Generic ground coupled heat pump systems (GCHPs) employing vertical and horizontal ground heat exchangers were analyzed to evaluate their performance in a hot, semi-arid climate. A detailed building energy simulation program was used to generate hourly thermal loads for a typical meteorological year. The peak and hourly loads were then fed into commercial GCHP simulation software to size the heat exchangers and estimate the annual energy performance. Performance was analyzed under different soil conditions and compared to the performance of a conventional air source heat pump. Unsaturated (dry) soil conditions increase the required length of the heat exchangers by approximately 33% compared to saturated soil conditions. Heat rejected to the ground under unsaturated conditions steadily increased the mean temperature in the soil adjoining the heat exchanger, degrading the energy efficiency of the system. A companion paper reports on the results of an economic analysis of the performance of these systems.
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