Reduced graphene oxide modified melamine sponges filling with paraffin for efficient solar-thermal conversion and heat management

A novel type of reduced graphene oxide(rGO)modified melamine sponges(rGS)filling with paraffin(rGS-pf)is developed for efficient solar-thermal conversion and heat management.The microstructures,filling and holding capacity of paraffin in porous rGS,solar-thermal energy conversion and energy harvesting efficiency of the prepared rGS-pf have been investigated systematically.The content of rGO nanosheets coated on the skeletons of rGS-pf is only 0.11%,while the loading content of paraffin in the rGS-pf is as high as 97.53%.Based on the solar-thermal conversion property of rGO nanosheets in the rGS-pf and the heat storage ability of paraffin in the rGS-pf,the proposed rGS-pf provides excellent performance for heat management.The efficiency of solar-thermal conversion could reach up to 92.5%.The thermo-regulation provided by the proposed rGS-pf is real-time,repeatable and long-term stable.The results in this study provide valuable guidance for developing functional materials for efficient solarthermal conversion and heat management.

Optimal Configuration Method for the Installed Capacity of the Solar-Thermal Power Stations

Because of the randomness of wind power and photovoltaic(PV)output of new energy bases,the problem of peak regulation capability and voltage stability of ultra-high voltage direct current(UHVDC)transmission lines,we proposed an optimum allocation method of installed capacity of the solar-thermal power station based on chance constrained programming in this work.Firstly,we established the uncertainty model of wind power and PV based on the chance constrained planning theory.Then we used the K-medoids clusteringmethod to cluster the scenarios considering the actual operation scenarios throughout the year.Secondly,we established the optimal configuration model based on the objective function of the strongest transient voltage stability and the lowest overall cost of operation.Finally,by quantitative analysis of actual wind power and photovoltaic new energy base,this work verified the feasibility of the proposed method.As a result of the simulations,we found that using the optimal configuration method of solar-thermal power stations could ensure an accurate allocation of installed capacity.When the installed capacity of the solar-thermal power station is 1×106 kW,the transient voltage recovery index(TVRI)is 0.359,which has a strong voltage support capacity for the system.Based on the results of this work,the optimal configuration of the installed capacity of the solar-thermal power plant can improve peak shaving performance,transient voltage support capability,and new energy consumption while satisfying the Direct Current(DC)outgoing transmission premise.

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.

Thickness Dependence of Structural and Optical Properties of Chromium Thin Films as an Infrared Reflector for Solar-thermal Conversion Applications

The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.

Magnetic Field-induced Enhancement of Phase Change Heat Transfer via Biomimetic Porous Structure for Solar-thermal Energy Storage

Multifunctional phase change composites are in great demand for all kinds of industrial technologies and applications,which have both superior latent heat capacity and excellent solar-thermal conversion capability.In this research,biomimetic phase change composites are made by inspired by natural systems,successfully getting the high thermal conductivity of carbon foam and magnetism of composites together,to establish a novel solar-thermal energy storage method.The morphology and the thermal characteristics of biomimetic phase change composites have been characterized.The results showed that the maximum storage efficiency of the biomimetic phase change materials increased by 56.3%compared to that of the based materials,and it can further be improved by the application of magnetic field.Meanwhile the heat transfer process of solarthermal conversion and energy storage in biomimetic porous structure under the external physical fields has been explained by simulation.Thus,the magnetic field-induced method applied in this research has better solar-thermal energy storage characteristics within a porous structure by dynamically controlling the magnetism,which has potential uses for various sustainable applications,including waste-heat recovery,energy conservation in building,and solar-thermal energy storage.

Anisotropic hemp-stem-derived biochar supported phase change materials with efficient solar-thermal energy conversion and storage

As cheap and renewable sources,the exploitation of biomass resources was of great value in phase change energy storage.In this study,hemp stems were converted into biochars with three-dimensional multi-level anisotropic pores through a temperature-controlled charring process,which were used as supports for polyethylene glycol(PEG6000)to form shape-stable composite phase change materials(ss-CPCMs).It is shown that the ss-CPCMs using anisotropic hemp-stem-derived biochar obtained at a carbonization temperature of 900℃as a support has high PEG6000 loading rate(88.62wt%),large latent heat(170.44 J/g)and favorable thermal stability owning to its high surface area and hierarchical pores.The biochar-based ss-CPCM also has good light absorption ability with a maximum solar-thermal conversion efficiency of 97.70%.In addition,the different thermal conductivities in the transverse and longitudinal directions of ss-CPCMs reflect the unique anisotropic structure.This work can not only improve the high-value utilization of biochars,but also provide the ss-CPCMs with excellent performance for solar-thermal conversion and storage systems.

