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Abstract
Residential buildings with limited natural lighting are generally lit by fuel-based electricity which contributes to increase of CO2 concentration in the atmosphere. This paper presents the design of a hybrid fiber-optic daylighting and PV solar lighting system for household applications. The system is composed of a light collecting subsystem, a light guiding subsystem, an optical fiber light diffuser subsystem and corresponding control system. Preliminary system performance shows that, the developed system could provide comfortable and natural indoor illumination. Meanwhile, the hybrid lighting system can provide an average of 9h of electric lighting under clear sky conditions, and reduce 158.2kg of carbon dioxide emission in a year within the tested dark room of 5m².
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... Muhs et al. [33] experimentally reported that by modifying fibre mounting hardware, a 17% improvement in distribution efficiency is achieved as it improves the fibre alignment with the average angle of incident concentrated light. Some other studies that detail the mechanical parts and joints are [32,54,92,93,98]. Gorthala et al. [92] designed a single unified structure with a filter holder, filter, secondary lens holder, cable holder and cable ring successively with thread and screw arrangement, minimising the scope for the misalignment of components. ...
... Patil and Kumar [65] utilised an L bend to attach the fibre cable with the lens holder in which a hot mirror was placed with the help of a nut screw arrangement. Lv et al. [93] presented a schematic diagram of a collector fixing unit consisting of an aluminum panel on which fibre optic receiver unit was mounted using a nut and bolt arrangement. Song et al. [54] also utilised screw and thread arrangement to fix fibre cable at the focus point of the collector. ...
The lighting load can be reduced either by improving the efficiency of artificial lighting or by supplementing daylight to the building interiors with Innovative Daylighting Systems (IDS). Fibre optic daylighting system is an up-and-coming IDS that utilises direct and diffused sunlight to illuminate deep-plan buildings without location and orientation constraints. The system can benefit both building occupants and owners by attaining comfort conditions, improving productivity, saving cost and contributing to sustainable goals. This paper aims to review and summarise previous studies on fibre-optic daylighting system by categorising it into five individual subsystems: light-carrying optical fibre cable, suitable collectors, diffusers, fibre–collector interface and fibre diffuser interface. Each subsystem is reviewed and analysed based on its material property, geometrical parameters, output measurements and performance. The advantages and shortcomings of the types of optical fibre cable are explained after investigating the material characteristics and transmission efficiency parameters. Collectors used in conjunction with fibre cable are classified and analysed based on the principle, mode of study, design specification, concentration achieved and output performance. Diffusers at the fibre end used for even distribution of light have been studied to compare the sizing, spacing and output spectral characteristics. Additionally, the collector–fibre and fibre–diffuser interfaces have been reviewed. We conclude the paper by identifying the shortcomings of the system and giving some pointers towards gap in the literature that needs to be addressed to improve the system's present state and aid its widespread implementation.
... Yuexia Lv explained that same type of nine fresnel lenses used on solar collecting panel and then sunlight focused on receiving end of the optical fiber. The system was made in such a way that sunlight falls vertically on the fresnel lens which is possible by a rotating system in which stepper motor is used to rotate according to sun rotation [8]. Several investigators experimented on the hybrid fiber optic lighting system including the solar radiation collection, which collects the incident ray of sunlight [9][10][11][12][13]. ...
... So, they used one technique in which at the receiver end of fiber optic cable is aluminum sunflower cooling flippers and resonating cylinder used. The zone and size of cooling flippers is accustomed according to the cooling requirement to meet the better dissipation effects [8]. ...
... Their extensive length, small diameter, and flexibility have led to numerous applications in our daily lives. Furthermore, the optoelectronic and photonic capabilities of fibres have facilitated advancements in various industries, including telecommunications, medicine, defence, energy conversion and lighting system [5][6][7]. ...
A model is presented for calculating the electric field profiles of transverse modes in fibres. Using this model, the electric field propagation of transverse modes was calculated and compared in both bent and straight Yb and Ho fibres. Our simulations revealed that the field intensities of the modes did not consistently increase or decrease by bending as expected, but rather fluctuated as the bending radii of the fibres changed from 1 to 100 cm. Additionally, it was observed that at certain bending radii, the modes of the fibres became deformed and transitioned into higher modes. Furthermore, the extent to which the modes stretched towards cladding due to bending was calculated. To provide a more comprehensive analysis of the results and investigate the effects of the physical parameters of the fibres on the bent fibre modes, simulation results were presented for two different V numbers and core radii.
