A simulator based on LED technology to study daylight on architectural scale models

The Strasbourg School of Architecture (ENSAS) developed a daylight simulator applied to architectural scale models. It reproduces both direct sunlight and diffusing light from the sky. Because LED technology offers a possible control of each source, it is no longer necessary to build the sky with a dome shape. Therefore we chose a cubic shape. RGB LED sources are fixed on a white panel behind a lambertian diffuser. To reach a uniform lighting on the technical platform, the system has to be calibrated. The objective is to define the correction table to be applied to the artificial sky. After calibration in such a sky, the luminous flux of each source will have the same contribution to the centre of the experimental platform. Initial results have shown that the application of a theoretical correction function does not provide uniform illuminance. These first counter-intuitive results led to investigate several configurations which showed that the inter-reflection between the walls represent about 20% of the illuminance measured inside the simulator. Finally, because of these inter-reflections, the intensity of the LEDs in the corners should be reduced by around 10%. To respect a lighting ratio of 6 between the sun and the sky, the intensity of the artificial sun has been adapted.