Performance Of Light Shelf Research Articles

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

In areas with a deep floor plan, the distribution of natural light is not uniform. Consequently, relying solely on daylight may not suffice to meet the space’s lighting requirements, necessitating the use of artificial lighting in darker areas. Therefore, a lighting system is needed that not only controls the glare near the windows but also increases the light at the end of the room and provides uniform daylight. One of the widely used systems is the “light shelf”, which has three main functions: shading, increasing the depth of light penetration, and reducing glare. Review articles about light shelves were published in 2015 and 2017, while more than 80% of the studies have been carried out since 2016, and light shelves with more diverse forms and dynamic elements and many consolidations have been proposed. Therefore, there is a need for a more comprehensive review. The main question of this research is how different parameters (including climate, material, ceiling, and integrated systems) can help to increase the efficiency of light shelves. By using a systematic review, studies in the past three decades were classified in order to determine the effect of these parameters on improving lighting performance and controlling solar heat gain.

Evaluation of External Light Shelf Performance in Relation to the Ceiling Types Used in Indoor Spaces

A light shelf is a type of natural daylight system that brings natural light from the outside into an indoor space through a reflector and a ceiling surface. The introduction of light shelves has led to studies evaluating their efficiency. However, past studies on light shelves did not consider the diversity of ceiling types when evaluating their performance. Therefore, this study derives fundamental data involving external light shelf designs by evaluating light shelf performance based on the ceiling type present using a light environment simulation method. This study analyzed the indoor illuminance distribution with Radiance to evaluate the performance according to light shelves and indoor space types. The results derived from this study are as follows: (1) In the case of a flat ceiling, the performance of an external light shelf can be improved by increasing its angle and width. However, adjusting the external light shelf angle to 30° during the middle of the season and 20° in winter is ineffective because natural light is not reflected by the ceiling surface. (2) The performance of a light shelf can be improved by increasing the slope and curvature of the ceiling types specified in this study. However, setting the light shelf angle to 30° during the middle season and to 30° and 20° in winter, when external natural light entering the indoor space is not reflected by the ceiling surface, is ineffective due to the low levels of daylight performance, regardless of the type of space. (3) To increase uniformity levels in gable ceilings and curved ceilings, it is advantageous to increase the number of reflections and diffusion areas on the ceiling’s surface due to the uniqueness of these ceiling shapes. Furthermore, the optimal external light shelf angle for these ceiling types differs from that of other types. (4) Regarding the appropriate external light shelf size according to a particular ceiling type, installing an angle-controllable external light shelf with a width of 1.2 m can improve daylight performance.

Experimental evaluation of radiant heat transmitted by light shelves

Light shelves are designed to distribute daylight deeper into the room and reduce energy consumption. While many studies have investigated the daylighting performance of light shelves, there are not much work done on the heat reflected by them. This paper aims to experimentally evaluate the radiant heat reflected from light shelves and analyse the trade-off between the transmission of heat and light. The study involves an experimental setup with controlled conditions and a novel methodology to quantify the reflected radiation. About 5 million data points for heat flux data were collected from light shelves made of eight different materials. Results showed that the mirror glass surface with high specular reflectivity, has maximum direct heat transmission of 10.4 W/m2 along with maximum illuminance. However, aluminium with lesser illuminance than mirror glass exhibits a maximum overall heat transmission of 35.8 W/m2. Also, polished black granite slab showed negligible reflected heat and moderate illuminance. Thus, this study helps us select materials for light shelves to reduce heat transmission without significantly affecting reflected light.

A Daylight Assessment on Visual and Nonvisual Effects of Light Shelves: A Human-centered Simulation-based Approach