... Any tracking technology is utilised to gather solar light, which is then compressed or concentrated before being delivered to an optical fibre, light pipe, or empty space (Chen et al. 2015). Fibers are made of quartz, silica, and PMMA, according to (Lv et al. 2018) A daylighting tool for mobile devices was created by (Gorthala et al. 2017) based on Fresnel lenses; it prevents heat degradation at the input of the fibre. Thermal shielding is used in most lighting systems. ...
Daylighting plays an important role in decreasing power usage in office buildings and enhancing indoor environments. Reducing the use of energy and producing energy from renewable sources will result in lower greenhouse gas emissions. Daylighting is a method of providing light indoors through the use of windows, solar panels, optical fibers, parabolic mirrors and other forms of daylight technologies. The proposed fiber optic daylighting system will illuminate the light uniformly in interior space. Parabolic mirror and Frensnel lens are two different efficient approaches available for fiber-based day lighting system. Captured light is passed via concentrator, fiber and lenses. Uniform lighting at the capture point eliminates the heat problem when incorporating optical plastic fiber is critical in making the device cost-effective. Collimated light increases device performance helping to inject full light into the optical fibres. From simulation setup will verify that uniform intensity of light will be illuminated to different regions of buildings by the fiber optic bundle. Collimated lighting and reduction of shadows caused by mechanical parts and the convex reflector will enhances the system’s efficiency. Uniform illumination will be given at all time by using hybrid system. Using solar day lighting in homes and offices via optical fibre cables is a potential way to reduce the energy used for artificial lighting while also improving visual comfort and human health. Analysis and discussion have been conducted on the impact of optical fibre diameter on the brightness and homogeneity of light. This efficient technology can lower energy costs and also helps in climate change challenges.
... Disciplinary knowledge within architecture and various engineering fields such as mechanical engineering, electrical engineering, architectural engineering, civil engineering, and building science provide a strong foundation for HBI research. Research on building processes and practices over the last decade has led to innovations in design methods [53][54][55] , engineering systems such as HVAC equipment and appliances 56,57 , lighting 58,59 , building materials like glazing systems 60,61 , construction processes 62,63 , and building management and controls 64,65 . In HBI, it is important to move beyond these building-centric foci to leverage sensed awareness of the needs and behaviors of their occupants so that user experiences and outcomes are optimized against often-competing external variables such as energy availability, extreme events (e.g., wildfires and public health concerns), weather events, schedules, or the needs of other users. ...
Human-Building Interaction (HBI) is a convergent field that represents the growing complexities of the dynamic interplay between human experience and intelligence within built environments. This paper provides core definitions, research dimensions, and an overall vision for the future of HBI as developed through consensus among 25 interdisciplinary experts in a series of facilitated workshops. Three primary areas contribute to and require attention in HBI research: humans (human experiences, performance, and well-being), buildings (building design and operations), and technologies (sensing, inference, and awareness). Three critical interdisciplinary research domains intersect these areas: control systems and decision making, trust and collaboration, and modeling and simulation. Finally, at the core, it is vital for HBI research to center on and support equity, privacy, and sustainability. Compelling research questions are posed for each primary area, research domain, and core principle. State-of-the-art methods used in HBI studies are discussed, and examples of original research are offered to illustrate opportunities for the advancement of HBI research.
... Each of these eight channels can be opened or closed independently of the others and is capable of driving a charge to 40 V with a current of 500 mA. The main limitation resides in the total dissipation power of the circuit and which is around 0.7 W for a temperature of 85 °C [32]- [34]. ...
