An Evaluation to the Performance of Evacuated Tube Solar Heaters for Arid and Hot Areas

Solar energy applications could be the best alternative to the conventional fuels for the purposes of domestic,water and space heating and some industries in the sunny,arid,and hot areas.In the present study,the performance of an evacuated tube solar heater for water heating for months of February and March was experimentally investigated.This was performed in a hot and arid area(Nasiriya City,South of Iraq).A solar heater with ten evacuated tube solar collectors with a capacity of 100 liter was used in the experiments.Each evacuated tube had a length of 1.8m with an outside diameter of 8 cm.It was observed that for the two selected months,water temperature of the solar heater reached a maximum more than 70°C during sunny days with no heat extraction from the tank of the solar heater.Moreover,heat was extracted from the solar collector with four different flowrates 0.5,0.75,1,and 1.25 l/min,respectively.The results showed that temperature of the solar heater behaved differently from the static situation.When the heat extraction begun,there was a gradual and noticeable decrease in the water temperature of the heater.The observed decrease was slight with the lowest flowrate(0.25 l/m)and becomes sharp with the highest flowrate(1.25 l/min).However,water temperature of the solar heater remained higher than 40°C for the investigated flowrates except the case of 1.25 l/min.The results showed that evacuated tube solar heater can work efficiently in arid and hot areas in winter and spring seasons when the conditions of solar radiation are suitable.

In-Situ Preparation and Thermal Shock Resistance of Mullite-Cordierite Heat Tube Material for Solar Thermal Power

In order to improve the thermal shock resistance of solar thermal heat transfer tube material, the mullite-cordierite composite ceramic as solar thermal heat transfer tube material were fabricated by pressureless sintering using a-Al203, Suzhou kaolin, talc, and feldspar as starting materials. The important parameter for solar thermal transfer tube such as water absorption （W）, bulk density （Db）, and the mechanical properties were investigated. The phase composition and microstructure of the composite ceramics were analyzed by XRD and SEM. The experimental results show that the B3 sintered at 1 300 ℃ and holding for 3 h has an optimum thermal shock resistance. The bending strength loss rate of B3 is only 2% at 1 100℃ by air quenching-strength test and the sample can endure 30 times thermal shock cycling, and the water absorption, the bulk density and the bending strength are 0.32%, 2.58 g·cm-3, and 125.59 MPa respectively. The XRD analysis indicated that the phase compositions of the sample were mullite, cordierite, corundum, and spinel. The SEM images illustrate that the cordierite is prismatic grain and the mullite is nano rod, showing a good thermal shock resistance for composite ceramics as potential solar thermal power material.

Enhanced efficiency in Concentrated Parabolic Solar Collector(CPSC) with a porous absorber tube filled with metal nanoparticle suspension

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector(CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction(φ), Darcy number(Da) and Rayleigh number(Ra), on the Nusselt number(Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe_3O_4, Al_2O_3, TiO_2.With the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.

Performance of Water in Glass Evacuated Tube Solar Water Heater under Kenya Climatic Condition

Solar water heaters which provide a cost-effective and environmental friendly approach to hot water generation are in widespread application. Evacuated tube solar water heaters perform better than flat plate solar water heaters as a result of their greater surface area exposed for sunlight absorption. Water-in-glass evacuated tube solar water heaters are widely used as compared to heat-pipe solar water heaters due to their short payback periods. In this study, the performance of water-in-glass evacuated tube solar water heater is investigated through experiments under the climatic conditions in Kenya. The results revealed a daily efficiency range of 0.58 - 0.65 and a daily final outlet temperature greater than 55°C given an initial temperature of 25°C.

CdHgTe Quantum Dots Sensitized Solar Cell with Using of Titanium Dioxide Nanotubes

The sensitization of TiO2 nanotubes with CdHgTe quantum dots (QDs) was applied by using the direct dispersion technique. The CdHgTe-QDs were fabricated with different Hg% ratio in organic medium for controlling their particle size. While TiO2 nanotubes (NTs) were fabricated by anodization technique. The QDs and NTs were characterized using SEM, TEM and UV-VIS spectrophotometer. In this work, the photovoltaic parameters of the quantum dots sensitized solar cell (QDSSC) depend mainly on the Hg% ratio in the QDs. The most efficient QDSSC was obtained at 25% of Hg ratio with Jsc of 4 mA/cm2, Voc of 0.63 V, FF of 0.32 and efficiency of 0.81%.