The contribution of daylight to a comfortable environment for occupants has been the subject of studies for years. Light shelves are known as daylight redirecting systems to enhance indoor daylight conditions. Although several research papers have focused on their daylight performance, there is a lack of studies on the performance of light shelves on circadian rhythm. In this context, daylight's biological effects on human beings have been under investigation. Therefore, this paper aims to evaluate the performance of light shelves in terms of visual and nonvisual effects of daylight, including circadian stimulus, visual comfort, and task performance through a multi-criteria human-centric evaluation. To this end, the authors set three following conditions if a model could provide simultaneously, the occupants would be in a comfortable space both visually and non-visually: 75% workstations with Equivalent Melanopic Lux> 250 EML concurrently with Vertical Photopic illuminance < 1500 lux, and Photopic illuminance on working plane > 300 lux. Accordingly, the light shelves with various depths, states, and orientations were simulated by ALFA to evaluate the comfort of occupants in office space over working hours. The results indicated that although applying light shelves impacted the metrics, the enhancements were minor compared to a conventional window, specifically on EML. In detail, inadequate EML levels were observed in all orientations on the simulation days. Besides, changes in the photopic illuminance at the eye and workstations levels were not substantial. Finally, the paper presents a case study that showcases simulation techniques that focus on daylighting and circadian rhythm.

Multi-objective optimization of daylight performance and thermal comfort in classrooms with light-shelves: Case studies in Tehran and Sari, Iran

In educational buildings, an efficient daylight design has significant influences on student’s visual comfort, well-being and productivity while it offers significant benefits for reducing lighting energy consumption. Besides visual discomfort, the excess of daylight entry to space will cause disadvantages, including building overheat. Therefore, it is essential to define the optimal design for daylight control devices. In previous studies, daylight performance of light-shelf as a window-attached daylight control device has been studied. This paper aims to investigate the effect of sky cloudiness on the optimum light-shelf properties defined for typical classrooms. In addition, the optimum properties of the light-shelf for classrooms in two cities have been defined, which had not been addressed in Iran’s national codes and guidelines. The methodology used is based on three steps: daylight optimization of light-shelf parameters, thermal comfort analysis for selected solutions, and choosing the best option. Four parameters of light-shelf, including height, length of the exterior part, length, and angle of inner part, have been considered as variables. Using Octopus optimization algorithm in Rhinoceros, Grasshopper simulation tool, a multi-objective algorithm has been applied to find the optimum combination of the parameters based on daylight performance indicators. Thermal comfort analysis has been conducted for selected solutions with optimized light shelves using Openstudio. The results indicated that applying light-shelf in Tehran with less sky cloudiness is more effective than Sari in terms of providing both daylight and thermal comfort, especially for cases with more window to wall ratio (WWR). Sari, the case with lower WWR, does not necessarily have less Annual Solar Exposure, even with an optimized light-shelf. Hence choosing the best option without comparing daylight metrics for optimized solutions of various WWR is misleading. According to the results, although the best options are different in the cities as the effect of sky cloud cover, the optimum light-shelf properties are the same in light-shelf height, exterior, and interior length, while the pivot angles vary. There is also a relation between rotation angle and daylight availability regarding WWR in each city. Considering daylight and comfort issues, WWR for the best option in Tehran is greater than Sari. The study results provide useful information for designers for choosing the optimal properties of light shelves and the best option for design in the two mentioned cities.

A Comparative Study on Daylight Performance Assessment of Light Shelves Based on Inclination

Energy consumption of lighting can be reduced by using different daylight control strategies. The rise in environmental distresses requires the necessity of natural light control systems. Light shelf is considered as excellent lighting control scheme that provides great lighting production and inexpensive prospect via entering the daylight inside the space. The aims of this study shows that the daylight efficiency and visual productivity are affected by the design parameters of light shelf such as its angle, location and height. In this research, Autodesk Ecotect 2011 is used for the daylight simulation of summer solstice and winter solstice days under overcast sky conditions on a nominated theoretical study space of an institutional building. Daylight simulation is carried out to evaluate the illuminance requirement within the selected space and analysis is also executed on the model with selected categories of light shelves including different positions, heights and angles. The acquired data is then exported on Radiance software intended for complete day-light investigation. The results of this research shows that external light shelf at a height of 7' and an angle of 20˚ is the most appropriate choice in prevailing the glare and it also enhanced the illuminance level to11.5% in 21st June and 10.6% in 21st December as compared to without light shelves. Furthermore, the shaded range is decreased by the rise in the angle of Light shelf which has a tendency to increase the inside average lighting. Hence, significant consideration should be given to the height and position of light shelves, since it has a superior effect on light shelf performance.

