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Concentration Measurement of Uniform Particles Based on Backscatter Sensing of Optical Fibers
摘要： A set of miniature optical fiber particle concentration measuring instruments is designed and applied to develop a unified expression for the concentration measurement of uniform particles in tap water. By measuring the concentrations of six uniform silicon carbide particles in the size range of 38–250 μm, the unified relationship between particle size, particle concentration, and optical scattering intensity is proposed. The unified expression is verified by the concentration measurements of silicon carbide particles with three other sizes. The results show that the measurement error is less than 10%, and the unified expression is satisfactory considering the large measuring range of 0–50 kg/m3. The effects of light intensity on the concentration measurement are discussed based on the results of 150 μm silicon carbide particles under three different light intensities. It is shown that a low light intensity can be applied for high-concentration measurement with relatively low accuracy, while a high light intensity can be adopted for low-concentration measurement with higher accuracy.
关键词： unified expression,optical backscatter,optical fiber,uniform particles,silicon carbide,particle concentration
更新于2025-09-16 10:30:52
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Knowledge-Based Sensors for Controlling A High-Concentration Photovoltaic Tracker
摘要： To reduce the cost of generated electrical energy, high-concentration photovoltaic systems have been proposed to reduce the amount of semiconductor material needed by concentrating sunlight using lenses and mirrors. Due to the concentration of energy, the use of tracker or pointing systems is necessary in order to obtain the desired amount of electrical energy. However, a high degree of inaccuracy and imprecision is observed in the real installation of concentration photovoltaic systems. The main objective of this work is to design a knowledge-based controller for a high-concentration photovoltaic system (HCPV) tracker. The methodology proposed consists of using fuzzy rule-based systems (FRBS) and to implement the controller in a real system by means of Internet of Things (IoT) technologies. FRBS have demonstrated correct adaptation to problems having a high degree of inaccuracy and uncertainty, and IoT technology allows use of constrained resource devices, cloud computer architecture, and a platform to store and monitor the data obtained. As a result, two knowledge-based controllers are presented in this paper: the first based on a pointing device and the second based on the measure of the electrical current generated, which showed the best performance in the experiments carried out. New factors that increase imprecision and uncertainty in HCPV solar tracker installations are presented in the experiments carried out in the real installation.
关键词： sun tracker,high-concentration photovoltaic systems,knowledge-based sensor,Internet of Things
更新于2025-09-16 10:30:52
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Thermodynamic analysis of Organic Rankine cycle driven by reversed absorber hybrid photovoltaic thermal compound parabolic concentrator system
摘要： In current study, an effort is made to improve the overall performance of the solar powered organic Rankine system to meet increasing energy demand and mitigate the resulting menace caused by environmental imbalance. Hourly performance evaluation of Solar powered Organic Rankine Cycle (ORC) system is done for varying concentration ratio in terms of collector output temperature, heat gain in evaporator, combined thermal and exergetic efficiency. The Heptane/R245fa is used as working fluid at fixed (0.1/0.9) fractional mass component. Organic Rankine system is coupled with reversed absorber hybrid photovoltaic thermal compound parabolic concentrator (PVTCPC). The highest collector outlet temperature 125.45 (cid:1)C, heat gain 3.21 (cid:3) 105 W, combined thermal efficiency 7.8%, and exergetic efficiency 14.38% is observed at 13:00 h for 6 concentration ratio of the concentrator. This study establishes the utility of low-grade renewable heat source conversion into solar electrification, solar irrigation, solar cooling and solar water purification.
关键词： Concentration ratio,Heptane /R245fa,Reversed absorber,Zeotropic mixture,Organic Rankine cycle
更新于2025-09-16 10:30:52
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Evaluation of Silica Nanofluids in Static and Dynamic Conditions by an Optical Fiber Sensor
摘要： This work presents an optical fiber dynamic light scattering sensor capable of simultaneously assessing concentration and flow speed of nanofluids. Silica nanoparticles (189 nm) in water were tested, yielding a sensitivity of 0.78288 × 103 s?1 for static conditions. Then, the sensor was submitted to situations that simulate spatial concentration changes, offering better results than those obtained by traditional mathematical models. Finally, in flow tests, the light backscattered by the nanoparticles were collected by a fiber probe placed parallel to the streamline, whereas intensity values were processed by artificial neural networks. The sensor provides average errors of 0.09 wt% and 0.26 cm/s for concentration and speed measurements, respectively, and can be further applied to assess different types of nanofluids and inline processes.
