Line Focus Research Articles

Sensitivity analysis of a parabolic trough concentrator with linear V‐shape cavity

AbstractIn the present investigation, a solar parabolic trough concentrator (PTC) with a linear cavity was examined by using a developed numerical model. More specifically, a V‐shape cavity receiver was studied in this work as a new and alternative design. The use of a cavity in a PTC is a very promising idea because it leads to high efficiency and to low investment cost. Up today, the emphasis in the use of cavities is given in dish concentrators and so there is a need for investigation of cavities also in linear concentrators. Different dimensional and operational parameters of the PTC with a V‐shape cavity were considered. More specifically, the position, aperture area, and the tube diameter of the V‐shape cavity, solar irradiance, inlet temperature level, and mass flow rate were evaluated based on sensitivity analysis. The results revealed that the highest optical performance was attained when the cavity was placed at the PTC focal line. Moreover, it is found that there is an optimum cavity aperture area to determine the greatest thermal efficiency. For the optical errors of 5, 10, 15, 20, and 35 mrad, the optimum cavity aperture wide was calculated at 5, 5, 6, 7, and 8 cm, respectively, with the tracking error to be 0°. The highest thermal performance has found when the collector operates with low inlet temperature, high flow rate, high solar irradiation level, and small cavity tube diameter.

Performance of a novel single-tubular ammonia-based reactor driven by concentrated solar power

Because of high concentrating ratios of Concentrated Solar Power Technologies (CSP), and maturity of industrial ammonia synthesis process, the high-temperature ammonia thermochemical energy storage based on CSP technology has a promising potential. As a prototype of a tubular ammonia reactor under un-uniform heat flux originating from a sunlight spot or line focusing, it is assumed that catalyst particles packed in it is isotropic, and the heat transfer and mass diffusion in the axial direction of the tube were ignored since the length-diameter aspect ratio of the tube is high. Consequently, employing the local thermal non-equilibrium method, a 3-dimensional model for an ammonia decomposition reaction in porous media was developed with semi-perimeter un-uniform heat flux. For further research, the diameter of catalyst particles, the porosity of packed particles and inflow modes were recognized as important factors. The results show that the particular axial or radial distributions of the porosity significantly affect the reaction characteristics. Especially, the distribution of radial linear reduction of porosity increases the ammonia conversion rate and reduced maximum wall temperature. At the same time, the smaller catalyst particles and the inflow mode of one-side in and one-side out all contribute to improving the performance of the tubular reactor. In general, the following measures can effectively improve the reactor performance: choose a smaller catalyst particle diameter, the porosity of catalyst particles packed decreases linearly along the radial direction from the center of the tube, and the inflow mode in the tube is one-side in and one-side out.

Tightly focusing terahertz wave using gradient-type slotted grating based on spoof surface plasmons.

The d1-d2-d3-d4-d5 gradient-type spoof surface plasmons (SSP) grating was designed and found to exert an obvious effect on electric field localization. Two gradient-shaped planar ports were added to the bottom of this grating to form a gradient-type slotted SSP grating and achieve tight focusing and local electric field enhancement for a terahertz wave. The size of the focal spot was optimized to 0.01λ. The single-gradient-type slotted SSP grating was considered as a unit and arranged in one and two dimensions to generate a longitudinal focal line and square focal spots array. This did not only improve the resolution of terahertz imaging, but also simultaneously scan multiple focal spots to increase the speed of terahertz imaging. This work makes the manipulation of terahertz wave more flexible and efficient which has great potential in terahertz high-resolution near-field scanning imaging.

Comparative performance analysis of parabolic trough solar collector by varying absorber surface

Abstract This work is to convert the solar energy in to useful work because solar energy is a renewable energy source and can be harnessed with relative ease. Parabolic trough collector is a line focus heater and it is tested under different conditions by varying the material of the absorber surface. It is found that PTC with different absorber surface gives varying results from which a optimum surface is to be decided for parabolic trough heater. Hence different materials were used their output values and were recorded in order to calculate efficiency absorption etc and to plot values to determine the best suitable material which gives maximum efficiency. Results were taken from parabolic trough collector for various collector set up it is found that more heat absorption is obtained by using Aluminium sheet.

