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Jacobs, Axel (2009) One-lamp artificial sky. Doctoral thesis, London Metropolitan University.
The assessment of the daylight performance of a building is often carried out with architectural scale models in an artificial sky. The commonly used mirror box artificial skies can only reproduce CIE overcast conditions, while the more configurable sky simulator domes are expensive to built and maintain and occupy a large space. This work proposes a new type of artificial sky in a one-lamp configuration. The theory of operation of such sky simulators, which is based on the principle of the daylight coefficient, is developed. A prototype of this new type artificial sky has been designed e and built in the LEARN lighting laboratory. The new one-lamp sky provides a number of advantages over traditional ones. This is because individual sets of measurements are taken for illumination from different parts of the sky. Those measurements are analysed and exploited through the application of what is known as climate-based daylight analysis. This new field of daylight research is based on the use of historical climate data making predictions of the building's daylight performance far more realistic than those based on theoretical sky conditions. It has been applied to data derived from virtual measurements with lighting simulation software. This thesis demonstrates that it can also be used with measurements in scale models under this new artificial sky. Scale models investigations have traditionally been limited to illuminance measurements. The new technique of high dynamic range, HDR, photography allows for the photometric calibration of images obtained with a digital camera resulting in accurate pixel luminance data. Methods of calibrating digital cameras for accurate photometric representation of the luminous environment are developed. The HDR technique is employed for measuring the luminance across interior surfaces of the scale model. The same climate-based analysis that is developed for illuminance measurements is applied to HDR luminance data.
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