共查询到18条相似文献,搜索用时 173 毫秒
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针对聚光型太阳能光伏电池能量转换效率和使用寿命受温度影响较大的问题,基于砷化镓半导体吸收式光纤温度传感器,提出一种对聚光光伏发电系统的温度进行实时监测和控制的方法。数值仿真实验结果表明,当冷却水的流速降低、聚光光伏电池工作温度升高时,半导体的吸收波长增加,光纤温度传感系统检测出来的温度较高,这时可以通过节流阀增加冷却水的流速,提高聚光光伏电池与冷却水之间的传热系数,从而降低聚光光伏电池的温度。该方法对于延长聚光光伏电池的使用寿命和提高太阳能的利用率具有一定的理论指导意义。 相似文献
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文章设计制作了一种智能控制的笔记本外置散热器。该散热器系统上位机(即笔记本)通过串口与下位机(即单片机)通信。上位机采用VB编程自制软件系统,通过计算机管理系统WMI及时获取CPU温度,还可以对下位机及散热器进行控制;下位机通过与串口通信及时获取CPU及周围环境温度,并可单独对散热器电动机进行控制,达到最终降温的目的。该散热器设置有三种工作模式:笔记本CPU温度超过周围环境温度30度;笔记本CPU自身温度超过70度;强制工作模式,即强制启动散热器。散热器启动后可以在1分钟内使CPU温度降低15度;另外该散热器还可以起到清除笔记本内部灰尘的作用。 相似文献
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利用MOCVD方法制备了GaInP/GaAs/Ge叠层太阳电池。测试了I-V特性,并测试分析了该电池性能在30℃至170℃温度范围内的变化情况。测试结果表明,随着温度的升高,短路电流密度略微增大,温度系数为9.8 (μA/cm2)/℃;开路电压以系数-5.6mV/℃急剧下降;填充因子也随之下降(-0.00063 /℃);电池的转换效率随温度升高线性减小,温度从30℃升高至 130℃时,效率从28%下降至22.1%。最后,本文对该叠层电池随着温度变化的特性给予了详细的理论分析。 相似文献
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《中国激光》2015,(8)
光伏电池性能对激光无线能量传输系统设计有重要影响。采用940 nm激光辐照单晶硅光伏电池,研究了光伏电池输出特性随激光强度和电池温度的变化规律。研究结果表明,短路电流随激光功率增加呈现线性增加后饱和的趋势。开路电压和效率与激光功率的关系则呈单峰特性。实验测得光伏电池在293 K时最大效率为29.49%。在283 K~308 K范围内,激光功率较低时,短路电流受温度影响较小,基本保持不变。激光功率较大时,短路电流随温度升高而线性下降。开路电压和效率则随温度升高而线性下降,但下降速率随激光强度的变化而变化。同时仿真了光伏电池效率与串联电阻的关系。结果表明,在强激光辐照下,减小串联电阻,降低复合电流的大小是提高单晶硅光伏电池效率的两个重要方面。 相似文献
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电池组温度对锂离子电池的工作性能和使用寿命等特性影响很大。为研究电池放电倍率以及冷却液流速对电池热管理系统温度分布的影响,本文以18650锂离子电池为研究对象,采用有限元方法仿真分析了在不同放电倍率、不同流动速度下的BTMS温度分布情况,分析造成温度和温差过高的原因。研究结果表明:当冷却液流动速度相同时,放电倍率越大,电池单体温度越高;当冷却液速度在0~0.05 m/s范围内时,增大冷却液流速,电池组最高温度降低越显著;当流速大于0.05 m/s后,冷却液流速越大,电池单体间温差越小,但冷却效果也在逐渐变差。 相似文献
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随着新能源汽车动力电池的能量密度日益提高,一般风冷散热方式难以满足电池散热要求。因此,本文提出了一种新型热管嵌入式动力电池风冷散热模组,在不同工况下对电池最高温度及最大温差进行数值计算,并将其性能与无热管的风冷散热模组进行比较。结果表明,在电池以最大倍率(5C)放电,空气流量为0.03m3/s时,有热管的电池模组对比无热管的电池模组,其电池最高温度降低了7.53℃,电池间最大温差降低了3.48℃,表明该模组满足电池散热要求同时具有更佳的散热性和均温性。通过优化散热器翅片参数可进一步提高该模组的散热性能。 相似文献
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Jinshu Zhang Hongyong Jia Pei-Hsin Tsien Tai-Chin Lo 《Electron Device Letters, IEEE》1999,20(7):326-328
The emitter ballasting resistor is used to equalize the current distribution between the emitter stripes in power transistor, but it will degrade the output power, power gain, and power added efficiency. Experimental results indicate that the current gain of uniform-base SiGe heterojunction bipolar transistors (HBTs) decreases with the increase of the temperature above 160 K, so the current distribution is equalized by itself to some extent. Therefore, the microwave power SiGe HBTs without emitter ballasting resistor were fabricated for the first time, and the continuous output power of 5 W and power added efficiency of 63% were obtained under Class C operation at a frequency of 900 MHz. Hence, the emitter current density of the SiGe HBT's with emitter width of 6 μm is 0.79 A/cm 相似文献
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Cotler A.C. Brown E.R. Dhir V. Shaw M.C. 《Components and Packaging Technologies, IEEE Transactions on》2004,27(2):411-416
We report here the application of water spray cooling directly to the top surface of a lateral diffused metal oxide semiconductor field effect transistor (LD-MOSFET) in a 500-MHz RF power amplifier. With the amplifier running in Class A, spray cooling at a flow of 0.14 l/min increases the output power from 66 W to 84 W, and the power-added efficiency increases from 26% to 34%, all at 34 W input. This improvement is attributed to a large spray-induced reduction in junction temperature and total package thermal resistance. At the point of highest measured RF output and DC power dissipation, the reduction in junction temperature and total thermal resistance were estimated to be from /spl ap/214/spl deg/C to /spl ap/115/spl deg/C and from /spl ap/1.5/spl deg/C/W to /spl ap/0.6/spl deg/C/W, respectively, and the maximum spray-induced heat flux was /spl ap/162W/cm/sup 2/. In Class AB, the increase in output power and power-added efficiency are less, /spl ap/8%, but the amplifier can be driven harder before failure occurs. The maximum output in class AB is 79 W compared to 70 W without spray cooling. 相似文献
