There are alternatives. For example, in the UK there is a growing interest in the notion of cryogenic liquids. These are reported to be at a lower cost point and more likely to be suitable where solar energy can be used to drive compressors to compress air to liquid air (as cryogenic fluids). Liquid air is potentially an energy vector in itself and vaporisation of the liquid using low-grade waste heat makes for a very efficient system that then drives a generator. The round-trip efficiency of these systems rivals batteries.

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