Daylight in buildings based on tubular light guides

doi:10.1016/j.jobe.2021.102608

Journal of Building Engineering

Volume 44, December 2021, 102608

https://doi.org/10.1016/j.jobe.2021.102608 Get rights and content

Highlights

•
Illuminance measurements from tubular light guide.
•
Study of reflectance influence on the light guide efficiency.
•
Daylight simulations of light guides for determination of illuminance and efficiency with respect of different sky conditions.
•
Light guide energy efficiency estimation.

Abstract

Tubular light guides (TLGs) represent a solution for energy efficient performance of light during a day based on the daylight transport into building interiors. While daylight from windows sufficiently illuminates rooms close to building envelopes the light guides improve visual environment and perception of architectural space in deeper parts of interiors. The main aim of this study is focussed on the evaluation of efficiency of two selected TLG systems experimentally tested in temperate climatic conditions. Firstly, daylight illuminance measurements under the light guide installations were performed for one year period with documentation of the typical daily illuminance courses. The measurement results show differences between daylight efficiency of these systems. Secondly, spectral reflectance of the light guide tubes was measured and analysed to find out material influence on light transport effectiveness. Finally, daylight simulations were carried out applying software HOLIGILM for determination of daylight illuminance under the TLG of various dimensions. The study gives general overview about potentials of daylighting applications for straight light pipe systems.

Introduction

Tubular light guides (TLGs) transport daylight for long distances, generally into deeper parts of building spaces due to multi-reflections of their inner reflective surfaces [1,2]. They represent opportunity for better performance of daylight in buildings, distribution of sunlight and reduction of electricity consumption for lighting [3,4]. Nowadays, TLGs are widely used for daylighting of interiors in various climatic localities. Especially, their applications are convenient in deep plans [2,5] and rooms without windows. TLG systems vary in materials of components and construction details which are designed to maximize their light transmission [[6], [7], [8], [9]]. Common tubular daylight guiding systems consist of transparent domes, tubes with reflective inner surface and light scattering diffusers. A position of the light guides in roofs or facades and their connection with building constructions influences effectiveness of light transmission of the systems and contributes to reduction of energy consumption. Moreover, TLGs as architectural elements can find applications in various types of buildings. Principles and recommendations for daylight guiding system design are specified in technical documents of the International Commission on Illumination [10,11].

The photometry of TLGs [12] and light measurement analyses gave data about their optical properties and performance [13]. Studies about light guides modelling using simulation tools [14] as well as experimental and analytical studies of light guides were provided [15,16]. Models for prediction of light guide performance were developed e.g. in Refs. [[17], [18], [19]]. An analytical light guide description for the interior illumination modelling was completed [20] with consideration of different sky luminance distributions [21]. For modelling of illuminance distribution on the reference plane and straight cylindrical light guide efficiency software HOLIGILM [20] was presented. Lately HOLIGILM model was extended for the design and evaluation of bended TLGs [22]. These models were used for prediction of indoor illuminance levels on the reference plane in various interiors [23,24]. Experimental measurements were undertaken to optimize daylight guiding system design. Summary of results acquired from tested systems [25] provided a basis for optimisation and formulation design rules. Building users' attitudes [26] as well as cost efficiency and benefits of TLG systems were also monitored [27,28].

Case studies and post occupancy evaluations are wildly used for assessments of daylighting in real buildings [29,30]. Positive environmental impact of daylighting plays important role for healthy indoor climate and sustainable building design is underlined in Ref. [31]. The daylight studies are commonly based on in-situ measurements and daylight simulations. Some of these studies are focused on evaluation of light guide effects on indoor visual environment [[32], [33], [34], [35], [36]], energy savings and daylight transport efficiency [37,38].

The light guide system efficiency depends on its geometry and optical properties of components as well as on the location in building envelope, orientation to the cardinal points and influences of surrounding obstructions.

The practice shows that very similar light guides of the same dimensions could supply different interior illuminances under the same ambient daylight conditions. Therefore, it is important to provide studies about applications of available light guiding systems already in early stages of the building design.

A case study of indoor daylight illuminance from two TLGs of comparable dimensions but different optical properties is the main goal of this paper. The research objective is to find properties of selected light guide products, investigate light reflectance of the TLGs inner tube surfaces as well as determination of efficiency of the light guiding system based on experimental measurements and daylight simulations.

