采用微功耗控制器提高光伏效率

该文从理论上分析了采用太阳自动跟踪控制装置可提高太阳转换效率的空间；并阐述了采用不同于传感器方式的定时跟踪法的电路实现原理。这种电路不仅省去传感器和相关电路的能耗，更重要的是在该电路中可以实现最省电的休眠工作模式，使采用太阳自动跟踪控制装置后提高转换电能成为现实。该文还对比了固定安置的太阳电池板和采用了太阳自动跟踪控制装置的太阳电池板在相同条件下的转换效率。结果得出采用定时太阳自动跟踪装置的光伏发电系统能大幅度提高转换效率。     

基于TRNSYS仿真的不同跟踪方式下CPV/T系统的热电性能及经济性分析

利用TRNSYS软件仿真预测了采用不同跟踪方式的聚光光伏光热(CPV/T)系统在西安、兰州和拉萨这3个地区的全年热、电性能。仿真结果显示,以西安为例,3种跟踪方式中,采用双轴跟踪方式的CPV/T系统的全年热、电效率均最高,分别为40%和11.34%;采用单轴东西向跟踪方式的CPV/T系统的全年热、电效率次之,分别为35.67%和10.74%;采用单轴南北向跟踪方式的CPV/T系统的全年热、电效率均最低,分别为32.19%和10.16%。从动态投资回收期的角度对采用不同跟踪方式的CPV/T系统的经济性进行了评价,计算结果表明,采用单轴东西向跟踪方式的CPV/T系统的经济性最佳,在西安、兰州和拉萨这3个地区,其动态投资回收期分别为4.84、4.93和4.81年;采用双轴跟踪方式的CPV/T系统的经济性次之,在上述3个地区其动态投资回收期分别为5.65、5.69和5.48年;采用单轴南北向跟踪方式的CPV/T系统的经济性最差,在上述3个地区其动态投资回收期分别为6.09、6.26和6.00年。     

超大面积中高温太阳能聚光跟踪技术

介绍了一种新型的太阳能聚光跟踪技术。该技术将数十排或数百面庞大而笨重的聚光镜固定在地上常年保持不动,仅用一套跟踪控制装置即可对这数十排或数百面反射镜同时进行跟踪,不仅使系统的运行稳定性有了质的飞跃,还大幅度降低了制造成本,使太阳能聚光跟踪技术的经济合理性得以实现。     

一种低倍聚光光伏系统的实验研究

提出一种拟抛物面聚光器,利用廉价的聚光器来代替电池组件,以此来降低成本。此聚光系统采用光电跟踪方法使聚光器始终正对着太阳。建立了实验系统,并通过实验分析此聚光光伏系统的性能。     

冷却剂流量对聚光型太阳能光伏系统效率的影响

针对聚光型太阳能光伏电池工作中温度升高会导致发电效率降低的问题,在太阳能模组上铺设有机工质循环管路对光伏电池进行冷却,通过冷凝器对管内有机工质吸收的热量进行收集利用,构建聚光型太阳能光伏/光热综合利用系统。建立传热模型,计算不同日照强度下模组的输出效率并与实验数据进行对比。实验结果表明:发电效率随日照强度的增加先增加后减小;对光伏电池进行冷却可提升系统输出效率;太阳能光伏发电及散热量利用效率合计可达60%。     

两级聚光光伏系统中砷化镓电池特性的实验研究

针对一般聚光系统中光斑不均匀而导致电池性能下降的问题,设计并搭建了具有二级聚光器的碟式聚光光伏发电系统,介绍了系统的结构及工作原理,进行了户外实验。在相同聚光比条件下(150X),与单级聚光系统相比,三结砷化镓光伏电池的平均峰值功率为1.515 W/cm2,平均效率为29.29%,平均峰值功率和平均效率分别提高了23.32%和9.12%。     

考虑太阳张角的聚光器设计北大核心CSCD

通过聚光等形式提高光能密度,减少光伏材料的使用量,有助于保护环境和节约能源。文章提出一种新型聚光器设计方案,其在分析太阳张角对光路影响基础上,对聚光器模型进行改进,并得到接收器上反射光线分布规律。根据节省材料比和聚光硅电池效率选取聚光器参数,建立聚光器三维模型,在TracePro软件中进行仿真,得到接收器表面的辐照度分布和总光通量,与传统光伏聚光器聚光效果对比,验证聚光器模型的有效性,为聚光光伏发电系统的实物设计奠定了理论基础。     

