An initial investigation of amorphous silicon-selenium solar cells

Amorphous silicon-selenium solar cells, where a selenium alloy thin film was used as an intrinsic layer, were successfully fabricated by plasma-enhanced chemical vapor deposition. The cells have a simple p-i-n structure. The maximum conversion efficiency of the cells was 5.1 %, measured under 100 mW/cm [2] ELH white light illumination. The fabricated selenium alloy solar cells exhibited stable characteristics under white light soaking, with respect to those of amorphous silicon comparison solar cells, fabricated under similar conditions. Measurement of the quantum efficiency showed that this cell can be used as a top cell in a tandem cell structure.     

热丝辅助MWECR-CVD法沉积氢化非晶硅薄膜研究

为了降低a-Si:H薄膜中的氢含量,提高其稳定性,在我们MWECR-CVD系统中引入了热丝装置,热丝对等离子体的热辐射使等离子体升温,既促进了气体的进一步分解和电离,获得较多的低氢原子基团,也减少了活性高硅烷聚合物的生成,从而使薄膜中的(SiH2)n的含量降低。同时,热丝对样品表面提供的热辐射和光辐射也可以进一步降低薄膜的氢含量。实验结果表明,用这种装置沉积的a-Si:H薄膜,氢含量可降低到4.5at%左右,稳定性明显增强,光敏性也有一定改善。     

Preparation of very stable and low hydrogen content amorphous silicon films by hydrogen-radical CVD method

High-quality a-Si : H films have been prepared by a hydrogen-radical CVD method. Films with high photosensitivity and high stability against light illumination could be prepared from both Si₂H₆ and SiH₄. It was found that hydrogen content is considerably low compared with films prepared by other deposition methods. These results suggest that hydrogen radicals contribute to the improvement of film properties.     

On the sensitivity of open-circuit voltage and fill factor on dangling bond density and Fermi level position in amorphous silicon p–i–n solar cell

A simple method for calculation of current–voltage characteristics of an amorphous silicon solar cell is described in terms of excitation current, J_G, and excitation voltage, V_G, the latter being defined in terms of separation of quasi-Fermi levels. Contrary to the usual method of calculating the short-circuit current and dark current separately and assuming a linear superposition, in the present method the calculations are done first in the open circuit where the neutrality of space charge can be assumed and then the current has been calculated in terms of a gradient in the quasi-Fermi levels. We find that depending on other parameters, the open-circuit voltage is a weak function of dangling bond density except in cases of very large degradation. The sensitivity of open-circuit voltage, V_oc, to light-induced degradation can further be reduced by moving the thermal equilibrium Fermi level above the upper dangling bond level. Fill factor deterioration is found to be mainly due to conductivity modulation and is higher for the lower values of thermal equilibrium Fermi level.     

Influence of the intrinsic layer characteristics on a-Si:H p–i–n solar cell performance analysed by means of a computer simulation

In this paper a set of one-dimensional simulations of a-Si:H p–i–n junctions under different illumination conditions and with different intrinsic layer are presented. The simulation program ASCA permits the analysis of the internal electrical behaviour of the cell allowing a comparison among the different internal configurations determined by a change in the input set. Results about the internal electric configuration will be presented and discussed outlining their influence on the current tension characteristic curve. Considerations about the drift–diffusion and the generation–recombination balance distributions, outlined by the simulation, can be used to explain the correlation between the basic device output, the i-layer characteristics (thickness and DOS), the incident radiation intensity and photon energy.     

Effect of edge junction isolation on the performance of laser doped selective emitter solar cells

The effect of laser and chemical edge junction isolation on electrical performance of industrially manufactured laser doped selective emitter solar cells with light induced plated n-type contacts is investigated in this work. Directly after the formation of the aluminium back surface field, photoluminescence images indicates that laser edge junction isolation causes substantial damage around the perimeter of the cell, extending several millimeters from the laser edge isolation groove. On finished devices, regions of high series resistance are evident around the perimeter, caused by parasitic plating nucleating in the damaged laser grooved region which induce shunting and inhibits further plating taking place in the surrounding regions. The use of chemical edge junction isolation eliminates both of these issues and can result in efficiency gains of more than 2% absolute compared to that fabricated using laser edge isolation, suggesting a far superior method of edge junction isolation for the industrial manufacture of laser doped selective emitter solar cells with light induced plated contacts.     

