Open source cell and stack simulations with computational fluid dynamics (CFD)
One focus is modeling and simulation from the cell component to the stack. In addition to various simulation methods adapted to the task at hand, method and scale coupling is a major challenge that the department has taken on. The complexity of the task combined with the high spatial resolution of the simulations requires a sophisticated computer infrastructure. As part of the Jülich Aachen Research Alliance (JARA), high-performance computers (HPC) from both RWTH Aachen University and Forschungszentrum Jülich are used to generate numerical solutions. An important aspect of this work is that both the simulations and the underlying models are comprehensible in terms of scientific transparency. This is a major, if not the decisive reason why commercial software has become less important for our work. The focus has therefore been on open source software for some years now. This has significantly strengthened the desirable exchange with other research groups.
Detailed 3D models of electrochemical components can be used to identify local behaviors and properties that are very difficult or impossible to measure in experiments. The information obtained from such numerical simulations is an indispensable tool in the research and development of electrochemical converters. As part of the research work, a comprehensive cell model was developed based on the object-oriented open source package OpenFOAM®. The model is able to take into account single-phase and/or two-phase flows that occur in fuel/electrolysis cells with electrochemical reactions, mass and heat transfer. It is based on the continuum assumption and uses the finite volume method. An example is the modeling and simulation of an alkaline water electrolyser.
Alkaline water electrolysis
A detailed 3D simulation of an alkaline water electrolysis cell was performed and validated based on internally collected experimental data. The two main objectives of the work were the prediction of local concentration differences of the potassium hydroxide and the formation of the generated gases, which significantly influence the behavior and performance of the cell. The simulations of the two-phase flow on the cathode and anode side are based on the Euler-Euler approach, where the mass transport, momentum exchange and heat transfer between the gas and liquid phases are described together with the local material concentrations. The electrochemical reactions are characterized by the Butler-Volmer equation, assuming that they take place at electrodes of finite thickness, i.e. within a defined volume. In addition, the properties within the various porous layers, such as tortuosities and permeabilities, are considered to be isotropic. The simulations were carried out on JARA's HPC hardware.
Literature
Shidong Zhang, Steven B. Beale, Uwe Reimer, Martin Andersson, Werner Lehnert
Polymer electrolyte fuel cell modeling – A comparison of two models with different levels of complexity, J. Hydrogen Energy 45 (2020) 19761-19777
https://doi.org/10.1016/j.ijhydene.2020.05.060
S. Zhang, U. Reimer, S.B. Beale, W. Lehnert, D. Stolten
Modeling Polymer Electrolyte Fuel cells: A High Precision Cell Analysis, Applied Energy. Applied Energy 233–234 (2019) 1094–1103
https://doi.org/10.1016/j.apenergy.2018.10.026
M. Andersson, S.B. Beale, M. Espinoza, Z. Wu, W. Lehnert
A review of cell-scale multiphase flow modeling, including water management, in polymer electrolyte fuel cells.. Applied Energy, 180 (2016) 757–778
http://dx.doi.org/10.1016/j.apenergy.2016.08.010