Abstract:
A daylight-linked photo sensor is a measures employed for interior lighting energy saving. Previous literature reveals that its efficiency depends on various factors such as location and glass specification. However, no studies have been conducted on the reflectance of interior surfaces. This study, therefore, aims to investigate the relationship between the reflectance of interior surfaces and the efficiency of a daylight-linked photo sensor and to find the break-even point. A computer program was used to collect data of interior lighting quality in a 3.5 x 5.4 x 2.7-meter simulation office. The room had six one-inch-diameter 36-watt fluorescent light bulbs, some controlled by an on/off switch and the others equipped with a light dimmer. This study consists of three parts. First, it explores the daylight index in the simulation office using the DIALux 4.8 program and finds that the reflectance of interior surfaces changed from 0.10 to 0.90 in all cases. Second, it studies energy consumption along with the use of a light sensor. The study compares the use of light bulbs with and without a daylight-linked photo sensor in different directions and times of year. Last, it gives the break-even point analysis considering an electronic device with and without the photo sensor and discusses the break-even point of using the photo sensor, considering different degrees of reflectance of interior surfaces. Findings suggest that offices with high reflectance of interior surfaces consume less lighting energy than those with lower reflectance. The use of a photo sensor can therefore result in energy savings of from 48 to 62%. Considering the break-even point, after taking into account both energy and device costs, offices with open space on the north ,east and west side should install a photo sensor with considering the high reflectance of interior surfaces.