Effect of dust accumulation on solar transmittance through glass covers of plate-type collectors

Dust accumulation on glass plates with different tilt angles and associated reductions in solar transmittance have been experimentally investigated over a period of 1 year under the climate conditions of the Minia region, middle of Egypt. The glass plates were never cleaned during the experiment duration of 1 month to allow dust to accumulate. The results showed that the fractional reduction in glass normal transmittance depends strongly on dust deposition in conjunction with plate tilt angle, as well as on the exposure period and site climate conditions. Based on the data obtained, an empirical correlation, accurate to ±6%, is developed which allows for the calculation of the reduction in glass transmittance for a given tilt angle after a number of days of exposure to the atmosphere. For design purposes and in the absence of any specific data, the literature comparisons encourage the use of the correlation for other neighboring regions along the desert belt that extends from the Atlantic Ocean to the Persian Gulf. For moderately dusty places, weekly cleaning of the glass covers of solar panels is strictly recommended as part of the maintenance routine, but equipment should be cleaned immediately after a dust storm to retain nominal operating efficiency.     

三种催化剂对半焦燃烧特性的影响

用热天平研究了四种半焦的燃烧特性,结果表明：添加催化剂制得的半焦具有较好的反应活性。炭燃烧反应前需要吸附的氧量也相对较小,具有较小的ＭＩ值;并通过燃烧动力学计算发现添加氧化钙制得的半焦燃烧活性最高;最后,提出了平均活化能的概念来作表示半焦燃烧活性的一个指标,提出了平均活化能的概念来作表示半焦燃烧活性的一个指标,并与其它研究者提出的可燃性综合指标Ｓ进行了比较。     

Effect of pore characteristics on hydrogen reduction kinetics based on a novel analysis approach combined model-fitting and iso-conversion

Carbon reductant used in metallurgy industry is a considerable source of carbon dioxide emissions. Growing concerns over greenhouse effect have urgently prompted research in the application of hydrogen energy as an alternative. However, some basic kinetic problems in the hydrogen reduction process have not been clarified and resolved yet, such as the activation energy fluctuations caused by neglect of pore characteristics, along with the overly subjective division of the whole reaction process to analyze rate limiting mechanisms. In this study, a novel approach for acquiring instantaneous activation energy is proposed that is able to identify the activation energy at every reaction moment and thereby provide a quantitative basis for kinetics segmentation and rate-limiting mechanism determination. Moreover, due to the space requirements, the activation energy for the reaction stage controlled by nucleation and nuclei growth has a strong correlation with specific surface area. Whereas the restriction mechanisms of chemical reaction and diffusion are closely related to the average pore size. These results reveal that the different pore characteristics and changes in value have a direct influence on the corresponding rate limiting mechanisms and restriction degrees.     

Effect of mass-ratio,damping, and stiffness on optimal hydrokinetic energy conversion of a single,rough cylinder in flow induced motions

Flow Induced Motions (FIMs) of a single, rigid, circular cylinder with end-springs are investigated for Reynolds number 30,000 ≤ Re ≤ 120,000 with mass ratio, damping, and stiffness as parameters. Selective roughness is applied to enhance FIM and increase the hydrokinetic energy captured by the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter at higher Reynolds numbers. The second generation of virtual spring-damping system Vck, recently developed in the Marine Renewable Energy Laboratory (MRELab), enables embedded computer-controlled change of viscous-damping and spring-stiffness for fast and precise oscillator modeling. Experimental results for amplitude response, frequency response, energy harvesting, and efficiency are presented and discussed. All experiments were conducted in the Low Turbulence Free Surface Water (LTFSW) Channel of the MRELab of the University of Michigan. The main conclusions are: (1) The oscillator can harness energy from flows as slow as 0.3946 m/s with no upper limit. (2) Increasing the spring stiffness, shifts the VIV synchronization range to higher flow velocities, resulting in reduced gap between VIV and galloping, where the harnessed power drops. (3) In galloping, the harnessed power increases with the mass ratio. (4) Local optima in energy conversion efficiency appear at the beginning of the VIV upper branch and at the beginning of galloping. (5) Local optima in power appear at the end VIV upper branch and at the beginning of galloping.     