The vast majority of embedded system designs start with a processor-based system, using a microcontroller or microprocessor as the core element to predict and process the basic control tasks. This paper aims to increase the reliability of controlling a stepper motor by an embedded circuit, which generates four digital signals of pulse width modulation (PWM). The manager of this circuit is an embedded processor licensed from Microblaze, which sits within the FPGA architecture Virtex 5. This processor analyzes the parameters to execute the rotation under the best conditions (energy consumption, speed, precision, reliability). The communication with the PC takes place via the RS232 link to provide feedback. The autonomous processor generates an independent control frequency of the PC. The four digital signals of PWM are simulated on Xilinx's ISim interface and sent to the ULN2803 amplifier circuit to run the stepper motor.
... This is due to the continuous change in the contact interaction area under the influence of temperature. A slight influence of 2 h on the qualitative and quantitative patterns of changes in the contact zone parameters was observed when the secondary PC thickness was more than 50% of h . The secondary PC material perceived force loading to a lesser extent. ...
The article discusses the effects of thermal-force on the Panda-type optical fiber. The studies used a wide temperature range. The research used two thermal cycles with exposures to temperatures of 23, 60 and -60 °C. The field of residual stresses in the fiber formed during the drawing process was determined and applied. Panda was considered taking into account a two-layer viscoelastic polymer coating under conditions of tension winding on an aluminum coil in the framework of a contact problem. The paper investigated three variants of coil radius to analyze the effect of bending on fiber behavior. The effect of the coating thickness ratio on the system deformation and optical characteristics was analyzed. Qualitative and quantitative patterns of the effect of temperature, bending, thickness of individual polymer coating layers and relaxation transitions of their materials on the Panda optical fiber deformation and optical characteristics were established. Assessment of approaches to the calculation of optical characteristics (values of the refractive indices and fiber birefringence) are given in the framework of the study. The patterns of deformation and optical behavior of the Panda-type fiber with a protective coating, taking into account the nonlinear behavior of the system materials, were original results.
... Though electricity is not required and there are no hassles of maintenance, this system will be techno economically viable in India if installation cost comes down. Some fibre optic based hybrid daylight capturing systems can provide about 9 hrs of light in the entire day in clear sky conditions which can about 158 kg of carbon emissions per year [40,41]. However, the limitation of this kind of system includes the time of operation and control. ...
As people living in remote areas still lack access to indoor lighting, the intervention of appropriate need-based innovations to improve basic indoor lighting facilities are essential. The present work discusses the development of a hybrid lighting device, Micro Solar Dome, that utilizes both the active and passive forms of solar energy to ensure sustainable lighting facilities for rural houses. The work elaborates the design, simulation, and pilot-scale installation of the device in 8 states in India. Based on the performance, a Principal Component Analysis was done, which indicated that more than 93% variation of the performance of the device was due to Global Horizontal Irradiance and Relative Humidity. A novel predictive model utilizing the Random Forest algorithm was developed for major Köppen climatic zones in India to determine the night-time performance of the device and validate the Principal Component Analysis results. As per the prediction, the average operation time of the device is about 3.5hrs at night, with the highest of 4.6 hrs in the Hot Desert Climate and the lowest of 2.4 hrs in the Humid Subtropical climate when 9 Köppen Zones are considered covering more than 95% of the geographic area of the country.
... Preliminary analysis proved to provide a stable illumination in the interior spaces, also the hybrid lighting system could provide with an average 9 hours of continuous electricity generation. When tested in room area of 5 m 2 it considerably reduced the release of 158.2 kg of CO 2 around the year [23]. Georgios E. Arnaoutakis et al. (2013) in this study it was shown that Optical fibers have an added advantage of being included in the solar concentrator systems by transporting the light into distant places with same illumination level and direct conversion of solar energy into light. ...
Over the years there has been an increase in the energy consumption pattern which has given rise to various environmental issues. Around 20% of the energy is used for lighting purpose and conferring to a U.S. Energy Information Administration 2007 & International Energy Agencies 2006 report lighting amounts for 7% of the CO 2 emissions globally and releases around 1900 metric tons of carbon dioxide (CO 2) into the atmosphere. Due to this issue an environment friendly solution which utilizes renewable form of energy so that even actions like lighting the buildings could be sustainable. About 50-80% of energy consumption for lighting can be saved through designing an efficient daylighting system to light the interior spaces in the buildings, which would provide various physiological and psychological benefits for the wellbeing of human beings. In this study a daylighting system is designed on the Cassegrain principle and evaluated through software's and experimental setup. A model of the daylighting system is constructed using simple and low cost materials, easily available and reliable. Maximum solar radiation point was ascertained by studying sun path diagrams. The model was tested for its lux intensity and temperature on 5 sunny days over a period of 6 hours. The daylighting system provides a lux intensity of above 1400 at its peak hour and 323 lux at its minimum through a bundle of 209 individual optical fibers enclosed in a circular pipe of 3/4 inch in diameter. The temperature attained was 60 ºC and 50 ºC which were well within the operating temperature limits of the optical fiber.
