Systems layouts with additional heat storages for low-temperature PVT collectors assisting Heat Pumps for DHW production

Systems based on the coupling of heat pumps (HP) with solar hybrid photovoltaic and thermal technology (PVT) for domestic hot water (DHW) production are a valid alternative to conventional electric production systems. In previous research, simulation models were developed in order to study the dynamic behaviour of a plant set-up based on the integration of an air-to-water heat pump aimed at DHW production with a rated power of 700 W and a storage tank of 500 lt. It was coupled with a plant of 6 PVT flat uncovered hybrid solar collectors with a peak power of 300 W for each module. Starting from the results obtained in the pre-sizing stage, in this study, a plant configuration was analysed to maximize the exploitation of the low-temperature contribution provided by the adopted PVT collectors. With this aim, the efficacy of the introduction of a solar water preheating storage in addition to the one normally integrated into the HP was investigated. Different operational scenarios have been studied to evaluate the best energy management strategies to be implemented. They consider the influence that the thermal capacity of the solar storage could have on the system performance according to its volume and the setpoint temperatures. The obtained results show that the proposed plant solution generally allows an increase in solar energy exploitation for DHW production and a reduction in HP electricity consumption.