光学与太阳能

开发资源丰富、可再生,清洁的新能源是全球一项紧迫的战略任务.在概述现有能源技术的基础上,从光学和光学技术角度重点对太阳能的直接利用、太阳能电池以及太阳能分解水制氰进行了分析.指出了利用简单有效的太阳能跟踪聚焦系统,以及耐热、低损耗、低成本和宽光谱传输的空芯塑料光纤,可以加大对太阳能的直接利用和普及推广;在太阳能电池方面,应重点研究和发展各种薄膜太阳能电池,采用对可见、紫外和红外光谱吸收的、具有不同带隙的复合材料和采用多结器件,以进一步提高电池的转换效率和降低成本;在太阳能分解水制氢方面,应该把直射到地球表面的、从紫外-可见-红外的宽太阳光谱,利用空腔辐射器作一个变换,转换成绝大部分位于水分子有强烈吸收带的红外区.同时利用催化剂(敏化剂),对水进行红外光催化分解反应,或者利用红外多光子离解这有可能取得工业化规模制氢的突破.     

Review of proton conductors for hydrogen separation

There is a global push to develop a range of hydrogen technologies for timely adoption of the hydrogen economy. This is critical in view of the depleting oil reserves and looming transport fuel shortage, global warming, and increasing pollution. Molecular hydrogen (H₂) can be generated by a number of renewable and fossil-fuel-based resources. However, given the high cost of H₂ generation by renewable energy at this stage, fossil or carbon fuels are likely to meet the short- to medium-term demand for hydrogen. In view of this, effective technologies are required for the separation of H₂ from a gas feed (by-products of coal or bio-mass gasification plants, or gases from fossil fuel partial oxidation or reforming) consisting mainly of H₂ and CO₂ with small quantities of other gases such as CH₄, CO, H₂O, and traces of sulphur compounds. Several technologies are under development for hydrogen separation. One such technology is based on ion transport membranes, which conduct protons or both protons and electrons. Although these materials have been considered for other applications, such as gas sensors, fuel cells and water electrolysis, the interest in their use as gas separation membranes has developed only recently. In this paper, various classes of proton-conducting materials have been reviewed with specific emphasis on their potential use as H₂ separation membranes in the industrial processes of coal gasification, natural gas reforming, methanol reforming and the water–gas shift (WGS) reaction. Key material requirements for their use in these applications have been discussed.     

Implementation of focused ion beam (FIB) system in characterization of nuclear fuels and materials

Beginning in 2007, a program was established at the Idaho National Laboratory to update key capabilities enabling microstructural and micro-chemical characterization of highly irradiated and/or radiologically contaminated nuclear fuels and materials at scales that previously had not been achieved for these types of materials. Such materials typically cannot be contact handled and pose unique hazards to instrument operators, facilities, and associated personnel. Over the ensuing years, techniques have been developed and operational experience gained that has enabled significant advancement in the ability to characterize a variety of fuel types including metallic, ceramic, and coated particle fuels, obtaining insights into in-reactor degradation phenomena not achievable by any other means. The following article describes insights gained, challenges encountered, and provides examples of unique results obtained in adapting dual beam FIB technology to nuclear fuels characterization.     

Stability issues of the next generation solar cells

Polymer, perovskite, and dye‐sensitized solar cells (DSSCs) are promising technologies for next generation low cost photovoltaic cells. Among these, perovskite solar cells are the newest technology and have the highest efficiency, while DSSCs are closest to commercialization with several companies producing the DSSC materials and modules and existing DSSC installations. However, all three types of solar cells share a concern about lifetime and stability. For each type of devices, there are specific concerns and degradation mechanisms, and all of the devices require encapsulation and exhibit varying degrees of sensitivity to moisture, oxygen, elevated temperature and UV illumination depending on the device structure and materials used. We are discussing the stability and lifetime for each type of cells and future outlook of these technologies. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

浅谈惯性约束核聚变

以煤、石油、天然气为代表的化石能源终将枯竭,基于核裂变反应的核裂变能源也由于安全性和核废料的处理等问题而不尽如人意。     

聚光光伏系统

随着传统化石类能源的枯竭和环境污染的日益严重,太阳能光伏发电技术倍受瞩目,但较高的发电成本及原材料的缺乏制约了其大规模发展.以高转换效率、低芯片消耗为核心的聚光光伏技术,在降低光伏发电成本方面被人们寄予厚望.文章主要介绍了聚光光伏系统发展的历史和现状,工作原理及存在的关键问题,并对其发展前景进行了展望.     

