Computer-aided design of PV/wind hybrid system

A complete set of match calculation methods for optimum sizing of PV/wind hybrid system is presented. In this method, the more accurate and practical mathematic models for characterizing PV module, wind generator and battery are adopted; combining with hourly measured meteorologic data and load data, the performance of a PV/wind hybrid system is determined on a hourly basis; by fixing the capacity of wind generators, the whole year's LPSP (loss of power supply probability) values of PV/wind hybrid systems with different capacity of PV array and battery bank are calculated, then the trade-off curve between battery bank and PV array capacity is drawn for the given LPSP value; the optimum configuration which can meet the energy demand with the minimum cost can be found by drawing a tangent to the trade-off curve with the slope representing the relationship between cost of PV module and that of the battery. According to this match calculation method, a set of match calculation programs for optimum sizing of PV/wind hybrid systems have been developed. Applying these match calculation programs to an assumed PV/wind hybrid system to be installed at Waglan island of Hong Kong, the optimum configuration and its hourly, daily, monthly and yearly performances are given. (C) 2003 Elsevier Science Ltd. All rights reserved.

A Multimoment Finite-Volume Shallow-Water Model On The Yin-Yang Overset Spherical Grid

A numerical model for shallow-water equations has been built and tested on the Yin-Yang overset spherical grid. A high-order multimoment finite-volume method is used for the spatial discretization in which two kinds of so-called moments of the physical field [i.e., the volume integrated average ( VIA) and the point value (PV)] are treated as the model variables and updated separately in time. In the present model, the PV is computed by the semi-implicit semi-Lagrangian formulation, whereas the VIA is predicted in time via a flux-based finite-volume method and is numerically conserved on each component grid. The concept of including an extra moment (i.e., the volume-integrated value) to enforce the numerical conservativeness provides a general methodology and applies to the existing semi-implicit semi-Lagrangian formulations. Based on both VIA and PV, the high-order interpolation reconstruction can only be done over a single grid cell, which then minimizes the overlapping zone between the Yin and Yang components and effectively reduces the numerical errors introduced in the interpolation required to communicate the data between the two components. The present model completely gets around the singularity and grid convergence in the polar regions of the conventional longitude-latitude grid. Being an issue demanding further investigation, the high-order interpolation across the overlapping region of the Yin-Yang grid in the current model does not rigorously guarantee the numerical conservativeness. Nevertheless, these numerical tests show that the global conservation error in the present model is negligibly small. The model has competitive accuracy and efficiency.

Shallow Water Model On Cubed-Sphere By Multi-Moment Finite Volume Method

A global numerical model for shallow water flows on the cubed-sphere grid is proposed in this paper. The model is constructed by using the constrained interpolation profile/multi-moment finite volume method (CIP/MM FVM). Two kinds of moments, i.e. the point value (PV) and the volume-integrated average (VIA) are defined and independently updated in the present model by different numerical formulations. The Lax-Friedrichs upwind splitting is used to update the PV moment in terms of a derivative Riemann problem, and a finite volume formulation derived by integrating the governing equations over each mesh element is used to predict the VIA moment. The cubed-sphere grid is applied to get around the polar singularity and to obtain uniform grid spacing for a spherical geometry. Highly localized reconstruction in CIP/MM FVM is well suited for the cubed-sphere grid, especially in dealing with the discontinuity in the coordinates between different patches. The mass conservation is completely achieved over the whole globe. The numerical model has been verified by Williamson's standard test set for shallow water equation model on sphere. The results reveal that the present model is competitive to most existing ones. (C) 2008 Elsevier Inc. All rights reserved.

A study on the minority carrier diffusion length in n-type GaN films

The minority carrier diffusion length of n-type GaN films grown by metalorganic chemical vapor deposition (MOCVD) has been studied by measuring the surface photovoltaic (PV) spectra. It was found that the minority carrier diffusion length of undoped n-type GaN is considerably larger than that in lightly Si-doped GaN. However, the data suggested that the dislocation and electron concentration appear not to be responsible for the minority carrier diffusion length. It is suggested that Si doping plays an important role in decreasing the minority carrier diffusion length.

Optical investigation on the annealing effect and its mechanism of GaInAs/GaNAs quantum wells

Thermal annealing of GaInAs/GaNAs quantum wells (QWs) as well as other nitrogen- and indium-contained QW structures grown by molecular beam epitaxy and its effect on optical properties are investigated. The photoluminescence (PL) and photovoltaic (PV) spectra of annealed GaInAs/GaNAs QWs show that the luminescence properties become degraded due to the N diffusion from the GaNAs barrier layers to the GaInAs well layer. Meantime, the annealing-induced blueshift of the PL peak in this QW system is mainly induced by the change of In distribution, suggesting that the In reorganization is greatly assisted by the N-induced defects. The elucidation of annealing effect in GaInAs/GaNAs QW samples is helpful for a better understanding to the annealing effect in the GaInNAs/GaAs QWs. (C) 2003 Elsevier Science B.V. All rights reserved.

