Proposal of a Solar Thermal Power Plant at Low Temperature Using Solar Thermal Collectors

To this day, only two types of solar power plants have been proposed and built: high temperature thermal solar one and photovoltaic one. It is here proposed a new type of solar thermal plant using glass-top flat surface solar collectors, so working at low temperature (i.e., below 100°C). This power plant is aimed at warm countries, i.e., the ones mainly located between -40° and 40° latitude, having available space along their coast. This land based plant, to install on the seashore, is technologically similar to the one used for OTEC (Ocean Thermal Energy Conversion). This plant, apart from supplying electricity with a much better thermodynamic efficiency than OTEC plants, has the main advantage of providing desalinated water for drinking and irrigation. This plant is designed to generate electricity (and desalinated water) night and day and all year round, by means of hot water storage, with just a variation of the power delivered depending on the season.

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.

Solar Thermal Systems Performances versus Flat Plate Solar Collectors Connected in Series

This paper shows the modeling of a solar collective heating system in order to predict the system performances. Two systems are proposed: 1) the first, Solar Direct Hot Water, which is composed of flat plate collectors and thermal storage tank, 2) the second, a Solar Indirect Hot Water in which we added an external heat exchanger of constant effectiveness to the first system. The mass flow rate by a collector is fixed to 0.04 Kg·s–1 and the total number of collectors is adjusted to 60. For the first system, the maximum average water temperature within the tank in a typical day in summer and annual performances are calculated by varying the number of collectors connected in series. For the second, this paper shows the detailed analysis of water temperature within the storage and annual performances by varying the mass flow rate on the cold side of the heat exchanger and the number of collectors in series on the hot side. It is shown that the stratification within the storage is strongly influenced by mass flow rate and the connections between collectors. It is also demonstrated that the number of collectors that can be connected in series is limited. The optimization of the mass flow rate on cold side of the heat exchanger is seen to be an important factor for the energy saving.

Assessment of High Concentrated Photovoltaic/Thermal Collector in Hot Climate

This work investigates the performance of combined hybrid high concentrated photovoltaic/thermal collector (HCPV/T) in Kuwait harsh climate. The proposed system consists of triple junction solar cells (InGaP/InGaAs/Ge) attached to heat source to discharge thermal energy to cooling media. Published HCPV/T models do not consider the effect of shunt resistance which greatly affects the system performance. So, a single diode model employing five parameters including the effect of shunt resistance is adapted to analyze the proposed system. To analyze the thermal performance of the proposed system, a two-dimensional thermal model based on the technique of finite difference is introduced to determine the efficiency of the hybrid HCPV/T system. The present developed subroutines are integrated with other involved codes in TRNSYS software to calculate HCPV/T system efficiency. Electrical and thermal as well as the whole system efficiency at different weather circumstances are evaluated and assessed. The effect of different weather conditions, cell temperature, concentration ratio and the temperatures of the coolant fluid on system performance are studied. Current results indicate that the model of single diode is a reliable one rather than using the two-diode complex model. Compared to measurements provided by high concentrated PV manufacturer, the current results revealed a total root mean square error of approximately 1.94%. Present predictions show that PV cell temperature has logarithmic increase with the rise in concentration ratio but with low values till concentration ratio of 400 suns after that the rise is faster at higher concentration values up to 1500 suns. Results also revealed that hybrid HCPV/T system works effectively specially in severe hot climate where thermal efficiency increases with high surrounding temperature for higher values of concentration ratio. In addition, an increase of approximately 15% in thermal efficiency and 10% in total efficiency can be achieved by utilizing active cooling device in HCPV/T system.

Experimental investigations on the thermal efficiency of a solar air collector with transverse rectangular baffles inclined by an angle of 135°

This work is experimental investigation on the impact of rectangular baffles on the thermo-hydraulic performance of a solar thermal collector.The study was conducted under moderate weather conditions and six cases were studied,including 2M135,6M135,10M135,14M135,18M135,and a smooth plate case.The results showed that the number and placement of baffles plays a crucial role in improving heat transfer and the best cases in terms of thermal performance were cases V and IV,with maximum values of h=15.84 W/m2.k,and h=17.46 W/m2k.The study also found that the heat transfer was greatest at the beginning of the channel and decreased towards the end.The highest thermal efficiency was recorded in case 18M135 with a maximum value ofȠ=0.73.

