Performance Evaluation Depending on Separation Distance Between Skylight and Light Shelf: Focusing on Variation of Distance of Indoor Space

Jiun Her,Hangwoo Lee,Yongseong Kim 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.11

The light shelf, which is a natural light system, has been intensively studied as its efficiency is recognized. However, previous studies on the light shelf have not considered various depths of space, and the performance of light shelf design has not been sufficiently studied with respect to the separation distance between a skylight and a reflection board. Therefore, the purpose of the present study is to establish the fundamental data for light shelf design by deriving an appropriate separation distance between a skylight and a reflection board, considering various depths of space. In the present study, a simulation software program, Radiance, was employed, and the performance evaluation was limited to the environment on the summer solstice when the energy consumption in buildings is the highest. The depth of space was established from 3 m to 8 m at intervals of 1 m for the performance evaluation. The separation distance between a light shelf and a skylight was set to be 50 mm, 100 mm, 150 mm, 200 mm, and 250 mm. The performance evaluation was conducted by deriving the depth of space and uniformity that satisfied the standard of 400 lx. The following conclusions were drawn from the present study. 1) The depths of space that satisfied the standard of 400 lx depending on the separation distance between the light shelf and the skylight established in the present study were the same at the light shelf angle of 0̊. However, the performance of the light shelf depending on the separation distance between the light shelf and the skylight was dependent on the depths of space at the light shelf angle of 30̊. 2) With regard to the uniformity depending on the separation distance between a light shelf and a skylight, the uniformity was excellent in the case where the separation distance between a light shelf and a skylight was equal to or shorter than 100 mm, while the uniformity was poor in the case where the separation distance was equal to or longer than 150 mm, which should be considered in the design of a light shelf. In the present study, appropriate factors related to light shelf design were identified by analyzing the performance of a light shelf depending on the separation distance between a light shelf and a skylight. Various studies may need to be conducted in the future about the performance variation on the basis of the separation distance between a light shelf and a skylight depending on the depth of space in controlling the angle of a light shelf.

A Study on Performance Evaluation of Mixed Light Shelf Type According to the Angle of Light Shelf

Woori Chae,Heangwoo Lee,Yongseong Kim 보안공학연구지원센터 2015 International Journal of Smart Home Vol.9 No.1

A light-shelf, one of natural lighting methods, has advantages in constructability and economic feasibility in comparison with other passive natural lighting system. A movable light-shelf enables a user in a room to adjust the angle according to his or her preference to control the amount of indoor light. In addition, a light-self serves as a shield to the intense light on window sides when the solar light is strong to relieve glare. The purpose of this study was to investigate the effect of angle adjustment of a mixed type light-shelf on indoor natural lighting and determine efficient light-shelf lighting performance values by using an actual size test-bed. This study was conducted in the following procedures: 1) Previous studies were investigated to analyze the definition of a light-shelf and identify experimental factors for a light-shelf; 2) On the basis of previous studies, the light-shelf experimental factors were set up with reference to the illumination values under clear sky at the meridian transit altitude in each season to perform an experiment; and 3) The performance of the light-shelf was evaluated to examine the effectiveness. The performance evaluation was performed for each season according to the solar altitude of the mixed light-shelf. The indoor distribution of illumination was analyzed on the basis of the day light introduction depending on the angle of the mixed type light-shelf to verify the correlation with variables and the efficacy.

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

Gangmin Jeon,Heangwoo Lee,Yongseong Kim 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.10

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.

실내공간 깊이와 광선반 규격 변화에 의한 광선반 성능평가 시뮬레이션 연구

이행우(Lee, Heang-Woo),김덕수(Kim, Duk-Su),김용성(Kim, Yong-Seong) 대한건축학회 2013 대한건축학회논문집 Vol.29 No.3

