# Design and Application of Daylight-Based Lighting Controller on LED Luminaire
## 2 Simulation  
The simulation of light distribution profile using DIAlux software has been done in two aspect. First part is the simulation on the on the case study room and the second part is the simulation on the experimental setup. The case study room has dimension of 8 m \(\times\) 12 m \(\times\) 3 m (width \(\times\) length \(\times\) height). The room consists of 9 windows with a size (not include frame) of 1 m \(\times\) 1.1 m. The overall layout of the case study room is shown in Figure 1.  
The result of daylighting on the case study room with only daylighting and with both daylighting and artificial lighting is shown in Figure 2a,b respectively and the summarizing result is shown in Table 1. The figure shown an example in case study room located in Bangkok, Thailand simulated at 10:00 AM. With clear sky on the 20 January 2020 in order to replicate the experimental setup case. The result in case of daylighting only shown that the illuminance value are high only in the area near the window and the daylighting cannot pass through the inner part of the room, thus reduce the uniformity of the lighting and the lighting quality cannot maintain at the commission on illumination (CIE) standard. However, the case study with both daylighting and artificial lighting has shown that the average illuminance on working plane is higher compare to previous case with high uniformity. In this case, it can be seen there has been excessive illuminance on the working plane. Thus, the daylight control can reduce light output of the luminaire and reduce energy consumption on lighting system. Figure 1: The overall layout of case study room modelling in DIALux software. Figure 2: \(Cont.\)  
The illuminance of daylighting on working plane in case of window-side of the room facing different direction can be summarized as shown in Table 2. From the table, it can be seen that buildings facing in the east and west directions will have a higher illuminance value compared to buildings facing in the north direction due to the pathway of sun movement. For the buildings facing the south direction, they have overall higher illuminance due to the location of simulate building (Bangkok, Thailand) alignment to the south of sun pathway. The illuminance value of the building facing east direction is higher in the morning and the building facing west direction has higher illuminance value on the evening. The result in terms of average illuminance has shown that during peak period daylighting can provide significant illuminance on working plane. However, the artificial lighting is still required in order to maintain the illuminance on working plane during the period that has low sunlight. To maintain illuminance within the international commission on illumination (CIE) standard at 300-350 lux, the artificial lighting does not necessary operate at maximum light output. Thus, the daylight control can be implemented to reduce energy consumption, while maintain lighting quality on the working plane. The simulation in second part is to evaluate the performance of an LED luminnaire and a T5 fluorescent luminnaire and their light distribution profiles on a working plane. The dimensions of the simulated room were 1 m in width, 2 m in length, and 3 m in height. Figure 3a illustrated the LED luminnaire (two sets of \(3\times 3\) W High power LEDs) location and its light distribution profile on a working plane 80 cm above the floor. Figure 3b illustrated the T5 luminaire (36 W T5 fluorescent) location and its light distribution profile on the same working plane. A comparison between the light distribution profile of the LED luminaire and that of the T5 fluorescent luminaire revealed that the light distribution profile of the LED luminaire was better because of the higher light output from the LEDs.