Search

A photovoltaic-thermal side-absorption concentrated module (PT-SACM) based on spectrum division for photovoltaic-thermal hybrid applications is carried out. In order to reduce the absorption by materials and the axial-chromatic aberration caused by the transmissive optical system and to improve the performance of the entire system, a reflective system, the parabolic mirror array, fabricated by the ultra-precision diamond turning technology, is proposed herein. For the purposes of spectrum division, thinner volume, lightweight, and wide acceptance angle, the proposed module is designed with a diffraction optical element (DOE), a light-guide plate with a micro-structure array and a parabolic mirror array. Among them, the DOE can separate the solar spectrum into the visible band, which is converted to electrical energy via photovoltaics, and the infrared band, whose thermal energy is collected. Experimental measurements show that the overall optical efficiency of the entire system reached 38.32%, while a deviation percentage of 3.5% is calculated based on the simulation. The system has successfully demonstrated the separation of visible and infrared bands of the solar spectrum. Meanwhile, the lateral displacement between the micro-structures of the light-guide plate and the focus of the parabolic mirror array can be used to compensate for the angular deviation of the sun incidence, thereby achieving wide-angle acceptance via the proposed solar concentration system. [ABSTRACT FROM AUTHOR]

This study focuses on the simulation of a solar photocatalytic reactor with linear parabolic reflectors and continuous fluid flow. The simulation approach was initially validated against experimental data reported by Miranda-Garcia et al. Catal Today 151:107-113 (2010), yielding a high degree of accuracy of approximately 0.99%. In this article, the effect of light intensity, Reynolds number, and fluid residence time on the performance of a photoreactor system using titanium dioxide catalyst and ibuprofen pollutant has been investigated. The results show that the intensity of light intensity has an effect of up to 29% on the decomposition of pollutant. With the increase of radiation intensity, the removal of pollutants reached from 85.5% to 99.46%. It has been demonstrated that higher flow turbulence significantly impacts removal efficiency, achieving rates of up to 71%. Moreover, enhancing the fluid's residence time through implementing a recirculating flow within the photoreactor has resulted in a 13% enhancement in removal efficiency. These results can be an important guide for optimizing the design of photocatalytic reactors. By adjusting the examined parameters, it is possible to obtain a higher efficiency in the removal of pollutants, which will be very effective in the scaling and industrial design of solar reactors. [ABSTRACT FROM AUTHOR]

AbstractAmong the four available concentrating solar-thermal (CST) power systems, parabolic dish systems show great potential as the preferred technology for renewable electricity generation. Nonetheless, the weight of the support structure poses a major hurdle to its development. As of present, solar dishes utilize steel structures to hold the reflective panels which amount to a lot of weight, necessitating large and expensive drive units and increases energy consumption. Hence, for the dishes to advance and further become economically feasible in the near future, the structures found need to be replaced with cost-effective materials that not only diminish the weight but still maintain the structural integrity found with the steel. Hence, this investigation embodies the first effort in literature to explore the viability of utilizing honeycomb sandwich composites as a lightweight and robust support structure for solar dishes, with the ability to cope with the aerodynamic loads imposed upon them during operation. Through combined fluid-structure interaction (FSI) and ray tracing analysis, the wind-induced structural behavior and optical performance of the sandwich composite-based paraboloidal solar dish were investigated under various loading scenarios at various azimuth and elevation angles. Under dissimilar operational conditions, the proposed system exhibited varying behavior characteristics, with the worst conditions being assessed according to relevant material failure and optical standards. With the worst operational condition taking place at 0° azimuth and 30° elevation, the detailed FSI-ray tracing analysis demonstrated that the dish managed to satisfy the set specifications, highlighting the potential and effectiveness of using honeycomb sandwich composites as a support structure for parabolic dish systems. [ABSTRACT FROM AUTHOR]

X-ray spectroscopies are uniquely poised to describe the geometric and electronic structure of metalloenzyme active sites under a wide variety of sample conditions. UV/Vis (ultraviolet/visible) spectroscopy is a similarly well-established technique that can identify and quantify catalytic intermediates. The work described here reports the first simultaneous collection of full in situ UV/Vis and high-energy resolution fluorescence detected x-ray absorption spectra. Implementation of a fiber optic UV/Vis spectrometer and parabolic mirror setup inside the dual array valence emission spectrometer allowing for simultaneous measurement of microfluidic flow and mixing samples at the Photon-In Photon-Out X-ray Spectroscopy beamline is described, and initial results on ferricyanide and a dilute iron protein are presented. In conjunction with advanced microfluidic mixing techniques, this will allow for the measurement and quantification of highly reactive catalytic intermediates at reaction-relevant temperatures on the millisecond timescale while avoiding potential complications induced by freeze quenching samples. [ABSTRACT FROM AUTHOR]

Porous ceramics find extensive applications in aerospace and other fields, and the measurement of their electromagnetic parameters is helpful in optimization of material properties and device designs. In this paper, a free-space 8f quasi-optical measurement system consisting of a vector network analyzer, a 325–500 GHz frequency expansion module, and four off-axis parabolic mirrors have been established to measure the transmission parameter S21 of porous ceramics. The complex permittivity was extracted according to the Newton-Raphson iterative method utilizing its measured S21 parameters based on flat mode. The porous ceramics with different porosity and density were measured and the relationships between their permittivity and porosity and density was established, respectively. These results are beneficial to the quality evaluation and application design of porous ceramic materials in the aerospace field. [ABSTRACT FROM AUTHOR]

