A Systematic Approach for Lifetime Evaluation of PV-Battery Systems

Battery energy storage systems (BESS) have recently been widely integrated to photovoltaic (PV) systems with the aim of increasing the control flexibility. To ensure the profitability under long-term operation of PV-BESS, lifetime evaluation is necessary during the design stage. In PV-BESS, the battery and power converters are the reliability-critical components that are subjected to high stress during the operation. This paper proposes a systematic lifetime evaluation framework for the PV-BESS where a three-stage modeling approach is applied to the battery and power converter lifetime estimation. The proposed lifetime evaluation also includes the interaction between the operation of the battery and power converter and its impact on the lifetime, which is the key novelty of this work. The framework is demonstrated on a case study of the PV-BESS in Germany. It reveals that the battery is the most life-limiting component, where the deep cycles and high average state-of-charge are the main factors limiting the battery lifetime. Additionally, the thermal stress of the battery converter is higher than that of the PV converter due to the high loading dynamic resulting from the battery charging/discharaing.