Abstract:

Hydrated salt thermochemical heat storage technology has the advantages of high heat storage density and low long-term storage heat loss, which is expected to solve the problem of imbalance between solar energy supply and energy demand. CaCl₂ has the advantages of fast hydration reaction kinetics, high heat storage density, low cost and a wide range of raw materials. However, pure hydrated salts have problems such as expansion and agglomeration, low thermal conductivity and poor stability. At present, researchers mainly improve the stability of hydrated salts by uniformly dispersing the hydrated salts through the porous matrix loading with high thermal conductivity, and increase the gas diffusion channels and accelerate the reaction rate through micro and nanopores. Therefore, in this paper, the main influencing factors of the performance of CaCl₂ composite thermochemical heat storage materials were analyzed from three aspects: the analysis of the storage/release mechanism, the performance index and the regulation of the physical properties of the composites. It was found that the pore characteristics and salt load of porous matrix were the main influencing factors affecting the heat storage density of composites, and the porous matrix of mesoporous structure was more suitable as a carrier for thermochemical reactions of hydrated salts. At the same time, the addition of magnesium-based salts to form binary salt composites was another effective method to control the physical properties, in which MgCl₂ can effectively improve the cycling stability of CaCl₂ and maintain good performance after 50 cycle tests. Finally, important technical directions for future research were pointed out, such as developing porous matrix with mesoporous structures including improvement of the aperture and stability of porous matrix, exploring new binary salt composite materials and matching thermal storage systems with thermal storage materials.

Key words: thermochemical heat storage, calcium chloride, composites, porous matrix, heat storage performance

摘要：

水合盐热化学储热技术具有储热密度高、长期储存热损失小等优点，有望解决太阳能供给与能源需求间不平衡的问题。CaCl₂具有快速水合反应动力学、高储热密度、低成本、原料广泛的优势。然而，纯水合盐存在膨胀结块、热导率低、稳定性差等问题。目前，研究者主要通过高热导率的多孔基质担载使水合盐均匀分散，实现稳定性的提升，并通过微纳米孔增加气体扩散通道，加快反应速率。本文分析了CaCl₂复合热化学储热材料性能的主要影响因素，分别从储/放热机理分析、性能评价指标、复合材料物性的调控三方面展开。研究发现，多孔基质的孔隙特性、CaCl₂的担载量是影响复合材料储热密度的主要影响因素，介孔结构的多孔基质更适宜作为水合盐热化学反应的载体。同时，加入镁基盐类形成二元盐复合材料是另一种有效的物性调控方法，其中，MgCl₂能有效提高CaCl₂的循环稳定性，在50次循环测试后仍保持良好性能。最后，指出了未来研究的重要技术方向，即开发以介孔结构为主的多孔基质，包括提高多孔基质的孔道开放度和稳定性、探索构建新的二元盐复合材料以及储热系统与储热材料的匹配等。

关键词: 热化学储热, 氯化钙, 复合材料, 多孔基质, 储热性能