盐湖水合盐/孔道矿物复合定形相变材料的制备与储能机理研究

The project involves preparation of efficient and stabilized phase change materials for thermal energy storage via impregnating inorganic hydrous salt including abundant K, Mg and Na element in salt lake to porous mineral to solve the long-term application problems such as supercooling and phase separation. The PSC and BET model are available to predict thermodynamics properties of inorganic salt hydrate. The phase diagram of polynary inorganic salt hydrate system is studied to select phase change media of suitable phase change temperature and high enthalpy. According to the structure layer and ion characteristic of expanded vermiculite, composite phase change material of low supercooling and high thermal stability is obtained via adding nucleating agent and thickener using surface modification technology. The combination and distribution between inorganic hydrous salt and ion in layer and functional group will be studied, which reveals mechanism control of effectively decreasing supercooling and phase separation in tiny space of porous mineral. Furthermore, the gypsum board and new composite phase change function materials was prepared to applied to building envelope system and decoration, and the energy saving effect is evaluated. The research is expected to provide the technical support for large-scale application of hydrous salt in salt lake in low-cost and high efficient building materials and present a new approach for higher-value utilization.

针对青海盐湖无机盐资源特点和目前水合盐相变储能材料实际应用中存在的过冷和相分离问题，利用孔道矿物为基体，以盐湖中富含钾、镁、钠元素的水合盐为相变储能介质，加工成稳定的复合相变储能材料。采用PSC和BET模型对盐湖无机水合盐进行热力学性质计算和预测，绘制多元无机水合盐体系相图，筛选出适宜相变温度和高焓值的无机水合盐体系。利用膨胀蛭可交换的特征，通过层内修饰和改性，添加成核剂和增稠剂，封装水合盐储能介质，形成过冷度小、热稳定性高的复合定形相变材料。通过研究无机水合盐与矿物层间离子相互结合状态以及水合盐在矿物层间的分布，揭示多孔矿物局域微空间中无机水合盐过冷度和相分离有效调控机制。将相变储能颗粒与石膏、镁水泥结合，制成相变储能石膏板和新型相变复合功能材料，用于建筑围护和装饰，并对其节能效果进行评价。研究成果有望为盐湖水合盐在建筑储能节能领域实现规模化应用提供技术支撑，为其低成本利用提供新途径。

盐湖中蕴藏有丰富的水合盐资源，其中部分水合盐具有储能密度大、相变温度适宜、廉价易得及过程易控制等优点，是获取相变储能原料的理想来源。盐湖水合盐的研究、开发和利用具有重要的经济价值和社会意义，然而，过冷度高、导热率低及相分离等问题制约了水合盐作为相变材料进一步应用与推广。本项目以青海盐湖水合盐相变储能介质为研究对象，以解决过冷和相分离等关键问题为主线，完成了水合盐储能介质体系的筛选、孔道矿物封装、储能材料的热物性能测试及应用领域探索等研究。取得的主要成果有：（1）开展了盐湖水合盐体系热力学性质预测及相图研究。通过热力学计算与实验研究从无机水合盐体系中筛选出CaCl2·6H2O、Na2SO4·10H2O、Na2HPO4·12H2O和CH3COONa·3H2O等具有良好储能效率和合适相变温度的储能介质；（2）深入开展了水合盐/孔道矿物复合定形相变储能材料的过冷和相分离抑制机理研究。采用增稠剂和成核剂分别改善水合盐的相分离和过冷抑制现象，获得了较低过冷度（≤1.4 ℃）的复合相变储能材料及其制备技术，并从晶体成核微观角度阐明了其在局域微空间中过冷抑制及调控机理。（3）系统开展了水合盐/孔道矿物复合定形相变储能材料的储热性能和稳定性研究，并进行了导热增强技术及机理探究。获得了较理想的相变温度、潜热和导热系数等重要参数，揭示了水合盐储能介质在多孔矿物表面及孔道内的相转变机理。（4）探讨了复合定形相变储能新材料用于建筑围护和装饰结构的可行性。采用复合相变储能颗粒与石膏料浆或镁水泥耦合制备了建筑储能新材料，探究了其作为墙体材料和新型储能石膏板的储热性能及可靠性。项目成果为解决水合盐相变材料的过冷及相分离提供了新的理论和技术，为无机水合盐相变材料的高效利用和盐湖资源的开发提供了参考价值。