Establishment of a set of skeletal oxidation mechanisms for mono-alkylated cyclohexanes with consistent structure

As a major chemical class of fossil fuels, mono-alkylated cyclohexanes are frequently employed to construct the surrogate fuels of fossil fuels. Much effort has been made to study the oxidation behavior of mono-alkylated cyclohexanes, but reduced/skeletal mechanisms suitable for multi-dimensional combustion simulations are still scarce. In this work, a set of skeletal models for mono-alkylated cyclohexanes from methyl-cyclohexane (MCH) to octyl-cyclohexane (n-OTCH) were built and deduced by integrating the decoupling methodology and reaction rate rules. The development process contains two parts, i.e., the skeletal model establishment for the base fuel and the skeletal model deduction for other fuels utilizing the reaction rate rules. For mono-alkylated cyclohexanes, the reactions in the fuel-relevant sub-model also dominate the laminar flame speed, apart from the C₀–C₃ sub-model, which differs from that of n-alkanes. To well capture the flame propagation behavior, the local sensitivity analysis on the comprehensive mechanism was introduced. For each mono-alkylated cyclohexane, the skeletal model includes 52 species and 216 reactions. The final skeletal models were validated against extensive experimental measurements in jet-stirred reactors, shock tubes, rapid compression machines, and premixed flames over wide operating conditions. Satisfactory agreements between the observed data and simulated results are achieved, which indicates the practicability of the proposed method.     

An experimental and kinetic modeling study of auto-ignition and flame propagation of ethyl lactate/air mixtures,a potential octane booster

Spark ignition engines are one of the main technologies in the transport sector. The improvement and optimization of the fuels used to empower these engines are of vital importance, both for economic and environmental reasons. In particular, one of the main issues of spark ignition engines is the knock phenomenon; new formulations of fuels are being studied in order to overcome this problem. In this study, a possible innovative anti-knock, octane booster additive is considered: ethyl lactate. This molecule is almost unknown in combustion literature, as it has been used only as green solvent and food additive. The first experimental results under combustion conditions are presented, together with a kinetic mechanism. Two set-ups have been employed: a rapid compression machine, to measure ignition delay times, and an innovative spherical bomb, OPTIPRIME, to obtain laminar flame speeds. The results are encouraging for the expected application and the mechanism shows good performance. Ignition delay times at all conditions are well predicted by the mechanism and, when compared to ethanol, they are longer, implying a greater anti-knock capability. A rate of production analysis has been performed, where the unimolecular reaction leading to ethylene and lactic acid has been proved to be quite important at high temperatures and lean conditions. For laminar flame speeds, the agreement between model and experiments is good, with some discrepancies at lean conditions and high pressures. Compared to ethanol, at rich and stoichiometric conditions ethyl lactate flame speeds are slightly slower except at lean conditions, indicating that under some conditions this molecule could provide better performances than ethanol as an octane booster additive.     

Chemical-looping combustion: Status and research needs

Chemical-Looping Combustion (CLC) has emerged in recent years as a very promising combustion technology for power plants and industrial applications with inherent CO₂ capture, which circumvent the energy penalty imposed on other competing technologies. The process is based on the use of a metal oxide to transport the oxygen needed for combustion in order to prevent direct contact between the fuel and air. CLC is performed in two interconnected reactors, and the CO₂ separation inherent to the process practically eliminates the energy penalty associated with gas separation. The CLC process was initially developed for gaseous fuels, and its application was subsequently extended to solid fuels. The process has been demonstrated in units of different size, from bench scale to MW-scale pilot plants, burning natural gas, syngas, coal and biomass, and using ores and synthetic materials as oxygen-carriers.An overview of the status of the process, starting with the fundamentals and considering the main experimental results and characteristics of process performance, is made both for gaseous and solid fuels. Process modelling of the system for solid and gaseous fuels is also analysed. The main research needs and challenges both for gaseous and solid fuel are highlighted.     

