The Effect of Annealing under Non-vacuum on the Optical Properties of TiAlN Non-vacuum Solar Selective Absorbing Coating Prepared by Cathodic Arc Evaporation

TiAIN solar selective absorbing coatings which were deposited on 304L stainless steel using cathodic arc evaporation method were annealed under non-vacuum at different temperatures with different times. The optical properties （absorptance and emittance） of the coatings were measured by a spectrophotometer. It was found that, after being annealed for 2 hours at different temperatures, the absorptance of the coatings reached the highest value of 0.92 at 700 ℃ while the emittance got the lowest value of 0.38 at 800 ℃. When the coatings were annealed at 600 ℃ for 24 hours, the optical properties changed to 0.92/0.44 （absorptance/ emittance）. By measuring the structure, morphology, elements and surface roughness of the coatings, it was found that both the elemental composition and the surface roughness of the coatings changed as a result of annealing, and these changes caused the change of the optical properties of the coatings.

A review of high-temperature selective absorbing coatings for solar thermal applications

Solar selective absorbing coatings directly harvest solar energy in the form of heat.The higher temperatures are required to drive higher power-cycle efficiencies in favor of lower costs of energy.According to different dielectrics,high temperature coatings can mainly be divided to double cermet solar selective coatings,transition metal nitride multilayer coatings and transition metal oxide multilayer coatings.This paper assesses the photothermal conversion efficiency and thermal stability,and discusses the challenges and strategies of improving both thermal and optical properties.Double cermet layers can stabilize nanocrystalline structures by alloying,while transition metal nitride/oxide layers generally choose the reliable materials with superior mechanical properties and thermal stability.The purpose of this review is to get the optimized systems,and propose further research directions at higher temperature,such as all-ceramic absorbing coatings.

Optical Design and Preparation of High Performance Mo/NiAlN/NiAlON/SiO_2 Solar Selective Absorbing Coating

A new solar selective absorbing coating of Mo/NiAlN/NiAlON/SiO_2 multilayer was prepared on stainless steel(SS) substrates by magnetron sputtering for solar thermal power applications. The optical constants and thickness of individual layers were simulated using the Scout software based on the experimentally measured reflectance and transmittance spectra of individual layers. The coating of Mo/NiAlN/NiAlON/SiO_2 with an ideal solar absorptance(α) of 0.945 in the solar spectrum range was designed via the optical constants of each layer in the Scout software. The Mo/NiAlN/NiAlON/SiO_2 coating was deposited via the optimized layer thickness. A good spectral selectivity with absorptance(α=0.936) and emittance(ε=0.09, T=80 ℃) was obtained. This method, which incorporates the optical simulation with the related experiments, provides a convenient approach to obtain the ideal solar selective absorbing coatings.

Preparation of solar selective absorbing CuO coating for medium temperature application

A new method of preparing CuO solar selective absorbing coating for medium temperature is presented.After pretreatment,brass was overlaid with CuO by chemical plating.The effects of reactant concentration,reaction tem-perature and reaction time on the absorptivity of CuO coating were investigated.The optimized condition of preparing CuO coating was obtained.The CuO coating was analyzed with X-ray photoelectron spectroscopy(XPS)and scanning electron microscopy(SEM).In order to prolong the period of use,the CuO coating was protected by TiO2.The experi-ment shows that the TiO2/CuO coating is more heat-resistant,acid-resistant,and wear resistant than CuO coating,without losing absorptivity markedly.The TiO2 coating can reduce emissivity and protect the CuO coating.

The Impact of Annealing Temperature on the Optical Performance of Cr-Cr_2O_3 Produced by Plasma Spraying as Solar Energy Selective Absorber Coating

A series of selective solar absorber coatings of Cr-Cr2O3 were deposited in different content on stainless steel by plasma spraying.The samples were annealed at different temperatures.The optical performance(both the solar absorptance and the thermal emittance)were studied by spectrophotometry.The surface morphology,the structure and the surface roughness were investigated by scanning electron microscopy(SEM),X-ray diffraction(XRD),and roughmeter respectively.The results show that,as the content of Cr increased,the solar absorptance(α)decreased greatly,from 0.91 to 0.84.Meanwhile,the thermal emittance(ε) decreased more greatly,from 0.86 to about 0.64.The ratio between the solar absorptance and the thermal emittance increased from 1.06 to 1.31.Annealing had a great impact on the optical performance.Annealing temperature is an important element.But its influence was a little complex.To pure Cr coating,annealing at 500℃ was a perfect chosen,where the ratio between the solar absorptance and the thermal emittance was highest of 1.46.

