基于太阳能热发电系统效率的最佳运行温度

分别对汽轮机组热机效率和太阳能集热器效率进行了分析,并对热机效率进行了修正,得到了不同状况下的太阳能热发电系统效率和最优运行温度。研究表明:随着太阳辐照度、太阳能热发电系统聚光比的增加,系统效率提高,最佳集热温度升高;然而,当综合传热系数增大时,系统效率下降,最佳集热温度降低;太阳能集热器光学效率的变化,只影响系统效率,对系统的最佳集热温度影响不大。     

太阳能光热与光电/光热系统在中国不同建筑气候带下的性能研究

文章利用TRNSYS动态模拟软件研究了在我国不同建筑气候带条件下,不同类型的太阳能PV/T集热系统和普通太阳能PT集热系统的各项性能。其中,太阳能PV/T集热系统分为基于普通玻璃型太阳能PV/T集热系统和基于Low-e型太阳能PV/T集热系统。文章探究了基于普通玻璃型太阳能PV/T集热系统和基于Low-e型太阳能PV/T集热系统的电、热性能,分析了这两种太阳能PV/T集热器的光电转化效率,以及这两种太阳能PV/T集热系统和普通太阳能PT集热系统的光热转化效率、太阳能贡献率、一次能源节约率、供热节能率和环境效益等参数。分析结果表明:普通太阳能PT集热系统的吸热量、太阳能贡献率、供热节能率和CO₂减排量均高于太阳能PV/T集热系统;与基于普通玻璃型太阳能PV/T集热系统相比,基于Low-e型太阳能PV/T集热系统的发电量降低了3.77%,但热效率、太阳能贡献率、一次能源节约率、供热节能率和环境友好度均较高。     

不同倾角太阳能热水器北京地区热性能试验研究

为确定北京地区不同倾斜角度对紧凑式全玻璃真空管太阳能热水器的影响,本文对不同倾角太阳能热水器集热性能进行试验分析.试验结果表明,相同辐照情况自然循环时,5°～45°倾角太阳能热水器集热性能较为一致,集热性能较好;60°～ 90°倾角太阳能热水器集热性能有所降低,90°倾角热水器集热性能最低.     

改进型微热管平板太阳能空气集热器性能分析

近年来,以空气作为换热介质的太阳能集热器越来越受到重视。本文以微热管阵列为核心传热元件,设计并搭建了改进型微热管平板太阳能空气集热器性能测试系统。通过实验研究了不同空气流量和不同进口温度对集热器集热性能的影响,获得相应参量对集热器的出口空气温度、集热效率和微热管阵列蒸发段温度的影响特性,分析对比了改进前后集热器的集热性能,得到了集热器效率的归一化曲线。实验结果表明,改进型微热管平板太阳能空气集热器在夏季240 m³/h空气流量时集热性能最佳,改进后的集热器相比原集热器在夏季的平均集热效率最高同比提升13.8%;在240 m³/h风量下的平均集热效率最高达到了74%,对应集热器的压降为9.2 Pa。     

太阳能与燃煤机组混合发电系统集成方式的研究

阐述了太阳能与燃煤机组混合发电系统的3种集成方式:太阳能集热场与锅炉并联,太阳能集热场与加热器并联及太阳能集热场与锅炉、加热器二者并联.采用传统的绝对电效率、标准煤耗以及太阳能热发电效率作为经济性指标,并利用热平衡方法对混合系统的热经济性指标进行了计算.以200 MW机组热力系统为例,对3种集成方式下机组的热经济性指标进行了比较,对不同辐射强度下机组热经济性指标的变化规律进行了分析,并确定混合发电的最优集成方式.结果表明:太阳能与燃煤机组混合发电时,太阳能热发电效率高于单纯的太阳能热发电,且燃煤机组煤耗率降低;在3种集成方式中,太阳能集热场与锅炉并联时,太阳能热效率最高、节煤量最多.     

铝幕墙板太阳能集热器的性能研究

研制了一种铝幕墙板与集热元件一体化的新型太阳能集热器,并通过所搭建的测试平台对其集热性能及隔热特性进行了测试研究。通过实验测试,对该集热器在不同工况下的集热性能、隔热特性及其影响因素进行了系统分析,得出了集热器的累积集热量、集热效率、隔热特性等性能评价参数。测试结果表明,铝幕墙板太阳能集热器的平均集热效率为23%,隔热性能优于普通铝幕墙板。该装置具有太阳能集热及隔热功能,为建筑高效利用太阳能,实现太阳能与建筑一体化提供了一种新的工程应用模式。     

太阳能集热及用于提升低品位热能的理论分析

基于热力学第一、第二定律,运用集总热容法对太阳能集热以及太阳能在提升低品位热能的过程中所遇到的问题进行理论分析。分析得出了太阳能集热过程中集热器的集热度B与集热工质温度T之间的函数关系,可用于集热方式的选择。在太阳能热利用中选择性涂层的设计影响着集热的效率,通过分析给出选择性涂层设计的截止波长应位于曲线交叉点处的波长。在提升低品位热能时发现存在集热时间缩短的问题,通过加热容积热容量ρc较小的新工质,形成温差对低品位热能间接加热,提高太阳能的利用率。     

太阳能烟囱发电装置的集热棚集热效率分析

在太阳能烟囱发电系统中,集热棚是影响其发电效率的关键部件之一.为了提高太阳能烟囱发电系统的发电效率,对系统中集热棚集热性能的各种影响因素进行了分析,模拟计算了集热棚的集热效率.     

