Recent advances in fuel cell technology and its applications

Currently, there is a good deal of interest in the possibility that fuel cells will make an important contribution to world energy supplies for both mobile and stationary applications. This paper provides an up-to-date review of fuel cell technology.     

Self-adjusting smart windows based on polymer-dispersed liquid crystals

The control of sunlight can be achieved either by electrochromic or polymer-dispersed liquid crystal (PDLC) smart windows. We have recently shown that it is possible to homeotropically align fluid mixtures of low molecular mass liquid crystal with a negative dielectric anisotropy, and a liquid crystalline monomer, in order to obtain electrically switchable chromogenic devices. They are new materials useful for external glazing. In fact, they are not affected by the classical drawbacks of PDLCs. In this paper we present a new self-switchable glazing technology based on the light-controlled transmittance in a PDLC device. The self-adjusting chromogenic material, which we obtain, is able to self-increase its scattering as a function of the impinging light intensity. The relationship between the electro-optical response and the physical-chemical properties of the components has been also investigated.     

The temperature behavior of smart windows under direct solar radiation

The purpose of this paper was to investigate the variation in temperature of electrochromic devices under direct solar radiation and to compare the results with double-glazed glass. The devices consisted of a V₂O₅ layer as an ion storage film and a WO₃ layer as an electrochromic layer. The V₂O₅ and WO₃ films were prepared by thermal and electron beam evaporation, respectively. The optical properties and structures of these films were investigated. Both the ion storage film and the electrochromic layer were amorphous. The optical absorption was caused by a direct-forbidden transition in V₂O₅ and by an indirect-allowed transition in WO₃. The maximum temperatures under solar radiation were measured for colored and bleached devices, double glass and air, they were found to be approximately 63, 63, 53 and 36 °C, respectively. The rates of increasing temperature to the incident power density for colored, bleached devices and double glass were 0.051, 0.049 and 0.041 °C/(W/m²), respectively.     

Recent advances in coherent anti-Stokes Raman scattering spectroscopy: Fundamental developments and applications in reacting flows

Coherent anti-Stokes Raman scattering (CARS) spectroscopy is widely used for measuring temperature and species concentration in reacting flows. This paper reviews the advances made over the last twelve years in the development and application of CARS spectroscopy in gas-phase reacting flows. The advent of high-power nanosecond (ns) lasers and off-the-shelf compact picosecond (ps) and femtosecond (fs) lasers is enabling the rapid expansion of the application of single-shot or high-bandwidth CARS spectroscopy in a way that would have been quite unimaginable two decades ago. Furthermore, compact ps lasers are paving the way for the development of a fiber-based CARS system for use in harsh environments. The objective of this paper is to provide an overview of recent progresses in ns-, ps-, and fs-CARS spectroscopy for gas-phase thermometry and species-concentration measurements since the second edition of A.C. Eckbreth's book entitled Laser Diagnostics for Combustion Temperature and Species, which was published in 1996. During the last two decades, four encompassing issues have driven the fundamental development and application of CARS spectroscopy in reacting flows: 1) measurement of temperature and concentration of multiple species with one CARS system, 2) extension of the application of traditional ns-CARS to challenging reacting flow environments, 3) performance of nonresonant background-free and collision-free measurements in high-pressure reacting flows, and 4) measurement of temperature and species concentration at high bandwidth, typically 1 kHz or greater, to address the instability and transient phenomena associated with turbulent reacting flows in the combustors and augmentors of modern propulsion systems. This review is focused on identifying and discussing the recent results of gas-phase CARS spectroscopy related to the four issues mentioned above. The feasibility of performing high-bandwidth CARS spectroscopy with one laser beam as well as the potential of tailored fs lasers for thermometry and species-concentration measurements in gas-phase reacting flows are also discussed.     

Recent advances in alternative material photovoltaics

Abstract

Alternative material photovoltaics (PVs) have started gaining more attention recently. Although the field is not new, it just started growing a few years ago. The PV market has been dominated by various silicon technologies, besides a few other popular thin films, such as CdTe, copper–indium–galium–selenide varieties and some III–V materials. This has been reflected in research as well. Successful developments of efficient solar cells using alternative absorbers will significantly enrich the PV industry and reduce the market gap with other energy sources. Hence, in this review, recent advances and trends to develop PVs using alternative materials are presented and discussed. The focus will be mainly on binary as well as environmentally friendly compounds and thin film devices. Nonetheless, some other more complex materials and structures will be briefly addressed.     

Recent advances in NiMH battery technology

Nickel-metal hydride (NiMH) is a commercially important rechargeable battery technology for both consumer and industrial applications due to design flexibility, excellent energy and power, environmental acceptability and cost. [1] From the initial product introduction in 1991 of cylindrical cells having an energy of 54 Wh kg⁻¹, today's small consumer cells have a specific energy over 100 Wh kg⁻¹. Numerous licensed manufacturers produce a myriad of NiMH products ranging from 30 mAh button cells to a wide variety of consumer cylindrical products, prismatic cells up to 250 Ah for electric buses and 6 Ah multicell modules for hybrid electric vehicles. Power has increased from under 200 to 1200 W kg⁻¹ commercially and up to 2000 W kg⁻¹ at a development level [2].     