... The Dual-axis tracking has an optical efficiency of 0.813%, with a year average value of 14.3% and 40.9% times better than the east-west and north-south monitoring modes, respectively. Lv et al. [13] Proposed dual fiber-optic daylighting and photovoltaic lighting systems for residential use. The system consisted of a light transmission subsystem, a light controlling subsystem, an optical fiber light diffuser subsystem, and the associated control device set up the system. ...
A hybrid solar lighting/ thermal system utilized a parabolic solar dish as a solar collector illustrated in this paper. A two-axis tracking system was developed and employed to improve the energy output of a concentrating solar system (CSP) that produces hot water and light. During the daytime, sunlight is transmitted by fiber optics to an indoor photovoltaic PV device to generate electricity, or it can be used directly as daylighting. The heat generated is used to heat water. The findings show that the proposed system is a low-cost, high-performance approach for solar energy use in building energy efficiency, and readily available tracking components and tools. The experimental work shows that the maximum efficiency of the hybrid solar lighting/ thermal system controlled with a dual-axis solar tracking system was 32.2%.
... Such daylight systems have gained popularity because of their deep reach into the dark buildings and the fact that they can be deployed in existing building structures (Mayhoub, 2014). Such systems have also been found suitable for military expeditionary shelters (Lv et al, 2018). Since most of the daylight-harvesting systems actively track sun, sunlight can be made available to indoors spaces, for longer durations. ...
We demonstrate a prototype for a compact, hybrid daylight harvesting system that collects and transports sunlight to illuminate dark spaces, up to two levels underground. The prototype is designed to have a compact size so that it can be mounted on top of a conventional lamp post at ground level and the system serves an additional purpose of a streetlamp for ground level illumination during nighttime. The system utilizes an acrylic ball lens as solar concentrator, and the focused sunlight is directly coupled into a single plastic optical fiber that transports it to indoor spaces. The spherical symmetry of the ball lens allows it to be static, while the position of focused light spot varies gradually underneath it, in accordance with the solar position in the sky. Therefore, only the light-collecting optical fiber needs to be moved under the ball lens, obviating the need for heavy-duty motors typically used to align solar concentrators along the direction of sun’s rays. The focused sunlight under the ball is tracked using a microcontroller-based tracking mechanism. This design is the first demonstration of a daylight harvesting system, to the best of our knowledge, using a ball lens as static sunlight collector and a movable optical fiber tracking the focused spot underneath the ball. The moving parts in the proposed system are lightweight and are well concealed from environmental hazards like dust, wind and moisture.
... With a small change in the point of concentration of the Fresnel lens due to tracking errors, a huge flux effect can be observed. Also, almost all the researchers reported in the literature adopted a small size of the Fresnel lens for the daylighting system [14][15][16][17][18][19]. To illuminate a big area, it is necessary to integrate a giant Fresnel lens concentrator or many medium size lenses. ...
A strategy for precise solar tracking has been developed using feedback signals from seven photo sensors in conjunction with the operation of an active daylighting system. The tracking system was composed of a microcontroller, two stepper motors, photo sensors, a grooves-in Fresnel lens concentrator, and a glass optical fiber cable. A robust control was implemented using Cadmium Sulfide (CdS) sensors to track the sun's path precisely from sunrise to sunset. To avoid the cloud effect, two separate sensors were installed apart from the main tracking sensors. The control system was allowed to track the sun's position if clouds covered the sky continuously for less than approximately 70 minutes. To analyze the performance of the solar tracker for daylighting applications, a series of experiments were performed in different weather conditions where the accuracy and effectiveness of the present solar tracking control were confirmed.
