Parabolic Reflector Research Articles

Enhanced‐Resolution Learning‐Based Direction of Arrival Estimation by Programmable Metasurface

AbstractDue to its growing importance and wide range of applications, direction‐of‐arrival (DOA) estimation has become a major research topic, particularly in the field of communication systems. While traditional DOA estimation methods rely on antenna arrays and complex algorithms, recent progress achieved in the design and implementation of metasurfaces has proved their effectiveness as promising alternatives. This study presents a distinct approach for DOA estimation that combines the use of a programmable metasurface with deep learning. The programmable metasurface together with a radio‐frequency power detector placed at the focal point, acts as a parabolic reflector antenna with an adjustable pointing direction, which scans the azimuth plane in 5° increments to receive the power level of incoming signals. The collected data is then fed into a pre‐trained multilayer neural network to enable DOA estimation with a resolution of lower than 1° without requiring fine‐tuning of the scanning procedure. This approach ensures accurate and fast estimations, paving the way for advanced solutions in detection and localization for various applications.

Performance Analysis of a Renewable‐Powered Multi‐Gas Floating Storage and Regasification Facility for Ammonia Vessels With Reconversion to Hydrogen

ABSTRACTNatural gas and renewable energy carriers play critical roles in the energy supply chain due to rising energy consumption demands and a significant shift toward cleaner energy. However, the requirement to liquefy and regasify liquefied natural gas (LNG) and renewable energy carriers for transportation makes the entire process expensive and challenging. Hence, a floating storage and regasification unit (FSRU) plant provides a solution to the aforementioned problems with the additional benefit of being more affordable, time‐efficient, and having less land footprint requirement than the conventional onshore facility. The proposed integrated FSRU in this study, is powered by renewable energy, including solar and ocean thermal energy. The subsystems of integrated FSRU consist of parabolic dish collectors (PDC), Rankine cycle, organic Rankine cycle (ORC), multi‐stage flashing (MSF) desalination unit, decomposition, reliquefication, and regasification plants, which provide valuable commodities such as freshwater, electricity, hydrogen, and heating. It can also cater to standard multi‐gas harboring vessels for storage and regasification of sustainable energy carriers. The study assesses the performance of the proposed system thermodynamically by analyzing mass, energy, entropy, and exergy balance equations using the engineering equation solver (EES) software. Furthermore, parametric studies were conducted to understand the interlinkage among various variables. The analytical results show that the proposed system is able to produce 1.82 MW of electricity, 2056 kg/day of fresh water, and 338.3 kg/day of hydrogen, achieving an overall system energy efficiency of 32.7% and exergy efficiency of 79.3%. This approach aims to foster energy diversification, enhance energy security, and support the transition toward sustainable energy systems, as well as further the advancement of maritime transport systems.

The development of a low-temperature terahertz scanning tunneling microscope based on a cryogen-free scheme.

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 ∼25K. Meanwhile, an ultra-small ultra-high vacuum chamber results in the reduction of the distance from sample to viewport to only 4cm. 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.

Optical design and analysis of a high-speed triple galvanometer laser 3D scanning system

In this paper, a triple galvanometer laser three-dimensions (3D) scanning system (TGLSS) was proposed. The system consisted of three galvanometers and two parabolic mirrors, with rapid movement of the laser focus in 3D space by rotations of the three galvanometers. The optical principle of the TGLSS was analyzed, and the method of designing TGLSS by geometrical optics and Abbe’s sine condition was given in detail. Scanning range and focusing quality were analyzed by optical simulations. An experiment was carried out to verify the feasibility of TGLSS. The implications of TGLSS for reflective dynamic focusing device (RDFD)-based laser system and their impact on technologically relevant applications were discussed. The great potential for enhancing the speed of advanced laser processing in 3D space was offered by TGLSS.

