Energetic, Visual and Non-Visual Aspects of Office Lighting

Abstract

Light has important visual and non-visual effects on humans and high-quality light should therefore be supplied inside buildings in sufficient quantities. On the other hand, artificial lighting is responsible for a large part of an office building's electricity needs. It is thus important to take into account at the same time visual comfort, non-visual effects of light and energy-efficiency when designing lighting systems for office buildings. The general objective of this doctoral thesis was to combine knowledge from several scientific fields (e.g. daylighting technology, artificial lighting technology, lighting simulation and chronobiology) to discuss how sustainable lighting solutions (i.e. lighting solutions that are optimized in terms of energy-efficiency, visual comfort and performance as well as non-visual aspects of lighting) can be achieved in office rooms. A research strategy that used a test office room equipped with an Anidolic Daylighting System (ADS) as a starting point has been followed. This ADS was shown to be well-accepted by office occupants and to be able to supply sufficient daylight flux during large parts of most working days. Based on this ADS, a highly energy-efficient electric lighting system for complementary artificial lighting was developed and tested in a visual comfort and performance study with human subjects. In addition to that, the chronobiological properties of the test office room were assessed. It was shown that the ADS-equipped room performs extremely well under daylighting conditions in terms of non-visual aspects of office lighting. For the rare times when this is not the case, a back-up system for chronobiological lighting based on blue Light Emitting Diodes was developed. In order to get a deeper insight into chronobiological aspects of office lighting, a first applied chronobiological study at the Solar Energy and Building Physics Laboratory was initiated. Furthermore, possibilities to apply the concepts developed during this doctoral thesis to other types of buildings and other geographic regions were discussed. In conclusion, this doctoral thesis successfully demonstrated that it is possible to achieve sustainable lighting scenarios that are optimized in terms of energy-efficiency, visual comfort and performance as well as non-visual aspects by combining day- and electric lighting technologies in an appropriate way.