The key feature of hydrogen as energy storage wouldn't necessarily be round trip efficiency but cost effectiveness (compared to batteries) of long-term storage over months.
Think about transporting peaks of renewables electricity generation that are not economically usable at the time when they're produced to times when renewables produce too little to meet demand. (Mostly in regions where generation depends significantly on seasons.)
Think about transporting peaks of renewables electricity generation that are not economically usable at the time when they're produced to times when renewables produce too little to meet demand. (Mostly in regions where generation depends significantly on seasons.)