Multi-Objective optimal scheduling of energy Hubs, integrating different solar generation technologies considering uncertainty

For a few decades, operators of energy systems have sought to achieve appropriate frameworks due to energy crises and rapid growth in energy requirements. In this regard, this study presents a multi-objective optimization model for an energy hub (EH) designed to manage a diverse energy portfolio. The EH receives electricity, natural gas, hydrogen, seawater, and solar energy as inputs, aiming to satisfy electricity, heating, and freshwater demands at the output port while considering a limited available area. The model incorporates the selection of the optimal solar energy technology (photovoltaics, parabolic dish, or parabolic trough collector) through a comprehensive evaluation encompassing technical, economic, and environmental aspects. To achieve optimal scheduling of the EH’s production units, the model factors in forecasts of solar energy availability alongside electrical, heat, and water load demands. The evaluation of the EH’s performance is conducted through a multi-objective framework considering social welfare, CO2 emissions, voltage stability margin (VSM), a newly proposed simplified fast temperature stability index (SFTSI), and a similarly novel simplified fast pressure stability index (SFPSI). The optimization problem is formulated within a MATLAB environment and solved using a multi-objective Archimedes optimization algorithm across five distinct case studies, each characterized by a varying designated area for solar energy generation. The effectiveness of the proposed model and optimization technique is validated through test systems, with the obtained results demonstrating significant improvements compared to a baseline scenario. These improvements include a 36.18% reduction in CO2 emissions, a 14.22% increase in total social welfare, and reductions in the average values of VSM, SFTSI, and SFPSI when incorporating all solar energy technologies.

Heat transfer analysis of solar distillation system by incorporating nano‐enhanced PCM as thermal energy‐storage system

AbstractThe 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.

Analysis of the thermodynamic performance of the SOFC-GT system integrated solar energy based on reverse Brayton cycle

Efficient power generation systems are an essential way to reduce carbon emissions. To avoid the complex effects of high-pressure conditions on the solid oxide fuel cell (SOFC) and gas turbine (GT) hybrid systems, while further improving energy efficiency. A SOFC-GT hybrid system based on the reverse Brayton cycle (RBC) is proposed, in which the SOFC operates at near atmospheric pressure conditions and GT expands below atmospheric pressure. Solar energy is integrated to further enhance system performance. Rigorous assessments of the novel system and the pressurized system are conducted utilizing energy, exergy and economic analysis. The sensitivity analysis of environmental parameters on the novel system's performance is performed. The results show that the novel system generates power and efficiency better than the conventional system when the GT compression ratio is 3 and 6, respectively. The power generation and exergy efficiency of the novel system at the design point is 60.47 % and 58.57 %, respectively. The largest exergy destruction occurred in the SOFC. The lowest exergy efficient components are the parabolic dish collector (PDC) and heat exchanger 2. The novel system is more cost-effective due to the higher lifetime of the SOFC, with the levelized cost of energy (LCOE) is 0.1418 $/kWh.

Performance analysis of an SPD integrated with a stepped pyramid solar still: experimental study

AbstractWater scarcity poses a major challenge for the next generation. Additionally, increasing agricultural and industrial activities are creating an unprecedented demand for freshwater supplies throughout Egypt. The Nile River serves as Egypt’s primary water source, accounting for 69.4% of the total water resources. Moreover, Egypt's annual share of water has decreased to approximately 500 m3 per person because of the completion of the Renaissance dam in Ethiopia and the rapid increase in population growth. Solar distillation has been presented as a long-term and promising method for producing edible drinkable water. The present research goal is to increase the daily freshwater output from a stepped pyramid solar still (SPSS) by coupling with a solar parabolic dish (SPD). The proposed system consists of a conventional pyramid solar still (CPSS) and a modified pyramid solar still (MPSS). The main components of an MPSS include an SPSS, a PV panel, an SPD with a spiral coil, a circulating pump, and an Arduino Mega Unit. The developed system was designed, fabricated, and verified from July to August 2023 at the Faculty Engineering, South Valley University. The results of the experiments indicated that the daily productivity of freshwater from MPSS was greater than that from CPSS and reached 6038 and 2612 mL/day, respectively, with an increase in the daily yield of 131%. The peak energy efficiency is 56% for the MPSS and 24% for the CPSS. The peak exergy efficiency is 4.26% for the MPSS and 3.79% for the CPSS. Additionally, the cost analysis of the suggested system revealed that the estimated cost per liter of the proposed system is 0.01635 USD/L.

