Analysis of Fuel Cells Utilizing Mixed Reality and IoT Achievements

Recent advances in the development of smart glasses enable new interaction patterns in an industrial context. In the field of Mixed Reality, in which the real world and virtual objects fuse, new developments allow for advanced procedures of condition monitoring. Hereby, the smart glasses serve as a mobile display and inspection station. In this work, we focus on the applicability of Mixed Reality to monitor data of the spatially resolved current density distribution of a fuel cell. To be more specific, we implemented an IoT approach based on the Message Queuing Telemetry Transport protocol (MQTT) to enable the aforementioned monitoring. The realized solution, in turn, provides a live monitoring as well as an overview feature

Carbon felt electrodes for redox flow battery: Impact of compression on transport properties

In a flow battery setup, carbon felt materials are compressed to obtain higher performance from the battery. In this work, a commercially available carbon felt material, commonly used as electrodes in Vanadium Redox Flow Battery setups was evaluated for the transport properties (diffusivity, permeability, pressure drop required for maintaining flow, among others) while under seven set levels of compression, using an image analysis coupled with pore network modeling approach. X-ray computed tomography has been used to obtain the microstructure of a commercially available electrode under compressed conditions. An open-source pore network modeling tool, OpenPNM has been used to investigate the transport properties of the porous felt material at each of the set compression levels. The results from the modeling are compared against experimentally obtained electrolyte transport patterns visualized using synchrotron X-ray radiography. The electrical resistance of the carbon felt electrode was measured experimentally using a four-probe method. The compression resulted in a 58% reduction in permeability, and a 25% reduction in single-phase diffusion. This combination of ex-situ characterization of the electrical and fluid transport through the electrodes provides valuable data for modeling flow battery systems, and validating hypothesis from in situ testing

Development of self-supporting MPLs for investigations of water transport in PEM fuel cells

The performance of a polymer electrolyte membrane (PEM) fuel cell has a strong dependence of its water management. The membrane needs humidity to have sufficient ion conductivity. But at high humidity, especially at high current densities, flooding of the electrodes can occur and consequently the available active area begins to decrease. The primary purpose of a micro porous layer (MPL) on a gas diffusion layer (GDL) is the effective wicking of liquid water from the catalyst layer into the diffusion media as well as reducing electrical contact resistance with the adjacent layers. In synchrotron radiography studies the importance of liquid water pathways through the porous structure for the water management is proven. These pathways can be formed by natural cracks in the MPL and the texture of the carbon fibre substrate or by artificial pore paths through the GDL. With artificial paths in a carbon fibre GDL produced by laser perforation an overall performance gain has been obtained. To get additional information about the function of the MPL as an interconnection between the reaction layer and the macro porous carbon fibre substrate a self-supporting MPL was developed. This allows the manufacturing and the following treatments of the MPL independent from the GDL substrate. This MPL consists of a thin nonwoven of synthetics coated on one side with a mixture of carbon and PTFE produced by the dry spraying technology. It is possible to perforate this layer alone and press it with the non-coated side on a commercial GDL without MPL (Sigracet® GDL25BA from SGL). Thus it was feasible to perform experiments for investigation of the influence of artificial pores in the MPL on the water management. As a consequence, the liquid water transport of non-perforated GDL/MPLs is compared to the perforation of both layers as well as to the exclusive perforation of MPL and the GDL, by means of in-situ synchrotron imaging. Further measurements, in particular Ucell(i)-curves up to limiting current densities and electrochemical impedance spectra were done in a 5 cm² fuel cell setup, to obtain a correlation of the global intrinsic properties of the MPL, like through-plane permeability, electrical conductivity or hydrophobicity, with fuel cell performance

Impurities in fuels and air

Despite impressive developments in the technology of proton-exchange membrane fuel cells (PEMFCs), large-scale commercialization still faces issues of low stability and durability that continue to be adversely affected by impurities in the PEMFC system. This article provides a thorough discussion of the impurity and contamination issues that have plagued PEMFC performance. After a brief introduction to the operational principles of the PEMFC, the common sources of impurities in PEMFC systems are discussed, including fuel-side impurities (COx, H2S, and NH3), air-side impurities (NOx, SOx, and COx), and impurities coming from the system components themselves. The effect of contamination and the mechanisms of these impurities on fuel cell operation and performance are presented, followed by a detailed discussion of current strategies for mitigating contamination. Finally, suggestions are provided for future work in PEMFC contamination research

