Effect of the Time Interval Base on the Calculation of the Renewable Quota of Building in an Alpine Context

The European goal of decarbonization drives design toward high-performance buildings that maximize the use of renewable sources. Hence, the European RED II Directive (EU, 2018) and the Italian decree (DL 8/11/2021) raise the minimum renewable share in new buildings and major renovations. In this framework, an air-source heat pump (ASHP) combined with an on-site photovoltaic system (PV) is one of the most popular solutions. However, the effectiveness of this heating system in mountainous contexts is not taken for granted, since the harsh climate induces both an increase in heating requirements and a deterioration of heat pump performance. For these reasons, energy simulation is a useful tool for understanding energy behavior and evaluate strategies to ensure the best energy savings. Currently, the renewable quota verification involves a quasi-steady state calculation on a monthly basis. However, this implies the use of the national grid as a battery through the net metering mechanism. The actual share of renewable coverage in the absence of expensive electric storage will necessarily be lower. This work analyzes the actual renewable share achievable in a new building in a mountainous area. Five representative locations in the province of Trento were initially identified through a cluster analysis. The renewable share was evaluated through a coupled dynamic simulation of the building and the energy systems. The results show how the calculated renewable share in this building changes according to the time interval used to close the balance with the grid. The evaluation of the renewable quota (QR) was carried out not only closing the balance by the hour or sub-hour but also by the month.