Flat Fresnel Lens Research Articles

Daylight performance of collector-diffuser combinations in light pipe systems at different geographical locations

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.

Graphene-based ultralow-profile microwave Fresnel lens

The development of ultrathin Fresnel lenses has revolutionized the lens technology and provided great prospects for the miniaturization of electromagnetic systems. Despite considerable advances in microtechnology, a scalable fabrication strategy to achieve ultralow profile microwave lenses is yet to be developed. Here, we report on a novel strategy to create ultrathin and essentially flat Fresnel lenses using graphene rings. We show that monolayer or multilayer graphene can be microstructured into a Fresnel lens to utilize the unique transmission properties of graphene. We design different Fresnel lenses and investigate their performance in the microwave regime both numerically and experimentally. It is shown that one can change the intensity of the focused wave without shifting the focusing point by altering the number of the graphene layers. The good agreement between our experimental results and the results of numerical simulations demonstrates the feasibility of atom-thick (about 10−7 of the operating wavelength) graphene-based lenses and shows their potential for ultra-compact integration.

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

A novel three-dimensional elliptical-shaped Fresnel lens (ESFL) analytical model is presented to evaluate and maximize the solar energy concentration of Fresnel-lens-based solar concentrators. AutoCAD, Zemax and Ansys software were used for the ESFL design, performance evaluation and temperature calculation, respectively. Contrary to the previous modeling processes, based on the edge-ray principle with an acceptance half-angle of ±0.27° as the key defining parameter, the present model uses, instead, a Gaussian distribution to define the solar source in Zemax. The results were validated through the numerical analysis of published experimental data from a flat Fresnel lens. An in-depth study of the influence of several ESFL factors, such as focal length, arch height and aspect ratio, on its output performance is carried out. Moreover, the evaluation of the ESFL output performance as a function of the number/size of the grooves is also analyzed. Compared to the typical 1–16 grooves per millimeter reported in the previous literature, this mathematical parametric modeling allowed a substantial reduction in grooves/mm to 0.3–0.4, which may enable an easy mass production of ESFL. The concentrated solar distribution of the optimal ESFL configuration was then compared to that of the best flat Fresnel lens configuration, under the same focusing conditions. Due to the elliptical shape of the lens, the chromatic aberration effect was largely reduced, resulting in higher concentrated solar flux and temperature. Over 2360 K and 1360 K maximum temperatures were found for ESFL and flat Fresnel lenses, respectively, demonstrating the great potential of the three-dimensional curved-shaped Fresnel lens on renewable solar energy applications that require high concentrations of solar fluxes and temperatures.

Structure of microprismatic Fresnel lenses for creating uniform focal images.

Flat Fresnel lenses are known to form a point image in the focal plane. However, several practical applications require transforming lens to concentrate a parallel light beam into a uniformly illuminated light circle. We previously proposed a novel algorithm for simulating such a transforming Fresnel concentrator. In this study, we applied this method to the diamond-cutting technique to create prismatic refractive surfaces of high optical quality. To reduce the discreteness of formed images, each refractive lens zone was fabricated from several small identical microprisms in the simulation. The new fabricated circular light beam concentrators were investigated by computer modelling and experimentally with a collimated laser beam.

Solar Desalination Using Fresnel Lens as Concentrated Solar Power Device: An Experimental Study in Tropical Climate

Solar desalination is a renewable energy-driven method that produces freshwater from saline/brackish water. Conventional solar desalination units are equipped with an inclined transparent condensing plate placed over a feedwater basin containing saline water. The process is limited to a small quantity of production because of scattered solar irradiation and the unavailability of solar heat due to intermittent cloudy weather. In this study, a Fresnel lens has been used to concentrate solar energy onto a spot to increase the local temperature of feedwater and the evaporation rate. Flat Fresnel lenses on a double sloped passive solar still were used, where the focal points were adjusted to fall directly on the feedwater. The experiments were conducted for two different geometries and alongside the comparison between the conventional and the modified solar still; the number of Fresnel lenses was also varied. Saline solution with a concentration of 20,000 ppm was used as the feedwater. The research is aimed to be implemented for producing freshwater in the natural weather conditions of Malaysia. It was found that using two Fresnel lenses instead of a single large one gives a boost to the production of freshwater per unit solar irradiation by 39%. The produced water has a TDS value of 37 ppm, which is well within the drinking water standard range according to the World Health Organization.

