上海某高密度功率机房的气流组织研究

上海某项目高密度功率机房由原科研楼改造而成,机房单机柜平均功率为8 kW,弹性功率为15 kW。机房末端空调为水冷型机房专用精密空调,配置原则为N+X(N<5,X=1;5≤N<10,X=2)。冷水的供/回水温度为18℃/24℃,机房采用无架空地板弥漫式送风、封闭热通道、吊顶回风的气流组织形式。控制空调的送风温度为24℃,根据回风温度控制EC风机的转速。当机房空调故障(相邻2个和不相邻2个)时,机房热环境仍可满足连续布置8 kW单机柜、间隔布置(空1个机柜位)15 kW单机柜、间隔布置(空2个机柜位)2个15 kW单机柜的要求。

高密度电法在涌水区探测中的应用研究

地铁建设中,隧道掘进时容易发生涌水、涌沙等突发事件。在突发状况下,现场情况比较复杂,各种电磁干扰及人为干扰较大。如何克服多干扰,利用先进的物探技术,第一时间为事故处理提供详实可靠的成果是关键问题。综合分析后选择大功率高密度电法进行探测,及时准确的圈定了漏水影响区域范围及空间位置并指导注浆;通过注浆前后成果的对比,及时检验了注浆加固的效果,注浆止水效果良好。在快速应对处置涌水中起到了重要的作用。

热设计在车载固态发射机中的应用

以某车载固态发射机为例进行了热设计,通过计算和仿真分析得到了固态发射机内主要模块表面温度分布,证明合理的热设计能够为高密度高功率的固态发射机结构总体方案设计和优化提供理论支撑,并节省研制成本,提高工作效率。

High Brightness,High Power Density Fiber Coupling of High Power Laser Diode

The output radiation from the 100μm×1μm aperture of a high power Laser Diode (LD) is efficiently coupled into a 50μm multimode optical fiber.The fiber output of the high power LD with high brightness and high power density is achieved.The power density is up to 3 6×104W/cm2 and the coupling efficiency is 70%.The extreme divergence and the astigmatism of high power LDs require the optics with complex lens structures and high performance.A double-curved lens with two crossed cylindrical lenses structured on both sides of the glass substrate is used in the coupling system.

Efficiency Improvement of PEM Fuel Cells via Humidity Control

PEM （Proton Exchange Membrane） fuel cell is a promising renewable energy source to a wide range of applications for its clean products and high power density. However, controlling its humidity is a challenging problem due to the interdependence of several phenomena contributing in membrane＇s water content. This work deals with efficiency improvement of PEM fuel cells via humidity control. An innovative strategy of control based on the model of Ref. [1] is proposed. It consists on regulating gas humidification rates according to the power demand so that to minimize power losses. The proposed control takes into consideration constraints related to humidification in order to avoid dry out or flooding of the membrane. Simulations results show that time-phasing between hydrogen and oxygen humidification rates plays an important role in minimizing power losses. The proposed control shows significant improvement in the fuel cell＇s efficiency up to 20%.

Thermal analysis of surface-mounted permanent magnet synchronous motor for electric vehicle application

As a driving motor, surface mounted permanent magnet synchronous motor exhibits high efficiency and high power density. However, it is susceptible to suffer irreversible demagnetization and insulation failure of coils under severe thermal load condition. Therefore, it is essential to predict temperattrre distribution in the driving motor. In this paper, a lumped parameter thermal mode/of surface mounted permanent magnet is investigated. By using finite element method, the iron loss distribution in various parts of the driving motor is achieved. Moreover, the influences of interface gap and flow rate on temperature distribution are discussed. Finally, the simulation of temperature distribution in different parts of the driving motor is achieved. The presented methodology contributes to verify the feasibility of the driving motor design.

Energy Storage System with Ultracapacitors for Thermal Underwater Glider

A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider.Heat generated by PEMFC is used as the propulsion power of the glider,and the electricity is used in the control and sensor system.An electric energy storage system (ESS) is required which possesses high power density with good cycle life.Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices.Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system.Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS.

Integration of Power MOSFETs for Synchronous Buck Converters

Efficiency and power loss in the microelectronic devices is a major issue in power electronics applications. The engineers are challenged every year to increase power density and at the same time reduce the amount of power dissipated in the applications to keep the maximum temperatures under specifications. This situation drives a constant demand for better efficiencies in smaller packages. Traditional approaches to improve efficiency in DC/DC synchronous buck converters include reducing conduction losses in the MOSFETs （metal oxide semiconductor field effect transistors） through lower RDS （ON） （resistance drain to source in the ON state） devices and lowering switching losses through low-frequency operation. However, the incremental improvements in RDS （ON） are at a point of diminishing returns and low RDS （ON） devices have large parasitic capacitances that do not facilitate the high-frequency operation required to improve power density. The drive for higher efficiency and increased power in smaller packages is being addressed by advancements in both silicon and packaging technologies. The NexFET power block combines these two technologies to achieve higher levels of performance, and in half the space versus discrete MOSFETs. This article explains these new technologies and highlights their performance advantage.

