Research progress of CaCl2 composite thermochemical heat storage materials
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.
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