Laser-produced plasma is a promising compact light source applicable in a broad range of wavelengths. We performed a spectroscopic analysis and plasma characterization of the laser-produced plasma of Al, Fe, Cu, and Inconel alloy (Ni/Cr/Fe) to explore their potential applications in the far-ultraviolet (FUV) region where these methods are yet widely exploited. The emission spectrum from each target exhibited a characteristic spectral profile over the wavelength range from 120 to 250 nm. These results were well reproduced by spectral simulations, providing detailed information on the plasma. We also developed a dedicated parabolic mirror that successfully collimated the plasma radiation into beam with an intensity enhanced by a factor of ∼ 35. Our study demonstrated the generation of collimated FUV radiation with an intensity of a 10 7 photons/pulse/1% bandwidth as a potent laboratory-size light source for various applications. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of solar trough collector with a spliced cylindrical mirror and develops a new ray-tracing method to predict and optimize its performance. The mirrors of this system are composed of multiple cylindrical mirrors whose centers are on a parabola, and the normal vector of the centers of each cylindrical mirror is consistent with the normal vector of the parabola point where it is located. The new ray-tracing method is based on the transverse distribution of solar radiation, and it has been validated with Soltrace, with the maximum intercept factor error in the calculations being less than 0.31%. This paper compares the spliced cylindrical mirror trough solar system with the conventional parabolic trough system and finds that the influence of cylindrical, spherical, and coma aberration can be reduced to negligible levels by adjusting the system design. At the same time, the slope error and cost of the cylindrical mirror are much less than the parabolic mirror so it has better performance from numerical simulation. The spliced cylindrical mirror system can be further optimized to achieve an annual net efficiency of 65.52% in the north–south horizontal axis tracking mode. [ABSTRACT FROM AUTHOR]

In this study, a rapid and accurate optical axis alignment technique of a reflective beam expander composed of convex and concave off-axis parabolic mirrors was established by using (a) five parallel lasers and (b) shear interferometry. The five parallel lasers are placed on the top, bottom, left, and right sides, and center of the disc fixture, forming a circular symmetrical distribution and parallel to each other. Since the convex and concave off-axis parabolic mirrors are both confocal systems, the central laser of the five parallel laser beams is incident along the optical axis of the reflective beam expander, and the surrounding four beams diverge outward after the first reflection of the convex off-axis parabolic mirror, and these diverging laser beams converge inward after the second reflection of the concave off-axis parabolic mirror, so that the four output beams are parallel to each other, maintaining a circular distribution and a large diameter, but the divergence angle is relatively small relative to the incidence. The optical plate with excellent parallelism is placed in front of the collimated beam at an angle of 45°. The reflected beams on both sides of the optical plate are expected to interfere. In this study, this shear interferometry method was used to measure the collimation of a parallel beam after passing through a reflective beam expander. In this experiment, a HeNe laser was used as the light source, and its wavelength and beam diameter were 0.6328 μm and 3 mm, respectively. The test sample is a beam expander with a magnification of 2× and an incident beam diameter of 3 mm. After 30 repeated tests, the experimental results showed that the beam diameter increased to 5.78 mm and that the magnification accuracy was 96.3%. [ABSTRACT FROM AUTHOR]

The technology of solar still shows up as an effective and affordable solution to convert available brackish water into potable water. The present study aims to address the challenge of providing freshwater by desalinating brackish water using solar energy. An attempt has been made in this work to make a desalination system for the efficient utilization of solar energy by using a parabolic reflector and energy‐storage material. Modification in the desalination system and storage of energy facilitates the continuation of the process in sunshine and off‐sunshine hours which increases yield output. To investigate the objectives, helical‐shaped focal tubes and nano‐enhanced phase change material (PCM) are prepared. The desalination system is coupled with nano‐enhanced PCM by placing it in the annular space of a helical‐shaped focal tube. The heat transfer coefficient ranged from 11.46 to 28.77 W/(m² K). PCM 3 (i.e., base PCMs with 1.5% nanoadditives) achieved a maximum productivity of 3533.3 mL/m²/day, marking a 97.89% improvement over the system without PCM. The preheated water outlet temperature reached 67.4°C, and the basin water temperature was 75.35°C. The highest concentrator efficiency recorded was 49.82% at a mass flow rate of 0.0053 kg/s. Thermodynamic analysis showed a 67.19% enhancement in overall thermal efficiency with PCM 3 compared with the non‐PCM scenario. Additionally, the system attained a maximum average exergy efficiency of 12.29% and the shortest payback period of 115 days. The study concludes that the base PCM sample with a 1.5% mass concentration of nanoparticles was optimal. [ABSTRACT FROM AUTHOR]

There is an increasing need for sustainable solar thermal energy systems for power production, desalination, cooling and heating, and even cooking in the current world. The most significant challenge for the further development of solar-based technology is the discontinuity and lack of solar irradiance, especially on cloudy days and night hours. Thermal energy storage is the most suggested technology to tackle this challenge partly or mostly. Phase change materials can have a notable role as thermal energy storage in solar thermal energy systems. Besides, parabolic dish collectors are a type of solar collector technology that can be utilized in various thermal systems due to their high concentration ratio and working temperatures. Hence, in this review, the applications of phase change materials in various solar parabolic dish collectors will be investigated in detail. Moreover, the research works are divided into five main categories: power production systems, cooling-heating systems, desalination systems, solar cooker systems, and multigeneration systems. Based on the literature, studies of phase change material's applications in dish collectors are currently limited to theoretical studies in several cases. There is vast research need for further experimental investigations in all the mentioned categories. To this end, some concluding points and suggestions for future studies will be presented to the researchers. [ABSTRACT FROM AUTHOR]

