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Polymer Electrolyte Fuel Cells in Reformate Power Generators
KTH, School of Chemical Science and Engineering (CHE). (Applied Electrochemistry)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The topic of this thesis is the generation of electricity from hydrocarbon fuels via polymer electrolyte fuel cells (PEFC). The aim has been to develop methods and hardware for experimental evaluation of process parameters and design variables in PEFC reformate cells and stacks.

Reformate fuel cell systems have the potential to offer a way for utilizing fuels efficiently with low global and local emissions. Reforming of hydrocarbon fuels may also provide a way around the famous “chicken or egg” dilemma of hydrogen vehicles and infrastructure.

In this thesis current distribution measurements are introduced as a tool for investigating the current distribution in a PEFC with Pt/C or PtRu/C anode catalyst as function of reformate fuel gas composition. It is shown that CO may induce a strong transient behavior, with respect to current density, on both Pt/C and PtRu/C catalysts, depending on mode of operation. Analysis of the exhaust fuel gas showed that the oxygen in the air bleed most likely reacts close to the anode inlet, but this is not visible in the measured current density plots.  The time dependence of the CO poisoning reactions is studied more closely in a commercial fuel cell stack.

The development of a test fuel cell system, called multisinglecell, that can multiply the capacity of a conventional test station is reported. The setup is successfully demonstrated with initial screening of the corrosion resistance of different stainless steel grades and coatings. Most of the iron originating from a stainless steel sample accumulates in the MEA and GDLs. These results were validated with a similar measurement in a commercial fuel cell stack.

The experimental validation of a 3D FEM computer endplate model, which can accurately predict pressure distribution within any type of fuel cell at any temperature, is described. The model could reliably predict trends in changes in the compression pressure distribution.

The PBI fuel cell competes with the PEFC in small-scale power applications. A high temperature break-in procedure for PBI fuel cells is developed, which can rapidly and reproducibly ensure stable cell behavior.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 59 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:54
Keyword [en]
Chemical, Automotive
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26938ISBN: 978-91-7415-821-2 (print)OAI: oai:DiVA.org:kth-26938DiVA: diva2:373328
Public defence
2010-12-17, E3, Lindstedtsvägen 3, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2010-11-30Bibliographically approved
List of papers
1. The influence of CO2, CO and air bleed on the current distribution of a polymer electrolyte fuel cell
Open this publication in new window or tab >>The influence of CO2, CO and air bleed on the current distribution of a polymer electrolyte fuel cell
Show others...
2008 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, no 33, 2064-2072 p.Article in journal (Refereed) Published
Abstract [en]

The influence of CO2, CO and air bleed on current distribution was studied during transient operation, and the dynamic response of the fuel cell was evaluated. CO causes significant changes in the current distribution in a polymer electrolyte fuel cell. The current distribution reaches steady state after approximately 60 min following addition of 10 ppm CO to the anode fuel stream. Air bleed may recover the uneven current distribution caused by CO and also the drop in cell voltage due to CO and CO2 poisoning. The recovery of cell performance during air bleed occurs evenly over the electrode surface even when the O-2 partial pressure is far too low to fully recover the CO poisoning. The O-2 supplied to the anode reacts on the anode catalyst and no O-2 was measured at the cell outlet for air bleed levels up to 2.5%.

Keyword
PEFC Current distribution Reformate carbon dioxide
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-13216 (URN)10.1016/j.ijhydene.2008.02.002 (DOI)000256606900011 ()2-s2.0-42749087163 (Scopus ID)
Note

QC 20150727

Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2017-12-12Bibliographically approved
2. Experimental results from a 5 kW PEM fuel cell stackoperated on simulated reformate from highly dilutedhydrocarbon fuels: Efficiency, dilution, fuel utilisation,CO poisoning and design criteria
Open this publication in new window or tab >>Experimental results from a 5 kW PEM fuel cell stackoperated on simulated reformate from highly dilutedhydrocarbon fuels: Efficiency, dilution, fuel utilisation,CO poisoning and design criteria
2009 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, no 34, 1508-1514 p.Article in journal (Refereed) Published
Abstract [en]

