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A new model for smart windows with movable plane mirror-arrays as a basis for energy minimizing control

: Schwank, A.; Schmid, J.; Maas, A.

International Solar Energy Society -ISES-:
30th ISES Biennial Solar World Congress 2011. Vol.3 : Kassel, Germany, 28 August - 2 September 2011
Red Hook, NY: Curran, 2011
ISBN: 978-1-618-39364-7
Solar World Congress (SWC) <30, 2011, Kassel>
Conference Paper
Fraunhofer IWES ()

A new model, called solREflexiq, to evaluate the energy related effects of specular, plane, and arbitrary oriented solar-redirection systems is introduced. It also consists of an algorithm for the distribution of solar flux into the building which is comparable with other algorithms that are already in use. It is a mixture of methods: ray tracing, radiosity, and balance of areas. solREflexiq is one step to link the effects of daylight distribution, thermal effects, and other side conditions in order to find an energy-optimized control strategy and to evaluate the whole year energy effects of those systems. The approach is motivated by the development of micro-mirror-arrays and uses their geometrical relations as an example. The plausibility contains mainly the comparison between visual and numerical analysis. It gives an idea of the possibilities for analysing the properties of these kind of structures. It showed that, even for horizontally oriented solar-redirection sy stems, a 2-dimensional analysis is not accurate for steep azimuth angles. Following visual and numerical analysis there is a substantial influence of the azimuth angle to the transmission properties. The validation of solREflexiq with Radiance showed a relatively high relative error for the irradiance distribution on the reference plane. The assumption was approved that this deviation was a result of the neglected secondary reflections of the floor and the walls. Subtracting those reflectances in Radiance, the comparison of the results shows a very similar shape and a low relative error throughout the whole room. This leads to the result, that the algorithm for the mirror-arrays and for the distribution from the ceiling to the reference plane is validated. The algorithm for the other secondary reflectance has to be improved. As a result a solar-transmission field dependent on the solar altitude and the mirrors setting angle was extracted. This shows the analytical possibilities of solREflexiq offeri