CH-24-C095 - Development of a High-Efficiency Cost-Effective Ground Source Heat Pump System for Subtropical Climate Applications

Ground source heat pump (GSHP) systems have the potential to achieve higher system efficiencies. However, a significant obstacle to widespread adoption of GSHP technology is the high initial costs primarily associated with the installation of underground heat exchangers. This study investigates the feasibility of integrating a dry fluid cooler into a vertical closed loop GSHP using advanced control strategies. The aim is to reduce the borehole lengths to improve the cost-effectiveness of the system without compromising its efficiency. With advanced control strategies, the system can switch between dry fluid cooler and vertical heat exchanger for optimal source as space heating/cooling demand occurs, to improve system efficiency. When there is no space heating/cooling needed, and weather condition is favorable, the dry fluid cooler can be used to precondition the underground, resulting in more favorable source from underground during heat pump operation. The developed system is expected to serve as a potential alternative in residential buildings, utilizing high-efficiency heat pump systems instead of conventional systems in hot/warm climates. A simulation model was developed in the TANSYS environment for the designed system deployed in a residential building located in Atlanta, Georgia. The simulation results indicate that the designed system can maintain the system's efficiency during long-term operation with an additional dry fluid cooler and shorter borehole length. The integration of a dry fluid cooler into a GSHP system, supported by advanced control strategies, has been proven to be effective for the studied house located in subtropical climates, such as Atlanta. When compared to a conventional GSHP system, the initial system costs can be reduced from decreased borehole length, while the system efficiency was maintained on an adequate level, due to the use of a dry fluid cooler.