The expansion of renewable energy with its volatile feed-in character places higher demands on the power grid of the future. Large-scale storage systems (LSS) are a promising option for supporting the electricity grid and have been gaining importance in the last years, both on the market for frequency containment reserve (FCR) and in research. The majority of publications investigating the interaction between storage and FCR are based on simulations rather than on field measurements. This paper presents the analyses of multi-year, high-resolution field measurements of the hybrid 6 MW/7.5 MWh battery storage “M5BAT” to address this issue. The influence of FCR operation on the operation and degradation of the hybrid LSS and the individual battery technologies is investigated via a statistical evaluation of the historical operating data between 2017 and 2021. The data-based analysis of the LSS and the individual battery technologies reveals a high availability of the LSS of over 96.5%. Furthermore, the FCR operation results in an average SOC of the LSS of 50.5% and an average C-rate of the battery units of 0.081 C. A capacity test after four years of operation exposes that the lead-acid batteries have experienced a loss of energy capacity of up to 36%, whereas the lithium batteries have only experienced a loss of up to 5%. The calendar ageing predominates in this context. The presented results can be used to investigate and model the influence of FCR on the operation and battery degradation of the LSS and its different battery technologies.

Large‐scale battery storage systems have become popular for various grid services in recent years. A worldwide market growth for battery storage has led to increased competition in several grid service markets. Modular large‐scale battery storage systems require a safe, highly available, and intelligent energy management system (EMS) in order to be economically competitive. One component of this EMS is the control for distributing the power requests between individual battery units of the large‐scale battery storage system. As the EMS is usually undisclosed intellectual property of the system manufacturers, there is only little information on real‐world operation available. To contribute, we present a rule‐based power distribution algorithm (SPDA) in this paper and validate it through field tests on a 6 MW/7.5 MWh system that is providing frequency containment reserve to the German power grid. The results show that especially when combining different battery technologies, the SPDA can exploit individual technological strengths. In this way, the state of charge of the batteries, energy throughput and power load of the batteries can be controlled to extend the lifetime. Moreover, the SPDA managed to shift nearly 80 % of the energy throughput to one battery unit to protect less cyclic stable batteries and make use of the advantage of cyclic stable battery technologies, while fulfilling all grid service requirements. By shifting those large quantities of the energy throughput to more cyclic stable battery units, the large‐scale battery storage system experienced in sum up to 45 % less cyclic aging with the SPDA than with a symmetrical power distribution algorithm. Furthermore, the operational efficiency of a large‐scale battery storage system can be significantly improved via additional software adaptations of the power distribution, depending on the system layout.

Large-scale battery energy storages (BESS) are being used more and more for various applications such as system services in the power grid. The importance of their use in short-term energy trading, such as day-ahead and intraday trading, has been growing steadily due to increasing and more dynamic energy prices. In current technical and economic simulations and trading models, batteries are often represented as energy reservoirs that can charge and discharge a constant power within a specified time frame, which can lead to significant discrepancies between planned and physical delivery. Since batteries and consequently BESS cannot deliver the same power over the whole state of charge (SOC) range, their real operating ranges and limits have to be investigated in order to successfully use BESS in energy trading. With an intraday performance test of the lithium-manganese-oxide (LMO) batteries of our hybrid BESS M5BAT, we show capabilities and limitations of the battery units. The results show that the LMO batteries meet the performance and requirements of the intraday market over a wide SOC range. However, especially in the upper and lower SOC ranges, the power available from the batteries is reduced. When parameterizing trading models for batteries, special attention has to be given to the efficiencies of the batteries, power electronic components and transformers under the respective load points so that the deviations between the trading plan and reality do not become too large. Based on our results for a relatively aggressive profile, we find that LMO batteries are well suited for short-term energy trading applications, adhering to safe temperature levels in the case of our system. Further, we find that with the appropriate knowledge of efficiencies, short-term BESS operations can be optimized with sufficient accuracy. Using the example of M5BAT, this work provides insights in performance characteristics of the operation of BESS.