Electric/thermal hybrid energy storage planning for park-level integrated energy systems with second-life battery utilization

Abstract

The use of retired batteries from electric vehicles as a second-life battery energy storage system has been recognized as a way to break the high investment cost limitation of battery energy storage systems with the associated cost reduction of a park-level integrated energy system. The battery degradation and replacements should be further considered in the planning period, especially compared with new battery energy storage systems. Additionally, there is a lack of discussion on utilizing thermal energy storage systems in coordination with second-life battery to reduce degradation. For this reason, an electric/thermal hybrid energy storage system planning method for park-level integrated energy systems with second-life battery utilization is proposed. A cumulative battery life loss calculation model is developed. A bi-level optimal planning model of electric/thermal hybrid energy storage system using second-life batteries, including an upper-level planning model and a lower-level operating model, is proposed. At the upper level, to maximize the net present value during the planning stage, the capacity of the hybrid energy storage system as well as when the second-life battery energy storage system needs to be replaced are optimized. At the lower level, the operation schemes are optimized to obtain the minimum annual operating cost, which are fed back to the upper level. The proposed method considers continuous capacity degradation of second-life batteries and mutually beneficial relationships between thermal energy storage and second-life batteries. Finally, a case study demonstrates the economic effectiveness and battery service life improvement of the proposed planning method.