Calculation of the hourly and daily radiation incident on three step tracking planes

Mathematical formulas for estimating the hourly and daily radiation incident on planes of azimuth three step tracking and hour angle three step tracking have been derived in this paper. Based on the hourly solar radiation data of an average day in each month at Er-Lian-Hao-Te city, the hourly and monthly radiation received by planes of these two kinds of tracking have been calculated. The results show that in this district, one axis azimuth three step tracking and hour angle three step tracking could, respectively, obtain 66.5% and 63.3% higher radiation than that on the horizontal surface all year. Moreover, a two axis azimuth three step tracking plane could receive 72% more radiation than the horizontal surface. (C) 2002 Elsevier Science Ltd. All rights reserved.

Photovoltage and luminescence study of stacked InAs/GaAs self-organized quantum dots

The ground and excited state excitonic transitions of stacked InAs self-organized quantum dots (QDs) in a laser diode structure are studied. The interband absorption transitions of QDs are investigated by non-destructive PV spectra, indicating that the strongest absorption is related to the excited states with a high density and coincides with the photon energy of lasing emission. The temperature and excitation (electric injection) intensity dependences of photoluminescence and electroluminescence indicate the influence of state filling effect on the luminescence of threefold stacked QDs. The results indicate that different coupling channels exist between electronic states in both vertical and lateral directions.

The investigations on semi-insulating GaAs by surface photovoltaic spectroscopy

The surface photovoltage (SPV) effect induced by the defect states in semi-insulating (SI) GaAs was studied. The PV response below the band edge was measured at room temperature with a de optical biasing. The spectra were found to be strongly dependent on the surface recombination and were attributed to formation of the carrier concentration gradient near the surface region, showing that SPV is a very sensitive and nondestructive technique for characterizing the surface quality of the SI-GaAs wafers.

Structural and photoelectric studies on double barrier quantum well infrared detectors

GaAs/AlAs/GaAlAs double barrier quantum well (DBQW) structures are employed for making 3-5 um photovoltaic infrared (IR) detectors with a peak detectivity of 5 x 10(11) cm Hz(1/2)/W at 80 K. Double crystal X-ray diffraction is combined with synchrotron radiation X-ray analysis to determine successfully the exact thickness of GaAs, AlAs and GaAlAs sublayers. The interband photovoltaic (PV) spectra of the linear array of the detectors are measured directly by edge excitation method, providing the information about spatial separation processes of photogenerated carriers in the multiquantum wells and the distribution of built-in field in the active region. The spectral response of the IR photocurrent of the devices is also measured and compared with the temperature dependent IR absorption of the DBQW samples in order to get a better understanding of the bias-controlled optical and transport behavior of the detector photoresponse and thus to optimize the detector performance. (C) 1999 Elsevier Science Ltd. All rights reserved.

Photovoltage and photoreflectance spectroscopy of InAs/GaAs self-organized quantum dots

We present a detailed study of the interband excitonic transitions of InAs/GaAs self-organized quantum dots (QDs) based on photovoltage (PV) photoreflectance (PR) and photoluminescence (PL) spectroscopy. At room temperature, the interband absorption transitions of QDs have been observed by using PV spectrum, which clearly exhibits four well-resolved excitonic absorption peaks. The absorption line shape is Gaussian-like. Furthermore, the corresponding excitonic transitions are also observed in PR experiment at 77 K. The first derivative of a Gaussian profile can fit the experimental data well. (C) 1998 American Institute of Physics. [S0003-6951(98)00743-8]

双面太阳电池垂直安装发电性能的测试

双面太阳电池是一种非常规太阳电池。本文通过建立光伏组件-控制器-蓄电池-负载试验系统，对日立公司双面受光单晶硅太阳电池组件分别在东西和南北朝向情况下垂直地面安装时的功率输出特性进行了测试和分析。根据应用测试结果，总结了双面受光太阳电池的应用优缺点和可能的应用方式。

