The influence of photometric coating on spectral reflectance of artificial sky dome

The artificial sky has been in operation at the Institute of Constructions and Architecture of Slovak Academy of Sciences in Bratislava since 1970's. This artificial sky provides lighting simulations in conditions of overcast sky mainly for daylighting measurements in physical scaled models. It has been used for wide spectrum of photometric measurements ranging from scaled building interiors to light distribution using tubular light guides. The sky dome was made of reinforced concrete and is suspended to loadbearing structure of the surrounding building on steel ropes. It is hemispherically shaped with diameter of 8 meters. Thanks to support of grant scheme APVV the lighting system in artificial sky is undergoing the total reconstruction. The part of this reconstruction contains the renewal process of the dome's surface through applying special photometrical coating, developed especially for this purpose in cooperation with company Chemolak a. s. Smolenice, Slovakia. The other part of reconstruction consists of new LED lamp installation in combination with the new electrical installations and new controlling and calibration programming system. This paper deals with comparison of spectral reflectance of dome's surface before and after application of new photometrical coating to determine inputs for simulation of CIE Standard General Sky in laboratory conditions. The experimental results show the quite high rate reflectance values and uniform - spectrally neutral reflectance properties. The surface also meets the desired requirements regarding the diffuse light reflectance. The aim of lighting system reconstruction is to improve spectral rendering of new lighting system, to decrease consumption of electricity and enable to simulate of all 15 types of the CIE Standard General Sky, which are adopted by ISO and CIE in ISO 15409:2004/CIE S 011/E:2003.