离子液体的相变储能利用

相变储能技术因其相变潜热大、蓄热和放能过程温度和热流基本恒定等优点成为能源科学技术中的重要分支.本文首先探讨了传统有机与无机相变储能材料存在的过冷、相分离、储能密度低、腐蚀性强等不足的原因,进而对离子液体相变储能材料的研究现状进行了分析.讨论了离子液体相变材料在太阳能储热、建筑节能、工业废热回收以及军事热红外伪装等领域的应用研究进展.指出了设计新型高效的功能化离子液体对于提高相变材料储能密度的重要作用,揭示了离子液体相变潜热与分子间作用力的关系本质,在此基础上提出了从离子液体的分子体积、氢键能、取代基诱导效应、H-π作用以及阴离子电负性等方面的改性入手,进行离子液体相变储热功能强化的科学设计的基本策略,以期为相变材料的科学设计与制备提供新的思路.     

相变储能高分子纳米复合材料的研究进展

讲述了亚稳态及高分子亚稳材料的概念,并从亚稳态的观点出发探讨了相变的分类及机理,说明对高分子材料亚稳态的研究不仅有理论上的意义,更具有重要的实用价值。描述了相变储能材料的分类,以及不同类型相变储能材料的特性及发展概况。介绍了相变储能高分子纳米复合材料的制备方法,着重概括了纳米技术在高分子相变储能材料领域的应用及研究进展。相变储能技术对节能、环保有着重要的应用价值,已经成为新材料科学领域的热点之一。     

复合相变储能材料的制备及应用研究进展

系统概述了复合相变储能材料的制备方法及其研究进展。特别介绍了固-液复合相变储能材料的制备方法,如熔融浸渍混合法、溶胶-凝胶法、静电纺丝法、真空渗入法和超声波法等。并结合实例探讨了复合相变储能材料在太阳能利用、建筑节能和纺织行业等领域的应用,在此基础上对其研究方向进行了展望。     

用于电热转化、存储与利用的导电相变材料

电能和热能作为生活生产中最大的供应端和消耗端,二者间的转换、存储与利用在能源体系里占据了重要的一环。因此,研发高效率的电热转换-存储功能材料,在能源、环境和气候危机频现的今天,具有重要的意义。相变材料的储热密度高、相变时吸放热而温度不变,在热能存储中具备独特的优势。然而大多数相变材料的本征低电导率与当下储能系统的功率要求不匹配,通过与导电材料结合得到电热转化的相变复合材料可以有效地改变这种情况。本文对电热转换相变材料最新研究进展进行了综述,从电热转换相变材料的功能机制、影响因素和应用三个方面,对添加导电填料、负载导电骨架或导电高分子聚合的复合相变材料进行了综述与比较。最终对此领域未来的研究方向和重点进行了展望。     

水合盐相变储能材料的研究进展

无机水合盐相变储能材料具有相变潜热大、相变温度适中、价格低廉等优点,在太阳能高效利用、跨季节储热采暖、工业余废热利用、轻纺行业等方面具有广阔的应用前景。但过冷、相分离、导热系数低等问题限制了其实际应用。本文介绍了水合盐相变储能材料近年来的研究进展,分析了水合盐相变存在的过冷及相分离现象的原因。通过成核剂法、多孔基体吸附法、微胶囊法等方法可以降低其过冷度;通过增稠剂法、晶形改变剂法等方法可以改善其相分离问题;通过与高导热性的纳米粒子、多孔的高导热基体相复合,可以提高其导热性能。最后,指出了今后水合盐相变储能材料的重点研究方向,可以从与计算化学相结合、寻找合适的无机壳材料以及探究共晶体系等方面继续深入研究。     

纳米胶囊相变材料研究进展

纳米胶囊相变材料是一类新型储能材料.本文介绍了纳米胶囊相变材料的研究背景、发展历程和优势;分析了相变储能纳米胶囊的结构、原理及其功能,包括囊芯与囊壁的种类及选材原则,微胶囊与纳米胶囊性质比较;重点介绍了细乳液聚合、原位聚合和界面聚合等纳米胶囊制备方法的原理及研究进展,并对相变储能纳米胶囊在建筑节能、功能热流体、服装、航空航天及军事等领域的应用作了总结.     

