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分析传输线模型(TLM)法在接触电阻测量中的缺陷,通过建立金属-半导体界面的电压、电流方程推导出不同电流模式下接触电阻的表达式,在TLM法的基础上提出新的测量方法,可精确测量电极与硅体的比接触电阻率和接触界面的薄层方块电阻,从而准确计算出太阳电池接触电阻。该方法测量方便、计算结果精确,可有效应用于晶体硅太阳电池接触电阻的研究。 相似文献
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晶体硅太阳电池扩散工艺研究 总被引:2,自引:0,他引:2
作为晶体硅太阳电池制作的心脏环节,扩散的效果也就是扩散后方块电阻的均匀性显得尤为重要。影响方块电阻均匀性的主要因素有:大小氮的流量、O2的流量、通源时间、再分布时间和中心温度。通过逐一改变这些因素,分析所得数据,得到一个能有效控制方块电阻大小、使方块电阻均匀性达到最佳的规律:大小氮流量的变化共同影响方块电阻均匀性;方块电阻大小的改变主要靠温度、时间、小氮的流量的改变来调节。通过以上实验规律的研究,便于常规工艺的调试和高方块电阻工艺中高方块电阻的制备和极差的优化。 相似文献
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《太阳能》2020,(9)
在现阶段主流太阳电池生产设备的水平条件下,研究了激光频率、初始方块电阻和烧结峰值温度对基于激光掺杂的选择性发射极(SE)+PERC单晶硅太阳电池电性能的影响。分别采用奥林巴斯显微镜和Halm电学性能测试仪,分析了不同频率的激光在硅片表面形成的光斑形貌,以及不同实验条件时电池的电性能变化趋势。结果表明,激光频率为220 kHz时有利于在硅片表面形成连续性且不重叠的光斑,形成最佳重掺杂区,从而提升电池转换效率;基于现有的常压扩散设备的掺杂水平,在确保硅片表面方块电阻均匀性的情况下,初始方块电阻选择120Ω/□更有利于提升电池的转换效率;烧结峰值温度为790℃时,更有利于在电池电极位置形成良好的欧姆接触,从而获得最佳的电池转换效率。 相似文献
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研究ITO/Metal/ITO(IMI)电极中金属层Cu和Ag及其厚度对电极光电性能的影响,结合霍尔测试、紫外分光光度计、原子力显微镜等分析金属层材料和厚度对IMI电极光电性能以及形貌的影响。通过优化金属层厚度,获得方阻分别为11.2 Ω/□和14.5 Ω/□且400~800 nm波长范围内平均透过率分别为93.9%和86.5%的ITO/Ag/ITO和ITO/Cu/ITO电极。将IAI和ICI电极作为正面电极应用于钙钛矿太阳电池,太阳电池的填充因子从62.5%提升至78.0%。IMI在短波段的较大反射率会导致电池短路电流密度低1~2 mA/cm2。当Cu层和Ag层的厚度分别为7.4 nm和6.4 nm时,钙钛矿太阳电池的效率达到最佳。 相似文献
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利用化学气相沉积法,成功地制备了掺Sb的SnO_2织构膜,并对其电学、光学和结构特性,以及它们与工艺参数的关系进行了分析研究。在最佳工艺条件下,这种膜的方块电阻达10Ω/,直射透过率约为80%(波长800nm)。在这种织构膜上制作的a-Si 太阳电池,其开路电压和短路电流明显地高于在光面ITO/SnO_2复合膜上制作的电池。 相似文献
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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. 相似文献
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《热能动力工程》2014,(5)
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%. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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. σred = σ1 β + (1 − β)σi, where: σ1-maximal principal stress, σi-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. 相似文献
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Jaime Massanet-Nicolau Alan Guwy Richard Dinsdale Giuliano Premier Sandra Esteves 《International Journal of Hydrogen Energy》2010
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. 相似文献