Light Pipe Research Articles

Daylight performance of horizontal light pipe with egg-crate reflector in the tropics

Horizontal Light Pipe (HLP) is one of a light transport system that can guide daylight deeper into building interiors. Improvement of HLP’s light distribution by installing an egg-crate reflector at its opening distribution was conducted. The study’s aim was to evaluate and explain the daylight performance of HLP with an egg-crate reflector at office space in the tropics. Experiment with physical scaled model 1:5 was used as a research method. Illuminance value, Daylight Factor (DF), uniformity ratio and diversity of illuminance of an office space lit by side window (base case) were compared to the office space lit by side window and HLP with an egg-crate reflector (case), simultaneously with daylighting standards. The results showed that HLP with egg-crate reflector improved daylight level and distribution. Improvement of DF and illuminance level were in the range of 16.6 % to 56.6 %. The uniformity ratio of the base case was in the range of 0.35 to 0.45, while in the case was in the range of 0.48 to 0.66. The diversity of illuminance of the base case at a low altitude of the sun (15:00) exceeded 5:1 while in the case was kept lower than 5:1 at all the measurement time.

Technological Review of Tubular Daylight Guide System from 1982 to 2020

T.D.G.S., “Tubular Daylight Guidance Systems”, are natural lighting processes based on the transport of light. In 1990, they were judged by Littlefair as the most innovative technology in daylighting [1]. From 1982 to 2020, this paper is a state of the art on the different processes of tubular daylight guide systems. The key words used to carry out the census are light pipe; light tube; light guide; sun pipes; solar pipes; solar light pipes; daylight pipes; tubular skylight; sun scoop; tubular daylighting device; tubular daylight guide systems; mirrored light pipe. A classification by type of process is proposed (collection, transport or diffusion) for each technology identified in the literature.

Technological Review of Tubular Daylight Guide System from 1982 to 2020

T.D.G.S., “Tubular Daylight Guidance Systems”, are natural lighting processes based on the transport of light. In 1990, they were judged by Littlefair as the most innovative technology in daylighting [1]. From 1982 to 2020, this paper is a state of the art on the different processes of tubular daylight guide systems. The key words used to carry out the census are light pipe; light tube; light guide; sun pipes; solar pipes; solar light pipes; daylight pipes; tubular skylight; sun scoop; tubular daylighting device; tubular daylight guide systems; mirrored light pipe. A classification by type of process is proposed (collection, transport or diffusion) for each technology identified in the literature.

Analysis of light extraction in light pipes by linear and elliptical grooves using different source aperture angles

An analytical and numerical analysis of light extraction from light pipes using total internal reflection grooves with linear and elliptical profiles is presented. We performed the study considering light sources with different aperture angles, such as sunlight delivered by optical fibers and LEDs. With this analysis, we propose an analytical model based on the edge ray concept that allows selecting the most convenient profile, size, and orientation of the groove to extract light with a desired illumination area according to the source aperture angle employed in the light pipe system. We also have numerically found that for sources with high aperture angles, the light extracted by the linear and elliptical grooves produces similar irradiance and angular distributions, whereas for sources with low aperture angles, the elliptical groove focuses the extracted light and produces a higher angular distribution in comparison to this obtained with the linear groove. Our results are scalable to different light pipe dimensions and provide a systematic way to obtain preliminary designs of grooves for lighting systems that employ optical sources with different aperture angles.

Control on Temperature of Hybrid Nanofluid in Evacuated Tube Solar Collector Using Smart Curtain

This research was revealed control on temperature hybrid nanofluid in evacuated tube solar collector system, where the hybrid nanofluid utilized as working fluid in ETC for enhancement the thermal performance for heating device. The smart curtain was used for purpose shadow the evacuated tube solar collector for controlling on temperature of the hybrid nanofluid in heating or cooling conditions. In addition, Adaptive neuro fuzzy inference system (ANFIS) a way of artificial intelligence was applied to control on the shadow the evacuated solar tube collector. Where the main principle of the curtain is to control the polarization of the sun radiation, the curtain work depends on three parameters were applied in ANFIS technique, two parameters are input variable like as (temperature of hybrid nanofluids (inlet, outlet) and ambient temperature, and one output parameter represents by (distance parameter).