熔融盐循环热载体无烟燃烧体系的选择

介绍了一种全新的燃烧系统-熔融盐循环热载体无烟燃烧技术。本技术将燃料与助燃空气的燃烧分为氧化剂的生成和燃料与氧化剂接触反应两个过程。并且这两个阶段通常在两个反应室中进行,在氧化剂生成室,空气中的氧全部被氧载体吸收,剩余的高纯度氮气则被回收利用;在燃烧室,氧载体把自身的一部分或全部氧传递给燃料,完成燃烧过程。在燃烧室中,若燃料完全反应,那么只有高纯度的CO2生成,也可以直接回收用作化工原料。因为N2从燃烧系统中分离出去,且硫和重金属元素被熔融盐吸收而不被烧掉,所以燃烧过程没有NOx、 CO2、和SO2等污染物的排放。本文对几个典型的无烟燃烧系统进行了分析,并与传统燃烧过程进行了比较,对熔融盐循环热载体无烟燃烧体系的选择具有指导意义。     

三维多孔复合碳层对电极的制备及其光伏性能研究

基于TiO_2光阳极、Pt对电极的染料敏化太阳能电池(DSSC)因其优异的光电转换特性受到了广泛的关注,然而Pt昂贵的价格制约了其发展与应用.针对这一问题,本文设计、制备了一种由相对致密且高导电的石墨膜(PC层,底层)及多孔碳纳米颗粒膜(CC层,顶层)构成的低成本、高性能三维多孔复合碳层对电极.基于该CC/PC对电极的DSSC具有优异的光伏性能:在1.5标准太阳光照射下,其填充因子高达65.28%(较Pt对电极高4.1%)、光电转换效率高达5.9%(为Pt对电极的94.2%). CC/PC对电极的优异光伏性能主要归因于其独特的三维多孔导电结构,该结构有极高的比表面积和丰富的催化反应活性位,有利于电子的快速传输及离子的快速转移,在这些因素的协同作用下,其光电转换性能大大改善.     

Polymer electrolyte for photoelectrochemical cell and dye-sensitized solar cell: a brief review

This paper reviews the use of solid polymeric electrolyte (SPE) and gel polymeric electrolyte (GPE) in photoelectrochemical cell (PEC) and dye-sensitized solar cell (DSSC). The structure of PEC and its working principle are presented. The various types of polymer electrolytes utilized in PEC and DSSC have been highlighted in this review. It also highlights the comparison of performance of PEC and DSSC utilizing those polymer electrolytes. This review is completed with the list of other SPEs that potentially be tested in DSSC.     

Hydrogen enrichment enhances soot formation in swirl-stabilized non-premixed turbulent combustion of ethylene in a model gas turbine combustor

A switch from fossil fuels to hydrogen is currently not feasible mostly due to supply and infrastructure issues. One of the possible approaches, and this is now practiced to a limited extent in industrial gas turbines, is to blend relatively small amounts of hydrogen with fossil fuels curbing the carbon dioxide emissions. However, studies assessing the influence of modest amounts of hydrogen blending with hydrocarbon fuels on soot processes yielded contradictory results. Most of these experimental and numerical studies were performed on laminar diffusion flames and studies on turbulent flames are scarce. One of the confounding factors in assessing the influence of hydrogen is selection of a control experiment in which the fossil fuel is blended with the same amount of an inert diluent. Using helium in the control experiment is preferable because of its similar transport properties and heat capacity to those of hydrogen. Hence, we studied the soot processes in a model gas turbine combustor in which the flame is stabilized by an air swirl. Swirl-stabilized platform ensures that with and without hydrogen/helium dilution, the hydrodynamics of the combustor stays fixed. Base fuel ethylene is supplemented with hydrogen or helium by the same amount to separate the dilution affects and assess the direct chemical interaction of hydrogen related to soot formation. Soot volume fraction and primary soot particle diameters were measured by auto-compensating laser induced-incandescence for all cases. Flow field data obtained using stereoscopic particle image velocimetry is utilized to ascertain the hydrodynamic effects on soot distribution due to addition of lighter species. Soot formation was found to be enhanced by the addition of hydrogen when allowance was made for the dilution effect using the helium doped flame experiments. Possible causes of this observation including the molecular diffusivities of hydrogen and helium, and chemical interaction are discussed.     