... After concentration or compression, the sunlight is transmitted through the optical fiber, light pipe or free space [105]. The technology transmitted through the optical fiber is also called Fiber Daylighting System [32,[38][39][40][41][42][43][44][47][48][49][50]52,[101][102][103][104][106][107][108]. However, the main materials of the optical fiber used in the fiber daylighting system are: SiO 2 , PMMA and quartz. ...
Daylighting systems make daylight illuminance possible, and the development of prototype daylighting systems can provide more efficient daylight illuminance. The purpose of this article is to review the development and performance of prototype daylighting systems in the last decade. The passive and active daylighting systems are listed separately and divided into the four categories by the presence and absence of hybrid. Each prototype daylighting system was evaluated in terms of cost and daylight performance and as well as their novel optical design. We evaluated the architecture and daylighting principles of each system by reviewing individual prototype daylighting systems. The cost of prototype systems still poses a challenge to development. How to use passive or active systems in different environments and whether or not electrical lighting assistance is needed is a controversial issue. However, active daylighting systems equipped with solar tracking systems are still mainstream. This research is a valuable resource for daylight researchers and newcomers. It is helpful to understand the advantages of various prototype daylighting systems and commercial daylighting systems that have been developed for many years; moreover, it is also possible to know the research directions suggested by the prototype daylighting systems. These will be of further use in developing innovative and better daylighting systems and designs.
As a result, the industry is actively working to reduce its energy footprint and promote a more sustainable approach to agricultural lighting. This study presents a solar lighting system designed for indoor farming to provide natural light. The proposed system uses a parabolic dish concentrator integrating with polymethyl methacrylate optical fibers to direct concentrated light into a desired place. A water cooling mechanism is also used to prevent heat transmission to the optical fibers. The indoor sunlight's distribution is studied using a designed darkroom. The evaluation is carried out in 7 days, from November 23 to 29, from 8 a.m. to 4 p.m., to ensure the stability of the system under various weather conditions. The results of the experiments show that the receiver's temperature can remain at 63 °C on sunny days under a clear sky, even when the maximum value of solar radiation is about 982 W m⁻² with the highest air temperature of 19 °C. During the experiments, the solar illuminance ranges from a maximum of 118,821.85 lx to a minimum value of 374.9.6 lx. The overall optical efficiency of the system, considering optical components, ranges from 31% to 32% under various outdoor illuminance levels. Overall, it is confirmed that the developed solar lighting system offers a applicable method to naturally illuminate protected agricultural environments, enhancing the quality of the growing crops.
This article analyzes and compares three daylighting technologies: light pipes, optical fibers, and heliostats. This work aims to evaluate their efficiency, sustainability, and cost-effectiveness in providing natural light to indoor spaces. The analysis includes a review of the principles behind each technology, the design and development of the prototypes and experiments carried out by our research team, their advantages and disadvantages, and their applications in different settings. The comparison is based on several criteria, such as installation, cost, efficiency, output spectrum, and hybrid system. The results indicate that each technology has its unique features and is suited to specific applications. Light pipes are effective for short distances, and they can be easily integrated into existing buildings. Optical fibers are suitable for long distances and offer flexibility in design, but they require more maintenance. Heliostats are ideal for large spaces, but they are expensive to install and operate. Overall, this study provides valuable insight into the strengths and weaknesses of three daylighting technologies and helps designers and architects make informed decisions when selecting the most appropriate solution for future work.
This research examines household energy technologies adopted in the past decade in the state of New South Wales, Australia. The examination addresses regional differences that need to be considered in the promotion of clean, renewable energy. The study analyses a longitudinal dataset (2011-2019) of Building-Sustainability-Index-certificated dwelling units in metropolitan (n = 167,883) and rural (n = 100,675) areas. The sampled units have adopted a variety of technologies for heating water; heating, cooling and lighting homes; and cooking food. The results show a significant difference between the two examined regions in terms of adoption rate, with the p-values of the Chi-squared tests all below 0.001. This difference can be attributed to the complex socioeconomic , lifestyle and living conditions of the two different regions. Based on the Bass model (with p-values < 0.05), most technologies will reach saturation, whereas a few will continue to grow, such as the combination of ceiling fans and air conditioning for bedroom cooling in rural areas. This study makes suggestions for policies to promote clean, renewable energy among households on the basis of regionality.
