Effect of ambient conditions on performance and current distribution of a polymer electrolyte membrane fuel cell (original) (raw)
Related papers
Journal of Power Sources, 2006
For portable applications, the, characteristics of passive air-breathing PEMFCs were investigated by examining effects of cathode open area and relative humidity on the cell performance. Among the single cells with cathode open area from 52 to 94%, the single cell with the open area of 77% exhibited the highest performance. The cell performance was improved with increasing RH of atmosphere from 20 to 100% in the low current region while lowered in high current region. Those results were related with the mass transport of oxygen from the atmosphere to the catalyst layer and the degree of membrane hydration determining the ionic conductivity of the membrane.
Effects of Flow Characteristics in Polymer Electrolyte Membrane Fuel Cell
An experimental and numerical study of polymer electrolyte membrane fuel cell (PEMFC) is presented and compared with the experimental data to investigate the effects of pressure gradient, flow rate, humidification and supplied oxidant type for the practical application. The membrane and electrolyte assembly (MEA) materials are implemented by double-tied catalyst layers. A single-phase two-dimensional steady-state model is is implemented for the numerical analysis. Testing condition is fixed at 60sccm and 70°C in anode and cathode, respectively. It is found that the performance of PEMFC depend highly on the conditions as gas pressure, temperature, thickness, supplied oxidant type (Oxygen/Air) as well as humidification. The results show that the humidification effect enhances the performance more than 20% and the pure oxygen gas as fuel improves current density more than 25% compared to ambient air suppliance as oxidant.
Humidification studies on polymer electrolyte membrane fuel cell
Journal of Power Sources, 2001
Two methods of humidifying the anode gas, namely, external and membrane humidi®cation, for a polymer electrolyte membrane fuel (PEMFC) cell are explained. It is found that the water of solvation of protons decreases with increase in the current density and the electrode area. This is due to insuf®cient external humidi®cation. In a membrane-based humidi®cation, an optimum set of parameters, such as gas¯ow rate, area and type of the membrane, must be chosen to achieve effective humidi®cation. The present study examines the dependence of water pick-up by hydrogen on the temperature, area and thickness of the membrane in membrane humidi®cation. Since the performance of the fuel cell is dependent more on hydrogen humidi®cation than on oxygen humidi®cation, the scope of the work is restricted to the humidi®cation of hydrogen using Na®on 1 membrane. An examination is made on the dependence of water pick-up by hydrogen in membrane humidi®cation on the temperature, area and thickness of the membrane. The dependence of fuel cell performance on membrane humidi®cation and external humidi®cation in the anode gas is also considered. #
Journal of Power Sources, 2011
Although water management at the cathode is known to be critical in miniature polymer electrolyte membrane fuel cells (mPEMFCs), this study shows that control of water transport towards the anode is a determining factor to increase air-breathing mPEMFC performances. An analytical 1D model is developed to capture the water transport and water content profile in the membrane. It shows that drying at the anode and flooding at the cathode can happen simultaneously, mainly due to dominant electro-osmotic drag at low cell temperatures. Experimental results demonstrate that injecting water at the anode, at a rate of 3 times the amount produced at the cathode, increases the cell performances at high current densities. By this method, the limiting current and maximum power densities have been raised by 100% and 30% respectively.
Water transport characteristics of polymer electrolyte membrane fuel cell
International Journal of Hydrogen Energy, 2004
This paper describes the performance of a polymer electrolyte membrane fuel cell (PEMFC) system without humidiÿcation of the reactants which consumes a lot of parasitic power, increases the weight of the PEMFC system and thus adds complexity. Such PEMFC systems are preferable for portable applications. The results indicate that dry gas operation depends on various factors like reactant ow ÿeld design, area of the electrode and equilibration time for the product water. The performance of the fuel cell can be improved by giving some equilibration time for the product water, produced by the electrochemical reactions, to get transported across the membrane to the anode side, thus increasing the conductivity of the membrane. The water transported through the membrane across the cell was investigated by measuring the amount of product water at the anode side which allows humidiÿcation for the anode gas and less condensed water in the uid ow channels of the cathode. ?
