Experimental analysis of a renewable energy dual source heat pump system for decarbonizing residential buildings

The decarbonisation of the European building stock is a crucial challenge to reduce greenhouse gas emissions and improve energy efficiency. Buildings, responsible for around 40 per cent of total energy consumption in the European Union, need innovative solutions to reduce dependence on fossil fuels, particularly for heating and cooling. In this context, the European project ResHeat has developed an innovative system for the integrated generation of heat, cooling and electricity, designed to meet the energy needs of residential buildings on different scales. The ResHeat system consists mainly of a water-to-water heat pump, a hybrid photovoltaic-cooling system and two thermal storage units. Among the system's innovations is the use of waste heat from the cooling of the photovoltaic panels to maintain the energy levels of the heat pump's cold source constant, achieving a coefficient of performance of more than five. This paper focuses on analysing the experimental data collected following the construction of the demosite plant in Palombara Sabina and comparing the measurements with the model's forecast data. Thanks to the experimental monitoring of the operation of the plant in situ, it was possible to understand the actual effectiveness and potential of the ResHeat system in a mild climatic context such as that in Italy, critically analysing the recorded performance and identifying margins for improvement. The experimental data, which included heat pump operating temperatures, photovoltaic panel temperatures and energy data relating to both production and consumption, were compared with the forecast results of the mathematical model. Through monitoring, correlations between different operational quantities were analysed, allowing key factors influencing the mismatch between modelling and realisation to be identified. The quantities selected as input for the model included external climatic conditions and fixed flow rates known from measurements. The results show how the ResHeat system can optimise heating, cooling and domestic hot water production, reducing primary energy demand and improving overall system efficiency. Furthermore, the comparison between the experimental data and the simulations provided valuable insights for the refinement of the model and the system itself. The conclusions show that the ResHeat system, thanks to the innovative integration of renewable technologies, not only achieves significant energy savings, but also offers a replicable model for the energy efficiency of multifamily buildings, contributing to the achievement of the environmental sustainability targets set by the European Union.