RE: bbc news19 Dec 2019 21:13
Not sure if this extract explains the power ratios ..."Liquid ammonia contains 1.7 times as much hydrogen as liquid hydrogen itself [206] … an ammonia tank (1?MPa) contains 2.5 times as much energy as a hydrogen tank (at 70?MPa) by volume, i.e. a hydrogen tank of 770?L (350?kg) could be replaced by an ammonia tank of 315?L (172?kg) ".
Valera-Medina et al, Ammonia for power, November 2018