Optimization and thermal performance of evacuated tube solar collector with various nanofluids

Evacuated tube solar collectors (ETSC) constitute an important place among water heating systems. The use of solar energy systems will reduce CO2 and SO2 emissions for green nature. In this context, geometric and technical values of the open-ended ETSC systems were optimized by considering different parameters. In the optimization study, the solar tube collector with vacuum tube which gives the most appropriate results was discussed and its effects on heat transfer according to the presence of different work fluids were investigated. For this study, a numerical study was carried out by applying the finite volume method, one of the computational fluid dynamics methods. We confirmed our numerical study with both experimental and numerical studies. In our study, water and water-based nano-fluids are used as heat transfer fluid in 24 heat tubes with 30º inclination and the related tank that connected to it. The water-based nano-fluids we used are water as the basic fluid and MWCNT, TiO2, SiO2 and Cu as the nanoparticles. We modeled nanofluids homogeneously by handling them for different volumetric ratios. The thermal and hydrodynamic conditions of the collector were investigated using the Boussinesq Approach and the tank exit temperatures were determined. As a result of this study, it was seen that the use of nano-fluids improved the heat transfer in the ETSCs and the best thermal recovery among the nano-fluids we used in our study was realized in Cu-Water nano-fluid. Improving the thermal performance of the ETSC is important for better energy conversion. For this reason, the effects of nano-fluid usage on thermal performance in solar energy systems of pollution-free energy are promising.

Analyzing thermal properties of solar evacuated tube arrays coupled with mini-compound parabolic concentrator

Effective utilization of solar energy resource enables to improve the thermal performance of solar evacuated tube. In present work, the back side of solar vacuum tube was coupled with mini-compound parabolic concentrator (mini-CPC). The thermal characteristics of the presented mini-CPC solar vacuum tube were analyzed theoretically and experimentally. A mathematical model of heat transfer for the mini-CPC vacuum tube was established according to the energy conservation, and solved by iterative calculation based on home-built C programming language. The obtained numerical solutions fit in well with the experimental results. Furthermore, analysis indicates the vacuum interlayer plays a crucial role in hindering heat transfer. The thermal-convection resistance (Rco-air,conv) dominates the heat loss from cover tube to ambient rather than thermal-radiation resistance (Rco-sky,rad). The measured final temperature increment of working water for the mini-CPC and ordinary evacuated tube can reach 63.4 K and 49.8 K, respectively. An experimental result also reveals that the thermal efficiency of the mini-CPC vacuum tube is increased by 24.3%–29.2% compared with that of vacuum tube without mini-CPC, considering various weather conditions. Consequently, the designed mini-CPC evacuated tube shows a preferable performance, which may provide a certain reference in technology for engineering applications.

Horizontal light pipe transporter for deep plan high-rise office daylighting in tropical climate

Despite having abundance of daylight in tropical climate, many high-rise offices do not exhibit good daylight condition. Economic profits have led to the blooming of deep open-plan design which causes non-uniform daylight distribution especially in the deep area. Light pipe (LP) provides a solution to transport daylight into the interior. Daylighting performance of nine LP transporter shapes with different numbers of side and extractor openings were analysed using computer simulation software, Integrated Environment Solution Virtual Environment (IESVE) and validated with a physical scale-model experiment. Validation results showed significant Pearson correlations that ranged from 0.9170 to 0.9544. Simulations were carried out under overcast sky and intermediate sky with sun conditions. The results showed that all of the LP cases improved the daylighting performance of an empty open-plan office room. The semicircle transporter with two openings, which has 14% less surface area than a typical rectangular transporter, showed the best performance both quantitatively and qualitatively. This helps to save cost in terms of material usage and creates additional spaces for wiring and ducting in the plenum. This study also concluded that the shape of the LP transporter affects the efficiency of LP while the influence of the number of polygon sides and height of the sides, without altering the overall height of the transporter, are not significant. Thus, the findings of this study promote the usage of LP in deep open-plan high-rise office buildings by proposing design recommendations and guides for building designers.

A High-Performance 2.5 μm Charge Domain Global Shutter Pixel and Near Infrared Enhancement with Light Pipe Technology.