遮阳板式太阳能相变集热器的实验研究

研制了遮阳板与集热器一体化的新型太阳能相变集热器,通过搭建的实验测试平台对其集热性能及隔热特性进行了实验测试。该建筑构件具备遮阳隔热及太阳能集热功能,为在建筑中高效利用太阳能,实现太阳能与建筑一体化提供一种新的工程应用模式。通过实验测试,对该集热器在不同工况下的集热性能、隔热特性及其影响因素进行了系统分析研究,提出了该集热器的累积集热量、集热效率、隔热特性等性能评价指标。测试结果表明,遮阳板式太阳能相变集热器的平均集热效率可达12.3%,隔热效果优于普通遮阳板。     

定面积集热棚倾角对集热效率影响的数值模拟研究

文章应用计算流体力学方法对呼和浩特地区太阳能烟囱在固定集热棚面积下不同集热棚倾角的棚内空气流动情况进行了数值模拟。由模拟结果可知:在集热棚倾角为0~70°时,空气温度、压力、速度以及集热棚效率曲线有明显变化;在集热棚面积固定条件下,随着集热棚倾角的变化集热棚效率存在较为理想的值,并在达到峰值后持续降低。     

Ray tracing and simulation for the beam-down solar concentrator

The ray tracing equations for the beam-down solar concentrator have been derived in this paper. Based on the equations, a new module for the simulation of the beam-down solar concentrating system has been developed and incorporated into the code HFLD. To validate the ray tracing equations, a simple beam-down solar concentrating system consisting of 3 heliostats and a hyperboloid reflector is simulated. The concentrated spots at the lower focal point of the hyperboloid reflector for the beam-down system are calculated by the modified code HFLD and then compared with that calculated by the commercial software Zemax. It is found that the calculated results coincide with each other basically. Furthermore, a beam-down solar concentrator consisting of 31 heliostats, a tower reflector and a CPC is designed and simulated by using the modified code HFLD. The concentrated spots of the beam-down solar concentrator are calculated.     

Review on Development of Small Point-Focusing Solar Concentrators

The technology of small point-focusing concentrator of solar energy has been developing rapidly in recent years owing to its compact structure and high collecting efficiency. This report presents important developments of small point-focusing concentrator in the past decade. This kind of solar concentrator refers to the parabolic dish concentrator, the point-focusing Fresnel lens, and the Scheffler reflector. Technological advances of these concentrators and the related performances have been presented. There are three main mirror fabrication technologies for dish concentrator, which are high polishing metal, silver-glass mirror and vacuum-membrane. Polymethyl methacrylate is widely used as material in Fresnel lens. Many scholars have proposed new lens shape to improve the uniformity of focusing. The Scheffler reflector has a characteristic of fixed focus, but its design parameters are not perfect so current research focuses on the theoretical calculation of the mirror. In addition, typical applications of the small point-focusing concentrator in photovoltaic system, solar thermal system, solar chemical system, and day-lighting system are summarized. Upon listing the important publications in open literature, a category of main applications of such kind of solar collector is provided based on the working characteristics of the system.     

基于三角腔体吸收器的透射式菲涅尔定焦线系统聚光特性分析

为解决线性菲涅尔太阳能集热系统单轴跟踪过程中出现的聚光焦线偏移以及降低系统跟踪能耗等问题,提出一种透射式菲涅尔定焦线太阳能聚光器.该聚光器采用极轴跟踪方式与线性菲涅尔透镜定期滑移调节方式相结合,可实现固定焦线聚光.将该聚光器与三角腔体吸收器所组成的太阳能集热系统,利用基于蒙特卡罗光线追迹法的TracePro光学软件分析...     

一种新型多曲面复合槽式太阳能集热器的理论分析

提出一种新型槽式太阳能聚光集热器的设计思路,介绍了其工作原理和设计方法。对该集热器的集光比、跟踪精度、高宽比、材料使用量等各方面进行了详细的理论分析,对重要的设计参数进行了分析和优化,给出了大致的取值范围。该新型槽式聚光集热器能够利用多曲面组合实现对太阳光反射聚焦,并具有在反射面上不留阴影、改善高温太阳能接收器的工作性能和工作环境以及有利于提高反射面结构强度等优势。     

Non-concentrating and asymmetric compound parabolic concentrating building façade integrated photovoltaics: An experimental comparison

Concentration of solar energy increases the illuminated flux on the photovoltaic (PV) surface thus less PV material is required. A novel asymmetric compound parabolic photovoltaic concentrator has been characterised experimentally with a similar non-concentrating system. Different numbers of PV strings connected within the system have been analysed and a power ratio of 1.62 measured compared to a similar non-concentrating PV panel with the same cell area. The solar to electrical conversion efficiency of 8.6% and 6.8% was achieved for the non-concentrating panel the concentrating system, respectively. The measured average solar cell temperature of the PV in the concentrator system was only 12 °C higher than that of the similar non-concentrating system with same cell area.     

