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NaYF 4 : Eu nanorods with high aspect ratios are elaborated and optically trapped using dual fiber optical tweezers in a counterpropagating geometry. High trapping efficiency is observed using converging beams, emitted from diffractive Fresnel lenses directly 3D printed onto cleaved fiber facets. Stable nanorod trapping and alignment are reported for a fiber-to-fiber distance of 200 μm and light powers down to 10 mW. Trapping of nanorod clusters containing one to three nanorods and the coupling of nanorod motion in both axial and transverse directions are considered and discussed. The europium emission is studied by polarization-resolved spectroscopy with particular emphasis on the magnetic and electric dipole transitions. The respective σ and π orientations of the different emission lines are determined. The angles with respect to the nanorod axes of the corresponding magnetic and electric dipoles are calculated. Mono-exponential emission decay with decay time of 4–5 ms is reported. It is shown that the nanorod orientation can be determined by purely spectroscopic means.

Concentrated photovoltaic system provides higher efficiency at the expense of complexity and cost. A direct comparison in performance is made between concentrated and non-concentrated PV units. It is observed that a concentrated system outperforms, not for all, but only for a range of insolation. The range depends majorly on the relative difference between the conversion efficiencies of the PV materials. In-house experiments are performed to evaluate the performance metrics. A GaAs based concentrating PV module is characterized showing nominal efficiency and temperature coefficient to be 24.0% and −0.045%/°C, respectively. A Fresnel lens based tracked concentrator system is designed, fabricated and characterized under different DNI, ambient temperatures and operating cell temperatures (maintained by constant temperature coolant flow). An opto-thermal model, validated against the aforementioned experiments, is employed to make systematic comparison under different insolations. As for example, a CPV system (with CR = 90) with 40%-efficient cells outperforms an NCPV system with 25%-efficient cells only above DNI ∼630 W/m2. Exact value of the critical DNI depends on other operating conditions and effective conversion efficiencies. Here, the presumption of better performance of CPV system under all conditions is proven incorrect and a general methodology is provided for such an important design decision.

To effectively eliminate optical end loss for small-scale linear solar concentrators, a fixed linear-focus Fresnel lens solar system (FLFS) with triangle cavity receiver is described and the principle is provided. The effects of the receiver parameters including receiver position f, solar declination angle δ , solar hour angle ω , internal surface absorptivity α a b and end plane reflectivity ρ r on the end loss ratio ( μ o e l ) and relative optical efficiency ( η r e − o p t ) of the proposed system have been studied by the control variable method and Monte Carlo ray tracing (MCRT) method which is implemented by software TracePro®. Significance tests of critical factors are conducted to assess the effect of receiver parameters. These results revealed that the FLFS could effectively solve the problem of optical end loss of linear solar concentrators. When f = 650 mm and δ = 0°, 8°, 16°, and 23°27 ′ , the corresponding average η r e − o p t at ω from 0° to 60° are 0.9459, 0.9422, 0.9145, and 0.8144, respectively. As δ increases, reducing f can ensure the system operates at a high-efficiency state. The η r e − o p t shows a positive relationship with α a b and no relationship with ρ r . δ occupies the greatest significant influence on η r e − o p t , which is followed by ω , α a b and f.

Fresnel lenses are important compact optical components, which are comprised of multiple faceted concentric rings. These lenses are the most widely utilized diffractive optical element in the industry and has been extensively applied in various optical systems due to their distinct advantages. These include the reduction in the lens thickness, smaller occupied volume and less material required compared to their conventional spherical and aspherical counterparts. In general, the processes to manufacture Fresnel lenses can be categorized into two distinct groups: subtractive fabrication and precision forming. Precision forming processes, like molding and embossing, are usually used in mass production to replicate the optical features and profiles usually employ the use of lens molds generated by subtractive fabrication processes. Thus, the process of molding Fresnel lenses are not substantially different from that of conventional molding processes for other optical components, still relying on the accuracies of the molds utilized. Unfortunately, there is a lack of a comprehensive study to summarize and evaluate the recent advances of UPM techniques to generate these optical Fresnel lens structures. Fresnel lenses and molds differ from each other in terms of lens design, work material and tool/workpiece geometries, and such variations will then drive the development of different machining and characterization methods in terms of tool setting, tool wear, tool path generation as well as lens measurement. This paper summarizes the existing fabrication techniques to generate these lens structures, excluding molding. In addition, a discussion and analysis of the strengths and future areas of research interest of the reviewed techniques are conducted. This review is believed to be helpful and educational for the progress and further development of machining of ultra-precision Fresnel lens structures for advanced optical applications.

In this paper, the performance of a silicon cell with a Fresnel lens (FL) for building a solar photovoltaic concentrator system was evaluated; the solar concentrator is a Fresnel lens, which is a point concentrator made of polymethyl-methacrylate (PMMA) as a thin lens for the optics system. As the radiation from the sun on the solar cell is concentrated to the levels of solar radiation of 750, 1300, 1930, 2600, 4250, 7250, and 10500) W/m2, the work was conducted at the midday in summer weather conditions, with ambient temperatures ranging 40-45 °C. The evaluation was performed in three cases; each case was conducted in succession. The performance of the cell was evaluated first without a cooling system, and then it was evaluated using the heat-sink (phenolic (pcb) printed circuit boards type). Finally, the fan with the heat-sink was used as a cooling system, which was more effective in dissipating the heat generated in the solar cell. The evaluation, based on the current and voltage (I-V) results with cell temperature, showed the following efficiency values for the abovementioned three cases, respectively:(6.91 ,7.76 ,6.65 ,7.77 ,6.27 ,4.74 ,3.37 ) %, (7.41 , 9.21 , 7.5 , 8.31 , 9.71 ,7.53 ,4.72 ) %, and (7.63 ,9.34 , 7.57, 8.37 , 10.2 ,7.75, 4.7) %.

