硅太阳能电池实验中温度效应的实验研究

硅太阳能电池特性研究是国内众多高校开设的大学物理实验之一。本文研究了温度变化对硅太阳能电池参数测量及最大输出功率造成的不利影响,提出了两种改进方案并进行了实验验证。通过研究发现,在硅太阳能电池表面增加散热装置一方面可以有效地降低该实验中数据测量值的不稳定性,另一方面可进一步提高硅太阳能电池的最大输出功率。另外,本文还研究了温度和温差发电片输出功率之间的关系,并用温差发电片的电流电压补偿硅光电池的输出功率。显然,如将温差发电片补充到硅太阳能电池实验中,可提高硅太阳能电池的光电转换效率。     

菲涅耳聚光下半导体温差发电组件性能研究

采用菲涅耳透镜汇聚太阳辐射,提高半导体温差发电组件的热端温度,冷端利用散热片进行散热.从热流密度的角度建立了半导体温差发电片理论分析模型,实验基于稳态的条件下,忽略冷热端之间以及电臂间的空气对流和辐射,研究菲涅耳聚光下半导体温差发电组件的性能,推导出了半导体温差发电片的温度梯度d T/dx关系式,获得了输出电流、输出功率及热电转换效率的表达式.研究表明:随着电阻比率a(RL/R)的增大,半导体温差发电器件的输出电流I减小,输出功率P和转换效率ηhe先增大后减小,且在a=1时,其输出功率和转换效率最高.随着温差比率b(?T/T_(H2))的增大,无论a取何值,其输出功率P和转换效率ηhe均增大.实验研究中,半导体温差发电片应偏离菲涅耳透镜焦平面一定距离以获得较好输出特性.通过温差发电片的不同串并联组件可获得相应输出电压.     

基于甲烷燃烧的热电转换特性实验研究

本文介绍了基于温差热电转换原理的小型燃烧温差热电转换系统,并通过实验研究了小型甲烷燃烧器的性能特点,并对影响温差发电系统发电性能的因素进行了研究分析.实验表明:小型燃烧器工作稳定可靠,可燃流量范围和着火当量比范围较宽;负载电阻、当量比、输入能量(燃料流量)以及外界换热条件都会对系统的功率输出和效率产生明显的影响.实验中获得了最高569 mW的功率输出和0.55%的系统发电效率.     

半导体温差发电过程的模型分析与数值仿真

本文提出一种新型的半导体温差发电模型,在温差发电过程的数值模拟中考虑了热电单元之间封闭腔体内空气传热的影响.同时进一步运用有限元的数值计算方法对不同电臂对数和不同型号温差发电模型的温度场、电压场进行了数值仿真计算,并对仿真结果进行分析.结果表明:采用127对热电单元模型计算的能量转换效率随冷热端温差增大而迅速提高,与采用1对热电单元模型计算的能量转换效率之差从冷热端温差为20℃的0.39%提高到冷热端温差为220℃时的5.16%,能量转换效率比1对热电单元平均高出3.02%.冷端温度恒定在30℃时,温差发电芯片的输出电压、功率以及能量转换效率均随着电偶臂的横截面积的增大而提高,且电偶臂冷热两端的温差越大提高幅度也越大,而温差发电芯片内阻则与电偶臂横截面积成反比关系,当温差为220℃时对应的输出功率最高达28.9 W.     

SP1848温差发电片的实验研究

用自制的温差发电实验仪测量了 SP1848温差发电片在不同温差(10 ℃、20℃、30℃、40℃、50℃)下的电学输出特性数据。测试结果表明:输出电流与负载R成反比;输出电压先随负载迅速增大,然后逐渐趋于饱和,输出功率先随负载从0迅速增大至最大值(负载电阻8-15Ω区间达到最大值),然后逐渐衰减至0;最大输出功率随温差呈非线性关系,可用二次函数进行拟合。实验结果显示,所制备的温差发电实验装置数据合理,较为准确,可以运用到实验教学中。     

基于塞贝克效应的热电转换装置

温差发电是一种新式的环境友善型能源技术,可以将废热转换为电能.本文设计了基于塞贝克效应的热电转换装置,实现了温差发电.基于单片机系统和OP07芯片设计了有源I/V变换电路,将温差发电输出的电压信号在LCD1602液晶屏上显示,并计算出不同温度差输出的电功率.实验结果表明热电转换输出的电压随着温度差变大而增加,且呈线性关系,单片发电片的热电转换效率达到0.11%,使用热电转换装置可以给用电量较小的设备供电.     

带有压缩机余热温差发电装置的家用空调性能试验研究

世界范围内的能源危机和环境污染日益严重,为了充分利用家用空调系统中的低品位能,提高空调性能,降低空调能耗,对带有温差发电装置的家用空调性能进行了试验研究。试验结果发现:在额定制冷工况下,利用压缩机余热发电装置的空调系统与空调原型机相比输入功率降低43.5W,制冷量提高2.8%,能效比提高9.0%。温差发电装置中发电片冷热端最大温差为17.5℃,平均温差为13.2℃,冷热端温差较小。系统性能还可通过改变冷却方式和优化系统来提高。因此,温差发电技术在家用空调余热回收方面具有广阔的应用前景。     

使用相变换热的温差发电器的数值模拟

为了解决温差发电技术中发电片热端与尾气间传热温差大造成的输出功率和热电转化效率不高的问题,本文提出通过改变尾气与温差发电片热端之间的传热结构,且在结构中充以气液相变工质的方法强化传热,并通过数值模拟的方法比较了加装相变结构前后温差发电器性能的变化。在此基础上,研究了尾气温度、流量及相变换热温差发电器的结构参数对其输出功率及效率的影响规律。结果表明,特定尺寸的相变结构可大幅提高发电器的输出功率及转化效率,但其优化效果受工质蒸发温度的限制。     

聚光光伏与温差联合发电装置的研究

针对太阳能量利用率较低的现状,设计了基于砷化镓多结太阳能电池、半导体温差发电片的聚光光伏与温差联合发电装置.通过测量得出单独聚光光伏发电模块在几何聚光比为75时光电转换效率最大,达31.87%;而在加了半导体温差发电模块之后在几何聚光比为112时系统光电转换效率达32.81%,提高了整体光能量转化电能效率.     

太阳能光伏-温差发电驱动的新型冰箱模型设计与热力学分析

结合太阳能电池温度特性和温差发电特点,设计了一套新的太阳能光伏发电-温差发电驱动的冰箱模型,该模型包括太阳能光伏电池、半导体温差发电模块、电源控制系统等.根据负载用电需求,做出了光伏发电系统的设计方案.采用热力学基本理论,对该模型进行了工作效率及 火 用 效率的分析.结果发现:能效比COP达到了2.73(一般 冰箱COP为2左右), 火 用 效率也达到42.5%.同时,该系统模型环境效益明显,可以减排CO₂ 1394.2 kg,SO₂     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.