关键词： silica nanofluid,concentration measurement,optical fiber sensor,flow speed measurement
更新于2025-09-16 10:30:52
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A new method to enhance organic photodetectors active layer trap doping by blending doping
摘要： In order to solve the problem of high concentration trap doping in the active layer of organic detector, a blending doping method is proposed in this paper. The influence of the doping concentration of C60:C70 on the trap concentration in the P3HT:PC61BM active layer and the optoelectronic performance of the detector are studied through experiments. It founds that the maximum doping concentration and trap concentration of active layer could arrive to 1.5 wt.% and 3.26×1018 cm-3 respectively after blending doping, which increased by 50% and one order of magnitude compared with the maximum doping concentration of single C60(doping concentration:1.0wt.%, trap concentration: 5.83×1017 cm-3), and the external quantum efficiency is increased by 8 folds from 1067.84% to 8510.17%. The result shows that the doping concentration and the trap concentration can be greatly improved using the blending doping method, and thereby the high concentration trap doping of the active layer can be achieved.
关键词： high doping concentration,blending doping,organic photodetectors
更新于2025-09-12 10:27:22
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Design of Curved Fresnel Lens with High Performance Creating Competitive Price Concentrator Photovoltaic
摘要： In this paper, the design of a curved Fresnel lens applying to the concentrator photovoltaic system is proposed by using the edge ray theorem, the Snell’s law, and the conservation of optical path length. The new structure of the curved Fresnel lens can improve significantly the uniformity of sunlight distribution over the solar cell while the concentration ratio can reach a high value of 900 times. The good uniform distribution can be obtained by using the novel idea. The novel idea is based on the uniform sunlight distribution of every groove of the lens so that the whole lens also distributes uniformly the sunlight beam over the receiver. The structure of the lens is built by two surfaces: input surface (or upper surface) as a part of spherical surface and output surface (or lower surface) that consists all grooves of the lens. Matlab program is used to design the input and the output surfaces of the lens. The input surface and the output surface are independent to each other in construction in Matlab. LighttoolsTM software is used to optimize the structure of the novel lens. Furthermore, LighttoolsTM is also used to perform a simulation to examine the efficiency of the lens in concentrator photovoltaic (CPV) system by using the light source with a wide spectrum of 380 – 1600 nm. The results show that the lens has an acceptance angle of 0.80 and good optical efficiency (>85%).
关键词： concentrator photovoltaic (CPV),Fresnel lens,solar energy,high concentration ratio,multi-junction solar cells,uniform irradiance distribution,CPV without secondary optical element (SOE)
更新于2025-09-12 10:27:22
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The Effect of Chiral Ligand Concentration and Binding Mode on Chiroptical Activity of CdSe/CdS Quantum Dots
摘要： Chiroptically active fluorescent semiconductor nanocrystals, quantum dots (QDs), are of high interest from a theoretical and technological point of view as they are promising candidates for a range of potential applications. Optical activity can be induced in QDs by capping them with chiral molecules, resulting in circular dichroism (CD) signals in the range of the QD UV-Vis absorption. However, the effects of the chiral ligand concentration and binding modes on the chiroptical properties of QDs are still poorly understood. In the present study, we report the strong influence of the concentration of a chiral aminoacid (cysteine) on its binding modes upon the CdSe/CdS QD’s surface, resulting in varying QD chiroptical activity and corresponding CD signals. Importantly, we demonstrate that the increase of cysteine concentration is accompanied by the growth of the QD CD intensity, reaching a certain critical point after which it starts to decrease. The intensity of the CD signal varies by almost an order of magnitude across this range. NMR and FTIR data, supported by DFT calculations, reveal a change in the binding mode of cysteine molecules from tridentate to bidentate when going from low to high concentrations, which results in a change in the CD intensity. Hence, we conclude that the chiroptical properties of QDs are dependent on the concentration and binding modes of the capping chiral ligands. These findings are very important for understanding chiroptical phenomena at the nanoscale and for the design of advanced optically active nanomaterials.
