Techno-Economic Optimization of Vanadium Redox Flow Batteries for Large-Scale Stationary Storage: A Case Study at Fraunhofer Institute for Chemical Technology

Integrating battery energy storage systems is crucial for increasing the flexibility of power systems with a high proportion of variable renewable energy sources. Although lithium-ion batteries dominate applications due to their high energy density and falling costs, their use in large-scale stationary settings is limited by rapid capacity fade, performance degradation, safety concerns and reliance on critical raw materials. Vanadium redox flow batteries (VRFBs) offer a promising alternative due to their scalability, long lifetime, inherent safety, and the recoverability of capacity fade associated with electrolyte imbalance through periodic rebalancing. The optimization problem determines the energy capacity and installed power that minimize the total annualized cost within a predefined storage design range, including investment, operational, and market interaction costs. This is achieved using 2024 real power data at a resolution of 15 min from photovoltaic and wind plants, combined heat and power, and grid exchanges. The annual optimization assumes perfect foresight of electricity demand, generation, and prices over the investigated horizon. Within the investigated design range, the model selects the upper-bound energy capacity of 2000kWh together with an interior power solution of 625kW; this configuration reduces annualized system costs by about 8% compared to the no-storage scenario, achieving a levelized cost of electricity supply (LCES) of 0.0847 €/kWh. However, when degradation and end-of-life replacement are accounted for, the lithium-ion LCES increases to 0.09217 €/kWh under the baseline zero-residual-value convention.