INNOVATIVE PHOTOVOLTAIC-THERMAL HEAT PUMP SOLUTIONS FOR DOMESTIC HOT WATER PRODUCTION

With the rapid growth of energy consumption in the building sector and the consequent necessity to develop energy efficiency strategies, the application of heat pump systems seems to be a competitive solution to improve energy efficiency. In particular, air-source heat pump (ASHP) systems assisted by solar energy have drawn great attention, owing to their great feasibility in buildings for space heating/cooling and hot ater production purposes. The complementation system between solar and air energy can solve the poor performance of the air source heat pump under low-temperature conditions and can also make up for the shortcoming of the solar collector as an unstable energy source. Both solar energy technologies and air source heat pumps (ASHP) are widely used renewable energy sources at the moment. The former has the advantages of low utilization cost, simple technology, easy access, and no pollution, while the latter has the advantages of high efficiency, energy-saving, and good environmental benefits. Among emerging technologies coupled to heat pump systems, PV/T hybrid solar collectors are estimated to have a high potential and a fast-growing market. The PV performance of PV/T collectors increases slightly compared with a panel with PV cells since the operating temperatures of the PV cells are reduced due to the cooling effect of the heat extraction. Solar-assisted heat pump systems for DHW and space heating purposes have been studied by several researchers. Both experimental investigations and numerical studies aimed to assess the potential and performance of various system designs under different climatic boundaries. The aim of the present thesis is the investigation of the energy performance of systems based on the coupling of air to water heat pumps with PV/T hybrid solar collectors for producing domestic hot water (DHW). The gains from using these two currently promising technologies and the benefits of their integration are investigated by analising different configurations of these integrated systems. Comparisons with more traditional technologies were performed both in terms of thermal and electrical power production and energy savings. In particular, investigations were performed in order to identify the optimal number of modules that make up the solar plant and the most performing technology with the purpose of this thesis among PV, PV/T, and ST collectors. Furthermore, two different integration configurations were analysed depending on the different functions of the thermal contribution of the PV/T string within the entire system. The simulations were performed both for the context of the mainland, considering the climate of Palermo (Italy), both for the context of the minor Mediterranean islands, with particular reference to Lampedusa (Italy). For the latter case, in particular, the impact of the substitution of existing fuel-based technologies with heat pump systems eventually coupled to a photovoltaic (PV), solar thermal plant (ST), and hybrid photovoltaic-thermal (PV/T) systems was analysed.