Microelectromechanical deformable mirrors

A new class of silicon-based deformable mirrors is described. These devices are capable of correcting time-varying aberrations in imaging or beam forming applications. Each mirror is composed of a flexible silicon membrane supported by an underlying array of electrostatic parallel plate actuators. All structural and electronic elements were fabricated through conventional surface micromachining using polycrystalline silicon thin films. A layout and fabrication design strategy for reducing nonplanar topography in multilayer micromachining was developed and used to achieve nearly flat membrane surfaces. Several deformable mirrors were characterized for their electromechanical performance. Real-time correction of optical aberrations was demonstrated using a single mirror segment connected to a closed-loop feedback control system. Undesirable mirror contours caused by residual stress gradients in the membrane were observed     

试评小功率氢-空气燃料电池

根据储氢系统可能达到的比能量和燃料电池堆在常温常压下的比功率讨论了小功率氢 空气燃料电池系统的比能量 ,在连续工作时间不长时难以与常规二次电池竞争。在常温下如何排除电池反应生成的水也存在一些问题。据此讨论了小功率氢 空气燃料电池的可能适用范围及进一步发展时应解决的问题     

微型直接甲醇燃料电池的技术进展与挑战

随着便携式电子产品的普及化,人们对小体积及高性能的便携式电源的需求与日俱增。利用微机械加工技术制作的微型直接甲醇燃料电池具有体积小、质量轻、能量密度高、携带安全等特点,适用于民用数码产品(如笔记本电脑、手机等)和国防系统(如单兵系统、弹药引信等)等领域。但与常规直接甲醇燃料电池相比,微型直接甲醇燃料电池在产物管理、制造方法、膜电极制备、燃料供给等方面有所不同,工作效能存在较大差异。从以上几方面对目前微型直接甲醇燃料电池的研究状况进行深入调研,分析了影响燃料电池输出性能的关键因素,并指出了微型直接甲醇燃料电池面向未来应用所需要解决的技术挑战和发展趋势。     

氢燃料电池在电力系统后备电源的应用研究

笔者针对变电站直流系统,应用新型氢燃料后备电源替代蓄电池组作为后备电源产品。旨在将氢燃料电源作为直流系统整体后备电源,氢燃料应急移动直流电源,直流技改中氢燃料后备电源的可行性和解决方案进行测试研究,提出新型后备电源设计、采取措施以及提出一整套系统的解决方案。结果显示,将氢燃料电池供电系统代替铅酸蓄电池组作为停电期间的后备电源,只保留少量的铅酸蓄电池作为系统启动过程中的支撑,停电时自动启动、市电恢复时自动进入待机状态,铅酸电池随即进入浮充状态。大量减少铅酸蓄电池的使用,能减少对环境的污染。氢燃料电池供电系统若包含DC/AC逆变设备,即可为通信站的交流负载供电,替代汽柴油机,降低噪音和振动,减少二氧化碳等气体排放。     

SFC,Toshiba show DMFC prototypes at CeBIT

Munich-based SFC Smart Fuel Cell presented its latest direct methanol fuel cell performance prototype at the recent CeBIT 2004 information technology trade show in Hannover, Germany. SFC says the ‘PowerBoy’ is a flexible and highly miniaturized power supply that can operate and charge a variety of consumer electronic devices, including parallel operation of several products.     

多孔硅在微型燃料电池中的应用研究进展

多孔硅作为一种具有特殊功能的结构材料,在燃料电池特别是微型燃料电池中,可用作扩散层、质子交换层和重整器等构件。介绍了应用于微型燃料电池的多孔硅的结构特点及其制备方法,综述了多孔硅在微型燃料电池领域中的应用研究进展。     

考虑部件使用寿命的FCEV能量管理策略

能量管理控制策略是提升燃料电池电动汽车经济性及部件耐久性的关键技术,为了解决已有能量管理控制策略存在的缺陷,本文提出了一种基于二次型效用函数的能量管理策略。首先建立了车辆和零部件的数学模型,并通过零部件试验验证模型的准确性。其次应用二次型效用函数将需求功率分解为燃料电池和电池的输出功率,该策略考虑了电池及燃料电池的历史输出状态、变载率等,此外为了提高能源的耐久性和车辆的经济性,应用纳什均衡计算出所提出策略的最佳参数。仿真结果表明,所提出的控制策略可以有效提高燃料电池和电池的耐久性,降低氢气消耗,提升续驶里程。与基于有限状态机的策略相比,该策略可降低21.15%电池性能的衰退。与模糊控制策略相比,所提出的控制策略可减少36.52%燃料电池性能的衰退。     

MH/Ni动力电池的分选及性能

研究了燃料电池城市客车用MH/Ni动力电池的分选组合方法及充放电性能.分别采用LBC-80方形动力电池检测分析系统和电动车用动力电池仿真测试系统对100Ah MH/Ni动力电池进行分选,选出320只单体电池,并进行了12V模块的组合.结果表明:分选组合而成的12 V模块在比能量高于55 Wh/kg的前提下,具有3C(300A)持续放电大于3min的能力.根据384 V/100Ah电池组不同DOD条件下脉冲功率容量测试计算得知,该电池组可以充分满足燃料电池城市客车使用要求.     