Wearable Conformal Metasurfaces for Polarization Division Multiplexing

AbstractIn practice, there is a strong requirement for modulating the performance of existing bulk devices without changing their physical geometry. In this study, by attaching a flexible metasurface on a cylindrical lens, a wearable conformal metasurface for terahertz polarization division multiplexing is demonstrated, which could be used in wireless communications, detection, and imaging. The integrated metasurface/lens can achieve the control functions of spot focusing, generation of Bessel beams, and phase holograms, respectively, for crosspolarized waves and line focusing for copolarized waves. A total modulation efficiency of up to 87% is experimentally obtained. Notably, the metasurfaces can be attached on/removed from existing bulk devices multiple times, without reducing the performances of both metasurface and conventional devices. As the flexible samples are fabricated using the cost‐effective standard flexible printed circuit technique, a multilayer conformal metasurface can be easily obtained for an efficient control. Furthermore, the same bulk device can be integrated with different flexible metasurfaces for various controls. Thus, the proposed metasurface can provide a promising flexible platform for various integrated applications and contribute to the development of wearable functional devices.

Femtosecond laser fabrication of LIPSS-based waveplates on metallic surfaces

A fast and reliable method for the fabrication of polarization modifying devices using femtosecond laser is reported. A setup based on line focusing is used for the generation of LIPSS on stainless steel, processing at different speeds between 0.8 and 2.4 mm/s with constant energy per pulse of 1.4 mJ. SEM and AFM characterizations of the LIPSS show a progressive increase in period as the processing speed increases, while height remains approximately constant in the studied range. Optical characterization of the devices shows an induced change in the polarization of the reflected beam that varies with the processing speed, which allows a controlled fabrication of these devices.

Levers of Control for Supply Chain Sustainability: Control and Governance Mechanisms in a Cross-Boundary Setting

The rise of global supply chains as well as attention to the Triple Bottom Line provides organizations with new conditions and strategy paradoxes to be dealt with when it comes to sustainability in supply chain management. This study of a large multinational organization with a strong Triple Bottom Line focus provides a comprehensive analysis of the use of control and governance mechanisms in supply chain context. Through the Levers of Control framework, the application of these mechanisms both internally and across organizational boundaries is shown. The interplay between levers helps in dealing with the in itself paradoxical nature of Triple Bottom Line goalsetting. The results show that the “softer” elements of the Triple Bottom Line, i.e., People and Planet, are approached with the lever associated with the beliefs system, which in turn enforces the boundary and interactive control systems. Ultimately, applying the Levers of Control in supply chain context might contribute to pursuing a holistic approach of sustainable supply chain management.

Theoretical model of caustics method for the interfacial cracks

As a non-contact optical experimental method, caustic method is commonly employed in measuring stress intensity factor at the crack tips of different materials. Caustics theory is commonly used for solving stress intensity factor at crack tips in homogeneous isotropic materials, but it lacks the required accuracy for solving stress intensity factor in interfacial cracks in dissimilar materials. In this paper, we have deduced the theoretical equation of stress intensity factor at interfacial crack tips the orthotropic bi-materials and evaluated the effects of different crack propagation speeds, orthotropic bi-materials and other parameters on the initial curves of focal line and the shape of caustics. In addition, dynamic caustic experiments on composite/epoxy bi-materials under low velocity-impact loadings were performed and the evolution of dynamic interfacial cracks was captured by high-speed cameras which showed good agreements with theoretical results. Research results confirmed the usefulness of the application of caustic method in dissimilar isotropic and orthotropic materials, isotropic-orthotropic bi-materials and homogeneous isotropic and orthotropic materials under subsonic crack propagation velocities.

Metalens With Artificial Focus Pattern

Metalens as one of the most popular applications of emmerging optical metasurfaces has raised widspread interest recently. With nano structures fully controlling phase, polarization and transmission, metalens has achieved comparable performance of commercial objective lenses. While recent studies seeking for the accomplishment of traditional focusing behaviors through metalens are successful, inthis work, we have discovered that instead of focusing light to a point, metasurface further enables shaping the focus into a flexibly designed pattern, with more promises and potentials. New mechanism and generalizations of conventional point-focused metalens guiding principles have been proposed with metalens concentrating light to artificial focus pattern. As proving examples, we have demonstrated the engineering of metalens with artificial focus pattern by creating line and ring-shaped focus as 'drawing tools'. The metalens with 'U' and 'M' shaped focus are characterized for the proof of concepts. These metalens are fabricated through a single layer of silicon-based material through CMOS compatible nano fabrication process. The mechanism to generate artificial focus pattern can be applied to a plethora of future on-chip optical devices with applications ranging from beam engineering to next generation nano lithography.