There are so much of researches underway in order to find out the solution to 22% higher lighting energy consumed by a building. In particular, many studies on light shelves are ongoing due to the merits such as guiding light inflow into deep inside a building as well as allowing excessive shading. The existing literatures fail to provide adequate basis in designing light shelves for various sized space, as they are limited only to performance evaluation on variables of light shelves. In this study, performance evaluation on light shelves was performed by dividing space depth at the interval of 1m for 3~8m, to draw a conclusion as follows: 1)First, the analysis resulted in 6m, 4m and 3m of space depth that entirely meets standard intensity of illumination 400lux, with light shelves not installed for Winter Solstice, Summer Solstice and Spring/Autumnal Equinox Day, while it showed 4∼6m, 3∼4m and 3∼4m with light shelves installed in depth and at angle as specified by this study, telling us there was no Daylighting Efficiency by changes in space depth except Summer Solstice even with light shelves installed. 2)The performance of light shelves depended on, in order, the specular surface of light shelves, the reflection of ceiling and the position of third reflection to be changed by space depth which have to be considered as an element in designing. Especially in the cases of at the angle of 20° during Winter Solstice and angle of 30° during Spring/Autumnal Equinox Day, extra care should be paid while designing a light shelf that will directly guide light inflow to indoor through its specular surface. 3)As the depth of light shelf increased, the shade size caused by light shelfrose along with higher uniformity ratio of illuminance, while it reduced with less uniformity ratio of illuminance as the angle of light shelf increased. 4)Considering the space depth set by this study, light inflow and reflection type through light shelf and uniformity ratio of illuminance, the adequate proposals were drawn as an external light shelf of 10° and 0.3m in depth, an external light shelf of 20° and 0.3m in depth, and an external light shelf of 30° and 1.2m in depth, for Winter Solstice, Spring/Autumnal Equinox Day, and Summer Solstice, respectively. However, for Summer Solstice, it was determined that the most appropriate proposal was an external light shelf of 0.3m in depth, considering the fact that an external light shelf with the angle of 30° is efficient in general and that the angle of a light shelf is changed by operation. This study provides meaningful performance evaluation on light shelf by space depth. Further multilateral studies will be required in consideration of the height and the depth of space as the element of space size.

주거공간 내 사용자인식기술 적용 조명에너지 저감 광선반 시스템 연구

서태원(Seo, Tae-Won),이행우(Lee, Haeng-Woo),김용성(Kim, Yong-Seong) 대한건축학회 2012 대한건축학회논문집 Vol.28 No.11

The current energy consumption of buildings occupies 23.5% of the total energy consumption in Korea, a high ratio, of which about 22% is consumed through lighting energy. For that reason, various experiments and research have been undertaken to reduce the energy consumption needs of indoor artificial lighting. This study suggests a light-shelf system applied with user recognized technology based on considerations of the light-shelf system and user recognized technology, and verified the possibility of introducing it to residences, and its effectiveness by comparing the results of energy reduction performance evaluations for the proposed light-shelf system with the user recognized technology and that with user unrecognized technology. The light-shelf system applying user recognized technology is a system that allows the occupant to set the luminance value of the room so that the light-shelf system and lighting can be interlocked and provide the luminance value requested by the occupant. In order to verify the energy reduction effects of the light-shelf system with the user recognized technology applied, this study has calculated the power consumption of lighting energy for a user unrecognized fixed light-shelf system, a user recognized fixed light-shelf system and a user recognized variable light-shelf system. From the results, when comparing the user unrecognized fixed light-shelf system and the user recognized fixed light-shelf system, Case A did not generate a reduction in energy consumption, and Case B saw a 4.4% reduction of lighting energy consumption levels. Case C generated a 13.3% reduction of lighting energy consumption. When comparing the user recognized fixed light-shelf system and the user recognized variable light-shelf system, power consumption was equivalent in Case A of one occupant and A, B and A, Case C for 2 occupants, while a 13.3% energy reduction was achieved for Case B of 1 occupant and B, Case C of 2 occupants. Case C of 1 occupant also achieved a 15.2% lighting energy consumption reduction. The user recognized variable light-shelf system showed the largest reduction of lighting energy power consumption, followed by the user recognized fixed light-shelf system and the user unrecognized light-shelf system in order of the reduction of lighting energy power consumption from user recognition.

천장의 기하학적 형태에 따른 광선반 성능평가 시뮬레이션 연구

이행우(Henagwoo Lee),김용성(Yongseong Kim),서장후(Janghoo Seo),김덕수(Duk-Su Kim) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.4

Light-shelf is one of the most efficient natural lighting systems due to the improved function of the inflow level of the outdoor natural light. However, the existing research on the light shelf limits to the rectangular parallelepiped space, so do not provide sufficient data for various shapes of spaces. Thus, this study aims at deriving proper plan and relationship of the light shelf through its performance assessment depending on the indoor space shapes and utilizing them as basic data of light shelf design. The conclusions are as follows:1) for 6m space depth, standard intensity of illumination satisfaction depth has shown 8.3%~26.3% improvement through the adjustment of the angle and width when installing light shelf compared to no light shelf installation; 2) -30˚, -20˚ and -10˚ light shelves set by this study play only as a blind regardless of the shape of ceiling on the summer solstice, and it is unsuitable; and 3) this study has derived proper plan of light shelf upon space shapes based on energy reduction and indoor evenness. The study results provide expanded data of the performance assessment of the light shelves according to the different space shapes and light shelf factors, which serves as a basis of the light shelves designing.