Polymer Electrolyte Membrane Fuel Cell
Recent Trends in Fuel Cell Science and Technology, 2007
：Analyses of performance and behavior of the individual PEM fuel cells (PEMFC) under different operating conditions are of importance optimally to design and efficiently to operate the stack. The paper focuses on experimental analyses of a two-cell stack under different operating conditions, which performance and behavior are measured by the voltage of a cell as well as the stack. Experimental parameters include stoichiometric ratio, temperature of the air supplied under different working stack temperatures and loads. Results showed that the cell voltages are dominantly influenced by the temperature of the air supplied among others. In addition, an inherent difference between the first and the second cell voltage exists because of the tolerances of the cell components and the resulting different over-potentials at different equilibrium states. Furthermore, it is shown that the proton conductivity in the membranes conditioned by the humidity in the cathode channel highly affects the voltage differences of the two cells.
Journal of Power Sources, 2013
Polymer electrolyte membrane fuel cells (PEFC) with a porous flow field have been proposed as an alternative to cells with gas flow channels. In this study, the basic characteristics of a PEFC with a porous flow field are identified experimentally. It is shown that stable operation is maintained under conditions at high current density and low stoichiometric ratios of the cathode air, but that operation with low relative humidity gases is difficult in the porous type cell. To clarify the detailed causes of these characteristics, internal phenomena are investigated using a cell specially made for cross-section observations of the cathode porous flow field and temperature distribution measurements on the anode gas diffusion layer (GDL) surface. The direct observations show that the porous type cell is superior in draining the condensed water from the GDL surface, and that hydrophilic properties of the porous material is important for better cell performance at high current densities. The temperature measurements indicate that increases in temperature near the reaction area tends to be larger in the porous type cell than in the channel type cell due to the lower heat removal capability of the porous material, resulting in the unstable operation at relatively low humidities.
Distributed Performance of Polymer Electrolyte Fuel Cells under Low-Humidity Conditions
For reduced system complexity and compactness, it is desirable to operate polymer electrolyte fuel cells (PEFC) with low humidification. In order to more fully understand and optimize performance, there is a need for combined distributed current, species, and impedance data. This paper presents results of a series of experiments at various anode and cathode humidity levels with distributed current, species, and high frequency resistance (HFR) data. This provides much insight into the characteristic operating performance of PEFCs under low-humidity operation. Results show that the degree of water saturation in the anode greatly influences local performance through local anode dryout, even for the thin electrolytes used in this study. A characteristic curve has been developed to predict the qualitative shape of the current profile for a coflow arrangement under fully dry to fully humidified inlet combinations. These results should also be of great interest to those seeking experimenta...
Performance of PEM Fuel Cells without External Humidification of the Reactant Gases
ECS Proceedings Volumes, 1995
Operation of polymer electrolyte fuel cells (PEMFC) without external humidification of the reactant gases is advantageous for the PEMFC system. This is, because this mode of operation eliminates the need of a gas-humidification subsystem which is a burden the fuel pell system with respect to weight, complexity, cost and parasitic power. We investigated the possible range of operating conditions for a PEMFC using dry H /a ir by applying a simple model and it was found, that dry air, passing at the cathode, may be fully internally humidified by the water produced by the electrochemical reaction at temperatures up to 70 *C. The water distribution in the cell operated on dry gases is dominated by the backdiffusion o f product water to the anode. The dominating water back diffusion allows for internally humidifying also the hydrogen and prevents drying out o f the anode. With optimized membrane-electrode-assemblies (MEA), self-humidified cells achieve similar performance as cells withs standard MEA's and humdified gases. The performance of single cells and small stacks is investigated.
Influence of Operating and Electrochemical Parameters on PEMFC Performance: A Simulation Study
Membranes
Proton exchange membrane fuel cell, or polymer electrolyte fuel cell, (PEMFC) has received a significant amount of attention for green energy applications due to its low carbon emission and less other toxic pollution capacity. Herein, we develop a three-dimensional (3D) computational fluid dynamic model. The values of temperature, pressure, relative humidity, exchange coefficient, reference current density (RCD), and porosity values of the gas diffusion layer (GDL) were taken from the published literature. The results demonstrate that the performance of the cell is improved by modifying temperature and operating pressure. Current density is shown to degrade with the rising temperature as explored in this study. The findings show that at 353 K, the current density decreases by 28% compared to that at 323 K. In contrast, studies have shown that totally humidified gas passing through the gas channel results in a 10% higher current density yield, and that an evaluation of a 19% higher R...