Thermodynamic analysis on medium-high temperature solar thermal systems with selective coatings

Thermodynamics analysis was carried out for solar thermal receivers with different selective coatings.The relation between the energy conversion efficiency of a medium-high temperature solar thermal system,the spectral properties of selective coating and the operating temperature of the receiver were discussed.Furthermore,the relation between the optimum operating temperatures,the exergy efficiencies and the incident solar flux were analyzed for the traditional concentrating system and concentrating beam splitting system,respectively.According to the analysis results for the thermal receiver with blackbody surface and selective coatings,the optimum cutoff wavelength was obtained for the ideal selective coating.An analysis method for the optimum operating temperature calculation was developed for thermal receivers with selective coating.The optimum operating temperature for an actual selective coating was analyzed on the basis of the proposed theory.

Greatly enhanced solar absorption via high entropy ceramic AlCrTaTiZrN based solar selective absorber coatings

High entropy alloys(HEAs),which is at the expense of high cost compared to traditional alloy,should not be confined to the mechanical properties,but should be employed to devise a novel combination with unique functional and mechanical performances.In this work,high entropy alloy nitride(HEAN)is utilized as a novel double absorption layer to improve solar absorption in the high temperature solar selective absorbing coatings(SSACs).Our primary motivation is to lower thermal emittance(ε)and enhance solar absorptance(a).In order to realize this goal,coating design(CODE)software is employed to design and optimize the proposed HEAN based SSACs using appropriate dielectric function model.The ultimate as-deposited coating shows good optical properties with a high a value of 0.965 and a lowεvalue of 0.086(at 82C).The estimate of thermal stability tests indicates that HEAN based SSACs has the ability to resist instability in high working temperature,which keeps good optical properties(a¼0.925,ε¼0.070)after annealing at 600C for 10 h.

Selective Absorber Coatings and Technological Advancements in Performance Enhancement for Parabolic Trough Solar Collector

Parabolic trough solar collector systems are the most advanced concentrating solar power technology for large-scale power generation purposes. The current work reviews various selective coating materials and their characteristics for different designs in concentrating solar power. Solar selective absorbing coatings collect solar radiation and convert it to heat. To promote higher efficiency and lower energy costs at higher temperatures requires, this study aims to analyse the fundamental chemistry and thermal stability of some key coatings currently being used and even under investigation to find reasons for differences, information gaps and potential for improvement in results. In recent years, several novel and useful solar absorber coatings have been developed. However, qualification test methods such as corrosion resistance, thermal stability testing and prediction of service life, which have essential technical value for large-scale solar absorbers, are lacking. Coatings are used to enhance the performance of reflectors and absorbers in terms of quality, efficiency, maintenance and cost. Differentiated coatings are required as there are no uniformly perfect materials in various applications, working conditions and material variations. Much more knowledge of the physical and chemical properties and durability of the coatings is required, which will help prevent failures that could not be discovered previously.

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。

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.

太阳能选择性吸收涂层的失效机制及优化策略

在光热系统中,集热器作为光热转化的核心部件通过光谱选择性吸收涂层将太阳能转化为热能。因此,对选择性吸收涂层进行优化能够有效提高集热器的工作效率。选择性吸收涂层的主要吸收机理为本征吸收和干涉吸收,提升涂层吸收效率的策略有材料掺杂、等离激元、光学陷阱等。在集热器实际工作过程中,选择性吸收涂层的失效是影响其效率的主要因素,明确失效原因和寻找解决方案是进一步研究选择性吸收涂层的重点。综述了太阳能选择性吸收涂层的种类及原理,梳理了涂层的失效机制,总结了抑制涂层失效的方法。

光谱选择性太阳能吸收涂层的研究进展

选择性吸收涂层技术是公认的太阳能光热转换较为核心的技术,它对提高太阳能热转换效率,大规模推广太阳能光热应用起着至关重要的作用。主要综述了光谱选择性太阳能吸收涂层的分类及制备方法。

中高温太阳光谱选择性吸收涂层的研究进展

近年来,中高温太阳光谱选择性吸收涂层(以下简称为中高温吸收涂层)的研制及其在工业上的应用成为人们日益关注的焦点。本文在分类总结中高温吸收涂层的基本类型、作用机理和制备方法的同时,介绍了国内外不少科研工作者的研究工作和最新成果,并对中高温吸收涂层的制备方法优缺点及其发展方向进行了探讨。

