聚光型光伏电池冷却热管蒸发端的数值模拟

针对碟式聚光型太阳能光伏电池效率受温度制约的问题,采用两相闭式热虹吸管(重力热管)散热的方式,工质采用水.热管的蒸发端与聚光太阳能电池接触,其温度场对电池性能和热管效率影响显著.通过FLuENT建立了蒸发端底部的数学模型,计算过程中考虑热流密度、蒸汽饱和温度以及充液量对蒸发端性能的影响.计算结果表明,在聚光倍数为140...     

半抛物槽式聚光分频光伏系统的性能分析

设计了一种包含13层膜系的分频器,建立了考虑太阳张角影响的三维光学模型,研究了分频对半抛物槽式聚光光伏系统的光、热、电性能的影响,得到了系统能量的光谱分布及光伏电池平面能流密度分布.计算结果表明,系统对AM1.5太阳光谱的光学效率为58.7%,对不同聚光镜开口应选择最优电池倾角以获得最均匀的能流密度;采用分频可以降低电池温度提高聚光系统的聚光比以及光电转换效率.     

三结太阳电池在非均匀光照下光斑强度和覆盖比率的优化研究

高倍聚光光伏组件通常采用光电转化效率较高的三结太阳电池.由于聚光器件的非理想性,电池承受的光照分布通常是高度非均匀的,在光伏组件中可通过适当增大光斑与电池面积的比率来降低光照非均匀性对电池电学性能的影响.通过对某一特定三结电池进行电路网络建模计算,分析光斑的强度分布和照射面积对电池的影响,并对比了四种设计方案(均匀光照、非均匀光照、电池效率最大、组件效率最大)下的光斑强度、光斑大小、电池效率以及电池温度分布.对比分析结果表明,组件达到效率最大时的电池效率并不是电池在标准测试条件下的最大效率,而使电池工作在效率最大值的设计方案中组件效率最低.组件效率最大方案中使用的聚光器透镜面积较小,因此该方案将导致组件成本增大.电池效率最大方案中使用的聚光器透镜面积较大并且电池温度最低,故该方案组件成本较低且可靠性较高.这表明在实际组件设计中应充分考虑对发电量的实际需求,选择合适的几何聚光倍数和光斑覆盖电池的比率.     

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.     

几种太阳能光伏发电方案的热力分析与比较

本文建立了平板固定式、数倍聚光式、抛物槽一次反射聚光式、碟式反射聚光分频式和菲涅尔透镜聚光式等五种光伏发电方式的光学系统和辐射能量转换器的热物理模型,进行了能量效率和有效能利用率分析,介绍了与太阳不处于热平衡态的地面太阳光谱辐射能的计算式,分析表明在光电池许可的温度下适当提高聚光比可大幅减少光电池使用面积.     

太阳能分频利用电热联产初步研究

本文对太阳能聚光分频利用电热联产的机理进行了探讨,给出了太阳能光谱有效能函数以及太阳能聚光分频利用电热联产的设计方案,并对该系统进行了热力性能分析,发电投资和成本比较.结果表明,对30倍聚光分频的光伏/光热系统,光伏发电效率约0.095,250～280℃热量利用效率0.14,折算为电的总发电效率为0.139;与普通光伏发电系统相比,单位面积硅光电池发电功率提高约16倍,投资成本仅0.33倍,每千瓦时的发电上网成本可从3.52元降到0.84元,考虑税收后的上网成本将从5.1元降到1.18元.     

减小边缘复合助力28%效率的四端钙钛矿/硅叠层太阳能电池

钙钛矿/硅叠层太阳能电池由于能突破单结太阳能电池的效率极限而吸引了广泛的研究兴趣.然而,在将商业化的大面积硅电池切割为实验室所需的平方厘米级的小面积电池时,会造成显著的效率下降,限制了叠层电池的性能.为了消除传统的激光切割法造成的热损伤和热传导,减少切割后的异质结硅电池的非辐射复合,本工作采用砂轮划片这一冷加工方法,对异质结硅电池进行切割.与采用激光切割法得到的器件相比,冷加工法得到的异质结硅电池的截面损伤小,非辐射复合得到显著抑制,器件的开路电压和填充因子均得到提高,平均光电转换效率提高了1%.将得到的硅电池与正式半透明钙钛矿太阳能电池进行机械堆叠,获得了效率超过28%的四端钙钛矿/硅叠层太阳能电池.     

掺杂Rhodamine 6G的平面波导型PMMA聚光器研制

通过聚光波导提高光的转换和收集效率,是提高太阳能电池效率、减少电池用量、降低光伏发电系统成本的重要途径。利用PMMA作为波导基质材料,Rhodamine 6G(罗丹明6G)作为荧光染料,通过涂覆方法,在表面积为50 mm×50 mm、厚度为5 mm的洁净PMMA衬底上制备出了荧光层厚度约为32 μm的平面波导型聚光器,并研究了荧光染料的掺杂浓度对其聚光比和光伏性能的影响。结果表明,当掺杂浓度为0.250%时,聚光器的聚光比和器件的光伏性能达到了最优,分别为0.45%和0.49%。     

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。     

基于LR305的平面荧光太阳能聚光波导研制

光伏发电是目前太阳能最佳的利用方式之一,但发电成本高。利用聚光结构提高光的转换和收集效率,是提高太阳能电池效率、减少电池用量、降低光伏发电系统成本的重要途径。以Lumogen F Red 305 (LR305) 染料作为荧光材料,将其掺杂到PMMA中,通过本体聚合法制作出尺寸为50 mm×50 mm×5 mm的PMMA平面荧光太阳能聚光波导,对其光学特性进行表征,同时将太阳能电池粘贴到聚光波导的输出端面,通过测试平面荧光太阳聚光波导对太阳能电池性能的影响研究了荧光太阳能聚光波导的聚光特性。     

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.