日本燃料电池的发展状况

简要地概述了日本燃料电池的发展状况。因燃料电池两电极中均含有贵重金属 (铂 钌 )作催化剂 ,大部分情况需要防止其对一氧化碳的中毒失效。如果含有碱性电解质 ,要考虑除去二氧化碳。碱性燃料电池开发较早 ;高分子电解质燃料电池在家庭及动力电源的应用上取得很大进展 ;磷酸型燃料电池已广泛应用于供电、供热 ;熔融碳酸型燃料电池则非常适合于大规模及高效率的电站应用 ;固体氧化物燃料电池的重点集中于平面基材的研究 ,以降低成本 ,适合大规模生产。在各种燃料电池的研究开发上 ,不单只是利用燃料来发电 ;更重要的是使能源得到合理的充分利用。通过对上述五种燃料电池的性能比较 ,分析了它们今后的发展方向     

镁燃料电池的发展及应用

综述了镁-空气燃料电池与镁-过氧化氢燃料电池系统的工作原理,概括了近年来在镁阳极、阴极电催化剂与结构、电解质添加剂等方面的研究与进展。镁燃料电池具有高比能量、长期存放、安全和成本低等特点,在军事和民用方面有广泛的用途,可广泛应用于可移动电子设备电源、自主式潜航器电源、海洋水下仪器电源和备用电源等领域。     

燃料电池在电动汽车中的应用前景

以石油燃料为动力的汽车,其尾气是空气污染的主要来源,以充电电池为动力的电动汽车是解决汽车尾气污染的途径之一.目前,由于充电电池贮能量比内燃机低而使电动汽车数量仍然很少.燃料电池是未来最有希望替代内燃机的汽车动力,它的运行效率高,能够使用甲醇、乙醇、天然气或氢气等非石油基燃料,还可以显著改善排气质量,减少大气污染.可用于电动汽车的燃料电池类型有磷酸型燃料电池、离子交换膜燃料电池和固体氧化物燃料电池.本文对上述燃料电池的原理和性能作了详细介绍,对世界各国的研究开发活动作了介绍.     

小型燃料电池商品化展望

介绍了质子交换膜燃料电池（PEMFC）和直接醇类燃料电池（DAFC）实现商品化的优势和存在的技术问题;指出价格是它们商业化的关键问题,由于DAFC能制成小功率的电池,受价格的影响相对较小,很可能会优先商业化。     

Comparative evaluation of different power management strategies of a stand-alone PV/Wind/PEMFC hybrid power system

This study presents different power management strategies of a stand-alone hybrid power system. The system consists of three power generation systems, photovoltaic (PV) panels, a wind turbine and a proton exchange membrane fuel cell (PEMFC). PV and wind turbine is the main supply for the system, and the fuel cell performs as a backup power source. Therefore, continuous energy supply needs energy storing devices. In this proposed hybrid system, gel batteries are used. The state of charge (SOC), charge-discharge currents are affecting the battery energy efficiency. In this study, the battery energy efficiency is evaluated with three different power management strategies. The control algorithm is using Matlab-Simulink®.     

基于模糊的氢燃料电池时序采样能量控制方法

氢燃料电池汽车的能量管理系统对燃料电池寿命、耐久、经济性等性能起着重要作用。 在对经典模糊控制策略的改进 基础上,解决控制策略存在的燃料电池输出功率变载频繁的问题,以时序规则进行优化设计,根据燃料电池运行特性、工作效率 点以及道路工况具备的特点提出了一种基于时序周期采样的控制策略,通过对车辆搭载燃料电池和动力电池输出功率的控制, 完成能量管理策略优化。 针对一款实际运营的燃料电池公交车在等速工况和中国典型城市公交循环工况下,使用不同控制策 略时的氢耗、燃料电池输出功率状态、动力电池荷电状态变化等数据进行分析,发现设计的控制策略能有效降低燃料电池变载 次数,提高燃料电池使用寿命,在氢耗方面比功率跟随策略、开关控制策略有明显优势,在初始动力电池荷电状态为 60%条件 下,后两者策略氢耗分别增加了 3. 98%和 27. 88%。     

低温型燃料电池混合发电系统的半物理仿真

针对低温型燃料电池运行状态对电池性能和寿命的影响,建立了基于机理的质子交换膜燃料电池的电气模型,给出了采用电化学方程的质子交换膜燃料电池半物理混合发电系统电气特性的模型结构、优化、仿真和实验,为低温型燃料电池混合发电系统的研究提供了一个实际工程应用模型。     