Section snippets

Methodology of investigation of TLGs properties

Two comparable TLGs were experimentally investigated in temperate climatic conditions in location Ostrovačice in Brno - country district in the Czech Republic (geographical latitude 49°12′39.08″ N, longitude 16°24′34.1″ E, altitude 330 m). Interior illuminance measurements were carried out in test chambers for one year period to assess light transmittance of the installed TLGs under various exterior conditions. Measured illuminance data were statistically evaluated. The statistical analysis was

Results of daylighting measurements

Results from daylight illuminance measurements and spectral reflectance yielded data are useful for the evaluation of the investigated light guides and elaboration of application strategies. Sensors 1 to 5 were installed in chamber 1 and sensors 6 to 10 in chamber 2. During measurements all sensors were synchronised with the external sensor 11. Examples of daily illuminance profiles on August 13, 2015 presenting the clear sky condition and on August 15, 2015 documenting dynamic illuminance

Spectral measurement results

Spectral measurements in the optical radiation range were performed in accordance with standards [40]. They show differences between reflectances of LP1 and LP2 inner tube surfaces, as it was assumed. Total reflectance in the range of 300 nm–2500 nm (Fig. 7) is 77.7% for sample LP1 and 96.4% for sample LP2. The lower reflectance of the LP1 tube is caused by reduction of incident energy in the infrared spectral range between 1000 nm and 2500 nm. This finding is important for architectural design

Daylighting simulation

The data from daylight measurement were compared to daylight simulations. The light guide evaluation was finally completed with a daylight simulation study focused on efficiency of light guides of different dimensions and various reflectances under clear and overcast sky conditions which gives general overview about potentials of the straight light pipe systems for daylighting applications.

Conclusion

The evaluation of light guides was based on the daylight measurements and simulations. The long term measurements in this study were focused on daylight illuminance levels of two samples of light guiding systems with comparable dimensions in test chambers. Differences in achieved internal horizontal illuminance in chamber 1 and chamber 2 give information about variations of daylight transmission of tested light guides. Internal illuminance levels monitored for LP1 and LP2 vary from about 30 lx

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This article has been elaborated under the project No. LO1408 “AdMaS UP - Advanced Materials, Structures and Technologies”, supported by Ministry of Education, Youth and Sports under the “National Sustainability Programme I” and VEGA 2/0017/20. The daylight measurements were supported by company TOPVET, Ostrovačice. Authors are grateful to Associate Professor Pavel Rovnaník PhD. for providing the spectral measurements.

References (48)

G. Oakley et al.
Daylight performance of light pipes
Sol. Energy
(2000)
S. Lu et al.
Multi-layered and multi-dimensional suitability evaluation of tubular daylight guidance systems
J. Build. Eng.
(2020)
A. Rosemann et al.
Lightguide applications for daylighting systems
Sol. Energy
(2005)
M. Kocifaj et al.
HOLIGILM: hollow light guide interior illumination method – an analytic calculation approach for cylindrical light-tubes
Sol. Energy
(2008)
M. Kocifaj et al.
Availability of luminous flux below a bended light-guide: design modelling under optimal daylight conditions
Sol. Energy
(2012)
M.S. Mayhoub et al.
The costs and benefits of using daylight guidance to light office buildings
Build. Environ.
(2011)
F. Sharp et al.
The use and environmental impact of daylighting
J. Clean. Prod.
(2014)
M. Al-Marwaee et al.
Tubular guidance systems for daylight: achieved and predicted installation performances
Appl. Energy
(2006)
K. Vasilakopoulou et al.
Analysis of the experimental performance of light pipes
Energy Build.
(2017)
A.R. Day et al.
The use of the planning system to encourage low carbon energy technologies in buildings
Renew. Energy
(2009)

S.C.J. Smith, N.C. Ruck, The passive transmission of natural light to deep building interiors. in: Proceedings 2nd...

K. Vasilakopoulou et al.

Performance prediction and design optimisation of an integrated light pipe and artificial lighting system

Int. J. Sustain. Energy

(2016)

V. Garcia Hansen, I. Edmonds, Natural illumination of deep-plan office buildings: light guide strategies, in:...

I.R. Edmonds et al.

Daylighting enhancement with light guides coupled to laser-cut light-deflecting panels

Light. Res. Technol.

(1995)

D. Carter

LRT Digest 2 Tubular daylight guidance systems

Light. Res. Technol.

(2014)

P. Greenup, I.R. Edmonds, Novel technologies for improved daylighting of high rise office Buildings, In Towards...

Hollow light guide technology and applications, Technical Report

Commission Internationale de l’ Eclairage

(2005)

Tubular daylight guidance systems, Technical Report

Commission Internationale de l’ Eclairage

(2006)

A. Rosemann et al.

The photometry of hollow light guides

Light. Res. Technol.

(2005)

D.J. Carter

The measured and predicted performance of passive solar light guide systems

Light. Res. Technol.

(2002)

S. Chirarattananon et al.

Simulation of transmission of daylight through cylindrical light guides

J. Susutain. Energy Environ

(2010)

H.W. Li Danny et al.

