Light Shelf System Research Articles

Analytical Study on Reducing the Heating Effects of Daylight and Improving Natural Lighting Performance at Erzincan Train Station in the Context of Climate Change

Climate change is an environmental issue that is rapidly escalating due to the effects of global warming. The increase in carbon emissions, along with various human activities such as industrial processes, land use changes, and the reckless consumption of natural resources, are among the primary causes of global warming. Various architectural interventions are being implemented in historical buildings to mitigate the impact of global warming and its consequence, climate change. The study aims to protect the historical building from the harmful effects of climate change by reducing the heating effects of direct sunlight during the summer and enhancing the efficiency of natural lighting throughout the day. In this context, the Erzincan Train Station is located in Erzincan in Eastern Anatolia. Erzincan is one of the most affected by the climate change crisis has been selected for the study. The plans of the Erzincan Train Station were digitized using AutoCAD software and subsequently modeled in three dimensions using Revit software. Daylight analysis was conducted on the created model using the Insight plugin in Revit software. The analysis determined that recommendations should be made for the building's south facade. Based on the climate data of Erzincan province and the conducted analyses, the light shelf system was designed and implemented due to its applicability, shading, and lighting advantages among daylighting systems. The effects of the proposed system were examined using spatial daylight autonomy (sDA) and annual sunlight exposure (ASE) daylight metrics according to LEED v4 EQc7 standards. The study found that the light shelf system resulted in a 5% reduction in ASE values building-wide and a 6% reduction in the average values of specific areas while increasing sDA values. In this context, it has been observed that areas experiencing a decrease in direct sunlight exposure (ASE values) also show an increase in sufficient daylight exposure (sDA values), which could contribute to improving the building's energy performance.

Subjective and Simulation-Based Analysis of Discomfort Glare Metrics in Office Buildings with Light Shelf Systems

Glare is a kind of physiological phenomenon that influences occupants’ visual comfort. Discomfort glare scenes in comparison to other levels of glare have been difficult to estimate and need accurate and reliable metrics. In contemporary architecture, the glass façade is so popular since it can remarkably minimize energy consumption in buildings and maximize daylight utilization as a natural energy. However, it is necessary to consider occupants’ visual discomfort due to the daylighting glare risks during the initial stage of design. Since the measured glare metrics should have an acceptable correlation with the human subject data study, the agreement on the glare indices is complicated. This paper presents a comparison between subjective and simulation-based analysis of discomfort glare metrics in offices with a light shelf system. The discomfort glare metrics considered in this study include Daylight Glare Index (DGI), CIE Glare Index (CGI), Visual Comfort Probability (VCP), Unified Glare Rating (UGR), and Daylight Glare Probability (DGP). The parallel comparison was conducted by using simulation and questionnaire surveys to determine which criteria are more useful under different conditions. According to the findings, DGP yields the most reliable results in different levels of glare based on the subjective analysis and VCP has the lowest accuracy in each stage. UGR also has the highest accuracy rate for evaluating perceptible glare, DGI is applicable for assessing imperceptible glare, and CGI can be an acceptable index for approximating intolerable glare. The study results significantly reduce the complexity of the problem and can provide useful guidance for designers to select the most reliable glare metric based on climatic conditions.

Cooling capacity evaluation of thermally activated light shelf (TALS) systems

A light shelf is typically used to improve the lighting environment by preventing glares and increasing illuminance in interior zones. If its surfaces can be utilized as cooling surfaces it can also be used to control the thermal environment, particularly in perimeter zones. In this study, the concept of a thermally activated light shelf (TALS), wherein a chilled water pipe is embedded in a light shelf, was proposed, and its cooling capacity was experimentally evaluated. As the upper and lower surfaces are exposed to indoor air and cooling loads, which are different from those of conventional radiant cooling panels, a mock-up test chamber was developed to represent the cooling load applied to both the upper and lower surfaces of the TALS. Mock-up experiments were conducted to evaluate the cooling capacity of the TALS alternatives: TALS with thermal insulation (INS case), cavity air (AIR case), and DC fans (FAN case). Compared with the baseline (INS case), the cooling capacities of the AIR and FAN cases were enhanced by 9.4–29.4% and 22.7–53.1%, respectively, because both the upper and lower surfaces could be utilized as cooling surfaces. Based on the experimental results, cooling capacity curves were derived to provide generalized cooling capacity data considering various cooling load conditions, operating conditions (e.g., chilled water temperature and room air temperature), and layer configurations of the TALS.