关键词： cysteine,chiroptical activity,density functional theory,quantum dots,chirality,ligand concentration,binding mode
更新于2025-09-12 10:27:22
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Effects of Particle concentration, deposition and accumulation on Photovoltaic device surface
摘要： The efficiency of solar photovoltaic system is affected by many factors, among which the influence of dust deposition on photovoltaic panels is a prominent problem. In the desert which has sufficient radiation, the problem of dust deposition is quite serious. In some developed cities, photovoltaic devices are affected by dust or aerosol deposition. This short paper, thus, briefly summarizes studies of dust deposition on PV panels of urban and desert areas in recent years, and analyses the influence of dust deposition on the panel, particle characteristics and dust deposition process based on these studies. In general, there are three fields that suggests more research: (1) study on characteristics of sand or dust combined with local environmental characteristics; (2) modeling and simulation of particle dynamics around photovoltaic array; (3) comprehensive laboratory designed experiments to understand the specific influencing factors.
关键词： Airborne concentration,Efficiecy reduction,Photovoltaics (PV),Dust deposition,Accumulation
更新于2025-09-12 10:27:22
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Modeling and optimization of n-c-AlGaAs/p-c-GaAs solar cells
摘要： The main of our work is to establish a model which enables us to predicate an improvement for solar cells e?ciencies elaborated by hetero-structures compounds; we focused our optimization by simulation on an n-c-AlGaAs/p-c-GaAs solar cell with back surface ?eld (BSF), which is a p/p+ (Low-High) junction. This junction creates a potential barrier which avoid speedy recombination of minor careers (electron in the base), however all the main parameters which have large impact on the short circuit current density, on the open circuit voltage, on the ?ll factor and on the conversion e?ciency were discussed in this work. Generally the electrical conversion is function of the acceptor and donor doping concentrations, of the cell emitter and the base thicknesses, of the surface recombination velocity at front and back contacts and of careers live times (for electrons and holes). The e?ects of the discontinuities occurring in the energies bands clause to the interface were taken into consideration too. Under A.M 1.5 illumination, our calculations results reveal an e?ciency of 23.80% for the optimum parameters (Nd = 5 × 1018 cm?3, Na = 5 × 1017 cm?3, JSC = 25.77 mA/cm2, VOC = 0.985 V, Sf = 104 cm/s and Sb = 108cm/s). It seems that this simulated device can be used in cell concentrations utilities and, it presents an e?ciency of 29.28% under 100 A.M 1.5. Finally, based on these attempts, the n-c-AlGaAs/ p-c-GaAs structure is suggested as promising solar cell applications and the actual model is intended to be extended to multilayer solar cells.
关键词： Solar cell,E?ciency,Thickness,Sun concentrations,Doping concentration,Recombination velocities
更新于2025-09-12 10:27:22
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Model of phosphorus diffusion in silicon for highly doped solar cell emitter layer
摘要： Purpose – The purpose of this paper was the development of a model enabling precise determination of phosphorus concentration pro?le in the emitter layer of a silicon solar cell on the basis of diffusion doping process duration and temperature. Fick’s second law, which is fundamental for describing the diffusion process, was assumed as the basis for the model. Design/methodology/approach – To establish a theoretical model of the process of phosphorus diffusion in silicon, real concentration pro?les measured using the secondary ion mass spectrometry (SIMS) method were used. Samples with the phosphorus dopant source applied onto monocrystalline silicon surface were placed in the heat zone of the open quartz tube furnace, where the diffusion process took place in the temperature of 880°C-940°C. The measured real concentration pro?les of these samples became template pro?les for the model in development. Findings – The model was developed based on phenomena described in the literature, such as the in?uence of the electric ?eld of dopant ionized atoms and the in?uence of dopant atom concentration nearing the maximum concentration on the value of diffusion coef?cient. It was proposed to divide the diffusion area into low and high dopant concentration region. Originality/value – A model has been established which enabled obtaining a high level of consistency between the phosphorus concentration pro?le developed theoretically and the real pro?le measured using the SIMS method. A coef?cient of diffusion of phosphorus in silicon dependent on dopant concentration was calculated. Additionally, a function describing the boundary between the low and high dopant concentration regions was determined.
关键词： Concentration pro?le,Solar cell,Doping process,Emitter layer,Phosphorus diffusion
更新于2025-09-12 10:27:22