GeoEnergy Enterprises

GeoThermal Technology

Conventional and Geothermal Heat Pump Basics
As the name implies, heat pumps simply take heat from one place and move it to another, much like one's refrigerator takes heat from its interior compartment and transfers it into the kitchen air and the window air conditioner takes that heat from the kitchen air and transfers it to the outside air it. Both of our example’s kitchen appliances are air source systems that use the ambient air as its heat reservoir to either take heat from the air (when used as a heat source) or send heat to the air (when used as a heat sink) utilizing the difference in the reservoir's temperature to maintain its efficiency. The basic issue with air source heat pumps is that they need, in winter, to remove heat from cold air and, in summer, send heat into hot air. A refrigerant gas (such as R-22, R-410a or R-407c) and an adequate differential temperature between the gas and the air is used to adsorb or reject the heat to or from the air.

ABSORBS HEAT IN WINTER

REJECTS HEAT IN SUMMER

Because the earth’s mass, when used as a ground heat source/heat sink reservoir, is more consistent in temperature all year-round, as well as being warmer in the winter and cooler in the summer than the ambient air reservoir, geothermal based systems work under much less strain than conventional air-to-air heat pumps. Thus less energy is consumed in their operation and geothermal have a much longer useful life as well due to this reduced strain and that the heat exchange system is not exposed to the outdoor elements.

Geothermal Comfort
Due to the lower ambient exchange temperatures utilized by geothermal HVAC systems in cooling mode, the latent heat reduction (removal of moisture) from the air is greater than that of air-to-air cooling systems, so that geothermal systems provide for a drier, more comfortable home in the hot, humid summer months. Also of note is that as geothermal systems in the heating mode do not overheat the air as with high temperature fossil fuel heating systems; air so heated by geothermal HVAC retains more of its moisture in the cold, dry winter months. Thus geothermal systems can provide in addition to energy savings a more stable and comfortable indoor environment year round.

Geothermal Heat Pumps
By way of background, there are currently three types of “conventional” geothermal systems in common use today:

the open loop water source,
the closed loop water source, and the
direct exchange system.

Examples of the 3 Common Water Source Heat Exchanger Types

Open Loop Water Source
The open loop water source geothermal heat pump system (see the “two well system” in above illustration) takes advantage of a large local source of water. This can be a large pond, a lake or river or more commonly, the “deep-well” aquifer itself which is also commonly used for drinking water. As its name implies, the system pumps water from the water source, extracts or expels heat from or to that water (using a water-to-refrigerant heat exchanger instead of an air-to-air heat exchanger as in our example above) and then returns the warmer or cooler water to its original source. As with all heat pumps the warmed or cooled refrigerant is then compressed to increase the heat value and sent either into the structure (using the hot gas to heat it) or to the earth’s mass (to remove the structure’s heat from the hot gas).

A variation of the open loop system is the open well system. In this system a very deep (often over 1000 feet deep) borehole is drilled through bedrock and filled with a water to form a “standing water column”. This water is then pumped, by a separate electrical water pump, from the standing water column and through a water-to-refrigerant heat exchanger as described above and then returned to the standing water column. This system is often used in large scale installations with a high bedrock incidence (such as found in New York City) where other types of geothermal HVAC heat exchangers are not practical. As you can imagine the well drilling costs can be higher than other types of water source systems.

Since deep-well aquifer groundwater is at a relatively constant temperature year-round it is an excellent source for a heat source or heat sink and where there is an adequate source of water, this is one of the cheaper geothermal systems to install and operate. However as ground water utilized in the heat exchange process in many areas of the country is also utilized as drinking water, the open loop's disadvantages are: direct contact with the ground water, cooling or heating of the ground water thereto, possible contamination of the ground water during the installation, pumping or exchange process, additional water pumping costs and the required maintenance of the return well (which, according to good practice should be 100 feet “downstream” from the supply well). Open loop water source systems also require professional engineering assistance the determine the water flows, rates and temperatures for successful operation of the system in both heating and cooling mode as well as plumbers and water well drillers for the installation process in addition to the HVAC personnel.

Closed Loop Water Source
The closed loop water source geothermal HVAC system by contrast circulates, by use of an electric water pump, a liquid (generally an antifreeze solution) through small diameter plastic pipe that is buried underground. The fluid then exchanges with the constant temperature of the earth’s mass (instead of continuously pumping fresh water) through these plastic pipes. This warmed or cooled fluid is then passed through a water-to-refrigerant heat exchanger where it performs a similar process of heat transfer as described above. There are two basic types of closed loop systems the horizontal loop, and the vertical loop.

