An experimental study of natural lighting for energy conservation using top-up control method

This paper presents the experiment-based analysis of interior illuminance from natural lighting through clear glazed window of a reference room located in Bangkok, Thailand, during February to May 2007 as a case study. The point illuminances measured by photoconductive sensors were collected every 5 minutes and the average interior illuminance from natural lighting were then calculated instantaneously. In this study, natural lighting also aims to reduce the requirement of electric lighting during daytime (7 am-5 pm) of the reference room. If natural lighting alone cannot supply the light at the required value, the electric lighting is assumed to be switched on under top-up control method to maintain the standard illuminance level. The average interior illuminance, which comprises of natural light and electric light, is controlled to be stable at the IES standard level of 500 lux. Nine sets of high performance lamp, 56 lm/W of efficacy, are assumed to supply the light to meet the standard condition. The requirements of supplementary lighting and possible savings during the test months are finally estimated.