Fuel Cell Stack Assembly Research Articles

Effects of Inhomogeneous Gas Diffusion Layer Properties on the Transportation Phenomenon and Performances of Proton-Exchange Membrane Fuel Cells.

The encapsulation of the proton-exchange membrane fuel cell (PEMFC) is an essential step of fuel cell stack assembly. The selection of the assembly pressure is very important to the stack performance and life. Based on that, this paper presents a method to describe the internal physical deformation of the gas diffusion layer (GDL) after inhomogeneous pressure by using user-defined functions (UDFs). The results show that the transmission difference caused by the nonuniform GDL deformation can be clearly seen by the UDFs method, and there is an obvious transition of GDL at the interface of the channel and the rib. A three-dimensional single-channel PEMFC model is established, and an optimal assembly pressure range is obtained, between 1.5 and 2.0 MPa. The maximum thermal stress inside the cell occurs in the middle of the membrane electrode assembly and decreases as the assembly pressure increases. Furthermore, the influence of rib-channel ratios is discussed. Compared to the fuel cells with ratios of 2:1, 2:3, and 1:2, the one with 1:1 exhibits the maximum current density and the highest power density.

Development of an Adaptive Human-centered Work Station for Fuel Cell Stack Assembly

Facing the challenges of modern production, such as increased product variability and individuality, assembly systems must strive for maximum flexibility. Consequently, despite the continuous advancements in automation, the human workforce retains its crucial role in industrial assembly due to its exceptional adaptability and learning capabilities. However, the industry is confronted with the additional challenge of addressing a shortage of skilled workers, managing ongoing demographic changes, and handling an increasingly heterogenous workforce in terms of age, skills, and experience. As a result, there is a growing emphasis on the efficient and ergonomic use of the human workforce. In this context, the concept of human-centered production systems has emerged as an important approach.The objective of this paper is to propose a general concept for the implementation of a human-centered assembly system that can adapt to different human characteristics in terms of anthropometry, functional capabilities, knowledge, and personal needs during the assembly process. This in-process adaptation is based on the tracking of human movements and actions during the assembly process using LiDAR and camera technology. The collected data is utilized to feed a recommender system that serves to suggest possible configuration optimizations in the assembly system dimensions of Working height, Range of vision, gripping area, and handedness, Lighting and Use of information and assistance systems, encompassing a laser projector, spatial augmented reality facilitated by a dynamic beamer, and intelligent tools.Subsequently this general approach is applied to the development of a work station designed for the assembly of fuel cell stack components.

Development of novel single fuel cell based on composite polar plates for highly efficient power generation

In proton exchange membrane fuel cells (PEMFCs), bipolar plate (BPP) and membrane electrode assembly (MEA) are arranged alternately to construct a fuel cell stack for power generation. This construction method may affect the power generation performance of fuel cell stack or even damage the MEA components. To improve the fuel cell stack's assembly efficiency, we propose a novel single fuel cell that consists of two composite polar plates and a MEA, the composite polar plate is formed by a nylon frame and a titanium thin sheet with microchannels. The structural design of the single cell and its working principles are firstly presented, and followed by the fabrication of the single fuel cell. A three dimensional (3D) numerical model is developed to investigate the internal electrochemical reaction behaviors of the single fuel cell. Then, experimental tests are conducted to test its electrochemical performance for power generation. The obtained results showed that the open circuit voltage can reach 0.93 V and energy density is approximately 813.83 mW/cm3, indicating our developed single fuel cell had a high energy utilization efficiency for power generation. Therefore, our developed single fuel cell has the potential to power unmanned aerial vehicles (UAVs), robotics, and new energy vehicles.

Static Stress Analysis of Membrane Electrode Assembly (MEA) and Gasket in Proton Exchange Membrane Fuel Cell Stack Assembly Pressure

The proton exchange membrane fuel cell (PEMFC) system was an electrochemical device that generates electricity through the reaction of hydrogen and oxygen without combustion. Proton Exchange Membrane (PEM) stacks typically consisted of components combined into one unit and equipped with suitable clamping torque. This was to prevent reactant gas leakage and minimize the contact resistance between the gas diffusion medium and the bipolar plate. The combined components consisted of a bipolar plate with a flow field, current collector, membrane electrode assembly (MEA), endplate, and gasket. PEMFC performance was measured concerning its power output, which depends on temperature and the operating pressure. Various efforts had been made to determine the optimal compaction pressure and its distribution through simulations and experiments. Therefore, this research analyzed the static stress of membrane electrode assembly (MEA) and gasket in PEMFC stack assembly pressure. The components’ geometric dimensions and mechanical properties, such as endplates, current collectors, bipolar plates, MEAs, and gaskets, were combined for electricity. Pressure-sensitive film (Fuji measure film prescale) was also used to visualize contact pressure distribution between the MEA and the bipolar plate. The result showed that the color variation of the pressure film indicates the exact distribution of pressure entering the stacking design and the contact image. In conclusion, the detailed contact pressure distribution was an important influence on heat transfer processes and local electrochemical reactions in cell stacks.

