Advanced Window and Lighting Technologies in net Zero Energy Buildings

Light has an important visual and non-visual impact on humans. Most of our information exchange, especially within office working spaces, occurs through it, our circadian rhythms are directly influenced by its presence. On the other hand, artificial lighting is responsible for a large fraction of electricity consumption in non-residential buildings. The latter becomes even more dominant within net Zero Energy Buildings (nZEB) where yearly net heating and/or cooling loads are reduced almost to nil by the way of energy savings measures and renewable energy technologies. Anidolic Daylighting Systems (ADS) are very effective façade-integrated daylighting systems which can collect and redirect diffuse daylight deep into office rooms under almost any climatic conditions: several studies have demonstrated their efficiency in the Northern and Central European regions, as well in sub-tropical climates. Recent studies have shown that their integration with high efficacy electric light sources and efficient luminaries can lead to very low lighting power densities (e.g. 3 - 4 W/m2 instead of 12 – 15 W/m2), as well as an improvement of visual comfort, visual performance and contribution to human health. As such, they offer excellent opportunities to reduce the electric lighting load in solar buildings and nZEB. An integrated day- and electric lighting system has been implemented in the south-facing office rooms of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Objective visual performance and subjective visual comfort assessments were carried with 20 subjects, confirming the adequacy of this approach regarding human response factors, as well as from an energy savings perspective. A ceiling integrated anidolic daylighting system was also implemented last year in an nZEB, located in Singapore and erected through the refurbishment of an existing building. The system was based on a former study carried out on the EPFL campus by the way of a 1:1 scale mock-up office room equipped with a comparable device. Significant electricity savings, as well as visual comfort and performance improvement, were also observed in this case.

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

Optimal integration of daylighting and electric lighting systems using non-imaging optics - art. no. 667004

Friedrich Linhart, Jean-Louis Scartezzini

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2007

Minimizing connected lighting power in office rooms equipped with anidolic daylighting systems

Friedrich Linhart, Jean-Louis Scartezzini

Electric lighting is responsible for up to one third of an office building’s electricity needs. Making daylight more available in office buildings can not only contribute to significant energy savings but also enhance the occupants’ performance and wellbeing. Anidolic Daylighting Systems (ADS) are one type of very effective façade-integrated daylighting systems. All south-facing office rooms within the LESO solar experimental building in Lausanne (Switzerland) are equipped with a special type of ADS. A recent study has shown that these offices’ occupants are highly satisfied with their lighting environment. The most energy-efficient south-facing offices have a lighting power density of less than 5 W/m². The lighting situation within these “best-practice”-offices has been assessed using the RELUX Vision lighting software. Because this lighting situation is very much appreciated by the occupants, it was used as a starting point for developing a yet more energy-efficient office lighting design. Two new lighting designs, leading to lighting power densities of 4 W/m² and 3.1 W/m² respectively, have been suggested and simulated with RELUX Vision. Simulation results have shown that the performance of these new systems can be expected to be comparable to that of the current lighting installation within the “best-practice”-offices or even better.

EPFL2007