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A light-shelf is a highly efficient daylighting system about which a great deal of research has been performed. However, improvements to the daylighting performance of light-shelves have been limited, because light-shelves could introduce external natural light into the interior space through specular reflection, rather than into a specific region of the interior environment. In this study, to improve the performance of a light-shelf, a light-shelf using the principle of diffused reflection was proposed, and its validity was verified through performance verification. The conclusions of this study are as follows: (1) The optimal angles of a flat type light-shelf and a light-shelf using diffused reflection could vary depending on measurements taken in different seasons. (2) With the installation of the light-shelf using diffused reflection in the summer, the uniformity ratio of illuminance could be improved by 29.9%-34.3% with the external type and by 10.4%-13.7% with the internal type compared to the existing flat type light-shelf. (3) For the light-shelf using diffused reflection, the lighting energy could be reduced by 7.98%-13.3% in the case of the external type and by 1.8%-4.4% in the case of the internal type compared to the existing flat type light-shelf.

Various ongoing studies regard light-shelves as one solution to the recent increase in lighting energy consumption. However, in previous light-shelf systems, the direction of incoming light was determined by external conditions, thereby limiting the efficiency of lighting energy saving. The purpose of the present study was to develop a movable light-shelf system with location-awareness technology and verify its performance. In this study, a full-scale testbed was established in order to test the proposed movable light-shelf system with location awareness as well as to verify its energy saving potential. The results were analysed and compared with the performances of previous fixed (Case 1) and movable (Case 2) light-shelf systems without location-awareness technology. The obtained results were as follows. (1) The proposed light-shelf system can respond to external conditions and to the location of the occupant by means of the control axis of the light-shelf module angle through modulation between the control axis of the angle of the previous light-shelf and the reflector of the light-shelf. (2) The proposed light-shelf system provides 90.0% and 86.6%/91.0% energy savings in comparison to Case 1 and Case 2, respectively.

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.

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.