Generation of extremely strong accelerating electric field by focusing radially polarized THz pulses with a paraboloid ring

Efficient acceleration of electrically charged particles by focused electromagnetic pulses requires a strong accelerating electric field as well as a sufficiently large interaction region. Single-cycle terahertz pulses are promising candidates for such applications due to their advantageous wavelength and available peak electric field at the MV/cm level. We propose and characterize a focusing optics for a possible electron vacuum accelerator. This consists of a reflaxicon for beam shaping and a ring-like segment of an on-axis parabolic mirror for tight focusing of the radially polarized THz pulse in order to reach a strong accelerating electric field. The electric field distribution in the focal region was determined by the Stratton–Chu vector diffraction method. Semi-analytical and purely analytical formulae were also derived, simplifying the computation procedure. By focusing radially polarized single-cycle terahertz pulses with 3mJ pulse energy, calculations predict accelerating electric field component in the order of 100MV/cm, well suitable for particle acceleration.

Solar-driven self-sustaining remediation of petroleum-contaminated soil

Petroleum-contaminated soil poses an environmental risk and is costly to remediate. Self-sustaining Treatment for Active Remediation (STAR) is an emerging remediation technique that consists of igniting and propagating a smoldering front through a volume of contaminated soil. While effective, the electrical energy demand required to initiate smoldering can be cost-prohibitive in locations without robust electrical infrastructure. To address this, we investigated the viability of a novel concentrated solar power process as a low-carbon alternative to electrically driven heating for STAR. The solar-driven system uses parabolic reflectors to focus solar energy, then directs it through fiber optic bundles to flexibly transmit it to a soil column. This process is demonstrated on ∼ 750 mL samples of petroleum-contaminated soil and detectable hydrocarbons were reduced in each case. Research evaluated several parameters of interest for effective treatment including thermal receiver material and distance between solar output and thermal receiver. Temperature was measured throughout treatment and typically exceeds 400 °C prior to ignition. Steel and quartz thermal receivers show effective temperature distribution, initiating smoldering, reducing detectable hydrocarbons and maintaining durability. The results indicate that concentrated solar power can efficiently ignite smoldering remediation, showing promise as a low-carbon alternative to current methods.

Development of a sunlight adjustable parabolic trough reactor for 24-hour efficient photocatalytic wastewater treatment

Solar energy is the ideal energy source for activating photocatalysis. However, due to the solar motion, achieving 24-hour solar-powered efficient photocatalytic reactions remains a challenge. In this study, a Sunlight Adjustable Parabolic Trough Reactor (SA-PTR) integrated with flexible parabolic mirror and solar panel was developed. During the daytime, flexible parabolic mirror could be rolled up under sunny condition or expanded under cloudy condition, thus providing optimal light irradiance (1500 W·m−2) and temperature (rises yet below 55 ℃) for photocatalysis. Additionally, the solar panel behind the flexible parabolic mirror could generate solar-electricity. At night, the stored solar-electricity could meet 100 % power demands of UV lamp, enabling a 24-hour solar-powered photocatalytic process. Compared with traditional parabolic trough reactor and inclined plate collector, SA-PTR exhibited higher treatment efficiency against carcinogenic organic dyes (Rhodamine B, Methylene Blue, Methyl Orange), antibiotic (Tetracycline) and pathogenic bacteria (Escherichia coli) during day and night. Moreover, SA-PTR exhibited superior global deployability, economic advantage, safety and lifetime. Therefore, SA-PTR, as a novel solar controllable 24-hour operational photoreactor, is promising to be employed in real wastewater treatment plant.

Theoretical analysis of upward-heating multiple-effect diffusion solar still with parabolic dish concentrator

Upward-heating multiple-effect diffusion solar still (UHMEDS) coupled with a parabolic dish concentrator (PDC) was proposed and analyzed theoretically. UHMEDS has cover glass, several partitions and preheating cover, and wicks are placed on the upper surfaces of partitions and preheating cover. Saline water preheated on the preheating cover flows down the partitions by gravitational force. The lowermost partition of UHMEDS was heated by solar energy collected by PDC. The basic behavior of UHMEDS at Fukuoka, Japan was analyzed theoretically by modeling heat and mass transfer in the still. The theoretical results show that PDC can collect the sunrays to the lowermost partition of UHMEDS effectively, and the overall daily productivity of the still was predicted to be about 18.5, 24.5 and 10.4 kg/m2day on spring equinox, summer and winter solstice days, respectively, which values are almost equivalent to those of other types of multiple-effect diffusion solar still.