Long Term Testing in Dynamic Mode of HT-PEMFC H3PO4/PBI Celtec-P Based Membrane Electrode Assemblies for micro-CHP Applications

International audienc

Influence of the MPL on PEM fuel cell performance

The gas diffusion layer (GDL) plays a crucial role for PEM fuel cell performance. The main requirements of a GDL are the provision of a gas and water transport as well a significant electrical and thermal conductivity. For the development of PEMFC diffusion media the still unknown influence of the micro porous layer (MPL) on fuel cell performance is a major obstacle. Therefore a self-supporting MPL was developed because it allows basically to measure the properties of the MPL separately from the substrate. This MPL consists of a thin nonwoven of synthetics coated on one side with a mixture of carbon and PTFE produced by the dry spraying technology. For in-situ experiments and some ex-situ measurements these layers are pressed with the non coated side on a commercial GDL without MPL (Sigracet® GDL25BA from SGL). To get a correlation of the global intrinsic properties of the MPL, like through-plane permeability, electrical conductivity or hydrophobicity, to fuel cell performance, Ucell(i)-curves up to limiting current densities and electrochemical impedance spectra are measured in a 5 cm² fuel cell setup. Additionally the function of the MPL structure on water distribution is investigated. Synchrotron radiography studies proved the importance of liquid water pathways through the porous structure for the water management. These pathways can be formed by natural cracks in the MPL and the texture of the carbon fibre substrate or by artificial pore paths through the GDL. With artificial paths in a carbon fiber GDL produced by laser perforation an overall performance gain has been obtained. In the presented work, we performed further experiments to investigate the influence of artificial pores in the MPL on the water management. Therefore the liquid water transport of nonperforated GDL/MPLs is compared to the perforation of both layers as well as to the exclusive perforation of MPL and the GDL, by means of in-situ synchrotron imaging

Synchrotron radiography and tomography of water transport in perforated gas diffusion media

Water transport in gas diffusion media (GDM) is investigated by synchrotron radiography and tomography. It is demonstrated that micro porous layer (MPL) cracks improve the water management in polymer electrolyte membrane (PEM) fuel cells. A further treatment by means of laser perforation is expected to enhance this effect. The radiography analysis reveals that water transport is practically not influenced by perforations applied only to the MPL. In contrast, perforations through the whole GDM (including the MPL) have a strong influence on the overall water transport behavior and are therefore considered for a deeper analysis. Performance measurements show a correlation between the perforation size and the fuel cell power density. An optimum is found for a perforation diameter of 60 µm. Synchrotron tomography analysis reveals that this optimum is due to an improved draining effect on the area around the perforation. Moreover, SEM and EDX analysis show a loss of PTFE on the GDM surface in the vicinity of the perforation due to the laser processing. The tomography images reveal water accumulations in this area that can be explained by the hydrophilic surface

Self-Supporting Microporous Layers (MPLs) for PEM Fuel Cells

The gas diffusion layer (GDL) plays a crucial role for PEM fuel cell performance. The main requirements of a GDL are the provision of gas and water transport as well as significant electrical and thermal conductivity. For the development of PEMFC diffusion media the still unknown influence of the micro porous layer (MPL) on fuel cell performance is a major obstacle. Therefore a self-supporting MPL was developed because it allows basically the measurement of MPL properties separately from the substrate. To get a correlation of the global intrinsic properties of the MPL, like electrical conductivity or hydrophobicity to fuel cell performance, I-V curves up to limiting current densities and electrochemical impedance spectra (EIS) are measured in a 5 cm² fuel cell setup. Additionally synchrotron X-ray radiography studies were performed to compare the influence of different MPLs on liquid water distribution during fuel cell operation

Improved water transport in natural and artificial pore paths of gas diffusion layer in PEM fuel cells

Gas diffusion layer in PEM fuel cells have to fulfil many tasks: high electrical and thermal conductivity, gas and water transport. Different pore sizes and pore geometries in gas diffusion layer influence these parameters. For high current densities, water agglomerations in the porous medium limit the fuel cell performance. The geometry of the carbon fibre substrate and natural cracks in the micro porous layer form preferred water pathways through the porous structure. Synchrotron radiography and tomography studies prove the importance of these pore paths for the overall water distribution. Regarding the flow field design it is found that these water paths cause a draining effect, which transports water from under the land to the gas channel. For further improvement a higher and more regular distribution of cracks is necessary. To achieve this, laser perforation based on and mechanical milling techniques were applied. With this treatment a higher overall performance has been obtained due to the improved water transport. This has been proven by synchrotron imaging