A Basic Study on the Performance Evaluation of a Movable Light Shelf with a Rolling Reflector That Can Change Reflectivity to Improve the Visual Environment

Abstract

In recent years, the need for comfortable visual environments in indoor spaces has increased energy use in buildings. There have been diverse studies on using a light shelf to solve this problem. It is an effective system that allows external natural light deep into indoor spaces through reflection. However, prior studies have used light shelves with a fixed reflectivity, and there are few studies on improving the visual environment through light shelf control. Therefore, this study proposes a movable light shelf with a rolling reflector that can change the reflectivity. To achieve these objectives, we conducted a performance evaluation of the system’s ability to save energy and improve the visual environment. This study built a real scale testbed and conducted a performance evaluation by deriving values for lighting energy consumption, uniformity, and luminance contrast depending on the light shelf variables. We conclude that (1) the light shelf system achieved an energy savings of 13.6% and 5.7%, respectively, compared to a fixed type light shelf, whose reflectivity cannot be changed, and a traditional movable light shelf; (2) in terms of improving the visual environment, results suggest that the visual environment could be improved using a light shelf by deriving light shelf variables that disturb indoor uniformity; and (3) the results verified glare generation conditions by deriving luminance contrast caused by the variables of light shelf angle and its reflectivity.

An Evaluation of Useful Daylight Illuminance in an Office Room with a Light Shelf and Translucent Ceiling at 51° N

“…• use of a diffusion sheet [26] • evaluation of a light shelf based on energy consumption [27] • light shelf with a solar module [28] • light shelf based on reflector curvature [29] • application of a prism sheet [30] • movable light shelf with a rolling reflector [31] • light shelves with photovoltaic modules [32] Avila-Zamora and Murillo-Quirós experiment • three different anidolic systems were evaluated (anidolic ceiling, integrated anidolic system, anidolic solar blinds)…”

“…In the following years till the current time, the team of Prof. Heangwoo Lee published 11 papers considering different aspects of a light shelf and its performance. Those papers feature a light shelf using diffused reflection [22]; a movable light shelf system [23]; an awning system with a built-in light shelf [24]; the use of a diffusion sheet [25]; an evaluation of a light shelf based on energy consumption [26]; a light shelf with a solar module [27]; a light shelf based on reflector curvature [28] application of a prism sheet [29]; a movable light shelf with a rolling reflector [30]; and finally, in 2021, light shelves with photovoltaic modules [31].…”

A Review of Factors Affecting the Lighting Performance of Light Shelves and Controlling Solar Heat Gain

“…In this way, the reflection rate of the reflector is considered to be 97% in summer, spring and autumn and 85% in winter. The results show that changing the type of reflector throughout the year will have a significant effect on reducing energy consumption [25].…”

A Study of Optimal Specifications for Light Shelves with Photovoltaic Modules to Improve Indoor Comfort and Save Building Energy

“…Among these technologies for saving building energy, a light shelf is a typical natural daylighting system that works as building envelope element technology installed in windows to introduce external natural light deep into a room through the use of reflection. Various studies have confirmed the effectiveness of this technology [ 5 , 6 ]. Previous studies related to light shelves have expanded from performance evaluations with installation of light shelves to research integrating advanced information technology (IT), such as user recognition and location recognition technologies [ 7 , 8 ].…”

“…As shown in Table 1 , previous studies related to light shelves [ 5 , 6 , 7 , 8 , 12 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ] controlled the variables associated with light shelves or changed their shape to improve daylighting performance. Recent studies integrated various moving or operational technologies, including IT, and applied other elements to light shelves, such as awnings and PV modules.…”