Performance analysis of HT-PEFC stacks

Lüke, Lukas; Janssen, Hans-Karl; Kvesić, Mirko; Lehnert, Werner; Stolten, Detlef

doi:10.1016/j.ijhydene.2012.02.190

Cited by 47 publications

(18 citation statements)

References 51 publications

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“…This would be enhanced by the fact that local current density is not distributed evenly at higher total current densities. [128][129][130] Degradation can occur if the local temperature exceeds a critical value. The model itself does not resolve local effects, but the critical temperature can be roughly translated into a critical value of the overall heat flux.…”

Section: Journal Of the Electrochemical Society 162 (1) F153-f164 (2mentioning

confidence: 99%

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Reimer

Schumacher

Lehnert

2014

J. Electrochem. Soc.

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Accelerated stress tests are commonly applied in order to obtain a prediction of fuel cell life time within a short testing period. The stress test in this work considers a fuel cell which is constantly under load with frequent periods of very high current. Four different cells were operated each with a specific load profile. As a result severe performance degradation was observed in the region of high current densities. A short overview over the phenomena which may contribute to this specific fuel cell degradation is compiled from literature. Based on this overview major degradation modes are identified and combined with a simple polarization curve model. The modeling results allow for two different interpretations. Carbon corrosion reactions can explain the observed effects if cell voltage is assumed as the driving force for degradation. A better fit was obtained by using the overall heat flux as degradation criterion. In this case an increase in local temperature could lead to redistribution and loss of phosphoric acid from the MEA. The expected lifetime of a polymer electrolyte fuel cell (PEFC) ranges from 5 000 h for mobile application to 40 000 h for stationary application.1,2 In order to gain information about time dependent degradation in advance accelerated test protocols are used.3,4 Depending on the design of these tests valuable information about the nature of the main degradation mode under the applied operation conditions can be obtained. Despite the difference in operation conditions for PEFC, HT-PEFC and PAFC the structure and material of the electrodes are almost the same. Consequently, observed degradation phenomena show strong similarities.5 A good description of these phenomena can be found in several review papers 6-13 as well as in at least four books 1,2,14,15 where recent experimental facts and interpretations are summarized. A compact description can also be found in a recent review paper on modeling transport phenomena in PEFCs. 16 The purpose of this paper is to present the results of a specific accelerated degradation test for high temperature polymer electrolyte fuel cells (HT-PEFC) with phosphoric acid doped polybenzimidazole (PBI/H 3 PO 4 ) membranes. The fuel cell is constantly under load with frequent periods of very high current. In order to accelerate degradation effects the fuel cell is operated beyond it's point of maximum power. A simple polarization curve model is used as starting point for the analysis of data. Based on this first analysis a degradation model is proposed which allows for a straightforward physical interpretation. The complexity of degradation effects which occur simultaneousy usually leads to models which either resolve a specific mechanism in depth or describe more general effects. This paper aims at general effects which requires a broader understanding of degradation. In the following it is attempted to provide an overview over the phenomena which may contribute to fuel cell degradation. Based on this overview major degradation modes are identified and ...

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Section: Journal Of the Electrochemical Society 162 (1) F153-f164 (2mentioning

confidence: 99%

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Reimer

Schumacher

Lehnert

2014

J. Electrochem. Soc.

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“…For a more evident quantification of the current homogenization, an additional factor is introduced -the relative mean spread of current density (S) (equation (12)), similar to [21]. The new factor (S) shows the mean spread between extreme current density values (minimum and maximum) and the average current density.…”

Section: Relative Mean Spreadmentioning

confidence: 99%

“…This causes an increase in measured current density at the left and right rim. More details about the stack experiment are provided in a separate paper [21]. The stack flow field is shown in Fig.…”

Section: Consistency Of the Modelmentioning

confidence: 99%

“…Each operating point is characterized by local distribution of current density and temperature within the stack. It should be mentioned that the volumetric composition of anode gas in the experiment is adjusted to 42.1%, whereby the gas flow is controlled with an accuracy of AE0.8% of the full scale and AE0.2% of the actual set point [21]. The boundary and operating conditions for the simulations are provided in Table 3.…”

Section: Model Validationmentioning

confidence: 99%

“…This is due to the measurement tolerance of the measuring cells and the calibration procedure. Further details can be found in [21]. (ii) The simulated results are obtained at the surface of the MEA, whereby the measured data origins from the segmented plate between the 3rd and 4th cell.…”

Section: Model Validationmentioning

confidence: 99%

See 2 more Smart Citations

3D modeling of an HT-PEFC stack using reformate gas

Kvesić

Reimer

Froning

et al. 2012

International Journal of Hydrogen Energy

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Start‐Up of HT‐PEFC Systems Operating with Diesel and Kerosene for APU Applications

et al. 2014

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Fuel‐cell‐based auxiliary power units offer power generation with reduced fuel consumption and low emissions. A very promising system is the combination of an autothermal reformer with a high‐temperature polymer electrolyte fuel cell. A fast start‐up procedure is a crucial requirement for the use of this system as an auxiliary power unit. This paper reports on the development of a suitable start‐up strategy for a 10 kWel auxiliary power unit with a start‐up burner. A commercially available diesel burner was tested as a start‐up device. A dynamic MATLAB/Simulink model was developed to analyze different start‐up strategies. With the currently available apparatus and start‐up burner it takes 2,260 s before power generation can begin according to simulation results. The fuel processor alone would be ready for operation after 1,000 s. An optimization of the fuel cell stack with regard to its thermal mass would lead to a start‐up time of 720 s. A reduction to 600 s is possible with a slight customization of the start‐up burner.

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Performance analysis of HT-PEFC stacks

Cited by 47 publications

References 51 publications

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

3D modeling of an HT-PEFC stack using reformate gas

Start‐Up of HT‐PEFC Systems Operating with Diesel and Kerosene for APU Applications

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