真空管式太阳能集热器研究最新进展

从选择性吸收涂层的材料、结构、热稳定性及真空环境等方面综述了真空管式太阳能集热器的研究进展。不锈钢、Ti、Al、Ni类材料适于制备中低温选择性吸收涂层;而Mo和W类等高熔点材料,适于高温涂层。涂层结构方面,主要有吸收层/介质减反层的光干涉类、金属红外反射层/金属介质吸收层/介质减反层的金属陶瓷类。影响涂层热稳定性的主要因素是高温下涂层的破裂、氧化及元素扩散,涂层厚度与结构也能影响热稳定性。结果表明:①选择性吸收涂层制备,应采用电化学或磁控溅射技术并结合纳米材料对涂层进行多层化、梯度化研究;②应着重发展Mo类金属陶瓷型的热稳定性好的涂层,以实现高温高效集热;③应加快实现太阳能集热器的智能化、自动化与建筑一体化。

太阳能吸热涂层的研究现状

综述了 我国近 年来太阳 能吸热 涂层的研 究现状， 包括非选 择性涂层 和选择 性涂层两 大类，其 中选择性涂层 又可分为 电镀涂层 、阳极化 涂层、真 空镀膜涂 层和选 择性涂料

太阳能光谱选择性吸收涂层研究进展

太阳能是一种永不枯竭的清洁能源,目前,实现太阳能直接利用的方式主要是光-热转化技术。光谱选择性吸收涂层是光-热利用技术的核心。从光谱选择性吸收涂层的选择性吸收机理出发,阐述了涂层选择性吸收的理论依据。根据相应的理论,详细阐述了光谱选择性吸收涂层的结构。同时,综述了国内外光谱选择性吸收涂层的制备方法以及相关的研究进展。

两种太阳能选择性吸收涂层的综合评价

将全生命周期评价的基本方法和传热模型相结合,以市场上较为普遍的两种分别使用电镀法和物理气相沉积法(PVD)制作的太阳能选择性涂层为例,综合分析不同情景下使用这两种涂层的太阳能集热器的热利用效率、环境成本和综合能源价格。结果表明:物理沉积法所制涂层虽然制备成本较高,但生产过程对环境友好,同时该涂层在多种情景下的适用面相对更广,具有更好的经济性。

Ni-Mo太阳光谱选择性吸收涂层的制备与性能研究

以自制Ni-Mo团聚型复合粉末为喷涂原料,采用超音速火焰喷涂法制得Ni-Mo太阳光谱选择性吸收涂层,表征了复合粉末和涂层的表面形貌,涂层的组成元素、相组成和光学性能,研究了粉末粒径大小、涂层组分比例和表面处理对涂层选择性吸收性能的影响。结果表明:当所用复合粉末粒径r≤45μm,粉末中Ni,Mo质量比为7∶3时,制备的涂层选择性吸收性能较好,涂层由Ni,Mo和NiO三相组成,其表面为微不平漫射表面;将该涂层研磨处理至其表面粗糙度Ra为2.156μm时,涂层选择性吸收性能较佳,吸收率α为0.84,发射率ε为0.16;再在表面加镀减反层后,α增加至0.92,大幅提高了太阳光利用率。

中温太阳光谱选择性吸收CuO涂层的研制

为了获得性能良好的高纯度中温太阳光谱选择性CuO涂层,利用NaC lO作为氧化剂,在预处理过的黄铜片上研究CuO涂层的制备.考察了碱的用量、NaC lO摩尔浓度、反应温度和反应时间等对CuO涂层太阳吸收率α的影响,得到了制备CuO涂层的优化条件,并对CuO涂层表面进行了XPS及SEM表征;在CuO涂层上涂敷TiO2作为保护层,以延长CuO涂层的寿命.实验结果证明,在不明显影响吸收率的情况下,TiO2/CuO涂层的耐热性能、耐腐蚀性和耐磨性能比单纯CuO涂层有明显提高,从而达到既降低发射率,又延长涂层寿命的目的.

太阳能选择性吸收薄膜研究进展及展望

太阳能选择性吸收薄膜是太阳能集热器的主要功能组件,是太阳能光热转换中最为关键的部分,也是获得高光热转换效率的重要方式。本文从太阳能选择性吸收薄膜的原理出发,对材料选择、吸收机理以及制备方法等方面进行了介绍,对太阳能选择性吸收薄膜的国内外发展现状进行了论述,同时对限制太阳能选择性吸收薄膜性能的主要因素进行了分析,并对今后的发展进行了展望。