Large Fresnel Lens Research Articles

大口径菲涅尔透镜制造关键技术研究与应用

大口径菲涅尔透镜制造关键技术研究与应用

Efficient sunlight harvesting with combined system of large Fresnel lens segmented mirror reflectors and compound parabolic concentrator without tracking sun for indoor daylight illumination

Sunlight is a great substitute for indoor artificial lighting during the daytime but still isn't so viable because of the cost of fiber-based daylighting system and its efficiency. In this paper, we report the design and development of a cost-effective non-mechanical tracking-based solar concentration system using a combination of a large Fresnel lens, segmented mirrors, and segmented compound parabolic concentrator (SCPC) for indoor daylighting application. This system presents the three-stage collection of sunlight by means of extending the collection aperture vertically while keeping the horizontal area same. First one is the concentrated light from the Fresnel lens, the second one is the direct sunlight incident onto the CPC and the third one is the direct sunlight reflected from the segmented mirrors onto the CPC. Hence the light transported through this system is adequate for illumination purposes inside the room. The manufacturing of ideal CPCs through the moulding process is both expensive and complex, and it necessitates extreme precision. Therefore, a cost-effective and efficient segmented CPC is designed and developed using a highly reflecting mirror-polished aluminum sheet which works well compared to the ideal CPC. To transport concentrated sunlight inside the room a highly reflecting horizontal light pipe is designed and developed. The collimated light at the output is challenging therefore, we have coupled inverted CPC at the exit of segmented CPC in the system. Further, to guide sunlight deep into the rooms we have coupled the entire system with a rectangular light pipe. An efficient diffuser is coupled at the end of the rectangular light pipe to illuminate the room uniformly. Various optical parameters such as illuminance, color rendering index (CRI), and correlated color temperature (CCT) values are analyzed from the result obtained which shows that the system can efficiently transport sunlight deep inside the room throughout the day. Therefore, the proposed system is very much helpful for the sustainable development of a country.

Dual Fresnel lens and segmented mirrors based efficient solar concentration system without tracking sun for solar thermal energy generation

We propose and experimentally demonstrate a combination of two large Fresnel lenses and six segmented mirrors for concentrating sunlight efficiently within a common area throughout the day without mechanical tracking the sun. The proposed system was used for efficient solar thermal power generation, i.e., efficient heating of water. The angular position of two lenses is designed and mounted in such a way that the lenses are in direct line-of-sight with the sun for efficient sunlight collection during early morning, mid-day and for evening hours. Further, the height gap between Fresnel lenses and receiver unit is sufficient enough such that there is no shadow effect on the receiver unit hence the receiver unit is also exposed to direct sunlight rays throughout the day. Due to concentration of sunlight throughout the day the efficiency of solar thermal system is significantly enhanced. This is due to the fact that with the help of the proposed system, apart from concentrated sunlight made incident on to the solar thermal receiver it is also exposed to direct sunlight. The thermal receiver unit is placed in the common area and fluid is heated very fast. The design of system using ray optics in ZEMAX and experimental study of the direct and collected incident sunlight radiations using the proposed concentrating system on the receiver unit is analyzed. The thermal performance of the proposed system is compared with combination of single large Fresnel lens and segmented mirrors. The instantaneous thermal efficiency of the proposed system is around 20% or more in comparison to single lens concentrating system. The result shows that this type of system is highly efficient, and very much useful for countries where sunlight is available in plenty. Therefore, the proposed system is very much helpful for sustainable development of country.

Experimental study of combined transparent solar panel and large Fresnel lens concentrator based hybrid PV/thermal sunlight harvesting system

Solar energy is immensely available during daytime on the earth. It is a sustainable, renewable and green energy. Improvement in efficiency of harnessing solar energy is the utmost concern of the present research due to its renewable nature. This article presents a complete utilization of solar irradiation over the broad spectrum of solar energy efficiently. The design, development and implementation of the hybrid solar photo voltaic & thermal (SPVT) system are reported, in which a tandem structure of transparent solar panel and large Fresnel lens concentrator are mounted for sunlight harvesting. In this hybrid system a semi-transparent solar panel mounted on the top for PV application and large Fresnel lens is for concentrating the transmitted light onto a solar thermal absorber unit for heating water efficiently. The partial visible portion of solar energy is converted into voltage generation using semi transparent solar panel (TSP) while remaining transmitted radiations is further concentrated by a large Fresnel lens which was fixed below semi-transparent solar panel. Concentrated sunlight was focused on solar thermal unit which was utilized for water heating. Two different color filter semi-transparent solar panel modules were integrated with the system for testing and reported that the red color filter solar panel generates more power and overall efficiency as compared to other one. Experimental results using the prototype developed system are reported. Due to simultaneous electricity generation and domestic hot water application the hybrid system becomes more efficient, robust and cost effective for sustainable development of the country.

