Technical and economic assessment of a battery storage system for a nZEB in the Mediterranean climate

In recent years, the promotion of nearly-Zero Energy Buildings (nZEB), has become a priority for European member states. In order to get this label, typically, a monthly or yearly energy balance of energy use through the exploitation of renewable energy sources (RES) is required, but not a hourly balance. This approach may determine a low exploitation of the RES on site in the case of solar and wind energy, because they are intermittent by nature. Moreover, energy production and energy use peaks are often in mismatch during the day. Battery energy storage systems (BESS) offer a solution to better integrate RES into buildings as well as into the grid, increasing its reliability and minimizing interactions. The cost of these systems is rapidly decreasing, opening new economic opportunities for investors. However, for many applications they do not yet represent the optimal cost-effective solution due to the lifespan of their short-lived components. The paper investigates the technical and economic feasibility of integrating a BESS into a high-performance residential building in the Mediterranean climate based on the outcomes of an original case study based research. The existing photovoltaic system combined with the BESS may substantially optimize the energy use, maximizing the self-consumption and minimizing grid interactions; nevertheless, the pay-back time may become fully-attractive for the analysed building, only if BESS costs will halve by 2030.