After being adequately captured and concentrated, solar radiation can be conducted by optical fiber bundles/cables and directly used for illumination (lighting) or heating of confined spaces, or indirectly used by converting it in other forms of energy (e.g., for producing electricity). This article reports preliminary tests conducted on a 7-m-long optical fiber bundle/cable with an effective aperture circular area of 14 mm in diameter, specially designed and manufactured by a leading company to transmit up to 1000 Wth of unfiltered concentrated sunlight. The cable was tested in the typical receiver position at the top of a solar concentration central tower. The main purpose was the experimental determination of the transmission efficiency of the cable in function of the incidence angle using selected groups of heliostats belonging to the heliostat field. The testing methodology proved to be capable of evaluating the performance of the cable. The cable withstood the tests without revealing any type of damage. The results obtained showed that the transmissivity of the cable is higher than 50% when the incidence angle of the solar radiation is lower than 14.7°, increasing sharply to circa 95% when the incidence angle is lower than 4.5°.
Because a traditional optical fiber light guiding system includes a tracking device, it also inevitably has a complex structure, high construction and maintenance costs, short life span and low reliability. Although several types have been developed for decades, there are no successful products on the market. The biggest cause of the problem is that all traditional optical fiber light guiding systems must have a tracking device. This paper studies a solar fiber optic guide system without a tracking device, hoping to solve this problem. A fixed fiber light guide system using concave outlet concentrators as its receiving unit is proposed. The structure and working principle of the concave outlet concentrator, the receiving unit and the light guide system are introduced. With optical simulation software and the actual sunlight experimental method, this paper first discusses the conceptual design of the concentrator, then studies the transmission efficiency curve of the receiving unit with different angles of incident light, and finally tests the output illuminance of the whole system in actual sunlight. Field test results show that when the average sunshine intensity is about 800 W/m2, the system has an output of nearly 300 lux at 0.4 m in front of the outlet end of the fiber bundle with only receiving area. This illumination has been able to meet people’s daily lighting requirements. The results of computer simulation and actual sunlight experiments show that this fixed optical fiber light guide system with non-tracing structure is feasible. The absence of a tracking structure means that all moving parts of the system are completely discarded. This greatly improves the working reliability and operation life of the light guide system, and greatly reduces the maintenance and operating costs.
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.
Due to energy saving and flexible installation, the daylighting system via optical fibers for indoor illumination has attracted a lot of research attention. However, in applications, it is hard to adopt large aperture lens to improve sunlight collection due to the overheating problem caused by high sunlight concentration. The optical fibers generally adopted, Polymethylmethacrylate (PMMA) fiber, often suffers from overheating, and cannot work under a temperature exceeding 70 °C (Ashby, 2005). To solve this problem, this study tested three measures, infrared light filter (Sedki and Maaroufi, 2017), flux homogenization and fiber facet polishing, respectively to control thermal load caused by a large lens with a diameter of 1 m. The experimental data shows that the infrared light filter can reflect infrared light (740–1100 nm) efficiently, meanwhile keeping highly transparent for the visible spectrum (400–700 nm), which produces the cold incident light. A homogenizer was also designed to produce a uniform flux distribution by reflection in a mirror cavity. Analysis based on Monte Carlo rays-tracing method (MCRT) showed that the homogenizer could supply a flat flux distribution of 1500 suns by eliminating the flux peak. Microscopy experiments revealed that fine polish could effectively remove dust off the surface of the PMMA fiber, so to avoid heat spot to protect PMMA fiber. A long time daylighting test on Beijing (40°05′23″N, 116°17′45″E, 97 klux outdoor) demonstrated the feasibility of the large lens with an aperture of 1 m for daylighting via optical fibers, which offered an illumination level of 180 lx on an area of 36 m ² . A comparison test on Lhasa, Tibet (29°39′52″N, 91°06′26″E) has also carried out under a higher outdoor illuminance of 125 klux, which showed a daylighting efficiency of 15.1%. The research showed that, as long as there was good thermal load control, PMMA optical fibers can work well and it is feasible to adopt large lens into daylighting system via plastic optical fibers.
