Modeling the Performance of an Integrated Battery and Electrolyzer System

Abstract

Both daily and seasonal fluctuations of renewable power sources will require large-scale energy storage technologies. A recently developed integrated battery and electrolyzer system, called battolyser, fulfills both time-scale requirements. Here, we develop a macroscopic COMSOL Multiphysics model to quantify the energetic efficiency of the battolyser prototype that, for the first time, integrates the functionality of a nickel−iron battery and an alkaline electrolyzer. The current prototype has a rated capacity of 5 Ah, and to develop a larger, enhanced system, it is necessary to characterize the processes occurring within the battolyser and to optimize the individual components of the battolyser. Therefore, there is a need for a model that can provide a fast screening on how the properties of individual components influence the overall energy efficiency of the battolyser prototype. The model is validated using experimental results, and new configurations are compared, and the energy efficiency is optimized for the scale-up of this lab-scale device. Based on the modeling work, we find an optimum electrode thickness for the nickel electrode of 3 and 2.25 mm for the iron electrode with optimal electrode porosities in the range of void fraction of 0.15−0.35. Additionally, electrolyte conductivity and the gap thickness are found to have a small effect on the overall efficiency of the device.

A pseudo-2-dimensional model of the nonlinear impedance response of a nickel-iron battery

“…However, the latter simplifies the analysis by neglecting factors that contribute to the internal impedance of the system [11]. Here, we account for the physicochemical transport properties to numerically simulate the impedance response of a Ni-Fe battery using a known set of base case parameters from Raventos et al's [9] study (table 1), while unknown parameters were calculated or φs assumed from various works of literature on nickel-based systems. Raventos et al [9] developed a 1D model of a nickel-iron battolyser using parameters experimentally obtained from a commercial nickeliron battery.…”

“…The base parameters of a nickel-iron battery were first established to initialize the P2D model. The reported geometric and physicochemical parameters on a nickel-iron battery were adapted from Raventos et al's [9] work. They developed a hybrid system integrates the functionality of a battery and an electrolyzer.…”

A Tale of Nickel-Iron Batteries: Its Resurgence in the Age of Modern Batteries

“…The overall reaction is quite complex as it involves intermediate species that result in different possible products. During the charge-discharge process, the electrolyte's role is not apparent in the overall reaction, as shown in the following reactions: [36]. Copyright 2021, American Chemical Society).…”

“…On the other hand, a 1D multiphysics model was developed by Raventos and coworkers [36] to optimize the individual components of the battolyser. The study focused more on the effects of geometric cell parameters on functionality, as this is often overlooked.…”

“…Schematic illustration of strategies towards Ni-Fe battery improvements (retrieved with permission from Ref. [36]. Copyright 2021, American Chemical Society).…”