Mitigation of losses from hydrodynamic mixing in a hydrogen bromine Laminar flow battery

Abstract

The hydrogen bromine laminar flow battery is a promising technology for grid-scale energy storage. It dispenses with the expensive membrane used in traditional flow batteries, instead using laminar flow to maintain the separation of fluid streams. It also takes advantage of powerful, inexpensive chemical reactants. However, mixing between the fluid streams within the battery reduces its single-pass performance and cyclability. Conditions at the inlet junction where oxidant and electrolyte streams come together are thought to influence mixing. This work investigates the relationship between fluid flow at the inlet junction, mixing, and battery performance. Matching electrolyte- and oxidant-stream flow rates or velocities is predicted to cause less mixing than employing hydrodynamic focusing of the oxidant stream. When hydrodynamic focusing is used in channels with heights on the order 500 [mu]m or less, numerical simulations show recirculating flows at the inlet junction and experimental results show a decrease in limiting current. However, for matching inlet velocities or flow rates experimental results show limiting current consistent with predictions that assume no mixing. This result shows a path forward achieving higher power density in the hydrogen bromine laminar flow battery by prioritizing symmetry of the inlet flow conditions as the channel height is decreased.