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



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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.