Papers by Keyword: Bipolar Plate

Abstract: Bipolar plates are a key part of fuel cells. The optimal hot press temperature, pressure, and time were determined in this study. The press condition can directly affect the relative density, thereby improving the conductivity and mechanical property. Several carbon black doped samples were also successfully prepared on the basis of the optimized preparation method. Results show that carbon black optimized the conductivity due to the “conduction bridge”. The maximum conductivity and bending strength reached 345 S/cm and 32.5 MPa, respectively. Key words: fuel cells; bipolar plate; graphite; composite materials.

Abstract: Bipolar plate is the key component of proton exchange membrane fuel cells. Due to the factors of rapid and mass production, the stamping process is selected to manufacture the bipolar metal plates. First, the stress-strain curve is performed by universal material testing machine.The stress-strain curve is necessary for bipolar plate stamping simultion. The maximum forging load and effective stress distribution of bipolar plate stamping are determined by finite element analysis. Finally, the effect of the traditional crank stamping on the flatness and section thickness of stainless steel bipolar plate are observed by experiments.

Abstract: Suitable conductive fillers for resins and processing conditions are critical factors for the final properties of composite bipolar plates. This research is focused on the development of expanded graphite/epoxy/aliphatic amine composite as a potential replacement for conventional bipolar plates to meet global standards of Polymer Electrolyte Fuel Cells (PEFCs). The synergistic effects on the electrical conductivity of secondary fillers Carbon Black (CB) and Graphite nanoplatelets (GNP) with Expanded Graphite (EG) were studied in a diglycidyl ether of bisphenol A (DGEBA) epoxy/polyether triamine system. Compositions of secondary filler were varied in proportions of 5, 10, 15 and 20 wt % in a fixed 40 wt % EG / Epoxy resin (w/w) to find the right secondary fillers under direct mixing without solvent. A 10 wt % CB displayed the highest electrical conductivity around 3.05 QUOTE x10^-2 S/cm. For a 60 wt % EG/10 wt % CB composite, the electrical conductivity (in plane) and flexural strength were at about 19 S/cm and 22 MPa, respectively.

Abstract: Proton exchange membrane fuel cell (PEMFC) system is an advanced power system for the future that is sustainable, clean and environmental friendly. The flow channels present in bipolar plates of a PEMFC are responsible for the effective distribution of the reactant gases. Uneven distribution of the reactants can cause variations in current density, temperature, and water content over the area of a PEMFC, thus reducing the performance of PEMFC. By using Serpentine flow field channel, the performance is increased. Two types of serpentine flow field channels are implemented such as curved serpentine flow field channel and normal serpentine flow field channels. The result shows that curved serpentine flow field channel gives better current density and power density, thus increasing the performance of PEMFC.

Abstract: Bipolar plates in Proton Exchange Membrane fuel cells (PEMFC) distribute fuel and oxidant over the reactive sites of the membrane electrode assembly. In a stack, bipolar plates collect current, remove reaction products and manage water. They also separate neighboring cells and keep the oxidant and the fuel from mixing; they provide structural support to the stack. The plates are typically graphite with parallel or serpentine channels. The efficiency of a stack depends on the performance of the bipolar plates, which depends on the material and flow field design. The drawbacks of graphite include weight, fabrication inaccuracy, cost, porosity, and brittleness. Open-cell metal foam is investigated as a flow field/bipolar plate and compared to conventional graphite bipolar plates. The complex internal structure of the foam was modeled using an idealized unit cell based on a body center cube. This cell maintained the actual structural features of the foam. Clones of the idealized cell were virtually connected to each other to form the new bipolar plate. SolidWorks, and Auto-CAD were used to generate the unit cell and the computational domain, which was imported into ANSYS. Meshing of the domain produced than 350,000 elements, and 70,000 nodes. Appropriate boundary and operating conditions for PEMFC were applied, and the PEMFC module within ANSYS was used to obtain the temperature and flow distribution as well as the fuel cell performance. In comparison to conventional bipolar plates, results show that the cell current and voltage densities were improved, and temperature distribution on the membrane was even, and within the allowable limit. As importantly, there was a weight reduction of about 40% as a result of using metal foam as a bipolar plate.