全玻璃真空太阳集热管关键技术参数研究进展

全玻璃真空太阳集热管是太阳能热利用系统的重要组成部分,其性能参数的优劣直接影响到太阳能热利用系统的热性能、耐久可靠性和节能效果。文章从真空管基本结构和工作原理的介绍出发,对影响真空管性能的光学性能、热性能等关键技术参数及玻璃管材料、真空性能等其他技术要求的研究进展做了详细分析,并在长期从事科研和检测工作的基础上,给出了提升真空管的产品性能可从玻璃管生产优化、新涂层开发、真空性能加强、技术创新、先进设备开发、标准修订等方面的建议。

矩形翅片管糖醇相变储热器传热性能分析

对糖醇基矩形翅片管相变储热器传热性能进行数值模拟与实验研究,利用数值模型研究传热流体入口温度、流量以及储热器翅片间距、管间距等参数对充放热性能的影响。研究表明:从运行参数看,由于相变材料导热系数的影响,翅片强化区外流体入口温度与材料相变温度的温差对充放热速率呈正相关;在管内湍流条件下,管内流速在高于0.53 m/s时,不能显著提升储热器的充放热速率;从结构参数看,增加翅片可显著提升翅片区内充放热速率,翅片间距小于10 mm和管间距小于52.5 mm对充放热速率影响不明显。

级联型潜热储存耦合热泵系统性能研究

为提高太阳能利用率和热泵热力学性能,将真空管集热器、热泵和填充床等结合,提出一种级联型潜热储存耦合热泵系统用于建筑供热。针对太阳能集热及室外温度等条件,将太阳能蓄热和室外空气作为热泵的热源进行系统集成设计。在FLUENT和EES中分别建立填充床和热泵的热力学模型,并分析填充床的换热流体流量、放热温度和用户回水温度对系统热力性能的影响。结果表明,填充床流体流量从0.05 kg/s增至0.07 kg/s时,热泵系统整体平均性能指数下降0.16;填充床作为热源的放热温度升高20℃时,填充床供热增加74269 kJ,有效放热率下降21.9%;当用户回水温度升高10℃时,热泵系统整体平均性能指数下降0.19,有效放热率下降16.2%。

太阳能真空集热管热损分析与试验研究

基于热平衡法提出了一种动态热平衡热损计算方法,并进行了验证,同时分析了环境温度、进口温度、流量对真空集热管热损的影响。结果表明,热损随着环境温度的降低、进口熔盐温度的升高和熔盐质量流量的降低而增大;当辐照强度在700 W/m2以上时,真空集热管获得的热量大于热损并能稳定工作,说明槽式光热电站在东南沿海等太阳能资源相对不足的地区有一定的适用性。

新型槽式太阳能真空吸热管设计方法及其光学性能研究

针对传统槽式太阳能集热系统工质运行温度受限,以及真空吸热管表面能流密度分布不均而引起的热应力过大等问题,文章在不改变聚光器结构的条件下,提出了一种新型的槽式太阳能真空吸热管的设计方法,通过减小金属内管直径、下移金属内管位置以及在金属内管上方加装双曲线型二次聚光器来提高太阳能聚光比,改善了金属吸热管表面能流密度分布。利用仿真计算方法研究了新型槽式太阳能真空吸热管的光学性能,结果表明:和传统槽式太阳能真空吸热管相比,该新型结构在仅损失1.88%光学效率的情况下将聚光比从62 kW/m^(2)提升至71 kW/m^(2);能流密度分布均匀度改善了55.05%,提升了聚光-吸热系统的整体性能。