결정면 적용 광선반 채광성능 평가 연구

이행우(Heangwoo Lee),Kyle Eric Rogers,서장후(Janghoo Seo),김용성(Yongseong Kim) 대한설비공학회 2015 설비공학 논문집 Vol.27 No.8

Recently, many research studies have been carried out on the efficiency of light-shelf daylighting systems, especially comparing performance improvements and the limitations of reflective surfaces and their lighting performance. In this study, a crystal face reflective surface is proposed. The objective of the study is to evaluate the lighting performance of a crystal face light-shelf through a performance study. The performance study was carried out in a full scale test-bed in order to calculate the light distribution and energy consumption utilizing the standard indoor illumination as an index. The conclusions of the performance study are as follows. 1) The optimal angle of incidence for daylighting for both the operable flat type light-shelf and the crystal face light-shelf are taken in the natural environment on the dates of the winter and summer solstices, as well as the autumn and spring equinoxes. 2) The application and installation of the crystal face light-shelf can produce a 29.9%~34.3% increase of light distribution within the indoor space. However, the increase of light distribution can also lead to a decrease in the uniformity ratio, a design challenge that should be considered when applying a crystal face light-shelf. 3) It is possible to achieve a 7.98%~13.3% greater reduction in energy consumption when applying a crystal face light-shelf than when applying a flat type light-shelf. The increase in the number of crystal faces should concur with the analysis of the energy reduction. A limitation of the study is that only one predetermined pattern was performance tested for a crystal face light-shelf. In order to carry out further research on crystal face light-shelves, additional performance studies are needed based on alternative patterns and designs.

Effectiveness of a perforated light shelf for energy saving

Lee, Heangwoo,Kim, Kyungsoo,Seo, Janghoo,Kim, Yongseong Elsevier 2017 Energy and buildings Vol.144 No.-

<P><B>Abstract</B></P> <P>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.</P>

반사판의 폭 조절이 가능한 서랍형 타입의 가동형 광선반 개발 연구

김다솜(Dasom Kim),이행우(Haengwoo Lee),서장후(Janghoo Seo),김용성(Yongseong Kim) 대한설비공학회 2016 설비공학 논문집 Vol.28 No.9

Due to the recent increase in lighting energy consumption in buildings, there are a growing number of studies seeking solutions this problem. The effectiveness of light-shelves as natural lighting systems to solve this problem has been recognized, and various studies regarding such systems are being carried out currently. However, the lighting efficiency of light-shelves decreases if illumination intensity is low-such as at night time, and it also obstructs the views of building occupants. Therefore, the purpose of this study is to examine a movable drawer type light-shelf which allows for the width of the reflector to be adjusted and verify its performance through a simulated test-bed. The following conclusions were reached. 1) The purpose of this study is to solve the problem previously associated with the light-shelf system- of obstructed views-by responding to external environments and minimizing the width of the light-shelf at night time when the efficiency of the light-shelf declines. 2) The proper variables of the movable drawer type light-shelf which enables the width adjustment of the reflector were ascertained in this study according to four solar terms : a width of 0.6 m at an angle of 20°, a width of 0.4m with an angle of 20°, and a width of 0.1 m with an angle of 20° were determined for the summer solstice, fall/spring equinoxes, and winter solstice respectively; revealing that width adjustment of the light-shelf is a significant factor. 3) The movable drawer type light-shelf which enables\width adjustment of the reflector suggested in this study can reduce the lighting energy consumption by 18.7% and 14.3% in comparison to previous light-shelves with a fixed width of 0.3 m and 0.6m, indicating that it is effective for saving energy.

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

Lee, Heangwoo,Seo, Janghoo,Kim, Suktae Elsevier 2018 Building and environment Vol.144 No.-

<P><B>Abstract</B></P> <P>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.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Location of the diffusion sheet determines the performance of light shelf. </LI> <LI> Glass of the window is most appropriate to apply diffusion sheet. </LI> <LI> Diffusion sheet can improve Uniformity and glare of the light shelf. </LI> </UL> </P>