Research On Properties Of Thermochemical Heat Storage Materials Based On Strontium Chloride

The seasonal thermochemical heat storage,utilizing salt hydrates as heat storage materials,has the advantages of large heat storage density,no heat loss and no pollution during the charging and discharging process.It effectively copes with the mismatch of solar energy supply and demand in time and has bright prospects in the field of space heating.In this paper,composite heat storage materials were prepared by impregnating the strontium chloride in the matrix of expanded vermiculite and the related properties were characterized and investigated.Electron microscopy and energy dispersive spectroscopy were used to characterize the microstructure and analyze the elemental composition.The results reveal that a large amount of salts accumulate on the surface of VM-Sr30,which seriously damaged the original porous structure of the expanded vermiculite.In order to avoid the deliquescence of salt hydrates,the deliquescence relative humidity of strontium chloride was tested by constant temperature and humidity chamber.The results show that the strontium chloride has high deliquescent relative humidity in the common temperature range,which is beneficial to the adsorption ability and material storage.The adsorption performance of the heat storage material was tested in the constant temperature and humidity chamber and the influence of temperature and humidity on the adsorption performance was also investigated.Among the four composite materials,VM-Sr25 has the largest equilibrium adsorption capacity under different humidity,which reaches as high as 0.296 g/g in the temperature of 15? and 70%RH.VM-Sr25 also exhibits a faster reaction rate during the adsorption process.The VM-Sr30 fails to exhibit the adsorption performance superior to VM-Sr25 due to the blocking effect,which hinders the transmission of water vapor in vermiculite pores.Therefore,VM-Sr25 is the best heat storage material among the four composite materials.According to the STA test results,the complete desorption temperature of SrCl2·6H2O was 139?,and the heat storage density of VM-Sr25 is 708.3 J/g after complete adsorption in the humidity of 70%.Finally,a continuous charge and discharge experiment was carried out in the reactor based on VM-Sr25 composite heat storage material,and the maximum temperature rise of 12.9 ? is observed during the heat releasing process.