Recent advances in residual stress measurement

Until recently residual stresses have been included in structural integrity assessments of nuclear pressure vessels and piping in a very primitive manner due to the lack of reliable residual stress measurement or prediction tools. This situation is changing the capabilities of newly emerging destructive (i.e. the contour method) and non-destructive (i.e. magnetic and high-energy synchrotron X-ray strain mapping) residual stress measurement techniques for evaluating ferritic and austenitic pressure vessel components are contrasted against more well-established methods. These new approaches offer the potential for obtaining area maps of residual stress or strain in welded plants, mock-up components or generic test-pieces. The mapped field may be used directly in structural integrity calculations, or indirectly to validate finite element process/structural models on which safety cases for pressurised nuclear systems are founded. These measurement methods are complementary in terms of application to actual plant, cost effectiveness and measurements in thick sections. In each case an exemplar case study is used to illustrate the method and to highlight its particular capabilities.     

Recent advance in life prediction for HTGR applications

Key issues in design methods at high temperatures for an HTGR regime are creep constitutive equations. The life in service of structural components is controlled by creep damage. A creep constitutive equation is then needed to calculate inelastic stress-strain components. The method for life prediction, applicable to this temperature regime, has been investigated. The ductility exhaustion rule in conjunction with the creep constitutive equation is confirmed to be useful from the point of view of methodology. Creep-fatigue damage for Hastelloy XRs was assessed by this method in conjunction with the Miner's rule. It is found that the ductility exhaustion for creep damage has a tendency to estimate creep damage larger than the time faction that is often used conventionally. Creep damage under compressive stress should be evaluated at high temperatures.     

过渡金属基催化剂用于氧析出反应的研究进展

由于动力学缓慢,在能源转换和储存过程中,特别是在电解水过程,氧析出反应(OER)是一个关键的限制性反应.目前该领域所面临的主要挑战是探索不含贵金属的催化剂,以促进OER反应过程.由于独特的化学、物理特性和低廉的使用成本,过渡金属基化合物在水的电化学分解过程中的应用得到了广泛关注.本文综述了尖晶石、钙钛矿和层状双金属氢氧化物(LDH)三种过渡金属化合物作为OER电催化剂的最新研究现状和进展,重点介绍了提高OER催化活性和催化剂稳定性的策略以及相应催化剂的催化性能和效果.综合当前文献的研究结果可以发现,OER催化活性的提高主要有两种措施:一是在催化剂中引入更多的催化活性位点,并且保证这些活性位点尽可能暴露在催化剂的表面;二是优化催化剂的导电性能.通过控制尺寸、形态、晶格缺陷、氧空位、相态及化学组成,或者与导电材料相复合,可以在一定程度上满足上述两种要求.最后,对OER电催化剂的未来发展方向进行简要讨论.     

Recent advances in cobalt disulfide for electrochemical hydrogen evolution reaction

Hydrogen production by water electrolysis is the most promising green hydrogen supply method in the future. Electrocatalytic hydrogen evolution reaction (HER), an essential step in water electrolysis, has received continuous interest for a long time. Noble metal-based electrocatalysts exhibit excellent performance for HER, while their high price, limited reserves, and insufficient durability limit their large-scale applications. Transition metal sulfides (TMSs) have been extensively studied as potential alternative catalysts, among which cobalt disulfide (CoS₂) stands out due to its unique structure, low price, and good electrical conductivity. Although remarkable progress has been made, the catalytic activity and stability of CoS₂ electrode materials themselves are still insufficient for large-scale industrial applications, so effective improvement of the HER catalytic performance of CoS₂ remains the focus of research. In this review, we briefly outline the reaction mechanism of HER, focusing on strategies to improve the catalytic performance of CoS₂, including morphology engineering, carbon materials combination, heteroatom doping, and heterostructure construction. Furthermore, the key challenges and opportunities for CoS₂ electrode materials as an electrocatalytic material for HER are discussed.     

Recent advances in droplet vaporization and combustion

Recent progress on understanding the fundamental mechanisms governing droplet vaporization and combustion are reviewed. Topics include the classical d²-Law and its limitations; the major transient processes of droplet heating and fuel vapor accumulation; effects due to variable transport property assumptions; combustion of multicomponent fuels including the miscible fuel blends, immiscible emulsions, and coal-oil mixtures, finite-rate kinetics leading to ignition and extinction; and droplet interaction. Potentially promising research topics are also suggested.     