Cataracts and age-related macular degeneration (AMD) are the leading causes of blindness worldwide. The main symptoms of AMD are: a gradual decrease in visual acuity to the hundredth, metamorphosis, the appearance of a central scotoma, which reduces the quality of life of the patients and leads to disability. Prosthetic and stationary means of optical rehabilitation, such as magnifiers for the visually impaired, glasses, video systems are cumbersome and poorly functional. An alternative correction option is intraocular vision devices that improve the patient’s quality of life. The review considers various types of intraocular implants, in particular, the intraocular telescope system (intraocular miniature telescope-IMT, IOL-VIP, IOL-AMD), Fresnel lens, Lipschitz lens, Scharioth macular lens (Scharioth macula lens, SML), EyeMax Mono, LENTIS ® MAX IOL LS-313 MF80. The use of high-tech devices for the correction of visual disturbances in AMD has opened a new direction in the rehabilitation of low vision. Further study and implementation of the latest generation of “macular” lenses will improve the quality of life of patients with advanced stages of AMD.

This article investigates the discrepancy between the theoretical and the experimental optical characterisation results of a Fresnel Lens - silicon on glass (SOG), as a primary optical component toward UHCPV of >3000 suns design ( Shanks et al., 2018 ). All the equations were elaborated for single- and multi-junction solar cells, emphasising the performance when the focal spot area is larger or lesser than the solar cell area. This simple prediction approach of optical characterisation has shown a strong agreement between the theoretical and experimental results of the multi-junction solar cell with a discrepancy of 2% at 7.7 W (77 suns) and 6% on the average cross a solar irradiance on the cell from 3.1 W to 7.7 W corresponding to 31 suns – 77 suns in concentration ratio. A theoretical analysis of the optical performance for a 1/4 of the system grouping three optical interfaces is performed to estimate the optical loss and its influence on the optical efficiency and optical concentration ratio.

Solar radiation can be considered as one of the most suitable energy source to be used for cooking food. It is therefore important to promote advancement in solar cooking systems, in particular as concerns their efficiency and cooking times. In this work, we designed, realized and tested a novel low-cost solar cooker that uses a high-performance light-concentrating Fresnel lens, which is able to concentrate onto a small focal area a large amount of solar radiation. The radiation is then reflected by a mirror towards a cooking surface, where a pot can be located. The cooker has a geometrical concentration ratio of 40.97. In order to characterize the thermal performance of the cooker, we carried out several outdoor tests with a dedicated test setup, using water and silicone oil as absorbing media. Respect to other solar cookers, results show that the proposed cooker is able to reach high temperatures with good efficiency and reduced heating times: 3 kg of water can reach 90 °C in around 30 min, while 3 kg of silicone oil can be taken from 40 to 170 °C in less than one hour.

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.

In roll-to-roll (R2R) manufacturing of optical films, machining the microstructure on the roller mold is a crucial step. However, a trimmed radial Fresnel lens structure is discontinuous, and direct diamond cutting the trimmed radial Fresnel lens structure array on the surface of a roller mold was considered infeasible. Hence, a new machining method, diamond micro-scraping (DMS), combined with the polygonal Fresnel lens structure array characteristics, provides a possible solution for machining the Fresnel lens structure array on the roller molds. Tool path planning and simulation analysis were based on the layout of the polygonal Fresnel structure array. In this paper, a polygonal Fresnel lens structure array is processed directly on the periphery roller surface with a diamond tool. The machining performance of DMS was evaluated by studying the influence of different materials and machining parameters on the machined surface quality. The proposed method guides the design and precision manufacturing of the Fresnel lens structure array on precision rollers.

The maximum concentration ratio of the commercial parabolic trough collectors is limited to 42% of the theoretical limit of concentration. Recently, the secondary flat reflector geometry has been p...

Optical metasurfaces have been extensively investigated, demonstrating diverse and multiple functionalities with complete control over the transmitted and reflected fields. Most optical metasurfaces are however static, with only a few configurations offering (rather limited) electrical control, thereby jeopardizing their application prospects in emerging flat optics technologies. Here, we suggest an approach to realize electrically tunable optical metasurfaces, demonstrating dynamic Fresnel lens focusing. The active Fresnel lens (AFL) exploits the electro-optic Pockels effect in a 300-nm-thick lithium niobate layer sandwiched between a continuous thick and nanostructured gold film serving as electrodes. We fabricate and characterize the AFL, focusing 800-900 nm radiation at the distance of 40 $\mathrm{\mu}$m with the focusing efficiency of 15 % and demonstrating the modulation depth of 1.5 % with the driving voltage of $\pm 10$ V within the bandwidth of $\sim\! 4$ MHz. We believe that the electro-optic metasurface concept introduced is useful for designing dynamic flat optics components., Comment: 9 pages, 4 figures

Focusing Fresnel lenses are used in many fields of applied optics. These devices are used in optical sensor systems for imaging and optoelectronic integration. The traditional Fresnel lens concentrates the light intensity on the center of the formed image. We present a microprismatic Fresnel lens that transforms a circular incident parallel light beam into a homogeneous light circle with the necessary diameter at a certain distance from the lens. These transforming Fresnel concentrators can be successfully used, for example, in monitoring devices to automatically adjust the output signal from four-quadrant photodetectors. Traditional focusing Fresnel structures are manufactured by photolithographic methods or adjustable direct laser recording with photoresists. These methods enable the formation of stepped optical structures, which have inherent surface defects, resulting in the formation of images that are not high in quality. The proposed specialized Fresnel concentrators can be easily fabricated via the diamond cutting method, which enables the manufacturing of flat working surfaces with exceedingly high optical quality. We also develop a method for simulating the Fresnel transforming lenses with flat conical working facets and calculate the geometric parameters of the circular concentrators. We then apply the simulation results to the diamond cutting method and fabricate the microprismatic light transforming lens samples. These samples are then investigated experimentally with a collimated laser beam. The obtained data agree with the theoretical predictions.

