Search Results (5)

This study investigates a novel pressurized cabin system for open-cathode proton exchange membrane (PEM) fuel cells to enhance energy efficiency and performance. The urgency of this study lies in the increase in the uniformity index (UI) and the decrease in pressure loss, which are crucial parameters of the air supply system. It optimizes the cabin’s 3D geometry using the Taguchi method, achieving a 3.68% increase in UI and a 7.69% reduction in pressure drop. A 1D mathematical model developed for system control demonstrates the pressurized cabin’s superior efficiency compared to conventional air supply systems. Experimental results validate these findings, showing around an 8% reduction in energy consumption and a 9.4% improvement in power output. These results indicate that the novel cabin design offers substantial performance benefits, making it a valuable contribution to energy-efficient fuel cell technology. Full article

The use of polymer electrolyte membrane (PEM) fuel cells as an alternative to internal combustion engines can significantly contribute to the decarbonization of the transport sector, especially for heavy-duty applications. However, degradation is still an issue for this type of component, affecting their durability and performance. In this scenario, a detailed analysis of the anodic and cathodic distributors’ flow-field geometry may help to identify some local stressors that trigger the degradation mechanism, such as local hot spots and reactants not having a uniform distribution. A computational fluid dynamic (CFD) methodology is able to provide a volumetric description of a PEM fuel cell so it can be a useful tool to better understand the physical phenomena that govern the component operations. In this work, the open-source simulation library openFuelCell2 is adopted for a detailed analysis of two different PEM fuel cells characterized by standard distributor geometries, namely a parallel channel geometry and a serpentine configuration. The library, based on the OpenFOAM code, has been extended with a novel implementation accounting for the catalytic activity reduction due to the platinum oxide (PtOx) formation occurring under certain particular conditions. The adopted methodology is firstly validated resorting to experimental data acquired for the two different fuel cell configurations. The analysis highlights that the PtOx formation leads to a reduction in the fuel cell performance reaching up to 60–80% when operating at high voltages. Then, the effect of the distributor geometries on the component performance is investigated by resorting to in-plane and through-plane physical quantity distribution, such as reactant concentration, pressure or velocity fields. While the parallel flow channel configuration shows some diffusion losses under the rib, the serpentine channel geometry configuration can achieve some local performance peaks thanks to the convective flow in the gas diffusion layer (GDL) driven by local pressure gradients. Furthermore, the local enhancement in terms of higher current density under the rib is associated with an effective heat removal due to the high thermal capacity of the bipolar plate, avoiding the generation of local hot spots. Full article

In recent years, there has been a growing interest in utilizing hydrogen as an energy carrier across various transportation sectors, including aerospace applications. This interest stems from its unique capability to yield energy without generating direct carbon dioxide emissions. The conversion process is particularly efficient when performed in a fuel cell system. In aerospace applications, two crucial factors come into play: power-to-weight ratio and the simplicity of the powerplant. In fact, the transient behavior and control of the fuel cell are complicated by the continuously changing values of load and altitude during the flight. To meet these criteria, air-cooled open-cathode Proton Exchange Membrane (PEM) fuel cells should be the preferred choice. However, they have limitations regarding the amount of thermal power they can dissipate. Moreover, the performances of fuel cell systems are significantly worsened at high altitude operating conditions because of the lower air density. Consequently, they find suitability primarily in applications such as Unmanned Aerial Vehicles (UAVs) and Urban Air Mobility (UAM). In the case of ultralight and light aviation, liquid-cooled solutions with a separate circuit for compressed air supply are adopted. The goal of this investigation is to identify the correct simulation approach to predict the behavior of such systems under dynamic conditions, typical of their application in aerial vehicles. To this aim, a detailed review of the scientific literature has been performed, with specific reference to semi-empirical and control-oriented models of the whole fuel cell systems including not only the stack but also the complete balance of plant. Full article

Water management is one issue that must be surpassed to ensure high membrane proton conductivity and adequate reactant transport in the membrane-electrode assembly (MEA) simultaneously. A well-designed water management system is based on a comprehensive understanding of water transport in the inner part of the polymer electrolyte membrane (PEM) fuel cell. In this work, the water transport phenomena in the MEA PEM fuel cell are analyzed by using a mathematical model. The transport of diluted species interface is used to model the transport of water in the ionomer phase in the catalytic layer and the membrane domains. The molecular flux of water is defined using Nernst–Planck equations, including migration and Fickian diffusion using parameters obtained experimentally for diffusivity and mobility based on water drag for a fully humidified membrane. The proposed model 1D model includes anode gas channel, cathode gas channel, anode gas diffusion layer (GDL), cathode GDL, anode catalyst layer, cathode catalyst layer, and proton exchange membrane. Water activity, ionomer conductivity, and output voltage are predicted by changing the humidity on the anode side of the fuel cell. Full article

This paper presents an alternative approach to the flow control of an oxidizer in a proton exchange membrane (PEM) fuel cell system in which pure oxygen is the gas supplied to the cathode channel of the stack. The proposed oxygen flow control is implemented based on information about the current drawn from the fuel cell stack and the voltage variation in the stack. This information and a fuzzy-logic-based control algorithm are used to increase oxygen utilization in a PEM fuel cell system without a recirculation system in relation to the control, in which the oxygen flow rate is determined only in proportion to the current drawn from the stack. To verify the validity of the adopted assumptions, simulation tests of the proposed fuzzy control algorithm were conducted, for which parameters were adopted arbitrarily and determined with help of genetic algorithms. For simulation research, the proposed empirical mathematical model was used, which describes the mathematical relationship between voltage variation in the stack and the stoichiometry of oxygen flow through the cathode of a fuel cell stack. The simulation results confirm that the proposed control method leads to an increase in the oxygen utilization in the system without oxygen recirculation compared to an open system with cathode stoichiometry set to a constant level. Full article