Detailed simulations of lighting conditions in office rooms lit by daylight and artificial light

Abstract

In this thesis the effect on the annual artificial lighting demand is investigated by employing detailed simulations of lighting conditions in office rooms lit by daylight and artificial. The simulations of the artificial lighting demand is accomplished through daylight simulations in Radiance. The detailed simulations includes studies of the resolution of different weather data sets in climate-based daylight modeling. Furthermore, influence of the electrical lighting demand by simulating with dynamic occupancy patterns is studied. Finally the thesis explores the influence of obstructions in an urban canyon on the daylight availability within the buildings, and hence on the energy consumption for artificial lights. The results from the thesis demonstrates that the effect on the outcome of the daylight simulations when simulating with typical weather data files for the location of Copenhagen is insignificant. Each of the different weather data sets where found to give a reasonable prediction of the lighting dependency. Furthermore the effect of simulating with weather data sets of an hourly resolution opposed to a one minute resolution showed that the lighting dependency was underestimated when using weather data sets of hourly means. However, the findings from this study show that the dynamic, short-term effects of the weather data applied, have a surprisingly small impact on the simulation outcome. At present, using values of hourly means for the daylight simulations is therefore a reasonable predictor for the lighting dependency. Secondly, the thesis demonstrates that no real difference is seen in simulation results of the artificial lighting demand when the artificial lights are controlled automatically dependent on presence of occupancy and daylight level, applying occupancy profiles as annual average, hourly resolution or occupancy presence of two minute resolution. Comparison between the lighting demand for artificial lights by applying a diversity factor opposed to dynamic occupancy profiles showed a difference in lighting demand of 4 %, and the evaluation of the saving potential is therefore slightly conservative. A simple method based on the vertical daylight factor, daylight factor and CIE overcast sky has been presented with the aim being to facilitate the urban design process. By looking at the influence of the surroundings on the daylight factor within the room followed by a categorization of the facades according to their daylight performance it is possible to point out urban areas that are good in terms of daylight inside the buildings and areas that have a poor daylight performance. The results from the dynamic investigations of the influence of obstructions on the daylight availability show that in dense cities the orientation of the buildings has a minor importance. However, the results indicate that there is a preference for the northern orientations in terms of daylight availability at the lower oor plans. Using finishes of high reflectivity on the opaque part of the street facades increased the daylight penetration depth for the lower floor plan.