Improving the energy efficiency of a solar power plant

The urgency of the work is due to the feasibility of increasing the energy efficiency of solar power plants through the use of solar energy concentrators. Ways to improve the energy efficiency of solar panels using a sys-tem of directional mirrors, flat Fresnel lenses, spherical concentrators and trackers have been investigated. It is established that the most optimal way to improve the energy efficiency of solar panels is to use inexpensive track-ers with a simple design. The analysis of known types of solar panels, which differ in materials from which their elements are made, and the coefficients of efficiency – dependence of energy produced by a photocell on the intensity of solar radiation per unit of its surface has been carried out, and the type of solar panels by the criterion “price-quality” has been selected. A tracker design has been developed to track the angle of inclination of solar panels to increase efficiency. The electricity generated by the proposed solar power plant was calculated using an online calculator. It is projected to reduce losses when generating electricity for a given power plant due to the use of a tracker compared to a fixed power system, with the same number of solar panels. In order to reduce the cost of the tracker, it is suggested to orientate it to the south at once, and to change the inclination angles twice a year (in early April and late August). The energy efficiency of the power plant is calculated in two stages. At the first stage the amount of electricity from solar panels per year when adjusting only the angle of inclination of the panels to the south is calculated. At the second stage energy efficiency of the power plant is calculated taking into account the increase of energy efficiency of the solar power plant when using the tracker system. The calculated electricity generation of the proposed solar power plant with tracker confirmed the efficiency and feasibility of using the designed tracker system. The application of the designed tracker system allows to increase the energy efficiency of solar panels by an average of 25%.

FOCAL SPOT STRUCTURE OF FRESNEL LENS AND ITS HOMOGENIZATION

Using statistical Monte-Carlo photon-tracing method, we numerically studied focal spot structure of flat Fresnel lens. It has been shown that due to dispersion effect, focal spot structure changes considerably. In addition, we demonstrated homogenization of strongly focused photons. Rectangular prism can be applied to achieve the homogenization.

Application-based design of the Fresnel lens solar concentrator

A novel genetically themed hierarchical algorithm (GTHA) has been investigated to design Fresnel lens solar concentrators that match with the distinct energy input and spatial geometry of various thermal applications. Basic heat transfer analysis of each application decides its solar energy requirement. The GTHA incorporated in MATLAB® optimizes the concentrator characteristics to secure this energy demand, balancing a minimized geometry and a maximized efficiency. The optimum concentrator is then simulated to ensure the algorithm validity. To verify the algorithmic-optimization and simulation-validation processes, two experimental applications were selected from the literature, a solar welding system for H13 steel plates and a solar Stirling engine with an aluminum-cavity receiver attached to the heater section. In each case, a flat Fresnel lens with a spot focus was algorithmically designed to supply the desired solar heat, and then a computer simulation of the optimized lens was conducted showing great comparability to the original experimental results.

Performance Analysis of a Solar Desalination System with Concentrated Solar Power (CSP)

Malaysia, being located around the tropical belt, enjoys ample solar exposure throughout the year. Harnessing solar energy for different application is making progress nationwide. Besides extending research on photovoltaic cells; the solar water heating for different purposes is progressing through the past decades. In this paper, performance of a solar still associated with concentrated solar power facilities is presented. In a typical solar still, the solar heat is used to evaporate waste/brackish/saline water (generally termed as feedwater). A basin of the feedwater covered by an inclined transparent cover is placed under the sun to trap the solar heat. The solar heat evaporates the feedwater and the condensate is collected from the inner surface of the transparent cover. In this study, the incident solar irradiation is optimized to produce freshwater from saline/brackish water in a portable solar collector with concentrated solar power (CSP). Fresnel lens has been used as the CSP apparatus. A flat Fresnel lens of size 400 mm x 300 mm with a focal length of 510 mm and light intensity of 92% was attached to concentrate the incident solar irradiation on the inclined transparent cover. Preliminary experiments showed that addition of the Fresnel lens with an optimum tilt of 45° created a “hotspot” in the basin in a particular time of the day and the average condensate production rate increased by 92% compared to that from a bare transparent cover. The distillate from the solar still had a conductivity of 39 μS (25 ppm) which is well below the range of drinking water standard (500 ppm) of the World Health Organization. This study has been conducted in Kajang, Malaysia during the month of August 2018 with an average daytime temperature of 32°C.