Elucidating non-uniform assembling effect in large-scale PEM fuel cell by coupling mechanics and performance models

The assembly of proton exchange membrane (PEM) fuel cell has a significant influence on contact pressure of BP and GDL, which affects key parameters of GDL including contact resistance, porosity, and permeability. In this study, a large-scale finite element method (FEM) PEM fuel cell model is developed considering realistic assembly, which is assembled by 14 bolts. The contact pressure at the interface of GDL and BP is converted into non-uniform contact resistance incorporated into a self-developed “3D + 1D” full PEM fuel cell multi-phase model with the active area of 108 cm2. The “3D + 1D” model simplifies part of components along through-plane direction into 1D model to improve calculation efficiency and stability. The results show that the performance reduces slightly when considering non-uniform contact resistance compared with that considering uniform contact resistance. The uniformity of current density and temperature distributions reduces evidently when considering non-uniform contact resistance affecting the performance and durability, which demonstrates the necessity of treatment of non-uniform contact resistance. Furthermore, the effects of porosity and permeability of deformed GDL under different preloading torques on performance are investigated. It is found that the contact resistance reduces first and then flats as the preloading torques increase, which results in the same trend of electronic ohmic loss, while the concentration loss nearly linearly increases. The simulation shows that the PEM fuel cell shows the best performance when the preloading torque is 3 Nm. This study provides some meaningful guidance for PEM fuel cell stack assembly.

Experimental Characterization of Anisotropic Mechanical and Thermal Properties of Gas Diffusion Layers

Gas diffusion layer (GDL) is a vital component in proton exchange membrane fuel cells (PEMFC) due its main functions to conduct electrons and heat between the adjacent fuel cell components, provide preferential pathways for product water removal and to provide uniform reactant gas flow distribution to the electrode surface. Because of the anisotropic GDL microstructure, the transport properties vary in the through-plane and in-plane direction. Furthermore, during fuel cell stack assembly pressures exerted on the flowfield land compress the GDL under land cause changes of the GDL microstructure. While moderate compression increases GDL thermal conductivity due to increased fiber-fiber contacts, excessive compression may impede diffusive and liquid water transport due to loss of GDL pore volume. Detailed knowledge of how thermal conductivity is affected by the anisotropic nature of gas diffusion layers under compression is imperative in order to provide a better understanding on how thermal gradients influence two-phase transport during PEMFC operation. Previous research efforts have focused on steady-state methods for measuring effective through-plane GDL thermal conductivity [1][2][3][4] and effective in-plane GDL thermal conductivity [5][6] but to the best of our knowledge no studies have been conducted to measure effective in-plane GDL thermal conductivity for a variety of different GDL types under compression.This study attempts to fill that gap by using specially designed in-house tools to characterize the influence of GDL anisotropy on effective thermal conductivity as a function compression for different GDL types. Furthermore, a comprehensive ex-situ mechanical study is conducted to characterize the compliance matrix for different GDL types. Early results indicate a highly non-linear compressive behaviour in the GDL through-plane direction with large variations for the different GDL types. Moreover, the flexural modulus is found to be highly anisotropic where stiffness in the GDL machine direction (MD) is consistently larger compared to stiffness in GDL cross machine direction (CMD). This work will provide a foundation for a numerical study to couple an anisotropic GDL structural model with a non-isothermal two-phase model to investigate the effects of inhomogenous compression on two-phase transport. Keywords: GDL, PEMFC, ex-situ, anisotropy, modulus, microstructure, mechanical, compression, characterization, MD, CMD, through-plane, in-plane, thermal conductivity[1] G. Karimi, X. Li, P. Teertstra, Electrochim. Acta (2010).[2] R. Bock, A.D. Shum, X. Xiao, H. Karoliussen, F. Seland, I. V. Zenyuk, O.S. Burheim, J. Electrochem. Soc. 165 (2018) F514–F525.[3] G. Unsworth, N. Zamel, X. Li, Int. J. Hydrogen Energy (2012).[4] E. Sadeghi, N. Djilali, M. Bahrami, J. Power Sources (2011).[5] E. Sadeghi, N. Djilali, M. Bahrami, J. Power Sources (2011).[6] N. Alhazmi, D.B. Ingham, M.S. Ismail, K.J. Hughes, L. Ma, M. Pourkashanian, Int. J. Hydrogen Energy (2013).

