Characterization and aging studies of selective solar C/Al<sub>2</sub>O<sub>3</sub>/Al absorber surfaces

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.author Konttinen, Petri
dc.date.accessioned 2012-02-13T12:41:52Z
dc.date.available 2012-02-13T12:41:52Z
dc.date.issued 2004-04-23
dc.identifier.isbn 951-22-7003-X
dc.identifier.issn 1459-7268
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/2403
dc.description.abstract Solar thermal collectors are mainly used for domestic water and space heating. They capture incident solar radiation, convert it to usable thermal energy, and transfer the energy into a heat transfer fluid. All of this should be accomplished economically with minimal energy loss. One of the most important components of the solar thermal collector is the solar absorber. To be effective, the absorber should exhibit wavelength selectivity, i.e. have maximum solar absorptance and minimum thermal emittance. Selective solar absorbers have been studied intensively since the 1950's. State-of-the-art sputtered selective solar absorbers have good optical properties and long lifetime. A drawback can be high manufacturing costs. The main purpose of this thesis was the characterization and improvement of a mechanically-manufactured selective C/Al2O3/Al absorber surface. The manufacturing method is the only one based on solely mechanical treatment. The optical properties and microstructure of surface samples were analysed. Together with an industrial partner the manufacturing methods were refined. Comprehensive accelerated aging studies were carried out for the absorber surface. As a result the solar absorptance and the thermal emittance were improved to 0.90 and 0.22, respectively. The microstructure of the surface is composed of microgrooves and unhomogeneous carbon, graphite or graphite/alumina clusters. Inside a glazed collector a service lifetime between 20 and 25 years can be expected. The main degradation mechanism found was hydration of Al2O3 if condensed water is present on the surface at an elevated temperature. For very humid climates, an additional moisture barrier would be advisable even for glazed collector applications. For non-glazed applications moisture resistance needs to be improved. The price of the required manufacturing infrastructure for the C/Al2O3/Al absorber varies. It may be very low for manual manufacturing up to some tens of thousands euros for a more sophisticated mechanical workshop. Optical properties and energy yield of the C/Al2O3/Al absorber are in the same range as the best commercial spectrally selective paints, but lower than sputtered surfaces. Economically the C/Al2O3/Al absorber may compete with selective and non-selective paints in most glazed applications. en
dc.format.extent 69, [88]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Helsinki University of Technology publications in engineering physics. A en
dc.relation.ispartofseries 826 en
dc.relation.haspart Konttinen P., Lund P. D. and Kilpi R. J., 2003. Mechanically manufactured selective solar absorber surfaces. Solar Energy Materials and Solar Cells 79, number 3, pages 273-283. [article1.pdf] © 2003 Elsevier Science. By permission.
dc.relation.haspart Konttinen P., Kilpi R. J. and Lund P. D., 2003. Microstructural analysis of selective C/Al<sub>2</sub>O<sub>3</sub>/Al solar absorber surfaces. Thin Solid Films 425, numbers 1-2, pages 24-30. [article2.pdf] © 2003 Elsevier Science. By permission.
dc.relation.haspart Konttinen P. and Lund P. D., 2002. Characterization of selective absorbers prepared through a mechanical treatment. Invited lecture, in Proceedings of the World Renewable Energy Congress VII. Cologne, Germany, 29 June - 5 July, 2002. [article3.pdf] © 2002 Elsevier Science. By permission.
dc.relation.haspart Konttinen P. and Lund P. D., Thermal stability and moisture resistance of C/Al<sub>2</sub>O<sub>3</sub>/Al solar absorber surfaces. Solar Energy Materials and Solar Cells, in press. [article4.pdf] © 2004 Elsevier Science. By permission.
dc.relation.haspart Konttinen P. and Lund P. D., 2004. Microstructural optimization and extended durability studies of low-cost rough graphite-aluminium solar absorber surfaces. Renewable Energy 29, number 6, pages 823-839. [article5.pdf] © 2004 Elsevier Science. By permission.
dc.relation.haspart Konttinen P. and Lund P. D., Physical interpretation of impacts from a low cost manufacturing process on the surface microstructure of a novel solar absorber. Solar Energy Materials and Solar Cells, accepted for publication. [article6.pdf] © 2004 by authors and © 2004 Elsevier Science. By permission.
dc.relation.haspart Konttinen P., Salo T. and Lund P. D., Corrosion of unglazed rough graphite-aluminium solar absorber surfaces in simulated acid and neutral rain. Solar Energy, submitted for publication. [article7.pdf] © 2004 by authors and © 2004 Elsevier Science. By permission.
dc.subject.other Energy en
dc.title Characterization and aging studies of selective solar C/Al<sub>2</sub>O<sub>3</sub>/Al absorber surfaces en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Engineering Physics and Mathematics en
dc.contributor.department Teknillisen fysiikan ja matematiikan osasto fi
dc.subject.keyword solar energy en
dc.subject.keyword solar thermal absorber en
dc.subject.keyword accelerated aging en
dc.subject.keyword mechanical manufacturing en
dc.identifier.urn urn:nbn:fi:tkk-003486
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Advanced Energy Systems en
dc.contributor.lab Energiateknologiat fi


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