The role and benefits of storage systems in distributed solar PV generation on public buildings in Brazil

This paper proposes a method for assessing the energy and economic impacts provided by the adoption of battery energy storage (BESS) in public buildings with integrated photovoltaic (PV) systems under current legislation. The method is applicable to prosumer units (PU) connected on the medium voltage grid and is based on techniques for measuring the electric energy demand and the surplus PV energy injected by the PU into the grid. Empirical data, including ambient temperature and solar irradiation, were employed to assess the solar radiation resource. In BESS simulations, PU power flows were utilized. The BESS defined operation (charging/discharging schedules) was aimed at the maximum use of the surplus PV energy and the largest reduction in electricity expenses (energy arbitrage). The suggested methodology was applied to a case study of a public building PU in Brazil. The results showed that, during peak hours, the adoption of the BESS would provide a 100 % reduction in measured power demands and consumed energy with a significant annual injection of power in the utility grid. During off-peak hours, the annual self-consumption of the PU would increase by nearly 30 %. This outcome underscores the benefits associated with time-of-use billing structure for public PU + BESS. Approximately 85 % of the total energy required to charge the BESS would be originated from the surplus of PV energy. The remaining 15 % would be supplemented by the utility grid. The findings show that currently, the insertion of BESS would not present financial attractiveness. However, it is anticipated that BESS costs will drop during the next few years. A sensitivity analysis was carried out which concluded that for a cost of US$408 (expected value for 2025) the BESS would present financial attractiveness.