Syngas rich in hydrogen, generated through renewable‐powered co‐electrolysis of water (H2O) and carbon dioxide (CO2) using solid oxide electrolysis cells (SOEC), have gained significant attention due to its high efficiency and conversion rates. This method offers a promising solution for mitigating global warming and reducing CO2 emissions by enabling the storage of intermittent renewable energy. This study investigates solar‐integrated co‐electrolysis of H2O and CO2 via SOEC to produce hydrogen‐rich syngas, which is then utilized for methanol synthesis through a series of heat exchangers and compressors. Parabolic dish solar collectors supply thermal energy, while photovoltaic modules provide electricity for SOEC operation. CO2 from industrial processes is captured and combined with steam at the SOEC inlet for co‐electrolysis. The proposed system is modeled using engineering equation solver software, incorporating mass, energy, and exergy balance equations. The system's performance is analyzed by varying key parameters such as direct normal irradiance, heat exchanger effectiveness, current density, cell temperature, and pressure. The proposed system achieves a solar‐to‐fuel efficiency of 29.1%, with a methanol production rate of 41.5 kg per hour. Furthermore, an economic analysis was conducted to determine the levelized cost of fuel. [ABSTRACT FROM AUTHOR]

This study proposes parabolic dish-based, toroidal-structured fractal solar collectors. The potential of fractal geometry to increase heat transfer and the ability of the parabolic dish to concentrate solar rays form the basis of the proposed design for increasing efficiency. In this study, the thermal and hydrodynamic behaviors of the proposed 3-row, 4-row, and 5-row parabolic collectors were investigated comprehensively. Using theoretical modeling and experimental results, the performances of the proposed parabolic dish-based toroidal fractal solar collectors were evaluated and compared via numerical simulation methods. After the experimental studies of the 3-row toroidal fractal collector, the analysis studies were completed using the ANSYS-Fluent program. Then, simulations were carried out for other toroidal solar collectors using the results of these experimental studies. As a result of the converging numerical analyses, the radiative, hydrodynamic, and thermal analysis results of the toroidal absorbers in 3-row, 4-row, and 5-row structures integrated with the parabolic dish were compared. In the temperature distribution analysis, it was observed that the parabolic dish effectively focuses on the sun rays and provides a gradual temperature increase of approximately 21 K for the fractal collector. It is observed that 96.84% convergence was achieved between the experimental and numerical results. [ABSTRACT FROM AUTHOR]

A multirod Ce:Nd:YAG solar laser approach, using a Fresnel lens as a primary concentrator, is here proposed with the aim of considerably increasing the efficiency of solar-pumped lasers. Fresnel lenses are cost-effective, rendering solar lasers more economically competitive. In this work, solar-pumped radiation collected and concentrated using the Fresnel lens is received by a secondary three-dimensional compound parabolic concentrator which transmits and funnels the light toward the Ce:Nd:YAG laser rods within a water-cooled tertiary conical concentrator that enables efficient multipass pumping of the rods. To explore the full potential of the proposed approach, the performance of various multirod configurations is numerically evaluated. Through this study, configurations with three and seven Ce:Nd:YAG rods are identified as being the most efficient. A maximum continuous wave total laser power of 122.8 W is reached with the three-rod configuration, marking the highest value from a Ce:Nd:YAG solar laser, leading to solar-to-laser conversion and collection efficiencies of 7.31% and 69.50 W/m2, respectively. These results represent enhancements of 1.88 times and 1.79 times, respectively, over the previous experimental records from a Ce:Nd:YAG/YAG single-rod solar laser with a Fresnel lens. Furthermore, the above results are also 1.58 times and 1.68 times, respectively, greater than those associated with the most effective three-rod Ce:Nd:YAG solar laser utilizing a parabolic mirror as the main concentrator. The present study also shows the great usefulness of the simultaneous pumping of multiple laser rods in terms of reducing the thermal stress effects in active media, being the seven-rod configuration the one that offered the best compromise between maximum efficiency and thermal performance. This is crucial for the applicability of this sustainable technology, especially if we wish to scale our system to higher power laser levels. [ABSTRACT FROM AUTHOR]

Hybrid solar concentrating systems are recognized for their superior efficiency in generating both electricity and heat from solar radiation compared to standalone thermal or photovoltaic systems. However, these systems require greater technological maturity, are complex to produce, and are currently expensive, which restricts their commercial deployment. Few reported prototypes exist, and they offer significant opportunities for improvement. This article presents a prototype of a photovoltaic thermal concentrator that uses a parabolic dish, state-of-the-art multi-junction solar cells equipped with secondary optics, and an easy-to-build active cooling system with straight fins as channels to circulate water. It covers the design, optical simulation, construction, and electrical characterization of the prototype. One advantage of the prototype is its more straightforward structure compared to other reported prototypes, which facilitates manufacturing. The prototype was tested outdoors with and without active cooling. In the first case, it was observed that without the cooling system, the concentrating photovoltaic receiver temperature exceeded 108 °C, causing the electrical efficiency to drop to 8.31%. In the second case, the receiver temperature was maintained below 50 °C. Under clear-sky conditions, the system achieved an average real concentration of 414.8 suns and an average electrical efficiency of 29.75%, representing one of the highest efficiencies reported for these hybrid systems. This experimental study marks a fundamental step toward advancing photovoltaic thermal concentrator systems and bringing them closer to technological maturity. This study demonstrates a scalable solution for hybrid solar concentration, showcasing significant advancements in thermal management and system efficiency. [ABSTRACT FROM AUTHOR]

Conic sections are commonly used in reflective X‐ray optics. Hyperbolic mirrors can focus a converging light source and are frequently paired with elliptical or parabolic mirrors in Wolter type configurations. This paper derives the closed‐form expression for a mirror‐centered hyperbolic shape, with zero‐slope at the origin. Combined with the slope and curvature, such an expression facilitates metrology, manufacturing and mirror‐bending calculations. Previous works consider ellipses, parabolas, magnifying hyperbolas or employ lengthy approximations. Here, the exact shape function is given in terms of the mirror incidence angle and the source and image distances. [ABSTRACT FROM AUTHOR]

