Improved Energy Arbitrage Optimization with Detailed Flow Battery Characterization

This paper elaborates on the characterization of vanadium redox flow battery (VRFB) performance for energy arbitrage optimization based on the experimental data obtained in-house. Typical figures-of-merit used for evaluating VRFBs include coulombic, voltaic, and energy efficiencies. However, these metrics along with the deliverable power vary as a function of discharge/charge current during cycling. Thus, using a basic energy storage model with constant efficiency and fixed maximum power is not a rigorous approach for predicting the performance of VRFBs in applications with variable supply/demand of electricity. Moreover, optimization based on such an oversimplified treatment may result in inaccurate battery dispatch signal and may overestimate arbitrage profit. Here, we propose a more detailed VRFB model with dynamic efficiency and maximum power limits as a function of state of charge (SOC). These data were obtained using lab-scale VRFB cells over a range of operating conditions. The dynamic model's performance is compared to the basic model for various day-ahead electricity price profiles. Substantial difference between the predictions of two modeling approaches on the battery dispatch and profits was observed. The results indicate that the dynamic model provides more accurate predictions on the battery performance for applications with intermittent energy profile.