High Concentration Ratio Research Articles

Experimental and Comparison Study on Two Solar Dish Systems with a High Concentration Ratio

Two high concentrating solar systems have been established with dish concentrator and plane-mirrors array concentrator. In the paper, the thermal performance has been experimentally studied with jet water cooling device and flat microchannel water-cooled device. The experimental results show that the maximum surface temperature difference of the dish concentrating system is greater than 20°C, while the plane-mirrors array system is lower than 4°C. It indicates that the plane-mirrors array concentrator has better uniformity. As the concentration ratio increases, the electrical efficiency of the concentrating photovoltaic system gradually decreases. When the concentration ratio is 200, the electrical efficiency of the photovoltaic system is 25%. The concentration ratio of 500 times or less is considered to be a suitable value, and then the electrical efficiency can still exceed 20%. It is found that the plane-mirrors array solar system is more suitable for the photovoltaic system than dish type system, which is only suitable for thermal power generation system.

Thermal energy analysis on liquid desiccant air conditioning system at different desiccant solution parameters

Selection of suitable liquid desiccant operating parameters plays a significant role in the design of energy efficient liquid desiccant air conditioning system. To achieve same dehumidification rate from ambient air, different combinations of solution parameters (heat capacity ratio, concentration, and vapor pressure) could be employed in the system. Considering dehumidifier air inlet condition and dehumidification rates are fixed, an analytical study is carried out on the thermal energy analysis of the system at different solution operating parameters. Operating parameters considered in this study are solution concentrations ( Cs = 0.25, 0.3, 0.35 and 0.40) and heat capacity ratios ([Formula: see text] = 2.5, 3, 4 and 5). Control volume which includes a pair of air and solution channels (half width channels) of full scale liquid-to-air membrane energy exchangers (LAMEE) has been chosen to analyze the energy transfer between air and solution. The results indicate system requires lesser chiller load ( Qchiller) at high concentration and low heat capacity ratio ( Cs = 0.40 and [Formula: see text] = 2.5) which is 0.29 kW to achieve 0.61 kW cooling load. This is 99% lesser than the Qchiller at high concentration and high heat capacity ratio ( Cs = 0.40 and [Formula: see text] = 5) and 30% lesser than the Qchiller at low concentration and low heat capacity ratio ( Cs = 0.25 and [Formula: see text] = 2.5). Solution heat addition rate ( Qadd) per kW cooling capacity ( Qcc) at this solution condition is found as 0.85 kW.

Effect of the concentration ratio on energetic and exergetic performance of concentrating solar collectors with integrated transparent insulation materials

The effect of the concentration ratio on the performance of parabolic trough and central receiver collectors with integrated transparent insulation materials (TIMs) is analyzed in this work. A model based on optical, energy, and exergy analyses is developed to determine thermal and second law efficiencies of concentrated solar collectors as a function of the absorber temperature and concentration ratio. The results are compared with the respective traditional collector configurations without TIM. In general, high concentration ratios are fundamental to maintain high efficiencies. The incorporation of a TIM into concentrated solar collectors leads to higher thermal efficiencies at high operating temperatures even at low concentration ratios. An equivalent second law efficiency to that of the reference collector configuration can be achieved at lower concentration ratios by incorporating a TIM in parabolic trough or a TIM and a glass envelope in central receiver collectors. The idea of using a TIM deserves further exploration as it seems to be a promising alternative that contributes to a more efficient and cost-effective technology.

Application of homogeneous membrane electrodialysis in the treatment of high-salt organic wastewater

In this paper, a homogeneous membrane electrodialysis system was used to separate the high COD and high sulfate concentrated water from a non-ferrous metal plant. After continuous pilot test, the results showed that the homogeneous membrane electrodialysis method has the characteristics of low energy consumption, high concentration ratio, strong ion selective permeability and effectively remove organic matter. Therefore, the production cost can be reduced and the recycling of waste water resources can be realized.

A mechanochemically synthesized porous organic polymer derived CQD/chitosan-graphene composite film electrode for electrochemiluminescence determination of dopamine.

