A Dynamic Model of Redox Flow Batteries with Solid Boosters

It is imperative to enhance the energy density of redox flow batteries (RFBs), reaching higher energy-to-power ratios, and enabling long-duration energy storage while keeping costs and volume down to reasonable values. The adoption of solid boosters embedded in the electrolytes storage tanks is a promising solution from this point of view. A 0-D dynamic model is presented, targeting a compromise between accuracy and computational time, to study the effect of the adoption of solid boosters on the process performances of RFBs. The model considers a multi-cell stack configuration which includes overpotential, pumping and shunt current losses, and introduces a lumped approach for the simulation of the mass transfer, surface reaction and solid-state diffusion phenomena in solid boosters. Sensitivity analyses are carried out to investigate the effect of the main parameters of the solid boosters on the system performance, applied to aqueous organic electrolytes. Roundtrip efficiency values higher than 76% are found with an increase of the energy stored by ca. four times. The model presented is the first of its kind, enabling a quantitative assessment of the RFB use at system level. The numerical results shed light on how to maximise the benefits introduced by solid boosters.