Investigation by monitoring and numerical simulation of the performance of a ground-source heat pump system with and without regeneration in different configurations and operating modes

Abstract

This paper is focused on restoring the thermal imbalance of the ground caused by conventional GCHP systems through seasonal and continuous regeneration using a geothermal-solar facility with a vertical GCHP combined with photovoltaic (PV) and PV-thermal (PV/T) panels in a heating-dominated climate, located in Timisoara, Romania. Therefore, the performance of a GCHP system integrated into the heat supply system of an experimental office, operating in single and double U-tube borehole heat exchanger (BHE) configuration, with regeneration in the summer months by injecting heat into the ground, is experimentally evaluated. Exploratory research has indicated an increase in the average temperature of the working fluid by 2.4% and an improvement in system performance when using heat injection (seasonal performance factor (SPF) by 3.5% and 6.6% higher and CO2 emission by 1.2% and 3.8% lower in the single and double U-tube BHE configurations, respectively). Additionally, numerical simulations with Polysun software are also used to test the performances of the hybrid GCHP-PV/T system with continuous regeneration throughout the year by PV/T panels and of a conventional GCHP integrated into the heating and DHW production systems for a single-family building. The simulations were experimentally validated through measurements on the geothermal-solar facility for heating and DHW production in the experimental office. The simulation results show that the SPFHP-PV/T values of the hybrid GCHP-PV/T system in the single and double U-tube BHE configurations, equal to 6.00 and 5.79, respectively, are 32% and 34% higher than the SPFHP corresponding to the conventional GCHP system, equal to 4.56 and 4.32, respectively. In addition, the SPFHP-PV/T in the single U-tube BHE configuration is 3.6% higher than in the double U-tube BHE configuration for the GCHP combined with the PV/T array (31.8 m2).