uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Light-scattering properties of a Venetian blind slat used for daylighting applications
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2010 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 12, 2103-2111 p.Article in journal (Refereed) Published
Abstract [en]

The low cost, simplicity, and aesthetic appearance of external and internal shading devices, make them commonly used for daylighting and glare-control applications. Shading devices, such as Venetian blinds, screens, and roller shades, generally exhibit light scattering and/or light redirecting properties. This requires the bi-directional scattering distribution function (BSDF) of the material to be known in order to accurately predict the daylight distribution and energy flow through the fenestration system. Acquiring the complete BSDF is not a straightforward task, and to complete the process it is often required that a model is used to complement the measured data. In this project, a Venetian blind slat with a white top surface and a brushed aluminum bottom surface was optically characterized. A goniophotometer and an integrating sphere spectrophotometer were used to determine the angle resolved and hemispherical reflectance of the sample, respectively. The acquired data were fitted to a scattering model providing one Lambertian and one angle dependent description of the surface properties. These were used in combination with raytracing to obtain the complete BSDFs of the Venetian blind system.

Place, publisher, year, edition, pages
2010. Vol. 84, no 12, 2103-2111 p.
Keyword [en]
ABg-model, BSDF, Raytracing, Venetian blinds
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-139621DOI: 10.1016/j.solener.2010.09.005ISI: 000285125900013OAI: oai:DiVA.org:uu-139621DiVA: diva2:381791
Available from: 2010-12-28 Created: 2010-12-28 Last updated: 2016-04-19Bibliographically approved
In thesis
1. Daylighting Systems: Development of Techniques for Optical Characterization and Performance Evaluation
Open this publication in new window or tab >>Daylighting Systems: Development of Techniques for Optical Characterization and Performance Evaluation
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Successful integration of daylighting systems requires the ability to predict their performance for given climates. In this dissertation, a bottom-up approach is applied to evaluate the optical performance of a selection of daylighting systems. The evaluations are based on the optical properties of the included materials, and part of the dissertation focuses on developing new optical characterization methods.

The work on characterization techniques uses an integrating sphere method to characterize the transmittance of light scattering samples more accurately. The method's principle is to reduce the discrepancy in light distribution between the reference and the sample scans by using an entry port beam diffuser. For samples exhibiting distinct light scattering patterns, the benefits of improved uniformity outweigh the errors introduced by the diffusing material. The method is applicable to any integrating sphere instrument, and its simplicity makes it suitable for standard measurements.

In addition to normal-hemispherical properties, many daylighting applications require knowledge of the system's spatial light distribution. This dissertation presents a method combining experimental techniques and ray tracing simulations to assess the light distribution from a Venetian blind system. The method indicates that ray tracing based on simplified optical data is inadequate to predict the light distribution for slat materials exhibiting both specular and diffuse properties.

Ray tracing is a promising complement to experimental methods used to characterize light guiding or light redirecting systems. Here, spectrophotometric measurements of a scaled mirror light pipe validate a ray tracing model. The model shows excellent agreement with experimental results for both direct and diffuse incident light. The spectral evaluation shows no dramatic color changes for the transmitted light. The ray tracing model is used to evaluate four daylighting systems for a selection of Swedish locations. The percentage of occupied time when the studied systems achieve full design illuminance is relatively low, but the systems provide a valuable contribution to the required illuminance.

Additionally, this dissertation provides an overview of available energy efficient windows and illustrates the importance of including the solar energy transmittance when evaluating window energy performance.

Overall, this dissertation presents optical characterization techniques for improved performance evaluations of daylighting systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 157 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 987
Optical spectroscopy, integrating sphere, ray tracing, light scattering, window physics, Venetian blinds, core daylighting, optical characterization
National Category
Engineering and Technology
Research subject
Engineering Science
urn:nbn:se:uu:diva-183307 (URN)978-91-554-8512-2 (ISBN)
Public defence
2012-12-07, Polhemsalen, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Available from: 2012-11-16 Created: 2012-10-24 Last updated: 2013-01-23Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Nilsson, Annica M.
By organisation
Solid State Physics
In the same journal
Solar Energy
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 409 hits
ReferencesLink to record
Permanent link

Direct link