Impact of Layer Configuration and Chilled Water Temperature on the Cooling Capacity of Thermally Activated Light Shelf (TALS) System

Light shelves provide a function to control direct sunlight and introduce daylight into indoor spaces. Also, chilled water flowing in the light shelf can mitigate local cooling demands in perimeter zones. Therefore, in this study, a thermally activated light shelf (TALS) system was proposed, and the TALS’s radiative cooling capacity was evaluated. To do this, a mock-up chamber was developed using prototypes of TALS systems based on panel configurations. It is included: ‘Insulated’ (INS), ‘Air layer’ (ARL), and ‘Air layer with fans’ (ARF), which were designed to increase thermal insulation, natural convection, and forced convection in the TALS panels, respectively. The experiment showed that the ARL and ARF increased cooling capacity by 29% and 57% compared to the INS. Natural convective heat transfer and fan-forced airflow in the TALS's air cavity contributed to improving cooling capacity. With the INS and ARL, the air temperature was recorded at 28.6°C, which requires additional space cooling. The ARF reduced air temperature up to 2.0°C because the TALS cavity fans expedited convective heat transfer and mixing air between the cavity and test chamber. The results of this study could be used to estimate TALS cooling capacity and propose an optimal design in buildings.

Design Optimization for Light-Shelves with Regard to Daylighting Performance Improvements in The Tropics

Different daylight device systems and control strategies can be employed in different parts of a window system to perform different functions, particularly for fully glazed façades. A light-shelves with parametric control in both portions of the system were proposed in this study as an innovative daylighting device to improve daylighting distribution and glare probability. The aim of this article was to present a simulation study to investigate the influence of light shelves on daylighting performance improvements in buildings located in tropical climates. Multi-objective optimization method was proposed by classifying the results based on sky conditions. The metrics of Useful Daylight Illuminance and Daylight Glare Probability were used to evaluate the daylight performance and glare to compare the final solutions of the blight shelf parameters of the light shelf. The study concludes that daylight improvements by optimal solutions of light shelves can provide the best range of optimal daylighting for visual comfort in office spaces in the tropics. The idea of a light shelf system with parametric control in both portions (inner and outer) provides the most optimal options for achieving balanced daylighting levels in both the front and back of the room. This resulted in a glare-free environment with undetectable glare indices, and acceptable daylight is accomplished, as well as a high percentage coverage within UDI300-2000 lux between 63% and 73.8% at midday and no less than 55% during working hours.

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.

Simulation Study on Cooling Effect of Thermally Activated Light Shelf (TALS) System

A light shelf is commonly used to mitigate glare discomfort and overheating by preventing solar radiation from penetrating the indoor space. If the light shelf can be thermally activated, it can also be used for space cooling, particularly for the perimeter zone in buildings. In this study, a thermally activated light shelf (TALS) system was proposed, where the light shelf was integrated with a radiant cooling panel system. To examine the applicability of the TALS system, heat transfer simulations were conducted using the Physibel software. Based on the simulation results, the layer of TALS was determined to maximize cooling capacity at the lower panel surface while minimizing the lower surface temperature. Transient simulations were also conducted to evaluate the cooling effect of the TALS system during the summer season. Simulation results showed that the TALS system could reduce the average perimeter and interior zone temperature by 2.23°C and 2.19°C, respectively. With the TALS system, the maximum temperature was reduced by 3.2°C in both the perimeter and interior zones. It was found that the TALS system could effectively reduce the room air temperature, which could lead to cooling energy savings. The impact of the TALS system on cooling energy consumption needs to be investigated in future studies.

The impact of an external obstacle daylight in deep office spaces at hot arid zone

The use of effective daylighting systems is one of the main factors that inflounces energy consumption in buildings especially in deep office spaces. Therefore, the need for innovative daylighting systems with optimum overall daylighting performance - especially in term of saving energy performance - is an essential design element for such spaces. Light shelf systems are the most major potential lighting systems that can be used to provide such innovative daylighting systems.The parametric approach was implemented where all possible combinations of the various design parameters for the main two design elements of the light shelf system (light shelf and room specifications) were computed through Diva-for-Rhino (Grasshopper). The study of optimized light shelf systems in deep office spaces has been carried out in case of an external obstacle (neighbor) and without it – according to the Egyptian building codes - in order to identify the impact of such design elements on the performance of the optimized light shelf system in the main four directions in hot arid zone climate.