We developed a new 2.5 μm global shutter (GS) pixel using a 65 nm process with an advanced light pipe (LP) structure. This is the world’s smallest charge domain GS pixel reported so far. This new developed pixel platform is a key enabler for ultra-high resolution sensors, industrial cameras with wide aperture lenses, and low form factors optical modules for mobile applications. The 2.5 μm GS pixel showed excellent optical performances: 68% quantum efficiency (QE) at 530 nm, ±12.5 degrees angular response (AR), and quite low parasitic light sensitivity (PLS)—10,400 1/PLS with the F#2.8 lens. In addition, we achieved an extremely low memory node (MN) dark current 13 e−/s at 60 °C by fully pinned MN. Furthermore, we studied how the LP technology contributes to the improvement of the modulation transfer function (MTF) in near infrared (NIR) enhanced GS pixel. The 2.8 μm GS pixel using a p-substrate showed 109 lp/mm MTF@50% at 940 nm, which is 1.6 times better than that without an LP. The MTF can be more enhanced by the combination of the LP and the deep photodiode (PD) electrically isolated from the substrate. We demonstrated the advantage of using LP technology and our advanced stacked deep photodiode (SDP) technology together. This unique combination showed an improvement of more than 100% in NIR QE while maintaining an MTF that is close to the theoretical Nyquist limit (MTF @50% = 156 lp/mm).

Luminescence of YAG:Dy and YAG:Dy,Er crystals to 1700 °C

Reported here are measurements aimed at development of high temperature luminescence-based fibre optic thermometry for temperatures up to at least 1700 °C. Cylindrical crystal samples of YAG:Dy(1%) and YAG:Dy(1.5%),Er(0.5%) were fabricated by the co-precipitation method. The optical system was comprised of Nd:YAG 355 nm laser light injected into one leg of flexible bifurcated optical fibre connected to a sapphire light pipe. The input end is water cooled and the sensing end is inside a furnace in proximity to the crystal. The emission originates from the Dy3+ dopant. Decay times for the 4I15/2–6H15/2 (456 nm) transition in the YAG:Dy,Er host ranged from 856 ns at 1600 °C to 401 ns at 1700 °C. Signals taken at 10 °C intervals were clearly resolvable. Decay times appeared constant at 800 °C and below with average values of 863 µs for YAG:Dy and 734 µs for YAG:Dy,Er. Decay times from these two materials appear to converge to the same value at high temperatures. These results were achieved with laser excitation of 100 to 150 µJ. The results were compared to physical models both of which yielded reasonable empirical agreement for the limited amount of data. Thermal sensitivity determined from a multiphonon model shows that decay times change by 1% per degree at 1400 °C and 0.9% at 1700 °C. Dy emission was also detected at 405, 400 and 389 nm at 1575 °C and 1700 °C and showed the expected temperature dependence.

The Method of Hydraulic Calculation of a Heat Exchange Panel of a Solar Water-Heating Collector of a Tube–Tube Type with a Given Nonuniform Distribution of Fluid Flow Along Lifting Pipes

The purpose of this work is to develop a method for the hydraulic calculation of a heat exchange panel of a solar tube collector of a tube type with a given nonuniform distribution of fluid flow under conditions of forced circulation. On the basis of previously obtained design dependencies, a method of hydraulic calculation of a heat exchange panel of a solar thermal collector of a flat-plate type with a given uneven distribution of fluid flow under conditions of forced circulation has been developed. An example of calculation using the developed method is given.

Numerical Study of a New Solar Vacuum Tube Integrating with Phase Change Material

In this work, a new solar vacuum tube (SVT) integrating with phase change material is introduced and numerically investigated. The mathematical model and the numerical solution of phase change heat transfer is introduced. The heat transfer of the solar energy collection system during the energy storage process is simulated. Solid-liquid phase change characteristics of the SVT with paraffin inside is analyzed. Optimization analysis of fin structure parameters (fin thickness and fin spacing) in the vacuum tube is conducted. The results showed that the metal fin has a great effect on the phase change heat transfer of paraffin in SVTs. The closer the paraffin is to the fins, the more uniform the paraffin temperature is and the sooner the paraffin melts. As the fin thickness increases and the spacing between the fins decreases, the melting time of the paraffin decreases. Meanwhile, the effect of fin spacing on the overall heat transfer performance of the phase change energy storage tube is larger than the effect of the fin thickness. When the fin thickness is 2 mm, the melting time of paraffin with a fin spacing of 80 mm is 21,000 s, which is almost three times of that with a fin spacing of 10 mm (7400 s). Therefore, decreasing fin spacing is an effective way of enhancing phase change heat transfer. When the total fin volume is constant, a SVT with small fin space and small fin thickness performs better in heat transfer performance.