An innovative graphene-based phase change composite constructed by syneresis with high thermal conductivity for efficient solar-thermal conversion and storage

Graphene-based phase change composites hold significant potential for solar energy utilization,but their poor thermal conductivity hinders their practical applications.In this work,an air-dried graphene skele-ton(AGS)with excellent thermal conductivity enhancement efficiency was constructed by the ice tem-plating method and syneresis,and the air-dried graphene phase change composite(AGP)was subse-quently obtained through vacuum-impregnating n-Docosane(C22)into AGS.The syneresis effectively re-duced the phonon scattering between graphene sheets within AGS and increased the density of AGS to 0.1701 g/cm3.Therefore,with a graphene skeleton loading of 23.82 wt.%,AGP exhibited excellent thermal conductivity of 9.867 W/(m K),outstanding electrical conductivity of 68.08 S/cm,and remarkable shape stability.Additionally,AGP demonstrated a melting enthalpy of 188.5 J/g and an outstanding solar-thermal conversion efficiency of 93.98%,showing enormous potential for the utilization of solar energy.

Peak-like three-dimensional CoFe_(2)O_(4)/carbon nanotube decorated bamboo fabrics for simultaneous solar-thermal evaporation of water and photocatalytic degradation of bisphenol A

Catalytic CoFe_(2)O_(4) and solar-thermal carbon nanotube decorated bamboo fabrics(CCBF)are fabricated for integrating efficient solar steam generation from wastewater with catalytic degradation of its organic con-taminants.Thanks to the numerous porous channels and polar groups of bamboo fabric and the efficient solar-thermal energy conversion of black carbon nanotubes,the porous and hydrophilic CCBF exhibits fast upward transport of water,efficient solar light absorption,and high solar-thermal energy conversion effi-ciency.The decorated CoFe_(2)O_(4) not only enhances the solar-thermal energy conversion efficiency of CCBF but also activates potassium peroxymonosulfate to generate abundant highly active species for catalytic degradation of bisphenol A(BPA).Furthermore,folding the CCBF into a peak-like 3D evaporator can en-hance solar energy utilization,and gain environmental energy for promoting solar-thermal water evapo-ration and catalytic degradation performances.The 3D CCBF evaporator achieves a water evaporation rate of 2.72 kg m^(-2) h^(-1) under 1-sun irradiation.Meanwhile,100%of the BPA in the seawater can be degraded within 10 min.An exceptional high purification efficiency of 27.72 kg m^(-2) h^(-1) is achieved with the 3D evaporator during a long-term treatment of BPA-containing seawater under 1-sun irradiation.This work demonstrates efficient purification of seawater/wastewater with both metal ions and organic pollutants by simultaneous solar-thermal evaporation of water and catalytic degradation of organic pollutants.

风光热储互补发电系统容量配置技术研究

针对无常规电源支撑的风光热储互补发电系统,协调规划装机容量对提高发电系统运行经济性和利用率具有重要意义。提出了一种双层优化配置方法,上层以最小度电成本及弃电率为目标,确定系统装机容量;下层以新能源发电消纳最大为目标,解决功率分配问题。通过反复迭代寻优,得到系统容量配置;然后;通过纳什谈判对优化结果进行选择;最后,对甘肃河西地区数据进行仿真分析。结果表明:风光热储互补发电系统最优容量配置下的度电成本为0.3064元/(k W·h);风电场加光伏电站装机容量与光热电站装机容量的最优比为6:1,对比相同装机容量的风光互补发电系统,风光热储互补发电系统具有更高的稳定性。

考虑含HRD的光热电站和综合需求响应的综合能源系统低碳经济调度

在“双碳”的背景下,为进一步提升综合能源系统(Integrated Energy System, IES)的经济性和环境效益,文中提出一种在奖惩阶梯型碳交易机制下考虑含热回收装置(Heat Recycling Device, HRD)的光热电站和综合需求响应的IES系统低碳经济调度方法。首先,在源侧构建含热回收装置的光热电站与加装碳捕集的热电联产机组联合运行的IES架构,并分析电转气两阶段的运行原理,建立计及余热回收的电转气设备模型。其次,考虑到负荷侧电、热、气三种负荷的柔性特性,在负荷侧建立电热气综合需求响应模型。最后,引入奖惩阶梯型碳交易机制,进一步减小系统碳排放量,构建调度周期内以含购能成本、运维成本、碳交易成本等系统总运行成本最小为目标的综合能源系统低碳优化调度模型。通过算例分析结果表明,所提方法不仅能提高机组的运行潜力,而且有效降低了系统总运行成本与碳排放量。

