Formulation Optimization Of Quaternary Mixed Molten Salt And Economic Analysis Of Thermal Storage System

Energy is the material basis for human survival and social development.As people continue to improve their material and spiritual lives,they are also continuously aware of the serious consequences of the large-scale use of fossil fuels:increasingly depleted resources and deteriorating global environment.The development of renewable energy has entered a period of prosperity because of the problems of pollution and energy crisis are becoming autumn acute.The development and utilization of new and renewable energy resources are of great strategic significance to the path of sustainable development and the protection of the Earth’s ecological environment on which humanity depends.Solar thermal power generation technology has brought in general attention at home and abroad due to its large scale,low unit cost,environmental friendliness,and has achieved rapid development,the problem of intermittent and unstable solar energy can be solved by combination with heat storage technology.In the heat storage system,the heat transfer and heat storage medium with excellent performance can not only improve the heat storage efficiency,but also reduce the investment and operating costs.Mixed molten salt stands out of many heat transfer and storage material due to wide temperature range,low vapor pressure,large heat capacity,low viscosity,and economical environmental protection.In this paper,11 kinds of new mixed molten salts were prepared by adding different proportions of additive Ca（NO₃）₂·4H₂O to Hitec salt.Preferably a mixed salt with a composition of 16.67wt%Ca（NO₃）₂·4H₂O+44.17wt%KNO₃+5.83wt%NaNO₃+33.33wt%NaNO₂ by Differential Scanning Calorimetry（DSC）and Thermo-Gravimetric（TG）analysis,which has a melting point of 84℃and a decomposition temperature of 628.5℃.The specific heat of the samples were measured by the specific heat comparison method and its sensible heat storage cost was calculated as 4.1$/（kW·h）,which is lower than the commonly used Solar salt and Hitec salt.The densities of the samples were measured by using the Archimedes principle.The thermal diffusivity of the samples were measured by using the Laser Flash Analysis（LFA）and calculate the thermal conductivity.Its thermal properties were analyzed to obtain the corresponding fitting calculation formula.An experimental study was carried out on the stability of the mixed molten salt at565℃for 1200h and 120 cycles for RT⁵00℃.The corrosivity of the preferred mixed molten salt was studied for 500 hours by using carbon steel,201,304,316L.The experimental results show that:in the two thermal stability experiments,the mixed molten salt exhibits good thermal stability,in the corrosive experiment,the mixed molten salt is preferred to have a strong corrosive effect on the carbon steel,but for the 201,304,316L The corrosiveness is weaker.