Investigation on novel design of solar still coupled with two axis solar tracking system

This work deals with the design, fabrication, and experimentation of an innovative system of solar distillation that uses the concentration effect to increase the heat energy received by the still. So, a modified basin of conventional solar still (CSS) was integrated with a parabolic trough concentrator (PTC) and mounted on an iron structure to form the PTC-CSS. This structure allows the CSS to change continuously its orientation and track the sun from the sunrise to sunset. Also, it allows the permanent meeting of the PTC focal line with the basin absorber. Therefore, the reflected solar rays are directly and continuously concentrated on the water to be distilled with efficiency, and the CSS receives, throughout the day, the maximum solar radiation from two sides i.e. bottom surface and top glass cover. The presented system has allowed the assessment of the continuous direct concentration effect on the absorber of a self-tractable conventional solar still. It was found that the system can ensure a quasi-constant high temperature of water exceeding 80 °C from a low ambient temperature (19–26 °C). However, the heat and mass transfer processes that occur inside the still lead to increase considerably the temperature of the glass cover which affects negatively the productivity. Two main experiments were conducted: the first one was to assess the basic performances of the desalination system, whereas the second was performed to give more details about the high temperature of the glass cover revealed during the first experiment. The yield of the presented solar still was about 3.76 l/day. Compared to a compound parabolic concentrator assisted tubular solar still, the yield was slightly increased while the cost investment was reduced by 7%. Also, since the PTC-CSS presents the potential of high level of evaporation, further research focusing on enhancement of the condensation process is expected to give more impressive achievements.

Atmospheric water harvesting from low humid regions using tubular solar still powered by a parabolic concentrator system

The present study proposed a new system of atmospheric water harvesting from extreme low humid regions under climatic conditions of Hail city (27.64 oN, 41.75 oE), Saudi Arabia. The concept of the proposed system was to activate the tubular solar still by a parabolic solar concentrator. This concept would increase TSS ability to evaporate water from strong desiccant of calcium chloride under extreme low humid conditions. The TSS was opened and exposed to atmospheric air during night hours starting the absorption process. At the beginning of the sunrise, the TSS was closed and placed at the focal line of the parabolic concentrator starting the regeneration process. The proposed system was able to produce 0.51 L/kg of calcium chloride. The system thermal efficiency and water production cost were 24.61% and $0.15 respectively. The proposed device increased the productivity and the efficiency of the TSS by 292.4% and 82.3%, while reduced the water production cost by 25%. The proposed system was compact, small and portable that could be operated easily in a desert, remote and isolated areas without any need for water resource or infrastructure. The proposed new system could be lifesaving in urgent situations especially in the desert areas.

Effect of metallic reflectors and surface characteristics on the productivity rate of water desalination systems

The objective of this research is to determine the best metallic reflector for parabolic trough solar collectors of water desalination units. A group of materials have been selected and tested for their reflectivity. These materials were; aluminium foil of thicknesses 6 μm and 86 μm, and sheets of 1 mm thickness made of aluminium, galvanized steel, copper and stainless steel. An experimental setup has been constructed to examine the performance of the parabolic trough as a function of the reflecting surface. The experimental setup consists of an artificial sun, parabolic trough solar collector with an evacuated tube located in the focal point of the trough and a desalination unit. The influence of the different reflectors, in terms of reflectivity, on the performance of the collector and the desalination unit were examined. It has been found that both the material type and surface roughness affect the reflectivity of the surface, and that the highest desalination rate is obtained by the aluminium foil of thickness 6 μm that has the lowest surface roughness Ra 0.04 μm and highest reflectivity 93%. The heat energy output from a parabolic trough using an evacuated tube at its focal line is linearly proportional to its reflectivity.

