The off-grid energy and long-haul transport sectors, unregulated until the last decade, must be net zero by 2050. Battery technology is unsuitable due to cost and weight. Hydrogen technology is considered to be the only viable solution to decarbonising these sectors. Carnot power units will have greater efficiency, lower total cost of ownership and greater range, reliability and durability than fuel cells. They are the key to unlocking a hydrogen future while minimising the impact to supply chains.