Gigawatt-hour to terawatt-hour salt cavern supercapacitors and supercapatteries.

The advancement of energy technology has led to a notable increase in the contribution from renewable energy sources to the global energy supply and consumption landscape. Nevertheless, although inexhaustible and clean, the intermittency and instability of these energy sources present significant challenges to their wider deployment, necessitating the development of robust energy storage systems. Also, it is historical that the demand for power supply also varies significantly between day and night, and between different time zones, requesting large scale storage capacity for not only load levelling but also power supply security. In this article, salt caverns, which offer a sealable and unmatched large space and are currently employed for storage of compressed energy gases, are proposed for construction of giga- to tera-watt-hour scale supercapacitors and supercapatteries as an effective storage solution to renewable energy farms and national and international power grids. Following an introduction to salt caverns and their uses for storage of compressed air, natural gas, hydrogen and carbon dioxide, the potential is explored for construction of supercapacitors and supercapatteries in salt caverns. The discussion is specially focused on aqueous electrolytes that can be formed by utilising the salty water or brine from the construction of the salt cavern, and the respective electrode materials suitable for such aqueous electrolytes. Furthermore, calculations and analyses are given on the prospects of construction and application of giga- to tera-watt-hour supercapacitors and supercapatteries in salt caverns. Last, but not least, foreseeable challenges of such unprecedented ultra-large scale electrochemical energy storage devices are discussed with possible solutions.