Analysis of Energy Saving Effect of Residential BESS Connected to Roof-top PV in a Multi-family House

The discussion about carbon neutrality has recently spread worldwide in response to the climate crisis. In Korea, the concept of zero-energy buildings is one of the means to reduce carbon emissions in the construction sector. Photovoltaic (PV) power systems are the most commonly installed renewable energy systems in residential buildings. However, the installed PV capacity in apartment houses is limited because of difficulty in securing PV installation area and inability to process the surplus PV power. Battery energy storage systems (BESSs) are emerging as a means for the storage and reuse of surplus PV power. In this study, the energy-saving effect of a residential BESS connected to a rooftop PV system was analyzed for eight households in a multi-family house. The data of the main load power (grid supply) and PV+BESS power from households collected from August to October 2021 were analyzed. During the operation of the BESS, the surplus PV power was stored in the battery, and the PV+BESS power was continuously supplied to the load by discharging the battery regardless of the PV power time. Based on the average representative data for 6 days, the power saving rate was approximately 26.0% for the rooftop PV system and approximately 41.8% for the BESS.