C. Roecker

Experimental assessment of bi-directional transmission distribution functions using digital imaging techniques

Many daylighting applications require a precise knowledge of the directional transmission features of advanced fenestration materials. These photometric properties are described by a bi-directional transmission distribution function (BTDF), whose experimental assessment requires an appropriate equipment. A novel bi-directional photogoniometer, based on digital imaging techniques, has been designed and developed for that purpose. The main advantages of this device are the significant reduction of the time required for data measurement and its capability to assess an almost continuous BTDF function. These features can be achieved only through detailed and accurate calibration procedures of the bi-directional photogoniometer, which are described in this paper, together with digital image and data processing. Several experimental results, obtained for different fenestration materials, are used to illustrate the capabilities of this novel equipment.

Facade Integration of Solar Thermal Collectors: A Breakthrough

One main barrier to the acceptability of facade use of solar thermal collectors is their black appearance and the visibility of piping or absorber irregularities through the glazing. To facilitate facade integration, a project was set up to develop selective filters reflecting only a small part of the solar spectrum in the visible range while letting the rest of the radiation heat the absorber. These filters were successfully produced and, combined with a diffusing glass treatment, have achieved the desired masking effect with minor impact on the collector efficiency (less than 10%). Glasses of various colours combined with several diffusing finishing (acid etching, structured glass etc…) can be produced that are able to hide the absorber. Such glazings will allow the use of the same product both in front of facade areas equipped with solar absorbers (as collector external glass) and in front of the non exposed areas (as facade cladding), opening the way to a broad variety of active facade designs. The active elements can then be positioned at will on the exposed areas, and their quantity determined only by thermal needs. By freeing the dimension of the facade area that can be clad with this glazing from the thermally needed surface for collectors, a major step to help architects use solar thermal on facades has been taken.

Innovative solar products for architectural integration: a joint Task 41 and Task 51 IEA website

Keywords: architectural integration ; solar products ; photovoltaics ; solar thermal Reference EPFL-CONF-206307 Record created on 2015-03-12, modified on 2016-08-09

Web-site: Innovative solar products for architectural integration

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