사무소 건물의 조명제어를 위한 천장면 조도 특성에 관한 연구

Abstract

In modern office buildings, the lighting control is significant not only to provide the comfortable visual environment but also to reduce the energy consumption in buildings. For efficient lighting control, it is necessary to control lighting output according to the illuminance on the work plane; however, it is difficult to directly acquire the work plane illuminance because it is practically impossible to install the light sensor on the work plane and the occupant’s activities can affect the measured illuminance. For this reason, this study attempted to measure ceiling surface illuminance to control the illumination on the work plane. To verify this assumption, experiments and simulation were conducted to investigate the relationship between the illuminance on work plane and ceiling surface. To fulfill the purpose of this study, a test-bed was constructed in order to analyze the illumination in typical office space. In addition, an Arduino-based illuminance sensors and recording system were also developed in order to acquire the simultaneous illuminance distribution on the work plane and the ceiling surface. Forty illuminance sensors combined with wireless signal transfer system were constructed to facilitate the data measurement and acquisition. The developed measurement system was verified by comparing the result with those of the general-purpose illuminance meter, which has been already by other researchers. The by other researchers results showed that the accuracy of the Arduino-based measurement system is approximately 99.6% compared with the verified illuminance meter, which indicates that the developed measurement system could be successfully used to investigate the relationship between illuminance on work plane and ceiling surface. In order to quantify the relationship between illuminance on work plane and ceiling surface, the illuminance ratio of ceiling surface to work plane was suggested in this study. Test-bed experiment results showed that the ratio ranges from 0.26 to 0.55 (average of 0.37), implying that such ratio can be used to determine the proper position of the illuminance sensor on the ceiling surface. As the above-mentioned illuminance ratio will be affected by the reflectance of the wall, which has relatively large surface area in the space, it is necessary to investigate such ratio with other types of walls which has reflectance. Thus, the illuminance on work plane and ceiling surface was measured by applying three different wall papers with the reflectance of 0.834, 0.672, and 0.536, respectively. In addition, the measured illuminance data was compared with the Relux simulation, which was conducted to investigate the relationship between illuminance on work plane and ceiling surface under more various room conditions such as wall reflectance. The discrepancy between measured and simulated illuminance was –5∼10% for work plane and –13∼10% for ceiling surface, respectively Therefore, it was found that the developed simulation model is suitable for the analysis of the illuminance ratio with different wall reflectance. Using the simulation model, the correlation between wall reflectance and the illuminance ratio was analyzed. It was found that the correlation can be formulated with the regression equation Y = 0.1243X2 + 0.1534X + 0.1169 (R2 = 0.9993), where X is the wall reflectance and Y is the reflectance ratio. The derived regression equation can be used to determine the appropriate sensor position to control artificial lighting based on the ceiling surface illuminance. As the regression equation was derived under the condition that the daylight is not introduced into the space, it may not be applicable to the space with the natural lighting. Therefore, in order to extend the applicability of this study, it was necessary to investigate the impact of natural lighting on the illuminance ratio. For this reason, additional experiments were conducted by introducing direct and indirect daylight in the test-bed space. It was found that the daylight tends to elevate the overall illuminance on work plane and ceiling surface, which also affects the illuminance ratio. Thus it is necessary to conduct more comprehensive study to quantify the impact of the natural lighting on the illuminance ratio under various outdoor how about the effect caused by the indirect daylight.