太阳能辅助热电联产机组供热、发电及调峰性能分析

针对新能源存在不稳定性导致电网调峰问题日益严重的现状,结合较为成熟的光煤互补发电技术及多热源联合供热调峰系统,设计光煤混合供热发电系统,使热电联产机组具有一定的调峰能力。以某300 MW热电联产机组为研究对象,利用Ebsilon Professional软件搭建发电、供热可灵活调节的太阳能辅助热电联产系统,基于供热机组实际双机运行工况,在保证供热负荷前提下,分析太阳能辅助双机热电联产机组耦合方式,比较耦合前后双机调峰性能。结果表明:凝汽器出口与太阳能集热系统换热器间的管道上设置动态节流阀,改变太阳能集热系统辅助供热机组的运行模式,能够实现发电、供热、调峰一体系统的灵活运行;其中,以太阳能集热系统仅用于补充供暖的运行方式调峰能力最强,太阳能辅助单机供热前后调峰容量比值为0.76,太阳能辅助双机供热前后调峰容量比值为0.55,太阳能辅助承担最大供热负荷的1号机组在调峰容量及调峰补偿上效果最佳。

油田光热利用技术路线及解决方案研讨

在全球气候危机及全国“双碳”目标下,油气田企业加快绿色转型发展,推进低碳化油气生产。化石燃料占油气田生产过程能耗70%以上,光热利用是油气田清洁热力替代的主要方向。通过对工业光热应用领域各种主动式太阳能集热技术特点进行对比,分析油田多种用热环境的温位需求,认为光热技术多样性与油田用热需求多样性具有较高的匹配度。围绕油田多种用热环境,分析了单井拉油热电联供、小规模光热高效替代、大规模光热系统互联共享、复杂用热环境下光热梯级利用等多元化技术路线。针对光热项目在油田落地难度大的问题,从项目筛选、规模确定、系统设计、协同优化、能源管控等方面给出实施路径。油田光热利用方案制定中,因地制宜制定逐步清洁替代顺序是提高替代效益的关键,上下游系统思维及运行策略优化是设计方案优化的前提,严谨的可比性及全生命周期评估是多方案优选的基础,开展各种用热环境的研究实践是提高方案质量的重要路径。建议油田企业在实践中逐步深化认识,持续优化光热利用方案,规模化推动方案落地,进一步推动油气与新能源融合发展。

热流固耦合下不同载荷对光热熔盐泵转子运行稳定性的影响

光热电站熔盐泵转子系统由于其自身结构及外部载荷激励,在极端运行工况下难以维持运行稳定性。针对该问题建立有限元模型,分析了温度载荷、流场力载荷、离心力载荷等对熔盐泵转子的应力变形规律;设置4种不同轴段长度的转子模型,分析不同转子模态振型、固有频率以及临界转速等动力学特性。研究发现:转子结构中最大等效应力出现在首级叶轮叶片进口与前盖板交界处,最大变形出现在首级叶轮前盖板尾缘处,流场载荷与质量力载荷使应力与变形在叶轮上大致呈现中心对称分布,温度载荷使得叶轮产生较大的形变;对首级叶轮进行强度校核后,所选材料满足结构强度要求。模型转子的固有频率随中间轴段长度的增加而降低,湿态转子模型的固有频率略低于干态固有频率;其他转子的一阶临界转速均小于转子的设计转速,只有A9转子的临界转速满足±10%安全裕度,不易在运行过程中发生共振。研究结果对于该类型泵安全稳定运行以及在能源应用等领域具有重要的指导意义。

寒冷地区装配式日光温室保温性能仿真

日光温室的保温性能直接影响农作物产量,为了使其提高产量,需要对保温性能进行分析。但由于需要考虑诸多因素,导致分析过程繁复。因此,提出寒冷地区装配式日光温室保温性能仿真研究,利用数学模型化繁为简。计算温室前段与后段曲率,并构建温度场数学模型,使用二次曲线逼近的方式解析该模型;建立有限元分析模型,根据有限元求解思路计算热传递问题,分别确立稳态和瞬态下的热传递微分方程,设置边界条件;结合热传递情况,使用流体动力学算法,计算流体质量、动量和能量守恒公式,进而获得温室不同节点温度。实验结果表明,目标温室的保温性能良好,模拟出的温度与实际温度相符,能够为温室参数改进提供参考依据。