Modeling of chemical tracer transport in the atmospheric environment and its impact on the global climate

Continental regions are experiencing rapid environmental changes due to expansion of industrial activities and land uses in different types of agricultural productions, burning of fossil fuels, etc., which lead to the emanation of huge amount of smog aerosol particulates and chemicals in the atmosphere. Information about these chemical tracers has been found from Indian Ocean Experiment (INDOEX), Intergovernmental Panel for Climate Change (IPCC) assessment reports as well as from other sources. The results of these computations may be interpreted by the chemical tracer transport model. In this paper, we have used a global atmospheric model in which the optical properties and the concentrations of the chemical tracers and aerosols have been incorporated. The aerosols and chemicals are transported in the atmospheric environment by the model cumulus convection and through the model semi-Lagrangian advection process . Thus, they are globally distributed along with the wind flow. The model has been used in studying the impact of the tropospheric chemical perturbations on the global environment.     

Sensitized solar cells based on natural dyes

We have employed several natural dyes for application in dye sensitized solar cells (DSSC). Spinach, beet, red cabbage and strawberry are well known and have been already used. We then checked the opportunity to realize good DSSC with dyes available in Tunisia: Henna and Mallow (Mloukhya). Henna is a herb which has interesting reddish brownish dyeing properties used since antiquity for traditional decoration of skin, hair and fingernails in the Middle East and North Africa. The mallow is a green vegetable which is widely consumed in the same region. The optical absorption of the extracted dyes diluted in ethanol or distilled water were measured using UV–Vis spectrophotometer. The absorption in beet and red cabbage is more significant compared to the other dyes. Mallow and henna dyes present a noticeable band in the region 660 nm. Infra-red spectroscopy measurements were done to probe the structure and dynamics in our used dyes. In this paper, we present the steps followed in the making of our solar cells. The DSSC were assembled using two glass plates (supporting electrode and counter electrode) which are coated with transparent conducting oxide (TCO). The counter electrode is coated by a catalyst Pt (Platinum) to speed up the redox reaction with the electrolyte solution. The typical J–V curves of our solar cells under AM 1.5 using a density of power 100 mW/cm² were measured. Cells using henna and mallow as dyes present less degradation with time in the photoelectric characteristics. The mallow cell shows a good fill factor of 55% and a noticeable photoelectric conversion efficiency of 0.215%.     

Fiber-based tunable dispersion compensation

Tunable dispersion has been implemented in various technology platforms, including fiber gratings, planar waveguides, thin film etalons, and bulk optic technologies. This paper will focus on fiber grating based tunable dispersion compensation, because fiber gratings are at present one of the best developed TDC technologies available. The paper is divided into three parts. In the first part we describe grating based TDC technologies and discuss their advantages and disadvantages. We focus on thermally tuned linearly chirped fiber gratings, as these have to date been the most successful grating technology for 40 Gbit/s. We also compare grating TDCs to two other prominent tunable dispersion technologies: thin film etalons and planar waveguide ring resonators. In the second section we describe the techniques used to fabricate high performance dispersion compensation gratings as well as the theory of the primary defect of fiber grating dispersion compensation: group delay ripple (GDR). In the third section we describe the telecom system related issues for tunable gratings, including characterization of grating performance, tunability requirements and results from actual system trials using tunable FBGs.     