Impact of activation energy and gyrotactic microorganisms on flow of Casson hybrid nanofluid over a rotating moving disk

Many models of various non-Newtonian fluid flows for different geometries are available for analyzing the mass and heat transfer. Nevertheless, for researchers, it is challenging to choose the most suitable model for a specific geometry. Here, we have adopted a modified Buongiorno model to explore the impact of activation energy on the Casson hybrid nanofluid flow over an upward/downward-moving rotating disk filled with the gyrotactic microorganisms. Moreover, the external magnetic field can establish the magnetic effect, which normalizes the features of heat, mass transfer, and fluid flow. Here, we used silver and copper as nanoparticles suspended in human blood as the carrier fluid. The modeled partial differential equations are converted to ordinary differential equations by opting suitable similarity variables. The numerical solutions of these reduced equations are attained by means of Runge–Kutta–Fehlberg fourth-fifth-order method by adopting a shooting scheme. An investigation of the attained outcomes reveals that the flow field is affected appreciably by the activation energy, bioconvection, and magnetic effect. Peclet and concentration difference numbers diminish the microorganism's profile. A rise in values of the Brownian motion parameter leads to an increase in the rate of heat transfer.     

双效精馏节能影响因素的研究

介绍了双效精馏的原理和几种典型的操作方式,阐明了双效精馏的选择依据和应用原则.结合实际操作数据,对影响双效精馏节能的影响因素进行分析,讨论了回流比、塔的操作压力等对精馏系统节能的影响.     

Effect of solvent on fabrication of active layers in organic solar cells based on poly(3-hexylthiophene) and fullerene derivatives

Investigating the effect of solvent on the fabrication of photo-active layers in bulk heterojunction organic solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl C₆₁-butyric acid methyl ester, we found the short-circuit current density (J_SC) and fill factor (FF) of a cell with a photo-active layer made using materials dissolved in a mixture of o-dichlorobenzene with chloroform to be slightly higher than those of a cell made using the same materials dissolved only in chlorobenzene. Evaluating the absorption spectra, surface morphology, charge mobility, and solubility of photo-active films made using different solvents, we concluded that the higher J_SC and FF were due to a larger interfacial area between the photo-active materials in the layer.     

考虑聚合效应的多点分布式储能系统灵活性评价方法研究

针对多点分布式储能系统的灵活性评价问题,深入讨论分析了电力系统灵活性的定义、内涵,提出了考虑聚合效应的多点分布式储能系统灵活性评价指标和方法,并基于河南电网侧储能电站示范工程进行案例分析,验证了方法的适用性和有效性。研究表明：考虑聚合效应的灵活性评价指标和方法能够有效地量化多点分布式储能系统响应系统不确定变化时的灵活调节能力,有助于提高储能电站调度运行的量化决策水平,具有一定的工程实用价值。     

齿墩数目对齿墩状内消能工消能效果的影响

为改善传统消能方式、底流消能方式、挑流消能方式带来的不利影响,选取面积收缩比相同(ε=0.5)而齿墩数目不同的4种试验方案,通过物理模型试验,分析了各方案下齿墩状内消能工的消能率、脉动压强和空化特性。结果表明,4种试验方案的消能率大致随齿墩数目的增加而降低,方案A的消能效果最佳;脉动压强系数沿程分布规律基本相同,脉动压强在齿墩段变化剧烈,脉动压强最大点均出现在齿墩段后约1.5 D(D为圆管直径)处,随后又迅速减小,并在距齿墩段4 D后逐渐恢复平稳状态;在试验研究范围内,当n3时脉动压强随齿墩数目的增加而增大,n=4时脉动压强最小,其抗空化性能最好;脉动压强概率密度分布基本近于正态分布。研究结果可为内消能工的工程应用提供依据。     

反应速率对层流扩散火焰特性的影响

为探究燃烧过程中火焰结构和烟黑特性的变化规律,对层流乙烯/空气扩散火焰进行了数值模拟,分析了不同成核过程和表面生长过程中,反应速率常数的指前因子及活化能对层流乙烯/空气扩散火焰温度和烟黑体积分数的影响。结果表明：成核反应速率常数中,指前因子增大,火焰温度降低,烟黑体积分数增大,当指前因子提高50%时,在轴向高度3 cm位置对应的火焰温度峰值减小0.70%,烟黑体积分数的峰值增大37.98%;活化能增加,火焰温度增大,烟黑体积分数减小,当活化能提高50%时,在轴向高度3 cm位置对应的火焰温度峰值增大3.41%,烟黑体积分数的峰值减小78.92%;表面生长反应速率常数中,指前因子增大,火焰温度逐渐减小,烟黑体积分数逐渐增大,当指前因子提高50%时,在轴向高度3 cm位置对应的火焰温度峰值减小2.03%,烟黑体积分数的峰值增大1.65倍;活化能增加,使火焰温度升高,烟黑体积分数减小,当活化能提高50%,在轴向高度3 cm位置对应的火焰温度峰值增大9.61%,当活化能提高12.5%,烟黑体积分数的峰值减小46.68%。     