Fiber-optic solar hybrid lighting for mobile application such as military shelters in remote areas is appealing since high initial costs of such systems appear to be justified. This paper addresses the aspect of two-stage optics for a fiber-optic solar lighting system for the mobile application. More specifically, the focus of this paper is on the design and development of a second stage or secondary concentrator. Two-stage optics offers a distinct advantage of higher sun angle tolerance and hence a low-accuracy tracker can be used for the mobile application. The objective of this study was to design and develop a secondary concentrator that yielded a minimized peak illuminance on the fiber-optic inlet and achieved uniformity, to avoid localized heat damage to the fiber inlet. In addition, the overall goal was to increase the lumen output from the two-stage optics. Specifications for the design of the two-stage concentrator were: (1) the primary stage concentrator was a 10-in. diameter Fresnel lens; (2) solar tolerance angle or the half-angle of acceptance was ±1.75°; (3) the fiber half-acceptance angle was ±40°; and (4) the fiber optic cable diameter was 0.5-in. Raytracing was used to determine the optimum geometry for the secondary lens. Among various geometries simulated included a conical secondary, a Compound Parabolic Concentrator (CPC), and a combination of conical and Compound Elliptical Concentrator (CEC). The analysis showed that a combination design comprising conical/CEC geometry was better than the conical and CPC geometries in terms of greatest overall light output and most reduced peak illuminance on the fiber optic cable. Prototype secondary lenses based on the design were fabricated from acrylic and optical silicones. Testing of the prototype lenses revealed that acrylic secondary performed better than the silicone lenses in terms of the measured lumen output. Testing also showed that the fiber-optic cable temperature was within the maximum operating temperature of acrylic and didn't suffer any high temperature damage during the five month long outdoor testing.
This study was carried out in four districts of Assam to assess the technical functionality of the solar home lighting systems (SHLS), service delivery model, institutional mechanism, maintenance and monitoring, user's awareness and its impacts on rural livelihood. The study found that only 28.9% of the systems are functional, 62.3% are found working with minor faults and 8.8% are either non-functional or having major faults. The average working duration per day for winter, summer and monsoon seasons are 2.2 h, 3.5 h and 2.3 h respectively. The study observes noticeable benefits due to adoption of SHLS such as reduction in kerosene consumption, increase in children's study hours, extended working hours of small businesses and income generation through mobile phone charging. One of the key reasons for unsatisfactory technical performance of SHLS is because of poor service delivery model and inefficiency in existing institutional structure such as passive village energy committee and non-availability of service centres or local technicians for post-installation maintenance. The study observes that user perceptions on the system are positive. However, cost considerations seem to be the main obstacle for system adoption. This study concludes that availability of local technicians, effective village energy committees, demand driven system design and appropriate social awareness towards livelihood improvement options will improve the sustainability and economic viability of the SHLS.
Active daylighting schemes utilize sunlight more aggressively, promoting flexibility in the application of sunlight for indoor illumination. The daylighting system based on fiber-optic solar concentrator technologies is one of such systems that constantly track the sun to capture its beam radiation for indoor illumination. This paper introduces the applicability and functional effectiveness of a daylighting system which consists of dish concentrator(s), a dual-axis solar tracker and light guides including optical fiber cables. Simulation models were developed using a number of different software where Photopia provided the relevant photometric data (candela power distribution curves, CDCs) by producing a virtual luminaire of the daylighting system. To assess the validity of different models, a series of tests for the system's application to a test chamber were carried out. The effective combination of sunlight and conventional electric lighting is also explored with the application of a dimming control. (C) 2013 Published by Elsevier Ltd.
Unavailability of grid based electricity is a major challenge facing a majority of developing countries, particularly the population in rural areas. Consequently, people are forced to use the kerosene lantern in much of the world for lighting. However, fuel-based lighting is contributing to global warming and causing serious health related problems. To address these issues, several developing countries are now encouraging the use of sustainable clean lighting systems – solar-powered light emitting diode system. In the present paper, barriers and mechanisms to boost the use of solar-powered lighting are discussed.