A bubbling humidification-dehumidification (HDH) desalination system directly heated by concentrated sunlight is presented in this work. Sending directly the concentrated sunlight into bubbling humidification chamber can save the circulation pipeline and solar receivers, and reduce the heat loss of the pipeline which simplifies the device's structure and adds its operation reliability. The HDH system consists of a Fresnel lens solar concentrator, a bubbling humidification chamber and a bubbling dehumidification chamber. The operating principle and the structural design of the bubbling chambers are explained. A cylindrical Fresnel lens is used to focus sunlight into the humidification chamber to directly heat the seawater. With air coming out from the perforated wall of the immerged pipe, bubbles will generate underwater to obtain sufficient heat and moisture transfer. Experimental tests under different conditions were carried out to verify the design and study the performance characteristics. The results that the maximum freshwater productivity is about 1.24L/h/m2 when the maximum solar irradiance is 980 W/m2. The accumulated yield can reach 5.61L/d/m2 with an average thermal efficiency about 69% for sunny weather conditions in October in Beijing. Besides, the average thermal efficiency is about 71% under steady-state condition. Compared to some published works, the proposed bubbling HDH desalination system has relatively higher freshwater productivity owing to its effective heat and moisture transfer enhancement by direct solar heating and bubbling. The economic analysis showed that the price of the produced water for the system is about 0.027$/L.

Crossed electrode arrays address some of the challenges associated with 3-D ultrasound imaging because of the significant reduction in the number of elements ( $2{N}$ versus ${N}^{{2}}$ ). However, creating a two-way focused 3-D image in real time is difficult with these arrays because azimuth and elevation dimensions cannot be beamformed at the same time. This work describes a new 3-D imaging technique that uses the flexibility of bias-sensitive substrates to create a high-quality elevation focus on a crossed electrode array. The principle behind this technique is to perform conventional compound imaging with an azimuth set of electrodes while implementing a bias controllable elevation lens with an elevation set of electrodes. On transmit, the biases are chosen to mimic a Fresnel lens. Then, on receive, the Hadamard coding is implemented along the elevation dimension. After decoding, we gain the RF data for each element across the elevation aperture even though there is effectively only one channel in that dimension. A 30-MHz, 128-element crossed electrode relaxor array was fabricated on a 1–3 electrostrictive composite substrate and was used to demonstrate the performance of the imaging technique. The on-axis −6-dB beamwidths were simulated to be 175 and $150~\mu \text{m}$ in the azimuth and elevation directions, respectively, and the focus remained isotropic in the furthest elevation slice. Images were generated of a wire phantom to confirm the performance of the azimuth and elevational radiation patterns with good agreement between simulation and experiment. High-resolution 3-D volumetric images were generated of an ex vivo rat brain. Images of the cerebellum showed that the white and gray matter tracts could clearly be visualized with isometric resolution in both the azimuth and elevation dimensions.

We propose a new thin and flat virtual reality (VR) display design using a Fresnel lenslet array, a Fresnel lens, and a polarization-based optical folding technique. The proposed optical system has a wide field of view (FOV) of 102°x102°, a wide eye-box of 8.8 mm, and an ergonomic eye-relief of 20 mm. Simultaneously, only 3.3 mm of physical distance is required between the display panel and the lens, so that the integrated VR display can have a compact form factor like sunglasses. Moreover, since all lenslet of the lenslet array is designed to operate under on-axis condition with low aberration, the discontinuous pupil swim distortion between the lenslets is hardly observed. In addition, all on-axis lenslets can be designed identically, reducing production cost, and even off-the-shelf Fresnel optics can be used. In this paper, we introduce how we design system parameters and analyze system performance. Finally, we demonstrate two prototypes and experimentally verify that the proposed VR display system has the expected performance while having a glasses-like form factor.

The solar energy is increasingly used as a renewable energy source. Raising the efficiency of energy conversion from solar to useful energy (electric and thermal) represents an important research direction in the renewable energy domain. Using hybrid systems for electric and thermal energy cogeneration can be a solution. In this study, a hybrid system (HS) is designed, manufactured, implemented, and experimentally tested under concentrated sunlight with a concentration ratio of 25 suns, obtained using a Fresnel lens as a sunlight concentrator. The HS comprises of four concentrated photovoltaic cells (CPVs), four thermoelectric generators (TEGs), and a solar thermal collector (STC). The HS is studied in three configurations of the exposed surface: only the CPV active area, the CPV active area with ceramic support, and the CPV active area with ceramic support covered with graphite sheet. Results reveal that the efficiency of each system component is affected by the exposed surface. If the efficiencies of the CPVs decrease from 32.3% to 30.8% from the first configuration to the last one, the efficiencies of TEGs and STC increase from 0.12% to 0.44 and from 26.3% to 52.0%, respectively. Increasing the concentration ratio from 25 to 33 suns, the power of the CPVs increases with almost 31%, but the efficiency decreases slightly, instead the efficiencies of the TEGs and STC increase.

Tissue engineering has played a very significant role in the medical field with an ever-growing demand for various tissue donations. One crucial factor is the fabrication of a desirable artificial three-dimensional (3D) tissue scaffold to act as the extracellular matrix (ECM), meeting the complex requirements for specific cell cultures. Existing scaffold fabrication techniques and systems used in constructing extracellular matrix are two-dimensionally limiting, expensive, and time-consuming. For instance, some simple fabrication methods cannot control fabricated structures with morphologies accurately, while others may introduce harmful organic solvents into scaffolds during the fabrication processes. To achieve an optimal scaffold for tissue engineering, we developed a novel 3D printing system capable of printing tissue scaffold structures with improved efficiency. The uniqueness of our system is the transparent diffractive optical elements (DOEs) of linear binary Fresnel lens fabricated to control the luminous intensity distribution. These DOEs of different patterns are arranged in series on a coverslip with each optical element designed to diffact and focus incident light at a particular plane within the device. Coupled with other optical components of the system, 3D woodpile scaffolds were printed in an effective and efficient one-step light exposure process to photo cross-link the polymer solution upon demand. The combination of photo cross-linking and diffractive optical technique incorporated within our system enables the patterning of polymer solutions within seconds, making large-scale fast production not only feasible, but also making printing of complex features simple. With this system, 3D two-layered woodpile structures were successfully fabricated within 3 seconds. While cell toxicity studies showed that the scaffold can be used for tissue engineering.

