Correlating Optimal Size, Cycle Life Estimation, and Technology Selection of Batteries: A Two-Stage Approach for Microgrid Applications

A challenge in designing a microgrid system is determining the optimal size of the battery storage system (BSS). The annual investment cost of a BSS depends mainly on its size and the estimated BSS lifetime, which is defined as the total number of charge/discharge cycles. This depends heavily on how deep the battery is discharged during each cycle. Therefore, it is particularly important to determine the BSS's optimal size, depth of discharge, and lifetime cycling when adding a BSS in a microgrid. This paper introduces a two-stage approach to determine the optimal size, maximum Depth of Discharge (DoD), and service lifetime (in years) of a BSS. The proposed methodology is implemented in the following two stages: 1) mixed integer linear programing planning algorithm is developed in the first stage to determine the optimal size, maximum DoD, and number of performed partial cycles; and 2) second stage, which implements the obtained results from the first stage to estimate the battery's lifetime in years and selects the battery technology, as well as the equivalent number of complete cycles. The effectiveness of the proposed framework is validated using numerical simulations, as well as a comparative case study.