分布式光伏电站系统效率模型分析与研究

基于常州某3.00 MW分布式光伏电站级平台和上海地区单块组件级实验平台的实测数据,建立光伏系统综合效率随辐射量变化的数学模型,得到该电站年综合效率值为59.45%,远低于工程经验值。并从逆变器转换效率、单块光伏组件以及整个阵列的转换效率方面入手分析研究,对光伏阵列工作电压与逆变器MPPT工作电压失配导致电站综合效率受损进行重点揭示,且据此对光伏阵列组件串联数进行优化设计。可为分布式光伏电站的效率分析、设计优化提供理论指导,有利于光伏电站发电量的准确预估。     

太阳能最大功率跟踪装置的设计

本文介绍了太阳跟踪系统的控制原理、控制算法和系统硬件组成,并重点介绍了控制电路的结构和原理,给出了软件的设计思路及主要的程序流程图.同时,在考虑当地的气象基础上设计一种跟踪精度高、结构简单、控制可靠的太阳能跟踪系统.实验结果表明,在太阳辐射强度、环境温度变化时,系统仍能准确地跟踪到太阳能电池的最大功率点,从而有效提高了...     

槽式太阳能聚光集热系统在不同跟踪模式下的对比

根据合肥地区的实测气象数据,采用数值模拟和实验分析相结合的方法,对槽式太阳能聚光集热系统在春、夏、秋、冬4个典型工况下的3种不同跟踪模式(二维跟踪、东西向跟踪和南北向跟踪)的性能进行研究和分析。结果显示:采用东西向跟踪时,系统的集热性能主要受一年四季太阳位置的变化以及太阳辐照强度的影响,夏季时系统集热效率最大,达到0.351,冬季最小,降至0.196;而采用南北向跟踪和二维跟踪时,系统的集热性能主要受太阳辐照强度的影响,其中,南北跟踪时系统效率为0.300～0.312,二维跟踪时系统效率为0.347～0.363。     

双轴跟踪和单轴南北向跟踪CPV/T系统的热电性能研究

分别搭建了采用双轴跟踪和单轴南北向跟踪这2种跟踪方式的聚光光伏光热(CPV/T)系统实验平台,并对不同跟踪方式下的系统的热、电性能进行了测试.在实验条件基本相同的情况下进行了多次测试,结果表明,双轴跟踪C P V/T系统的平均光电转换效率和平均光热转换效率分别为13.0％和52.6％,均高于单轴南北向跟踪C P V/T...     

太阳跟踪装置的双模式控制系统

介绍了用于太阳跟踪装置控制系统中的两种控制模式结构、组成和工作原理。对该模式进行适当设置,即可用于太阳能热水器、太阳能屋顶发电、太阳能干燥器、太阳能电池、太阳灶、太阳能空调、太阳能路灯等各种太阳跟踪装置中,实现双模式控制。双模式控制系统具有较强的通用性和适应性。     

Improving conversion efficiency of solar energy to electricity in cyanobacterial PEMFC by high levels of photo-H2 production

In this study, we described an efficient electrical power generating system containing cyanobacterial photo-H₂ production and custom-built proton exchange membrane fuel cell (PEMFC). The filamentous N₂-fixing cyanobacterium Anabaena cylindrica was used as the photo-H₂ producer. A photosynthesis inhibitor-diuron (DCMU) was used for the enhancement of photo-H₂ production in the culture under argon gas. For the first time, a total of 1.0 μM DCMU was found to be the most effective treatment, as this produced 3.6 fold higher levels of H₂ in microalgae. By measuring polarization curve, the gas mixture collected from the culture was proven to be an effective fuel for electrical generation through a custom-built PEMFC. When the PEMFC was directly combined with the culture tube, the cells generated as much as 843 mV during a 5-day incubation due to the efficient conversion of solar energy to H₂ by A. cylindrica. Light energy conversion efficiency (LCE) for both solar energy to H₂ and solar energy to electricity were also determined. The LCE for the cyanobacterial conversion of solar energy to H₂ reached a peak at four days with a maximal value of 2.05% and an average value of 1.70% ± 0.17. The corresponding LCE for the conversion of solar energy to electricity in this system was 1.13% at peak and 0.94% ± 0.09 on average.     

Maximum power-conversion efficiency for the utilization of solar energy

The overall efficiency of solar thermal power plants is investigated for estimating the upper limit of their practical performances. This study consists of the theoretical optimization of the heat engine and the optimization of the overall system efficiency, which is the product of the efficiency of the solar collector and the efficiency of the heat engine. In order to obtain a more realistic performance of the solar thermal power plant, the solar collector concentration ratio, the diffused solar radiation and the convective and radiative heat losses of the solar collector are taken into account. Instead of the classical Carnot efficiency, the efficiency at maximum power is used as the optimal conversion efficiency of a heat engine. By means of simple calculations, the optimal overall system efficiency and the corresponding operating conditions of the solar collector are obtained. The results of the present work provide an accurate guide to the performance estimation and the design of solar thermal power plants.     