An equivalent mechanical model investigating endplates deflection for PEM fuel cell stack

The aim of this study is to obtain the deflection curve equations of endplates with one to five clamping belts which allows investigating endplates deflection for uniform contact pressure distribution. Based on an equivalent mechanical model for a large fuel cell stack, the effects of the thicknesses of endplates, numbers, and positions of clamping belts are discussed, and the optimal thickness of endplate with different clamping belts is obtained, and moreover the optimal position of intermediate and outer clamping belts on the endplates. Finally, a three-dimensional finite element analysis (FEA) of a fuel cell stack clamping with steel belts and nonlinear contact elements is compared to what the equivalent mechanical beam model predicts. The result of this study shows that the equivalent mechanical model gives good prediction accuracy for the deflection behavior of endplates and the clamping force of the fuel cell stack, which is effective and helpful for the design of a large fuel cell stack assembly.

Genetic algorithm for the optimization of vision acquisition for on-the-fly position measurement of individual layers in fuel cell stack assembly

Polymer electrolyte membrane (PEM) fuel cells consist of hundreds of stacked individual layers. As misplacement can lead to product-malfunctions the positioning accuracy plays a crucial role during assembly. Thus, to increase accuracy and to lower the cycle time, this paper presents a camera-integrated gripper for single layer handling of fuel cell components. The overlapping of suction holes within a gripper system is used for position measurement of fuel cell layers. The hole pattern is optimized applying a genetic algorithm to precisely measure the position of individual layers.

An Analytical Model for Contact Pressure Prediction Considering Dimensional Error of Stamped Bipolar Plate and Gas Diffusion Layer in Proton Exchange Membrane Fuel Cell Stack Assembly

Contact pressure distribution between bipolar plate (BPP) and gas diffusion layer (GDL) has significant impact on performance and life time of proton exchange membrane (PEM) fuel cell. Most current studies for contact pressure prediction are based on finite-element analysis (FEA), requiring huge computation for the whole fuel cell assembly. Comparatively speaking, the more generalized and well-developed analytical methods are deficient in this field. The objective of this study is to propose a full-scale continuous equivalent model to predict GDL contact pressure effectively in the PEM fuel cell. Using the model, the nonuniform pressure distribution resulted from dimensional errors of metallic BPP and GDL could be obtained. First, a parameterized theoretical model of BPP/GDL assembly is established based on equivalent stiffness analysis of components, and definition methods of dimensional errors are proposed according to actual measurements and Monte Carlo simulation (MCS). Then, experiments are carried out to obtain the actual GDL contact pressure and the model results show good agreement with experimental results. At last, effects of dimensional errors are investigated. Acceptable assembly pressure for a given fuel cell is suggested based on the model. This model is helpful to understand the effect of the dimensional errors, and it also could be adopted to guide the manufacturing of BPP, GDL, and the assembling of PEM fuel cell.

Sobol's sensitivity analysis for a fuel cell stack assembly model with the aid of structure-selection techniques

This paper presents a novel method for identifying the main parameters affecting the stress distribution of the components used in assembly modeling of proton exchange membrane fuel cell (PEMFC) stack. This method is a combination of an approximation model and Sobol's method, which allows a fast global sensitivity analysis for a set of uncertain parameters using only a limited number of calculations. Seven major parameters, i.e., Young's modulus of the end plate and the membrane electrode assembly (MEA), the contact stiffness between the MEA and bipolar plate (BPP), the X and Y positions of the bolts, the pressure of each bolt, and the thickness of the end plate, are investigated regarding their effect on four metrics, i.e., the maximum stresses of the MEA, BPP, and end plate, and the stress distribution percentage of the MEA. The analysis reveals the individual effects of each parameter and its interactions with the other parameters. The results show that the X position of a bolt has a major influence on the maximum stresses of the BPP and end plate, whereas the thickness of the end plate has the strongest effect on both the maximum stress and the stress distribution percentage of the MEA.

