Preliminary Study on the Performance Evaluation of a Light Shelf Based on Reflector Curvature

Abstract

The consumption of lighting energy in buildings continues to rise, and many studies are being conducted to address this problem. As part of such initiatives, research is being performed on light shelves, which are natural lighting systems. However, most prior studies focused on variables for operating flat reflectors and light shelves. This study aims to evaluate the performance of curved light shelves to prove their effectiveness and derive optimal specifications for them. The following conclusions were reached. The optimal light shelf angles for a flat light shelf were found to be 30°, 20°, and 20° for the summer, mid-season, and winter, respectively, and accordingly, a movable light shelf system would be suitable for all three seasons. The optimal light shelf angles for a movable curved light shelf with an arc angle of 60° were found to be 30°, 30°, and 10° for the summer, mid-season, and winter, respectively. The optimal light shelf angle and arc angle for a fixed-type curved light shelf were found to be 20° and 60°, respectively. A fixed-type curved light shelf designed according to these optimal specifications can reduce energy consumption by 3.6% in comparison to a movable flat light shelf. Consequently, the curved light shelf is considered an effective system, and additional studies analyzing various other factors should be carried out in the future.

Performance Evaluation of External Light Shelves by Applying a Prism Sheet

“…This demonstrates the improvement of daylighting performance and the effectiveness of applying a prism sheet. Previous studies of light shelves [11][12][13][14][15][16][18][19][20] mentioned the need for movable light shelves to improve daylighting performance and save lighting energy; however, this study produced valid results in improving daylighting performance without operating or moving the light shelf.…”

“…However, controlling movable light shelves requires additional energy, so optimal designs need to be applied to deal with related issues. Light shelves are classified into external and internal light shelves depending on the installation location [14]; external light shelves have better daylighting performance than internal light shelves [18], however, there are issues related to damage and maintenance since they are installed on the outside [17].…”

“…Various studies have confirmed the effectiveness of light shelves [11][12][13]. However, conventional light shelves use flat reflectors to introduce external natural light into rooms [14], so the daylighting performance of the light shelf may be reduced depending on external environmental factors, such as the altitude of the sun. Recently, research [15,16] and technologies incorporating operating techniques have been introduced to solve this problem; however, moving light shelves may be unsuitable for saving building energy due to difficulties in maintenance and the need to consume additional energy in their operation [17].…”

“…However, controlling movable light shelves requires additional energy, so optimal designs need to be applied to deal with related issues. Light shelves are classified into external and internal light shelves depending on the installation location [14]; external light shelves have better daylighting performance than internal light shelves [18], however, there are issues related to damage and maintenance since they are installed on the outside [17]. As shown in Table 1, recent studies related to light shelves [11][12][13][14][15][16][18][19][20][21] have applied advanced technologies such as user recognition and location recognition or have incorporated daylighting and shading systems to improve the daylighting performance.…”

“…As shown in Table 1, recent studies related to light shelves [11][12][13][14][15][16][18][19][20][21] have applied advanced technologies such as user recognition and location recognition or have incorporated daylighting and shading systems to improve the daylighting performance. Although the light shelves proposed in Energies 2020, 13, 4618 3 of 13 these studies may contribute to saving lighting energy by maximizing the daylighting performance, they require complex structures or increase the range of motion and therefore have lower economic efficiency than simple conventional light shelves.…”