Herein, we explore a new carbon source for preparation of carbon quantum dots (CQDs) with controllable composition using a porous organic polymer (POP) derived porous carbon via a nitric acid oxidation method. The POP used for the preparation of CQDs was synthesized by mechanochemical Friedel–Crafts alkylation under solvent free conditions. Using the as-prepared CQDs, we develop a simple and effective electrochemiluminescence (ECL) detection method for dopamine (DA) using a CQD/chitosan–graphene composite modified glassy carbon electrode (GCE). Both the electrochemical and ECL behaviors were studied in detail with ammonium persulfate as a coreactant. The complementary structure and synergistic function of the composite give the ECL sensor special properties. Apart from the high stability, it also presents good repeatability and high sensitivity to DA with a wide linear range from 0.06 to 1.6 μM. And a satisfactory detection limit of 0.028 μM (S/N = 3) was achieved for the prepared sensor. Furthermore, the ECL also shows high selectivity toward DA with an excellent interference resistance ability at a high concentration ratio of 100 (Cinterference : CDA = 100). In addition, the ECL sensor was successfully applied for effective detection and quantitative analysis of the actual dopamine in human body fluids for disease diagnosis and pathological studies.

Capillary-assisted localized crystallization on discrete micropillar rings

Microcrystals with defined sizes, morphologies, and locations provide a core opportunity for applications in microelectronic devices and microoptical components. Herein, a simple method was developed to obtain microcrystals with controlled sizes and locations by capillary-assisted localized crystallization, which utilizes “discrete micropillar rings” (DMRs) to mediate the solution evaporation process. Being different from conventional hydrophilic/hydrophobic modified surfaces, DMRs can guide the movement of three-phase contact lines, confine the solution residing inside the rings with a high concentration ratio, and help to crystallize microparticles (NaCl or CaCO3) without any further surface modification. Microcrystal sizes can be tuned in a wide range (from the order of ∼μm2 to that of ∼100 μm2) by changing the geometric parameters (height, pillar interval, and diameter) of pillar arrays. This facile, scalable, and low-cost technique for generating microcrystals with controlled size and location inside the DMRs holds great promise for micro-electronic and micro-optoelectronic applications.

An automated bacterial concentration and recovery system for pre-enrichment required in rapid Escherichia coli detection

One of the biggest challenges in rapid low concentration bacterial detection is the pre-concentration or pre-enrichment, which aims to increase bacteria concentration and reduce sample volume for easy bacterial detection. In practical bacterial detection, large-volume water samples with a pathogenic bacterial concentration of less than 1 CFU/mL have to be tested rapidly. The reported biosensors either have insufficient detection limit or have limited capability of handling a sufficiently large water sample. Therefore, a high-performance automated pre-enrichment process is strongly demanded in rapid practical bacterial detection. In this paper, a practical high performance automated bacterial concentration and recovery system (ABCRS) based on the combination of a ceramic membrane and tangential flow filtration technique was presented with short processing time (less than one hour), low pre-enrichment limit (≤0.005 CFU/mL), high concentration ratio (≥ 500), high recovery efficiency (~ 90%), and small final retentate volume (≤ 5 mL).

A fresnel concentrator with fiber-optic bundle based space solar power satellite design

A Fresnel concentrator with fiber-optic bundle based space solar power satellite (SSPS) is proposed as an innovative design in this paper. It consists of a flat Fresnel lens array for solar concentration, fiber bundles to transport the condensed sunlight to the photovoltaic panel and a highly modular sandwich module for power generation/transmission. Operating principle, structure configuration and efficiency of the system are presented in detail. Also, Fresnel concentrator with a secondary homogenizer is designed to obtain high concentration ratio and good irradiance uniformity on the solar cell. Lastly, to maintain the temperature fluctuation within a design requirement, the thermal analysis of the sandwich module is investigated. The obtained results demonstrate the feasibility of the proposed SSPS design.

