Modeling and simulation of 3D printed vanadium redox flow battery

Miniaturized redox flow batteries have seen interest in electronic applications because of their potential to simultaneously deliver electric power and remove heat. For these applications, the flow battery has to be constructed on a side of a computer chip, with components such as flow channels, manifolds, supply tubes, electrodes, membranes and current collectors. There are efforts underway to optimize the design of these components for different objectives such as maximum power density or maximum efficiency. Due to space constraints, design rules employed for classical redox flow batteries are only of limited use in microfluidic systems. Since experimentation with micro-scale components is especially expensive and time-consuming, there is a need to develop computational tools to understand trade-offs in the design and operation of these flow batteries. Computational fluid dynamics study of redox flow batteries using vii COMSOL Multiphysics software has been done. PEM fuel cells are very similar to flow batteries. The high temperature PEM fuel cell was studied first to understand the electrochemistry involved in such systems. The anolyte and catholyte fluid flows are modeled using Navier-Stokes equations of mass and momentum conservation. Species diffusion through porous electrodes is modeled using species-dependent diffusion coefficients, which are calculated based on the fluid state and the electrode geometry. The electrochemical reactions are modeled using the Butler-Volmer equation with a pre-defined exchange current density. The species concentrations, velocities and pressures are solved in the simulation. We found that the flow channel geometry and manifold design has an important effect on the flow distribution. It also affects the pressure drop, thereby affecting the pumping power required to keep the battery operational. The effect of different operating conditions such as electrolyte flow rate and state of charge has been simulated and it has been found that these parameters has significant effect on flow battery performance. Based on these findings, we make observations regarding cell design and operation. We expect that these simulations, once validated with experiments, lead to a better understanding of the trade-offs involved in the design and operation of miniature redox flow batteries for electronic applications.
by Brijesh Kumar
M.Tech.