A comprehensive study of dense-array concentrator photovoltaic system using non-imaging planar concentrator

A special modeling method using Simulink has been developed to analyze the electrical performance of dense-array concentrator photovoltaic (CPV) system. To optimize the performance of CPV system, we have adopted computational modeling method to design the best configuration of dense-array layout specially tailored for flux distribution profile of solar concentrator. It is an expeditious, efficient and cost effective approach to optimize any dense-array configuration for any solar concentrator. A prototype of non-imaging planar concentrator (NIPC) was chosen in this study for verifying the effectiveness of this method. Mismatch effects in dense array solar cells caused by non-uniform irradiance as well as sun-tracking error normally happens at the peripheral of the array. It is a crucial drawback that affects the electrical performance of CPV systems because maximum output power of the array is considerably reduced when a current–voltage (I–V) curve has many mismatch steps and thus leads to lower fill factor (FF) and conversion efficiency. The modeling method is validated by assembling, installing and field testing on an optimized configuration of solar cells with the NIPC prototype to achieve a conversion efficiency of 34.18%. The measured results are in close agreement with simulated results with a less than 3% deviation in maximum output power.     

Theoretical and experimental study on the application of diffuse‐reflection concentrators in PV/T solar system

In order to improve the practicability of PV/T solar system, we proposed the theory and method on the application of diffuse‐reflection concentrator in the PV/T solar system and analyzed the concentration characteristics of this proposed application. In addition, we designed experimental prototype of PV/T solar system and conducted test and analysis of the thermal and electrical characteristics of the PV/T solar system with or without a concentrator, respectively. The results showed that for the PV/T solar system with diffuse‐reflection concentrator, the amount of incident irradiance was increased by an average of 26% during test period, and the 200‐L water in the system was heated to 58 °C, which was 12 °C higher than that of PV/T solar system without diffuse‐reflection concentrator; moreover, the max output power was increased by 11%. Therefore, it is a feasible way to improve the practicability of PT/V solar system by integrating a diffuse‐reflection concentrator. Copyright © 2016 John Wiley & Sons, Ltd.     

Chromatic dispersion concentrator applied to photovoltaic systems

The aim of this paper is to show how it is possible to realise a chromatic dispersion concentrator which collects the different monochromatic components of the solar spectrum separately in subsequently concentric rings in the focal zone. This comes about without an increase in the energetic losses compared to any other type of concentrator. If different photovoltaic elements with energy gaps equal to the photon energy falling on the focal zone are put in the latter, energy losses due to incomplete utilization of the solar spectrum and to incomplete utilization of the energy of a single photon can be drastically reduced. How the losses due to the voltage factor and the fill-factor of the photovoltaic elements of the system can be reduced compared to the normal silicon cells is also demonstrated. The other contributions to losses in the conversion process have only been mentioned, foreseeing their possible variation.     

Performance evaluation of v-trough solar concentrator for water desalination applications

The working principle and thermal performance of a new v-trough solar concentrator are presented in this paper. Compared with the common parabolic trough solar concentrators, the new concentrator has two parabolic troughs which form a V-shape with the focal line at the bottom of the troughs. This is beneficial for the installation and insulation of the receiver, and the shadow on the reflective surface is avoided. The new v-trough collector does not require high precision tracking devices and reflective material. And therefore the cost of the system could be significantly reduced. Various experimental tests were carried out both outdoor and indoor using different types of receiver tubes. The results show that the collector system can have thermal efficiency up to 38% at 100 °C operating temperature. System modelling was used to predict the rate of fresh water produced by four different solar collector systems which include both static and one-axis solar tracking technologies. Comparison of the solar collectors at different temperature ranges for humidification/dehumidification desalination process using specific air flow rate were considered. At each temperature range, suitable solar collectors were compared in the aspect of fresh water production and area of solar collector required. Results showed that the new v-trough solar collector is the most promising technology for small to medium scale solar powered water desalination.     

碟式聚光器的月光聚光比分布计算模型

碟式聚光器和塔式聚光器均是点聚光系统,为了用月光法间接测量塔式聚光系统的聚光比分布,适宜用聚光稳定的碟式聚光器研究不同月相的光源亮度分布对聚光比分布的影响。主要建立月光下碟式聚光器的聚光比分布计算模型,首先依据拍摄的月相灰度图像建立分块均匀的光源亮度分布模型,再基于三维激光扫描点云数据生成准确的反射镜面形;在光线追迹过程中均匀采样镜面上的反射点,且考虑聚光器的跟踪误差;镜面的光学误差与光源的亮度分布合并为等效的光源亮度分布。模拟聚光比分布与实验聚光比分布的余弦相似度α>95%,光学模型准确性高。