Performance Evaluation of External Light Shelves by Applying a Prism Sheet

To address the increased use of lighting energy in the building sector, research on the use of light shelves has been increasing. Previous studies have focused on applying operating techniques to improve daylighting performance, which reduces the economic efficiency of light shelves and the building energy savings. This study proposes the use of prism sheets to improve the performance of light shelves, a concept which was validated by evaluating the performance related to saving building energy and improving indoor light uniformity through a full-scale testbed. This study used an external light shelf with no prism sheet, a window with a prism sheet applied, and a window with both an external light shelf and prism sheet applied as Case 1, Case 2, and Case 3, respectively, and analyzed the illuminance distribution and lighting energy consumption required to maintain the optimal indoor illumination for each case. This study also derived the optimal specifications for each case to save building energy and considered the flow of natural light to analyze the performance evaluation results. The main findings are as follows: (1) the optimal specifications to improve daylighting performance were derived for Case 1, requiring the application of operating techniques; (2) Case 2 was not suitable for saving energy and improving light uniformity when compared to Case 1; and (3) Case 3 was effective in saving building energy. In Case 3, even when the light shelf was fixed at 20° without moving, it saved building energy and improved light uniformity compared to Case 1. However, the prism sheet in Case 3 should be detached during winter to maximize building energy savings.

Experimental Analysis of the Performance of Light Shelves in Different Geometrical Configurations Through the Scale Model Approach

Experimental Analysis of the Performance of Light Shelves in Different Geometrical Configurations Through the Scale Model Approach

Positioning of light shelves to enhance daylight illuminance in office rooms

This paper aims to improve daylighting by using light shelves. Horizontal light shelf is found to increase the illuminance in the interior of office rooms. By tilting external light shelf more illuminance can be achieved. For uniformity of illuminance tiltable light shelf is the best choice instead of horizontal light shelf. The performance of light shelves was examined through simulations on DIALux and compared with experimental values obtained from a prototype. Substantial improvement in illuminance is obtained in the experimental studies with tilted light shelves on the prototype.

EVALUATION OF LIGHT SHELF DESIGN PERFORMANCES TO THE DAYLIGHT’S SUNLIGHT PENETRATION ON SINAR MAS LAND PLAZA BUILDING TANGERANG TO INCREASE THE GREEN MARK ASSESSMENT

Abstract- Light shelf is one of the daylighting strategies used in Sinar Mas Land Plaza Tangerang. However, based on observations made on the object of research, light shelf design on Sinar Mas Land Plaza Tangerang is not optimal. This is because the purpose of a light shelf that should reflect sunlight directly to enter much deeper into the room does not occur. This is evident in the use of artificial lighting in areas close to openings, so it is necessary to evaluate the light shelf design to improve light shelf performance, which is also useful for improving the Green Mark BCA assessment.This research uses experimental research method to see daylight penetration by simulating model using Ecotect which can simulate model by ray simulation. Evaluation is done by manipulating variables from light shelf design such as ceiling design aspect, light shelf shape, and light shelf slope to see effective light shelf design to be applied to Sinar Mas Land Plaza Tangerang. Based on the research, it can be concluded that the performance of the existing light shelf design is not optimal because of the fins that are above the light shelf to block out direct sunlight. The sloped ceiling design also affects the daylight penetration distance into space. Light shelf design that effective at North orientation is a light shelf design with curved shapes, while the light shelf design that effective at South orientation is a light shelf design with a slope of 200. Improving the light shelf design can increase the Green Mark rating up to 8 points. Key Words: light shelf, daylight penetration, assessment of Green Mark, Ecotect

EVALUATION OF LIGHT SHELF DESIGN PERFORMANCES TO THE DAYLIGHT’S SUNLIGHT PENETRATION ON SINAR MAS LAND PLAZA BUILDING TANGERANG TO INCREASE THE GREEN MARK ASSESSMENT

