Improved durability and reduced system complexity of solid oxide fuel cell systems

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Kiviaho, Jari, Dr., VTT Technical Research Centre of Finland, Finland
dc.contributor.advisor Himanen, Olli, Dr., VTT Technical Research Centre of Finland, Finland Thomann, Olivier 2015-12-10T10:03:08Z 2015-12-10T10:03:08Z 2015
dc.identifier.isbn 978-951-38-8361-4 (electronic)
dc.identifier.isbn 978-951-38-8360-7 (printed)
dc.identifier.issn 2242-119X (electronic)
dc.identifier.issn 2242-1203 (printed)
dc.identifier.issn 2242-119X (ISSN-L)
dc.description.abstract Solid oxide fuel cells (SOFCs) show great potential for clean and efficient power generation applications. However, their high cost is preventing their market entry. This dissertation focuses on solutions to increase the durability of SOFCs and to reduce the complexity of SOFC systems to drive their cost down. Chromium poisoning of the cathode is a major issue limiting the durability of SOFCs. This issue is addressed by the development of a protective manganesecobalt spinel coating for steel interconnects. Coated interconnects were characterised in SOFC relevant conditions and the results showed that the coating fulfilled its main requirements, which are: limitation of chromium transport from the interconnect to the cathode, protection against oxidation of the steel and low and stable area-specific resistance. Evidence was found that another source of chromium is the balance-of-plant (BoP) components upstream of the cathode, an issue which did not receive much attention in the literature. Therefore, a method for measuring chromium evaporation from BoP components was developed and validated on a stainless steel pipe. SOFC systems based on natural gas commonly include a fuel processing subsystem for fuel steam reforming. The need for an external water source can be eliminating by recycling the steam-rich anode off-gas. Investigations were performed on a pre-reformer with a precious metal catalyst and it was found that adding an anode off-gas recycling loop had no detrimental effect on the activity of the catalyst and carbon formation could be avoided. Additionally, results showed the possibility to generate the hydrogen-containing gas needed to prevent the reoxidation of the anode catalyst during heat-up phase. The results permitted the implementation of an anode off-gas recycling loop in a 10 kW SOFC system. Additionally, the system was heated up without supplying any premixed hydrogencontaining gas, which enables to reduce the complexity of the system. Finally, the durability of a stack can be improved by seal solutions with limited material interactions. A hybrid seal solution was developed by coating a compressible core with glass layers. The developed seal reduced the leak rate compared to a purely compressible seal. Material interactions were studied with a post-experimental investigation of an SOFC stack. Interactions were limited with the exception of evidence of increased oxidation at the steel/seal/air interface. Overall, the solution was found to be promising and the obtained results led to the commercialisation of the developed seal solution by Flexitallic Ltd (UK). en
dc.format.extent 87 + app. 49
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries VTT Science en
dc.relation.ispartofseries 112
dc.relation.haspart [Publication 1]: Thomann, O., Pihlatie, M., Rautanen, M., Himanen, O., Lagerbom, J., Mäkinen, M., Varis, T., Suhonen, T, Kiviaho, J. Development and application of HVOF sprayed spinel protective coating for SOFC interconnects. Journal of Thermal Spray Technology 2013, Vol. 22, No. 5, pp. 631–639. DOI: 10.1007/s11666-012-9880-9
dc.relation.haspart [Publication 2]: Thomann, O., Pihlatie, M., Schuler, J.A., Himanen, O., Kiviaho, J. Method for measuring chromium evaporation from SOFC balance-ofplant components. Electrochemical and Solid-State Letters 2012, Vol. 15, No. 3, pp. B35–B37. DOI: 10.1149/1.3570260
dc.relation.haspart [Publication 3]: Halinen, M., Thomann, O., Kiviaho, J. Effect of anode off-gas recycling on reforming of natural gas for solid oxide fuel cell systems. Fuel Cells 2012, Vol. 12, No. 5, pp. 754–760. DOI: 10.1002/fuce.201200047
dc.relation.haspart [Publication 4]: Halinen, M., Thomann, O., Kiviaho, J. Experimental study of SOFC system heat-up without safety gases. International Journal of Hydrogen Energy 2014, Vol. 39, No. 1, pp. 552–561. DOI: 10.1016/j.ijhydene.2013.10.043
dc.relation.haspart [Publication 5]: Rautanen, M., Thomann, O., Himanen, O., Tallgren, J., Kiviaho, J. Glass coated compressible solid oxide fuel cell seals. Journal of Power Sources 2014, Vol. 247, pp. 243–248. DOI: 10.1016/j.jpowsour.2013.08.085
dc.relation.haspart [Publication 6]: Thomann, O., Rautanen, M., Himanen, O., Tallgren, J., Kiviaho, J. Post-experimental analysis of a solid oxide fuel cell stack using hybrid seals. Journal of Power Sources 2015, Vol. 274, pp. 1009–1015. DOI: 10.1016/j.jpowsour.2014.10.100
dc.subject.other Energy en
dc.title Improved durability and reduced system complexity of solid oxide fuel cell systems en
dc.type G5 Artikkeliväitöskirja fi Perustieteiden korkeakoulu fi School of Science en
dc.contributor.department Teknillisen fysiikan laitos fi
dc.contributor.department Department of Applied Physics en
dc.subject.keyword fuel cells en
dc.subject.keyword SOFC en
dc.subject.keyword chromium poisoning en
dc.subject.keyword anode off-gas recycling en
dc.subject.keyword system heat-up en
dc.subject.keyword seal en
dc.subject.keyword interconnect en
dc.subject.keyword material interactions en
dc.identifier.urn URN:ISBN:978-951-38-8361-4
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Lund, Peter, Prof., Aalto University, Department of Applied Physics, Finland 2015-12-09

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