Colored collectors

Development of colored glazing for solar facades

Contact: Andreas Schueler

The architectural integration of  solar technology into buildings is often limited by aesthetical considerations: thermal solar collectors are disadvantaged by their black color and the visibility of tubes and corrugations of the absorber sheets and photovoltaic panels by their characteristical blue appearance. A certain freedom in color choice would lead to wider use of solar technology, but the colored appearance should not cause excessive performance degradation.

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 manufactured by the sol-gel dip-coating process or magnetron sputtering techniques. Optical measurements, such as spectrophotometry or ellipsometry, are used to determine film thicknesses and optical constants of individual layers, and to measure color coordinates and solar transmission for the multilayer stacks. Nanostructured materials are tailored for maximizing the optical performance.

Based on this technology, our group has developed colored glazed solar thermal and photovoltaic collectors for architectural integration into buildings. These now cover – among other – the iconic new building of Copenhagen International School, described by Mother Nature Network as one of “5 solar-powered buildings that will forever change architecture”.

Two patents have been filed and are commercialised by SwissINSO:

WO 2014045141 A2: Laminated glazing with coloured reflection and high solar transmittance suitable for solar energy systems

WO 2014045144 A1: Interference filter with angular independent orange colour of reflection and high solar transmittance, suitable for roof-integration of solar energy systems

Copenhagen International School waterfront view with colored solar cladding
Copenhagen International School, designed by C.F. Møller Architects & sits, solar façade designed by Danish company SolarLab with Kromatix technology developped by LESO-PB and Emirates Intersolaire (photo P. Vollichard)


acomet façade with coloured solar collectors
DOMA Solartechnik GmbH Headquarters, Satteins, Austria

In the media

HG-Gebäudetechnik 4/18: Fassadenintegration mit farbigen Oberflächen
24heures : La technologie de l’EPFL rayonne sur l’Ecole internationale de Copenhague
L’Agefi : Une technologie développée à l’EPFL recouvre une école entière : La plus grande façade solaire au monde
Le Matin du Dimanche: Grâce à Andreas Schueler l’énergie solaire se décline enfin en couleur : School claims largest solar façade in the world : World’s Largest Solar Glass Envelope To Supply Electricity At Copenhagen International School
Daily Planet Blog: This Danish School has installed the World’s Largest Solar Facade : Architektur: Die Schule mit der weltgrößten Solarfassade | AUTO : Architektur: Die Schule mit der weltgrößten Solarfassade
energate messenger Schweiz : Schweizer Technologie macht dänische Solarfassade farbig : Schweizer Technologie ermöglicht farbige Solarfassade
Baublatt : In Kopenhagen treibt es eine Solaranlage bunt


S. Mertin; V. Hody-Le Caër; M. Joly; I. Mack; P. Oelhafen et al. : Reactively sputtered coatings on architectural glazing for coloured active solar thermal façades; Energy and Buildings. 2014. DOI : 10.1016/j.enbuild.2012.12.030.
V. Hody-Le Caër; E. De Chambrier; S. Mertin; M. Joly; M. Schaer et al. : Optical and morphological characterisation of low refractive index materials for coatings on solar collector glazing; Renewable Energy. 2013. DOI : 10.1016/j.renene.2012.10.052.
S. Pélisset; M. Joly; V. Chapuis; A. Schueler; S. Mertin et al. : Efficiency of silicon thin-film photovoltaic modules with a front coloured glass. 2011. CISBAT 2011, Lausanne, Switzerland, September 14-16, 2011. p. 37-42.