Thermal performance investigation on an optimal PVT-ground coupled heat pump system for a teaching building

With the continuous rise in energy demand and growing environmental concerns, the combination of ground-coupled heat pump (GCHP) and photovoltaic/thermal (PVT) is becoming a promising solution to improve the performance of the two renewable energy technologies. It is necessary for building energy supply system to enlarge the integration effect of solar energy and geothermal energy by optimizing their combination. This paper presents the thermal performance investigation on a PVT-GCHP system for a teaching building in Beijing. A mathematical system model is firstly proposed to optimize the combination of PVT array and double U-pipes borehole heat exchangers based on the available roof area and in-situ geological condition. The annual performance and energy flow of the PVT-GCHP system are focused in the presented numerical investigation. The result shows that the directly utilized solar energy and the ground heat provides respectively 37.5% and 35.5% of the annual energy input of the system. The PVT generated electricity accounts for 34.2% of the annual total electricity consumption, resulting in an annual season performance factor of the PVT-GCHP system up to 5. For the utilization of the two renewable energies, monthly solar fraction shows the large fluctuations, but the monthly renewable heat fraction is relatively stabilized from 71.3% to 95% after solar energy coupled with ground heat in the presented system, and the yearly value is promoted to 80%.