This paper presents a microfabricated nozzleless acoustic droplet ejector with electrically tunable droplet size as a new tool for on-demand picking and placing semiconductor chips for semiconductor packaging. The ejector is based on a 2-mm-thick lead zirconate titanate (PZT) sheet with a planar annular-ring air-cavity acoustic Fresnel lens on top. When driven with sinusoidal pulsed voltage signals of 1.16 MHz, the ejector generates focused ultrasound with 1-mm focal diameter and 5-mm focal depth at 22 mm focal length in sodium polytungstate (SPT) solution. A finite-element-method (FEM) simulation model calculating the acoustic-field-induced fluid motion during the droplet ejection process has been developed, and verified by experiments, in which the device ejects SPT droplets whose diameter is from 850 to 2, $490~\mu \text{m}$ , controlled by the driving pulse width and voltage. The ejected droplets are able to carry 400- $\mu \text{m}$ -thick square silicon chips with side length from 700 to 3, $100~\mu \text{m}$ . A polyester channel-embedded guiding cover for semi-automatic loading of silicon chips to the ejection site is designed to avoid manual placement of the silicon chips. With the proof-of-concept system, we demonstrate ejecting silicon chips out of SPT surface onto a nearby paper, assembling them into arrays with good repeatability. [2020-0337]

As technological components continue to utilize space effectively within devices without compromise to their operational efficiency, the relevance of accurate and precise parts with good tolerances and surface finishing has shot to prominence. Ultra-Precision Machining (UPM) technology has constantly risen to the challenge by realizing components with superior geometrical accuracies and mirror-like surface finishes, much of which are required in the optical industry. However, conventional diamond shaping processes are usually limited to rotary symmetric components or linear gratings. Thus, the developed Virtual Rotating Tool Shaping (VRTS) addresses these issues by enabling the UPM to fabricate non-rotary symmetric, intricate and freeform elements by Direct Diamond Shaping (DDS). VRTS synchronizes the linear and rotational motions of the ultra-precision machine to constantly align the tool with the cutting direction, while compensating in the linear axes for the run-off. As such, DDS can now achieve a combination of linear and rotary features by planing. In this paper, the developed DDS technique is presented with experimental verifications of the algorithm on a segmented bi-focal Fresnel lens and a serpentine micro-channel, followed by the corresponding analyses.

Agricultural greenhouses are commonly built around cities to supply residents with agricultural products or green plants. With an increasing demand for plants’ growing environment, the temperature and illumination inside the greenhouses are counted especially during cold winter. This paper proposes a new construction idea of an energy-saving agricultural greenhouse, by which a solar energy collector is added onto the agricultural greenhouse to improve the energy utilization efficiency. Besides, the solar collector does not occupy extra land resource and merely influence the illumination inside the greenhouse. The design and modeling of solar system are introduced in accordance with the actual parameters of agricultural greenhouse. Then the characteristics of energy collection and inner house’s illumination are elaborated by simulation. It shows that when the inclination incident angle of the sunlight ranges from -38° to 38°, the receiving efficiency of ray in receiver is more than 80%. This implies that the system can work about 5 hours in heat collection. The light environment and the thermal environment are both important. When scattered and direct light are set 40% and 60% of daylight, respectively, the illumination of ground is up to 8.38×105 Lux. The minimum illumination is not less than 4.22×105 Lux. In addition, the illumination of rear wall ranges from 3.05×105 Lux to 7.62×105 Lux. Thus, the light environment in the greenhouse is not influenced and all the indoor activities could be maintained. Finally, local meteorological data are combined with simulated solar collection results to evaluate the economy. It shows that the system could provide about 1887.8 MJ/m2 in six cold months, which approximately equals to 6153.9$ per year.

This paper presents an experimental study using Fresnel lens to increase the overall efficiency of the conventional Single Slope Solar Still (SSSS) with single basin. The work aims to increase the performance of single basin conventional SSSS while maintaining the simplicity and usability of the system. Especially in the rural parts of Oman, the device is very simple to use. For the present unit, the conventional single basin SSSS has been fitted with an adjustable Fresnel lens. The adjustment enables the carrying out the experiments with and without the Fresnel lens at our Institute. The equipment was constructed from simple available materials and was placed north-south during the experimentation. The Fresnel lens fitted frame once adjusted in the morning was kept at same position for the entire day without tracking. The depth of water in the basin was maintained constant at 0.02 m during the study. The distillate yield for single basin SSSS fitted with Fresnel lens is observed 3 to 3.5 times higher than the conventional. The overall efficiency of the system has also increased almost 32.19 percent over the conventional. The quality of the distillate was assessed, which was estimated to be within limits in compliance with international standards. In conclusion, Fresnel lens has significantly improved the distillate production output and overall efficiency of conventional single basin SSSS.

Solar panel power output can still be improved through various means. The aim of this paper is to investigate the effect on solar panel power generation due to Fresnel lens distance to the solar panel. The use of Fresnel lens is to magnify the light intensity from the sun to achieve higher solar collectability of solar panel which may increase power output. The Fresnel lens is to be positioned on top of the solar panel to concentrate the sunlight on to the solar panel. Voltages are measured by an electronic microcontroller with a 10-second interval while power output are determined by the product of voltage and load resistance connected to the solar panel. Immediate results were an instantaneous rise in voltage output but gradually decreasing with increase heat absorption in the solar panel. In the long run, voltage and power outputs were obtained at 0, 5, 10, 20, 30 and 40 cm Fresnel lens distance to the solar panel where all results saw the reduction in voltage and power generation from the solar panel incorporated with Fresnel lens compared to one without due to high ambient temperature. Because of this, it is deemed unfeasible to use Fresnel lens for solar power generation in hot areas such as those with equatorial or tropical climate.