内聚焦真空管集热器热泵系统实验研究及分析

本文提出了一种集热蒸发器为内聚焦真空管的直膨式太阳能热泵来提升系统性能,并搭建实验台获取实验数据,深入研究不同工况下系统的热力学性能。结果表明,太阳辐照强度对系统性能影响显著,当太阳辐照强度由400 W/m^(2)上升到800 W/m^(2)时,系统COP由4.18升至5.34,集热效率由0.94降至0.67,此时系统损由1175.33 W升高到2290.27 W,系统效率由16.82%下降到11.99%,此外循环水入水温度和环境温度对系统的性能影响远小于太阳辐照强度。集热蒸发器是系统从太阳辐射获取能量的部件,对它的设计优化将有助于改善系统性能。

全玻璃真空管型太阳能热水器在嘉兴地区节能量与减排量分析

为评估太阳能热水器对“双碳”战略的贡献,减少对化石燃料的依赖,推动能源结构的优化和转型升级,在嘉兴地区通过对全玻璃真空管型太阳能热水器在实际使用工况下进行热性能测试分析.试验结果表明:在实际使用工况下,环境温度和辐照量是影响太阳能热水器日有用得热量的重要因素;78和75管间距的年节能量分别为451.87 kWh/(m^(2)·a)、467.46 kWh/(m^(2)·a),CO_(2)年减排量分别为338.9 kg/(m^(2)·a)、350.6 kg/(m^(2)·a),经估算2021年太阳能光热利用CO_(2)减排量约占全国碳排放总量的12.6%.

内插式真空管集热器集热性能提升技术研究综述

真空管太阳能集热器是太阳能热利用的重要途径。内插式真空管集热器是一种结构优化后的真空管集热器,为提升其集热性能,介绍了内插式真空管集热器的工作原理,对其传热机理进行了分析,归纳了当前对内插式真空管集热器的集热性能的研究现状,并在此基础上通过建立集热效率关于环境参数及流量的关联式、改进内插管主管和支管管径尺寸、综合优化集热器布置方式及管间距并设置反射板的方式等方法分析了存在的问题,为低成本、高效率的内插式真空管集热器的研究发展提供了参考依据。

管式PECVD工艺对“SE+PERC”晶体硅太阳电池镀膜均匀性的影响及改善研究

针对在“SE+PERC”晶体硅太阳电池制备过程中,采用管式等离子体增强化学气相沉积(PECVD)工艺沉积正面钝化介质膜后,硅片正面会出现角部发红色差,即镀膜均匀性异常的问题,通过实验,对硅片厚度、工器具状态、背面膜层结构、正面钝化介质膜沉积工艺等影响因素对硅片正面角部发红色差的影响分别进行分析和讨论,并提出解决方案。研究结果表明:硅片正面角部发红色差的产生与硅片自身厚度、工器具状态、背面膜层结构、正面钝化介质膜沉积工艺均存在一定关系。通过采用最具优势的管式PECVD工艺条件,即优化自动化装片技术、控制石墨舟形变量、采用合适的背面膜层结构,以及正面钝化介质膜沉积工艺采用高射频功率叠加高腔体压力,可将正面角部发红色差硅片的占比降低至0%,从而可有效提升“SE+PERC”晶体硅太阳电池的成品率,提升生产线的经济效益。

Study of the Solar Energy Drying Device and Its Application in Traditional Chinese Medicine in Drying

Background: We referred to nearly 40 years of development and application progress of solar dryer in China literature, especially its application in the field of Chinese herbal medicine drying. Objective: We explored the development direction of China’s development and application of solar dryers, especially focusing on its development and application in traditional Chinese medicine drying. Method: Five types of solar dryers including the greenhouse type solar dryer, the collector type solar dryer, the collector-greenhouse type hybrid solar dryer, the integrated solar dryer and the focusing type solar dryer accounted for the development and application of solar dryers up to 95% in China. The first three types of solar dryers are low temperature dryer (less than or equal to 70°C), while the latter two kinds of solar dryers are high temperature dryer (more than 70°C). In this paper, we respectively introduced and compared the structure, working principle, applications, advantages and disadvantages, and the research status of these five dryer. Results: The integrated solar dryer and the focusing type solar dryer belong to the high temperature dryer types are the future direction of development. Among them, the integrated solar dryer is relatively simple structure and has more promotion prospects. These two kinds of key drying device used in the dryer is the development direction of high efficient vacuum tube. On the other hand, because of their low cost, simple structure and the dry material requirements etc., the three types of low temperature dryers at low temperature for drying materials are also indispensable in the practical application. In contrast, the collector-greenhouse type hybrid solar dryer has more advantages, is the development direction of low temperature drying category. Conclusion: The collector tube which is the key element of the dryer was the core technology of solar dryer. Our country develops more successful of the all-glass vacuum solar thermal collectors and heat pipe-glass vacuum tube. Efficient vacuum tube collector technology is the future developed direction and is equally important to improve the quality of traditional Chinese medicine and dried.