Sensitivity analysis of parabolic trough concentrator using rectangular cavity receiver

The objective of this work is the investigation of a parabolic trough concentrator (PTC) with a linear cubical cavity receiver which operates with thermal oil as the working fluid. The solar collector is investigated in order to achieve maximum thermal efficiency. The PTC is investigated optically in Sol Trace software, while the thermal modeling is conducted by a code in Maple software. The developed model is validated with experimental data from the literature. Finally, a good agreement has been found between the measured thermal efficiency and the calculated thermal efficiency based on the presented model. Different geometrical dimensions of the cavity receiver were investigated based on sensitivity analysis including cavity position, cavity aperture, cavity height and cavity tube diameter. Also, the system is examined for different operating conditions. According to the results, the lower tracking and optical errors lead to higher optical performance. The best cavity depth is equal to the cavity aperture width. It was found that the higher concentrator aperture increases the absorbed energy. Moreover, it is found that the cavity has to be located in the focal line of the parabola. The highest absorbed heat and thermal efficiency of the solar system calculated was equal to 618.09 W, and 77.26% respectively for the cavity tube diameter of 5 mm.

Performance analysis of parabolic trough solar collector by varying the absorber surface

ABSTRACT In this paper, an attempt has been made to analyse the performance of parabolic trough solar collector (PTSC) by varying the absorber surface. This project intent is to convert the solar energy into a useful work because solar energy is renewable one. PTSC is a line focus heater and it is tested under different conditions by varying the absorber surface. It is found that the PTSC with different absorber surface gives a varying result from which an optimum surface is suggested for parabolic trough heater. The experiment was done with the use of aluminium sheet, aluminium foil and mirror sticker parabolic trough. Results were taken from PTSC for various collector set-up; it is found that more heat absorption is obtained by an aluminium sheet.

Thermal Efficiency Evaluation of a Solar Thermal Steam Generating System Using Thermosiphon Technique with Parabolic Trough Collector

Parabolic trough solar collectors are the most widely used concentrators for solar thermal applications in the world. This is because very high temperatures of 150°C to 350°C can be attained with its use without any noticeable degradation in the performance of the collector. In this work, a parabolic trough collector (PTC) was designed using simple parabolic equations and constructed with locally sourced materials. The developed PTC was used to converge direct solar radiation to a heat receiver (a copper pipe enclosed in an evacuated glass tube) placed at the focal line of the trough to heat up the water in the pipe to steam. Natural circulation (thermosiphon) was employed to drive the water from the heat source to the heat sink (tank) with the difference in density as the driving force of the system. Temperature sensors were installed at different points of the solar thermal system to experimentally investigate temperature distribution within the system, hence thermal performance. A pressure sensor was also installed in the tank to measure the pressure within the system. The results obtained shows that the solar thermal system generated low-mid temperature steam of up to 105°C at a pressure of approximately 120 kPa on a day when the global solar radiation intensity attained a value of 1109.5 W/m2. A thermosiphon mass flow rate of up to 0.042 kg/s was also recorded through a constant orifice of 12 mm diameter. The instantaneous efficiency of the receiver reached 46.48%.

Ku-Band Dual Linear-Polarized 1-D Beam Steering Antenna Using Parabolic-Cylindrical Reflector Fed by a Phased Array Antenna

We propose a 1D beam steering high gain hybrid reflector-phased array antenna system for enhanced data rate wireless communication at Ku -band (12 - 14 GHz). The proposed hybrid antenna system consists of a ${D}$ = 50 cm offset parabolic-cylindrical reflector with ${f}/{D} = 0.4$ fed by an $8\times4$ dual linear-polarized stacked patch phased array antenna placed along the focal line of the reflector. The parabolic-cylindrical reflector has the property of a wide-angle beam steering along the cylindrical axis as compared to a conventional parabolic reflector. A complete implementation of the dual linear-polarized phased array antenna with the silicon RFIC chipset based beamforming network and integrated with aluminum offset parabolic-cylindrical reflector is reported. Cavity model and physical optics approximations are used to analyze the radiation characteristics of the phased array and the induced currents on the parabolic-cylindrical reflector surface, respectively. Furthermore, the multilevel fast multipole method (MLFMM) is used along with the method of moments (MoM) in TICRA GRASP for a comprehensive analysis of the proposed hybrid reflector system. The peak directivity of the reflector pattern is around 27 dBi for both the X-polarization and Y-polarization, and a beam scanning of ±30° is achieved along the cylindrical axis of the reflector for 3 dB reduction in the gain. The analytical and computed results of the proposed hybrid reflector-phased array antenna system are experimentally verified.

