an abundant source of clean water and an adequate runoff area are required for a successful open loop system.  While double well designs can be economical, use of open geothermal ground loops is generally discouraged and even prohibited in some jurisdictions.  Water quality is key to an open loop design as mineral content and acidity can quickly damage geothermal units.  Also, improper installation or runoff management of an open loop geothermal system can result in ground water contamination or depleted aquifers.

Source – Informed Building

Geothermal for your home- Benefits & Great Savings

Residential

A GSHP system can be installed in a residential structure of any size, anywhere, whether it is single-family or multi-family. GSHPs can be installed on almost any size lot: under lawns, landscaped areas, driveways, or the house itself. An existing house can be retrofitted with a GSHP using the ductwork that is already there. Your dealer/installer will be able to determine ductwork requirements and if any minor modifications are needed. Home builders and homeowners can both take advantage of the special financing that is offered in many locations on a GSHP either through the utility or manufacturer.

The Department of Energy (DOE) and the Environmental Protection Agency (EPA) have both endorsed ground source heat pump systems as among the most energy efficient and environmentally friendly heating, cooling, and water heating systems available. In a 1993 report, the EPA concluded that geothermal technologies represent a major opportunity for reducing national energy use and pollution, while delivering comfort, reliability and savings to homeowners.

Ground Source Heat Pumps offer great benefits:

  • Can be a combination heating/cooling and hot water heating system
  • Some can save you up to 50% on your water-heating bill by preheating tank water
  • Made of mechanical components that are either buried in the ground or located inside the home
  • About the same size as a traditional heating/cooling unit
  • Pipe carries up to a 50-year warranty
  • Can cut energy consumption by 20 to 50% and reduce maintenance costs
  • Keep the air warmer in the winter (90 -105¡ F) and at a more consistent temperature throughout the home, eliminating the hot and cold spots common with other systems
  • Very quiet, providing a pleasant environment inside & outside the home
  • No noisy fan units to disturb outdoor activities
  • No exposed equipment outdoors; children or pets cannot injure themselves or damage exterior units
  • No open flame, flammable fuel or potentially dangerous fuel storage tanks

GSHPs offer great savings:

  • One of the most efficient residential heating and cooling systems available today
  • Heating efficiencies 50 to 70% higher than other heating systems and cooling efficiencies 20 to 40% higher than available air conditioners
  • Save money in operating and maintenance costs
  • Investments recouped in only a few years
  • Positive cash flow; energy savings usually exceed the cost of the system
  • Some utilities offer rebates or incentives to their customers who purchase GSHPs. To see what your state has to offer click here.
  • Many heat pump manufacturers, local utilities, and lending institutions have special financing for homeowners who are installing GSHPs

GSHPs are environmentally friendly:

  • Conserve natural resources by providing climate control efficiently and thus lowering emissions
  • Minimize ozone layer destruction by using factory-sealed refrigeration systems, which will seldom or never have to be recharged
  • Uses underground loops to transfer heat, with no external venting and no air pollution

Source – IGSHPA