TO-98-07-3 -- A Design Method for Hybrid Ground-Source Heat Pumps PDF

Although ground-source heat pumps (GSHPs) are recognized to be outstanding heating, cooling, and water-heating systems, a significant barrier to wider application of this technology is a high first cost, which makes short-term economics unattractive. One possible alternative that can lower first cost is the hybrid ground-source heat pump (HyGSHP) system. In many large buildings in the U.S., the required GSHP bore length for cooling is much greater than the required heating length. In these cases, it is possible to displace a large portion of the system cost by installing a ground loop large enough to meet the heating requirement in parallel with a fluid cooler or cooling tower to handle the cooling requirement.

The project on which this paper reports was proposed to analyze the impact of fluid coolers or cooling towers upon GSHP loop length design, annual ground loop heat buildup, system demand, and annual energy use. From this analysis, a design method was to be developed that simultaneously sizes the ground loop and fluid cooler. The conclusions of the project have attempted to address the needs of the GSHP design community.

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