In this paper, a novel small-decentralized desalination device is presented for increasing the temperature difference between brackish water and glass cover, so as to enhance the solar still’s freshwater productivity. This novel solar still device is based on installing a lens in front of the single slope solar still, and two lenses on still’s both sides, and a reflector over the back side of the solar still. The main objective of such novel still is to concentrate sunrays at the still’s bottom basin, through the refraction function of Fresnel lens. Furthermore, this novel still makes the reflector transferring its reflected sunrays to the solar still’s basin. Experiments are conducted under the climate conditions in Hangzhou city, China, for testing the novel still’s operational performance, and internal heat and mass transfer characteristics. Assessment of the novel still’s feasibility is performed based on energy, exergy, exergoeconomic, and enviroeconomic methodologies, as well as energy payback time. Results show that the productivity of novel still is 32% higher than that of conventional still, and novel solar still enhances the average hourly energy efficiency by 97.73%, compared to conventional solar still. While, the corresponding value of hourly exergy efficiency is also enhanced by 43.713%. Due to the higher energy and exergy outputs of novel still throughout its lifetime, the novel solar still proposed in this study mitigates more CO2 compared to the conventional still. Overall, incorporation three lenses and one reflector with the still is found promising in terms of freshwater yield, cost, and energy payback time compared to conventional one. Exergoeconomic and environmental parameters of the novel solar still are found more effective compared to the conventional one.

Based on high efficiency and wide spectral splitter film and Fresnel lens, we have theoretically investigated a full solar-spectrum power-generation system. Designed nano-multilayers are fabricated on Fresnel lens. Then short wavelengths (400 nm ~ 1100 nm) of solar-spectrum can be transmitted 95% to the solar cell, and long wavelengths (1100 nm ~ 2500 nm) of solar-spectrum can be reflected 90% and focused to the thermoelectric cell. This system can combine the efficiency of solar cells and thermoelectric cells to generate electricity across the entire solar spectrum. In theory, the limit for total conversion efficiency is $\eta =56.64$ %.

This paper evaluates the performance of standalone thermal system and cogeneration PVT system under concentrated two stage linear Fresnel lens (FL) based system with convex lens as Secondary Optic Element (SOE). Experiment for standalone thermal system with two stage concentrator investigates the thermal efficiency of the system with copper plates as thermal collector. The experiments to obtain VI characteristics of PV module were done without lens, then with FL and with both FL/CL. The electrical efficiencies were 12.23%, 11.5% and 9.2% respectively which shows fall in efficiency as a result of concentration. Peak powers were 3.42 W, 3.74 W and 4.23 W respectively which shows there is rise in output power. Increase in output power from no lens to single lens was 9.3% and increase in output power from single lens to two stage lenses was 13.1%. The position of Primary Optic Element (POE) was determined by adjusting distance from 10 cm to 35 cm. At 30 cm max power was obtained so POE was kept at 30 cm. In similar manner, SOE was positioned at 15 cm from POE. The net efficiency of standalone thermal system and PVT system with two stage concentrations was 47.61% and 53.7%.

The emergence of solar PV systems is an important area of research due to the availability of these photovoltaics at cheaper rates. The emerging technology of PV is already being used in many parts of the world as a source of energy to reduce dependence on non-renewable sources. The recent popularity of Photovolatalic Thermal systems also known as PV/T systems is in consideration due to their increased efficiency over conventional PV systems. The authors in this paper intend to show the various aspects of PV integrated with thermal systems, the PV/T systems. The Fresnel lens is used as a concentrator for focussing the sunlight on the PV cells. Various publications about Fresnel lenses show that they are of prime importance in the cogeneration of power and heat effectively. Various thermal and electrical aspects, modifications in the conventional PV/T systems have been discussed. To conclude this review paper, problem areas associated with the PV/T systems have been mentioned. Further research is suggested to improve the design, effectiveness, and reduce the overall cost of the system.

Solar disinfection, as a low carbon technology, is a sustainable and cost-effective water treatment method, which makes it more likely to be implemented in developing countries. It has been proven that ultraviolet light radiation is effective against pathogens and microorganisms. The aim of this paper is to evaluate the performance of solar disinfection apparatus that is equipped with Wood’s glass and a Fresnel lens. Wood’s glass is a band-pass filter that allows ultraviolet light to go through and blocks most of the remaining spectrum including infrared. This serves a dual purpose. It lets through the part that inactivates pathogens and microorganisms (ultraviolet) and blocks the part that helps the growth of bacteria (infrared). Experimental setup is designed to investigate the effect of Wood’s glass with and without a Fresnel lens on the solar disinfection process. The investigation is done on a batch-based system and on a novel instantaneous water disinfection system. Results of water disinfection process were recorded for each set of experiments taking into considerations vital parameters, such as solar radiation, solar ultraviolet light intensity and water temperature. The results of these experiments showed effective water disinfection up to 85% pathogens removal by the use of daily available solar radiation.

Besides the prohibitive cost, complexity, and baseband scale, the development of millimeter-wave (mmWave) digital-beamforming fifth-generation (5G) frontends is facing a physical-layer challenge of thermal dissipation. This is caused by the massively integrated power amplifiers (PAs) and the extremely compact volume due to millimeter-scale wavelengths. In this work, we theoretically analyze and experimentally demonstrate a reconfigurable planar Fresnel lens, based on which a new-concept mmWave beamforming frontend can be implemented with significantly reduced number of PAs. It overcomes the inherent shortcomings of analog beamforming solutions relying on massive use of power dividers and phase shifters and can replace the convex lens used in the recently proposed hybrid beamforming solution. The implemented Ka-band lens is simple-structured, cost-effective, and easy to control, providing multiple modes for beamspace massive-multiple-input multiple-output (MIMO) communications. Experimental results verified its potential in different mmWave 5G systems such as base stations and point-to-point links.