Hybrid fuel-cell strategies for clean power generation

A hybrid power system consists of a combination of two or more power generation technologies to make best use of their operating characteristics and to obtain efficiencies higher than that could be obtained from a single power source. Since fuel cells directly convert fuel and an oxidant into electricity through an electrochemical process, they produce very low emissions and have higher operating efficiencies. Hence, combining fuel cells with other sources, the efficiency of the combined system can be further increased or extend the duration of the available power to the load as a backup power. In this paper, different types of fuel-cell hybrid systems and their applications are presented. An analysis of the combined cycle operation of a solid oxide fuel cell (SOFC)-microturbine is presented. A strategy for combining the thermophotovoltaic power generation unit and SOFC to obtain the hybrid power system that would have higher efficiency is proposed. The hybrid operation of wind power and solar power system with proton exchange membrane fuel cell is also presented.     

An Electrochemical Generator Containing Cylindrical Aluminum-Air Cells

The article considers matters concerned with optimizing the design and technology of aluminum-air electrochemical generators for emergency and backup power supply to different consumers. The physicochemical principles used to construct such generators are briefly described. Owing to the absence of self-discharge in the energy storage mode, aluminum-air generators can remain in the waiting mode for a longer period of time as compared with electrochemical storage batteries or hydrogen-air fuel cells. The source is activated by adding water to it. To obtain better specific parameters of aluminum-air cells and improve their manufacturability, a cylindrical cell design is proposed. One-off cells and a battery have been developed, fabricated, and tested. The obtained results are compared with the data from testing a battery and cells having a flat design. The possibility of obtaining essentially better specific characteristics due to making a shift to a cylindrical design is shown. Owing to the proposed design, more efficient use of aluminum has been achieved along with simplifying the system for maintaining the thermal balance of the cell and battery. The article presents the results from testing a single aluminum-air cell and a four-cell battery, which showed the need to adjust the concentration of electrolyte in cells and batteries of this type. The obtained data are compared with the results from tests of previously fabricated aluminum-air elements of the classical flat design. For determining the prospects for using generators of this type, their technical and economic characteristics were compared with those of the main competing sources of emergency and backup power supply, including lead-acid and lithium-ion storage batteries, and with hydrogen-air electrochemical generators. The characteristic time of power source operation and the frequency of its coming into action for which the use of aluminum-air electrochemical generators is economically justified are determined, and recommendations on extending the range of these parameters are given.     

质子交换膜燃料电池电极结构的扫描电镜分析

质子交换膜燃料电池采用固体聚合物膜为电解质,简化了电池的水和电解质管理;薄的电解质膜使其可以获得非常高的比能量;高度可靠性和环境友好使其在用于航天、陆地和水下设备电源等方面具有广泛的应用前景。良好的电极结构是获得高的电池性能的先决条件。本文采用扫描电镜,对质子交换膜燃料电池的铂电催化剂、电极表面和电极切面等进行了分析。结果表明：只有良好地分散,催化剂才有较大的表面积;电极的催化层经热压后,厚度减薄一半;在电极内过多地浸入Ｎａｆｉｏｎ将增大电解质电阻,采用喷涂法向电极内浸入Ｎａｆｉｏｎ易在电极表面形成一层电解质薄膜,造成电极内Ｎａｆｉｏｎ不足,表面过剩,减少电极反应界面和增大质子传递阻力。     

Cantilevers and tips for atomic force microscopy

The key component of the atomic force microscope (AFM) is a cantilever with a tip. The tip must be sharp enough to record with high lateral resolution the topography. The cantilever must also have the appropriate compliance and resonant frequency for the type of operation selected, which can be either a contact or a noncontact mode of operation. The requirement for a low spring constant (less than 1 N/m) and a high resonant frequency (greater than 10 kHz) led to silicon micromachining techniques early on in the development of the AFM. Silicon micromachining is a technology by which a silicon wafer is processed through a series of deposition, photolithography, and etching steps to produce a mechanical structure with dimensional tolerances in the order of 1 μm. The use of silicon micromachining techniques has benefited the AFM in several aspects: (1) sharper tips can be manufactured with micromachining techniques than with alternative electrochemical etching techniques, as used for scanning tunneling microscopy tips; (2) batch fabrication simultaneously of thousands of cantilevers guarantees a high degree of reproducibility in the mechanical properties of the cantilevers; and (3) micromachined cantilevers are inexpensive     

MTI Micro announces supply chain for first product

US-based MTI MicroFuel Cells, a leading developer of miniaturized fuel cells for handheld electronic devices, has completed formation of the supply-chain partner team for its first product launch, planned for the end of 2004.