Image by: Michael Fousert
Publish Date: 15.09.2022
Category: Our contribution to sustainable development goals
Sustainable development goals: 7 Affordable and clean energy, 9 Industry, innovation and infrastructure, 13 Climate action (Indicators)
Hydrogen proton exchange membrane fuel cells are devices that enble direct conversion of chemically bound energy that is released during the reaction between hydrogen and oxygen into electrical energy with the water being the only side product of the process. Due to nontoxicity of the emissions, hydrogen fuel cells are considered to be one of the key technologies for achieving goals set in the scope of European Green Deal, especially for long haul and heavy-duty applications. Additionally, they also present an integral part of grid stabilization systems in power grids of the future.
Ensuring adequate hydration of a low-temperature fuel cell with a proton exchange membrane represents a scientific and technical challenge, mainly due to the low operating temperatures (e.g. 60-80°C) at which water is present in both the gaseous and liquid phases. In the latter, it fills the space intended for the transport of gases and thus limits the gas transport, which leads to a decrease in performance of the fuel cell and effects the degradation mechanisms via changed concentrations. Due to the convoluted causal chains of phenomena, low-temperature proton exchange membrane fuel cells are characterized by a highly nonlinear response. Optimizing performance in terms of performance and longevity is therefore extremely challenging. This reasoning calls for a precise online monitoring and control solutions such as coupled virtual observers taking into consideration also liquid water dynamics, which can cause flooding of the PEMFC and consequential drop in the performance. Modelling of the latter proves to be especially challenging due to varying retention and removal rates of liquid and gaseous water depending on the operating conditions thus representing a longstanding knowledge gap on the system level modeling, where calculations need to be performed much faster than in real time at a high frequency of data exchange.
To fill this gap, researchers of Laboratory of internal combustion engines and electromobility (LICeM), Faculty of Mechanical Engineering , University of Ljubljana have in collaboration with Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture in Split (FESB), University of Split developed and validated the Real-time capable transient model of liquid water dynamics in proton exchange membrane Fuel Cells, that can be utilized in the aforementioned advanced control methodologies such as virtual observers and hardware-in-the-loop as well as digital twin applications. The modelling approach is based on the 1D+1D system level mechanistically based PEMFC model composing two-phase flow water sub-model, which enables consistent system level treatment of liquid water dynamics in all seven most influential regions of the PEMFC (see Figure below), namely membrane, anode, and cathode channels, GDLs, and catalyst layers, while exhibiting real-time readiness with real-time factor of 0.0449 at the time step of 1ms or frequency of the data exchange of 1 kHz.
The model is a significant upgrade of the previously published thermodynamically consistent electrochemical model and was developed in the scope of the CDL for Innovative Control and Monitoring of Automotive Powertrain Systems. The results of the basic thermodynamically consistent electrochemical model and transient model of liquid water dynamics in proton exchange membrane fuel cells were published in a renowned journal - Journal of Power Sources (IF: 9.127). The importance and relevance of the research carried out in the field of fuel cell degradation modelling and the efficiency of the transfer of research results into advanced technological products is further confirmed by the integration of the developed modelling framework into the commercial simulation platform of one of the leading companies and its subsequent use in the development process of fuel cell-based systems at leading automotive manufacturers.
Image 1: Schematic representation of the seven regions modelling approach.