Solving global water shortages has become an urgent challenge, hindering sustainable development. Therefore, comparing different solar still designs from application and economic perspectives is necessary. Solar distillation is considered a major innovation in the alternative energy sector for purifying brackish or brine water into clean water. Despite the extensive literature on improved solar stills, determining the most efficient designs for residential and industrial applications remains difficult. This review compares the productivity of spherical, hemispherical, and tubular solar still designs. The aim is to study the factors that influence the efficiency of each type and to analyze recent research and results obtained under different conditions. The results show that innovations in solar distillation design can take many forms to improve efficiency and productivity. For example, adding parabolic mirrors can increase productivity in spherical, hemispherical, and tubular stills by 35 to 70%. Likewise, innovative designs such as rotating spheres and changing bowl shapes significantly increased the productivity of spherical and hemispherical stills. Likewise, retrofitting a still with vacuum generation technology can significantly increase yields by 50 to 70%. In addition, using nanomaterials, especially nanophase change materials (NPCM), has increased the efficiency of the spherical and tubular stills by 116.5%, producing 7.62 kg/m2 per day. Therefore, the NPCM-equipped model was still the most efficient option among the three designs. [ABSTRACT FROM AUTHOR]

Recent research has investigated in situ process characterization for laser welding and laser-based powder bed fusion of metals (PBF-LB/M) via reflection measurement in laser wavelength. These studies successfully identified the prevailing process regime and the formation of a vapor depression based on in situ integrating sphere data. This approach has great potential to accelerate process development by reducing the required ex situ specimen testing. Unfortunately, the measurement with an integrating sphere does not allow its application as an in-line monitoring system without significantly restricting the process design because the integrating sphere is placed within the gas flow and limits the working area with its small aperture close to the process zone. Therefore, this work investigates directional reflection-based process monitoring in the laser wavelength for laser welding and PBF-LB/M of AISI 316L under insignificant restrictions to the system. For this, the changes in direction and intensity of the reflected laser radiation are monitored for bare plate experiments at various laser powers with photodiodes, which are fiber-coupled to parabolic dish collectors surrounding the working area. These experiments are conducted in a wide working area. It was found that a characteristic change in the reflection direction coincides with the threshold for vapor depression formation, which was previously identified with the integrating sphere. These results show great potential for in-line process monitoring because this novel measuring approach adds directional information to reflection monitoring while decreasing its impact on the process design. [ABSTRACT FROM AUTHOR]

In this paper, we present a groundbreaking approach to enhance the illumination of traffic boards along superhighways, addressing significant challenges associated with conventional lighting systems. Our innovative method revolves around the strategic placement of remote spotlights at the side of the roadway to illuminate traffic signs equipped with retroreflector film (RTRF). The essence of our approach lies in remote illumination, which requires meticulous adjustment of the divergence angle of the spotlights to match the size of the signs and their distance from the projection source. To achieve the desired spotlight configuration, we have developed a hybrid optical system that incorporates a paraboloid reflector and a lens mounted on a bridge holder situated on top of the mirror. Through spot light illumination, we discovered that the initial divergence angle of the RTRF was too narrow. To improve projection angle tolerance, we recommend attaching a light diffuser film onto the surface of the RTRF. The coverage area ratio of the diffuser film can be adjusted to select the desired divergence angle for the reflected light. Our experimental measurements have yielded significant results, showcasing the half-divergent angle of the RTRF ranging from 3° to 7° for different coverage area ratios of the diffuser. In practical terms, with a target luminance of 300 nits at the white word on the traffic board, the power consumption of the spotlight fixture of the roadway was only 40 W, representing over 75% power savings when compared to traditional lighting methods. Consequently, our approach opts to utilize spotlights for illuminating specific traffic boards on superhighways, offering a more efficient and manageable lighting solution that greatly benefits both motorists and road maintenance personnel. [ABSTRACT FROM AUTHOR]

We have developed a terahertz (THz) nonlinear spectrometer at low temperatures (1.5–300 K) and under high magnetic fields (up to 10 T) by combining the laser-driven table-top intense THz source with a superconducting magnet. The strong-field THz pump pulse was generated from LiNbO3 crystal using the tilted-pulse-front technique and tightly focused into the center of the magnet by an off-axis parabolic mirror and a THz lens. The electric fields at the focus can achieve 500 kV/cm with a monocycle waveform and 30 kV/cm with a multicycle waveform at 0.5 THz. The sample was mounted on a low-temperature motorized rotation stage, which enables performing the polarization dependent measurements of the third harmonic generation (THG) intensity without rotating the incident THz pulses. The magnetic field direction can be rotated using a mechanical rotator, allowing for a convenient switch between Faraday and Voigt geometry. We demonstrate the excellent performance of our instrument by conducting THG measurements in the two-band superconductor MgB2 as a function of temperature, sample azimuth angle, as well as in-plane and out-of-plane magnetic fields. The successful combination of the strong field THz source with magnetic fields enables us to study a variety of materials with magnetic-field-dependent properties of interest. [ABSTRACT FROM AUTHOR]