Effect of various coal contaminants on the performance of solid oxide fuel cells: Part II. ppm and sub-ppm level testing

The poisoning effects of various trace contaminants in the coal-derived syngas stream at ppm and sub-ppm level on the performance of Ni-YSZ/YSZ/LSM solid oxide fuel cells were studied at extended duration. The thermochemical nature of impurities such as PH₃(g) and CH₃Cl(g) in presence and absence of water steam was analyzed by a high temperature mass spectrometer. Only less than half of PH₃(g) is hydrolyzed, and CH₃Cl(g) also co-exist with HCl(g). After a certain duration of exposure, 1 ppm AsH₃(g), 0.5 ppm PH₃(g), and 2.5 ppm CH₃Cl(g) all caused some degree of degradation to the power density at 750 °C. Whereas 1 ppm of H₂S(g) resulted in immediate performance loss. The mechanisms of degradation are mainly divided into two categories: surface adsorption effect (for S and Cl) and bulk reaction effect (for As and P). The controversies regarding the poisoning effect and mechanism of S are also discussed with the aid of thermodynamic equilibrium composition calculation.     

Effect of various coal gas contaminants on the performance of solid oxide fuel cells: Part III. Synergistic effects

The coal-derived gas from a coal gasifier contains multiple contaminants, and their synergistic effects may not be simply the additive influences of individual contaminants. The present work presents the results of a study of the synergistic effects of four contaminants of major concern—S, As, P, and Cl, at the ppm level and in combinations of two, three, or four kinds—on the performance of Ni-YSZ/YSZ/LSM solid oxide fuel cells. The results indicate that both cell performance and morphology differ significantly in cells exposed to a single contaminant, and that cell performance is not simply the additive influence of each contaminant. Synergistic effects can be very destructive (accelerated degradation or even cell failure) when S is in the presence with As/P, but can also be beneficial (stabilization in power density variations over time or a slowed degradation rate) when Cl is present with other contaminants. Cl can even partially restore performance loss when it is introduced after P is already present. Therefore, with the addition of Cl the tolerance limit of SOFCs for the other three contaminants can be greatly increased. We speculate that the affinity of the contaminants to Ni catalyst increases in the following order: As < P < Cl. The interactions between and among these contaminants and possible mechanisms for their destructive and beneficial synergistic effects are discussed.     

高压变频器在油田注水系统的应用及节能效果评价

介绍了油田注水站计量系统的结构和工作原理。对高压变频器应用于油田注水站后计量系统出现的问题进行了分析。分析结果认为：变频器输出电源的频率和相位与供电电源频率和相位不同步是造成计量系统产生故障的主要原因。介绍了注水站单机组运行模式和多机组运行模式下的节能效果评价方法和计算公式,并对评价计算公式进行了说明。     

Effect of NiO on organic framework functionalized ZnO nanoparticles for energy storage application

Functionalization of metal oxides nanomaterial by different organic and inorganic species could considerably enhance the electrochemical performance of a supercapacitor. Here, we have synthesized and functionalized ZnO nanoparticles (NPs) via organic compounds of E. cognate and then doped the synthesized nanomaterials by NiO following hydrothermal route involving the bioactive compounds. As synthesized ZnO@NiO was analyzed by field emission-scanning electron microscopy at nanoscale. The organic functional groups were delineated by X-ray photoelectron spectroscopy as well as by Fourier transform infrared spectroscopy. What is more, Tauc plot revealed drastically decreased band gap energy of ZnO@NiO to 2.48 eV resulting in an enhanced electrochemical properties. Therefore, organic framework derived ZnO@NiO nanomaterial was scrutinized as an electrode for supercapacitor by galvanostatic charge-discharge, cyclicvoltammetry and electrochemical impedance spectroscopy. ZnO@NiO electrode demonstrated specific capacitance of 185 Fg⁻¹ by cyclicvoltammetry, proposing its potential towards supercapacitor due to nanoscale particles and incorporated C, O, and N atoms of organic compounds.