Papers by Keyword: PEM Fuel Cell

Abstract: Waste heat recovery in automotive engineering is part of the sustainable energy effort to optimize energy utilization. For vehicles running on hydrogen fuel cells, the potential of heat recovery is perceived to be limited due to the low quality energy generated from the fuel cell stack. It has been established in fuel cell operation that increasing the inlet hydrogen temperature improves the conversion efficiency through higher kinetic reaction rates. A fuel cell power plant for a mini vehicle that will be competing in Shell Eco Marathon Asia 2014 was studied to identify the potential energy recovery limits for an improved power plant design with regenerative hydrogen pre-heater. Using modeling approach for fuel cell power generation and efficiency relationships, the first-order waste energy potential was identified based on test bench studies on the electrical and thermal power relationship of the fuel cell stack performance. The corresponding result is then mapped to a driving cycle to investigate the thermal power generated during the race in both aggressive and passive driving cycle. The energy recovery potential for 4 laps course under aggressive and passive driving cycle are 529 kJ and 501.8 kJ consecutively. The mean thermal powers are 485 W and 410 W respectively which is the reference energy for extended heat exchanger design purposes.

Abstract: The system of PEMFC is nonlinear, people who want to control the nonlinear system directly is hard to come true the goal they want.Characteristic of fuel cells polarization curve is determined by current vary,partial pressure of gasses (hydrogen and oxygen),working temperature,humidity of membrane and so on [. NARMA_L2 controller can transfer the nonlinear system into linear system by concealing the nonlinearities. And Neural networks have been applied successfully in the identification and control of dynamic systems. In this paper, the fuel cell model would be controlled by NAMRA_L2.

Abstract: In the paper the basic information about hydrogen were given. The most important parameters from energetic point of view were described. The efficiency and other work parameters were shown in the form of graphs.

Abstract: It is the objective of this study to present the 3-dimensional comprehensive computational fuel cell dynamics (CFCD) model of a scaled-down single PEM cell featuring a nominal active surface of 0.0004 m² for both conventional and serpentine flow field designs. The performance of these two designs are then analysed and compared keeping both anode and cathode inlet gases fully humidified. Then the parallel flow field was modelled under different inlet gas relative humidities (RH_a/RH_c) representing saturated, moderate, and dry conditions to observe the gain in cell performance. The higher pressure drop of the serpentine flow-field was demonstrated and the magnitude of which might seem to be negligible in the range of 100 Pascal. The simulation results show that a parallel flow-field design with appropriate humidity level can compete with the serpentine counterpart and gives considerably lower pressure drop across the cell. With a grid-independency analysis, it is suggested for the computational power available, the percentage error of important variables (species concentration and averaged current density) between the reference and finer mesh is negligible (< 3%) and the solution time is considerably less.

Abstract: The focus of this paper is to develop and test a modified design of the conventional parallel flow channel configuration in a proton exchange membrane (PEM) fuel cell. One of the main objectives in designing flow channel configurations is to achieve a uniform distribution of reactants across the catalyst layer of the membrane electrode assembly of the fuel cell. Uniform reactant distribution promotes an even current density distribution, and enhances power output and overall cell performance. A simple method for visualizing the flow distribution is used to study the flow distribution in the flow channels of a PEM fuel cell. In the experiment the principle of dimensional analysis and similitude was employed to study gas distribution by using water instead of gas. The results demonstrate that providing storage volumes before the channels creates a better flow distribution. The results also reveal that channels with the shortest distance between inlet and outlet manifold are reactant rich and are filled prior to the channels with longer such distances.

Abstract: This paper evaluate previous experimental studies on sub-freezing start up of proton exchange membrane (PEM) fuel cell system, and identify issues for further investigation. In a successful cold start, product water from electrochemical reaction in the cathode must be removed from the cell before it turns into ice and causing voltage drop and shutdown also leads to permanent damage to fuel cell components. Successful single PEM fuel cell start up was achieved from temperature as low as-30°C. Some researchers found that cold start of a 30 W stack from-20°C was possible only with aid of external energy. Successful self-start up a 2 kW stack from temperature-5°C was reported but the time taken was unacceptably long and attempts to start up the stack at lower temperatures were failed. Based on the current state of research, further research is necessary to fully understand the operation and mechanism of PEM fuel cell cold start.

Abstract: Among several hydrogen storage methods for application in fuel cells, on-board hydrogen generation using sodium borohydride (NaBH₄; a chemical hydride) for application in proton exchange membrane (PEM) fuel cells can be considered as a low-weight method for portable applications. In this paper, an integrated continuous-flow system for on-demand hydrogen generation from the hydrolysis reaction of the NaBH₄ solution in the presence of a low-cost catalyst is proposed. By using the prepared non-noble Co(NO₃)₂ on porous alpha-alumina support, as catalyst, the cost of the catalyst has cut down considerably. Up to 15 SLPM high-purity hydrogen gas is expected to be generated by this system to supply to a 1 kW-scale proton exchange membrane (PEM) fuel cell stack (H₂-air, 40% efficiency).

Abstract: The performance of proton exchange membrane fuel cell is greatly influenced by the presence, distribution and transport of liquid water in the gas diffusion layer (GDL). In this study, air-water flow in a 3D GDL microstructure along the in-plane direction is studied numerically by using the volume of fluid (VOF) method. The GDL microstructure is considered initially filled with water, air flows into the structure under the driving force of a set pressure drop and the flow is supported by the capillary pressure due to the hydrophobic nature of the GDL structure. It is found that water removal can be accelerated by improving pressure drop. Pressure drop has little influence on the state-steady water volume fraction when the pressure drop is over a critical value.

Abstract: Water management plays a significant role in enhancing performance of proton exchange membrane fuel cell (PEMFC). Successful water management requires effective removal of liquid water produced by electrochemical reactions. Therefore, it is a critical challenge to understand liquid water movements in flow channels. In the present study, a three-dimensional unsteady two-phase model for the cathode side of PEMFC consisting of gas channel (GC), gas diffusion layer (GDL) and catalyst layer (CL) is developed using FLUENT software with a volume-of-fluid (VOF) method and user-defined-function (UDF). When fuel cells are assembled, the cross sections of gas channel change, resulting in different water droplet movements. The effects of GDL deformations on water droplet movements are discussed.

Abstract: Investigation of conductive polymer composites have been carried out using polypropylene (PP) and polyphenylene sulfonate (PPS) for matrix compound and graphite, carbon black and multi walled carbon nanotubes (MWCNT) for fillers. The comparison of these matrix materials with respect to the resulting electrical conductivity were investigated in depth. The effect of quantity of nanotubes and their dispersion on electrical conductivity and formability was also investigated. It has been found that PPS composites show much higher conductivity, however the high temperature needed for forming, and high viscosity in case of high filler content (50 wt% <) make the processing difficult, therefore the injection molding of the resulting material is currently not possible. Furthermore in contradiction to the literature the addition of MWCNT did not raise the conductivity significantly, therefore the focus have been kept on filler content instead.