An analysis of light-guide system via full-scale measurements

Appl. Energy

(2010)

S. Samuhatananon et al.

An experimental and analytical study of transmission of daylight through circular light guides

Leukos

(2011)

X. Zhang et al.

Mathematical model for the performance of light guides

Light. Res. Technol.

(2000)

Cited by (14)

Optimizing of architectural geometry and tubular daylight guidance system based on genetic algorithm to enhance daylighting and energy performance in underground office buildings
2024, Journal of Building Engineering
Tubular daylight guidance system (TDGS), when properly selected and designed, can reduce excessive uncontrolled solar gain and daylight in underground spaces, thereby improving the building's energy performance and visual comfort. However, various questions related to their adaptation to different climates, design and optimization methods have not been answered. The aim of this paper is to show that different TDGS designs are needed even in geographic regions with similar climatic conditions. The objective function was defined as minimizing energy use intensity and maximizing daylight use. Sensitivity analysis indicated that the radius of TDGS was the most contributing of all the variables, followed by the aboveground building shape parameter, while the effects of the other variables varied widely. Therefore, this paper proposes a comprehensive optimization framework for small underground office buildings based on genetic algorithmic methods to seek the optimal design for applying tubular daylight guidance system (TDGS). Simulation studies were conducted in Ladybug and Honeybee software and further comparative optimization studies were conducted using the Strength Pareto Evolutionary Algorithm (SPEA-2) in the Octopus tool and the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) written in MATLAB. After applying the proposed optimization algorithm to the simulation study, the results demonstrate that the daylighting performance metric (UDI) has been improved to 53.2%–66.3% and the energy performance metric (EUI) has been reduced to 13.4%–78.4%, compared with the benchmark building. The research contribution is to propose a workflow that integrates parametric design, sensitivity analysis and NSGA-II to optimize TDGS designs with various parameters and ranges. In addition, the study proposes guidelines for designing TDGS in the five investigated cities.
Location-specific optimization of free conic dome daylight collector for improved light pipe performance
2024, Building and Environment
Tubular daylighting devices have emerged as efficient methods for transporting sunlight into interior spaces, offering numerous benefits in energy conservation, lighting quality, and occupant comfort. Collectors play a pivotal role in deciding system efficiency within the system components. Their primary function is to intercept sunlight from various angles, including low angles, and redirect it into light tubes with minimal loss. Amongst different collectors available, dome-shaped collectors are used widely in literature and commercially due to improved performance, adaptability, simple geometry, and ease of installation and maintenance. The design of dome collectors is a critical aspect of their effectiveness. They can vary in size, shape, and orientation to maximize solar gain. The studies evaluating the effect of height to diameter ratio (h/d) of the dome obtained by varying the convexity are minimal. The paper studies the influence of the h/d ratio on the performance of the spherical dome collector by analyzing the Spatial Daylight Autonomy (sDA₁₅₀) and illumination profile. As a next step, the study used a Laser Cut Panel (LCP) as a light redirection element for assessing the enhancement in sDA₁₅₀ and uniformity.
Later, the study proposes a novel methodology for optimizing the dome shape to improve the performance for each location using TracePro software by varying the apex height, coordinates of the control point, conic constant, and curvature of the conic segment to meet the performance criterion. Incorporating LCP with the new collector design significantly improves the daily sDA₁₅₀ values on the target plane, giving comparatively consistent natural lighting during the hours of consideration.
Comprehensive investigation on lighting and energy-saving performance of lighting/heating coupled tubular daylighting devices integrated with nanofluids
2024, Applied Thermal Engineering
Feasible regulation of the solar visible and infrared spectrum is a promising technology for energy-efficient buildings. Our recently published work has proposed a lighting/heating coupled tubular daylighting devices (LH-TDDs) integrated with nanofluids to track the trade-off between indoor visible light gain and near-infrared shielding and demonstrated its excellent lighting/heating decoupling performance. To further evaluate the application potential of the LH-TDDs, the present work develops a comprehensive evaluation method that considers both lighting and energy-saving performance. In detail, the LH-TDDs system was investigated using both the numerical models and Energyplus software. The results on lighting performance demonstrate that the filtration of nanofluids hardly affects the lighting quality of LH-TDDS, but will instead enhance lighting uniformity and lessen glare risk. Meanwhile, the energy consumption simulations indicate that LH-TDDs achieve energy saving from three approaches, namely, lighting energy saving, thermal energy output, and air-conditioning energy-saving, and 100 ppm nanofluid can improve the total energy-saving amount by 43.6 % in Harbin, China. The findings of this paper can accelerate the application of LH-TDDs, and the evaluation system elaborated in this work may provide some useful clues for the assessment of other nanofluids-based transparent envelopes.
Thermal analysis of tubular daylight guidance system on an insulated flat roof with overlying soil
2024, Solar Energy
As an emerging passive daylighting technology, tubular daylight guidance systems (TDGSs) are increasingly used in low-energy buildings. However, TDGS may become a thermal bridge to increase indoor air conditioning load. To avoid an increase in total energy consumption, the thermal analysis of a flat roof section with a TDGS is simulated using CFD in this work. Additionally, the simulation compares the heat transfer performance of a conventional TDGS with eight different designs TDGS that contain additional glass unit. The findings show that TDGS has a thermal bridging effect on an insulated flat roof with overlying soil. The additional glass unit in the middle of the conventional TDGS with diameter 500 mm decreases its overall heat transfer coefficient by 53 %. Further, the same thickness of glass is divided into 4 layers and evenly distributed inside the TDGS with diameter 500 mm, which can reduce the total heat transfer coefficient of the conventional TDGS by 67 %.
Daylight performance of collector-diffuser combinations in light pipe systems at different geographical locations
2024, Solar Energy
Incorporating daylight inside occupied spaces has several benefits, including reduced lighting load, improved mental and physical health of occupants, and increased productivity during working hours. Several Innovative daylighting systems that utilize advanced technologies and design approaches are devised and tested to bring natural light into occupied spaces. Amongst them, the Tubular Daylighting Devices (TDD) have immense potential to trap the sunlight and carry it to enclosed/dimly lit areas, especially in tropical climates.
The careful selection of system components dictates TDD's spatial and temporal illumination performance. The present study aims to analyze and correlate the performance of various TDD systems with different collector-diffuser configurations widely reported in the literature and used commercially. The study uses the Daily Useful Daylight Illuminance (DUDI) paradigm and uniformity criterion to assess the performance of carefully chosen collectors, namely, hemispherical dome, prismatic dome, and faceted collector, with the selected diffusers: flat plate acrylic, hemispherical dome, flat prismatic, and flat Fresnel lens. The study encompasses the identification, modeling, and simulation of different configurations throughout the year at four chosen cities in India. Results indicate that the maximum and average lighting level measured is high in the case of the hemispherical collector when paired with flat diffusers at all seasons and cities considered for the study. A matrix of different configurations of system components is tabulated for each location based on a predefined criterion. The increase in diameter of the tube improved the lighting level above 150 lx even at a distance of 1.5 m from the center, and splitting the light pipe into two pipes of an equivalent cross-sectional area improved the end illumination levels at the periphery of the room (10–25 %) making it better in terms of both illuminance and uniformity when paired with hemispherical/faceted collector and flat diffuser.
Coupling convolutional neural networks with gated recurrent units to model illuminance distribution from light pipe systems
2023, Building and Environment
Existing methods used to predict the performance of light pipe systems depend on empirical models based on specific conditions (e.g., climate, configuration). As a result, they are not readily applicable to conditions outside the initially considered boundaries. We propose machine learning (ML) models as an alternative to existing empirical models. 147 ML models were trained to predict illuminance distribution from a light pipe. Three ML algorithms were considered – convolutional neural networks (CNN), gated recurrent units (GRU) and an ensemble of CNN + GRU. The CNN + GRU model (R² = 0.987) showed a higher predictive performance than the GRU model (R² = 0.981). Additionally, the CNN + GRU model required less time to train and was significantly lighter than the GRU model; these attributes make the ensemble CNN + GRU model preferable during deployment. The developed models also offer better generalization capabilities than existing empirical models and are easily subjected to continued learning as more data becomes available.

