Integrating non-visual effects of light in the automated daylight-responsive control of blinds and electric lighting

The use of daylight in buildings is important because it contributes to energy savings by reducing the use of electric lighting and space heating. It also impacts on biological functions and on well-being. Indeed, light not only allows vision, but has non-visual effects on human physiology: for instance, light is the primary time cue for the circadian entrainment of the biological rhythms to the 24-hour environmental time.This thesis is focused on two aspects: the automated control of daylighting in buildings, and the examination of its impact on non-visual functions in a semi-realistic office study. The overall hypotheses for this thesis were that a strategy including a daylight-responsive automated control for indoor lighting combined with an advanced daylighting room design is beneficial for non-visual functions, it can maintain sound visual comfort and low electric energy demand. The main aims of this work were: 1) to set-up an automated controller for integrated daylight and electric lighting; 2) to test its effects on circadian rhythms, cognitive performance and visual comfort in a study with young participants, and 3) to evaluate its impact on energy demand. To achieve the first aim, an automated controller for venetian blinds and electric lighting was designed to provide optimal indoor lighting conditions following dynamic preset target levels of illuminance. The controller was based on real-time assessment of lighting conditions by high dynamic range vision sensors placed next to the desk at the eye level. Next, the controller was implemented in a well daylit office room (Test room) and compared with a Reference room corresponding to a standard working space without automated control. A total of 34 young participants spent five consecutive days (8h/day during normal office hours) in each of the two rooms. Lighting conditions in the room were continuously monitored, and individual light exposures were recorded by wearable devices. Several physiological outcome measures (sleep/wake times, salivary hormonal concentrations, skin temperatures) were obtained. Simultaneously, cognitive performance (on auditive computer tasks), as well as subjective comfort and well-being were repeatedly assessed. The results showed that vertical illuminance was significantly higher in the Test than in the Reference room, especially in the morning hours until the early afternoon, while visual comfort was always ensured. The higher illuminance in the first part of the day led to a faster accumulation of the daily light dose: 50% of the maximum accumulated illuminance was reached on average 50 minutes earlier in the Test than in the Reference room.Concomitantly with higher illuminance, the timing of the circadian rhythms (assessed by the onset of melatonin secretion and peripheral heat loss through the skin) was advanced by approximately 20-30 minutes in the Test room. On the other hand, participants overall performed better in the Reference room, especially in summer. The total electricity demand for space heating and lighting decreased by 9.6% in the Test room with respect to the Reference room.To summarise, these findings indicate that the lighting strategy had phase-advancing effects on circadian rhythms, which might be a useful real-setting treatment for circadian sleep-wake disorders which have become more frequent in young adults nowadays. Further work is needed to establish optimal lighting for cognitive performance across different seasons.

Integrated Daylighting and Artificial Lighting Control based on High Dynamic Range Vision Sensors

Ali Motamed

One fifth of the electricity consumption of Swiss buildings is due to electric lighting. Integrated control of sun shading and artificial lighting can mitigate this demand while maintaining user comfort. However, the drawback of existing building control approaches is that they do not consider one of the main aspects of human-centric lighting: visual comfort. The goal of this doctoral thesis is to develop an integrated energy efficient sun shading and electric lighting control system that incorporates widely accepted visual comfort criteria and privileges daylighting over electric lighting. The first part is dedicated to High Dynamic Range (HDR) vision sensor calibration, programing, validation and preliminary testing. A sensor originally developed by the Centre Suisse dâElectronique et de Microtechnique (CSEM) was photometrically, spectrally and geometrically calibrated and validated with respect to reliable illuminance and multi-point luminance meters. This HDR vision sensor was then equipped with an embedded image processing routine in order to assess âon the flyâ discomfort glare indices. It has been demonstrated that the developed device, is able to serve as an enhanced visual comfort feedback sensor in building automation systems. On the other hand, it can be employed to characterize highly glazed facades and workspaces regarding visual comfort and glare risks, as demonstrated in a project in Singapore. Two monitoring campaigns are reported in the second part of this thesis. Firstly, 30 human subjects occupied two identical office rooms of the LESO solar experimental building for 15 afternoons to compare the performance of a fuzzy logic control system incorporating two HDR vision sensors with respect to a âbest-practiceâ controller. Subjective self-reported visual comfort surveys, paper- and computer-based visual tests and monitoring of the electric lighting consumption were carried out simultaneously in both offices. It was shown that the electricity demand of the office with the advanced controller is 32% lower than that of the reference room, while the subjectsâ visual performance remained comparable. Secondly, an eight-month data monitoring campaign was carried out in the same building in order to study the ability of a novel control approach to maintain optimal visual and thermal comfort conditions while reducing the energy performance gap of a room as well as its electric lighting demand. The experimental results showed that the advanced controller mitigated the performance gap during the heating season by 72% with regard to standard occupant behavior and by 19% with respect to a best-practice automated system. This system reduced backup heating demand leading to lower CO2 gas emissions. At the same time, visual comfort constraints regarding Daylight Glare Probability (DGP) and workplane horizontal illuminance were respected during work hours. Finally, a self-commissioning integrated controller for Venetian blinds enhanced with a learning module was developed and validated for 22 days in a daylighting testbed at the Fraunhofer Institute for Solar Energy (ISE) in Freiburg, Germany. It has been shown that the visual comfort constraints are respected for 96% of the work hours and that the controller can successfully limit the number of shading movements. The market potential for HDR vision sensors and integrated control platforms has been studied and possible commercialization tracks have been identified.

EPFL2017

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

Daylight optimization of buildings and application of advanced daylighting systems in Central Mexico

Chantal Basurto Dávila, Apiparn Borisuit, Jérôme Henri Kämpf, Mirjam Münch, Jean-Louis Scartezzini

The intensive use of daylight in buildings is beneficial at many levels: it provides sufficient levels of illumination to perform working activities throughout the day and it reduces the use of artificial light, which in turn leads to lower electricity consumption [1-3]. The spectral composition of daylight often leads to higher visual comfort in humans, compared to electric lighting. There are also illuminance and spectrally-dependent light effects on the human circadian system, which regulate hormonal rhythms, alertness and (visual) performance across 24 hours [4-6]. The main objective of this work was to assess luminous performance in office buildings and to test optimizations by virtually applying different daylighting strategies by computer simulations.We first assessed the daylight distribution in two different office rooms, set-up as test modules on the EPFL campus in Lausanne (46° 32'N, 6° 39'E). One of these test modules is equipped with a standard double-glazing; the second one comprises anidolic daylighting systems [7], which convey diffuse daylight and sunlight deeper in the room, and reduce glare risk. In both rooms, we also assessed vertical spectral irradiance in the visible range, which gave us additional information with respect to photo biological properties of the available daylight. We then measured the real daylighting situation in an office room located in the city of Zacatecas, Mexico (22°47'N 102°34'W), which is equipped with a standard double-glazing window. In a next step we tested, whether the daylight distribution for this room could be improved by virtually applying different complex fenestration systems (such as prismatic panels and laser cut panels) by using computer simulations. The results of these simulations showed higher indoor luminous performance with the two advanced daylighting systems. This new method may contribute to an improved and tailored design of daylight availability in real buildings at different geographical locations.