External Light Shelf Research Articles

The Effect of Light Shelf and Translucent Ceiling on Daylighting Performance in Office Building in Thailand

Daylight control strategies were a challenge for a high-rise building in terms of savingenergy consumption. Light shelf was one of the daylight control systems which was usuallyhorizontal or inclined surfaces, placed on the inner and/or the outer side of windows toreflect sunlight to ceiling and distribute the light deeper into the room. This study aimedto investigate the performance of daylight control strategies in office rooms using alight-self with translucent ceiling. The light shelf, which is typically horizontal or inclined,was placed on the inner or outer side of windows to reflect sunlight and distribute itdeeper into the room. The study investigated the effect of type of daylight techniqueswhich are a combination of different light shelves and translucent ceiling on daylightingperformance. The illuminance level in an office room was calculated using DIALux 4.13 andwas performed for working hours in Bangkok, Thailand. The simulation was performedunder clear sky conditions and using real climatic data from four orientations. Fivetypes of daylight techniques, including the existing room, were investigated in terms ofilluminance level and uniformity of daylight in the office room. The CIBSE (2015) and IESNA(2011) standards indicate that offices room should have uniformity of at least 0.8 andan illuminance level of 500 lux. Thus, the objective of this research was to determine thebest combination of light shelves and translucent ceilings for achieving illuminance anduniformity standards. The results showed that the external light shelf with a translucentceiling and static louver at 90o (option 4) was the best solution for office rooms, providingaverage illuminance level 776 lux (above the standard) and uniformity 0.4 (nearly thestandard). This conclusion suggests that a light-shelf with a translucent ceiling guidesdaylight deep into the room but less uniformity.

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.

Investigating the optimization potential of daylight, energy and occupant satisfaction performance in classrooms using innovative photovoltaic integrated light shelf systems

Building-integrated photovoltaics (BIPV) show potential as a means of efficient solar energy harvesting. This paper introduces a multi-objective framework for finding the optimized design of parametrically modeled photovoltaics integrated light shelf systems to maximize their benefits to the indoor environment and users. Since the geometric design of traditional shading devices is restricted to rectangular-shaped panels, we aim to attain a clearer perception of the potential advantages of employing panels with novel design alternatives. First, we developed parametric models of internal and external light shelves; each consisted of either a surface with a curved section or a 4-point planar surface. Next, the assessment of daylight and energy operation along with occupants' thermal and visual comfort was carried out using the environmental plugins of Honeybee and Ladybug. Furthermore, to decrease the required lighting energy and upgrade users' visual satisfaction by providing favorable illuminance levels required for a specific task, we divided the classroom into alterable lighting zones. Lastly, the optimization process was performed via the Octopus plugin for Grasshopper, and optimal solutions were identified. Based on the numerical results of the yearly simulations, we gained noticeable energy-saving up to 29% while improving occupants' thermal and visual comfort.

Analysis and evaluation of the effect of reflectance values on internal walls, internal roofs, and light shelf on optimal illumination levels in the diploma economics and business building of the vocational school UGM, Yogyakarta

The use of natural light as a source of lighting in buildings is an option in energy saving. One of the efforts that has been made is the installation of a light shelf. The light shelf installed in the UGM Vocational School Economics and Business Diploma (DEB SV) building is not fully working optimally. As many as 83% of the light shelf in lecture rooms is covered by curtains because it is considered to produce excess light (glare). This results in a greater consumption of lighting electricity. This study was conducted to analyze and evaluate the effect of the reflectance value (color) attached to the internal walls, internal roof, external light shelf, and internal light shelf on the indicator of illumination levels Useful Daylight Illuminance (UDI). Furthermore, this study aims to determine the optimum reflectance value (color) parameter. The research was conducted with a simulation method using RadianceIES in the IESVE 2021 software. The first simulation results show the value of reflectance (color) installed (base case) on the internal wall, internal roof, external light shelf, and internal light shelf in one of the lecture rooms of the DEB SV UGM building resulting in a very large value of the UDI>2000lux indicator, which is 84,9% (not according to the criteria). The results of the second simulation provide two variations of the optimum reflectance (color) parameters in the independent variable. The first variation is the internal walls, internal roof, external light shelf, and internal light shelf, each of which has a reflectance value (color) of 90,67% (beige), 100% (white), 90,67% (beige), and 100% (white). The second variation is the internal walls, internal roof, exte rnal light shelf, and internal light shelf, each of which has a reflectance value (color) of 90,67% (beige), 100% (white), 90,67% (beige), and 90,67% (beige).

Daylighting Performance of Light Shelf Photovoltaics (LSPV) for Office Buildings in Hot Desert-Like Regions

Visual comfort and energy consumption for lighting in large office buildings is an area of ongoing research, specifically focusing on the development of a daylight control technique (light shelf) combined with solar energy. This study aims to investigate the optimum performance of light shelf photovoltaics (LSPV) to improve daylight distribution and maximize energy savings for the hot desert-like climate of Saudi Arabia. A radiance simulation analysis was conducted in four phases to evaluate: appropriate height, reflector, internal curved light shelf (LS) angle, and the integrated photovoltaic (PV) with various coverages (25%, 50%, 75%, and entirely external LS). The results revealed that the optimum is achieved at a height of 1.3 m, the addition of a 30 cm reflector on the top of a window with an internal LS curved angle of 10° with 100% coverage (LSPV1, LSPV2). Such an arrangement reduces the energy consumption by more than 85%, eliminates uncomfortable glare, and provides uniform daylight except for during the winter season. Hence, the optimization of the LSPV system is considered to be an effective solution for sustainable buildings.