A Basic Study on the Performance Evaluation of a Movable Light Shelf with a Rolling Reflector That Can Change Reflectivity to Improve the Visual Environment.

In recent years, the need for comfortable visual environments in indoor spaces has increased energy use in buildings. There have been diverse studies on using a light shelf to solve this problem. It is an effective system that allows external natural light deep into indoor spaces through reflection. However, prior studies have used light shelves with a fixed reflectivity, and there are few studies on improving the visual environment through light shelf control. Therefore, this study proposes a movable light shelf with a rolling reflector that can change the reflectivity. To achieve these objectives, we conducted a performance evaluation of the system’s ability to save energy and improve the visual environment. This study built a real scale testbed and conducted a performance evaluation by deriving values for lighting energy consumption, uniformity, and luminance contrast depending on the light shelf variables. We conclude that (1) the light shelf system achieved an energy savings of 13.6% and 5.7%, respectively, compared to a fixed type light shelf, whose reflectivity cannot be changed, and a traditional movable light shelf; (2) in terms of improving the visual environment, results suggest that the visual environment could be improved using a light shelf by deriving light shelf variables that disturb indoor uniformity; and (3) the results verified glare generation conditions by deriving luminance contrast caused by the variables of light shelf angle and its reflectivity.

A Study on the Blind-Type Light Shelf System for Improvement of Indoor Uniformity Ratio of Illuminance

Purpose: Light shelf systems can reduce the energy required for lighting by facilitating natural light ingress deep into a building. However, while they reflect a large amount of light into the building, they tend to create a low uniformity ratio of illuminance, and their indoor illuminance is not adjustable. Also, they are seldom used in architectural design due to their aesthetic disadvantages. This study proposes a blind-type light shelf system, consisting of multiple light shelf slats and blind slats, in order to solve the lighting problem of the light shelf system by modifying it with a blind system to reduce the energy required for artificial lighting. Method: Three combinations of blind-type light shelf system (no light shelf, 50 mm slats, and 100 mm slats) were proposed, and their performance was evaluated based on illuminance and uniformity ratios achieved in the indoor environment. Results: Case 2(50 mm slat) slatshowed an improvement, compared to the unmodified window, of up to 3.2 times while Case 3(100 mm slat), showed an improvement in the uniformity ratio of up to 2.8 times. With the installation of a blind-type light shelf system, the uniformity ratio can be ~3.2 times higher in the winter solstice and summer solstice, resulting in more light penetrating deeper into the interior of the building. The blind light shelf system was more effective in Case 2 than in Case 3 because it was better to have more light slats, despite the narrow slat width.

A Basic Study on Development of Movable Light-Shelf System with a built-in PV

A Basic Study on Development of Movable Light-Shelf System with a built-in PV

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

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.

Proposal for Light Shelf System that Applies Biomimicry for Lighting Energy Conservation

Proposal for Light Shelf System that Applies Biomimicry for Lighting Energy Conservation

Sophisticated Light Shelf System in South Orientation in Hot Arid Zone

In the framework of achieving advanced (sophisticated) light shelf system for deep office spaces in south in hot, arid zones, this study is based on the use of the parametric design approach in creating and investigating various combinations of the main design parameters of light shelf systems, in order to determine the design indicators and the key design elements that can help in developing and optimizing the performance of such daylight systems. Therefore a “819” study cases were created and tested in the previous phase of this study, as well as a “16” study cases have been tested in this study that produced from one hypothetical optimized parametric study case which was established by integrate the main design features of the best two case studies in the results of the previous study phase, in term of daylighting and energy consumption performance. This study has identified several basic designs and considerations for developing and optimizing the light shelf systems, in addition to the invention of two sophisticated design cases for deep office spaces with different ceiling heights (3.30 & 3.80 m.) in south in hot, arid zones (New Cairo area).

A preliminary study on the performance of an awning system with a built-in light shelf

Increased energy consumption is an ongoing research concern worldwide. In particular, uses of ongoing studies are focusing on improving indoor comfort via the development of double-skin facades that combine various skin element technologies. In light of this, this study aims to develop an awning system with a built-in light shelf, which is a new type of system combining an awning and a light shelf. It also confirms the effectiveness of this system based on a full-scale test bed by deriving the energy reduction performance and improvements in the comfort of the indoor lighting. The awning system proposed in this study has a built-in light shelf below the awning, and there is a cut-out hole in the cover of the awning so that natural light can hit the shelf. As a result, the system successfully prevents an increase in the indoor temperature by blocking the incoming sunlight and introduces natural light deep within the interior, improving the light uniformity and reducing the lighting energy consumption. The effectiveness of the system was demonstrated by analyzing the improvement in the indoor illumination uniformity and the cooling and lighting energy savings provided by the proposed system compared with existing awning and light shelf systems.

