Kurzbeschreibung
(Französisch)
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L'accord porte sur un travail de la conception et la réalisation d'un vitrage coloré, utilisable pour les capteurs solaires thermiques, les rendant aptes à refléter des couleurs au choix du projeteur (architecte), sans pertes notables de performances énergét
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Publikationen / Ergebnisse
(Englisch)
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The architectural integration of thermal solar collectors into buildings is often limited by their black color, and the visibility of tubes and corrugations of the absorber sheets. A certain freedom in color choice would be desirable, but the colored appearance should not cause an excessive degradation of the collector efficiency. Multilayered thin film interference filters on the collector glazing can produce a colored reflection, hiding the corrugated metal sheet, while transmitting the non-reflected radiation entirely to the absorber. These interference filters are designed and optimized by numerical simulation, and are manufactured by sol-gel dip-coating or magnetron sputtering. The novel colored glazed solar collectors will be ideally suited for architectural integration into buildings, e.g. as solar active glass facades. Due to the tunability of the refractive index, nanostructured materials such as SiO2:TiO2 composites and porous SiO2 are very useful for application in multilayer interference stacks. Novel quaternary Mg-F-Si-O films exhibit a surprisingly low refractive index and are therefore promising candidates for highly transparent coatings on solar collector glazing. The nanostructure of these thin films is studied by transmission electron microscopy, while the optical constants are measured precisely by ellipsometry. For a convincing demonstration, sufficiently large samples of high quality are imperatively needed. The fabrication of nanocomposite SiO2:TiO2 films has been demonstrated by sol-gel dip-coating of A4 - sized glass panes. The produced coatings exhibit a colored reflection in combination with a high solar transmittance, a homogenous appearance, and are free of visible defects. Film hardening by UV exposure will result in speeding up the sol-gel process and saving energy, thereby reducing costs significantly. The infrastructure for UV-curing has been established. A UVC radiation source can now be attached to the dip-coater, which is placed in a UV-screened laminar flow chapel. An industrial partner for the prototype fabrication of colored collector glazing has been found. For a first attempt of industrial scale production, adapted multilayer designs have been proposed. First tests on the industrial magnetron sputtering equipment have shown encouraging results, but some adaptations are still needed.
Possible ways of implementation of the novel colored solar collectors/solar facades are investigated and discussed with facade manufacturers and architects.
Auftragnehmer/Contractant/Contraente/Contractor:
EPFL - LESO - PB
Autorschaft/Auteurs/Autori/Authors:
Schüler,Andreas
De Chambrier,Estelle
Roecker,Christian
Scartezzini,Jean-Louis
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Schlussbericht
(Englisch)
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The architectural integration of glazed thermal solar collectors into buildings facades is limited by several factors: limited dimensional freedom, limited jointing choice and above all the black color and surface irregularities of the absorber visible behind collector glazing. Unlike for the two first factors that can be handled by industry, color is more complex. A certain freedom in color choice would be desirable, but the colored appearance should not cause an excessive degradation of the collector efficiency. Multilayered interference filters on the cover glass can produce an energy-efficient colored reflection, hiding the corrugated metal sheet, while transmitting the non-reflected radiation entirely to the absorber. These interference filters are designed and optimized by numerical simulation, and are manufactured by sol-gel dip-coating or magnetron sputtering.
Nanocomposite and nanoporous thin films are perfectly suited for the considered application. Due to the tunability of the refractive index, nanostructured materials such as SiO2:TiO2 composites and porous SiO2 are very useful for application in multilayer interference stacks. Novel quaternary Mg-F-Si-O films exhibit a surprisingly low refractive index and are therefore promising candidates for highly transparent coatings on solar collector glazing. The nanostructure of these thin films is studied by transmission electron microscopy, while the optical constants are measured precisely by ellipsometry.
For a convincing demonstration, sufficiently large samples of high quality are imperatively needed. The sol-gel deposition of the multilayered coatings on A4 - sized glass panes has been demonstrated in the laboratory by EPFL-LESO. The produced coatings exhibit a colored reflection in combination with a high solar transmittance, a homogenous appearance, and are free of visible defects. Film hardening by UV exposure will result in speeding up the sol-gel process and saving energy, thereby reducing costs significantly.
In collaboration with industry, real scale glass panes are coated with the novel multilayers. The novel glazing is integrated into first prototype collectors.
The necessary characteristics needed to successfully integrate solar collectors into facades have been thoroughly studied and published. Combined with selected interference filters colors, the various possible diffusing treatments have been studied and tested both on A4 size samples and on real size collector glasses. One major advantage of the new glazing has been shown, namely the possibilities opened by the use of the same glass for collectors and insulation cladding. Feedback collected from architects and other users has demonstrated the great interest for the architectural possibilities offered by this new glazing.
Auftragnehmer/Contractant/Contraente/Contractor:
Autorschaft/Auteurs/Autori/Authors:
Schüler,Andreas
Roecker,Christian
De Chambrier,Estelle
Munari Probst,Maria Cristina
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