EVALUATION OF DAYLIGHT CONTRIBUTIONS IN THE DESIGN OF LIGHTING FOR LECTURE THEATRES

Abstract

Daylight is a comfortable source of natural light nowadays called renewable energy with variations in luminosity. This research evaluated effectiveness of daylight contributions in lighting design of selected lecture theatres in Federal University of Technology, Akure (FUTA), Nigeria and its cost implications. Five years’ empirical solar radiation data were collected from Nigeria metrological agency (NIMET). Using existing model, the visible radiation was obtained from solar radiation, measured data were collected using measuring tape for dimension of the buildings and TES 1332A digital lux meters for indoor daylight lux level contributions in the buildings under different time of the day between (8:00 am to 6:00pm). Room index method and Random method were used to determine the number of measuring points. The daylight factor of the building was determined for computing the daylight contribution in each building. Correlation statistics was used to evaluate and analyze the average measured and computed daylight contributions. The luminaries needed in each of the building was computed using lumen method and the cost of energy per building was obtained. A model that incorporate daylight in lighting design was developed. The results revealed that room index method is more reliable than random method in determining the number of measuring points for indoor lux level determination. 22 % window area to wall area is considered moderate, 37 % window area to wall area is considered more suitable. The minimum lux of 12 is considered poor for lecture theatre while 21 and 28 lux is moderate and more adequate for lecture activities respectively. For the average lux level, 14 is poor for lecture activities while 80 and 113 lux is moderate and more adequate respectively for lecture activities. Also, based on the developed model, the results show that 3-in-1-A building did not requires artificial lighting during the day at all. viFBN needs artificial lighting in the evening and 1000 capacity needs artificial lighting in the morning and evening. it implies some luminaries should be connected to control circuit in order to save energy. Daylight incorporation in this work saves 21.6 % to 100% of energy. The cost of daylight contribution in the three buildings is largely significant, 1.5 million per year, and 47.1 million naira for 30 years amounting to 51.4% of the expected lighting charges for a year and 30 years in this work. A proposed model with effective control established in this work saves substantial cost of energy. The proposed model should therefore be used in lighting design for lecture theatres in order to reduce energy comsumptrion