Optimal Multi-Use Operation of Utility-Scale Battery Systems: Techno-Economic Feasibility Study of the M5BAT Hybrid Storage in Aachen

Large-scale battery storage systems (LSS) have found widespread application in frequency regulation and spot markets across Europe. However, the single-use operation of LSS is typically not economical and depends on fluctuating market prices. Therefore, combined multi-use approaches are necessary to achieve an economically robust operation of LSS and promote their expansion.

The hybrid 6 MW / 7.5 MWh battery storage system “M5BAT” is composed of five different battery technologies and actively participates in the frequency containment reserve (FCR) market. This work aims to find the optimal utilization strategy for the existing plant by combining different applications in an intelligent way. For this purpose, a mixed-integer linear programminng (MILP) optimization approach is proposed.

We evaluate applications such as energy arbitrage, frequency containment reserve (FCR), and automatic frequency restoration reserve (aFRR) in single and combined operation. Furthermore, proxys for battery aging, such as opportunity costs per unit of energy throughput, are considered in the profit-oriented optimization of the operation. The balance between capital costs and revenue is translated to important constraints when trading battery storage systems and is especially relevant for cycle-intensive applications such as energy arbitrage.

Simulation results suggest that the multi-use concepts explored result in higher revenues than the operation of single applications. In average, monthly revenues for the combined operation of FCR, aFRR, and energy arbitrage are 135 % higher than for the traditional individual FCR operation of LSS in 2022. Furthermore, the importance of sufficiently detailed technical modeling of LSS is highlighted in the context of scheduling and trading algorithms.