The development and performance analysis of all-China-made PEM fuel cell unit and 1 kW level fuel cell stack

The all-China-made proton exchange membrane fuel cell units were created and one fuel cell stack was assembled, with all domestic material such like Chinese proton exchange membrane, Chinese catalyst, Chinese carbon paper and Chinese graphite plate, on the basis of heat shaping CCM technology and modularized fuel cell stack assembly technology. The fuel cell unit was tested and optimized. The electricity generating test and other related experiments were conducted. It’s showed that the fuel cell unit’s performance was stable and its power density could reach 550 mW/cm 2; the fuel cell stack’s operating power had reached 200 mW/cm 2 with voltage uniformly distributed. The stack was stable and showed no obvious decrease in performance after 1800 h continuous operation. Discharged water analysis showed the all-China-made fuel cell stack’s materials had good chemical stability. This new type of fuel cell stack is much cheaper in production cost, compared to the same level import fuel cell stack.

Fuel Cell ASAP: Two Iterations of an Automated Stack Assembly Process and Ramifications for Fuel Cell Design-for-Manufacture Considerations

Polymer-electrode membrane fuel cell technology, a low-emission power source receiving much attention for its efficiency, will need to progress from low-volume production to high-volume within the course of the next decade. To successfully achieve this transition, significant research progress has already been made toward developing a fully functional fuel cell automatic stack assembly robotic station. Lessons can be drawn from this research with regards to design-for-manufacture (DFM) and design-for-assembly (DFA) considerations of fuel cells; however, more work still remains to be done. This document outlines both iterations of the robotic fuel cell assembly stations, other work to date, DFM and DFA lessons learned, and the anticipated future progression of automatic fuel cell stack assembly stations. Two individual robotic fuel cell assembly stations were constructed, including custom-built end effectors and part feeders. The second station incorporated numerous improvements, including overlapping work envelopes, elimination of a shuttle cart, software synchronization, fewer axes, and a better end effector. Consequentially, the second workcell achieved a fourfold improvement in cycle time over the previous iteration. Future improvements will focus in part upon improving the reliability of the overall system. As the stack assembly workcell continues to improve, research will focus upon the ramifications and interplay of tolerances, stack failure modes, sealing, reliability, and the potential for component redesign specifically to optimize fuel cell manufacturing throughput.

Analyses of the fuel cell stack assembly pressure

A proper stacking design and cell assembly are important to the performance of fuel cells. The cell assembly will affect the contact behavior of the bipolar plates with the membrane electrode assembly (MEA). Not enough assembly pressure may lead to leakage of fuels, high contact resistance and malfunctioning of the cells. Too much pressure, on the other hand, may result in damage to the gas diffusion layer and/or MEA. The stacking design may affect the pressure distribution within the fuel cell stack and thus the interfacial contact resistance. Uneven distribution of the contact pressure will result in hot spots which may have a detrimental effect on fuel cell life. In this study, finite element analysis (FEA) procedures were established for a PEM single cell with point stack assembly method. The mechanical properties and geometrical dimensions of all the fuel cell components, such as bipolar plates, membrane, gas diffusion layer and end plates were collected for accurate simulation. From the FEAs, the compliance as well as the pressure distribution of the single cell was calculated. In order to verify the results of the analysis, experimental tests, with a pressure film inserted between the bipolar plates and the MEA, were conducted to establish the actual pressure distribution. Color variations of the pressure film could be calibrated to obtain pressure distribution. Compliance of the gas diffusion layer was also measured. The analysis procedures for the fuel cell stacking assembly were established by comparing the simulation results with those of the experimental data at various levels of assembly pressures. They can help determine the proper stacking parameters such as stacking design, bipolar plate thickness, sealing size and assembly pressure, and are important in obtaining a consistent fuel cell performance.

Fuel cell transport frame

The present invention discloses a transport frame for transporting and maintaining a fuel cell stack assembly in a fixed position. The fuel cell stack asembly which is under compression by a top and bottom plate held together by tie rods positioned at the corners of each plate. The top and bottom plates are then mounted to a rigid frame for transporting the fuel cell. The tie rods being attached to mounts in the base plate of the rigid frame and an insulated attachment between the top plate of the fuel cell stack frame and the rigid frame is made. The fuel cell stack assembly being electrically insulated from the rigid frame.