The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Alexander Dyck - One of the best experts on this subject based on the ideXlab platform.
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demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell Operation with natural gas reformate composition
International Journal of Hydrogen Energy, 2017Co-Authors: Javier F Pinar, Maren Rastedt, Nadine Pilinski, Peter Wagner, Alexander DyckAbstract:Abstract Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode Air are presented. A test studying the effect of CO2, H2O and CO in the fuel on fuel cell performance revealed that the presence of CO2 mainly worsens mass transport, H2O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O2 concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H2/Air Operation up to 38.2% with synthetic reformate gas/30% O2 enriched Air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of −21.4 μV/h and was operated with H2/30% O2. The second test was performed with the same kind of MEA but different fuel composition (54% H2, 15% CO2 and 31% H2O) and exhibited a reduction of the degradation rate to −5.5 μV/h. The main reason for this lifetime improvement is H2O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H2 reformate streams also relieves formation of CO from CO2 via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of −22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during Operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H2, 14% CO2, 1% CO and 31% H2O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and Operation at high current densities enhances CO catalyst coverage.
Javier F Pinar - One of the best experts on this subject based on the ideXlab platform.
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demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell Operation with natural gas reformate composition
International Journal of Hydrogen Energy, 2017Co-Authors: Javier F Pinar, Maren Rastedt, Nadine Pilinski, Peter Wagner, Alexander DyckAbstract:Abstract Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode Air are presented. A test studying the effect of CO2, H2O and CO in the fuel on fuel cell performance revealed that the presence of CO2 mainly worsens mass transport, H2O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O2 concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H2/Air Operation up to 38.2% with synthetic reformate gas/30% O2 enriched Air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of −21.4 μV/h and was operated with H2/30% O2. The second test was performed with the same kind of MEA but different fuel composition (54% H2, 15% CO2 and 31% H2O) and exhibited a reduction of the degradation rate to −5.5 μV/h. The main reason for this lifetime improvement is H2O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H2 reformate streams also relieves formation of CO from CO2 via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of −22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during Operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H2, 14% CO2, 1% CO and 31% H2O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and Operation at high current densities enhances CO catalyst coverage.
Peng Xingpu - One of the best experts on this subject based on the ideXlab platform.
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dc brushless motor system for drainage motor and dc brushless motor control method and control apparatus for drainage motor
2015Co-Authors: Wang Chenguang, Wang De-sheng, Peng XingpuAbstract:The invention discloses a DC brushless motor control method and control apparatus for a drainage pump, and a DC brushless motor system for a drainage motor. The DC brushless motor control method for the drainage pump comprises the following steps: after the rotating speed of a DC brushless motor reaches a first predetermined rotating speed, comparing the duty ratio of voltage pulses supplying power to a stator winding of the DC brushless motor with a first critical duty ratio; and under the condition that the duty ratio of the voltage pulses is lower than the first critical duty ratio, determining that the drainage pump enters a half-water half-Air Operation state, and arranging the target rotating speed of the DC brushless motor to be a second predetermined rotating speed, wherein the second predetermined rotating speed is lower than the first predetermined rotating speed. According to the invention, the half-water half-Air state of the drainage pump is identified according to the duty ratio of the voltage pulses supplying power to the stator winding, and through reducing the target rotating speed of the DC brushless motor at the state, half-water half-Air noise is reduced.
Christina Roth - One of the best experts on this subject based on the ideXlab platform.
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Design of a reference electrode for high-temperature PEM fuel cells
Journal of Applied Electrochemistry, 2013Co-Authors: Sebastian Kaserer, Christoph Rakousky, Julia Melke, Christina RothAbstract:In this work, we present the design of an external reference electrode for high-temperature PEM fuel cells. The connection between the reference electrode with one of the fuel cell electrodes is realized by an ionic connector. Using the same material for the ionic connection as for the fuel cell membrane gives us the advantage to reach temperatures above 100 °C without destroying the reference electrode. This configuration allows for the separation of the anode and cathode overpotential in a working fuel cell system. In addition to the electrode overpotentials in normal hydrogen/Air Operation, the influence of CO and CO + H_2O in the anode feed on the fuel cell potentials was investigated. When CO poisons the anode catalyst, not only the anode potential increased, but also the cathode overpotential, due to fewer protons reaching the cathode. By the use of synthetic reformate containing hydrogen, carbon monoxide and water on the anode, fuel cell voltage oscillations were observed at high constant current densities. The reference electrode measurements showed that the fuel cell oscillations were only related to reactions on the anode side influencing the anode overpotential. The cathode potential, in contrast, was only negligibly affected by the oscillations under the applied conditions.
S. G. Yan - One of the best experts on this subject based on the ideXlab platform.
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Dependence of PEM fuel cell performance on catalyst loading
Journal of Power Sources, 2004Co-Authors: Hubert A. Gasteiger, J. E. Panels, S. G. YanAbstract:This study focuses on a determination of the cell voltage losses observed for Pt and PtRu loading reductions in H2/Air and reformate/Air polymer/electrolyte-membrane fuel cells (PEMFC). Experiments with catalyst-coated membranes (CCM) of varying anode and cathode catalyst loadings with H2/O2 and H2/Air demonstrate that the anode catalyst loading in state-of-the-art membrane electrode assemblies (MEAs) operating on pure H2 can be reduced to 0.05 mgPt/cm 2 without significant voltage losses, while the cell voltage losses upon a reduction of the cathode catalyst loading from 0.40 to 0.20 mg Pt/cm2 for optimized MEAs amounts to 10-20mV, consistent with purely kinetic losses due to the oxygen reduction reaction. It is shown that H2/Air Operation with state-of-the-art MEAs very closely approaches the Pt-specific power density (in units of gPt/kW) for large-scale automotive fuel cell applications with pure H2 feed. For reformate/Air Operation, PtRu anode loadings can be reduced to 0.20 mg PtRu/cm2 for reformate containing 100 ppm CO with a 2% Air-bleed. Any further reduction will, however, require either a change in operating conditions (i.e. lower CO concentration or cell temperature ≫80°C) or novel, more CO-tolerant anode catalysts. © 2004 Elsevier B.V. All rights reserved.
