The Influence of Frequency Containment Reserve on the Operational Data and the State of Health of the Hybrid Stationary Large-Scale Storage System

The expansion of renewable energy with its volatile feed-in character places higher demandson the power grid of the future. Large-scale storage systems (LSS) are a promising option forsupporting the electricity grid and have been gaining importance in the last years, both on the marketfor frequency containment reserve (FCR) and in research. The majority of publications investigatingthe 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 hybrid6 MW/7.5 MWh battery storage “M5BAT” to address this issue. The influence of FCR operationon the operation and degradation of the hybrid LSS and the individual battery technologies isinvestigated via a statistical evaluation of the historical operating data between 2017 and 2021. Thedata-based analysis of the LSS and the individual battery technologies reveals a high availability ofthe 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 operationexposes that the lead-acid batteries have experienced a loss of energy capacity of up to 36%, whereasthe lithium batteries have only experienced a loss of up to 5%. The calendar ageing predominates inthis context. The presented results can be used to investigate and model the influence of FCR on theoperation and battery degradation of the LSS and its different battery technologies

The Influence of Frequency Containment Reserve on the Operational Data and the State of Health of the Hybrid Stationary Large-Scale Storage System

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

Balancing group deviation & balancing energy costs due to the provision of frequency containment reserve with a battery storage system in Germany

renewable energy sources in the power grid. Thus, control reserves such as frequency containment reserve aregaining in importance and need further investigation. In Germany, the power grid is divided into balancinggroups, in which supply and demand must be balanced out. The provision of frequency containment reserve,creates an imbalance in the respective balancing group depending on the grid condition. However, this energeticimbalance and the resulting costs for the balancing group manager are further to be quantified. This workprovides a simulation model that examines the energetic imbalances resulting from the provision of frequencycontainment reserve. We validate the simulation results with field-data from the operation of a 6 MW batterystorage system and derive the resulting cost for the energy imbalances. In addition, flexibility options for batteriesgiven by the regulatory framework in form of the degrees of freedom are evaluated. The results show, thatthe degrees of freedom enable a battery storage operator to additionally charge up to 8.68 MWh/MW frequencycontainment reserve per month or dis-charge up to 9 MWh/MW frequency containment reserve per month onaverage. The additional profits from the German imbalance settlement price vary on average between 302 € and1,068 € per MW frequency containment reserve per month. In Conclusion, the field-data confirm the simulationdata in terms of energy deviations in the balancing group due to the provision of FCR. Over the period of onemonth, the deviation usually leads to a cost-related advantage for the balancing group manager. The provision offrequency containment reserve as a grid service can therefore be seen as a positive gain for a balancing group

The influence of frequency containment reserve on the efficiency of a hybrid stationary large-scale storage system

Large-scale battery storage systems are predestined for balancing the fluctuating feed-in from renewable energiesand supporting the electricity grid due to their high efficiency. As a result, large-scale storage has gainedimportance in the market for frequency support reserve (FCR). While the first LSS projects had to be plannedwithout operational experience a couple of years ago, new LSS can benefit from the evaluation of measured fielddata. Especially the real-word efficiencies are key information for electricity procuring costs and arbitragetrading. To contribute filling this information gap, this paper investigates the efficiency of the hybrid LSS, itstransformers, its inverters, the individual battery technologies (two types of lead-acid and three types of lithiumionbatteries) and the influence of FCR provision on efficiency. High-resolution field measurements of the hybrid6 MW/7.5 MWh battery storage system “M5BAT” at the FCR market over several years serve as the basis. Thedata-based efficiency analysis reveals a high round-trip efficiency of 72.8% (with self-consumption: 66.2%) forthe LSS in operation. In this context, the lithium-ion batteries have a higher round-trip efficiency of 97.4% thanthe lead-acid batteries with 85%. Low load on the transformers and the inverters leads to an average powerweightedpower efficiency of less than 95%. The results presented can be used to model LSS and its varioussystem components and battery technologies in order to further analyse the participation in chosen energymarkets

Potential analysis of current battery storage systems for providing fast grid services like synthetic inertia – Case study on a 6 MW system

Large-scale battery energy storage systems (BESS) already play a major role in ancillary service markets worldwide. Batteries are especially suitable for fast response times and thus focus on applications with relatively short reaction times. While existing markets mostly require reaction times of a couple of seconds, this will most likely change in the future. During the energy transition, many conventional power plants will fade out of the energy system. Thereby, the amount of rotating masses connected to the power grid will decrease, which means removing a component with quasi-instantaneous power supply to balance out frequency deviations the millisecond they occur. In general, batteries are capable of providing power just as fast but the real-world overall system response time of current BESS for future grid services has only little been studied so far. Thus, the response time of individual components such as the inverter and the interaction of the inverter and control components in the context of a BESS are not yet known. We address this issue by measurements of a 6 MW BESS's inverters for mode changes, inverter power gradients and measurements of the runtime of signals of the control system. The measurements have shown that in the analyzed BESS response times of 175 ms to 325 ms without the measurement feedback loop and 450 ms to 715 ms for the round trip with feedback measurements are possible with hardware that is about five years old. The results prove that even this older components can exceed the requirements from current standards. For even faster future grid services like synthetic inertia, hardware upgrades at the measurement device and the inverters may be necessary