The performance of solar thermal power systems using cavity receivers and parabolic dishes highly depends on the effective absorption of concentrated solar radiation by cavity receivers. Correct measurement of convection losses is challenging due to non-isothermal surface temperatures and unpredictable flow conditions inside the cavity. Correct prediction of radiation losses can help to predict convection losses. Effect of increasing the area ratio of normal cavity using cylinder in cylinder arrangement to increase the surface area for heat transfer, is studied experimentally. The specially designed heaters for model cavity size using nichrome wires sheathed between ceramic sheets were used to apply the thermal load, and the heat transfer rate was observed. Experimental temperatures were used for calculating the radiation heat losses using radiosity network method. Modified cavity surface is divided in parts and radiosity values for each part is calculated by solving simultaneous equation obtained by network method, using Gauss-Seidel method. Finally, the radiation heat loss from each surface is added to get total radiation heat loss. More heat transfer area for cylinder in cylinder arrangement and with the same heat input modified cavity shows higher surface temperatures. Network representation provides a better understanding of radiative interaction between different parts of the cavity. Radiosity network method predicts more accurate results than mean radiation heat loss calculations by calculating actual radiosity values for different parts of cavity. The difference in prediction is high at lower temperatures, emissivity and reduces with increasing temperature and emissivity. Effect of inner cylinder surface temperature was studied with three different cases and found that the radiation heat losses are less affected by inner cylinder surface temperatures. Effect of aspect ratio on radiation heat losses is presented in this work. Experimental results show that proposed cavity receiver design provide double surface area for heat transfer with increased surface temperatures for same heat input and total heat loss. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to investigate the effect of fins inside the absorber tube of parabolic trough collector (PTC). The analysis compares two cases: one without fins and one with four fins inside the absorber tube. The study is divided into two parts. In the first part, meteorological data is used to calculate the temporal numerical values of solar heat flux for the city of Laghouat, Algeria. Solar flux density values for different seasons (A summer, B autumn, C spring, D winter) have been computed, and a ray-tracing method is applied to determine the distribution of thermal flux on the lateral surface of the receiver tube. In the second part, a simulation is performed to model conjugate heat transfer within the receiver tube, with water as the heat transfer fluid. The simulation examines the case where four fins are added inside the absorber tube, along with a secondary reflector. The results for the first case (simple receiver tube) show that the highest fluid temperatures and system efficiency are reached during summer (73°C, 40%), while the lowest values occur in winter (45°C, 32%). Intermediate values are observed in B.autumn and C.spring (58°C, 32%). For the second case ( receiver tube with fins), higher performance is recorded during D. summer, with maximum fluid temperatures of 86.8°C and an efficiency of 49%. The lowest values in D.winter are 50.5°C and 39%, while B.autumn and C.spring show values of 77°C and 48%. Additionally, system performance is enhanced by incorporating fins inside the tube, leading to an improvement ratio of approximately 1.21 to 1.49. [ABSTRACT FROM AUTHOR]

This paper investigates the application of Schlieren flow visualization for detecting leaks in pipelines carrying high-temperature fluids. Two experimental setups were constructed: one with a 25 mm PTFE tube featuring a 2 mm diameter perforation, and another with a 100 mm diameter pipe insulated with an aluminum jacket and featuring a 12 mm leak gap. A single-mirror-off-axis Schlieren system, employing a 150 mm diameter parabolic mirror, was used to visualize the leaks. The temperature of the leaking air varied between 20 and 100 °C, while the ambient temperature was maintained at 14 °C. To quantify the leaks, the coefficient of variation for pixel intensity within the leak region was calculated. Results showed that for the PTFE tube, leaks became detectable when the temperature difference exceeded 34 °C, with the coefficient of variation surpassing 0.1. However, in the insulated pipe, detecting clear leak patterns was challenging. This research demonstrates the potential of Schlieren visualization as a valuable tool in enhancing pipeline leak detection. [ABSTRACT FROM AUTHOR]

We have developed a cryogen-free, low-temperature terahertz scanning tunneling microscope (THz-STM). This system utilizes a continuous-flow cryogen-free cooler to achieve low temperatures of ∼25 K. Meanwhile, an ultra-small ultra-high vacuum chamber results in the reduction of the distance from sample to viewport to only 4 cm. NA = 0.6 can be achieved while placing the entire optical component, including a large parabolic mirror, outside the vacuum chamber. Thus, the convenience of optical coupling is much improved without compromising the performance of STM. Based on this, we introduced THz pulses into the tunnel junction and constructed the THz-STM, achieving atomic-level spatial resolution in THz-driven current imaging and sub-picosecond (sub-ps) time resolution in autocorrelation signals during pump–probe measurements. Experimental data from various representative samples are presented to showcase the performance of the instrument, establishing it as an ideal platform for studying non-equilibrium dynamic processes at nanoscale. [ABSTRACT FROM AUTHOR]

This study investigates the concentration performance of three concentrator types – Fresnel lens, plano-convex lens, and parabolic mirrors in focusing sunlight onto a 1.5 mm diameter plastic optical fiber. The evaluation uses TracePro ray tracing software for simulation and analysis, considering visible light and infrared bands. Results show that parabolic mirrors achieved the highest concentration ratio at 7720 suns, followed by the Fresnel lens at 6400 suns, and the plano-convex lens at 2750 suns for a wavelength of 535 nm, surpassing geometric concentration values of 1202 suns. Efficiency measurements revealed that the Fresnel lens achieved 86% efficiency, the parabolic mirrors reached 97% efficiency, and the plano-convex lens achieved 93% efficiency. Additionally, the parabolic mirror demonstrated potential for creating the smallest concentration spot size due to its ability to focus light on a single point. This study highlights potential applications of sunlight concentrators in enhancing natural lighting in buildings and promoting energy efficiency. The comparative analysis of these concentrators offers insights into their performance characteristics, aiding in the selection and optimization of concentrators for daylighting applications. Moreover, this research supports the concept of green and sustainable energy by demonstrating the potential of solar energy to meet building energy demand and promote daylighting as a means to reduce reliance on conventional energy sources. [ABSTRACT FROM AUTHOR]

