Performance evaluation of battery-based energy storages for various duties

Licentiatavhandling, 2026

The growth of renewable energy increases imbalances between generation and demand, raising the need for frequency ancillary services. Battery Energy Storage System (BESS) are well suited for these services due to their fast response. However, Frequency Containment Reserve (FCR) operation affects both battery degradation and economic performance, making it important to assess the link between operation, ageing, and market remuneration.

This thesis evaluates the degradation and economic performance of BESS providing FCR services, including Frequency Containment Reserve for Normal operation (FCR-N), Frequency Containment Reserve for Disturbances upward regulation (FCR-D up), Frequency Containment Reserve for Disturbances downward regulation (FCR-D down), and combined configurations. A dynamic simulation with one-second frequency resolution is developed to model battery operation under realistic conditions, including SOC management based on Normal state Energy Management (NEM) and Alert state Energy Management (AEM). Semi-empirical calendar and cycling ageing models based on experimental data are reformulated to enable continuous degradation estimation, while cycling ageing is quantified using a rain-flow counting algorithm.

The results show that degradation depends strongly on the SOC operating range. FCR-D up exhibits the highest capacity loss due to long periods at high SOC, while FCR-N shows higher cycling degradation. In contrast, FCR-D down operates mainly at low SOC and shows the lowest degradation.

The economic analysis shows that combined services improve profitability. FCR-N+D achieves the highest annual net profit (1.10 MSEK) for 1 MWh/MW and has the shortest payback time 2 years, while stand-alone FCR-D services require 3 years to return the investment. A 50% reduction in remuneration still results in acceptable payback periods.