Performance analysis of a solar thermoelectric generation (STEG) system with spray cooling

Use of an efficient cooling system is critical from the performance viewpoint of solar thermoelectric generation (STEG) systems. This study proposes the use of spray cooling as an effective technique for use in applications involving STEG systems. A mathematical model has been established to analyze STEG systems from the perspective of net generating efficiency and output power. Results demonstrate that compared to water-cooling, use of the spray-cooling technique results in enhanced generating efficiency, especially under high concentration ratios, owing to inherent advantages, such as high heat transfer performance, low power consumption, and no contact resistance. At a concentration ratio of roughly 200, the net generating efficiency when using spray cooling was observed to be 31.3% higher compared to that achieved when using water cooling. Under conditions of fixed module parameters and structure, there exist optimum values of the spray flow rate and concentration ratio that result in maximization of the net generating efficiency of STEG systems. This maximum efficiency of 13.203% occurs at a concentration ratio of 165 and corresponding flow rate of 0.35 L·min−1, at ZT = 1. Additionally, the net generating efficiency can be further enhanced by reducing the temperature of cooling water. The structural parameter γ is proposed to characterize the geometry of the thermoelectric module. As observed, there exists an optimum value of γ as well that tends to maximize the net generating efficiency of the system. Moreover, this optimum value of γ gradually increases with increase in concentration ratio. Results also demonstrate that optimum values of the spray flow rate and concentration ratio follow an approximately linear increase with increase in the ZT value of STEG modules.

Nature of substrate modification effect on thermal performance of simulated solar cells over phase-change immersion cooling under high concentration ratios

A new point from modifying substrate structure of solar cells is proposed based on direct-contact phase-change immersion cooling to solve the heat dissipation problem of solar cells worked under high concentration ratios. An electric heating plate (EHP) is carefully designed to simulate the heat flux of solar cells under high concentration ratios (184.2 X). Easy and lower cost ways of electrochemical etching and mechanical drawing bench are adopted to modify substrate surface of simulated solar cells. The result of thermal measurement shows substrate, undergoing electrochemical etching for 2 h (CE-2) or mechanical drawing bench using 800 mesh (MDB-800), owns the lower wall average temperature (85.36 and 85.7 °C) and higher surface heat transfer coefficient (3008 and 2970 W/(m2 K)). SEM results reveal that CE-2 or MDB-800 has uniform-distributed porous or dense-grooved structure. These special structures show better surface wettability and provide more active nucleus sites for small bubbles generation as well as higher bubbles update frequency according to our modified surface wettability and quantitative analysis results. Our study reveals that the advanced heat transfer performance is attributed to substrate structure with uniform-distributed porous or dense-grooved of CE-2 or MDB-800. This work gives a theoretical guidance for heat transfer advancement investigation involved in surface characteristic.

Numerical Analyses of High Concentrator Triple-Junction Solar Cell under Jet Impingement Cooling

The triple junction III-V(TJ) solar cells are commonly used for the high concentrator photovoltaic (HCPV) arrangements as they have high efficiency and have a good response to high concentration. Nevertheless, the efficiency of solar cells decreases with an increase of temperature especially under high solar irradiance concentration ratios where the temperature of solar cells reaches to very high levels. Consequently, heat dissipation by cooling is crucial for a concentrator photovoltaic solar cell at high concentration. Moreover, significant temperature difference possibly will exist within the cell body, so it is vital to identify the presence of thermal stresses that can cause failure and deformation of the cell body.This work investigated the capability of impinging jet cooling technique to maintain a triple junction solar cell temperature under recommended operating conditions. Furthermore, thermal stress analyses were performed. The results showed that employing jet impingements cooling improved both of thermal energy and electrical generation. In addition, the thermal stress is considerably decreased with increasing the cooling inlet mass flow rate.

