Development of Sky Luminance and Daylight Illuminance Prediction Methods for Lighting Energy Saving in Office Buildings

Abstract

Accurately predicting indoor illuminance from daylight during the early stages of building design is an important factor in saving energy and the costs associated with lighting. The objective of this study was to predict sky luminance distribution using the Commission Internationale de l’éclairage (CIE) standard sky model, and propose a method that can be used to predict indoor illuminance. Results obtained from the proposed prediction method were compared and verified with simulation values obtained by Desktop Radiance. From the CIE overcast sky, the zenith/horizon ratio was 3:1. From the CIE clear sky, the luminance value was highest around the sun. In contrast, the luminance value was lowest in the opposite direction of the sun when the angle between the sun and sky elements was 90°. In addition, this study suggested an indoor illuminance prediction method by applying the effects of sky luminance, direct sunlight, and wall reflection elements. When the proposed equation’s calculation results were compared with Desktop Radiance simulation’s value in overcast and clear sky, all statistically analysis (R2, MBE, Cv(RMSE), t-value, p-value) satisfied each standard and showed high correlations. Consequently, it was established that the predicted indoor illuminance obtained from the proposed prediction method was accurate and can be used to predict the level of indoor illuminance. The results further revealed that it is possible to calculate indoor illuminance when installing blinds, by substituting variable values of visible light transmittance (VLT).

Evaluation of the Existing Solar Energy and Rainwater Potential in the Total Roof Area of Buildings: Izmit District Example

“…e use of daylight in buildings increases visual comfort and decreases ultimate energy demand for artificial lighting [46]. With the energy saving methods that are applied to the lighting systems of buildings, energy Advances in Materials Science and Engineering consumption decreases considerably [47,48]. In order to reach the desired lighting levels by transmitting daylight into the areas lacking daylight in buildings as much as possible and decrease electricity expenditures, not using lighting in the buildings in the day hours but using direct daylight through light tubes from the roofs is of great importance for sustainability (Figure 2) [49,50].…”

Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution

“…They have been considered among the communities of different areas such as electrical, chemical, or mechanical engineering. In the area of lighting technique, the ecological trends have also been easily visible [1][2][3][4][5][6]. Within these trends, one of the problems taken into account by researchers is the problem of light pollution, which is associated with the lighting of outdoor areas.…”

“…As a result of one of the priority actions of the European Union (EU), authorities are obligated to reduce electricity consumption, and an important branch of electricity, where this aspect is considered, is electric lighting. The effect of the actions made by the EU is a process of withdrawing energy-consuming light sources and promoting the introduction of modern light sources like light-emitting diodes (LEDs) [4,21,22]. For this reason, LED sources are also considered as the light sources possible to be installed in the opal sphere type luminaries.…”

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“…Natural light significantly influences the balance of energy use in buildings and actual human activities. Accurate estimation of daytime lighting in a room is important in saving lighting energy because daytime lighting data in a room can be used to predict the lighting energy of a building and improve energy efficiency [3].…”