Enhancing the performance of a passive tubular daylighting device using a parabolic-profile collector

With the rise of renewable energy systems, there is an increased demand for improved designs of daylighting devices that work without any external energy source to illuminate the deep dark spaces of buildings. Most of the present designs deliver only low light levels especially during the early morning and late evening. This paper focuses on the performance evaluation of specifically designed parabolic-profile collector that redirects the low altitude incident rays of the sun efficiently into a mirror light pipe and thus enhances the lighting to desired levels in the building. Numerical analyses of the same were carried out for the summer solstice, winter solstice, and the autumn equinox for clear sky conditions. Experimental results for the proposed design validated the enhancement in light levels during low altitude sun and controlled lighting during the mid-day sun. The average lighting value obtained through the configured collector during low altitude sun was more than twice the lighting value achieved by a conventional daylight-collecting dome and was ∼20% higher than a prismatic collector.

Modeling of Light Pipes for the Optimal Disposition in Buildings

A light pipe is an excellent solution to transport and distribute daylight into environments without or with little lighting, guaranteeing comfort inside the rooms. As stated in the literature, the evaluation of the performances of light pipes presents numerous complexities, making the work very difficult for technicians and designers. This study is aimed to present a methodology that is able to identify the potential of light pipes using indices such as daylight autonomy (DA), continuous daylight autonomy (DAc), and useful daylight illuminance (UDI). This paper presents an analysis of daylight obtained by several configurations of simple models of light pipes installed into a 5 × 5 m plant area room. All simulations are carried out in a DAYSIM environment, which allows calculating the annual availability of daylight based on a RADIANCE raytracer backward. Several daylight conditions were analyzed for different light pipe configurations, considering different pipe lengths and a variable number of light pipes. The light pipes are tested also in the horizontal position, for different orientations. The results of all the combinations were compared with the performances of a window with dimensions equal to 1/8 of the internal surface, which was in accordance with the minimum value to be guaranteed by the Italian Regulation (D.M. 5 July 1975 n. 190) for different orientations. The results indicated a difference in daylight distribution, showing a strong correlation between the percentage levels of DA and DAc with the length and number of pipes, during different periods of the year. The simulated model is strongly influenced by the aspect ratio (R = diameter/length). The results show that the illuminance levels decrease drastically, increasing the length.

A solar fiber daylighting system without tracking component

A fixed optical fiber solar system for long distance daylighting used in buildings is proposed. Its structure and working principle have been introduced. The proposed system takes the advantages of both light pipe and traditional optical fiber system and overcomes their shortcomings. The receiving surface of the new system is like a spherical sunflower. It has a simple structure, good integrity, flexible light transmission and light redistribution characteristics. Especially, it does not require a tracking device. Both the theoretical analysis and field test have proved that the system has the same reception feature as the traditional optical fiber system with a tracking device. Its graph of the illuminance roughly follows the fluctuation of the curve of the solar irradiance. A small test system with a solar receiving area of 1.69 × 10−2 m2 and receiving angle of 32° was made to verify the feasibility of the fixed optical fiber system. Experimental result had proved that the proposed system is feasible. On average, the output illuminance inside a small test room is up to about 180 lx in a distance of 0.4 m from the bundled end of the fibers with the solar irradiance being about 600 W/m2, approximately 300 lx under approximately 800 W/m2. The simple structure, expectable low cost, almost maintenance-free and a predictable long life of the new system will facilitate the mass production and the viable commercialization of daylighting systems.

Investigation of day light levels in a room within a building

This work investigates natural light levels inside a room in Electrical & Information Engineering building, Covenant University, Ota, Ogun State, Nigeria. In order to reduce the amount of energy used on lighting, it is imperative to make the utmost use of natural daylight. The use of windows are one traditional solution, other solutions are skylights and light pipes; atria and light wells; domes and arches; structural glass which are all discussed. In high temperature regions, it is necessary to reduce the amount of sunlight entering the room because light produces heat. With the use of a Light Dependent Resistor (LDR sensor), results are presented to study the day light levels in a room by measuring the light levels at various parts of the room; by measuring the proportion of light entering through the window and measuring how the light level changes over a 24 hour period. The outcome of this work is the study and development of a system that can monitor light levels in a building. The application of this work extends to determining the period of the day when daylight is maximal in order to reduce energy cost, building an automation system for the automatic lighting of dark areas within a building as well as monitoring energy consumption used to light p a building. Further extension will be to make predictions on the natural light level based on the data available.