A multi-pass side-pumping scheme for solar pumped Nd:YAG laser on 1 m diameter Fresnel lens is numerically analyzed. Using of the Monte Carlo photon-tracing numerical method, three different pumping schemes were studied. The results showed that a large efficiency improvement in a multi-pass side-pumping scheme compared to the double-pass side-pumping scheme. The study demonstrated that the multi-pass side-pumping scheme can double the overall efficiency of solar double-pass side-pumped Nd:YAG laser.

Energi matahari dapat dikonversikan menjadi energi termal dengan menggunakan kolektor surya maupun menjadi energi listrik dengan menggunakan sel surya/ photovoltaic . Radiasi matahari bersifat menyebar, sehingga memerlukan pengumpul atau pengarah agar lebih fokus. Ada banyak penelitian yang menggunakan lensa Fresnel untuk mengumpulkan radiasi matahari pada sel surya. Sedang penelitian lensa Fresnel pada kolektor surya masih terbatas sebagai concentrator . Makalah ini membahas perancangan dan pemakaian lensa Fresnel sebagai penutup pada suatu kolektor surya plat datar. Lensa Fresnel komersial hanya memiliki 1 titik fokus, maka langkah pertama penelitian adalah merancang lensa Fresnel dengan enam titik fokus. Jarak focus dirancang agar radiasi matahari jatuh ke plat penyerap pada jarak 90 mm dari lensa Fresnel. Bahan yang digunakan adalah PMMA Polymethyl methacrylate (acrylic) dan pembuatan profil lensa menggunakan proses tekan. Lensa Fresnel yang dihasilkan berhasil memiliki titik fokus 90 mm. Lensa Fresnel yang dihasilkan dipasang sebagai penutup pada kolektor surya plat datar. Hasil yang didapat adalah temperatur plat penyerap dengan lensa Fresnel lebih tinggi daripada dengan acrylic polos yang sebenarnya lebih bening. Temperatur maksimum di kiri atas plat penyerap dengan lensa Fresnel dapat mencapai 1.42 kali lebih tinggi daripada temperatur yang dihasilkan oleh acrylic polos. Temperatur cairan di inlet dan dalam tangki pada kolektor surya yang menggunakan lensa Fresnel lebih tinggi daripada temperatur cairan di kedua lokasi yang sama yang menggunakan acrylic polos.

The study was conducted to evaluate the thermal performance of a box-type solar cooker (BTSC) by implementing two Fresnel lens magnifiers (FLMG) which concentrate the solar irradiance on to the coo...

Dust deposition causes a significant loss of performance of a high-concentration photovoltaic thermal (HCPV/T) system. In this paper, the influence of dust deposition on the output performance of a gallium arsenide cell HCPV/T with a Fresnel lens was investigated using a dust deposition test. The changes in the thermoelectric and exergy performance of the system were analyzed at different dust densities. The influence of the dust particle size on the relative overall efficiency was determined. The results showed that the thermal efficiency and electrical efficiency decreased by 2.65% and 1.29%, respectively, for a 1 g/m2 increase in the dust density. At the same dust density, the relative overall efficiency was lower for the smaller dust particle size. Model fitting and calculations indicated that the rate of decline in power output reached the maximum at a dust density of 9.84 g/m2. The results provide references for similar experiments.

Millimeter-wave lens antennas will be essential for future wireless access. Conventionally, they increase the gain in the boresight direction only. In this article, cascaded Fresnel zone plate lenses are combined with a phased array to increase the gain at wide steering angles of ±52°. The side lenses are tilted to align with the maximum steering angle and cascaded to increase the focusing gain. The inner lenses increase the gain by 2.45 dB at boresight, and by 3.19 dB at the maximum steering angle. When the side lenses are repositioned, the simulated focusing gain increases to 4.69 dB. Asymmetric amplitude distributions are proposed to prevent the main lobe from splitting. An eight-element seven-lens prototype operating at 28 GHz achieved a gain from 12.96 to 15.35 dBi with a bandwidth of at least 1.3 GHz for all measured beam directions. The maximum measured azimuthal beamwidth was 27°. A design procedure and a theoretical analysis of diffraction through the lenses are provided. By increasing the SNR, this beamforming antenna could improve the coverage of three-sector 5G microcell base stations, and support gigabit wireless links for vehicular, rail, and satellite communications.

This paper describes a novel acoustic transducer with dual functionality based on 1-mm-thick lead zirconate titanate (PZT) substrate with a modified air-cavity Fresnel acoustic lens on top. Designed to let ultrasound waves focus over an annular ring region, the lens generates a long depth-of-focus Bessel-like focal beam and multiple trapping zones based on quasi-Airy beams and bottle beams. With 2.32 MHz sinusoidal driving signal at 150 $\text{V}_{\mathrm {pp}}$ , the transducer produces a focal zone with 9.9 mm depth-of-focus and 0.8 MPa peak pressure at a focal length of 31.33 mm. With 2.32 MHz continuous sinusoidal drive at 30–35 $\text{V}_{\mathrm {pp}}$ , the transducer is able to trap multiple polyethylene microspheres (350–1, $000~\mu \text{m}$ in diameter and 1.025–1.130 g/cm3 in density) in water either simultaneously (when suspended by mechanical agitation or released from water surface) or sequentially (when placed one after another with a pipette). The largest particles the transducer could trap are two 1-mm-diameter microspheres stuck together (1.07 mg in weight, lifted by buoyancy and $0.257~\mu \text{N}$ acoustic-field-induced force). When the transducer is moved laterally, some firmly trapped microspheres follow along the transducer’s movement, while being trapped. When trapped, some microspheres can rotate due to the rotation torque generated by the quasi-Airy beams. [2020-0184]