Hard Switching Process Optimization for Selected Transistor Suited for High Power and High Frequency Operation

This paper deals with optimization of hard switching commutation mode for high-power, high-frequency consumer applications for selected power transistor. The experimental investigation of suitable settings is outgoing from simulation analysis of hard switching for different transistor structures. For these purposes, the simulation models of power semiconductor switches with high level of validity have been used. After that, the experimental analysis for selected transistor was done with change of parameters that are influencing commutation process of transistor. Target of such kind of analysis was to reach as low switching losses as possible, achieving high power density and efficiency of power system, without utilization of improved switching techniques such as resonant switching. The results confirm that this task is realizable through use of progressive semiconductor devices such as SiC diodes and/or through latest families of MOSFET devices.

Electrochemical Energy Storage Technologies and Applications

The current need to fasten the implementation of renewable energies greatly depends on the development of competitive storage devices, and while there is not a single technology which is likely capable to competitively cover the wide range of possible demands, electrochemical technologies are one of the most promising for many of them. For the realization of this promise, new materials fulfilling criteria such as high energy density, high power density, competitive cost, reliability, and environmental compatibility need to be developed in the near future. Electrochemical energy storage devices can be classified into two main technologies： supercapacitors and batteries （including redox flow batteries）. Materials and applications for these technologies are discussed and compared, listing current status, technical and strategic challenges.

Practical Performance of High Bulk Modulus Oil

Although hydraulic drives have an advantage of high power density, volumetric shrinkage of hydraulic fluids due to pressure causes various disadvantages such as delay of hydraulic response and compression energy loss. Hydraulic fluids of new concept, high bulk modulus oils, have been developed as a new approach to improve the performance of a hydraulic servo system and verified. In this paper, practical performances of high bulk modulus oil, such as oil temperature rise during pump test, air bubbles generation by ultrasonic wave vibration, oxidation stability and anti-wear property, were studied. And the new oil was confirmed to have excellent practical performances besides advantages in pressure response and volumetric efficiency of pumps. Various new applications of the new oil are promising.

Design Consideration for High Power Density GaN Buck-Rectifier in ISOP-IPOS Converter based dc Distribution, System

GaN （gallium nitride） buck-rectifier has been proposed to realize high power density ISOP （input series and output parallel）-IPOS （input parallel and output series） converter-based dc distribution system. The ultra-low loss bi-directional switch can be developed by the GaN power device because of the low on-resistance, the high-speed switching behavior and its own device structure. The buck-rectifier using the GaN bi-directional switches has the potential to achieve higher power density than the commonly utilized boost-rectifier. Availability of the GaN-HEMT （high electron mobility transistor） for the buck rectifier has been verified taking the theoretical limit of the on-resistance and the switching loss energy into account. Design consideration for a high power density buck-rectifier has been also conducted and the application effect of the GaN bidirectional switches has been evaluated quantitatively. The ISOP-IPOS converter-based dc （direct current） distribution system takes full advantage of the buck-rectifier and the rectifier using GaN devices contributes to realizing higher power density dc distribution system.

Modeling Relative Humidity Effects on Power Electronic Performance

Variations in the behavior of power supplies caused electrical behavior dependence with environmental conditions. by environmental conditions require accurate characterization of the This paper introduces models to help predict relative humidity （Rtt） and other environmental factors influence on sensitive circuitry in power electronic systems. The resistivity and permittivity of an insulator have been modeled using different water contents i.e. RH, such model also included the mechanical properties of the design. An application example of a high power density, high voltage DC-DC converter is used to verify the results.

New Approach to Ultracapacitor Technology： What it Can Offer to Electrified Vehicles

Novel carbon-carbon ultracapacitors and hybrid lithium-carbon devices are described. New approach to the design of electrode materials and electrochemical systems followed by the improved design of ultracapacitor cells and modules have resulted in prototypes of superior performance that was verified by independent tests in the Institute of Transportation Studies, UC （ultracapacitor） Davis, in JME Inc., in Wayne State University, and in some other labs. All the test results confirm the superlative performance of the devices developed： carbon-carbon ultracapacitors demonstrate the extremely low inner resistance resulting in the highest power capability and efficiency that also alleviates the cooling requirements and improves safety. Our ＂parallel＂ hybrid devices demonstrate substantially higher energy density than competing LIC （lithium ion capacitor） technologies keeping at the same time the high power density, comparable with the best carbon-carbon ultracapacitors available in the market. In order to make ultracapacitor technology even more attractive to automakers, new organic electrolytes （not ionic liquids） have been developed and are currently under testing at temperatures about 100 ℃ and voltages up to 3.0 V.

