Evaluation of a light shelf based on energy consumption for lighting and air conditioning

Abstract

The shading effects of light shelves in indoor thermal environments have not been investigated to date. Thus, this study aims to identify the effectiveness and appropriate parameters required for a light shelf by evaluating its performance in the presence of lighting and air conditioning. A full-scale testbed was established in this study for evaluating the performance of the light shelf. Moreover, the performance evaluation was conducted by calculating the energy consumed for lighting and air conditioning to maintain proper temperature and illuminance. This study found the following: (1) During summer, the use of a light shelf would reduce the energy consumption for lighting and air conditioning by 0%–10.5% and 6.9%–9.3%, respectively. (2) During winter, the use of a light shelf would increase the energy consumption for lighting and air conditioning by 0%–25.3% and 0.2%–3.2%, respectively, which is undesirable. (3) Increasing the angle of the light shelf would increase the amount of light penetrating to indoors, thus would reduce the energy required for lighting. Based on these findings, we recommend the installation of a detachable light shelf that is 0.6-m wide with a 30° angle for buildings in Korea; and during winter, the light shelf should be removed to save energy.

Performance Evaluation of External Light Shelves by Applying a Prism Sheet

“…As shown in Figure 6, the artificial solar irradiation apparatus enabled us to simulate the sun by controlling the intensity, height, and angle of the artificial light source. This Grade-A apparatus ensured measurement uniformity in accordance with ASTM E927-85 [25], so it was able to obtain valid results between performance evaluations. However, the mechanical characteristics of this apparatus meant that it could only be used to evaluate the performance when the sun was facing south since it was impossible to simulate the solar azimuth.…”

“…As shown in Figure 6, the artificial solar irradiation apparatus enabled us to simulate the sun by controlling the intensity, height, and angle of the artificial light source. This Grade-A apparatus ensured measurement uniformity in accordance with ASTM E927-85 [25], so it…”

“…For this study, a full-scale testbed was built based on a related study [25] as shown in Table 6, and the details are given as follows: The size of the testbed was 4.9 m × 6.6 m × 2.5 m, and the reflectance was set to 86%, 46%, and 25% for the ceiling, wall, and floor, respectively. The size of the window where the light shelf was installed was 1.9 m × 1.7 m, and the transmittance of the glass was 80%.…”

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)…”

A Review of Light Shelf Designs for Daylit Environments

“…The use of daylighting systems, in an effort to increase core daylight illuminance, may reduce lighting energy consumption, but careful design is needed in order to avoid possible increases in cooling loads especially in cooling-dominated locations [10]. Thus, the main task of the design teams is to balance antagonistic phenomena, in an effort to maximize the users' thermal and visual comfort.…”