Non-contact measurement of firmness properties of fruits and vegetables using a parabolic-reflector airborne ultrasonic transducer and laser Doppler velocimeter

The requirement for high-quality fruits and vegetables have been increased. The sorting and grading of them in a non-contact way is important, and firmness is an important criterion. In this study, we developed a non-contact measurement system for the firmness of fruits and vegetables by using airborne ultrasonic waves and a parabolic reflector. Focused airborne ultrasound produced vibration on the surfaces of samples and the vibrations were detected by a laser Doppler velocimeter to characterize the elastic properties. First, we designed and fabricated an offset-type parabolic reflector. Then, the elastic parameters (maximum displacements, center frequencies, and damping factors) were determined based on the Kelvin⎯Voigt model. Finally, individual differences in the elastic properties of twelve kinds of samples and temporal changes in the maturity state and elastic properties of three kinds of samples were observed. From the results, we confirm the developed system could be potentially used as an evaluation system for the firmness of fruits and vegetables.

Optical analysis and design of a novel solar beam down concentrator for indoor cooking

This investigation provides the design and optical analysis of an innovative solar beam-down configuration, which can be a promising passive solution for indoor solar-based cooking, offering an eco-friendly and sustainable approach. The system uses a beam-down parabolic dish concentrator to concentrate the solar radiation onto a ground-mounted receiver module, which has a secondary optical module consisting of a secondary reflector-light pipe system. The receiver module is a well-insulated tank consisting of a receiver in contact with a primary heat transfer fluid. The thermal energy stored in the receiver module is transported via a secondary heat transfer fluid to and from the cooktop via a tube-in-tube arrangement, which induces a thermosyphon effect. A multi-variable optical analysis through an efficient ray tracing methodology has been adopted to identify optimal design values of optical components such as parabolic dish concentrators, secondary reflectors, and light pipe-receiver assemblies. The optimal optical design parameters and their corresponding ray trace analysis results are elaborated. It was found that the designed beam-down parabolic dish concentrator system provides an ideal thermal energy of 10.3 kWh per day at an average DNI of 650 W/m2. Further, this investigation provides a design for a beam-down parabolic dish concentrating system that may be used for efficient and sustainable solar energy solutions.

Experimental investigations for enhancing the performance of hemispherical cavity receivers using additively manufactured heat exchangers

ABSTRACT This research explores a pioneering approach in cavity-type solar parabolic dish collector technology (SPDCT) by introducing a novel, additive-manufactured thermally conductive polymer composite heat exchanger over a modified hemispherical cavity receiver for heat recovery applications. This manuscript investigates the performance of innovative configuration of SPDC for Wardha (442001), Maharashtra State (027), INDIA, 20.75° N, 78.65° E, modifying the traditional setup by employing copper coil with different arrangements. The unique aspect of this research lies in the implementation of a hemispherical cavity receiver with preheating water arrangement by installing a thermally conductive polymer composite (TCPC) heat exchanger developed with compositions TPU/MWCNT/GNP of 93/3.5/3.5 by wt.% using an additive manufacturing technique, a strategy not previously explored in the existing literature. A computational study (steady state thermal analysis) conducted using ANSYS Student Version R2023 revealed substantial heat availability over the receiver’s top exterior, forming the basis for the experimental tests. Under different test conditions, the highest thermal efficiency improvement reached to 10.91%. This paper contributes novel ideas to the field, emphasizing the potential of additive-manufactured thermally conductive polymer heat exchangers to increase the performance of solar parabolic dish collector systems.

Energy-efficient production of sustainable industrial process heat with a parabolic dish-conical cavity solar collector

Industrial decarbonization in response to global carbon neutrality requires vast process heat to be supplied in a low-carbon manner. Solar energy is regarded as one of the most promising alternatives to fossil fuel applied for heat-driven industrial processes, however, lack of effective approaches to improve the solar-thermal conversion efficiency is a longstanding issue. Here, we propose an efficient approach to produce industrial process heat based on a novel concentrated solar collector, mainly consisting of a parabolic dish concentrator and a conical cavity receiver. Results showed that the collector was competent to supply the process heat meeting various low-temperature industrial occasions, and there was an optimum flow rate to achieve a trade-off between the outlet temperature of working fluid and thermal efficiency of the solar collector. The thermal efficiency of the proposed solar collector was 2.7%–27.5% higher than that of most other existing collectors used for production of low-temperature process heat, and such a superior solar-thermal conversion efficiency was a consequence of the reduction in energy losses between the solar receiver and surroundings as confirmed by the comprehensive energy analysis performed in this study.