The Molonglo Cross was first commissioned in 1965, as a transit radio (408 MHz) interferometer with the largest collecting area in the Southern hemisphere. In 1981, the telescope was redeveloped as an Earth-rotation synthesis interferometer using only the East–West arm (843 MHz), known as the Molonglo Observatory Synthesis Telescope. While the East–West arm was revitalized in the 2010s, the (slightly larger) North–South (NS) arm, which consists of two co-linear paraboloid cylindrical reflectors spanning 2 × 778 m × 12.7 m, had not been used for over 40 yr. Re-fitting this 19 800-m2 collecting area with modern electronics is a cost-effective way of producing a significant survey instrument. The upgrades made to the entire signal chain of the NS arm from the antenna through the transport, digitization, and digital signal processing are described, along with the subsequent performance of the system. The instrument was designed to undertake pulsar timing and searching for dispersed single pulses [e.g. from fast radio bursts (FRBs)]. The upgraded system operated across the 806.25–856.25-MHz frequency range, and had a primary beam that spans 12.7 × 2.5 deg. It had dual linear polarization capability and a lower system temperature and wider bandwidth compared with the East–West system. The digital signal processing was performed on servers with graphics processing units, which enabled low-latency, high-speed data processing, and made use of pipelines built from existing and custom codes. It timed around 70 pulsars per day while running concurrent FRB searches at nearly 100 per cent duty cycle during its operation. [ABSTRACT FROM AUTHOR]

An autoclave is a device for sterilizing medical and surgical tools in hospitals and healthcare centers. The lack of electric power supply in some hospitals and rural health centers, in addition to pollution caused by fossil fuels, reinforces the need to search for other energy sources to operate the autoclave. Solar autoclaves can be utilized as an alternative choice in such circumstances. This work describes the effectiveness of the solar-powered autoclave, which is used for wet sterilization. The device is designed from a parabolic dish reflector covered with mirrors that reflect solar radiation toward the center of a focus for heating a vessel. It was found that the highest value of the average energy efficiency was 19 % and the average exergy efficiency was 2 % at 9:00 am and the lowest value of the average energy efficiency was 1.5% and the average exergy efficiency was 0.4 % at 12:00 noon. The effectiveness was tested against (pseudomonas aeruginosa) bacteria, where the highest values of steam temperatures for sterilization were recorded between 121 °C to 122 °C. It was also found that the sterilization efficiency was 100 % under steam pressure of 1.18 bar for every 30 minutes of the sterilization cycle for the periods 11:00 am to 11:30 am, 11:30 am to 12:00 noon, and 12:00 noon to 12:30 pm). [ABSTRACT FROM AUTHOR]

The current review aimed to identify the recent developments in sustainable steam generation and its applications in food sterilization. Fuel, gas, and coal boilers are the traditional methods for producing steam. Recently, innovative methods of steam generation include electrodes, solar, natural gas, nano-electric, biogas, biomethane boilers, and sustainable steam generation through heat pump (heat pump is an energy-efficient device that transfers heat from one location to another, typically using electricity). The calories in the 100% saturated steam are higher than steam saturation by 95%. The solar parabolic dish system includes biaxial tracking mechanism that ensures increased efficiency and useful energy production due to the increased radiation. Electrode boilers generate steam using electric current, offering simplicity, reliability, and efficiency. Nano-electric boiler boasts a high-power density, minimal carbon emissions, great physical stability, and high-power factor and electric conversion efficiency. The efficiency of natural gas, biogas and biomethane boilers ranges from 94% to 95% with an economizer. The air-source heat pump boiler provides stable system output with high energy efficiency, generating steam at temperatures exceeding 120°C. Water content below 0.01% mass is necessary for steam purity to prevent overheating. The thermal treatment of canned food should reduce bacteria levels by 12 log cycles in low-acid foods to meet safety limits. The container contains 1 spores for Clostridium botulinum for thermal treatment (sterilization) at 121°C. The process involves sterilizing materials at 121°C for 15 min, killing most heat-resistant microorganisms. The innovative steam sterilization methods aim to advance industrial uses that fulfill net-zero emissions and sustainable development goals (SDG). [ABSTRACT FROM AUTHOR]

Copyright of Amazonia Investiga is the property of PRIMMATE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A novel parabolic rigid deployable antenna based on origami was designed; • The optimization framework of parabolic rigid deployable antenna structure was estU:\ES\DTD560\JASR\17318\S5ablished; • Connection nodes and rotating axis were designed to circumvent collision during the process of deploying and folding. This paper introduces a novel approach for optimizing the packing and design of deployable parabolic rigid antenna structures based on origami, tailored to meet specific requirements related to the number of solid-surface blocks and the size of the folded antenna. The study begins by selecting a single-vertex four-crease configuration with one degree of freedom from the origami pattern, guided by mobility analysis, to optimize block arrangement. Subsequently, a planar model is employed to qualitatively examine the impact of geometric parameters on the stowage efficiency of the antenna. Building upon the insights gained from the planar model, an optimization framework for the parabolic rigid deployable antenna structure is established. The objective function of the optimization is the stowage volume, while simultaneously adhering to stiffness, collision, and mobility constraints. The design parameters of the antenna structure are thoroughly analyzed. To mitigate collision risks during folding, design considerations are applied to placement of support nodes, location of rotating axes, and block division, leveraging the optimized parameters. The practicality of the proposed method is successfully demonstrated through the folding of a simulated 3D model and of a physical 3D printed model. These tangible representations show the feasibility of the presented approach, affirming its potential applicability in the optimization and design of deployable parabolic rigid antenna structures. [ABSTRACT FROM AUTHOR]