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The efficiency of a Schottky varactor frequency multiplier at submillimeter wavelengths can be increased by cooling the diode. The increased mobility of the free carriers causes the series resistance to decrease, and the efficiency can increase as much as a few dB at low input power levels. At high output frequencies and at high power levels the efficiency of the multiplication is decreased by the current saturation, because the junction capacitance cannot be pumped effectively. When the diode is cooled, the maximum current of the diode increases and much more output power can be expected. There are also slight changes in the I -V characteristic and in the diode junction capacitance, but they have a negligible effect on the efficiency of the multiplier. The theoretical maximum output power near 1 THz is calculated to increase by about 10 dB from 50μW to 500μW, when the multiplier chain is cooled to 77 K. However, considerable improvement in the efficiency can be achieved by cooling to 150 K, which is easily attained in space by passive cooling 相似文献
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Daniel Chemisana Joan Ignasi Rosell 《Progress in Photovoltaics: Research and Applications》2013,21(4):444-455
Linear solar concentrators focus radiation onto the solar cell achieving a Gaussian illumination profile. Most of these concentrators use an active cooling system to evacuate the energy not converted into electricity to avoid undesirable overheating. Heat sinks can cause different temperature profiles in the cell depending on the cooling mechanism. Two temperature patterns are most common: the Gaussian and the anti‐Gaussian. The effect of these temperature curves on the cell's electrical parameters has been analysed and characterised numerically and experimentally under different concentrated radiations. A power output increase is shown when the cell is subjected to a Gaussian temperature profile. Contrarily, the cell efficiency decreases more than 3% under the anti‐Gaussian temperature profile. It is demonstrated that it is possible to tailor the temperature profile to maximise voltage output for determined illumination conditions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Mack M.P. Bayraktaroglu B. Kehias L. Barrette J. Neidhard R. Fitch R. Scherer R. Davito D. West W. 《Electronics letters》1993,29(12):1068-1069
The first high power demonstration of an InGaP/GaAs heterojunction bipolar transistor is presented. Multifinger selfaligned HBTs were tested at 3 GHz. A maximum output power of 2.82 W CW was obtained for a 600 mu m/sup 2/ emitter area device (4.7 mW/ mu m/sup 2/ power density) with an attendant gain of 6.92 dB; simultaneously, the device exhibited 55.2% power added efficiency, 69.1% collector efficiency and 8.0*10/sup 4/ A/cm/sup 2/ emitter current density.<> 相似文献
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基于GaInAs/AlGaAs应变量子阱大光腔结构激光器芯片和无氧铜微通道热沉,采用In焊料烧结工艺,制作了976nm大功率连续激光器单条。在20℃热沉冷却条件下,输入电流110A时,输出功率104.9W,电光转换效率达到最大值64%。输入电流300A时,输出功率276.6W,电光转换效率达到54.2%。对激光器单条的热阻以及特征温度进行了测试分析,根据分析结果模拟了激光器单条在大电流下的输出特性,模拟结果显示热饱和是限制激光器最大输出功率的原因。因此,为了提高大功率激光器的输出功率,需要进一步提高激光器的特征温度,并降低热阻以改善散热情况。 相似文献