Development and performance studies of a novel portable solar cooker using a curved Fresnel lens concentrator

Solar cookers use clean and accessible solar energy to heat food. They provide a new choice for outdoor cooking for users. However, currently available solar cookers now have some weaknesses such as being too big to carry, low heating temperature and overlong cooking time. To overcome these problems, this paper designs a novel portable solar cooker using a curved Fresnel lens as the concentrator. This novel solar cooker can focus sunlight onto an evacuated tube collector to heat the food here. It has a high concentration ratio and allows tracking the sun in both zenith and azimuth angles manually, therefore it is possible to get higher cooking temperature and shorten the cooking time. In this paper, the structure and working principle of the device are introduced. The optical performance of the system is simulated by a software and the heat transfer model of the system is established and presented. Experimental studies have been carried out, and the variation of maximum temperature of the system during the day under no-load condition has been obtained. Moreover, to test the system performance, the theoretical maximum temperatures of the system with no-load condition under different irradiances have been calculated. Results indicate that when direct irradiance is I = 712 W/m2 the obtained highest average temperature of the system without load can reach at about 361 °C. Besides, the performance of the solar cooker has been tested on four kinds of 0.5 kg representative foods, namely, sweet potato, pork (all lean), yam and radish. Results show that cooking time of pork is the shortest (only 34 min), and radish is the longest (64 min). All cooked food reaches the edible standard.

Bioconcentration, metabolism and the effects of tetracycline on multiple biomarkers in Chironomus riparius larvae

The antibiotic tetracycline (TC) is widespread in surface waters, but few data are available regarding its adverse effects on aquatic insects. In this study, we investigated the bioconcentration, metabolism, and effects of TC on Chironomus riparius larvae exposed to different concentrations of TC (1.83, 18.5 and 174 μg L−1) for 48 h. The bioconcentration factors were 3.65, 0.74 and 0.23 in larvae with exposure to 1.83, 18.5 and 174 μg L−1 TC, respectively. High concentration ratios of the metabolites anhydrotetracycline (0.56–0.60), 4-epitetracycline (0.43–0.69), and 4-epianhydrotetracycline (0.50–0.55) to the unmetabolized compound were found. Additionally, the activities of superoxide dismutase and glutathione S-transferase were markedly inhibited with a significant increase in malondialdehyde contents at high exposure concentrations of TC (18.5 and 174 μg L−1). Moreover, significant up-regulation of heat shock genes (hsp70 and hsp27), the ecdysone receptor gene, and the E74 early ecdysone responsive gene was observed at all exposure concentrations except for hsp70 at 1.83 μg L−1. Collectively, these results suggested that TC was quickly absorbed and metabolized by C. riparius and resulted in molecular and biochemical disturbances.

Parabolic trough collector with rhombus tube absorber for higher concentration ratio

ABSTRACTIn the present study, the concentration ratio of the parabolic trough collector using rhombus tube absorber has been estimated. An analytical technique has been developed to determine the optimum size of the rhombus tube absorber for given trough dimensions. The optimum size of the rhombus tube absorber is 13.8% smaller than the circular tube absorber for the LS3 trough with no change in intercept factor. The maximum improvement in the concentration ratio is found to be 31.5% for the troughs with rim angle 90° in comparison to circular tube absorber. Results also indicate that rhombus tube absorber can be employed for a range of rim angle 75 to 90 degree.Abbreviations: CR: concentration ratio; CSP: concentrated solar power; MCRT: Monte Carlo ray tracing; PTC: parabolic trough collector

Effect of applying lactic acid bacteria and cellulase on the fermentation quality, nutritive value, tannins profile and in vitro digestibility of Neolamarckia cadamba leaves silage.

