Study On Long-term Thermochemical Thermal Storage Performance Based On SrBr₂-vermiculite Composite Materials

Strontium bromide hexahydrate(SrBr2·6H2O)is one of the most promising salt water complexes for space heating thermochemical energy storage.However,It is necessary to develop a new thermochemical energy storage composite material by adding it into porous matrix as a composite adsorbent due to its unstable morphology.Secondly,due to the lack of an accurate kinetic model of SrBr2·6H2O,the desorption reaction and exothermic rate cannot be well controlled.In this paper,SrBr2/expanded vermiculite composite(EVM)was prepared,and its structure and adsorption/desorption properties were studied.The adsorption/desorption kinetics of SrBr2·6H2O were established.Firstly,the structure of the composite was characterized by scanning electron microscopy(SEM)and energy dispersive X-ray analysis(EDS).The results showed that salt was evenly distributed in the pores of expanded vermiculite,and the surface of the composites with high salt content was more salt than other composite materials.Secondly,in order to explore the adsorption/desorption properties of the composite under different humidities,a number of adsorption experiments were carried out in the constant temperature and humidity chamber.The results showed that the highest adsorption capacity of the composite material was EVM/45%,reaching 0.55 g/g,and the deliquescence humidity was 70%RH,which was relatively high,which was conducive to the adsorption and storage of the materials.Meanwhile,the desorption properties of pure salt and composite materials were tested by Thermo Gravimetric Analysis(TGA)and differential scanning calorimetry(DSC),the results showed that the complete desorption temperature of SrBr2·6H2O was 193.3?,and the desorption mass energy density of composite materials was 692.9 J/g.In order to predict the adsorption/desorption behavior of composites under different conditions,the adsorption/desorption kinetic equations were obtained by fitting based on the experimental data.Finally,the adsorption/desorption properties of the composites in the reactor were tested based on the thermochemical thermal storage test-bed.The results showed that in the cycle experiment,the average maximum temperature rise of the adsorption process was stable at 20.1?,the average adsorption mass was 150.3 g,and the average desorption mass was 149.5 g.With the increase of the number of cycles,the temperature and the quality of the composite tend to be stable.