Autostereoscopic display for multiviewers positioned at different distances using time-multiplexed layered directional backlight.

In this paper, an autostereoscopic display system based on a time-multiplexed directional backlight using a large aperture Fresnel lens is proposed. High-resolution stereoscopy for multiple viewers positioned at different distances from the screen is achieved in the proposed system by layering polymer dispersed liquid crystal screens behind the Fresnel lens. The screens with segmented electrodes are electrically controlled to change the position of light diffusion, while the time-multiplexed backlight is projected by a digital mirror device projector at a high refresh rate. The light is diffused at the conjugate focal points of the observers' eyes to deliver directional light to each eye. The right-eye image and the left-eye image are alternated on the LCD panel in front of the lens to synchronize with the backlight.

P‐72: An Autostereoscopic Display with a Deep Viewing Zone Using Time‐Multiplexed Directional Backlight

We propose a high‐resolution autostereoscopic display that has a deep viewing zone based on time‐multiplexed directional backlight using a large aperture Fresnel lens. When the distance of a viewer from the display changes, the depth of light source should be changed to avoid stereoscopic crosstalk. By combining a DMD projector with layered PDLC screens, the depth of the light source is electronically changed to follow the viewer's motion, which expands the viewing zone in the depth direction.

Indoor daylighting using Fresnel lens solar-concentrator-based hybrid cylindrical luminaire for illumination and water heating

Abundant availability of sunlight during daytime and the broad spectrum of solar energy has attracted much attention from researchers. The photometric parameters of sunlight such as color coordinates, color rendering index, and color temperature are most appropriate for human vision as compared to artificial light sources. This is due to the fact that visible portion of sunlight is almost uniform and matches perfectly with the human eye sensitivity curve. Further, it is well known that sunlight also has great health benefits. To exploit these advantages, we have developed a solar concentrator system based on a large Fresnel lens and a light guide to transport sunlight indoors. The infrared portion of solar energy is utilized for water heating, and the visible portion of sunlight is transmitted via a plastic optical fiber (POF) bundle which guides sunlight into the rooms. One end of the POF is coupled with a light guide, and another end is coupled with a cylindrical rod-shaped luminaire made up of acrylic. POFs are low cost, flexible, and easily available compared to glass fibers, and therefore are generally used for transporting sunlight indoors. However, the spectral profile of transmitted sunlight does not remain uniform in the visible portion while propagating via long POF. To achieve optimum spectral profile, a blue LED is ingrooved into the cylindrical luminaire. The design of the system, experimental details, thermal efficiency, and photometric parameters such as color coordinates, illuminance, optical efficiency, and spectrum of indoor lighting are reported. The proposed hybrid system will reduce the requirement of electricity consumption during the daytime, improve indoor illumination quality, and be useful for sustainable development.

Performance of the EUSO-Balloon optics

EUSO-Balloon is the first balloon pathfinder of the JEM-EUSO (Joint Experiment Missions - Extreme Universe Space Observatory) framework. It is an ultraviolet (UV) telescope designed to test the key technologies and methods necessary for the indirect detection of Ultra High Energy Cosmic Rays (UHECR) by observing from above the fluorescence emission produced by Extensive Air Showers (EAS) in the 290-430 nm band. The instrument was launched on the 24$^{t}^{h}$ of August, 2014 by the French space agency (CNES) from the stratospheric balloon base in Timmins, Canada and performed an 8 hour night time flight. One of the key technologies of EUSO-Balloon is the refractive optical system which consists of two large aspherical Fresnel lenses (≈ 1 m$^{2}$) and aims at focusing the UV light into a detector plane formed by an array of Multi-Anode Photomultiplying tubes. This work presents a description of the optical system, the test bench and methods used to characterize its performance and the global efficiency. The measured performance can be understood through the addition of a semi-empirical diffusion model to the classic ray-tracing model of the optics.

