Hydrogen is an answer to the question, "how do you transport and store renewable energy in a post-carbon, post extraction world?"
It will power cars...but only way after it's become the norm in powering trucks, ships and planes. Debating its merits as a fuel is a bit like calculating the properties of wheat as a boiler fuel. Very accurate numbers can be computed but why bother?
Comparing H2's properties, advantages and penalties with extracted fuels is like mulling, "Which is best, propane or alternating current?"
The extraction world is subject to eventual depletion and unwanted co-products: dross, sludge, ash, slag, accumulated toxicity, climate CO2.
The renewables world has a new and still unfamiliar set of problems—rather like gasoline posed in 1905. We are not yet experienced in its safe use. But that's about us, not about hydrogen, and will change with time. H2 will always be the same. There is no agreed way to create and fund its production and transport. There will be by 2035 when France, South Korea, Scotland et. al. have no more rail diesel. Is it likely that no fuel cell trawlers will have appeared when all rail diesels are gone in smaller advanced countries?
Electrolyzers and fuel cells are like rectifiers and inverters. They transform energy for the next use in whatever process they're incorporated into. Hydrogen is a new "bungie-cord" electrical technology. Trying to reconcile its role as a mined fertilizer reagent (or as a fuel) with its energy transport function can be done but it fogs more than it clarifies.
H2 trawlers will require much less ubiquity than cars and, so, a much smaller H2 infrastructure. That's why they'll probably become usual long before H2 cars do...unless a new battery marvel dictates otherwise.
Search USDOE's "H2@Rail(SM)" Odd as it seems at first, for "paradigm shift" purposes, commuter trains are a better model for trawlers than cars are. The ICW is more like a track than like a city or a county.