Feasibility Study of Solar Energy Steam Generator for Rural Electrification

In Middle East region, where there are plentiful amounts of solar radiation and great desert areas, solar energy can play a potential role in replacing conventional fuel-operated electricity generation methods with a cost-effective, sustainable solution. This paper presents a feasibility study of a low-cost solar energy steam generator for rural areas electrification. The proposed system is based on the use of trough concentrator which converts solar radiation into thermal energy in its focal line (where a receiver pipe is installed with a fluid flowing in its interior). The aim of the paper is to predict the feasibility and potential for steam generation using a stand-alone solar concentrator with a small dimension for domestic and small-scale electricity generation. The study presented here is based on modelling of the system to determine the points at which the system is expected to produce sufficient steam energy at the tube outlet to drive a steam engine for producing electricity. Results are presented in graphical forms to show the operating points and the effect of changing selected input parameters on the behavior of the system in order to set some limits (boundaries) for such parameters. Results show that among the three input design parameters selected, the tube diameter is the most dominant parameter that influences steam energy, then the tube length and finally the flow rate of the water passing through the tube. The results of this paper can provide a useful guideline for future simulation and/or physical implementation of the system.

Manufacturing and Thermal Performance Test of (Compound) Solar Collector in Damascus City

Solar water collectors that uses for domestic and industrial applications within temperature up to, are classified under two main types: Flat Plate collector (FP), and Evacuated Tube collector (ET). Thermal performance test results showed that each type have different thermal features. Comparison between (FP & ET) collectors showed that they could take advantages of different thermal features of two types when they work in the same climatic conditions and overlap of these thermal features when they work in different operational conditions. They can take advantage of these features through (compound) solar collector. Compound solar water Collector (CO) composed of a part of flat plate collector shape (FP), and a part of evacuated tube collector shape (ET). Booth have equal reference area, and connected together to be as one Solar collector (CO). Water entered first flat part (FP), then evacuated tube part (ET) then to tank or end-use. In this paper, present design and manufacturing as well the thermal performance test of (compound) solar collector, according to Standard Specification of tests, was EN12975:2001. Mechanical test for (CO) collector conducted successfully according to durability, reliability, and safety requirements. In addition, thermal performance was tested in steady state at the climatic conditions of Damascus city, and concluded the thermal performance of (FP & ET) that constitute (CO) collector. The results showed enhancement of thermal performance.

Performance and Optimization of a Small Hybrid Solar-Thermal Collector

A hybrid solar collector was designed to investigate the effects of combining two different solar collector techniques on the overall collector’s effectiveness. While most solar collectors focus only on one solar collection method, the small hybrid system uses a flat plate collector in conjunction with five evacuated tubes to absorb the most energy possible from both direct and diffuse solar radiation. Data was collected over four months while the system operated at different flow rates and with various levels of available insolation from the sun to evaluate the performance of the solar collector. To understand the relative contribution of the flat plate collector and the evacuated tubes, temperature differences across each part of the system were measured. The results indicate the average first law efficiency of the hybrid system is 43.3%, significantly higher than the performance of the flat plate alone. An exergy analysis was performed for this system to assess the performance of the flat plate system by itself. Results of the second law analysis were comparable to the exergetic efficiencies of other experimental collectors, around 4%. Though the efficiencies were in the expected range, they reveal that further improvements to the system are possible.