In-situ measurement techniques for investigating the life cycle chemical and thermodynamical properties of molten salts and corrosion prevention for thermal energy storage

Supervisor

Subject

Prof. Dr. Dongsheng Wen Thermal Energy Storage, Concentrated Solar Power Plant, Thermal Conductivity Measurement

Editor

Cooperation/Funding

Zheng, Jun; M.Sc. This project is supported by the China Scholarship Council, whose support is gratefully acknowledged.

Background

The development of renewable energy sources and the optimization of energy storage technologies are hot topics of current research, which help to achieve sustainable economic and social development. Thermal energy storage (TES) is well suited for storing excess energy. Our research will focus on the sensible heat storage in which energy is stored in a medium by raising its temperature. When thermal energy storage is coupled with a concentrated solar power plant (CSP), the heat absorbed from solar by the thermal storage medium during daytime can also be used to generate electricity at night. In this way, the excess energy can be temporarily stored in the thermal storage medium first, avoiding the waste of energy on the one hand, and contributing to the stability of the electric grid on the other hand. The development of the next generation of concentrated solar power plants coupled to molten salt thermal storage systems relies on answering important fundamental questions about the chemical and thermodynamic properties of molten salts, as well as compatibility with advanced thermal storage tank designs and materials. In particular, there is interest in understanding the conditions for advanced thermal storage systems to achieve long life and safety goals.

Experimental Studies

The physicochemical properties of the molten salt are relevant to both the interpretation of the corrosion mechanism and the effect of alloy dissolution in heat storage tank. Therefore, development of new detection systems and corrosion prevention strategies are needed to enable continuous operation of molten salt thermal storage systems under optimal conditions. By monitoring the system in an elevated temperature environment, key challenges including the early detection of impurity ions in the molten salt, the chemical behavior of the salt, abnormal changes in viscosity, variations in thermal conductivity, etc. must be addressed.

 

(1) Experimental platform building, including the procurement, assembly, commissioning, and operation of basic experimental equipment and experimental raw materials.

(2) According to the corrosion mechanism, the experimental variables are controlled and group experiments are conducted to develop in-situ corrosion monitoring methods and early warning mechanisms for molten salt energy storage systems. Cyclic voltammetry (CV) will be used in our study to monitor the concentration of impurities such as chromate, oxide, nitrite, hydroxide, water in the solar salt in-situ. This is an electrochemical method in which a three-electrode system is inserted into a heated molten salt, voltage signals are applied, and corresponding current signals were generated through a potentiostat.

(3) High temperature molten salt viscosity measurement experiments, first design and develop new self made rheometer, according to the corrosion mechanism, then the molten salt viscosity under different working conditions will be measured transiently and analyzed in comparison with literature values.

 

(4) In-situ measurement of thermal conductivity of molten salt by transient method. It involves the design and installation of thermocouples, the development of measurement devices, the measurement of thermal conductivity at different temperatures, and the measurement of thermal conductivity before and after the occurrence of corrosion.

 

(5) All-in-one device design and application to optimize the efficiency and accuracy of experimental data acquisition and to obtain simultaneously several high temperature molten salt physicochemical and thermophysical properties.

Research goals

The main goal of our research is to better understand the chemical and thermodynamic properties of molten salt thermal storage fluids in whole life cycle. So that we can establish strategies to prevent corrosion. In this work, it is planned to develop a comprehensive and integrated method that can easily, efficiently and accurately detect key properties in heat storage fluids, analyze and characterize the physical, chemical and thermodynamic properties of fluids of various compositions under different operating conditions, which provides theoretical support and laboratory level validation for industrial energy storage applications.