枯竭油气藏储集库储热供暖耦合CO_(2)封存性能分析

利用枯竭油气藏储存热能并封存CO_(2),既可解决太阳能跨季节储热难题,又可扩大可再生能源供暖占比,同时还可提高CO_(2)地质封存的经济性。提出了枯竭油气藏储热供暖耦合CO_(2)封存的新方案,以CO_(2)作为循环工质,夏季吸收太阳热量储存于油气藏背斜构造中,而冬季取出供暖,建立了储释能过程的数学模型,重点分析了枯竭油气藏储能系统热工性能和CO_(2)封存性能。结果表明:(1)新方案储能系统热工性能优异。单井平均采热功率4808.95 kW,每个采暖季可有效利用的平均储热量49859.21 GJ,平均能量储存密度28984.23 kJ/m^(3)。(2)CO_(2)密度对温度敏感的特性降低了热损失,提高了系统效率。枯竭油气藏储能系统平均能量回收效率95.84%,平均热回收效率83.66%。(3)储能加速了CO_(2)溶解。储释能过程中周期性的注入和采出工作气导致气液界面反复膨胀收缩,增加了气水接触面积,提高了传质动力,加速了CO_(2)在水中的溶解。对比储能模式和仅CO_(2)封存模式,CO_(2)溶解比例增量由0.26%上升至2.22%。枯竭油气藏储热供暖耦合CO_(2)封存新方案既有优异的热工性能,又加速了CO_(2)的地质封存,是一种高值化的枯竭油气藏利用和可再生能源供暖方案,具有大规模推广应用的潜力。

一种新型多功能一体化太阳能利用系统研究

针对轻钢装配式建筑中太阳能技术应用的研究不足,提出一种新型多功能一体化太阳能利用系统.为深入分析系统性能,根据系统特点以及能量转换关系,建立了系统发电效率、发电功率、热效率以及热水温度的理论模型.利用该模型探究了太阳辐照度、热水箱容量、热水箱水温预设值以及系统串联量等设计参数对系统电、热性能的影响.研究结果表明,综合考虑当地太阳辐照度和所需热水温度,合理设定系统热水箱容量、水温预设值以及系统串并联数量,可提升热效率、发电效率.在特定集热器参数下,当太阳辐照度达550 W/m^(2)时系统满足设计要求,此时系统高温阵列热水温度为74.5℃,热效率为52.6%;低温阵列热水温度为52.3℃,热效率为60.4%;发电功率为58 W,发电效率为9.46%;系统太阳能综合利用效率为79.1%,相较于此前文献的研究结果,太阳能综合利用效率提升了30%.该系统为日后太阳能利用系统的设计以及其与轻钢装配式建筑一体化设计提供了一种新思路,对高效利用太阳能具有重要参考价值.

基于改进粒子群算法的定日镜场优化设计模型

定日镜场是塔式光热电站的重要子系统.定日镜的优化布置问题是塔式光热电站建设需要解决的关键问题.以塔式光热电站的定日镜场为研究对象,建立阴影遮挡效率模型、余弦效率模型、截断效率模型以及大气透射率模型,得出定日镜场的光学效率.以镜场年平均输出热功率作为目标函数,建立非线性规划模型,用基于同心圆的粒子群算法进行圆形定日镜场的参数设计及优化求解.通过迭代寻优,找到年平均输出热功率最大时即可找到粒子的特征因子的最优解.

BIPV/T–DSF与新风一体化系统性能模拟研究

为提高光伏光热建筑一体化技术中光伏组件发电效率,充分利用其光热能量,同时满足室内人员对新风的需求,本研究将光伏光热建筑一体化技术与双层皮玻璃幕墙相结合,组成BIPV/T–DSF与新风一体化系统。以沈阳市一间30 m2的卧室为研究对象,通过实地测量室内污染物浓度并进行系统仿真模拟,对室内空气质量状况进行评估,并对系统的热电性能、空气通道内流场的流动特性进行研究。结果表明:系统运行时,冬季热效率达到0.22,电效率达到0.178;夏季电效率由原来的0.151提高到0.156。新风对于室内甲醛浓度有较好的净化效果,系统通风运行20 min后,甲醛浓度即可稳定在0.033 mg/m3。

槽式光热装置承压特种设备损伤模式及检验检测难点分析

本文通过对槽式光热装置的工艺流程及生产特点进行分析,识别出装置存在的典型损伤模式有机械疲劳、热疲劳、熔盐腐蚀、低分子有机酸腐蚀和碱应力腐蚀开裂等。结合槽式光热装置的运行情况和承压设备特点,发现检验检测过程中存在导热油管道长期高温运行无法停机检验检测,核心设备存在多种疲劳损伤模式检验检测要求高及安全评价难等行业难点问题,为保障光热发电领域特种设备安全,亟须加强科技攻关予以解决。

太阳能光热+市电耦合相变蓄能供暖系统测试分析

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