Concentrated photovoltaic thermal (CPVT) systems involving parabolic reflector have been scrutinized in this article. The purpose of using such a concentrated solar system is achieving higher electrical power and greater thermal productivity. The configuration of cooling system is very significant part of designing such CPVT system, and three configurations were utilized in this numerical modeling: (1) smooth duct (case I); (2) sinusoidal duct (case II); and (3) sinusoidal duct equipped with sinusoidal fins (case III). The utilized testing fluid was a mixture of water and hybrid nanoparticles, and homogeneous formulation was utilized for finding the properties of nanomaterial. Two steps for simulations have been considered: (1) finding the distribution of heat flux involving pure radiation within two-dimensional domains and (2) three-dimensional laminar flow of hybrid nanofluid involving all layers of PV. Active variables of present modeling were: concentration of hybrid additives (ϕ = 0, 0.04), amplitude (a = 1, 2 and 4 cm) and pitch ratio (λ = 0, 4 and 16 mm) of sinusoidal duct; number of fins (NoF = 1, 3); inlet flow rate (Q = 1, 2, 3 L min−1). When sinusoidal duct has been applied in the absence of helical fin, the electrical efficacy elevates about 2.5% with inclusion of hybrid nanomaterial when a = 1 cm and λ = 4 mm. With switching from case I to case II, thermal efficiency augments about 3.5%. In view of overall efficacy, case III has the best performance among various scrutinized configurations. If the third configuration has been utilized, applying more fins makes ηth and ηele increase about 0.5% and 0.8, respectively. Increase in Q in existence of one fin leads to augmentation of PEC about 51.38%. [ABSTRACT FROM AUTHOR]

It is imperative to mitigate the convective heat loss from the receiver to improve the overall efficiency of the parabolic dish concentrator. In this study, the reductions of convective heat loss from the cylindrical‐hemispherical receiver are numerically analyzed and the model was validated by the experimental data from literature. In the first case, the impact of the glass cover on convective heat loss is examined under conditions of both natural and forced convections at various receiver orientations (γ = 0°, 30°, 60°, and 90°). Numerical results clearly demonstrate that the use of a glass cover significantly reduces the intrusion of surrounding air into the receiver cavity which leads to an enhancement of the stagnation zone inside the cavity and, as a consequence, a noticeable reduction in convective heat loss is observed. To perform analysis of the receiver with glass cover under forced convective condition, the wind velocities over the receiver are considered in the range of 1–6 m/s. The maximum reduction of convective heat loss using the glass cover is achieved to be 58.44% with wind velocity of 5 m/s at γ = 60°. In the second case, the influence of air curtain at the receiver aperture under natural convective heat loss conditions is analyzed. The analysis incorporates three variables: receiver orientation (γ = 0°–60°), nozzle width (Lnoz ${L}_{\mathrm{noz}}$ = 0.002–0.004 m), and nozzle outlet velocity (Vnoz ${V}_{\mathrm{noz}}$ = 0.5–3.5 m/s). The results show that the air curtain minimizes the outflow of receiver inside air and results in an improvement in the stagnation zone inside the cavity. The maximum effectiveness of the air curtain is found to be 43.2% at nozzle width of Lnoz ${L}_{\mathrm{noz}}$ = 0.004 m and nozzle velocity of Vnoz ${V}_{\mathrm{noz}}$ = 1.5 m/s at receiver orientation of 60°. It is also noteworthy that the optimal nozzle velocity decreases with the increase of nozzle widths. [ABSTRACT FROM AUTHOR]

The current paper evaluated experimentally an innovative sun tracking concentrated solar still under Egyptian climatic conditions during the summer of 2022. The proposed system consists of a 120-cm-diameter parabolic reflector mirror that tracks the sun using a dual axis tracking system, a cylindrical solar still with a volume of 3.7 L positioned in its focal point, and a concentration ratio of 12.5. The performance of the concentrated solar still was investigated in the context of two critical parameters. First, three feed water salinity (17, 27, 37) ppt samples were evaluated, followed by four percentages of saline water filling ratio (26.5, 39.8, 53.1, 66.3)%. Increasing the salinity of the feed water had no effect on solar still productivity, but increasing the saline water filling ratio did. The daily cumulative productivity of the system was 6 kg/m2 with an optimal filling ratio of 53.1%, a daily efficiency of 42.88%, and an average cost of freshwater production of 0.0489 $/L. The proposed system also had the highest instantaneous efficiency of 61.77% and the highest distilled water productivity rate of 0.941 kg/h m2. [ABSTRACT FROM AUTHOR]

The era following the separation of CMB photons from matter, until the emergence of the first stars and galaxies, is known as the Cosmic Dark Ages. Studying the electromagnetic radiation emitted by neutral hydrogen having the 21 cm rest wavelength is the only way to explore this significant phase in the Universe's history, offering opportunities to investigate essential questions about dark matter physics, the standard cosmological model and inflation. Due to cosmological redshift, this signal is now only observable at frequencies inaccessible from the Earth's surface due to ionospheric absorption and reflection. With the Lunar Crater Radio Telescope (LCRT), we aim to conduct unprecedented measurements of the sky-averaged redshifted signal spectrum in the 4.7–47 MHz band, by deploying a 350 m diameter parabolic reflector mesh inside a lunar crater on the far side of the Moon and suspending a receiver at its focus. This work discusses the feasibility of the LCRT science goals through the development of a science model, with emphasis on post-processing techniques to extract the Dark Ages signal from the galactic foreground dominating the expected raw data. This model can be used to vary critical instrument and mission parameters to understand their effect on the quality of the retrieved signal. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'. [ABSTRACT FROM AUTHOR]