Abstract- Light shelf is one of the daylighting strategies used in Sinar Mas Land Plaza Tangerang. However,based on observations made on the object of research, light shelf design on Sinar Mas Land Plaza Tangerang isnot optimal. This is because the purpose of a light shelf that should reflect sunlight directly to enter much deeperinto the room does not occur. This is evident in the use of artificial lighting in areas close to openings, so it isnecessary to evaluate the light shelf design to improve light shelf performance, which is also useful for improvingthe Green Mark BCA assessment.This research uses experimental research method to see daylight penetration by simulating model usingEcotect which can simulate model by ray simulation. Evaluation is done by manipulating variables from lightshelf design such as ceiling design aspect, light shelf shape, and light shelf slope to see effective light shelf designto be applied to Sinar Mas Land Plaza Tangerang. Based on the research, it can be concluded that theperformance of the existing light shelf design is not optimal because of the fins that are above the light shelf toblock out direct sunlight. The sloped ceiling design also affects the daylight penetration distance into space. Lightshelf design that effective at North orientation is a light shelf design with curved shapes, while the light shelfdesign that effective at South orientation is a light shelf design with a slope of 200. Improving the light shelfdesigncan increase the Green Mark rating up to 8 points.Key Words: light shelf, daylight penetration, assessment of Green Mark, Ecotect

Energy-saving performance of light shelves under the application of user-awareness technology and light-dimming control

Much attention has been given to the sun as a source of alternative energy for conserving energy. Recently, solar energy technologies have been linked with IT to reduce the energy consumed in buildings, with proven effectiveness. In this study, we investigate the effectiveness of a light shelf with user-awareness and dimming control features. We assess the efficiency of a light shelf in saving lighting energy by examining each component of the light shelf. A testbed is used to verify the lighting energy-saving effect of this light shelf. In order to determine the energy consumption in different situations, we examine three cases. Case 1 features a light shelf that is user-unaware but with lighting On/Off control. Case 2 features a light shelf that is user-aware with lighting On/Off control. Case 3 features a light shelf that is user-aware with dimming control. Users were classified by target illumination levels according to illumination standards: A (600 lx), B (400 lx), and C (300 lx). The appropriate standards and lighting energy consumption levels for each Case were found through this study, and the lighting energy saving performance of the light shelf that is user-aware and applies light dimming technology proposed here was verified.

광선반 채광성능 개선을 위한 프리즘시트 적용 방안 연구

Recently, there has been an increase in the number of studies on the performance of light shelf with an aim of solving the issue of increasing lighting energy consumption in the building sector. However, the efficiency of the light shelf is limited in terms of building energy saving as operating technologies are applied to improve the daylighting performance in response to the external environment. Therefore, this study proposes a light shelf using a prism sheet and aims to verify its effectiveness based on performance evaluation through a full-scale test bed. The conclusions of the study are as follows : 1) This study derived the optimal variables for light shelf installation (Case 1), prism sheet attachment (Case 2), and light shelf with prism sheet (Case 3). 2) Based on the optimal variables, saving lighting energy was achieved in Case 3 compared to Case 1 and Case 2 by 2.6% and 14.9%, respectively. In addition, the fixed type of Case 3 at the angle of 0° led to saving of lighting energy compared to Case 2 and Case 3 by 2.6% and 14.9%, respectively. The results reveal that Case 3 proposed in this study is effective in terms of using the prism sheet to obtain the daylighting efficiency of a movable light shelf. 3) Based on the optimal angles derived for each case, the uniformity of Case 3 can be improved by 11.4% and 12.1% in the summer, and 0% and 6.3% in the mid-season, compared to Case 1 and Case 2, respectively. However, the application of the prism sheet during winter reduces the uniformity, so it is preferable to remove the prism sheet during winter.

Improvement of light-shelf performance through the use of a diffusion sheet

Several studies have addressed the issue of increases in the energy consumption associated with lighting in buildings. The light-shelf is a natural lighting system that efficiently reduces the amount of energy consumed for lighting by drawing natural light into a room through reflection. However, the performance of the light-shelf is reduced as a result of external environmental factors, such as the solar azimuth, and it can also produce glare while drawing natural light into the room. The present study examined the use of a light-shelf with a diffusion sheet, with the goal of improving LED lighting efficiency and reducing glare, and set out to validate its efficacy by evaluating its performance according to the position at which the diffusion sheet was attached. As part of the present study, performance evaluation cases were configured according to the diffusion sheet application and attachment position, and evaluations were conducted using a full-size test-bed. It was found that a conventional light-shelf brought more light into a room than that with the diffusion sheet, but glare was generated at certain angles in each season. However, the proposed light-shelf with the diffusion sheet attached to the upper window glass was analyzed and found to be effective at reducing lighting energy consumption by 2% while improving the glare and uniformity compared to that of a conventional light-shelf. This study is meaningful since it establishes the basic data for future light shelf design by deriving relevant variables and considering lighting energy reduction and glare.