Photometrical analysis of mirrored light pipe: From state-of-the-art on experimental results (1990–2019) to the proposition of new experimental observations in high solar potential climates

This paper focuses on the part of Tubular Daylight Guide Systems (TDGS): the Mirrored Light-Pipe (MLP). MLP is part of the multiple specular reflection conveyors. They allow daylight to be transported and distributed in dark rooms far from traditional openings while limiting heat transmission. It involves collecting, concentrating, and diffusing sunlight using a dome placed on the roof. It is then conveyed through a highly reflective tube and diffused into a building's room using a diffuser.Previous work (Malet-Damour et al., 2017, 2016) has shown that it was necessary to identify and study the climate in which the light pipe will be installed. A state-of-the-art of experimental and numerical results was conducted over the period from1990 to 2019. It revealed that the behavior of the light pipe depends strongly on the indoor (area to be illuminated) and outdoor (meteorology) environment.This paper presents the experimental observations of studies conducted from 2013 to 2015 on Mirrored Light-Pipe in Reunion Island. The climate in which the experiment was undertaken is presented with a focus on illuminance. In 2019, this study is the only one analyzing the performance of the light pipe in extreme situations of extreme sunlight conditions (maximum global illuminance of around 200 Klux). Experimental results based on various scenarios quantified the impact of the reflection coefficient of the area to be illuminated, the presence of an anticyclonic dome, the type of sky or the ideal position of a sub-dome deflector. The results are very encouraging.

Energy saving potential of tubular light pipe system with different colors on internal surfaces

PurposeLighting in building sectors (consumes the highest energy in commercial buildings and the second highest in residential buildings in India) has very much potential for energy conservation in buildings. With the use of daylighting system, energy consumption in lighting can be lowered up to 30 to 40 per cent.Design/methodology/approachAn experimental effort has been made in this paper to explore the internal wall coloring effect on the performance of tubular light pipe. Trace-pro software has been used and validated. With the help of this software, light pipe has been designed and simulated in a ray tracing mode. Assessment of four globally used prediction models has also been conducted to compare the performances in different seasons for light pipes in the composite climate of New Delhi.FindingsIt has been conducted based on three statistical indicators as mean bias error, root mean square error and R2. Using regression, an empirical model for average internal illuminance has been developed as a function of light reflectance value (LRV) and solar altitude angle. Trace-pro results confirmed that maximum internal illuminance can be obtained with wall surfaces coated with high LRV color. Finally, by using of a single light pipe system for a test room with the artificial lighting system and applying continuous dimming control, the amount of electrical energy has been saved up to 38.5 per cent per year.Originality/valueAfter going through the literature, it has been identified that there has been no paper published which explores the effect of colors of the internal walls on the performance of the light pipe. Along with this, the comparison between existing empirical performance models and find out which model gives the best result in different seasons has been carried out for New Delhi, India.

Simulation of the parametrs of the acrylic and specular light pipe for transmitting light radiation of the LED matrix

In this article, we simulated the parametrs of an acrylic and specular light pipe to transmit radiation from the LED matrix. The results of the experiment can be estimated using the dependence of the light flux on the number of reflections in the specular light pipe. Evaluation was conducted in the software package “Mathcad”. The possibility of providing illumination from 6 to 30 lx using the system of transportation of artificial light of roads \\ streets \\ squares depends on the class of the object. The study of the transmission of light through a specular and acrylic light pipe has shown that under equal conditions of light transport (the same power, the same aperture, the equal length of the light pipe, the same diameter of the light pipe), the acrylic fiber has the advantage. Losses using acrylic light pipe of 2000 mm are 24% whereas using specular light pipe they are 45%. However, if there is no limitation in the diameter of the light pipe, then it is preferable to use a specular one. For example, at 150 mm the losses are no more than 13%, which is not achieved with an acrylic light pipe even with a diameter of 10 mm, since when the radiation aperture is kept, a reduction in diameter leads to an increase of the interaction of the radiation with the walls of the acrylic rod and increase of the optical path.

Structure Optimization of Infrared Guidance Testing Device Based on Orthogonal Test

As an important weapon, missiles cannot be ignored in its fighting capacity. Therefore, the performance testing of the missile is particularly important. The hardware in the loop simulation test using missile test equipment on the ground can reduce the cost and improve the utilization rate; it is of great significance for the development of national defence construction. In the process of missile testing, the parts under the force of deformation will reduce the accuracy of the device, therefore the light pipe support needs sufficient strength and stiffness. In this paper, the finite element method was used to analyse the structure of the optical tube support seat, and the orthogonal test was used to optimize it. The test results were analysed by the range and variance to find out the optimal level combination and the significant influence of each factor in the result. At end, the appropriate structure of the program was determined. Comparing with the original structure, the strength and rigidity of the optical tube support seat have been greatly improved. Device accuracy has also been improved.