Geothermal Installation Techniques
Deep Well (Closed Loop Vertical) Direct Exchange ("DWDX")
One of the greatest benefits of ETA's patented geothermal technology is the fact that deep wells can now be utilized at depths from 100' to 300' per hole for a DX system, which requires less ground area exposure than a water-source system. The high cost and extensive drilling requirements for traditional water-source vertical ground loops have been one of the major hurdles to overcome when considering the installation of a geothermal system. Water-source technologies can require up to 250 feet of borehole depth per ton of design capacity. ETA's DX technology generally requires only 100 - 120 feet of depth per ton of design capacity.
Further, with the ETA system, the need for multiple small (50' to 75') wells in older, R-22 based, DX system designs are eliminated. For example, instead of having to use six 50' wells, the ETA technology only requires one 300' well to be installed. Such an ability to reduce borehole numbers, and to operate at significantly greater depths than older, first generation, DX designs, decreases installation time and expense, and increases geothermal heat transfer stability since near-surface temperature fluctuations caused by atmospheric conditions are no longer a significant factor.
ETA Deep Well Direct Exchange ("DWDX") System Installation Procedure
Step 1 - Deep well is drilled by licensed contractor.
Step 2 - ETA "seamless" ground loop is installed into the deep well, along with a 'trimmie tube' which will be used to transfer cementitious grout to seal up the well.
Step 3 - Deep well is grouted, from the bottom up, with Grout 111. Grout 111 was developed by Brookhaven National Laboratories specifically for geothermal applications. Unlike other grouting materials, Grout 111 is virtually water impermeable, is shrink resistant, is crack resistant, and boasts the highest known heat conductivity of any other known grout in existence. By utilizing this material, and grouting from the bottom up, your installer is providing a total seal around the well. This both protects the copper tubing and provides a safe sealant to prevent the cross-contamination of underground acquifers at varying depths.
Step 4 - A shallow trench is excavated to bury the copper tubing that will be used to connect the deep well to the compressor unit, which unit can be positioned either inside or outside your home or business.
Step 5 - The copper heat exchange loops within the well(s) are connected to the ETA compressor unit and to the interior air handler.
A DWDX system is generally the most efficient design, as the majority of geothermal heat transfer occurs at depths unaffected by near-surface atmospheric temperature fluctuations. Atmospheric conditions can affect ground temperatures down to about 65.5 feet, or 20 meters of the ground surface.
Other Installation Techniques
In-Ground Installation - When adequate land surface area is available, the copper heat exchange loops can be placed within mostly horizontally oriented trenches, about 4 to 6 feet deep. This installation procedure provides operational efficiencies close to those of a DWDX system, but is typically less costly to install.
In-Water Installation - When adequate water is available, such as a lake, a stream, a bay, or an ocean, subject to obtaining appropriate permits, the copper heat exchange loops can simply be placed under the water. This is typically the most economical installation procedure, which also typically provides operational efficiencies close to those of a DWDX system.
Pit System - The sub-surface heat exchange tubing can alternatively be installed within an excavated pit requiring about 600 square feet of area per ton of system design capacity. Here, a matrix of small 1/4 inch O.D. copper heat transfer tubing is placed at the bottom of the excavated pit, which pit is then back-filled. As with other near-surface design options, a pit system is typically less expensive to install than a DWDX design, but is more subject to atmospheric temperature flucuations and is not quite as efficient. However, all ETA system installations provide efficiencies that are far superior to conventional heating/cooling system designs.