A Vision of Daylight Technologies for High-Rise Residential Building in Tropic

Sidelighting is still the primary lighting opening for most buildings in all part of the world. The technology allows only limited penetration of daylight that causes a high energy consumption for artificial lighting. Using a right daylight technology in high-rise residential building could saving more energy and have a good impact on productivity and occupant’s health. This paper discusses the daylighting technologies for high-rise residential buildings in tropical area with literature review method. Some factors such function of systems, location, ability to change and transparency/the view outside will be the factors that must consider in selecting daylight technologies for high-rise residential building in tropic. The diffuse light-guiding system is a practical daylight technologies for deep floor plan building in tropics. The studies shows that potential daylight technology is diffuse light-guiding system that composed from light shelf, fish sytem and anidolic system. The performance of light shelf influenced by direct sunlight. Its increasing iluminance near window area and causes uneven distribution of illumination in the room. Fish system shows better performance than ordinary blinds, however the result is from integration of fish system and external blinds at low internal illuminance. Application anidolic system in tropical area improving illuminance ratio by factor 3.3, reducing glare by 14%, under overcast sky could transfer daylight upto12.5 m and under intermediate sky up to 20 m. For future work, anidolic system expected to respond sky conditions and direct sunlight for improvement in tropical area.

확산필름 부착 위치에 따른 광선반 성능개선 연구

Purpose: Various studies on a light shelf are in progress, but it has the problem of glare occurrence. The present study suggested a diffusion film as the method for resolving the glare problem, and aimed to establish light shelf-related basic data by conducting the performance evaluation of a light shelf depending on the installation position of the diffusion film. Method: To carry out the light shelf performance evaluation depending on the diffusion film installation position, three cases were established: no diffusion film installation (Case 1), diffusion film installation on the reflector (Case 2), and diffusion film installation on the upper glass surface of the window for light shelf installation (Case 3); and the energy reduction performance, luminance, and luminance contrast were analyzed based on a testbed. Result: The conclusions of this study are as follows. 1) When the diffusion film was applied, the amount of light introduced through the light shelf decreased, and the average indoor illumination decreased accordingly. 2) For Case 3, the lighting energy reduction performance was identical to the lighting energy reduction efficiency of the existing light shelf; and for Case 2, it was found to be inappropriate as the lighting energy consumption increased compared to that of the existing light shelf. 3) The analysis of the glare for the cases established in this study showed that the luminance contrast was low for Case 3, and thus the glare problem could be minimized. 4) The specific angle of the light shelf could induce the glare problem by increasing the luminance depending on the external condition. 5) Based on the aforementioned contents, the installation position of the diffusion film for improving the lighting performance and glare problem of the light shelf was found to be the upper glass surface of the window for light shelf installation.