Among solar energy technologies, differences exist in terms of costs, performance, and environmental sustainability. Flatplate solar collectors, solar towers, and parabolic dish systems offer high thermal efficiency and versatility, but they may be more costly and bulky compared to other collector models. This study focused on evaluating the efficiency of a cylindrical parabolic collector (CPC) for the production of domestic hot water in a high Andean region of Peru, using the F-Chart method. Its performance was estimated considering the energy demand for hot water in a single-family home with four occupants, in accordance with national regulations and international recommendations. Additionally, the collector area, water temperature, and incident solar radiation were determined based on meteorological data obtained using the PVsyst software. On the other hand, the F-Chart methodology was employed to find the dimensionless factors X and Y of the CPC collector, which allowed estimating the solar fraction factor and the monthly useful energy that can be provided by the designed CPC system. The results showed that, during months of maximum solar radiation, the CPC is capable of satisfying between 129% and 144% of the energy demand for hot water. This indicates that there is a surplus of usable solar energy in the collector during the summer, while in autumn and winter, the solar contribution balances and slightly exceeds the demand. CPC can significantly contribute to the development of high Andean areas by improving quality of life, reducing costs, and promoting environmental sustainability compared to other available technologies. [ABSTRACT FROM AUTHOR]

In a parabolic dish system, the heat losses from the cavity receiver significantly suppress the system's efficiency and may increase its overall cost. Several existing researches have numerically and experimentally developed the different cavity receiver models by modifying their inclinations, design geometrics, and structure. The conductive loss does not occur much in the cavity receivers compared to the convective loss. So, the analysis of convective loss is more critical in the cavity receivers; however, the accurate prediction of convection loss is quite complex due to the temperature distribution near the cavity. This prime aim of the paper is to comprehensively review the existing literature related to design configurations of cavity receivers and heat loss analysis to set a platform for performance improvement via design modifications. The study emphasizes the effect of geometric parameters like the structure of cavity receivers, shape and sizes, and angle of inclinations with the ground. Structural configurations, especially the hemispherical, cylindrical, conical, and trapezoidal cavity receivers utilized for the solar dish collector (SDC), are investigated between the years 1980 to 2022. A comparison is made based on heat loss models and research outcomes. Besides, the Nusselt correlation model used for predicting heat losses is also carried out in this review by varying the effects such as inclination, aperture ratio, wind effect, etc. This review supports the solar cavity designers for experimentally investigating and simulating a new modified solar cavity receiver with minimization and accurately predicting convective losses. [ABSTRACT FROM AUTHOR]

The goal of this study is to optimize and examine the effect of different rim angles and focus lengths on the performance of a solar parabolic dish. To achieve these goals, a solar parabolic dish concentrator was constructed with different focus point positions and tested under the climatic conditions of the Upper Egypt region in Qena city, with the location of (Latitude: 26.16°, Longitude: 32.71°). The preliminary experimental days started on 18th and lasted on 20th of September 2022, and the tested rim angles were 70°, 80°, and 60°. The results showed that the performance of the proposed solar parabolic dish concentrator was enhanced when the rim angle was between 60° and 70°, otherwise, the performance was regressed when the rim angle was between 70° and 80°. To optimize the rim angle, another available rim angle was selected to increase the performance of the solar dish fixed at 65°, and this angle was tested on 21st of September 2022. The results demonstrated that the thermal efficiency of the solar parabolic dish with rim angle of 65° was higher than that of 70°, 80°, and 60°, and the recorded thermal efficiency reached up to 79.5%, 39.4%, 5.84%, and 28.4%, respectively, under the tested rim angles. [ABSTRACT FROM AUTHOR]

Copyright of Dilemas Contemporáneos: Educación, Política y Valores is the property of Dilemas Contemporaneos: Educacion, Politica y Valores and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The efficiency of the parabolic dish system is significantly impacted by the thermal energy lost from the receiver. Well-established correlations can be used to determine the energy's conduction and radiation modes. However, due to the complex flow behavior near the cavity receiver, estimating the loss of convective heat is difficult. Surprisingly, the majority of studies has solely examined forced convection from the cavity and has not considered the impact of the dish structure. The presence of the dish structure may alter the local wind patterns near the cavity, which may also affect heat loss. Given the importance of an improved thermal model, the behavior of the wind flow must thus be investigated by adding the dish structure. The numerical results obtained in this work confirm that the dish has a significant impact on the flow in the cavity region. Under normal operating conditions, the cavity receiver is protected from the free stream flow by the dish architecture. Because the local flow velocity is relatively low near the receiver, there is a noticeable reduction in heat loss from the device. [ABSTRACT FROM AUTHOR]

This is a brief review of five-year studies of features of nontrivial three-dimensional topological structures of the electromagnetic field—optical strips—formed by vectors characterizing the sizes and orientation of the polarization ellipse of the light field with tracing of change in the orientations of these vectors along closed contours of various shapes, which are linked to lines of polarization singularity or are located immediately near them. The characteristics of polarization strips formed on arbitrarily oriented small circular contours around a single circular polarization singularity line of the electromagnetic field are described. The topology of polarization strips of light scattered by a dielectric sphere and a metallic spheroid with subwavelength sizes when elliptically polarized harmonic plane waves are incident on them is discussed. Optical polarization strips existing in the focal region of a parabolic mirror that tightly focus various laser beams incident on it is described. The topology of polarization ellipse strips in the electromagnetic field of laser radiation propagating in a planar metamaterial is discussed. [ABSTRACT FROM AUTHOR]

A low‐cost W‐band leaky‐wave antenna with two‐dimensional scanning capability is presented. By using the low‐loss transversal long‐slot array structure with a single‐layer parabolic reflector, the antenna realizes a passband from 85 to 102.8 GHz with Voltage Standing Wave Ratio <2. This antenna has a backward radiation direction, which changes with frequency in one dimension, and with the feeding wave front direction in the other dimension. The maximum sidelobe is measured to be −14.2 dB, 5 dB lower compared to the previous‐published longitudinal long‐slot array. A low‐cost, low‐loss, low‐profile design is provided for W‐band 2‐D beam scanning, with backward scanning capability, which is easy to fabricate and could be used for high‐solution sensing and point‐to‐point communications. [ABSTRACT FROM AUTHOR]