Sizing strategies of photovoltaic systems in nZEB schemes to maximize the self-consumption share

The integration of renewable energy systems in buildings has become a common practice. The design of net Zero Energy Buildings promotes the energy transition from fossil fuels based technologies by coupling renewable systems as photovoltaic (PV) plants with heat pumps for heating and cooling. In this framework, the correct sizing of PV plants plays a central role in the perspective of the definition of self-consumption schemes. Considering the problems related to small-scale photovoltaic plants, the present paper proposes an analysis of different sizing strategies on the energy streams between the building and the electrical grid to reduce the bidirectional energy flows with the electrical grid. The design objective concern the minimization of both the energy exported and imported through an optimized size of the PV plant and the integration of electrochemical energy storage. The investigation is based on the experimental data under real operating conditions obtained from two different residential buildings, a conventional residential house, and a nearly Zero Energy Building (nZEB). The paper aims to discuss the results of the monitoring activity and define criteria and guidelines for the design of this kind of systems based on real collected data. The use of two different self-consumption indexes helps to determine how close the system is to a zero-energy configuration showing that the use of a small to medium size storage system is fundamental for maximizing the self-consumption share of the energy produced.