Second-Life Battery Energy Storage System Deployment for Fast Charging of Electric Buses: A Scenario-Based Cost–Benefit Assessment

Abstract

Fast-charging sites for electric buses create short-duration high-power demand that can increase grid-capacity requirements and operating costs. This paper assesses the economic performance of second-life battery energy storage systems (BESS) at an operational electric-bus fast-charging site in Maribor, Slovenia. Using measured charging-demand data, this study compares baseline operation with three implementation scenarios: a small-scale BESS, a full-scale BESS, and a full-scale BESS integrated with photovoltaic (PV) generation. A 12-year scenario-based cost–benefit assessment (CBA) considers investment, grid-electricity, and operation and maintenance costs under the applicable network tariff. The results show that BESS-only configurations are not economically justified under the analysed conditions. Importantly, even a substantial temporary reduction in grid demand from approximately 150 kW to 60 kW produces only limited cost savings, demonstrating that technically effective peak shaving does not necessarily translate into economic viability. The strongest economic performance is achieved by combining BESS with the annual-demand-matched 92.4 kWp PV system, which substantially reduces annual grid-electricity demand and operating costs. Nevertheless, this configuration does not reach break-even within the 12-year assessment period; under the reference assumption of a 5% annual increase in grid-electricity costs, extrapolation indicates break-even in approximately year 18. The findings demonstrate that the economic value of second-life BESS at fast-charging sites depends not only on peak-shaving capability but on its interaction with tariff structure, grid conditions, and local renewable generation.