聚乙二醇/二醋酸纤维素相变材料的组成与储能性能间的关系

以刚性的二醋酸纤维素 (CDA)链为骨架 ,接枝上聚乙二醇 (PEG)柔性链段 ,可得到一种具有固固相变性能的网状储能材料 .利用该材料的PEG支链从结晶态到无定形态间的相转变 ,可以实现储能和释能的目的 .具体研究了PEG的百分含量及PEG的分子量对材料储能性能的影响 .研究结果表明 ,通过改变PEG的百分含量与PEG的分子量 ,可以得到不同相变焓和不同相变温度的材料     

高结构稳定性、低泄漏率三维铜@石墨烯复合相变材料的制备

由于能源消费需求的持续增长和传统化学燃料的日益枯竭,对可再生能源的需求日益迫切。以地热能、太阳能为代表的可再生能源脱颖而出。然而,这些能源的应用易受到天气、季节、地点和时间的影响,具有不稳定性、随机性、波动性和间歇性。储能技术是解决上述问题的有效途径,它可以在需要的时候储存或释放能量。在各种储能技术可选材料中,相变材料(PCMs)是智能热能管理和便携式热能领域的有力候选者。大多数相变材料都存在导热系数低、环境污染、熔点泄漏等问题,因此有必要将相变材料封装到支撑骨架材料中。事实上,支撑材料在应用中仍面临着一些重大挑战。首先,骨架材料应能抵抗相变材料在相变过程中的体积变化,即具有良好的结构稳定性。其次,还应具有较高的导热系数和较低的泄漏率。石墨烯气凝胶(GA)已被证明是提高相变材料形状稳定性的有效支撑骨架,但相变引起的泄漏和网络结构的脆性是制约其应用的关键问题。在此,我们提出了一种双脉冲电镀的强化策略,用于制备铜@石墨烯气凝胶(Cu@GA)作为相变储能骨架材料。这一结构设计中,石墨烯气凝胶上的石墨烯片层上均匀地镀上了铜层,且不同片之间被铜镀层所连接。这种铜增强石墨烯气凝胶网络结构赋予复合材料良好的导热性和坚固的骨架稳定性,有利于增强相变换热和抑制相变过程中的泄漏。此外,通过真空浸渍法将十八胺(ODA)封装在Cu@GA骨架中,获得了结构稳定性高、泄漏率低的复合相变材料(Cu@GA/ODA),保证了ODA在Cu@GA骨架材料中的均匀分散和填充。通过比较复合相变材料的重量变化,研究了不同骨架对复合相变材料泄漏率的影响。优化后的复合相变材料(CPCM)Cu@GA/ODA经20次储热、放热循环后,泄漏率降低至19.82% (w,质量分数),而GA/ODA和GOA/ODA为骨架的复合相变材料的泄漏率分别为80.31% (w)和72.99% (w)。为了探讨这种影响的原因,用扫描电子显微镜(SEM)观察了循环后骨架的形貌。铜/石墨烯气凝胶(Cu@GA)骨架材料没有明显的收缩或坍塌,仍可以保持完整的三维网络结构,而氧化石墨烯气凝胶(GOA)和石墨烯气凝胶(GA)的骨架材料三维结构不复存在,且在氧化石墨烯/石墨烯片能够观察到明显的裂隙。铜涂层可以提高骨架的微观结构稳定性,有利于提高结构稳定性,降低复合材料的泄漏率。同时,该研究为构建理想的金属增强石墨烯气凝胶复合骨架材料铺平了新的道路,该复合材料具有优异的综合性能,可用于未来的相变储能、多孔微波吸收和储能应用。     

相变储能材料的研究进展

综述了相变材料的研究进展状况 ,介绍了相变材料的分类以及各类相变材料的性能、储能机理和优缺点 ,并介绍了一些新型的相变材料 ,指出了该领域中有待解决的问题 ,展望了未来相变材料的发展前景。     

石蜡相变微胶囊的制备与表征

采用复乳交联法制备了以相变石蜡为芯材、壳聚糖为壁材的新型储能相变微胶囊。 此相变微胶囊具有很高的相变焓值（可达110 J/g以上）,并且可以根据具体需要改变芯材的温度;TGA研究表明,该相变微胶囊具有很好的热稳定性,在150 ℃以下可以稳定存在;由于壳材料进行了化学交联反应,使得该相变微胶囊具有很好溶剂稳定性,可以在水、乙醇和乙醚等常见溶剂中稳定存在。     

相变蓄热材料研究进展

相变蓄热材料(恒温潜热热能储存材料)是目前最热门的功能材料之一。它在发生相变时储存、放出的热量能够帮助所在系统进行能量的储存,同时可以一定程度上缓解双方在时间、强度及地点上的不匹配程度。相变蓄热材料优点突出,其中包括在使用过程中自身温度变化较小、有很好的稳定性、储热能力较强等。此类材料对环境友好,响应了国家近年来节能环保的政策,同时也可以极大地优化所在系统的运行效率。本文综述了近年来几类相变蓄热材料的种类、特点及国内外学者应对于不同缺陷做出的改进及其应用于行业的研究现状,并对未来的发展进行了探讨与展望。     

Application of PCM thermal energy storage system to reduce building energy consumption

The building sector is known to make a large contribution to total energy consumption and CO₂ emissions. Phase change materials (PCMs) have been considered for thermal energy storage (TES) in buildings. They can balance out the discrepancies between energy demand and energy supply, which are temporally out of phase. However, traditional PCMs need special latent storage devices or containers to encapsulate the PCM, in order to store and release the latent heat of the PCM. The proper design of TES systems using a PCM requires quantitative information and knowledge about the heat transfer and phase change processes in the PCM. In Korea, radiant floor heating systems, which have traditionally been used in residential buildings, consume approximately 55% of the total residential building energy consumption in heating. This article reviews the development of available latent heat thermal energy storage technologies and discusses PCM application methods for residential building using radiant floor heating systems with the goal of reducing energy consumption.     