On-Sun Alignment of a Concentrated Solar Parabolic Dish Located in Abu Dhabi, UAE

Improper alignment is one of the key parameters that affect the performance of a concentrated solar parabolic dish (SPD). The receiver must have a flux distribution that is as uniform as feasible for an SPD to operate at its optimum performance. The aim of this research is to align a SPD from ZED Solar [1], which is recently installed at Khalifa University's Masdar Institute Solar Platform in Abu Dhabi, United Arab Emirates. This dish's future application involves integration with a photo-electrochemical hydrogen production reactor, which demands a multi-aimpoint alignment approach for optimal performance. To facilitate this alignment, the sunspots of all facets are initially aligned within a 200 mm diameter circle around the focal point using the on-sun alignment method. During the alignment, the dish was placed in sun-tracking mode, with all facets covered except the one being aligned. The reflection of the facet on the target was observed using a camera. The facet was adjusted until the aimpoint was oriented in the optimal position. The average time to align one facet, including cleaning, loosening the front nuts, and replacing the covers, was found to be around 15 minutes. The complexity of the bolt mounts, rust on the bolts, and the use of a manlift contributed to the prolonged alignment process. Despite these challenges, the on-sun alignment method proved to be an accurate way of aligning the facets of a concentrated SPD.

Design and kinematics analysis of a parabolic cylinder deployment mechanism with modular over-constrained triangular pyramid

Space missions require novel mechanisms that can have compact form in complex space environments. This study proposes a modular triangular pyramid parabolic cylinder deployment mechanism. The modular deployable unit contains an over-constrained triangular pyramid deployable mechanism and a symmetrical trapezoidal Bricard linkage that drives the longitudinal and transverse motions of the mechanism. A cable net is added between two symmetrical linkages to form a parabolic cylindrical reflector and is analyzed by the force density method. The Denavit-Hartenberg (D-H) coordinate method is used to analyze the kinematic characteristics. Based on the analytical solution for the angular displacement, the degrees of freedom of the mechanism are derived from screw theory. Subsequently, the angular velocity and acceleration of the joint points are obtained. Finally, kinematic models of the modular triangular pyramid parabolic cylinder deployable mechanism are established, and the accuracy of the theoretical model is verified using a numerical method. This novel parabolic cylinder deployable mechanism will have a significant influence in aerospace domain. Crucially, the work has value to design deployment mechanism for parabolic cylinder antenna.

Evaluating the performance of spherical, hemispherical, and tubular solar stills with various configurations - A detailed review

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.

Optical performance of a solar dish concentrator formed by the same size mirror located on parabolic frame

Solar dish concentrator with low cost and meeting the flux distribution is always pursued for the efficient utilization of concentrated solar energy. This paper investigates the optical performance of a solar dish concentrator formed by using a number of identical square mirror units arranged on a parabolic surface frame. The manufacturing of the mirror surface of this concentrator requires only one kind of mold, which has the significant advantage of low-cost manufacturing. Three common types of mirror units including the parabolic mirror (focal length fm), spherical mirror (radius Rm) and plane mirror are considered. The influence of key geometric parameters including the mirror width d (250–750 mm) and dimensionless parameters such as f1/D, fm/f1 and Rm/f1 (f1 is the focal length of parabolic frame) on its optical performance indexes such as the focused spot size (i.e., intercept width w), average local concentrator ratio (LCR), peak LCR and flux uniformity is analyzed using ray-tracing method, and the correctness of optical model and concentrator optical function is verified by outdoor concentrating experiments. The results show that the concentrator composed of parabolic or spherical mirrors can easily obtain a small circular focusing spot with high LCR and the intercept width can be easily controlled within 200 mm, the peak LCR can reach 34457 (average LCR is 12898), and average LCR reaches 14794 (peak LCR is 29497) at the smallest spot with w = 38.4 mm, which can be a low-cost alternative to parabolic dish concentrator. The concentrator with plane mirrors are easier to obtain square focusing spots with excellent flux uniformity, w can be controlled from 180 to 380 mm and uniform LCR is between 100 and 1400, which is very suitable for concentrating photovoltaic field.