Recent Advances in Precombustion Coal Cleaning Processes

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Durability issues and service lifetime prediction of electrochromic windows for buildings applications

In general, the purposes of this paper are to elucidate the crucial importance of durability and service lifetime prediction (SLP) for electrochromic windows (ECWs) and to present an outline for developing a SLP methodology for ECWs. The specific objectives are (a) to illustrate the generic nature of SLP for several types of solar energy conversion or energy conservation devices, (b) to summarize the major durability issues associated with ECWs, (c) to justify using SLP in the triad of cost, performance, and durability rather than just durability, (d) to define and explain the seven major elements that constitute a generic SLP methodology, (e) to provide background for implementing the SLP methodology for ECWs, including the complexity of the potential degradation mechanisms, and (f) to provide an outline of studies using ECWs for improving the durability of ECW materials and predicting a service lifetime for ECWs using the SLP methodology outlined in objective (d). Our major conclusions are that substantial R&Dis necessary to understand the factors that limit ECW durability, and that it is possible to predict the service lifetime of ECWs.     

Plate heat exchangers: Recent advances

This study presents the advances in plate heat exchangers both in theory and application. It dresses the direction of various technical research and developments in the field of energy handling and conservation. The selected areas of heat transfer performance and pressure drop characteristics, general models and calculations change of phase; boiling and condensation, fouling and corrosion, and welded type plate heat exchangers and finally other related areas are highlighted.     

Integration of smart windows into building design for reduction of yearly overall energy consumption and peak loads

The purpose of this work is to investigate the potential of diminishing the energy consumed by typical low thermal mass office buildings for heating, cooling and lighting by using smart windows. The windows considered consisted of a double pane glazing unit in which a controllable absorbing layer is added on the interior surface of the exterior glass pane. This absorbing layer allows to change the optical properties of the window, resulting in a direct potential of control of the incident solar heat flux entering the building through the windows. A corresponding numerical model is developed showing that optimizing the solar heat flux absorption rate of the absorbing layer in regard of the necessary heating, cooling and lighting needs helps reducing significantly the total yearly energy consumption, and cooling peak loads. The simulations were done considering a building located in Quebec City, Canada.     

Recent anode advances in solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are electrochemical reactors that can directly convert the chemical energy of a fuel gas into electrical energy with high efficiency and in an environment-friendly way. The recent trends in the research of solid oxide fuel cells concern the use of available hydrocarbon fuels, such as natural gas. The most commonly used anode material Ni/YSZ cermet exhibits some disadvantages when hydrocarbons were used as fuels. Thus it is necessary to develop alternative anode materials which display mixed conductivity under fuel conditions. This article reviews the recent developments of anode in SOFCs with principal emphasis on the material aspects. In addition, the mechanism and kinetics of fuel oxidation reactions are also addressed. Various processes used for the cost-effective fabrication of anode have also been summarized. Finally, this review will be concluded with personal perspectives on the future research directions of this area.     

Recent advances in the development of supported carbon membranes for gas separation

Carbon membranes have emerged in the 70's and have been presenting promising results for application in processes involving gas separation because of their sieving effects. The carbon membranes are obtained by pyrolysis of a precursor polymer beyond its initial decomposition temperature under essentially inert conditions. Supported and unsupported carbon membranes can be produced, but the former are distinguished for the industrial separation of gases due to the improved mechanical strength and high chemical and thermal stability. In this context, different types of support, coating methods and pyrolysis conditions for supported carbon membranes have been reported in the literature, in order to improve the separation capability of gas mixtures in respect to permeability and selectivity. The aim of this review article is to report and discuss the evolution of supported carbon membrane in the last 10 years in respect to configuration, transport mechanisms, manufacturing processes and its main applications, highlighting the main challenges still to be overcome for this technology to be applied industrially.     

Isothermal transient ionic current study of laminated electrochromic devices for smart window applications

The isothermal transient ionic current (ITIC) in three different kinds of laminated electrochromic devices has been determined. The devices consisted of one 300 nm thick layer of nickel oxide and one 300 nm thick layer of WO₃ deposited onto separate In₂O₃:Sn (ITO) covered glass substrates by DC magnetron sputtering at room temperature. They were then laminated with a polymeric ion conductor, acting as electrolyte, in symmetric and asymmetric configurations, i.e. WO₃/WO₃, NiO_xV_yH_z/NiO_xV_yH_z and WO₃/NiO_xH_y. The electrolyte was prepared by mixing polyethylene glycol of average molecular weight 400 (PEG 400) and lithium triflouromethanesulfonate (LiSO₃CF₃) for 12 h at 70°C and with a ratio oxygen/lithium (O/Li)=10. The samples were first polarized, i.e. the ions are transported to one of the electrodes, which in the asymmetric devices is the nickel oxide electrode. At the first applied potential step, the ions move through the electrolyte towards the opposite electrode. The potential is then switched and the ions move back to the first electrode. The ITIC curves are found to depend on the electrode material and in the asymmetric case also the direction of the ion current.