Fuel cell degradation failure modes

Previous work includes a Failure Mode Identification (FMEA) and fault Tree Analysis (FTA) of a general PEMFC by Rama, et al. (2008). Additionally, a more recent FTA work was presented by Placca. L Kouta. R (2011), looking at the failure modes that could cause PEMFC degradation, yielding a more detailed fault tree of fuel cell degradation. 

Much recent ongoing work has focused on the chemical degradation mechanisms and revealed that radical attack is the root cause of the membrane decomposition. However, there is still a lack of fundamental understanding of the mechanisms for the degradation of mechanical strength, which is related to the membrane failure mode responsible for the sudden death behavior of fuel cells. 

Various studies have focused on the degradation mechanisms of either the fuel cell system or its components under steady or accelerated operational conditions. The major failure modes of different components of PEM fuel cells are listed in Table 1.2. 

The scientific community has made great progress in increasing the durability of polymer electrolyte membrane fuel cell (PEMFC) systems, but durability must further increase before we can consider fuel cells economically viable [1]. As durability increases, new modes of fuel cell contamination and failure are exposed. We expect state of the art PEMFC systems to run for thousands of hours. This means that each sulfonate group in typical per-fluorosulfonic acid (PFSA) membranes used in today s PEMFC systems will associate with several million protons over the lifetime of the systems. Even if other cations replace only a small fraction of the protons entering the electrolyte membrane, these contaminant cations can build up in the system and degrade the fuel cell system performance over time. 

Failure modes studied included fuel starvation and cell reversal, partial fuel starvation, carbon corrosion, membrane thinning and hole formation oxidant starvation excessive drying and flooding, air and fuel contamination, freeze-start and freeze-thaw degradation. 

The durability of fuel cells needs to be increased by about five times the current rates (e.g., at least 60,000 h for the stationary distributed generation sector) in order for fuel cells to present a long-term reliable alternative to the current power generation technologies available in the maiket. The degradation mechanisms and failure modes within the fuel cell components and the mitigation measures that could be taken to prevent failure need to be examined and tested. Contamination mechanisms in fuel cells due to air pollutants and fuel impurities need to be carefully addressed to resolve the fuel cell durability issue. 

This book provides a systematic review of PEM fuel cell durability and failure modes, progressing from component degradation to contamination-, environment-, operation-, and design-induced degradation, with each chapter covering one topic. Chapters 2 through 7 examine the degradation of various... 

Membrane degradation can result in loss of the electrolyte, loss of separator functionality, and severe fuel cell failure. In following sections, three membrane degradation modes—chemical, mechanical, and thermal—are introduced. 

PEM Fuel Cell Failure Mode Analysis presents a systematic analysis of PEM fuel cell durability and failure modes. It provides readers with a fundamental understanding of insufficient fuel cell durability, identification of failure modes and failure mechanisms of PEM fuel cells, fuel cell component degradation testing, and mitigation strategies against degradation. 

Presents degradation testing protocols important for durability and failure mode studies of PEM fuel cells... 

Written by international scientists active in PEM fuel cell research, this volume is enriched with practical information on various failure modes analysis for diagnosing cell performance and identifying failure modes of degradation. This, in turn, helps in the development of mitigation strategies and the increasing commercialization of PEM fuel cells. 

For MEA designers or fuel cell stack engineers, a polarization curve is an immensely useful practical analysis tool. It allows for a comparative assessment of sources of voltage losses in the cell, fuel cell failure modes, critical or limiting current densities, as well as impacts of degradation and water management. For materials scientists, the polarization curve entails useful information on performance effects... 

Previous failure mode and effect analysis and fault tree analysis work by the authors has shown that the inherently complex system of a PEMFC assembly can harbor dependencies between multiple failure modes. Therefore in this presented work, Petri-Net simulation has been adopted to develop a more accurate degradation model. Operational parameters such as water content, temperature and current density s effects on the occurrence of failure modes can be modelled through this technique. This work will improve previous fuel cell reliability studies by taking into consideration operating parameters (water content, temperature), ambient weather and fuel cell voltage demand (drive cycles). 

SSC was chosen as a failure mode to verify initially, as this Petri-Net interaction is relatively simple, and easy to analyse for effective modelling. SSC degradation was considered through a review of the literature in this area. Hong Kim, et al. (2010) conducted extensive experimentation to reveal the relationship between SSC and degradation of fuel cell performance. Their results show that after 1500 instances of SSC, a drop in performance of 0.08 V was observed (Fig. 8). Therefore per cycle it can be considered that SSC causes a drop in performance of 5.333 x 10 V. 

Rama, P. et al. 2008 A review of performance degradation and failure modes for hydrogen fuelled polymer electrolyte fuel cells, Proceedings of the Institution of Mechanical Engineers, Part A Journal of Power and Energy, vol 222, no. 5, 4214—441. 

Rama P, Chen R, Anehews J (2008) A review of performance degradation and failure modes for hydrogen-firelled polymer eleetorlyte fuel cells. Proc Inst Mech Eng Part A J Power Energy 222(A5) 421 1... 

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