Cycle-life degradation assessment of Battery Energy Storage Systems caused by solar PV variability

With an ability to manage solar PV variability in one side and high capital investment in the other, Battery Energy Storage System (BESS) is considered as a critical asset in a PV plant. It is therefore essential to meticulously track the use of BESS in day to day operation and the resulting degradation of life. Due to the intermittent nature of BESS operation as an effect of PV variability, determination of the exact number of charge-discharge cycles a BESS undergoes, and hence the amount of cycling capacity loss it encounters, is not a trivial task. This paper investigates the impact of variable PV based operation of BESS on its cycle-life by applying “Rainflow Counting” algorithm - a generic cycle counting technique traditionally used for metal fatigue analysis. Conducted using data from a real PV plant in Australia, the case study presented in this paper provides a realistic idea of cycle-life degradation that may be caused by PV variability.