This study was designed to evaluate the effect of applying lactic acid bacteria (LAB, Lactobacillus plantarum LP) (0 and 1×106 cfu/g fresh matter (FM)) and cellulase (0, 30, 60 and 120U/gFM) on the ensiling characteristics of N.cadamba leaves. The experimental design was a completely randomized 2×4 factorial arrangement. Fermentation parameters, microbial populations, chemical compositions and in vitro digestibility of the silages were measured after 60-day fermentation. LAB inoculation decreased the pH (p<0.05), ammonium nitrogen (NH3 -N) proportion (p=0.08), the concentrations of crude protein (CP, p<0.05) and condensed tannins (CT, p=0.07), and the microbial counts (p<0.01) of LAB and yeasts along with increased (p<0.01) concentrations of neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and hemicellulose. Cellulase addition increased (p<0.01) the microbial populations and protein fractions and decreased (p<0.01) the concentrations of acetic acid, cell wall components, total phenols (TP), soluble tannins (ST) and CT with increasing enzyme inclusions. The interaction of LAB and cellulase showed an effect (p<0.01) on the NH3 -N proportion, microbial counts, fibre fractions and CP. No effect (p>0.05) was found on the dry matter recovery and digestibility of the silages with LAB or cellulase application. Besides, high lactic acid concentration and true protein ratio, low pH and NH3 -N proportion, and a few spoilage organism counts were found in all silages, indicating a successful preservation. These results infer that, with some improvement, the ensiling characteristics and chemical compositions of N.cadamba leaves silage show specific responses to the addition of LAB inoculant or cellulase.

A thorough study on electrochromic properties of metal doped tungsten trioxide film prepared by a facile solution process

In this research, we investigate the effect of metal doping on the electrochromic (EC) performance of tungsten trioxide (WO3) films. These films were prepared by a novel method involving solution processing and thermal annealing. In this procedure, ammonium tetrathiotungstate ((NH4)2WS4) was dissolved in dimethylformamide at a high concentration ratio (200 mg mL−1) to obtain a homogeneous solution and then spin-coated onto the indium thin oxide (ITO) substrate for use as a working electrode. Subsequently, the film was annealed at the different temperatures (200, 300, 400, and 500 °C) to form a crystal structure of WO3. X-ray diffraction, Raman, and X-ray photoelectron spectroscopic results confirm the crystal formation of WO3. Moreover, in order to improve the electrochromic performance, different concentrations (10, 20, 30, and 40 mM) of different metal chlorides such as PtCl4, PdCl2, AuCl3, AgCl, CuCl2, NiCl2, NaCl, and KCl were added into the (NH4)2WS4 precursor and the mixture was coated on the ITO substrate and annealed at 500 °C. The results indicate that the performance of the Au-doped WO3 film was better than those with other dopants, likely as a result of the plasmonic effect. Therefore, the proposed method and Au-doped WO3 films are great candidates for the development of smart windows with high EC performance.

Thermal hydraulics of natural circulation loop in beam-down solar power tower

There have been continuous efforts by researchers and power producing companies to reduce various costs involved in solar power tower (SPT) plants. Economically deploying conventional SPT plants for industries using thermal or thermo-chemical processes which need temperatures >1100 K could be challenging. Here, the overall economics of deployment of conventional SPT could go unfair as such design needs larger heliostat field, therefore costlier stiffer heliostats to reach high concentration ratio (CR). These challenges can be solved by beam-down SPT which uses secondary reflector mounted on tower top and receiver cum secondary concentrator on the ground could achieve desired CR, is one potential candidate to save on tower construction and pumping costs. Using beam-down SPT heat can be made available at the ground which opens an option of extracting the heat using natural circulation loop (NCL). The current paper explores the new proposed configuration of NCL in terms of understanding thermal hydraulics using 3-D CFD simulations. Further, it also incorporates optimization of the proposed design configuration using formulated heat transfer model. The optimized geometry is simulated using 3-D CFD simulation which gave the desired rating.

Enhancement of selective Cu(II) sorption through preparation of surface-imprinted mesoporous silica SBA-15 under high molar concentration ratios of chloride and copper ions