Boosting CO2 photoreduction activity by large Fresnel lens concentrated solar light

CO2 photoreduction to hydrocarbons is an important process for solar energy. Herein, the reaction rate is massively pushed up by large Fresnel lens (diameter = 1 m) concentrating solar light technology. The maximum CH4 yield rate reached 3157.2 μmol·g−1·h−1, C2H4 rate to 511.6 μmol·g−1·h−1, C2H6 to 1346.0 μmol·g−1·h−1, and the CO2 conversion reached 3.94%. The total solar to chemical energy conversion efficiency got 0.15%. The results are considered from the intensification of reaction conditions such as light intensity, reaction temperature, and pressure of H2O and CO2. The findings will be beneficial for the further discussion of CO2 photoreduction basing upon the existed catalysts system, and decrease the research threshold in CO2 photoreduction.

Realization of high flux daylighting via optical fibers using large Fresnel lens

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 m2. 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.

Solar concentrator based multipurpose sunlight harvesting system without tracking

Sunlight is being utilized to reduce energy crisis and it is a popular and reliable source of energy because of its pollution free nature. It is abundantly available on the Earth but difficult to achieve maximum efficiency during daytime without tracking. We have designed and developed a non-tracking solar concentrator system based on a combination of large Fresnel lens and segmented mirrors. Six segmented mirrors are mounted at different angles so that the concentrated light due to the Fresnel lens is redirected into a particular area throughout the day to achieve maximum concentration without tracking the sun. The entire system is mounted in a single mechanical mount with no moving parts. The concentrated sunlight was utilized for multipurpose solar applications. We have demonstrated simultaneous solar water heating and electricity generation by means of a thermoelectric generator (TEG) module using the developed system. The maximum temperature of water recorded at the outlet from the water heating system is 88°C and efficiency at this temperature is 0.47. The preliminary results of power generated from one TEG module is 40 mW. Experimental results of water heating throughout the day and electricity generation using TEG is reported. This type of system is unique, robust, and low cost for sunlight harvesting.

An optical fiber daylighting system with large Fresnel lens

Because of flexible installation and natural spectrum, the concentrated sunlight transmission systems via PMMA (Polymethyl methacrylate) fibers for indoor illumination are concerned widely in areas of building energy saving. Due to the long-term indoor work, the daily working population in cities lacks of natural light and is susceptible to various diseases. Therefore, from the health point of view, it is necessary to develop deep indoor daylighting. In this work, a sunlight concentration and transmission system was developed and tested, which uses a Fresnel lens with a diameter of 1m to achieve large flux collection. A reflection design of light path was adopted to resolve the problem of long focal length of the Fresnel lens. A hot mirror and a homogenizer were used to protect the optic fiber bundle from burned by high temperature. The results showed that the daylighting efficiency is about 11%-13%. The operability of the equipment was verified through experiments, proving that the equipment can be combined with buildings for daylighting. It is hoped that this research will be of some reference value to the design of optical fiber daylighting systems in buildings.

Experimental evaluation of a large aperture Fresnel lens system for the plastic optical fiber coupling with solar-concentrated light

Experimental evaluation of a large aperture Fresnel lens system for the plastic optical fiber coupling with solar-concentrated light

Design and experimental study on Fresnel lens of the combination of equal-width and equal-height of grooves

High concentrating PV systems rely on large Fresnel lens that must be precisely oriented in the direction of the Sun to maintain high concentration ratio. We propose a new Fresnel lens design method combining equal-width and equal-height of grooves in this paper based on the principle of focused spot maximum energy. In the ring band near the center of Fresnel lens, the design with equal-width grooves is applied, and when the given condition is reached, the design with equal-height grooves is introduced near the edges of the Fresnel lens, which ensures all the lens grooves are planar. In this paper, we establish a Fresnel lens design example model by Solidworks, and simulate it with the software ZEMAX. An experimental test platform is built to test, and the simulation correctness is proved by experiments. Experimental result shows the concentrating efficiency of this example is 69.3%, slightly lower than the simulation result 75.1%.