High Power Density Three-Level Three-Phase AC-DC 48 V Power Supply

International standards impose several constraints concerning the electric power quality and require that the harmonic content of the line current of grid connected equipment is below assigned limits; for this reason, operating of AC-DC converters with high power factor and low line current distortion has become essential. In this paper, the prototypal realization of a three-phase AC-DC 48 V power electronic converter for telecom system supplying is described and experimental testing results are discussed. The main constraints in the power supply design are the required power density of about 900 W per dm3 as well as the absence of the neutral wire in the supply grid. The carried out investigation is focused on three-level power converter configurations which are considered in order to reduce voltage rating of power switches. As a result of the reduced voltage, low on-resistance metal-oxide-semiconductor field effect transistors can be used in the power stage, solution which allows to achieve improved efficiency as well as increased switching frequency with respect to the insulated gate bipolar transistors based two-level topologies.

Advancement in Materials for Supercapacitors

As future improvement to the energy density and power density of supercapacitors relies on the availability of new materials, worldwide research has been undertaken to address this need. The recent advancement in new materials used for fabricating supercapacitors is reviewed in this paper. Among the newly emerged materials covered in this review are the activated graphene, conductive polymers, CNT （carbon nantotubes）, AC （activated carbons）, carbon additives and metal oxides for EDLC （electric double layer capacitors） and pseudocapacitors applications.

Advanced Asymmetrical Supercapacitors Based on Graphene Hybrid Materials

Supercapacitors operating in aqueous solutions are low cost energy storage devices with high cycling stability and fast charging and discharging capabilities, but generally suffer from low energy densities. Here, we grow Ni（OH）2 nanoplates and RuO2 nanoparticles on high quality graphene sheets in order to maximize the specific capacitances of these materials. We then pair up a Ni（OH）2/graphene electrode with a RuO2/graphene electrode to afford a high performance asymmetrical supercapacitor with high energy and power density operating in aqueous solutions at a voltage of -1.5 V. The asymmetrical supercapacitor exhibits significantly higher energy densities than symmetrical RuO2-RuO2 supercapacitors or asymmetrical supercapacitors based on either RuO2- carbon or Ni（OH）2-carbon electrode pairs. A high energy density of -48 W.h/kg at a power density of -0.23 kW/kg, and a high power density of -21 kW/kg at an energy density of N14 W-h/kg have been achieved with our Ni（OH）2/graphene and RuO2/graphene asymmetrical supercapacitor. Thus, pairing up metal-oxide/graphene and metal-hydroxide/graphene hybrid materials for asymmetrical supercapacitors represents a new approach to high performance energy storage.

Nitrogen-doped black titania for high performance supercapacitors

For energy storage system,it is still a huge challenge to achieve high energy density and high power density simultaneously.One potential solution is to fabricate electrochemical capacitors(ECs),which store electric energy through surface ion adsorption or redox reactions.Here we report a new electrode material,heavy nitrogen-doped(9.29 at.%)black titania(TiO2-x:N).This unique hybrid material,consisting of conductive amorphous shells supported on nanocrystalline cores,has rapid N-mediated redox reaction(TiO2-xNy+zH++ze■-TiO2-xNyHz),especially in acidic solutions,providing a specific capacitance of 750 Fg-1at 2 m V s-1(707 Fg-1at 1 A g-1),great rate capability(503 F g-1at 20 Ag-1),and maintain stable after initial fading.Being a new developed supercapacitor material,nitrogen-doped black titania may revive the oxide-based supercapacitors.

Increased working voltage of hexamine-coated porous carbon for supercapacitors

Highly porous carbon, both unmodified and hexamine-coated on the pore surfaces, is tested at high working voltages in organic electrolyte for supercapacitors in order to enhance the energy density and power density.Sol–gel processing allows for excellent control of the porous structure and chemical composition of carbon,resulting in a material with high surface area and a low level of impurities. This porous carbon can be modified using a simple solution-based method to enhance capacitance. Increasing the working voltage from 2.0 to 3.0 V significantly improves performance for both unmodified and hexamine-coated carbon. The energy density and power density increase at higher working voltage, and under certain conditions, the capacitance increases as well.Cyclic stability is also investigated, with hexamine-coated carbon retaining more of its initial capacitance than unmodified carbon at all working voltages.

Stable Ultrahigh Specific Capacitance of NiO Nanorod Arrays

Previously reported examples of electrochemical pseudocapacitors based on cheap metal oxides have suffered from the need to compromise between specific capacitance, rate capacitance, and reversibility. Here we show that NiO nanorod arrays on Ni foam have a combination of ultrahigh specific capacitance （2018 F/g at 2.27 A/g）, high power density （1536 F/g at 22.7 A/g）, and good cycling stability （only 8% of capacitance was lost in the first 100 cycles with no further change in the subsequent 400 cycles）. This resulted in an improvement in the reversible capacitance record for NiO by 50% or more, reaching 80% of the theoretical value, and demonstrated that a three-dimensional regular porous array structure can afford all of these virtues in a supercapacitor. The excellent performance can be attributed to the slim （〈 20 nm） rod morphology, high crystallinity, regularly aligned array structure and strong bonding of the nanorods to the metallic Ni substrate, as revealed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and X-ray diffraction （XRD）.