Enhanced Shadow Retargeting with Light-Source Estimation Using Flat Fresnel Lenses

Shadow-retargeting maps depict the appearance of real shadows to virtual shadows given corresponding deformation of scene geometry, such that appearance is seamlessly maintained. By performing virtual shadow reconstruction from unoccluded real-shadow samples observed in the camera frame, this method efficiently recovers deformed shadow appearance. In this manuscript, we introduce a light-estimation approach that enables light-source detection using flat Fresnel lenses that allow this method to work without a set of pre-established conditions. We extend the adeptness of this approach by handling scenarios with multiple receiver surfaces and a non-grounded occluder with high accuracy. Results are presented on a range of objects, deformations, and illumination conditions in real-time Augmented Reality (AR) on a mobile device. We demonstrate the practical application of the method in generating otherwise laborious in-betweening frames for 3D printed stop-motion animation.

Optimizing the Fresnel-Lens Solar-Concentrator Design for Tracking Error Mitigation in Thermal Applications, Using a Statistical Algorithm

The driving motive of this work is to enhance the tolerability of a flat Fresnel-lens concentrator to tracking errors, without the use of secondary optics or sophisticated, and normally costly, meticulous tracking equipment. This is achieved by optimizing the prismatic geometry of the Fresnel lens through a statistical approach that incorporates laws of light refraction and trigonometry. The proposed design produces high focal heat flux that is more suitable for thermal applications. A comparative simulation analysis was conducted for two case studies from literature, each with a different design method for the Fresnel lens. On basis of equivalent geometric concentration ratio and f-number, the flat-spot lenses, designed by this study, returned higher values of the concentration acceptance product ( $$CAP$$ ). In case #1 of a 212× cylindrical lens with an f-number of unity, an equivalent flat lens by this work almost doubled the $$CAP$$ from 0.165 to 0.34. For the design case #2 of a 559× aspheric Fresnel lens made by simple geometrical optics, a 60.7% enhanced $$CAP$$ was achieved by this work’s lens, from 0.206 to 0.331, at an f-number of 0.83.

A fresnel concentrator with fiber-optic bundle based space solar power satellite design

A Fresnel concentrator with fiber-optic bundle based space solar power satellite (SSPS) is proposed as an innovative design in this paper. It consists of a flat Fresnel lens array for solar concentration, fiber bundles to transport the condensed sunlight to the photovoltaic panel and a highly modular sandwich module for power generation/transmission. Operating principle, structure configuration and efficiency of the system are presented in detail. Also, Fresnel concentrator with a secondary homogenizer is designed to obtain high concentration ratio and good irradiance uniformity on the solar cell. Lastly, to maintain the temperature fluctuation within a design requirement, the thermal analysis of the sandwich module is investigated. The obtained results demonstrate the feasibility of the proposed SSPS design.

Design and preliminary experiments of truncated ball lens as secondary optical element for CPV system

The Concentrated Photovoltaic (CPV) technology based on the use of high-efficiency multi-junction solar cells has higher power generation efficiency than other photovoltaic power generating technology. However, the cost and reliability of CPV technology are the primary reasons that restrict its progress. A truncated ball lens as a secondary optical element for CPV optical system is proposed in this paper to reduce the cost and improve the reliability. Theoretical analysis and experimental investigations were conducted on a concentrator with geometrical concentration ratio of 625×, a flat Fresnel lens as primary optical element and a truncated ball lens as secondary optical element. Test results show that the concentrator with power generation efficiency of 30.1% and acceptance angle of 0.73° can be obtained. Additionally, temperature effects of SOG lens on power generation are also studied.

Focal zone characteristics of stepped Fresnel and axicon acoustic lenses

Flat Fresnel and axicon acoustic lenses were developed and characterized both numerically and experimentally. Flat lenses have a compact profile leading to less attenuation and phase distortion in the bulk lens material. Fresnel lenses approximate spherical focusing to a fixed point whereas the axicon focuses to a narrow focal line, producing a tighter lateral beam over a longer depth. Numerical models of the sound pressure field from both types of lenses were done using the angular spectrum method. The lenses were 3d printed with polylactic acid (PLA) and also lathe cut with transparent polystyrene. Pulse-echo measurements of the sound speed were done for both materials. Pressure field scans were conducted using a 1.2 MHz planar transducer in a hydrophone scanning tank. These scans demonstrate the focusing effect of both types of lenses and are in agreement with the numerical model.

