None of this makes hydrogen a bad idea at sea. It makes it a bad idea on this boat, for now. Go underwater and the arithmetic flips completely, because a
www.autonocion.com
Why fossil fuels continue to triumph: Energy density
Eighteen days on hydrogen, fifty on diesel
"Same hull. Same propellers. Different box in the middle. The reason comes down to one comparison, and it is not close.
"ACUA’s published Pioneer-class specification, laid out in detail by Uncrewed Systems Technology, puts endurance at 18 days on hydrogen and 50 days on diesel, both at an average 4 knots. That is the same boat doing the same job at the same speed, with the fuel as the only variable.
"The fuel cell is not the weak link. Pioneer runs a bespoke 45 kW unit from Nuvera that hits 58% thermal efficiency, against the 50 to 52% ACUA says most fuel cells manage. The problem is what you can physically carry.
"Hydrogen goes aboard as compressed gas in a modular frame that holds up to nine cylinders at 350 bar, roughly 10 kg apiece. Diesel goes aboard as about 4,000 litres of liquid that needs no pressure vessel at all, and buys around 5,000 nautical miles of range. Hydrogen wins per kilogram and loses badly per cubic foot, and a 46-foot boat is mostly cubic feet."