Improving energy saving evaluation in lighting using daylight utilization with area segregation technique

Abstract

Lighting control is one of the key areas for energy saving in lighting system. Automatic control systems reduce energy consumption by decreasing load and operating time of lamps based on various factors like occupancy, time and daylight illuminance. Daylight-linked control systems can provide substantial savings in rooms with daylight availability. This approach to energy saving is called Daylight Utilization. Different methods to estimate energy savings from daylighting exist. The existing methods use simulations along with complex calculations which are suitable for research projects, but difficult to adopt for electrical designers. Moreover, some issues within these methods prevent them from estimating the maximum potential of savings. Particularly, these methods often consider the whole room as one workplane, whereas in reality the actual task area is considerably smaller. Also, the existing methods take annual average daylight penetration without considering variation of daylight penetration throughout the day or year. These problems lead to inaccurate assessment and ultimately reduced savings. This study aims to develop a new method using simulation data that considers segregation of the workplane and daylight variation for improved daylight utilization assessment. The proposed method uses two approaches to overcome the above problems of previous studies. Firstly, dividing the workplane of the room into task and surrounding area, and associating different illuminance level requirements for the two areas. Secondly, dividing the daylight penetration into three different ranges of daylight illuminance levels, thus taking into account variation in daylight illuminance. The method was applied on the simulated model of a small office room, and the annual savings potential was found to be 83.67%. The results show that the proposed method gives estimation of 73.45% savings for an office room, which is 10% higher than the results of an existing method. This shows that the new method is a viable solution for estimation of energy savings potential from daylighting.