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。

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%。

太阳能光热发电系统研究现状

针对太阳能光热发电系统,综述了光热发电系统中集热器、蓄热技术以及动力循环的研究及应用现状,并阐述了太阳能混合系统的优势,总结了太阳能光热发电系统面临的关键问题,为光热发电系统的发展提供参考。

抛物面槽式太阳能集热器球形接头测试系统的研制与应用

球形接头是抛物面槽式太阳能集热器的关键部件,针对球形接头易发生运转卡涩和导热油泄漏问题,研制了一套球形接头性能测试系统。该测试系统可以实现球形接头在旋转、摆转或旋摆联动模式下,以及在导热油温度达393℃和压力达4.1 MPa工况条件下的加速寿命测试。以导热油为传热流体,开展了球形接头在导热油温度为393℃和压力为2.3 MPa工况条件,以及温度、压力变化条件下的性能测试研究,分析了球形接头在模拟12年寿命期的扭矩特性和密封性能,验证了该测试系统运行的稳定性和可靠性,并且关键技术参数的控制精度和测量精度满足使用要求,为球形接头的性能评价提供了技术支撑。

基于太阳能分频利用的光伏/光热综合发电系统热力学分析

通过对太阳能聚光投入辐射进行分频,建立光伏与光热驱动有机朗肯循环综合供电系统。在冷却背板温度100℃的限制下,对该系统进行热力学分析,筛选了适宜的循环工质,获得了有机朗肯循环(ORC)系统优化的蒸发温度。结果表明:isobutene作为光伏系统的冷却工质和ORC系统的循环工质时系统效率最高,分频技术将冷却背板散热负荷转移至集热器,可降低光伏板的散热需求,从而降低循环工质质量流量,对提高系统发电能力有积极作用,该系统可将单纯光伏发电效率提高9百分点;同时,分频效率和太阳能电池吸收波段对综合供电系统的总效率影响较大。

源荷置信度水平下光伏光热耦合热电联产系统的调度优化

为提升近用户侧太阳能安装容量,促进太阳能光伏与光热的消纳,提出一种光伏光热耦合的热电联产系统,构建基于能源销售商—用户—系统的主从博弈理论,优化不同置信度水平下用户侧和系统侧的热电平衡关系。案例分析结果显示,使用主从博弈策略达到博弈均衡后,在置信度为0.9的工况下,需求响应后用户侧在高电价时段的用电需求平均减少763 kWh,而在低电价时段用电需求平均增加564 kWh。其中,燃气轮机在09:00时输出最大电能为2.2 MWh,光伏组件在14:00时输出最大电能为2.4 MWh,用户侧的用热需求实现31.6%的削减。通过引导系统侧的设备出力及用户侧的用能需求,系统侧产能更合理,用户侧用能更经济,各参与方均能实现自身利润的最大化。

交叉V型吸热板-底板太阳能空气集热器热性能的数值模拟

应用太阳载荷模型,利用FLUENT软件对九个交叉V型吸热板-底板太阳能空气集热器进行了数值模拟,得到集热器的热效率、出口温度、热损和吸热板温度,并对其进行了对比分析,发现集热器的热效率随着空气流道高度的增大而减小,热损失、吸热板温度和出口温度随着空气流道高度的增大而增大,最大效率为34.60%,最高出口温度为355.13 K.

用于农宅供暖的三角形太阳能空气集热器集热性能研究

用于农宅供暖的太阳能空气集热器均为平板型,通常安装于农宅南墙外侧,但农宅南墙除了门窗外,可用于安装集热器的面积有限,所以集热量也有限。为此,设计一种可安装在南、东、西墙的新型三角形太阳能集热器,以提高对太阳能资源的利用率。基于有限体积-能量法,建立了集热器的光学模型;联合光学模型,构建集热器的动态传热模型,并通过实验验证了模型的准确性;分析了集热器安装在农宅南、东、西墙的集热性能,并与传统贴墙安装平板太阳能空气集热器以及倾斜安装平板太阳能空气集热器进行了对比。结果发现,集热器安装在农宅东墙和西墙的集热量约为安装在南墙的60%和80%;三角形太阳能空气集热器安装在南墙的供暖季集热量比贴墙安装平板太阳能空气集热器高33.5%,比倾斜安装平板太阳能空气集热器高15.0%。

Thermal performance of solar air collector with transparent honeycomb made of glass tube

Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate solar air collector. Experiments are performed for solar collectors with six different honeycomb sizes. The emphasis is to study the effects of diameter and aspect ratio of the honeycomb unit on the transmittance and efficiency of the solar collector. It is shown that for the same diameter but different aspect ratios, there are large temperature differences between the collector’s exits; the smaller the aspect ratio, the larger the exit temperature, with a maximum difference of 10°C; for the same aspect ratio but different diameters, the temperature differences are small; the maximum temperature difference between the collectors with and without honeycombs is 12°C. A theoretical expression for the honeycomb transmittance is derived with a simplified method. The result shows that the honeycomb transmittance is only related with the aspect ratio and the materials’ optical properties but not the actual size of the honeycomb.

