WU Yuting, ZHANG Cancan, LU Yuanwei, SANG Lixia, CHEN Xia, DU Yanjun
Molten salt heat storage utilizes liquid salt to absorb heat as the temperature increases and release heat as the temperature decreases. The molten salt used for heat storage is generally a eutectic mixed salt formed by mixing two or more inorganic salts in a certain proportion, which has the advantages of wide liquid temperature range, large temperature difference, high heat storage density, and long service life. Molten salt thermal storage generally uses a dual tank liquid sensible heat storage scheme, which has the advantages of constant inlet and outlet parameters of the heat storage and release heat exchanger/electric heater, small temperature difference between hot fluid outlet and hot salt tank, and simple control. It has a wide range of application scenarios in the fields of solar thermal power generation, peak shaving system of coal-fired unit aided by molten salt heat storage, molten salt direct/heat pump thermal storage and power generation, molten salt thermal storage for heating and steam supply, compressed air energy storage and compressed heat storage, etc. It is a medium to long term energy storage technology with low-cost, large capacity and long-life. The key technologies and difficulties of molten salt thermal storage are the research and development of mixed molten salt and its composite thermal storage materials with low melting point, high decomposition temperature, low corrosion, low-cost and thermally stable, the research and development of large inlet and outlet temperature difference molten salt heat exchangers and high-voltage molten salt electric heaters, and the integrated regulation and optimization of a new energy system coupled with molten salt thermal storage. At present, more than 30 integrated large capacity thermal storage solar thermal power plants have been put into commercial operation worldwide (with a total installed capacity of over 3 million kilowatts). The longest molten salt thermal storage solar thermal power plant has been successfully operating for 18 years. In recent years, in China, Huaneng Weijiamao, Guoxin Jingjiang, Huaneng Haimen, Shandong Dezhou and other thermal power plants have successively built several molten salt thermal storage peak shaving demonstration projects. At the same time, several molten salt thermal storage heating and steam supply demonstration projects have also been built in Hebei, Beijing, Zhejiang and other places. The Liaohe Oilfield has built an electric molten salt energy storage injection test station. At present, Beijing University of Technology has successfully developed a series of low melting point, high decomposition temperature, wide liquid temperature range mixed molten salt optimization formulas with melting points between 100~160 ℃ and decomposition temperatures between 560~740 ℃, and has been widely used in molten salt heat transfer and storage engineering for a long time. Zhejiang Green Storage, Huayuan Frontline and other companies have successively developed high-voltage molten salt electric heaters.
