OK, I have thought about this a bit (I have worked on gas liquefaction plant design), and I do not believe this claim. 70% is about the maximum thermodynamic e

OK, I have thought about this a bit (I have worked on gas liquefaction plant design), and I do not believe this claim. 70% is about the maximum thermodynamic efficiency of any heat engine operating between -190 degrees and ambient. And the best efficiency you can expect in liquefaction, in a very complex and large plant, is circa 50% (1). Combined with storage losses, I think the overall cycle efficiency cannot be more than 25% or so. Happy to review and comment on any back-up to their claim. (1) see eg here: https://search.informit.com.au/documentSummary;dn=893357213721903;res=IELENG https://search.informit.com.au/documentSummary;dn=8933572137...