PERFORMANCE ENHANCEMENT OF A RESIDENTIAL SCALE GROUND SOURCE HEAT PUMP SYSTEM WITH SOLAR THERMAL ENERGY

Unlike conventional space heating and cooling technology, heat pumps can provide both heating and cooling efficiently. When coupled with ground heat exchangers, they have low operational costs and can provide reliable heating and cooling for a long period of time. Nevertheless, in a climate where there is an unbalanced annual need for cooling and heating, performance degradation and eventual system failure have been reported. A number of researchers have considered complementing ground source heat pump systems (GSHPs) with solar thermal energy to improve their performance in cold climates. However, in the context of the lithological and metrological conditions in the extremely cold climate of Alberta, Canada, there are limited studies. The aim of this work is to analyze the performance enhancement of a solar-assisted ground source heat pump (SAGSHP) for a residential building in Calgary, Canada. In this study, the performance of a 150 m vertical borehole ground heat exchanger (VBGHE) with two independent double u-loop pipes is numerically investigated using a realistic dynamic building load profile. The numerical solution of the governing equations, together with the boundary conditions, was implemented in a finite-volume computational fluid dynamics tool for a conventional and enhanced VBGHE. Results show that using solar thermal energy can improve or maintain the ground thermal balance and the system’s coefficient of performance (COP). Overall, an annual average heating COP of 3.70 and 3.03 was achieved for SAGSHP and GSHP, respectively, at the end of the fifth year of operation, with 17.4% savings in heat pump unit energy consumption.