Implications of Poverty on Children Readiness to Learn

In this current era education is much needed one to survive in this world. Lots of implications are there to affect the learning of children. Due to poverty people are not able to fulfil even their basic needs. The people below poverty line focus only for fulfilling their daily needs rather than concentrating on their children’s education. Since the children do not get the required materials and facilities for studythey lose interest for study. Hence this leads to dropout of students from school. During this time it is necessary to know the reasons as well as the readiness of children to study. Therefore the researcher is making an attempt to analyze through this study the researcher is making an attempt analyze the implications of poverty on children readiness to learn. For this study purpose the researcher has taken into consideration the Madurai slum area. Interview schedule is used for the data collection and around thirty samples were taken for this purpose. Through this study the researcher is trying to analyze the causes of situation which create more of dropout among the children social demographic details, implications of poverty on children readiness to learn, and what is their need to overcome. The researcher has also come up with suitable suggestion for decreasing the dropout rate of schoolchildren

Fiber-based daylighting system using trough collector for uniform illumination

A lot of research attention has been given to collect sunlight through solar concentrators for indoor illumination. Traditional, parabolic trough as a line focus with single array of fibers had mechanical design and installation issues. Here, a novel daylighting system is proposed to transmit maximum light into the optical fibers using parabolic trough as the primary collector and nonimaging reflector as the secondary reflector. The proposed system increases light levels, improves installations difficulties, and maintains long-term reliability. All modules are designed and verified through raytracing simulation for calculating the efficiency and achieving the required light-levels. The proposed trough-based design inserts maximum light into the fiber bundle, which is placed at the center of the trough. Further, the fiber-coupled bi-layer prismatic optical diffuser provides relatively high uniform illuminance distribution. Simulation results have shown that the light concentration of 285, an optical efficiency of 42%, and an acceptance angle of ±1.1° are achieved that are better than that of previous trough-based daylighting system.

Design and Analysis of Parabolic Trough Solar Water Heating System

Renewable energy technology is one of the prospective sources which can meet the energy demand and can contribute to achieve sustainable development goals. Concentrated collectors are widely used in solar thermal power generation and water heating system also. It is very popular due to its high thermal efficiency, simple construction requirements and low manufacturing cost. This paper is concerned with an experimental study of parabolic trough collector for water heating technology. It focuses on the performance of concentrating solar collector by changing the reflector materials (aluminum sheet, aluminum foil and mirror film). In Bangladesh, it is possible to use low cost solar concentrating technologies for domestic as well as industrial process heat applications. The line focusing parabolic trough collectors have been designed, developed and evaluated its performance by collecting solar radiation, inlet and outlet water temperature, flow rate, efficiency etc.

Multi-line fluorescence scanning microscope for multi-focal imaging with unlimited field of view.

Confocal scanning microscopy is the de facto standard modality for fluorescence imaging. Point scanning, however, leads to a limited throughput and makes the technique unsuitable for fast multi-focal scanning over large areas. We propose an architecture for multi-focal fluorescence imaging that is scalable to large area imaging. The design is based on the concept of line scanning with continuous 'push broom' scanning. Instead of a line sensor, we use an area sensor that is tilted with respect to the optical axis to acquire image data from multiple depths inside the sample simultaneously. A multi-line illumination where the lines span a plane conjugate to the tilted sensor is created by means of a diffractive optics design, implemented on a spatial light modulator. In particular, we describe a design that uses higher order astigmatism to generate focal lines of substantially constant peak intensity along the lines. The proposed method is suitable for fast 3D image acquisition with unlimited field of view, it requires no moving components except for the sample scanning stage, and provides intrinsic alignment of the simultaneously scanned focal slices. As proof of concept, we have scanned 9 focal slices simultaneously over an area of 36 mm2 at 0.29 µm pixel size in object space. The projected ultimate throughput that can be realized with the proposed architecture is in excess of 100 Mpixel/s.