MechSE Associate Professor Kyle Smith and doctoral student Md Abdul Hamid recently published an article in the Journal of Power Sources.
Smith and Chen, researchers from the University of California, Riverside, have introduced a groundbreaking theory that challenges conventional approaches to understanding mass transport in flow batteries. Their study titled “A bottom-up, multi-scale theory for transient mass transport of redox-active species through porous electrodes beyond the pseudo-steady limit” proposes a new means of comprehending convection inside reactive porous media. The researchers introduce frequency-dependent transfer functions to upscale mass transport occurring in microscopic pores, shedding new light on familiar mass and heat transfer principles.
What sets this research apart is the introduction of transfer functions as mathematical tools in the context of mass transport in flow batteries. Transfer functions are usually utilized in control theory, but this study is the first to apply them in this context or derive them in this manner. Smith and Chen formulated their theory before the COVID-19 pandemic, making their publication a long-awaited success.
The researchers introduce a spectral Sherwood number, a type of transfer function that extends the film law of mass transfer to transient conditions. Similarly, a spectral Nusselt number extends Newton’s law of cooling for convection heat transfer. The two also formulated the embedding of transfer functions into an up-scaled model to obtain the time-domain response of flow batteries.
What’s truly unique about this research is that it extends non-dimensional parameters from their conventional application in time-invariant, or steady-state, settings to transient settings in a way that accounts for changes in the microscopic dynamics that result from transient cycling. This discovery represents a significant shift in understanding mass transport in flow batteries, which could have major implications for the power capacity of flow batteries used in electricity production from renewable energy sources.
Smith and Chen’s research on the understanding of mass transport in flow batteries through porous electrodes has broader implications for the chemical, civil, and petroleum engineering communities. While these communities have explored approaches to understanding mass transfer in other porous materials, these approaches were not previously applied to electrochemical systems. Smith points out that their work introduces a relatively straightforward approach to modeling these effects, starting from the detailed microstructure and up-scaling its effects for use in macroscopic scale models.
This approach is unique in that it bridges the gap between the microscopic and macroscopic scales, allowing for a more accurate and comprehensive understanding of mass transport. The implications of this research extend beyond flow batteries, as this method could be applied to other electrochemical systems and porous materials. This research has the potential to revolutionize the field of electrochemistry by introducing a new perspective on mass transport, opening up new avenues for innovation and discovery.
The theory developed by Smith and Chen has significant implications for the design and operation of flow batteries. By introducing frequency-dependent transfer functions, their theory demonstrates that flow batteries can operate at higher than their limiting current for short periods of time. This finding suggests that cheaper and lighter batteries can be designed to withstand cycling conditions without compromising performance. Hamid notes that the theory not only provides a better modeling approach for accurate prediction of existing flow battery rate capabilities but also offers guidelines for more efficient designs, operating schemes, and materials.
Smith and Hamid are keen to expand the scope of their research beyond flow batteries, and they plan to apply their theory to various energy and environmental devices that utilize electrochemistry. By doing so, they hope to gain a better understanding of the role of mass transport in other porous materials and to identify potential areas for innovation and development. Additionally, the researchers plan to extend their theory beyond the range of conditions demonstrated in their publication, exploring the full range of transient conditions that affect mass transport in porous electrodes.
The team’s research has the potential to transform the field of electrochemistry by providing a new perspective on mass transport that accounts for changes in microscopic dynamics resulting from transient cycling. Their approach bridges the gap between microscopic and macroscopic scales, offering a more comprehensive understanding of mass transport in porous materials. As such, this research opens up new avenues for innovation and discovery, with implications for the development of more efficient and cost-effective electrochemical devices.
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