A computationally efficient, zero-dimensional stack model for simulating redox flow battery performance

Scaling redox flow battery (RFB) innovations from single cells to stacks is an important step for concept validation, but this procedure is challenging, as new processes emerge that impact performance and durability. Models that facilitate performance predictions from material properties and single-cell measurements can inform stack engineering and streamline iterative design-build-test cycles. Here, we deploy a semi-analytical zero-dimensional modeling framework to rapidly simulate stack cycling performance, focusing on failure modes relevant to RFB scale-up (i.e., shunt currents, pressure losses, crossover). We first investigate the computational efficiency of the model, yielding simulation times under 0.04 s per cycle—significantly faster than prior stack models described in the literature. Next, we explore the role of shunt currents in RFB cycling, discussing the theoretical underpinnings of these parasitic losses and providing generalized stack performance predictions under variable operating conditions. We then apply the model to evaluate engineering considerations for emerging aqueous-organic RFBs— specifically, we show that (1) higher current densities reduce the impact of shunt currents; (2) larger port cross-sections enhance round-trip efficiency, provided requisite port lengths are achieved; and (3) lower membrane resistances facilitate higher current densities, mitigating the impact of shunt currents while amplifying capacity fade via crossover.