The study to investigate the thermal performance of solar cooker using a spot Fresnel lens for concentrators of solar thermal energy is conducted. The main objectives of the present work are: a)to develop a new design of the cooking pot of solar cooker as an absorber of solar thermal from a spot Fresnel lens; b)to analyze the relationship of several temperature parameters in the cooking pot with the thermal efficiency of the Fresnel solar cooker (FSC); c)to conduct field test by heating test and cooling test to obtain a performance characteristic of FSC. The experimental test was conducted at Brawijaya University (7.9553°S, 112.6145°E), East Java, Indonesia during August – September 2019. The Fresnel lens operation method uses the azimuth manual tracker to concentrate direct normal irradiance (DNI). The measurement of Direct Normal Irradiance (DNI) was made by the SM 206 Solar Power Meter and placed on the FSC frame. A new design of solar cooking pot has been developed. That is a cylindrical shape for boiling water and food cooking with a cone cavity as a solar collector. While on the cooking pot, the temperature sensor is placed: 1)ambient temperature; 2)cooking pot temperature; 3)focal point temperature on the receiver surface; 4)water temperature in the solar cooking pot. It is connected to the Digi-Sense 12 CH-Scanning Benchtop Thermometer for temperature data acquisition system. The measurement of wind speed was made by Cup Anemometer ABH-4224. The procedure for testing the FSC was developed based on existing international testing standards. The receiver/cooking pot was tested for thermal performance characteristics of cooking by conducting the following tests: 1)no-load test; 2)water heating and cooling tests. The experimental results show that the average stagnation temperature in a cooking pot with a conical cavity receiver was 267.35°C. The receiver shape with a conical cavity has better heat transfer capability and low heat losses, hence, making it suitable for applications on FSC. DNI ±850W/m² produces a focal point temperature of 1064°C, a heat removal factor of 7.39W/m².°C, and an optical efficiency factor of 0.312. Therefore, the thermal efficiency of the FSC is 27.72%. The thermal efficiency tends to decrease until the end of the process due to the influence of the optical efficiency factor

Nondispersive infrared CO2 gas sensor was developed after the simulation of optical cavity structure and assembling the optical components: IR source, concave reflectors, Fresnel lens, a hollow disk, and IR detectors. By placing a hollow disk in front of reference IR detector, the output voltages are almost constant value, near to 70.2 mV. The absorbance of IR light, Fa, shows the second order of polynomial according to ambient temperatures at 1,500 ppm. The differential output voltages and the absorbance of IR light give a higher accuracy in estimations of CO2 concentrations with less than ± 1.5 % errors. After implementing the parameters that are dependent upon the ambient temperatures in microcontroller unit (MCU), the measured CO2 concentrations show high accuracies (less than ± 1.0 %) from 281 K to 308 K and the time constant of developed sensor is about 58 sec at 301 K. Even though the estimation errors are relatively high at low concentration, the developed sensor is competitive to the commercial product with a high accuracy and the stability.

This paper presents a novel method approaches to simplify refractions on prisms to get the ideal shape of the Fresnel lens. A simplification is about to use one refraction on the upper surface to replace the two refractions on the upper and the lower surfaces. A differential equation that describes the ideal shape of Fresnel lens has been derived out. It shows that the particular solution of the differential equation is a bunch of confocal curves. Especially, the ideal curves are closing to their basic circle when total refracted angle less is than 30°, which makes it reasonable to use the basic circle as the profile of Fresnel lens. Then a Fresnel lens was designed with considering material and manufacturing technology. Then an analysis on the focal length change during the tilt incidence was mainly carried via simulation and experiment. It is found that the effective tilt incident angle can be enhanced from 7° to 32° by lifting up the position of the receiver and adding a simple mirror secondary reflector. The experimental result shows that the Fresnel solar concentrator is working efficiently during the time from about 10:00 to 14:30 a day. The steady output temperatures are 125 °C, 150 °C and 170 °C, with collection efficiencies are about 0.53, 0.48 and 0.44. It can well satisfy mid-temperature solar thermal application.

The paper discusses the comparison of the performance of steam generators in large and small receivers, using a Fresnel lens concentrator. The goal is to get the best value from the efficiency of a steam generator between large and small receivers, with the following task details: a)design a conical cavity receiver that has the most efficient geometric concentration ratio; b)compare the thermal efficiency of conical cavity receivers that have different geometric concentration ratios; c)analyze the potential of the steam energy from the conical cavity receiver produced by the PMMA Fresnel lens concentrator based on theamount of average radiation directly at the study site. The study uses an experimental field research method, which is conducted outdoors. This research was conducted in the energy conversion laboratory, Universitas Brawijaya (Latitude: 7.9553°S and Longitude: 112.6145°W), in September 2019. The PMMA Fresnel lens is used for the solar thermal concentrators. The two receivers with a conical cavity that were compared were made of copper with a volume of 2 litres and 0.25 litres, respectively. They are coated with a glass wool insulator with a thickness of 10mm. Direct Normal Irradiance (Ib) is measured by a solar power meter. The cup anemometer is used to measure wind speed (vw) around the receiver. Digi-Sense 12 Channel Scanning Benchtop Thermometer connected to the laptop is used to measure temperature. The positions of the four K-type thermocouples are as follows: 1)ambient temperature (Ta); 2)focal point temperature (Tf); 3)receiver wall temperature (Tr); 4)steam/water temperature (Tw). A pressure gauge to measure the pressure of the steam that goes to the measuring cup was used. After saturation pressure (Psat) has been reached, it will be known from the condensation process through the copper coil, which functions as a condenser. From the results of the study, the large receivers have specifications CRg=8 and a volume of 2 litres of water. Whereas, the small receiver is CRg=30 and 0.25L. The large receivers can produce steam latent heat energy Qs=1.37MJ per cycle with useful efficiency (utilization efficiency) ηTh=31.81%. Whereas the small receiver can produce steam energy, Qs=579.17kJ per cycle with useful efficiency, ηTh=33.31%. Hence, from the two types of conical cavity receivers, small receivers have that higher effectiveness than large ones can be recommended

A Fresnel lens with blue phase liquid crystal (BPLC) material is proposed, and the mainly electrical field in BPLC layer is parallel to substrates. The structure and proportion of the applied volta...