Abstract: Bipolar plates (BPPs) serve multiple roles in polymer electrolyte membrane fuel cells (PEMFCs). When assembled in a stack, they provide the structural backbone of the stack, plus serial electronic connections. They also provide gas (air and fuel) and coolant distribution pathways. Traditionally, bipolar plates have been made of carbon, but these are being replaced in favor of metal bipolar plates made of stamped foils. The Naval Research Laboratory has explored making titanium metal BPPs using 3D printing methods (direct metal laser sintering – DMLS) and superplastic forming, and then using a gold/TiO₂ surface layer for corrosion resistance. The 3D printed plates are made as one piece with the coolant flow internal to the resulting 2-mm thick structure. Their surface roughness requires smoothing prior to coating to increase their cell-to-cell conductivity. We found that 3D printed cells with 22 and 66 cm² active areas are slightly warped, preventing the robust sealing of the stacks. The formed plates are made in separate pieces and then joined. Despite the high temperatures required for superplastic forming, the resulting plates are thin and lightweight, making them highly attractive for lightweight compact PEMFC stacks.

Abstract: This research aims to study the effect of the functionalization of the multiwall carbon nanotubes (MWCNTs) on the mechanical property improvement of phenolic composites for bipolar plate applications in proton exchange membrane fuel cells (PEMFC). The MWCNTs were oxidized by strong acid and silanized by silane coupling agent in order to enhance the interfacial adhesion between the MWCNTs and matrix and were used as reinforcement in the phenolic composites. The silanized MWCNTs was found to improve the mechanical properties of the composites; however, they caused the decrease of electrical conductivity due to the wrapping of the MWCNTs with non-conductive silane molecules. Nevertheless, the conductivity of more than 100 S/cm is maintained to meet the DOE requirement of materials for use as bipolar plates.

Abstract: Optimization of the moulding parameters on the carbon black/graphite/epoxy (CB/G/EP) composite for bipolar plate application using the Taguchi method was carrying out. Moulding parameters of the compression moulding process such as moulding temperature, moulding pressure and moulding time were measured. Analysis of variance (ANOVA) shows that, the most significant moulding parameter is moulding time with percentage contribution of 59.98%.The confirmation experiment using additive model shows that, the electrical conductivity of CB/G/EP composites was 168.50 S/cm. The electrical conductivity of CB/G/EP composite was improved 65.72 % compare with the initial trial. The results show that Taguchi method is an effective approach to obtain the optimal moulding parameters of the CB/G/EP composites.

Abstract: In order to improve the anti-corrosion characteristic of Ag-coated 316SS bipolar plates in PEMFC environment, self-assembled monolayer (SAM) was prepared on its surface by chemical methods. The electrochemical characteristic of modified bipolar plate was also investigated. The results indicated that the SAM was composed of dodecyl thioalcohol. After forming SAM, the bipolar plate’s contact angle increased from 58° to 102°. In addition, its double layer capacitance (Cd) was decreased and charge transfer resistance was increased. The homogeneous SAM, which acted as a protective barrier, inhibited the corrosive ion from corroding. SAM may provide significant protection against corrosion in PEMFC environment.

Abstract: Both assembly force and temperature play an important role in the proton exchange membrane (PEM) fuel cell performance. In this paper, contact pressure between bipolar plate and gas diffusion layer (GDL) in a PEM fuel cell under various assembly forces and at different temperatures was studied numerically. Considering the coupling effects of assembly force and operating temperature on contact pressure, a three-dimensional finite element model of the PEM fuel cell was established and the contact pressure between the GDL and the bipolar plate was studied using commercial code ABAQUS. In order to verify the simulated results, the experimental study was conducted to investigate the contact pressure distribution between the bipolar plate and the GDL. The experimental results are in good agreement with the finite element method (FEM) results. The simulated and experimental results reveal that the contact pressure increased with the increase of assembly force and temperature. It is found that the contact pressure distribution between the bipolar plate and the GDL had the best uniformity under the applied torque of 3.0N·m and at the operating temperature of 80 °C in this work.