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To address the inherent intermittency and instability of renewable energy, the construction of large-scale energy storage facilities is imperative. Salt caverns are internationally recognized as excellent sites for large-scale energy storage. They have been widely used to store substances such as natural gas, oil, air, and hydrogen. With the global transition in energy structures and the increasing demand for renewable energy load balancing, there is broad market potential for the development of salt cavern energy storage technologies. There are three types of energy storage in salt caverns that can be coupled with renewable energy sources, namely, salt cavern compressed air energy storage (SCCAES), salt cavern hydrogen storage (SCHS), and salt cavern flow battery (SCFB). The innovation of this paper is to comprehensively review the current status and future development trends of these three energy storage methods. Firstly, the development status of these three energy storage methods, both domestically and internationally, is reviewed. Secondly, according to the characteristics of these three types of energy storage methods, some key technical challenges are proposed to be focused on. The key technical challenge for SCCAES is the need to further reduce the cost of the ground equipment; the key technical challenge for SCHS is to prevent the risk of hydrogen leakage; and the key technical challenge for SCFB is the need to further increase the concentration of the active substance in the huge salt cavern. Finally, some potential solutions are proposed based on these key technical challenges. This work is of great significance in accelerating the development of salt cavern energy storage technologies in coupled renewable energy. Full article

Salt cavern flow batteries (SCFBs) are an energy storage technology that utilize salt caverns to store electrolytes of flow batteries with a saturated NaCl solution as the supporting electrolyte. However, the geological characteristics of salt caverns differ significantly from above-ground storage tanks, leading to complex issues in storing electrolytes within salt caverns. Therefore, investigating and summarizing these issues is crucial for the advancement of SCFB technology. This paper’s innovation lies in its comprehensive review of the current state and development trends in SCFBs both domestically and internationally. First, the current development status of SCFB energy storage technology both domestically and internationally is summarized. Then, eight main issues are proposed from the perspectives of salt cavern geological characteristics (tightness, conductivity, ions, and temperature) and electrolyte properties (selection, permeability, corrosion, and concentration). Finally, a novel SCFB system is proposed to address the most critical issue, which is the low concentration and uneven distribution of active materials in the current SCFB system. The review in this paper not only comprehensively summarizes the development status of SCFBs both domestically and internationally, but also points out the direction for the future research focussing on SCFBs. Full article