Improvement of energy self-sufficiency in residential buildings by using solar-assisted heat pumps and thermal and electrical storage

To reach the EU 2030 goal of reducing greenhouse gas emissions targets, many apartments within residential buildings can be equipped with rooftop or building-integrated PV systems. However, as non-programmable renewable energy sources (solar, wind) are characterized by uncertainty and fluctuation, it is very difficult to match the supply with the demand for the building's energy needs. Thermal and electric energy storage play a fundamental role in maximizing self-consumption, reducing the difference between peaks and valleys of the energy demand, and improving the electrical system's flexibility. In this study, the performances of an energy system composed of an electric heat pump (HP) fed by a PV plant and both thermal and electric storage are investigated. An innovative logic of the charge and discharge of the two storages as a function of energy generation and demand has been developed with the aim to optimize the energetic self-sufficiency of typical residential buildings. The results of the analyses carried out evidence that the system configurations with a thermal storage of about 1.000 L and an electrical storage of 5.0 kWh allow achieving rates of self-consumption and self-sufficiency of about 80%, which are 3 times higher than that one achievable by an energy system without storage. Moreover, this system configuration reduces dramatically the power exchange with the grid. The outcomes of this study are useful to provide indications for the design of the storage in combination with a solar-assisted heat pump system avoiding the recurrent praxis of oversizing of more than 100% of the electric storage.