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.

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.

Effectiveness of a perforated light shelf for energy saving

Light shelves are natural lighting systems, which have been highlighted in various studies as a suitable approach for reducing energy consumption. However, external light shelves are at risk of being destroyed by high wind pressure when used on the upper stories of high-rise buildings. Therefore, this study proposes a perforated light shelf that minimizes the effect of wind pressure. Its effectiveness is verified by comparing its lighting energy saving performance with that of previously tested light shelves in an actual testbed. The results showed that at vent ratios of 29.55%, 32.58%, 34.27%, and 35.35%, the lighting energy consumption of the proposed perforated light shelf (Case 4) increased by 20.6%, 20.6%, 42.9%, and 48.3%, respectively, in comparison with that of a nonperforated light shelf. However, at the same four vent ratios, the perforated light shelf was found to be capable of reducing the lighting energy consumption by 74.0%, 74.0%, 56.0%, and 51.4%, respectively, in comparison with a case without a light shelf (Case 1) and a case with a 0° fixed nonperforated light shelf (Case 2). In Case 4, the lighting energy saving rate of the perforated light shelf may be improved by increasing its width.

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.

주거공간의 혼합형 광선반 각도 변화에 따른 채광성능 평가

The purpose of this study is to evaluate the effectiveness in the lighting performance of mixed type light-shelf, by comparing and analyzing the internal light-shelf, external light-shelf, and mixed-type light-shelf. The performance of light-shelf was evaluated according to the angle of light-shelf at summer solstice, winter solstice, vernal equinox, and autumn equinox. The comparative analysis between the internal light-shelf, external light-shelf, and mixed-type light-shelf was carried out using the performance evaluation and analysis method. The result of performance evaluation is shown as follows. The mixed type light-shelf showed the highest lighting performance all at summer solstice, winter solstice, vernal equinox, and autumn equinox, followed by the external light-shelf and the internal light-shelf in the same order. The mixed type light-shelf was the most favorable for bringing daylight to indoors by adjusting the angle of light-shelf, and it also showed the highest lighting performance in terms of uniformity ratio of illumination which indicates the quality of light.

A study on performance evaluation of punching plate reflecting plate-applied external light shelf according to vent ratio

Global energy consumption shows uptrend each year in the rapidly changing contemporary era. Building energy consumption accounts for 38% of total energy consumption, and lighting takes up high ratio with 22% in the building energy consumption. Lighting is actually applied to various researches and spaces. The light shelves make illuminance balanced by introducing natural light to indoor spaces. Among the light shelf types, external fluorescent light shelves are known to be more excellent in lighting performance, compared to the internal fluorescent light shelves and mixed fluorescent light shelves. However, the light shelves externally protruding by high wind pressure have difficulties in applying them to high rise buildings. This research proposes a punching plate reflecting plate-applied external fluorescent light shelf that can be designed for and applied to high rise buildings. This research verified the lighting performance of the existing light shelves and the circle-shaped punching plate reflecting plate-applied

The approach to daylighting by scale models and sun and sky simulators: A case study for different shading systems

At the Daylighting Laboratory of the Politecnico di Torino a facility, which consists of a sun simulator and a sky scanning simulator, allows daylighting simulations to be made inside scale models for both research and design purposes. Photometric data and digital images of the luminous environment are the results that are obtained. The “sky” covers one-sixth of the vault, while the “sun” is fixed: therefore the model is rotated to reproduce the entire vault and rotated and tilted to reproduce the relative sun–Earth position. In the paper the different components of the structure are shortly described, the possible fields of application are presented and, as an example of daylighting assessments, the results of a case study are reported. This latter is concerned with a comparative evaluation of different typologies of shading systems for South orientated façades for a sample high-school classroom: overhangs, external and internal+external light-shelves, horizontal fins are analysed, taking the effect of specular, semispecular and matt finishing also into account. For this purpose, reference conditions were assumed, both for sky conditions and sun positions, and repeated so as to compare environment performance which were obtained with the different shading systems.

Optimising daylighting in high-rise commercial developments in SE Asia and the use of computer programmes as a design tool

The consensus of the '92 Rio summit was that all development should aim for non-depletion of the earth's resources.The major growth region for the next decade is SE Asia and particularly the cities of South China for which Hong Kong is a role model with its dense urban construction. Recent Hong Kong energy legislation addressed the thermal transmission of the envelope without integrating building services energy consumption while planning legislation determines plot ratio but does not restrict overall building height in most areas of Hong Kong. A recently constructed high-rise commercial building has been analysed and proposed modifications computer modelled to evaluate options to extend daylight deeper into the space using extra interior height, alternative glazing and an external lightshelf. The commercial programme Lightscape, recently developed, is being assessed as a design tool to visually simulate the interior lighting, the illumination levels and daylight factors verified against scale physical models.