개폐 개념의 높이 조절이 가능한 광선반 개발 연구 : 외부조도에 따른 광선반 성능평가 중심으로

개폐 개념의 높이 조절이 가능한 광선반 개발 연구 : 외부조도에 따른 광선반 성능평가 중심으로

Performance evaluation of light shelves

This paper aims to objectively evaluate the potential of light shelves to improve daylighting and visual comfort. This study consists of two parts. The first part is experimental and involves measurements taken on a scaled prototype. More than one million data points were collected using illuminance sensors installed on a test chamber. The data was analyzed statistically and the performance of the light shelf was evaluated for various configurations. A horizontal light shelf is found to increase the illuminance in the interior by an average of 21%. By rotating the external light shelf to an optimal angle, up to 300% increase in illuminance can be achieved. The second part of the study consists of purely theoretical simulations. Some new metrics such as useful daylight enhancement (UDLE) were developed specifically to evaluate the daylighting performances of light shelves. A case study of a hypothetical building in Chennai is taken and simulations are performed using Radiance lighting simulation software. 1080 simulations were performed under various configurations. It is found that most of the common assumptions about the performance of light shelves are not supported by simulation results. Even though, in many cases, the horizontal light shelf is able to improve illuminance at distances greater than the height of the window, the area where there is useful daylight enhancement is low. It is commonly assumed that light shelf provides shading near the window, thus eliminating glare. However, in 30% of the simulated cases, horizontal light shelves are found to increase the illuminance near the window, thereby increasing the possibility of glare. Light shelf is also found to decrease the uniformity in illuminance. These problems can be eliminated by using a rotatable light shelf.

Study on Indoor Temperature Variation Depending on External Type Light Shelf Angle

Among natural light systems, the light shelf, which reflects external natural light and introduces the light deep into the indoor space, has been studied and applied in various areas, as its efficiency is well recognized. However, previous studies related to the light shelf have been limited to simple variables such as light shelf angle, width, height, and reflection rate in a specific environment or lighting energy, and the change of the thermal environment due to the reflection by a light shelf and the heating and energy consumption caused by the change have not been investigated. Therefore, the present study was conducted as a fundamental study focusing on temperature change in an indoor space depending on the installation of a light shelf and the variables of a light shelf. The following results were obtained from the present study. 1) The average temperature when the angle of a light shelf was 0° and 10° was lower than when no light shelf was installed. This indicates that the introduction of light by light shelf reflection was decreased as a shade was formed by the light shelf. 2) The indoor temperature with a light shelf having a light shelf angle of 30° was higher than that without an installed light shelf, which may be because more light was introduced by the reflection on the light shelf. The optimum light shelf angle of 30° found in previous studies may be inappropriate since the energy consumption for cooling is increased, which should be taken into account in the design of a light shelf. Future studies may need to be conducted on the evaluation of light shelf performance with respect to the light and cooling and heating energy consumption depending on the variation of indoor space temperature.

빛환경 및 냉난방환경 기반 광선반 성능평가 연구

Purpose: As the energy consumed by buildings increases, there is a growing need for studies and technology development to address this issue. One of the solutions to excessive energy use by buildings is the light-shelf, which is a natural lighting system enabling efficient reduction in light energy, and research in this area has been intensive. However, most of the studies about the light-shelf are limited to the light environment, and thus the application of their findings to an actual environment in the form of a design may be problematic. Therefore, the purpose of the present study is to provide fundamental data for light-shelf design by carrying out a light-shelf performance evaluation on the basis of the light environment and the heating and cooling environment. Method: In the present study, a testbed was established to conduct a light-shelf performance evaluation by measuring the electric power consumption of lighting and heating and cooling devices depending on the existence of a light-shelf and its angle. Result: The findings of the present study are as follows: 1) With respect to the uniformity of the indoor light environment amenity, the optimum angle of a light-shelf was found to be <TEX>$30^{\circ}$</TEX> for the summer solstice and the winter solstice. 2) With respect to the reduction of electric power consumption by indoor lighting devices, the optimum light-shelf angle at the summer solstice is <TEX>$30^{\circ}$</TEX>, at which time electric power consumption may be reduced by 10.2% in comparison with when no light-shelf is applied. However, at the winter solstice, a light-shelf may increase the energy consumption for lighting in comparison with when no light-shelf is applied, and this should be taken into account in the design of a light-shelf. 3) In terms of reducing the electric power consumption of heating and cooling devices, the optimum angle of a light-shelf was found to be <TEX>$30^{\circ}$</TEX> for the summer solstice, while a light-shelf is inappropriate for the winter solstice since a light-shelf creates shade and thus increases the heating energy consumption. 4) To summarize the findings above, the optimum angle of a light-shelf is <TEX>$30^{\circ}$</TEX> for the summer solstice, but the installation of a light-shelf may in some circumstances increase the energy consumed by lighting devices as well as by heating and cooling devices. Therefore, more studies and technology development may need to be performed to solve the problem of increased energy consumption at the winter solstice.