Publikationen / Ergebnisse
(Englisch)
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go-PEF-CH is a project within the PEF-CH framework, involving academic institutions (Paul Scherrer Institut PSI, Berner Fachhochschule für Technik und Informatik BFH-TI) and Swiss Industry (CEKA, MESDEA). 2 PhD theses are to be carried out under the aegis of PSI. The objective is to investigate membrane electrode assembly (MEA) degradation phenomena and aging mechanisms under application-near operating conditions, encompassing rapid load transients and start-stop cycles.
So far, no suitable candidates for the 2 PhD positions have been identified. The kickoff meeting of ‘go.PEF-CH’ was held on Nov. 30 at PSI. The Swiss hydrogen and fuel cell community came together on the occasion of the Impulse Day 2007, organized by the SFOE and hosted by PSI, giving extensive opportunity for exchanging ideas and networking.
Auftragnehmer/Contractant/Contraente/Contractor:
Paul Scherrer Institut
Autorschaft/Auteurs/Autori/Authors:
Gubler,L.
Schneider,Ingo
Scherer,Günther G.
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Schlussbericht
(Englisch)
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In the go.PEF-CH project, involving the two Swiss industrial partners CEKAtec AG (Wattwil SG) and MES S.A. (Stabio TI), we a) develop the necessary diagnostic tools to investigate transients occurring during non-steady state operation of a polymer electrolyte fuel cell (PEFC), b) measure and quantify respective transients and degradation in custom-built cells as well as technical cells, and c) identify and implement mitigation strategies to improve fuel cell lifetime under application-relevant conditions. We have gained fundamental insights into the local current distribution via the measurement of local currents and the distribution of liquid water using neutron radiography, both in hardware supplied by MES and in-house built model cells. Key results are the mapping of current density along the channels of the flow field (scale: cm to tens of cm) and on the scale of channels and lands (sub-mm resolution). For the latter, a unique 1 cm2 cell with micro-flow field was developed and built at PSI. Key transients that were resolved are short-circuiting of the cell, which is used in the fuel cell systems of MES S.A. to provide intermittent humidification, and start-stop procedures. An implication of using a channel and land geometry for reactant distribution are diffusion limitations. We show that a small differential pressure between adjacent cells significantly improves current generation under the land. This insight can be used to improve the flow field of the fuel cell. The analysis of the short-circuit effects on possible aging of the MEA could not be fully completed and may require additional work for quantification of the degradation phenomena. The start-stop induced degradation of PEFCs was investigated comprehensively on all levels of complexity in single cells and stacks, ranging from fundamental investigations in single cells under controlled potential conditions to start-stop cycling in a 30-cell stack. Based on the analysis of important influencial parameters (humidity, auxiliary resistance, etc.), application- relevant start stop protocols were implemented. In the stack, a distinct influence of the position of individual cells in the stack on the rate of degradation as a result of start-stop cycling was identified. This is a result of the non-ideal distribution of gas during start-up and shutdown. Further work may be necessary to address these inhomogeneities on the stack level.
Auftragnehmer/Contractant/Contraente/Contractor:
Paul Scherrer Institut
Autorschaft/Auteurs/Autori/Authors:
Gubler,L.
Linse,Nicolas
von Dahlern,Steffen
Höckel,Michael
Höckel,Michael
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