聚酰亚胺膜用于醇/醚混合物的分离

采用渗透汽化（PV���或蒸汽渗透（VP）膜过程分离共沸、近沸、同分异构以及热敏感性液体混合物的研究工作已经开展许多年了。同传统严重耗能的分离技术相比（如萃取或者共沸精馏），Pv���VP无论从节能、安全还是环境友好方面看，都是一个非常有前景的新技术。PV���VP也是一种"清洁"的技术。它特别适合于处理含有挥发性有机组份的混合物。目前PV���VP的方向可以分成三个：（l）水一有机混合物的脱水；（2）从水溶液中脱除挥发性有机物；（3）有机一有机溶剂混合物的分离[1]。PV���一个里程碑式的工作是1982年GFT公司（现属SulzerChemtech公司）利用亲水材料聚乙烯醇（PVA）在巴西建成了第一个乙醇脱水的工业化膜装置。至今在全世界已经建立了100多套Pv���业装置（90％是GFT公司提供的膜和技术）。多数用于有机溶剂的脱水，包括乙醇脱水、异丙醇脱水以及酷类、醚类和其它有机溶剂的脱水。现在PV���研究热点己经不是亲水膜了，而是亲有机溶剂的膜。这方面的研究是非常活跃的。但是与之呈鲜明对比的是没有什么大的工业化技术。值得提及的是1991年AlrProducts公司建成了膜法分离甲醇一MTBE的工厂。这个成功激励人们进一步研究那些汽一液平衡差的有机混合物的分离。目前PV���遍存在的主要问题是通量较低，这是阻碍Pv���一步工业化的关键。而这个问题的根源在于缺少具备耐溶剂的聚合物膜材料。膜材料问题又表现在两个方面：一个是设计并合成出新的高性能膜材料，另外是筛选出具备高渗透性能与稳定性兼备的膜材料。事实上，经过二十多年的研究，针对PV���经开发出许多新，的聚合物膜材料了。但似乎合成新材料的热情并没有因此而降温。开发新材料仍旧是聚合物膜领域的一个重要问题。对现有材料进行改性研究已经成为材料设计的一个重要方面。由于PV���离膜对体系的针对性非常强，为特定体系筛选材料就成为一个关键问题。筛选材料又涉及到构造膜材料结构与渗透性能关系的理论【3］。目前这方面的工作还很不完善。VP是将有机溶剂在蒸汽状态下进行分离的较新膜过程。近10年来VP技术工业化的步伐很快，这主要得益于PV���术在工业应用中所积累的经验与知识。1989年9月德国Heilbronn的Bruggem～公司设计并投入运行了世界上第一套工业规模的VP装置，接下来有许多VP装置在世界各地建立起来。在无水乙醇生产中，二者操作成本相似，但VP法比PV���节省设备投资费用，因而总成本也比较低。另外，VP过程还特别适合于从空气或其它气体中去除挥发性有机污染物，并回收有用物质。如石油化工中回收乙烯、丙烯、氯乙烯单体；天然气生产中去除C3以上碳氢化合物，及HZS、C02等酸性气体；空气中可挥发性有机物，如氯甲烷、丙酮、庚烷等［2］。实际上，从己经工业化的技术上看，单纯应用PV���VP进行有机混合物的分离不是最佳的选择。采用PV���VP与蒸馏过程祸合的方法常常是最经济的，因为藕合过程可以利用原有的精馏设备。这不仅有利于节省设备的投资，而且可以节约操作费用。尽管利用PV���VP分离有机一有机混合物的商业前景是非常广阔的，但是这个领域的发展却最缓慢。现在看来，主要问题是研究者在表征与开发单一成分的膜材料（比如聚合物材料与无机材料）方面花费了太多的时间与精力。因为单一材料的分离性能也许注定不能成功。正像聚合物材料在气体分离方面存在透过性与选择性相互制约的Robeson上限那样，在有机混合物分离方面也应该存在类似的关系。但人们常常是被迫才承认这些让人不愉快的极限定律。本论文采用长春应化所自主合成的一种可溶性聚酞亚胺（HQDPA-DMMDA）为基本膜材料，进行有机混合物的分离研究。开展了三方面的工作：一个方面是表征这种聚合物膜对醇一醚（主要是甲醇-MTBE）混合物的分离，包括对材料进行共混改性、杂化改性等研究。第二个方面是针对"溶解一扩散"理论及实验上存在的一个基本问题，发明了一种测定有机溶剂在聚合物膜内形成团簇尺寸的新方法。第三个方面是将气体分离中有关自由体积理论引入到"有机溶剂一聚合物"体系中，解释其溶胀、吸附行为。论文的第一章将介绍己经研究的和工业化的有机一有机混合物体系及膜材料的状况。第二章将介绍与PV���VP有关的较新理论。第三章将介绍两种表征聚合物及测定聚合物一溶剂相互作用的新方法。第四章将介绍与本论文有关的实验背景。第五章是关于聚酞亚胺膜材料用于甲醇-MTBE分离的表征与改性研究的工作。第六、七、八、九章是关于分离机理的研究工作。