Fresnel lenses allow the concentration of sunlight that can be employed in different thermal unitary operations or endothermic chemical transformations. A system with Fresnel lenses should also take into account vessel or reactor surface thermal losses (reflection, convection and emission), as well as the thermal energy required to keep the vessel or reactor structure warm. In this paper, a numerical and experimental analysis indicated that the solar radiation incident on the lens, the Fresnel lens area and the specimen mass can be represented by a grouping called Heating Factor (31 ≤ Ψ (W/kg) ≤ 3347). The Heating Factor (Ψ) was strongly correlated with the maximum temperature conductive specimens could reach when inserted at the focal point of a Fresnel Lens. Equilibrium Temperatures were predicted by a physical-mathematical model and validated by experimental tests. The Fresnel lens system has been shown to be able of providing Equilibrium Temperatures from 345 to 1600 K for specimens with Heating Times between 3 and 85 min and Initial Thermal Rates from 1.16 to 312.00 K/min. Numerical-experimental analyses also showed that the heating dynamic was strongly influenced by the nature of the materials that constituted the specimens (specific mass and the specific heat).

A novel apparatus has been designed, simulated and fabricated to harness solar energy for indoor solar cooking and day lighting purposes. Herein, a fixed orientation collimated beam of concentrated sunlight has been achieved irrespective of the sun’s position using three optical components, viz. concentrator, reflector and collimator with a dual axis tracking system. Two different designs were simulated using optical ray tracing simulations and the optical output was compared. The first design uses a paraboloidal reflector while the second design uses a Fresnel lens as concentrator. Simulation results show that the first design employing paraboloidal reflector has 52.5% optical loss just after the collimator and 52.9% loss at a 4 m distance from the collimator. Similarly, the second design has 50.6% optical loss just after the collimator and 61.8% loss at a 4 m distance from the collimator. The prototype of the Fresnel lens-based design with automatic dual axis tracking was fabricated and the system was tested from morning to evening. Stationary focal spot was observed throughout the day irrespective of the sun’s position demonstrating the feasibility of the system for transporting solar energy for indoor applications. Optical loss of the prototype system was measured and was compared with the simulation results. Optical loss for the prototype just after the collimator was found to be 61.6% which is in good agreement with the simulation results. Thus, the developed novel system can be used as an alternative and clean source of energy for indoor solar cooking and day lighting applications.

Enhancement of solar intensity is achieved through concentrator which focuses direct normal irradiance to a smaller area. Such redirection necessitates aligned movement of the whole assembly along the apparent motion of the sun. The motion of a bulky system consumes significant power during the operation, thereby reducing the effective energy collection efficiency. Therefore, a static geometry which does not require tracking the sun is desirable as concentrating optics. Here, we propose such a novel static concentrator based on cylindrical Fresnel lens. Only the absorber is given a single axis tracking motion. A systematic optimization is performed to select the geometrical parameters which maximize the solar intensity and minimize the intensity-non-uniformity. For a Silicone glass cylinder of 20 cm diameter, we find an absorber of width 5 cm, placed at a distance of 11 cm from the axis of the concentrator provides the maximum intensity and the minimum intensity-non-uniformity when the vertex angle of the Frensel lens is 37°. The study demonstrates that the procedure to perform such geometry optimization is straightforwardly extendable. We demonstrate that the annual average intensity on the absorber can be enhanced by over ∼50% with lower operational cost and a meagre increase in the initial cost.

Roll-to-roll (R2R) embossing is a low-cost and high-productivity manufacturing process that replicates the microstructures from a cylindrical impression mold onto flexible films with high resolution and accuracy. However, discontinuous non-rotationally symmetric microstructures are very difficult to fabricate on either planar or cylindrical surfaces. In this paper, a novel machining method, diamond micro-scraping (DMS), is developed to provide a possible solution for the fabrication of polygonal Fresnel lens structure on the roller mold. In the proposed DMS machining method, the tool path is generated according to geometrical calculations considering the structural design of the drum roll lathe, the polygonal Fresnel lens structure designed, diamond tool geometries, and parameters of the roller mold. Through a series of processing experiments, the feasibility of DMS machining method is verified, and polygonal Fresnel lens structure is fabricated on the roller mold. The experimental results show that the profile accuracy of the processed polygonal Fresnel lens structure is at the submicron level and the surface roughness is several nanometers. The proposed DMS machining method can meet the requirement of embossing high-precision optical roller mold.

In this communication, we experimentally demonstrate a frequency- and beam-reconfigurable lens antenna based on an active second-order bandpass frequency-selective surface (FSS). The FSS lens is composed of three nonresonant metallic layers separated by two thin dielectric substrates. By integrating microwave varactors in FSS unit cells, the center frequency of this bandpass FSS can be tuned from 4.0 to 5.8 GHz by a direct-current (dc) bias voltage. Based on this wideband tunability, the phase-correction technique is used to implement a microwave Fresnel lens. The experimental results show that the proposed 1-D lens antenna can achieve frequency-reconfigurable beam steering within a 1 GHz bandwidth. With advantages of low cost and concise structure, the proposed reconfigurable lens antenna can be potentially used in a wide range of applications.

Renewable energies have a high impact on power energy production and reduction of environmental pollution worldwide, so high efforts have been made to improve renewable technologies and research about them. This paper presents the thermal performance results obtained by simulation and experimental tests of a parabolic trough collector with central receiver coupled to Fresnel lens, under different configurations on the pipe. The simulation method was computational fluid dynamics (CFD) analysis in Solid Works® soft-ware tool, which works with Naiver-Stokes equations to converge on a solution. Experimental tests were formed with all configurations proposed and three observations for each one, a total of 12 observations were performed in all research. As a result, the best thermal performance in simulation was achieved with the Fresnel lens and black pipe collector, with a maximum temperature of 116 °C under 1 000 W/m2 radiation, the same system achieved in experimental tests a maximum temperature of 96 °C with a radiation of 983 W/m2.