Autoignition characteristics of bio-based fuels,farnesane and TPGME,in comparison with fuels of similar cetane rating

Bio-based alternative fuels have received increasing attention with growing concerns about depletion of fossil reserves and environmental deterioration. The development of new combustion concepts in internal combustion engines requires a better understanding of autoignition characteristics of the bio-based alternative fuels. This study investigates two cases of alternative fuels, namely, a kerosene-type fuel farnesane and an oxygenated fuel, TPGME, and compares those fuels with full-boiling range of fuels with similar cetane number. The homogeneous autoignition and spray ignition characteristics of the selected fuels are studied using a modified CFR octane rating engine and a cetane rating instrument, respectively. When comparing farnesane with a full-boiling range counterpart (HRJ8), their similar cetane ratings result in comparable combustion heat release, but the overall ignition reactivity of farnesane is stronger than HRJ8 during the pre-ignition process. Results from a constant volume spray combustion chamber indicate that the spray process of farnesane and HRJ8 strongly influences the overall ignition delay of each fuel. Despite the similar cetane ratings of TPGME and n-heptane, TPGME shows greater apparent low-temperature oxidation reactivity at low compression ratios in the range from CR 4.0-5.5 than n-heptane. A simplified model focused on the key reaction pathways of low-temperature oxidation of TPGME has been applied to account for the stronger low-temperature reactivity of TPGME, supported by density functional theory (DFT) calculations. Regardless of the similar cetane ratings of the fuels, n-heptane and JP-8/SPK lead to similar total ignition delay times, while TPGME shows the shortest overall ignition delay times in the constant volume combustion chamber.     

Simulations and analysis of a piezoelectric micropump

A number of micropumps have been proposed in the last few years based on different actuating principles and fabricated by different technologies. However, many of those micropumps have been designed taking into account primarily available microfabrication technologies rather than appropriate pump performance analysis. In fact, not all papers are available in the literature presenting theoretical models usable to describe the functioning and predict the performance of those micropumps. In this paper, we present a new micropump model and FEA method suitable for guiding the design and predicting the performance of a micropump actuated by a piezoelectric actuator. The model takes into account the influence of piezoelectric transducer and pump geometry. Simulations have been performed and compared with results of experiments on a prototype micropump fabricated in our laboratory.     

A review on recent advances in hydrogen energy,fuel cell,biofuel and fuel refining via ultrasound process intensification

Hydrogen energy is one of the most suitable green substitutes for harmful fossil fuels and has been investigated widely. This review extensively compiles and compares various methodologies used in the production, storage and usage of hydrogen. Sonochemistry is an emerging synthesis process and intensification technique adapted for the synthesis of novel materials. It manifests acoustic cavitation phenomena caused by ultrasound where higher rates of reactions occur locally. The review discusses the effectiveness of sonochemical routes in developing fuel cell catalysts, fuel refining, biofuel production, chemical processes for hydrogen production and the physical, chemical and electrochemical hydrogen storage techniques. The operational parameters and environmental conditions used during ultrasonication also influence the production rates, which have been elucidated in detail. Hence, this review's major focus addresses sonochemical methods that can contribute to the technical challenges involved in hydrogen usage for energy.     

Jet-stirred reactor and flame studies of propanal oxidation

There is a strong drive towards utilizing oxygenated biofuels in blends with existing fossil fuels. Improving the kinetic modeling of the oxidation of these bio-derived oxygenates requires further investigation of their key stable intermediates such as the aldehydes. In this study, an experimental and chemical kinetic modeling investigation of propanal oxidation was carried out. Experiments were conducted in a jet stirred reactor and in counterflow flames over a wide range of equivalence ratios, temperatures, and ambient pressures. Stable species concentration profiles were measured in the jet stirred reactor and laminar flame speeds were measured. A detailed chemical kinetic reaction model was validated using the present experimental results and existing literature data. The model was used also to provide insight into the controlling reaction pathways for propanal oxidation in both the low- and high-temperature kinetic regimes.