金属原卟啉的电化学聚合以及氧在其上的电催化还原

氧的电还原不仅在高效能量转换和储存装置中，而且在电解工业中降低电耗方面也起着重要的作用。为此寻求催化活性好、稳定性高和经济适用的氧还原催化剂是一个十分重要的课题。许多研究工作者已发现卟啉、酞菁一类过渡金属大环络合物对氧的催化还原有很高活性，但是其稳定性差。为提高催化剂的稳定性，人们进行了多种尝试，如真空沉积、热处理、将活性单体嵌入Nafion膜或导电高聚物膜中等，但都未能很好解决稳定性问题。我们试图将活性单体用电化学方法直接聚合在电极基底上，以提高催化剂的稳定性。为此，本论文主要进行了以下工作：（1）活性单体的合成，（2）钴原卟啉二甲酯(CoPP)的电化学聚合，以及（3）氧在聚CoPP膜上电还原的活性、稳定性和机理等的研究。一、通过实验摸索出一条由血红素单体合成CoPP单体的简便途径。二、研究了高聚物膜的电化学聚合和表征，以及膜在水溶液中的电化学行为。用循环伏安法(C.V.)和恒电位(P. S.)方法研究了CoPP单体直接聚合在不同的电极基底[如玻璃碳(GC)、烧结石墨(Pc)、导电玻璃和Pt等]上的条件。发现C.V.图上有三对氧化还原峰。在聚合的过程中，中断所旋加的电位时，聚合电量继续增加。找到了若干种能溶能聚CoPP膜的有机溶剂和水溶液，并对高聚物膜进行了红外、紫外表征，发现聚CoPP膜的紫外吸收红移不大，CoPP单体在聚合中，卟啉环上的一个乙烯基被饱和，卟啉环没有被破坏，在聚CoPP膜中，每个卟啉环中仍存在由四氦围绕着的中心金属。扫描电镜结果表明：高电位下聚合膜的空隙，比低电位下聚合膜的多，由此提出了阳离子自由基的聚合机理。此外我们还发现在酸性溶液中，能观察到明显的中心金属离子的氧化还原峰。三、氧在聚CoPP膜上电催化还原的研究 用RDE（旋转盘电极）方法比较了氧在聚CoPP/GC与吸附CoPP单体/GC上的电还原，发现聚CoPP膜的活性和稳定性都比吸附单体的高。聚合电位影响高聚物膜的稳定性。高聚物膜越厚，稳定性越好，并且随溶液pH值的降低而增大。高聚物膜厚度与其活性关系之间存在一个最佳值，低于或高于此值，其活性降低。在一定厚度范围内，氧电还原的Tafel斜率基本不变；其动力学反应常数(Kf)与电极表面上有效活性中心浓度(Pv')和乘积(Kf·Pv')随膜厚度的增加而降低。用RDE方法研究溶液pH值的影响时发现，在较宽的pH值范围内，聚CoPP/GC主要催化氧为二电子还原。聚CoPP膜的活性随溶液pH值的降低而增大。在低极化区内，氧在碱性溶液中或中性溶液中的电还原与OH~-浓度无关，而在酸性溶液中，H~+浓度有影响；在高极化区内，溶液pH值影响很小。RRDE（旋转环盘电极）的研究结果表明，在一定的电位范围内，氧在聚CoPP/PC上电还原的主要产物为H_2O_2，H_2O_2一但在盘电极上生成，就不再进一步还原，并同时体随有少量氧按四电子途径还原。若电位在很负的情况下，在盘上生成的H_2O_2能够进一步还原。根据以上的实验现象及结果我们提出了氧在聚CoPP膜上电催化还原的二电子还原机理、四电子还原机理和四电子的串联还原机理，并对上述实验现象的结果给予了一定的解释。

几种硫属化合物半导体的电化学与光电化学研究

本文分别用恒电位电沉积和恒电位脉冲电沉积技术在ITO基底上成功地沉积出表面平滑均匀、与基底附着牢固、具有一定光活性的CdS多晶薄膜。系统地考察了CdS薄膜的电性质、光性质及光电化学行为。用电沉积技术在不同基底（Ni、Ti、ITO）上成功地实现了Hg_(1-X)Cd_xTe(MCT)的三元共沉积。初步组装了P-Hg_(1-X)Cd_xTe/n-CdS异质结PV���。研究了层状结构材料n-InSe的PEC行为并考察了多种单晶材料，诸如CdS、CdTe、CdSe、InSe等的光阳极特性和界面行为。