High-conductivity nanomaterials for enhancing thermal performance of latent heat thermal energy storage systems

Journal of Thermal Analysis and Calorimetry - Dispersing high-conductivity nanomaterials into phase change materials (PCM) of latent heat thermal energy storage systems (LHTESS) is expected to...     

Development of a model for compensating the influence of temperature gradients within the sample on DSC-results on phase change materials

The use of phase change materials (PCMs) in thermal storage is not a new concept, but engineers are continually finding new ways to utilize them in a wide range of applications. A PCM takes advantage of high latent heat in the phase change process to store large amounts of heat while undergoing only a small change in temperature. This property makes PCMs suitable for thermal storage purposes in a wide range of engineering applications. Due to the nature of these applications, it is vital to have a precise knowledge of the thermal characteristics of any PCM. Unfortunately, due to the low thermal conductivities and high latent heats found in PCMs, current measuring tools such as differential scanning calorimetry, provide inconsistent results. This paper conjectures that these errors come from the effects of low thermal diffusivity samples as well as improper data analysis methods.     

Numerical simulation and parametric analysis of latent heat thermal energy storage system

This paper presents the numerical analysis of the transient performance of the latent heat thermal energy storage unit established on finite difference method. The storage unit consists of a shell and tube arrangement with phase change material (PCM) filled in the shell space and the heat transfer fluid (HTF) flowing in the inner tube. The heat exchange between the HTF, wall and PCM has been investigated by developing a 2-D fully implicit numerical model for the storage module and solving the complete module as a conjugate problem using enthalpy transforming method. A comparative investigation of the total melting time of the PCM has been performed based on natural convection in liquid PCM during the charging process. The novelty of this paper lies in the fact it includes convection in PCM and this investigation includes a detailed parametric study which can be used as a reference to design latent heat storage. The results indicate that natural convection accelerates the melting process by a significant amount of time. In order to optimize the design of the thermal storage unit, parametric study has been accompanied to analyze the influence of various HTF working conditions and geometric dimensions on the total melting time of the PCM. Another important feature considered in this work is the influence of the inner wall of the tube carrying the HTF on the entire melting time of the PCM. An error of around 7.2% is reported when inner wall of the tube is ignored in the analysis.

     

The investigation of thermal conductivity and energy storage properties of graphite/paraffin composites

Phase change materials (PCM) have been extensively scrutinized for their widely application in thermal energy storage (TES). Paraffin was considered to be one of the most prospective PCMs with perfect properties. However, lower thermal conductivity hinders the further application. In this letter, we experimentally investigate the thermal conductivity and energy storage of composites consisting of paraffin and micron-size graphite flakes (MSGFs). The results strongly suggested that the thermal conductivity enhances enormously with increasing the mass fraction of the MSGFs. The formation of heat flow network is the key factor for high thermal conductivity in this case. Meanwhile, compared to that of the thermal conductivity, the latent heat capacity, the melting temperature, and the freezing temperature of the composites present negligible change with increasing the concentration of the MSGFs. The paraffin-based composites have great potential for energy storage application with optimal fraction of the MSGFs.     

Latent heat nano composite building materials

Heat storage for heating and cooling of buildings reduces the conventional energy consumption with a direct impact on CO₂ emissions. The goal of this study was to find the physico-chemical fundamentals for tailoring phase change material (PCM)-epoxy composites as building materials depending on phase change temperature and latent heat using the optimal geometry for each application. Thus, some nano-composite materials were prepared by mixing a PCM with large latent heats with epoxy resin and Al powder. Some polyethylene glycols of different molecular weights (1000, 1500, and 2000) were used as PCMs. Subsequently these PCM-epoxy composites were thermo-physically characterized by DSC measurements and found to be suitable for building applications due to their large latent heat, appropriate phase change temperature and good performance stability. Moreover these cross-linked three dimensional structures are able to reduce the space and costs for encapsulation.     

Effect of phase change materials on the hydration reaction and kinetic of PCM-mortars

The phase change materials are considered an attractive way to reduce energy consumption thanks to their heat storage capacity. Their incorporation in the construction materials allows the energy to be an integral part of the building structure. Even though PCMs have shown their reliability from a thermal point of view, some drawbacks linked to their use were emphasized such as the loss of the compressive strength of the PCM-material. This paper attempts to provide an explanation by the investigation of the hydration kinetic of PCM-mortars. The semi-adiabatic Langavant test was adapted to this case. The numerical diffuse element method was used for the computation of the heat flux, which is a compulsory step for the determination of the hydration degree. The results showed a lower heat released by the PCM mortars compared to a control mortar as well as a delay in the hydration progress with the addition of PCMs.