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.

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.

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.

Flow Characteristics Diagnosis and Optimization for Dust Collectors Inflow Duct in Thermal Power Plants

火电厂烟风道用于输送烟气、冷风等介质，其设计优化水平不但影响火电厂烟风系统阻力的大小，而且影响与烟风道直接相连的各个设备的运行状态。某600MW机组除尘器前烟道设计不合理，存在磨损严重、进入除尘器烟气分配不均等问题，文中采用标准缸￡模型，利用Fluent求解器对该部分烟道的流场进行数值计算，诊断分析其存在的主要问题，提出的3个改造方案均可使烟道阻力大幅度下降、烟道磨损减轻、进入除尘器烟气分配均匀。同时，研究了缓转半径及烟气流速对该段烟道阻力和烟气分配的影响情况，计算结果表明该段烟道缓转半径宜选在0．875以上，烟气流速对该段烟道的性能基本没有影响。

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.

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。

一种轻薄型光伏/光热集热器性能分析及实验研究

【目的】野外作业和户外生存对能源的需求越来越大,现有常规供能方式存在一些重要缺陷,例如常规发电机需携带大量燃油、蓄电池重量大等。太阳能光伏/光热(photovoltaic/thermal,PV/T)发电技术可有效解决户外生存和野外作业能源缺乏的问题,而现有的PV/T集热器多为刚性结构、重量大而不便于携带。【方法】提出一种基于铜铟镓硒薄膜电池和毛细管网相结合的轻薄型PV/T组件,通过实验的方法研究该组件的集热性能及水流量对组件光电、光热转换效率的影响。【结果】在典型上海气候下,该组件的全天电效率、热效率分别为13.04%、22.50%;在平均辐照度为760 W/m^(2)的实验条件下,水流量为2.1 L/min时,此PV/T的集能性能最优;毛细管网内冷却水可有效降低电池温度(10℃)、提高能量利用效率(23.94%)。【结论】该组件具有高功率密度、轻便灵活的特点,可用于野外作业、户外生存时的能源供给,为户外能源装备的设计提供了新思路。

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。

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.

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。

影响废酸再生装置长周期运行的问题及解决措施

介绍了某炼化公司湿法废酸再生工艺流程,对装置运行过程中影响长周期运行的瓶颈问题进行原因分析,针对装置高温换热器管束开裂、高温除尘器过滤效果不佳、导热盐换热器频繁发生泄漏、导热盐控制阀阀盖泄漏、一级反应器入口烟气风机振动大等问题,采取了相应的整改措施,取得了良好的效果,为同类湿法废酸再生装置提供借鉴。

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。

火星表面薄膜型太阳能集热器设计及应用

为解决火星表面探测器热能短缺挑战,克服火星表面太阳能原位热利用中的性能和环境适应性困难,提出一种基于火面太阳能原位热利用的薄膜型太阳能集热器,热能收集采用高透明聚酰亚胺膜窗和选择性吸收涂层,储能采用3D打印高填充率相变储能装置,并利用半刚性赋形设计、热变形自适应、被动式泄压分别解决火星表面尘积、大温差热交变和星际飞行过程中快速泄压问题。仿真和试验表明,集热器最大光热转化效率为74.9%,日平均集热效率为32.5%~49.8%,单位面积集热量为1105.7~2381.5 Wh/(m^(2)∙sol)(其中sol代表火星日,火星的一个恒星日的平均长度是24小时37分23秒),可适应火星严酷的应用环境。

基于设备互补特性的冷热电系统优化

为提高能源系统综合性能,将地源热泵、光伏和光热等可再生能源集成于以原动机为核心的冷热电系统,并着重对系统设备的效率进行研究。基于设备能量互补特性,提出优化多个设备运行参数,分别是地源热泵供冷启动因子和供热启动因子以及原动机的启动因子来实现整个系统设备效率的提高。将控制多个设备的启动因子结合以电定热运行模式与传统以电定热运行模式进行对比分析,并以单独的地源热泵系统为参考系统,采用黑洞算法对系统进行优化。研究结果表明,与传统模式相比,控制多个启动因子模式系统具有更好的性能。与参考系统相比,耦合可再生能源的冷热电系统性能指标有了较大改善,特别是以启动因子模式运行(年能源节约率达到36.03%;年CO_(2)减排率达到53.24%;年总成本降低率达到36.85%;年综合性能达到42.04%)。

太阳能热发电熔盐槽式集热回路流量分配特性研究

在太阳能热发电站中,抛物面槽式集热系统多回路的流量分配特性对集热工质出口温度和电站运行性能具有重要影响。传统U型集热回路采用调节阀可实现各回路流量的平衡分配,但对系统的控制水平要求较高,且建设成本较大。该文以熔盐槽式集热系统为研究对象,提出采用Z型布置结合母管变径的新型集热回路,以实现多回路流量自平衡;通过开展流量分配的理论设计计算,以及基于Apros软件搭建的集热系统动态仿真模型,研究太阳直接法向辐射DNI、入口质量流量变化以及云遮扰动工况下,Z型集热回路的流量分配、出口温度和回路压降的稳态和动态变化规律。研究结果表明,槽式集热回路Z型布置结合母管变径的方式在稳态和瞬态工况下都具有较好的流量自平衡特性。

不同加热方式下热管接收器传热性能研究

为研究不同加热方式下热管的传热性能,该文设计并搭建一套具有非均匀加热功能的热管传热性能实验测试台架。实验测试加热方式(均匀加热、上表面加热、下表面加热)、加热功率和放置倾角对热管传热性能的影响。实验结果表明:加热功率和放置倾角一定,均匀加热时热管热效率最大,下表面加热时次之,上表面加热时最小;下表面加热时,热管总传热热阻最小,蒸发段传热系数最大,外壁面平均温度最低。无论采用哪种加热方式,随着放置倾角的增大,热管热效率均逐渐减小,总传热热阻逐渐增大,蒸发段传热系数逐渐减小;蒸发段液池区域外壁面温度均明显高于液膜区域;液膜区域,沿高度方向外壁面温度变化较小。

抛物面槽式太阳能集热器热损失因素研究

将太阳能热发电技术与分布式能源系统相结合,有利于加大可再生能源在能源消费结构中的比重。抛物面槽式太阳能集热器是目前太阳能热发电中应用最为广泛的太阳能-热能转化设备,其运行特性决定了太阳能热发电技术与分布式能源系统中其他能源技术是否能够相互协同。因此,针对影响槽式集热器运行特性的热损失,开展了基于现场的规模化实验系统测试工作,验证了所建槽式集热器数学模型,并且进一步应用该模型对真空区残留气体量、风速和吸热体发射率等因素开展了参数比较分析研究。

槽式太阳能集热管弯曲测量及溢出损失分析

槽式太阳能集热管的弯曲变形会造成聚光能量的溢出损失,需要进行测量和分析。提出基于无人机摄影的槽式太阳能集热管弯曲测量方法:采用无人机搭载高分辨可见光相机,实现对槽式太阳能集热管的图像采集;基于边缘检测算法对集热管图像进行处理,最终获得集热管的弯曲变形量。基于光线追迹理论建立槽式聚光器聚光过程数学模型,推导弯曲集热管的溢出损失计算公式。选取3种不同弯曲量的集热管进行测量实验,测得的最大弯曲量分别为1.23、7.75、18.79 mm,平均测量误差为±0.75 mm,计算对应的溢出损失分别为0.02%、0.57%、3.72%,结果表明:集热管弯曲量较大时,会造成较大的溢出损失。