A Novel Technique to Design Flat Fresnel Lens with Uniform Irradiance Distribution

In this paper, we propose a novel technique to design flat Fresnel lens to achieve big concentration ratio, high uniform irradiance distribution while keeping F-number small using both refraction and total internal reflection (TIR) phenomena. Also, this method can be used to design concentrated photovoltaic (CPV) system without secondary optics lens (SOE). In this technique, Fresnel lens is constructed by many prisms, which are built by ideal Cartesian oval. The design process of Fresnel lens was performed using Matlab program. Ray tracing technique has been used to optimize the structure of lens using LightToolsTM software. The simulation results have been shown that Fresnel lens has a good optical property such asconcentration ratio is 2500x, F-number =0.4, and high uniform irradiance distribution.

Design of the Secondary Optical Elements for Concentrated Photovoltaic Units with Fresnel Lenses

The goal of this presented study was to determine the optimum parameters of secondary optical elements (SOEs) for concentrated photovoltaic (CPV) units with flat Fresnel lenses. Three types of SOEs are under consideration in the design process, including kaleidoscope with equal optical path design (KOD), kaleidoscope with flat top surface (KFTS), and open-truncated tetrahedral pyramid with specular walls (SP). The function of using a SOE with a Fresnel lens in a CPV unit is to achieve high optical efficiency, low sensitivity to the sun tracking error, and improved uniformity of irradiance distribution on the solar cell. Ray tracing technique was developed to simulate the optical characteristics of the CPV unit with various design parameters of each type of SOE. Finally, an optimum KOD-type SOE was determined by parametric design process. The resulting optical performance of the CPV unit with the optimum SOE was evaluated in both single-wavelength and broadband simulation of solar spectrum.

Design and study of Fresnel lens for an antenna in indoor visible light communication system

Indoor visible light communication is a novel wireless communication based on white LED technology. For its application needs, equal-pitch flat Fresnel lens is designed. Compared with traditional lens, Fresnel lens has several advantages including strong focus ability, short focal length, thin thickness, light weight, low cost, etc. The optical concentration ratio, the optical efficiency and the spot size of these Fresnel lenses are analyzed respectively with different parameters by means of Trace pro. Furthermore, the concentration performance is discussed at different incident angles. The results indicate that this kind of Fresnel lens could be used as an antenna of high-gain and small field, and the optical efficiency could be obtained to be 92.1%.

Conceptual design and assessment of a profiled Fresnel lens daylight collector

This paper describes design of daylight collectors using multiple Fresnel lenses, each facing the sun for a particular period of time in a day. The influence of solar movement on flat Fresnel lens was studied. The influence of groove density of the lens was also determined by which the suitable Fresnel lens was selected. Passive and profiled north-facing and south-facing collectors with multi-lens system have been designed based on the solar altitude and azimuth angle of a geographical location. Performance of the north- and south-facing collector at different times of a day with an acrylic dome indicated better efficiency and uniformity of lighting throughout the day time for the proposed profiled Fresnel collectors.

Integrated opto-mechanical analysis of a PMMA Fresnel lens for a concentrated photovoltaic system

This study presents the integrated opto-mechanical analysis of a polymethylmethacrylate (PMMA) Fresnel lens used in solar concentrators for concentrated photovoltaic systems. A solid model of a flat Fresnel lens made of PMMA was constructed based on the design parameters and derived formula of a Fresnel lens. Ray-tracing simulations were used to investigate the two main influences of temperature variation on the Fresnel lens: variations in the refractive index and thermal distortion. The temperature dependence of the refractive index of the PMMA lens was analyzed based on the temperature coefficient of the refractive index (dn/dT). The thermal distortion of the Fresnel lens at various temperature increases was calculated using finite element analysis. The temperature-induced effects, refractive index variation, and deformed lens geometry were then simultaneously imported into a ray-tracing simulation. Thus, this study investigates and discusses the thermal–optical effects of a flat Fresnel lens on its optical performance, including the spot size, the maximum irradiance on the receiver, and the optical efficiency at different temperature increases.

Simulation of Thermal-Optical Effects on a PMMA Fresnel Lens Used in Solar Concentrators

This study presents an integrated opto-mechanical analysis of a PMMA Fresnel lens used in solar concentrators for concentrated photovoltaic systems. The temperature dependence of refractive index of the PMMA lens was analyzed based on its temperature coefficient of refractive index dn/dT. In addition, the thermal distortion of the Fresnel lens under various temperature rises was computed by finite element analysis (FEA). Then, the temperature induced effects, variation of refractive index and the deformed lens geometry, were imported into ray tracing simulation simultaneously. Finally, the thermal-optical effects on the optical performance of a flat Fresnel lens were successfully investigated and discussed, including the maximum irradiances on the receiver and the optical efficiencies under different temperature rises.