Development and Performance Evaluation of Light Shelves Using Width‐Adjustable Reflectors

In recent years, there has been an increase in the consumption of energy for lighting purposes, which has led to an increase in the number of studies being conducted on this subject. Most studies have focused on light shelves, which are daylighting systems used for reducing the lighting energy required for the interiors of buildings. However, the existing light shelves cannot actively deal with external environmental factors, which often lead to an infringement of the right to light during the night when the performance of the light shelf deteriorates. Therefore, in this study, we propose a light shelf with a width‐adjustable reflector and verify its validity using a testbed. The reflector of the proposed light shelf system is modularized so that the length can be adjusted in stages. The optimum width of the light shelf is calculated in terms of the energy reduction and uniformity ratio improvement, and the obtained optimum width is varied depending on the season. We find that the width‐adjustable reflector can save 20% and 21.6% more lighting energy than light shelves with fixed reflector widths of 0.3 m and 0.6 m, respectively.

A Study on Development of a Curved Light Shelf System

A Study on Development of a Curved Light Shelf System

반사율 변경이 가능한 롤링타입형 광선반 개발

Purpose: Recently, lighting energy consumption in buildings has been gradually increasing and more studies are being carried out in order to solve this problem. Especially, the efficiency of the light-shelf system, which is a natural lighting system, has been recognized as a potential solution in addressing this problem and so various studies regarding the light-shelf system are being conducted. However, if high luminance material is used for the light-shelf system, glaring may occur in certain circumstances even though such material increases efficiency, and there are also difficulties related to maintenance and management in the case of an external light-shelf system. Therefore, the purpose of this study is to suggest modifications in relation to the reflectivity of the light-shelf system and introduce a rolling type light-shelf system with built-in cleaning equipment. In addition, a performance evaluation technique was established to verify its effectiveness. Method: In this study, we reviewed previous studies related to the light-shelf system and its performance. Then a testbed was established to assess the performance of the rolling-type light-shelf system suggested in this study. Also, the performance of the rolling-type light-shelf system suggested in this study was compared and analyzed with that of existent light-shelf systems in order to better verify the performance, and the uniformity ratio of illumination and lighting energy consumption were calculated for this purpose. Result: The results of the performance evaluation are as follows. 1) The performance evaluation result of the light-shelf system on the day of the summer solstice shows that <TEX>$30^{\circ}$</TEX> is appropriate for the angle of light-shelf system, and the depth of the incoming natural light also increases as the angle of the light shelf increases. 2) It is possible to improve the uniformity ratio of illumination by increasing the reflectivity of the light shelf, and the reason for this is the increase in the amount of incoming light entering indoors due to the increased reflectivity of the light shelf. 3) The rolling type light-shelf system suggested in this study enables energy saving in comparison with existent light-shelf systems, and when the external illuminance decreases to 60,000 lx and 40,000 lx during the summer solstice due to factors such as the weather, the suggested light-shelf system can save energy by 12.1% and 5.1% respectively. Thus the light-shelf system proposed in this study is deemed to be effective in reducing energy costs.

Study on movable light-shelf system with location-awareness technology for lighting energy saving

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.

Energy Efficient Building Design and Estimation of Energy Savings From Daylighting in Chennai

ABSTRACTThe objective of this study was to perform a daylighting analysis on the light shelf system installed to save energy in office buildings in Tamil Nadu. For this, a building was chosen for energy analysis simulation using Ecotect software. Light shelves with four different patterns of diffuse reflections in increasing levels were chosen at the preliminary stage. The illuminance was highest in the mirror finish followed by high reflective, medium reflective and light reflective partitions. The light shelf with the mirror finish was chosen for the economic analysis since it is more efficient than other diffuse reflection panels. Results of the economic analysis showed that lighting energy consumption was reduced by an average of 30% using the mirror finished light shelf with energy efficient lamps, compared with the base case model where lighting control was not applied. A simple payback period, calculated for the model with the light shelf system installed was 6 years and 4 months.