Geo-exchange Totally Explained

Everything about Geo-exchange totally explained

A Geo-exchange system utilizes the near-constant (less than 35 feet) or constant (more than 30 feet) temperature of the ground to heat or cool. It is a type of Heating, Ventilating, and Air-conditioning (HVAC) system (some systems don't incorporate ventilation, however). Geo-exchange systems are usually comprised of a target structure (the building to be heated/cooled), a heat pump, and a sink.
The heat pump consists of working fluid, a loop field, and a heat exchanger. The working fluid flows through the loop field and the heat exchanger.
Geo-exchange is more than just a Natural Building technique. The system allows one to cool a structure in the summer and heat a structure in the winter. These systems typically have a greater coefficient of performance than most typical HVAC systems.

Thermal Exchange

Open to diffusion wells

Most common in areas with near-surface and plentiful water, this type of exchange system draws water from the earth through a geothermal heat pump. Energy is alternately extracted from the water (winter) or added to it (summer). The water is then returned to the earth by means of a diffusion (reinjection) well or, if permitted, to a surface-level body of water.

Standing Column Wells

Most common in areas where bedrock is within 150-200 feet of the surface. Water is drawn from the bottom of a deep rock well, passed through a geothermal heat pump--where energy is either extracted (winter) or deposited(summer)--and returned to the top of the well, where traveling downwards heats up in winter and cools off in summer. The choice of a Standing Column Well is often dictated by a large urban application or a rural application with an existing domestic water well.

Indirect

Type of system used where a heat exchanger either extracts or injects heat. Pipes or tubes are placed within the ground and act as a heat exchanger. The working fluid is usually water. Sometimes, however, air, glycol, or something else may be used. The choice of working fluid is generally based on economics, efficiency, or abundance.

Direct

Earth tubes are a type of geo-exchange where the heating/cooling is direct because these systems lack a heat exchanger.
Like other building techniques it has properties that would prohibit its use in certain geographical places unless the additional hardships, like mold, are addressed.

Arrangement

A Geo-exchange system may be open or closed. This refers to the way the loop field is arranged.

Closed

A closed system has a working fluid that stays enclosed within the pipes used. A closed system is more common for many reasons including but not limited to cost, energy use, and simplicity. These systems typically use a heat pump.

Open

An open system would have the working fluid enter from a source, like the city water supply, go through the geo-exchange system, and exit the system, like come out of faucets. These systems don't use a heat pump.

Configurations

A Geo-exchange system may have its working fluid conduits (pipes in many cases) configured mostly horizontal or mostly vertical. Rarely are the conduits configured in a hybrid fashion, although this is entirely possible.

Vertical

Vertical configurations place the pipes from the surface down holes or wells at least 100 feet to usually no more than 500 feet.

Horizontal

Horizontal configurations place the pipes in trenches. These trenches may be either in a large pit or encircle the structure.

Confusion

With so few users of this technology (not much more than 1 million) in the US, others have a hard time understanding the technology and relating this to others. This has led to confusion.

With Geothermal

It appears many websites confuse geo-exchange for geothermal heating. Geothermal uses very hot (100+*C) subterranean regions to generate electricity. This is usually, but not always, done by phase changing liquid water to steam that powers a turbine which produces the electricity.

With Heat Pumps

It appears that others also confuse this term with Geothermal heat pump and Geothermal exchange heat pump as well. The term "geothermal exchange heat pump" is an amalgamation of "Geo-exchange" and "Geothermal heat pump." The term "geothermal heat pump" refers to a system in general where a heat sink is used to dump heat from a system, but not necessarily where a single source, like a home, uses the near constant or constant temperature of the near surface of the ground to provide near constant temperatures within the structure.

Further Information

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