太阳电池减反射膜系统的研究

减反射膜系的制备对于高效空间太阳电池来说非常重要,对其进行优化设计可以大幅度的提高太阳电池的短路电流,从而提高太阳电池的光电转换效率,从波动光学的基本原理出发,用加权平均反射率作为评价膜系设计质量的参数,编制出了进行减反射膜系优化设计的计算机程度,理论上可以使太阳电池表面的加权平均反射率降到1％以下,提高了电池的短路电路。     

多结太阳电池减反射膜的优化

基于多层膜的光学计算基本原理,模拟分析多结化合物太阳电池减反射膜的反射谱。模拟结果准确的反应了实际测量结果。以此为基础设计优化Ti O_x/Al_2O_3/MgF_2三层减反射膜,在GaInP/In_(0.01)GaAs/Ge三结太阳电池上实现了减反射膜对子电池响应电流的精确调节,并得到了子电池电流匹配的GaInP/In_(0.01)GaAs/Ge太阳电池,短路电流密度相比制备减反射膜前提升35.84%。     

太阳电池减反射膜的最佳光学匹配

本文对吸收系数大的半导体太阳电池,导出了单层减反射膜的最佳光学匹配条件,设计时必须考虑τ(λ)对膜厚、折射率和匹配中心波长的影响。     

AlxGa1—xAs／GaAs太阳电池减反射膜的研究

以太阳电池的短路电流积分表达式为依据，应用减反射膜的光学原理，对具有阳极氧化、ＳｉＯ和ＳｉＯ２三种减反射膜的ＡｌｘＧａ１－２Ａｓ／ＧａＡｓ太阳电池分别进行了反射光谱、短路电流、开路电压的实验测试。研究表明，阳极氧化膜、ＳｉＯ膜具有良好的减反射性能，而ＳｉＯ２膜的减反射性能较差。     

用于太阳电池的SiO2增透膜的制备及性能研究

用溶胶-凝胶及酸碱两步催化法制备出SiO_2溶胶,采用提拉法在太阳电池组件玻璃上制备SiO_2薄膜,进行表面修饰使其具有良好的疏水性,接触角由修饰前的40°提高到107°。设计并制备出在400～800nm波段平均透过率增加5%以上的大面积减反射膜。疏水性耐磨性都可以达到工业化生产的要求。     

硅太阳电池用UV/IR截止滤光膜系设计

根据光学薄膜原理,编制出计算机程序。在太阳电池封装玻璃的上、下表面分别设计出红外(IR)截止的带通滤光膜系A|[1.05(LMHML)](LMHML)6[1.15(LMHML)]1.15L| G和紫外(UV)截止的带通滤光膜系G|H/2LH/2|7s。透射曲线表明:这两种带通滤光膜系对于不同波长的光有着很好的选择性透射,IR截止滤光膜系能够使波长大于1120nm的大部分光在到达电池表面前就被反射,UV截止滤光膜系能够使得波长小于350nm的光在到达电池表面前几乎全部被反射掉。同时,350nm<λ<1120nm的光的入射几乎不受影响,加权平均透射率为97.49%。     

基于Matlab软件SiN_x/Si0_2叠层减反射膜厚度优化的研究

SiN_x/SiO_2叠层膜作为减反射钝化膜在高效太阳电池中具有广泛的应用。本文采用光学导纳特征矩阵法,利用Matlab软件对SiN_x/SiO_2叠层膜的减反射效果进行系统理论研究。首次将AM1.5G光谱、透过叠层膜到达硅片表面光子数作为衡量标准,进行减反射膜的厚度优化研究。结果表明,优化后SiN_x/SiO_2叠层膜厚度为70nm+20nm时,透过叠层膜到达硅片表面光子数最多,达到2.618×10~(17)(1/s·cm~2)。     

减反射膜玻璃对光伏组件光增益的分析

完善光伏组件光学模型,并根据模型理论模拟减反射膜玻璃和普通玻璃对光伏组件光增益的大小,通过分析发现当太阳光垂直光伏组件入射时,普通玻璃封装后,单晶硅太阳电池封装后光增益小于多晶硅太阳电池,减反射玻璃对多晶硅太阳电池片的光增益大于对单晶硅太阳电池的光增益。     

AlxGa1-xAs/GaAs太阳电池MgF2/ZnS双层减反射膜的研究

介绍了在AlxGa1-xAs/GaAs太阳电池上制备MgF2/ZnS双层减反射膜的研究工作,引入了有效反射率R,并通过使Re极小来实现减反射膜的优化设计,考虑了MgF2/ZnS双层减反射膜与窗口层的耦合,实验上获得了良好的减反射膜,提高了AlxGa1-xAs/GaAs太阳电池的短路电流和效率,表明用Re极小化来设计减反射膜是合理的。     

低温生长SiO2钝化膜在太阳电池上的应用

主要研究在晶体硅衬底上采用干氧氧化法生长SiO2薄膜,通过改变非晶SiO2薄膜的生长温度、时间以及气体流量等参数优化工艺条件,增强对硅片的钝化作用,提高光生少数载流子寿命.实验发现在840℃下生长的非晶SiO2薄膜对硅片钝化效果最佳,可将硅片少子寿命提高约90%.此外,为优化SiO2/SiNx双层膜的减反射作用,采用Matlab程序计算SiO2/SiNx双层膜的反射谱,从理论上获得最优的膜系组合.实验发现生长有SiO2钝化膜的SiO2/SiNx双层膜太阳电池相对单层SiNx膜太阳电池,短路电流和开路电压分别提高了0.2A和8mV,转换效率提高约9%.     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Contents in Volume 23,2014

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Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.