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。

太阳能热发电技术与系统

我国对大规模太阳能热发电技术的研究仍处于起步阶段,而国外则已进行了多年的研究。本文介绍了各类太阳能热发电技术及其系统,总结了国内外一些学者的研究成果,比较了各类太阳能热发电技术的优缺点。塔式和槽式技术最适用于大规模太阳能热系统。碟式太阳能热发电装置功率较小,适用于分布式能源系统。其它太阳能热发电技术仍处在试验研究阶段。今后的研究重点主要是塔式太阳能热发电系统的系统集成技术和槽式真空吸热管技术。

中国太阳能中温集热技术进展及应用

在分析太阳能热利用行业发展数据的基础上,对目前应用较为广泛的跟踪型和非跟踪型中温太阳能集热技术的发展研究及标准编制现状进行分析,介绍中温太阳能技术在供热采暖、空调、烟草等行业应用,明确了太阳能中温利用的温区,给出不同形式中温集热器性能提升的建议及应用展望。

太阳能冷热电联供系统的综合性能评价与研究

为了高效利用丰富的太阳能资源,同时满足用户多样化能源的需求,可以采用太阳能实现冷热电联供。当太阳能作为热源或辅助电源时,系统较为稳定且控制方法简单。但是当两种形式同时存在时,会导致太阳能的能源利用率降低且成本升高。因此,需要一种方法对太阳能冷热电联供系统(PV/T-CCHP)的优劣进行评估。提出采用基于Fuzzy-AHP的多目标决策法(MCDM),建立PV/T-CCHP系统指标体系。以传统的分供系统作为参考,从四个角度分别评估了PV/T-CCHP系统运行性能、不同控制策略下的运行性能以及综合运行性能。研究结果可以为PV/T-CCHP系统的设计运行提供参考。

添加固体颗粒提高太阳能集热管内导热油光热转换性能

利用太阳辐照玻璃真空管加热导热油的试验装置,试验研究了添加不同种类和不同质量分数的固体颗粒对导热油光热转换特性的影响,通过测量闷晒温度和闷晒太阳辐照量间接比较了3种试验流体的热性能;理论分析了固体颗粒对导热油吸热与对流传热的强化机理。结果表明：添加铜箔颗粒可提高导热油平均温度14℃;同等试验工况石墨-油分别与铜箔-油和铝箔-油的最大温差达3.3和7℃;质量分数3%-3.2%的铜箔颗粒对提高导热油闷晒温度较有利,增大含量对光热转换的强化效果不明显。石墨-油和铜箔-油显示出良好的光热转换性能。该研究为导热油在太阳能热发电和热管热水器领域的应用提供科学参考。

槽式太阳能聚光集热器传热特性分析

为了研究槽式太阳能集热器的传热特性及为槽式太阳能集热器的设计提供理论依据,该文分析了槽式太阳能集热器的传热特点,建立了槽式太阳能集热器传热过程一维数学模型:利用该数学模型,计算分析了槽式太阳能集热器的传热特性。选取了2014年9月21日、10月25日的太阳直接辐照数据进行计算分析,10月25日太阳直接辐照数据均值比9月21日高37.5894 W/m^2,9月21日集热器吸收的太阳辐射热能计算均值比10月25日高196.644.W/m:接受管内外壁导热量随内外壁面温差升高而增加,接受管外径与内径的比值大于1.05时导热热阻增加到0.0004679 K/(W·m);接受管和玻璃管之问传热主要是辐射换热,辐射换热量随玻璃管内壁面温度升高而增加:对流换热量数值上可以忽略不计,且与接受管和玻璃管之间的环形空间残存气体类型有关,环形空间为氢气的对流换热量大于空气,空气大于氩气:玻璃管对外界的传热主要是辐射换热和对流换热,环境温度每下降lO℃,玻璃管对环境的辐射放热量增加约105 W/m:玻璃外管壁温度为50℃时,风速为6 m/s比0.5 m/s时的对流换热量增加约116W/m,玻璃外管壁温为80℃时,该值增加约为340 W/m;集热器的瞬时热效率随传热工质温度的升高而下降,随太阳直接辐照增加而升高;利用该文建立的数学模型计算的瞬时效率与美国可再生能源实验室的试验数据最大偏差约为3%。