The types of geothermal heat pump systems differ by their earth loop type and the heat exchange medium. Presently, the most common forms of earth loops are horizontal, vertical, or diagonal. The two primary exchange methods are water-based and direct exchange.
Horizontal loops have the advantage of ease and simplicity of installation. Because these loops are typically placed at 6 to 8 ft. below grade, however, they are more subject to the temperature fluctuations the earth experiences at its surface. This variation in temperature causes a reduction in coefficient of performance (COP) over the winter season. Also, because these loops are shallow, there length requires and disturbs more land, and thus requires a property with space for this excavation.
Vertical loops, on the other hand, are more compact in their footprint. Because of their depth (typically 150 to 400 ft. depending on the project), they do not experience a significant COP fluctuation over the heating season. These systems, however, require more skill to install and also require larger equipment. Depending on the geology, this can slightly increase the costs of installation.
Diagonal loops are typically installed at a 30-degree angle from the horizontal and to a depth of 65 to 75 ft. These loops have the same advantages as vertical loops, but are particularly used for urban and some suburban installations, where space is at a premium for excavation and bringing in large equipment is more difficult. The one restriction on diagonal loops is that they are less suitable for very wet soil with bedrock at a significant distance below grade because the casing of the boreholes is more difficult at an angle than it is vertically.
Water-based systems use water and non-toxic antifreeze in special plastic tubing as the heat transfer medium for the earth loops. These earth loops then bring the heat into the heat pump, where it is transferred to the refrigerant loop and extracted with a heat exchanger. This design is resilient and well-tested, but it also loses efficiency because the heat must be transferred to two mediums before it is extracted. More heat transfer medium is also typically required, which translates into additional feet of earth loops and more energy required for loop pumping.
Direct exchange systems, also known as DX systems, eliminate the water intermediary, and use non-toxic refrigerant directly in ground loops made of copper tubing. Copper's high conductivity allows for very efficient heat transfer. This significantly increases system efficiency, meaning a higher COP is usually attained. In addition, the loop size can be reduced and the space required for drilling equipment is less than for water-based systems.
For a free consultation and geothermal heat system estimate in Syracuse, Ithaca, Rochester, Webster, Lansing, Fairport, Auburn, Cortland, Canandaigua, Pittsford, Geneva, Penfield, Brockport, Hilton, Spencerport and the surrounding New York area, call Halco at 1-833-844-2622 or contact us online.
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