The earth absorbs an amazing 46% of the sun's energy, leaving a fairly constant underground temperature between 45° and 70° F. In the mid-atlantic area the average constant tepurature is 57° F.
When adequate land area is available the horizontal loop is used for new construction or retrofit applications of existing buildings. Depending on the loop design and application for your customized GeoThermal system, pipe trenches are prepared ranging in size from 5 to 8 feet deep and 100 to 300 feet long.
Since most projects, either new or retrofit, have limited land area the vertical loop is the most commonly used. A drilling rig is used to bore holes at of depth of 150 to 450 feet. A U-shaped coil of high density pipe is inserted into the bore hole. The holes are then backfilled with a grout type sealing solution.
The Vertical Loop delivers the best conductivity, requires the smallest area footprint and is generally the loop of choice for most retrofit projects.
This loop is an option if a body of water 8 to 10 feet deep and 1/2 acre in size is available within approximately 200 feet of the home. Several coils of pipe typically 300 to 500 feet in length each are placed in and anchored to the bottom of the body of water.
This system application is available if an abundant supply of high quality well water is available with a minimum of 4 to 8 gallons of consistent water per minute. An approved proper discharge area such as a river, drainage ditch, field tile, stream, pond, or lake must be available within a reasonable distance from the building. Many municipalities no longer approve this pump & dump type application.
The GeoThermal Process
The Water Furnace a GeoThermal GSHP
A GeoThemal GSHP is a central heating and cooling unit that pumps heat both from the ground and back into the ground. It uses the earth as a heat source (in the winter) or a heat sink (in the summer). These units are known by a variety of names including geoexchange, earth-coupled, earth energy or water-source heat pumps.
The core of the Water Furnace is the Ground Loop Exchange System. Using the flowing water from the Ground Loop, exchanging the temperature with the refrigerant and then sending it through a vapor-compression cycle, heat is moved into (during the winter) and out of (during the summer) the conditioned air in the building.
Unlike a conventional air-source heat pump, which transfers heat to or from the outside air, a GeoThermal GSHP transfers heat with the ground. GeoThermal GSHP systems are the most energy efficient space conditioning technology available.
The Delivery System
The heat may be carried to its end use by either circulating water (hydronic heated floors or baseboard) or forced air (duct system). A Liquid-to-Water GSHP is a hydronic system unit that use water to carry heating or cooling through the building. Systems such as radiant underfloor heating, baseboard radiators and conventional cast iron radiators would use a liquid-to-water GSHP. A Liquid-to-Air GSHP delivers forced air, and are most commonly used to replace forced air furnaces and central air conditioning systems.
For water heating, you can add a desuperheater to a Geothermal Water Furnace. A desuperheater is a small, auxiliary heat exchanger that uses the superheated gases from the GSHP compressor to heat water. This hot water then circulates to the building's storage water heater tank.
By creating a heat exchanger, also known as the Ground Loop System, the stored solar energy in the ground can be harnessed and delivered to the GeoThermal GSHP system in the building. The entire Ground Loop system is installed and enters the building below the surface grade.
There are three basic elements of a GeoThermal GSHP system:
Ground Loop --- A system of fluid-filled HDPE pipes buried in the ground or sometimes in a body of water, near the building
Water Furnace — A Geo GSHP unit which transfers the 57 degrees absorbed by the Ground Loop & manipulates it to heat or cool the building
Delivery System — Conventional ductwork used to distribute the conditioned air throughout the building or hydronic delivery by heated water.
Simply put, a Geothermal Geothermal GSHP system works much like the refrigerator in your kitchen, with the addition of a few extra valves that allow heat-exchange fluid to follow two different paths: one for heating and one for cooling. The GSHP, using the Ground Loop, moves the 57 degrees from the ground into the Water Furnace which then manipulates it to either heat or cool your building. Since a GSHP both heats and cools with only one indoor unit there is no more need for that noisy outdoor A/C unit ... and a natural byproduct of the process is free hot water heating during the summer.
Geothermal GSHP systems still use a small amount of electricity to run the pump, compressor & fan. However, it delivers $5 of energy for every $1 of electricity purchased. Unlike a conventional heat pump system, a GEO system use the relatively constant temperature of the earth as the source of heat in the winter and as a heat-sink repository for heat in the summer.
In the winter, the water passing through the underground (or underwater) sealed Ground Loop is warmed by the earth's heat. The collected heat is extracted and concentrated by the GSHP and distributed through the building's ductwork or hydronic delivery system.
To cool the building in the summer, this process is reversed — the heat pump collects heat from the indoor air and moves it into the Ground Loop where it is absorbed by the relatively cooler ground. The heat removed from the indoor air during the summer can also be used to produce free hot water.
At Four Feet Below Grade Each Vertical Well Connected to a Manifold Creates the Loop Field's In & Out Line Which Runs Into the Building and Transfers the Constant Ground Temperature to the WaterFurnace.