Use of tergitol-7 in photogalvanic cell for solar energy conversion and storage: Toluidine blue-glucose system

Photogalvanic effects were studied in a photogalvanic cell containing toluidine blue, glucose and tergitol-7 as a photosensitizer, reductant and surfactant, respectively. The photocurrent and photopotential generated by this system were 70 μA and 315 mV, respectively. The effects of different parameters on the electrical output of the cell were observed. Current/voltage characteristics of the cell have also been studied, and a mechanism has been proposed for the generation of photocurrent in photogalvanic cell.     

Combination of dark- and photo-fermentation to enhance hydrogen production and energy conversion efficiency

In this study, we investigated a two-phase process of combining the dark- and photo-fermentation methods to reutilize the residual solution derived from dark fermentation and increase the hydrogen yield (HY) from glucose. In dark fermentation, an orthogonal experimental design was used to optimize the culture medium for Clostridium butyricum (C. butyricum). The optimal culture medium composition was determined as glucose 20 g/l, NaCl 3 g/l, MgCl₂ 0.1 g/l, FeCl₂ 0.1 g/l, K₂HPO₄ 2.5 g/l, l-cysteine 0.5 g/l, vitamin solution 10 ml/l, and trace element solution 10 ml/l. In this method, the maximum HY increased from 1.59 to 1.72 mol H₂/mol glucose and hydrogen production rate (HPR) from 86.8 to 100 ml H₂/l/h. The metabolite byproducts from dark fermentation, mostly containing acetate and butyrate, were inoculated with Rhodopseudomonas palustris (R. palustris) and reutilized to produce hydrogen in photo-fermentation. In photo-fermentation, the maximum HY was 4.16 mol H₂/mol glucose, and the maximum removal ratios of acetate and butyrate were 92.3% and 99.8%, respectively. Combining dark fermentation and photo-fermentation caused a dramatic increase of HY from 1.59 to 5.48 mol H₂/mol glucose. The conversion efficiency of heat value in dark fermentation surged from 13.3% to 46.0% in the two-phase system.     

Electrokinetic energy conversion efficiency analysis using nanoscale finite-length surface-charged capillaries

Electrokinetic power generation efficiency using a two-dimensional axisymmetrical model is numerically investigated. A finite-length nanoscale surface-charged cylindrical capillary with reservoirs connected at the capillary ends is considered as the physical domain. The Navier–Stokes, Laplace, Poisson, and Nernst–Planck equations are solved simultaneously to obtain the fluid flow, electrical potential, ion concentration and electrical current in the flow field. The energy conversion efficiency predicted using a one-dimensional model assuming an infinitely long channel, Boltzmann ion distribution and equal ionic electrical mobility is also carried out and compared with the two-dimensional result.     

计算机显示器能效标识制度与能效测试

在计算机显示器能效标准和能效测试的基础上,通过分类统计的方法,分析了被测显示器的能效等级和能效指标的分布,讨论了计算机显示器的能效水平和制约因素,说明能效标识制度的实施促进了计算机显示器的节能进程,并对其节能技术创新具有一定的指导意义。     

Off-design performance analysis of a closed-cycle ocean thermal energy conversion system with solar thermal preheating and superheating

This article reports the off-design performance analysis of a closed-cycle ocean thermal energy conversion (OTEC) system when a solar thermal collector is integrated as an add-on preheater or superheater. Design-point analysis of a simple OTEC system was numerically conducted to generate a gross power of 100 kW, representing a base OTEC system. In order to improve the power output of the OTEC system, two ways of utilizing solar energy are considered in this study: (1) preheating of surface seawater to increase its input temperature to the cycle and (2) direct superheating of the working fluid before it enters a turbine. Obtained results reveal that both preheating and superheating cases increase the net power generation by 20–25% from the design-point. However, the preheating case demands immense heat load on the solar collector due to the huge thermal mass of the seawater, being less efficient thermodynamically. The superheating case increases the thermal efficiency of the system from 1.9% to around 3%, about a 60% improvement, suggesting that this should be a better approach in improving the OTEC system. This research provides thermodynamic insight on the potential advantages and challenges of adding a solar thermal collection component to OTEC power plants.     

Theoretical upper limit to the conversion efficiency of solar energy

The theoretical maximum useful work obtainable from solar energy has been calculated taking account of its directional character. The method employed is the calculation of the availability of a thermodynamic system containing such energy in an environment corresponding to the earth's surface. The corresponding efficiency is where T_o is the ambient temperature, T_s the equivalent solar temperature and δ the half angle of the cone subtended by the sun's disc.