Batterienergilager som flexibel resurs i elnät : Potential, ekonomiska beräkningar och praktiska utmaningar i jämförelse med nätutbyggnad vid kapacitetsbrist

This thesis explores the potential, implementation, limitations, and benefits of using flexible resources, specifically battery energy storage systems, as an alternative to traditional grid reinforcements during peak load hours, from the perspective of a distribution system operator (DSO), Ellevio. The study examines real-world cases and operational data from Ellevio to assess whether flexibility could serve as an alternative to costly and long-term grid reinforcements during limited peak load conditions. The analysis also includes one case where BESS is used to avoid increasing the upstream network subscription limit and the associated overcapacity charges. The potential of limited peak-shaving through demand response is also considered as a complementary strategy. The study assesses the economic viability of flexibility compared to grid investments within the current regulatory framework (RP4), while also discussing upcoming changes under regulatory period 5 that may influence future decisionmaking. Special attention is given to the dimensioning of the flexible resource, implementation challenges, and a comparative cost analysis over time. Due to regulatory frameworks, it is not economically viable for DSOs to own batteries for this purpose. Therefore, flexibility must be purchased through third-party contracts. The study also examines market prerequisites for flexibility services and the conditions necessary for future market development. Furthermore, flexibility is investigated as a transitional solution during the lead time for planned grid reinforcements. The study applies a mixed-method approach. A literature review is combined with qualitative insights from interviews with representatives from Ellevio and the battery supplier Energy Solutions. In addition, a quantitative model was developed and implemented using NetBas, Python, and Excel to evaluate technical and economic outcomes under various scenarios. The findings indicate that flexibility, when used as a bridge solution, can improve overall cost-efficiency for DSOs while enabling faster connection of new customers, thereby increasing customer satisfaction. However, to enable the use of flexibility as a permanent solution, further developments are required both within the regulatory framework and in internal DSO processes. Such solutions are most viable when overload situations occur during a small number of short peak load events, rather than extended periods of high energy demand. Under the current regulatory framework, traditional grid reinforcements are economically favorable for DSOs regardless of cost. However, upcoming changes in the next regulatory period are expected to incentivize alternative solutions that enhance overall economic efficiency, particularly through improved network utilization.