Solar Phase Change Energy Storage Heating Technology Based On Hydrated Salt Composite Materials

At present,some rural areas in northern my country cannot provide centralized heating in winter and can only use fossil fuels for decentralized heating.Distributed heating has the problem of low heating efficiency and environmental pollution.Solar energy is a kind of clean energy.Using solar energy to heat buildings can solve the dilemma of decentralized heating.Existing data show that solar heating mainly uses sensible heat storage,and the latent heat storage technology with better heating effect is still in the theoretical experimental stage.Many people have carried out research and need to deepen their focus on practical applications.Therefore,an efficient solar phase change energy storage unit can be built.Combine phase change latent heat energy storage materials with solar heating technology to meet the demand for decentralized heating in northern my country.The following researches are carried out around this content:(1)Preparation of hydrated salt composite phase change material:Sodium acetate trihydrate in hydrated salt is used as the main material of the energy storage unit.Aimed at the problem of supercooling and phase separation of hydrated salt materials.The mass ratio of 2.5%nucleating agent(disodium hydrogen phosphate dodecahydrate)and 2%thickener(sodium alginate)are used to suppress the supercooling and phase separation of the main material.The thermal stability and heat absorption and release cycle tests of the prepared composite material were carried out.The phase transition temperature of the composite material is 55℃.The reaction enthalpy dropped from the initial 269 k J/kg to 191.72 k J/kg after 100 cycles.The composite phase change material has good energy storage performance.(2)Design a modular cylindrical energy storage unit with a built-in spiral coil heat exchanger,and analyze the connection mode between the energy storage units.The energy storage simulation analysis of the energy storage unit shows that the charging process of the energy storage unit is divided into three stages:the initial sensible heat stage,the intermediate latent heat stage,and the final sensible heat stage.The energy storage unit is dominated by sensible heat in the initial stage of energy storage,and enters the mid-term latent heat stage after the temperature reaches the material phase transition temperature of 55℃.The temperature of the energy storage unit is maintained at 55℃until the phase change is completed.After that,the temperature of the energy storage unit continues to rise.Enter the final sensible heat energy storage stage,until the temperature of the energy storage unit rises to 70℃and the end of energy storage.The whole process lasted 330 minutes;the simulation results of the energy storage unit were compared with the energy storage of the laboratory energy storage unit,and the accuracy of the simulation simulation of the energy storage unit was obtained;the heat release simulation of the energy storage unit was performed.It is concluded that the energy storage unit containing 3 kg of composite phase-change energy storage materials can maintain the water temperature at the heating end of the same proportion above 30℃for 9 hours.The heat exchange efficiency of the energy storage device is 84.1%.The heat transfer effect and heat exchange efficiency of the energy storage unit are good.(3)Design a solar phase change energy storage heating system.The solar phase-change energy storage heating system is designed from the aspects of heat storage temperature and heat storage capacity:the temperature of the solar phase-change energy storage heating system is set to the phase change temperature of the composite energy storage material at 55℃,which meets the relevant national heating standards;The heat storage capacity design of the heat collector and energy storage materials is carried out,the heat collector is optimized,the best installation angle of the heat collector and the calculation method of the heat collector area are determined.Calculated with reference to the required unit heating load(55 W/m~2)of civil buildings,it is calculated that 8 kg of composite phase change energy storage materials meet the heating demand per square meter;the design and promotion of buildings in a certain area of Lintao,Gansu.The study of the local solar radiation intensity shows that the solar radiation intensity is basically above 200 W/m~2 during the heating season,which is higher than the unit heating index of residential houses(46.5-70 W/m~2).In the heating season,the radiation intensity in Lintao area is relatively abundant.It is calculated that the optimal installation angle of the collector is 50°,and the total area of the collector is 6.9 m~2;the heat storage capacity of the energy storage device is calculated with the required unit heating load of civil buildings,and 20 m~2 requires a composite phase change storage can material 160 kg.