Dynamic characteristics of the local current density in proton exchange membrane fuel cells with different operating conditions

Alaefour, Ibrahim; Li, Xianguo

doi:10.1002/er.4202

Cited by 14 publications

(8 citation statements)

References 45 publications

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“…One of the possible reasons is that at lower current density, the pressure at the outlet is higher (assuming the same inlet pressure, 0.3 barg, in all conditions) compared with that at higher current densities, as less hydrogen is consumed at lower current densities. It is shown that higher outlet pressures result in fluctuation in performance as water removal become less effective . Another possible reason for this can be the temperature difference between the anode and cathode inlets.…”

Section: Resultsmentioning

confidence: 99%

“…It is shown that higher outlet pressures result in fluctuation in performance as water removal become less effective. 68 Another possible reason for this can be the temperature difference between the anode and cathode inlets. Anode inlet temperature is kept at room temperature (ie, 20°C), and more hydrogen purge means more local temperature change in the MEA (ie, more hydrogen flow brings the local MEA temperature down) that can promote the liquid water build-up at the anode side.…”

Section: The Effect Of Temperature On Optimum Purge Intervalmentioning

confidence: 99%

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PEMFC purging at low operating temperatures: An experimental approach

et al. 2019

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SUMMARY In this paper, the effect of operating temperature on optimal purge interval for maximum energy efficiency in a proton exchange membrane fuel cell (PEMFC) with dead‐ended anode (DEA) was experimentally investigated. The study was conducted with a focus on challenges associated with operation at temperatures lower than the recommended designed temperature. With DEA, gradual voltage drop happens due to the accumulation of water and impurities such as nitrogen. Hence, periodic purging of the anode side is required to remove excess water and impurities that are accumulated at the anode side over time. Short purge intervals increase hydrogen loss that translates into low fuel utilisation, whereas long purge intervals result in voltage drop due to high water and impurity accumulations. Therefore, an optimal purge strategy should be implemented to maximise the stack energy efficiency. Depending on the operating conditions and loads, there are instances that a fuel cell stack operates at temperatures lower than its recommended designed temperature. Considering the temperature effect on the cell water management, operating temperature is an important factor to consider for optimising the purge strategy in PEMFCs. At lower operating temperatures (ie, below 50°C), more water is formed in liquid form, which makes the optimisation of purge strategy more challenging. For a stack temperature of 40°C, it was observed that with an increase in stack current from 0.25 to 0.45 A cm−2, the optimal purge interval decreases from 90 seconds to around 45 seconds, respectively. Increasing the stack temperature from 40°C to 50°C resulted in an increase in the optimal purge interval to 120 seconds and 90 seconds for stack currents of 0.25 (ie, low current density) and 0.45 A cm−2, respectively. At lower operating temperatures, more frequent purging schedules are needed accordingly to remove the liquid water from the cell. These results indicated that at lower operating temperatures, water accumulation at the anode side becomes more dominant compared with higher operating temperatures.

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Section: Resultsmentioning

confidence: 99%

Section: The Effect Of Temperature On Optimum Purge Intervalmentioning

confidence: 99%

PEMFC purging at low operating temperatures: An experimental approach

et al. 2019

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“…1,2 Proton exchange membrane fuel cells (PEMFCs) have been recognized as one of the most promising power sources for mobile and stationary application, due to its high power density, low operating temperature and zero emissions. [3][4][5] However, there are still many challenges for its widespread commercial application, such as water management. [6][7][8] Proton exchange membrane needs to be fully hydrated to maintain high conductivity.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of water dynamics in a novel wettability gradient anode flow channel for proton exchange membrane fuel cells

Zhang

Yang

et al. 2020

Int J Energy Res

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The effective removal and transport of water in flow channels play an important role in the water management of proton exchange membrane fuel cells (PEMFCs). In this paper, a novel design of anode serpentine flow channel with the wettability gradient wall is discussed and numerically investigated by utilizing the volume-of-fluid (VOF) method. The effects of the contact angle and the wettability gradient of channel walls, as well as hydrogen flow velocity and water droplet size, on the droplet dynamic behavior are studied. The results indicate that compared with the conventional flow channel, the water droplet can be more effectively removed from the turning part in the wettability gradient flow channel. And the water removal ability in the turning part is improved with the increase of the wettability gradient. Moreover, the wettability gradient flow channel can also improve the water removal performance for the cases with different hydrogen flow velocities and water droplet sizes. This study provides ideas for guiding the design of flow channel to effectively enhance anode water management.

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“…Dynamic operating conditions, such as startup and shutdown, could cause performance degradation and dramatic loss in durability . Thus, understanding transient characteristics of the cell during startup/shutdown processes is of great importance to optimizing operation strategy and improving fuel cell durability and stability …”

Section: Introductionmentioning

confidence: 99%

“…[10][11][12][13] Thus, understanding transient characteristics of the cell during startup/ shutdown processes is of great importance to optimizing operation strategy and improving fuel cell durability and stability. 14 During the startup/shutdown processes, the hydrogen/air boundary could form in the flow field, 15,16 and high potential 15,17,18 is locally present on the electrode, causing reverse current in the cell and carbon corrosion, as well as Pt oxidation and dissolution in the catalyst layer. 1,19,20 Thus, the cell durability is significantly reduced, and it is necessary to devote efforts to investigating the reverse current during startup/shutdown processes.…”

Section: Introductionmentioning

confidence: 99%

Dynamic characteristics of internal current during startups/shutdowns in proton exchange membrane fuel cells

2019

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Summary Studying dynamic characteristics of proton exchange membrane fuel cells (PEMFCs) during startups/shutdowns is of great importance to proposing strategies to improve fuel cell performance and durability. In this study, internal current during startup and shutdown processes in PEMFC is investigated, and effects of gas supply/shutoff sequences and backpressure are analyzed by measuring local current densities and the cell voltage in situ. The experimental results show that when reactants were fed/shut off, internal current occurs and variation patterns of local current densities along the flow channel are different. During startups, local current densities in the downstream drop to negative values and internal current can be eliminated when air is first supplied into the cell. While during shutdowns, the results show that negative currents occur in the upstream, and if hydrogen is shut off first, all local current densities remain constant at zero, indicating the effectiveness of gas shutoff sequence in eliminating/mitigating internal current in PEM fuel cells. Further experimental results show that the magnitude of internal current increases with the pressure difference between the anode and the cathode.

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Dynamic characteristics of the local current density in proton exchange membrane fuel cells with different operating conditions

Cited by 14 publications

References 45 publications

PEMFC purging at low operating temperatures: An experimental approach

PEMFC purging at low operating temperatures: An experimental approach

Numerical investigation of water dynamics in a novel wettability gradient anode flow channel for proton exchange membrane fuel cells

Dynamic characteristics of internal current during startups/shutdowns in proton exchange membrane fuel cells

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