Stray light reduction in optical computed tomography using a convergent cone-beam source

The planar diffuser light source for a cone-beam optical CT scanner was replaced with a filtered LED and large Fresnel lens. The source was focused on a camera and convergent cone-beam images were acquired. Images are sensitive to mismatches in the refractive index of vessels, samples and matching liquid. For PETE jars and water solutions, a loss of approximately 30% of the projections was demonstrated. Teflon PFA cylinders provided better refractive index matching and more accurate reconstructions. The convergent cone-beam source dramatically increased imaging efficiency by a factor of 1000 and reduced stray light levels by confining illumination to image forming rays.

Radiochromic film thickness correction with convergent cone- beam optical CT scanner

A cone-beam optical computed tomography (CT) scanner was modified by replacing the diffuse planar yellow light emitting diode (LED) source with violet and red LEDs and a large Fresnel lens. The narrow band sources provided transmission images of radiochromic EBT2 film at 420 and 633 nm, with air as a reference. The dose image was not detectable with the violet source. This demonstrated spectral independence of the two images. Assuming attenuation at 420 nm was dominated by absorption from yellow dye in the active film layer allowed a relative thickness image to be calculated. By scaling the 633 nm optical density image for relative thickness, non-uniformities in the recorded dose distribution due to film thickness variations, were removed.

Technique for Outdoor Test on Concentrating Photovoltaic Cells

Outdoor experimentation of solar cells is essential to maximize their performance and to assess utilization requirements and limits. More generally tests with direct exposure to the sun are useful to understand the behavior of components and new materials for solar applications in real working conditions. Insolation and ambient factors are uncontrollable but can be monitored to know the environmental situation of the solar exposure experiment. A parallel characterization of the photocells can be performed in laboratory under controllable and reproducible conditions. A methodology to execute solar exposure tests is proposed and practically applied on photovoltaic cells for a solar cogeneration system. The cells are measured with concentrated solar light obtained utilizing a large Fresnel lens mounted on a sun tracker. Outdoor measurements monitor the effects of the exposure of two multijunction photovoltaic cells to focused sunlight. The main result is the continuous acquisition of theV-I(voltage-current) curve for the cells in different conditions of solar concentration and temperature of exercise to assess their behavior. The research investigates electrical power extracted, efficiency, temperatures reached, and possible damages of the photovoltaic cell.

Machining Mechanism of Fresnel Lens Mold

This paper analyzed the large diameter Fresnel lens mold machining mechanism based on modal test methods .The design and mold machining principle of Fresnel lens were introduced . Explored the cutting speed and feed on chip formation process. The results show that: the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing, an improvement of material strength with the increase of strain rate and the evolution process of the chip can be divided into: ribbon cuttings, serrated chips, cell chips.

Using large aperture projection optics to monitor characteristic parameters of far field speckle

In order to systematically evaluate the characteristic parameters of far field speckle in the real atmosphere condition and analyze the influence of laser atmospheric propagation on the optoelectronic system, a monitoring method is presented using large aperture projection optics. The projection optics is made of low cost and large aperture Fresnel lens, which can project the irradiance distribution of far field speckle on the CCD detector. The receiving power and scintillation index on a certain aperture can be evaluated through CCD imaging process. The beam wander and beam radius can also be evaluated under the condition that the receiving aperture is large enough and the speckle would not leave the Fresnel lens because of the beam wander effect. The error of CCD pixel response non-uniformity and its influence and the calibration of CCD irradiance response function and image geometric projection coefficient are discussed. The experiments show that this system is feasible for the monitoring of far field speckle characteristic parameters in the laser atmospheric propagation. Especially for the free space optical communication, it can prove experiment data support on the slow fading research of median level and optimal design of detection threshold under the complex influence of atmospheric extinction and various kinds of turbulence effects.

Research on Chip Formation Mechanism in Mold Processing of Large Diameter Fresnel Lens

This paper describes the analysis of the chip formation mechanism in mold machining process of large diameter Fresnel lens based on the ABAQUS finite element simulation software and modal test methods. Combined with the material constitutive relation and material failure criteria etc, a two-dimensional orthogonal cutting model was established and the chip derived from the simulation was compared with the chip from modal test, with a consequent verification of the feasibility of simulation chip model. The simulation contributes to an investigation into the effects of the cutting speed on chip formation process. The results show that: the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing, and material strength will improve with the increase of strain rate, the evolution process of the chip of material plastic reduction can be divided into: ribbon cuttings, serrated chips, cell chips.