Exploring the value-stacking opportunities of batteries providing frequency containment reserve services in different regulatory environments

Abstract

The security and reliability of the European power system network that is used to transmit electricity from producers to consumers is under increasing pressure. The penetration of renewable energy resources that have a variable and unpredictable energy output and the rising cost of the operation of fossil-based power generators are negatively influencing the availability of controlling power that is critical for normal system functioning. Without this controlling power, there is a risk of electricity network imbalances and complete electricity blackouts. To be able to guarantee the continuity of electricity supply, transmission system operators are required to search for new and alternative flexibility resources, including resources that could provide the primary system response (frequency containment reserve) to these grid imbalances. Battery energy storage systems are one of the most promising alternative resources that could provide this load controlling capacity. These systems are, however, extremely cost-intensive. Using a battery for multiple battery applications simultaneously could improve the financial viability of these battery energy storage systems and thereby, accelerate their deployment in society. To be able to get the full potential out of this value-stacking opportunity, more insight into the technical and operational compatibility of using a battery for frequency containment reserve and other battery applications is required. In this master thesis, a research was conducted to obtain a better understanding of the opportunities to create added value in the utilization of a battery that is providing frequency containment reserve services. By means of a (multiple-)case study research (including a literature review, a simulation model and a time series analysis and forecasting model), more insight was obtained in the power and energy capacity utilization of a battery that is providing frequency containment reserve services and the usability of the leftover capacities of this battery for serving other battery applications. In the literature review that was performed, it was demonstrated that the activation of batteries for frequency containment reserve is mainly dependent upon the regulations and grid characteristics that are present in the area of interest. These regulations provide terms and conditions for the theoretical use of a battery’s power and energy capacity and therefore, the theoretical opportunities for valuestacking. These value-stacking opportunities include the use of moments in which a battery is idle and the time periods in which a battery is not using its full energy capacity. The simulation study that was performed subsequently showed that for all frequency containment reserve markets examined in this research, there are moments and periods in time in which a battery is not using its entire reserved frequency containment reserve power and energy capacity. This indicates that using a battery at these particular moments and periods in time for other battery purposes might create substantial added value to the overall system operation. The analysis of the data that was obtained from the simulation study showed that the practical usability of these moments and periods in time for value-stacking opportunities seems limited. Although it was illustrated that there are moments in which the battery’s power capacity is not used, no clear prediction can be made of these so called ‘idle moments’. Consequently, it is uncertain at what exact moments in time the battery is idle and could be used for other battery purposes. The duration of the idle moments is furthermore relatively short, which makes it difficult to use these idle time periods for applications that require consecutive power supply or energy storage. Results of the time series analysis and forecasting model demonstrated that there might be opportunities to predict the required energy capacity for frequency containment reserve. This indicates that forecasts can be made of the state of charge development of a battery over a certain time period. This information can be used to identify the underutilized battery energy capacity, which subsequently could be used for other battery applications. The combination of both the power and energy capacity limitations prove to be a challenge when aiming at value-stacking of a battery. Using the idle moments and the forecasted available energy capacity of a battery for other battery applications requires expert knowledge of the energy capacity that is needed for the additional application and seems to require flexibility of power capacity utilization of the additional application itself. Further research should focus on the improvement and validation of the frequency containment reserve activation forecasts to be able to make a better estimation of the battery energy capacity that is available for serving other battery purposes. Research should moreover be conducted to examine the energy and power requirements of other applications over time. This includes the need for state of charge control. The information that is obtained from these studies is essential to identify how various battery applications, including frequency containment reserve, can be properly aligned and could add value to the battery system operation.