Horizontal Water Source Trench with Plastic Pipe Array

The horizontal closed loop water source geothermal system’s plastic pipe is commonly laid out in trenches within the earth’s mass and less commonly laid out in a large body of water such as a large, deep pond or lake (commonly called a “pond loop” system).

The vertical loop system is basically numerous drilled small diameter boreholes that are normally several hundred feet in depth. Similarly to the horizontal loop system above small diameter plastic pipe is installed into these boreholes where the also similar fluid to earth’s mass heat transfer takes place.

As “pond loop” systems are the exception rather than the rule, both the horizontal and vertical loop systems often require expensive deep well-type drilling or vast horizontal trenching (as well as the land area to do so) to install. The heat exchangers (the small diameter plastic pipes) require a certified professional to engineer the loop to the soil conductivity and are assembled “in-the-field” requiring expert tradesmen to weld these pipes together so that they do not leak under pressure.

All water source geothermal HVAC systems may also require the utilization of licensed plumbing contractors in addition to the engineers, excavator/drilling personnel, plastic pipe welding and HVAC personnel. All water source heat exchangers, in the event of a field failure (fluid leak, low water well levels) require reinstallation of the heat exchange system or new wells dug.

Direct Exchange
The direct exchange (DX) system is a series of copper tubes buried in trenches4 to 6 feet below ground level or in deep vertical boreholes. Refrigerant gas is then fed through these so buried copper tubes creating a direct heat exchange between the temperature of the ground and the heat transfer medium, which in this case is the refrigerant gas (as you can see this eliminates the water-to-refrigerant heat exchanger and the electric water pump too). Because of this direct exchange feature these systems can operate at lesser costs than water source systems. DX should also be less expensive and complex to install as it requires no water well drilling or plumbing costs. As copper is a more efficient heat transfer medium than PVC pipe as found in water source, trenching costs are less due to less ground mass being required by DX. As with water source heat exchangers a leak in the system requires reinstallation of the entire heat exchange field.

Direct Exchange Field and Trench/Pit

GeoColumn™ - The Hybrid Geothermal Heat Exchanger
In response to the shortcomings of current geothermal heat exchanger systems GeoEnergy Enterprises, LLC (GEE) has developed and patented a new, cost effective, hybrid, shallow-well heat exchanger system, the revolutionary new GeoColumn™.

The GeoColumn

The GeoColumn patent covers a sub-terrain heat exchanger consisting of a containment device containing a standing column of fluid which is 100% water (unlike certain other geothermal systems no antifreeze is required) and a refrigerant-to-water heat exchanger. The refrigerant gas exchanges heat with the water column, which, depending on the mode of operation, causes the water to either rise or fall within the containment by natural convection effect. Heat is then exchanged through the wall of the containment with the earth’s mass.

The GeoColumn heat exchanger unit is 28 inches in diameter by 20 feet long, per ton of conditioning required, and installs within a borehole that is 23 feet deep. This compares to 450 to 900 square feet of land surface area, per ton of conditioning, for horizontal loop systems or to the 100 to over 1500 foot boreholes or wells, per on of conditioning, typically required for vertical plane geothermal heat exchanger systems.

The GeoColumn is pre-engineered to your region and soils and using a componentized heat exchanger such as the GeoColumn greatly reduces the expense and complexity of field design. The GeoColumn can be quickly installed with utility pole type digger-derrick drilling equipment or with caisson type pressure drill rig equipment. This consequently enables the GeoColumn to be installed in much less time that other systems and thus reduces the drilling expense which is often a cost barrier to the use of geothermal HVAC.

The small footprint of the GeoColumn is ideal for all types of installations, new and retro fit, but is especially suited for geothermal usage in areas of limited ground areas, such as in urban or suburban areas. GeoColumns can be placed below sidewalks, driveways, lawn and garden areas or, in new construction, even underneath the foundation!

GEE's GeoColumn heat exchanger units are coupled to GEE indoor components (a compressor section, air handler, etc.) to provide heated and cooled air and hot water and it may also be used for hydronic heating systems as well. These GeoColumn based systems provide many advantages over conventional fluid based geothermal equipment since it generally requires a smaller land area to install and eliminate the use of pumps and fluid-to-refrigerant heat exchangers. This alone may provide cost savings of 35% to 50% or more over other conventional geothermal equipment’s installation. GEE’s systems are also much easy for any competent HVAC dealer to install than a conventional water source geothermal unit since it does not require the use of engineers, plastic pipe welders, plumbing professionals and/or well drillers/trench excavators for installation. In the event of a field failure as the top of the GeoColumn is only 3 feet below the surface any necessary repairs can easily be made in the field.

Please go to the GeoColumn tab for more info on the GeoColumn technology…