On the Effect of the Time Interval Base and Home Appliance on the Renewable Quota of a Building in an Alpine Location

Abstract

The European goal of decarbonization drives design toward high-performance buildings that maximize the use of renewable sources. Therefore, the European RED II Directive and Italian law raise the minimum renewable share required for new buildings and major renovations. Currently, the renewable energy ratio (RER) is used for the mandatory verification, obtained with a quasi-steady state calculation on a monthly basis, while much of the scientific literature uses self-consumption factor (SCF) and load coverage factor (LCF) often calculated through dynamic simulation. However, the use of a monthly balance implies the use of the national grid as a virtual battery through the net metering mechanism. The actual share of renewable coverage in the absence of expensive electric storage will necessarily be lower. The link between the different indices, the effect of the time base used in the calculation as well as the actual renewable share achieved by buildings, considering also plug loads not in the regulatory verification framework, are still open issues. This work analyzes the actual renewable share achievable for a new building in a heating-dominated climate, i.e., the mountainous area of the municipality of Trento. The renewable share is evaluated through a coupled dynamic simulation of the building and the energy systems. The results show that the RER decreases by 13% and 15% when switching from monthly to instantaneous balance in the case without and with additional home appliance loads, respectively. Similarly, simulations show how the time interval base affects the difference between the RER index and the LCF of PV energy.