We synthesized and characterized surface-imprinted poly (ethyleneimine) (PEI)-grafted mesoporous silica SBA-15 (Cu-imprinted PEI-SBA-15) for selective Cu(II) sorption from aqueous solutions. To enhance the Cu(II) selectivity of Cu-imprinted PEI-SBA-15, Cu(II) loading on PEI-SBA-15 was increased via Cu(II) sorption under high-molar-concentration ratios of chloride (Cl) and Cu(II) ions. Then, selective Cu(II) sorption sites were increased through imprinting processes (crosslinking and elution) on Cu-loaded PEI-SBA-15. Selective experiments were performed using Cu-imprinted PEI-SBA-15 prepared at various [Cl−]/[Cu(II)] ratios, ranging from 2 to 1000. In multinary solutions containing divalent ions, such as Cu(II), Pb(II), Zn(II), Ni(II), and Co(II), Cu(II) selectivity was highest (79.62) at a [Cl−]/[Cu(II)] ratio of 500; the relative Cu(II) selectivity for Cu-imprinted PEI-SBA-15 over PEI-SBA-15 was 29.24. In multinary solutions containing Cu(II) along with trivalent and tetravalent ions, such as Al(III), Cr(III), and Zr(IV), the Cu(II) selectivity was also highest (3.40) at a ratio of 500; the relative Cu(II) selectivity was 3.96. In this study, we demonstrated that the Cu(II) selectivity of surface-imprinted SBA-15 could be enhanced through its preparation under high [Cl−]/[Cu(II)] ratios.

Performance Analysis and Optimization of Concentrating Solar Thermoelectric Generator

A thermodynamic model for a concentrating solar thermoelectric generator considering the Thomson effect combined with Fourier heat conduction, Peltier, and Joule heating has been developed and optimized in MATLAB environment. The temperatures at the hot and cold junctions of the thermoelectric generator were evaluated by solving the energy balance equations at both junctions. The effects of the solar concentration ratio, input electrical current, number of thermocouples, and electrical load resistance ratio on the power output and energy and exergy efficiencies of the system were studied. Optimization studies were carried out for the STEG system, and the optimum number of thermocouples, concentration ratio, and resistance ratio determined. The results showed that the optimum values of these parameters are different for conditions of maximum power output and maximum energy and exergy efficiency. The optimum values of the concentration ratio and load resistance ratio for maximum energy efficiency of 5.85% and maximum exergy efficiency of 6.29% were found to be 180 and 1.3, respectively, with corresponding power output of 4.213 W. Furthermore, at higher concentration ratio (C = 600), the optimum number of thermocouples was found to be 101 for maximum power output of 13.75 W, maximum energy efficiency of 5.73%, and maximum exergy efficiency of 6.16%. Moreover, the optimum number of thermocouple was the same for conditions of maximum power output and energy and exergy efficiency. The results of this study may provide insight for design of actual concentrated solar thermoelectric generator systems.

Microscopic morphology and seasonal variation of health effect arising from heavy metals in PM2.5 and PM10: One-year measurement in a densely populated area of urban Beijing

In order to study the sustained impact of particulate matter on urban residents, 572 PM2.5 and PM10 samples in all were attained simultaneously from a densely populated area of Beijing from September 2015 to August 2016. 11 types of heavy metals were determined as to better ascertain the seasonal variation characteristics of particle composition. In the course of the year, the mean concentrations of PM2.5 and PM10 were detected to be 102.45 μg m−3 and 144.75 μg m−3, respectively. From general perspective, winter turned out to be the longest in haze day quantity and the highest in particle concentration, followed by spring, autumn and summer, successively. The mass concentrations of numerous PM2.5 elements fluctuated evidently in the decreasing order of Ba, Zn, Mn, Sr, Cu, Pb, Cr, V, Ni, Cd and Sb. In contrast with other seasons, winter displayed the most evident increase of metal content in particulates, especially under the condition of haze. Relationship between different size particles was also reckoned with in this study. High concentration ratio of PM2.5 and PM10 (0.76–0.84) was detected during haze period, and PM2.5 was accounted as a primary pollutant during haze-fog day in Beijing. Moreover, the carcinogenic and non-carcinogenic risk posed by detected heavy metals was investigated. Cr posed the highest carcinogenic risk, and in the meantime, as compared with other non-carcinogenic metals, value of Pb was the highest in Hazard Quotient. Risk arising from Cr and Cd in winter shall be noteworthy, and accordingly it may pose danger or potential risk to adults in haze days. Eventually, a large amount of fly ash and soot particles in winter samples were indicated from SEM-EDX analysis results, whereas those are rarely detected in summer samples.