View all citing articles on Scopus

View full text

Daylight in buildings based on tubular light guides

Highlights

Abstract

Introduction

Section snippets

Methodology of investigation of TLGs properties

Results of daylighting measurements

Spectral measurement results

Daylighting simulation

Conclusion

Declaration of competing interest

Acknowledgement

Sol. Energy

J. Build. Eng.

Sol. Energy

Sol. Energy

Sol. Energy

Build. Environ.

J. Clean. Prod.

Appl. Energy

Energy Build.

Renew. Energy

Performance prediction and design optimisation of an integrated light pipe and artificial lighting system

Int. J. Sustain. Energy

Daylighting enhancement with light guides coupled to laser-cut light-deflecting panels

Light. Res. Technol.

LRT Digest 2 Tubular daylight guidance systems

Light. Res. Technol.

Hollow light guide technology and applications, Technical Report

Commission Internationale de l’ Eclairage

Tubular daylight guidance systems, Technical Report

Commission Internationale de l’ Eclairage

The photometry of hollow light guides

Light. Res. Technol.

The measured and predicted performance of passive solar light guide systems

Light. Res. Technol.

Simulation of transmission of daylight through cylindrical light guides

J. Susutain. Energy Environ

An analysis of light-guide system via full-scale measurements

Appl. Energy

An experimental and analytical study of transmission of daylight through circular light guides

Leukos

Mathematical model for the performance of light guides

Light. Res. Technol.