Energetic, Visual and Non-Visual Aspects of Office Lighting

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.

Building envelope and solar energy optimization: a new “wizard” for architects

Marja Edelman, Maria Cristina Munari Probst, Christian Roecker

When designing a project, architects are facing more and more constraints on the building’s energy efficiency. Tougher values on insulation and energy consumption are now often combined with compulsory implementation of active solar systems - photovoltaics or solar thermal. With natural lighting, passive and active solar all competing for envelope areas, comparing results of architectural variants becomes more important and at the same time more complex. To help overcome this situation, a renowned “energy balance calculation/certification” software tool has been improved and adapted, proposing a wizard developed to meet a growing demand: obtain a quick feedback on building envelope, energy efficiency and solar strategies, especially in the early design stage, when strategies are defined. The wizard helps fulfilling various norms of different European countries, allowing architects to compare variants during this crucial phase. By simplifying data entry using smart default values derived from appropriate general choices, and by presenting a clear and intuitive user’s interface, this new tool offers practicing architects an easy access to building envelope and solar energy use optimization.

Université Catholique de Louvain-la-Neuve2011

Efficient lighting strategies for office rooms in tropical climates

Friedrich Linhart, Jean-Louis Scartezzini

The “Green Lighting” research project, initiated at the Solar Energy and Building Physics Laboratory (LESO-PB) of the Swiss Federal Institute of Technology in Lausanne (EPFL), is aiming at an energy efficient integration of advanced daylighting and electric lighting systems. This communication presents the latest developments within this project and discusses possible consequences for offices in tropical climates. A computer model of a Singapore office room equipped with an Anidolic Integrated Ceiling, for which daylight autonomies have recently been calculated at National University of Singapore, has been developed using the RELUX Vision lighting software. An appropriate complementary electric lighting system for this office room is suggested and its performance in terms of visual comfort is discussed. It is shown that this electric lighting system would lead to a lighting power density lower than 5 W/m² and would consume less than 1 kWh of electricity per day.

2007

Optimal integration of daylighting and electric lighting systems using non-imaging optics

Friedrich Linhart, Jean-Louis Scartezzini

Electric lighting is responsible for a significant fraction of electricity consumption within non-residential buildings. Making daylight more available in office and commercial buildings can lead as a consequence to important electricity savings, as well as to the improvement of occupants’ visual performance and wellbeing. Over the last decades, daylighting technologies have been developed for that purpose, some of them having proven to be highly efficient such as anidolic daylighting systems. Based on non-imaging optics these optical devices were designed to achieve an efficient collection and redistribution of daylight within deep office rooms. However in order to benefit from the substantial daylight provision obtained through these systems and convert it into effective electricity savings, novel electric lighting strategies are required. An optimal integration of high efficacy light sources and efficient luminaries based on non-imaging optics with anidolic daylighting systems can lead to such novel strategies. Starting from the experience gained through the development of an Anidolic Integrated Ceiling (AIC), this paper presents an optimal integrated daylighting and electric lighting system. Computer simulations based on ray-tracing techniques were used to achieve the integration of 36W fluorescent tubes and non-imaging reflectors with an advanced daylighting system. Lighting power densities lower than 4 W/m2 can be achieved in this way within the corresponding office room. On-site monitoring of an integrated daylighting and electric lighting system carried out on a solar experimental building confirmed the energy and visual performance of such a system: it showed that low lighting power densities can be achieved by combining an anidolic daylighting system with very efficient electric light sources and luminaries.

2007