The present article analyses the effects of dilute biogas on efficiency, fuel utilisation, dynamics, control strategy, and design criteria for a polymer electrolyte fuel cell (PEFC) system. The tested fuel compositions are exemplified by gas compositions that could be attained within various Swedish biofuel demonstration projects. Experimental data which can serve as a basis for design of PEFC biogas systems operating in load-following, or steady-state mode, are reported for a 5 kW PEFC stack.

Keyword
PEFC Air bleed Reformate Biogas CO
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-13217 (URN)10.1016/j.ijhydene.2008.11.079 (DOI)000263666000046 ()2-s2.0-58649097489 (Scopus ID)
Note

QC 20150723

Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2017-12-12Bibliographically approved
3. Modelling compression pressure distribution in fuel cell stacks
Open this publication in new window or tab >>Modelling compression pressure distribution in fuel cell stacks
2009 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 193, no 1, 269-275 p.Article in journal (Refereed) Published
Abstract [en]

A general purpose 3D finite element method model has been developed for the estimation of the compression pressure distribution in fuel cell stacks. The model can be used for the optimisation of any type of fuel cell structure at any temperature. The model was validated with pressure sensitive film measurements using PEFC stack components that had low rigidity and were highly deformable.

Place, publisher, year, edition, pages
ELSEVIER, 2009
Keyword
Stack, Clamping pressure, Pressure distribution, Modelling, FEM
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-26936 (URN)10.1016/j.jpowsour.2009.01.033 (DOI)000267561400039 ()
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2017-12-12Bibliographically approved
4. Cost effective in-situ characterization of coatings for PEFCbipolar plates demonstrated with PVD deposited CrN
Open this publication in new window or tab >>Cost effective in-situ characterization of coatings for PEFCbipolar plates demonstrated with PVD deposited CrN
Show others...
2011 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, no 5, B550-B556 p.Article in journal (Refereed) Published
Abstract [en]

The corrosion and contact resistances of coated and uncoated stainless steel grades were studied. The coatings studied were PVD CrN and arc discharge deposited Au. The samples were aged in long steady-state experiments using a multisinglecell device. MEAs and exhaust water were analyzed for accumulated iron after measurements. Iron accumulation was measured from MEAs, exhaust water and gas outlet pipes from the cells. The interfacial contact resistances were measured before and after the fuel cell experiments. Low contact resistance was achieved with all coated samples. The main accumulation site of dissolved iron was found to be the MEA and GDLs. A large variation in the corrosion results due to differences in the coating quality was observed. Some coatings with low interfacial contact resistance were found to be prone to corrosion. The CrN coating was also tested in a stack, and it performed well. It was concluded that the multisinglecell is a useful tool for screening different coatings reliably and cost-effectively.

Keyword
CrN, Coating, PEFC, Au, Fuel cell
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-26937 (URN)
Note
Updated from submitted to published. QC 20120326Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2017-12-12Bibliographically approved
5. A rapid break-in procedure for PBI fuel cells
Open this publication in new window or tab >>A rapid break-in procedure for PBI fuel cells
2009 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 34, no 15, 6452-6456 p.Article in journal (Refereed) Published
Abstract [en]

Different break-in procedures for phosphoric acid doped polybenzimidazole membrane fuel cells (PBI-FC) have been studied, including voltage cycling and the use of constant current at different temperatures. A rapid break-in procedure consisting of high-temperature constant current break-in and relaxation has been developed. The break-in procedure is considered suitable for contamination and performance studies.

Place, publisher, year, edition, pages
ELSEVIER, 2009
Keyword
Fuel cell, High temperature, HTPEM, Conditioning, Activation, PBI, Break-in
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-26935 (URN)000269561000049 ()
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2017-12-12Bibliographically approved

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