Optimal battery capacity of grid-connected PV-battery systems considering battery degradation

The optimal capacity of a battery energy storage system (BESS) is significant to the economy of energy systems and photovoltaic (PV) self-consumption. In this study, considering the long-term battery degradation, a mixed-integer nonlinear programming (MINLP) model was proposed for the PV-battery systems which aim to minimize the life cycle cost (LCC) and was solved by a novel two-layer optimization method. This study compared optimal battery capacities, LCCs, and self-consumption ratios (SCR) under two types of tariffs with and without considering battery degradation. The effects of feed-in tariffs, feed-in limits and PV degradation on the optimization results are discussed. The results showed that the battery degradation could cause an increase in operation cost. The cases considering battery degradation have larger battery capacity and more life cycle cost than the cases without considering battery degradation. Compared with the feed-in tariff profile of flat rate, the cases with feed-in tariff profile of time-of-use have smaller optimal battery capacity, higher SCR, and lower LCC. The feed-in tariff, feed-in limit and PV degradation have an important impact on optimal battery capacity and total life cycle cost. This study provides an optimization method and theoretical analysis for the capacity and operation optimization of PV-battery systems. © 2021 Elsevier Ltd