Ammonia is simply nonsense. It's not going to happen for a variety of reasons. Liquid hydrogen is an even bigger nonsense.
Realistic fuels that are being used now: 1. Methanol. 2. Liquid methane.
Realistic fuels that are being used now: 1. Methanol. 2. Liquid methane.
One could get (much) higher efficiency by using the heat from a nuclear power plant directly (never producing electricity) but I guess that would have to be a completely custom design.
If you have spare electricity (from any source), it's easy. Just capture some CO2 and react it with hydrogen with specific catalysts and at a high pressure. You can get methanol directly this way.
It's more expensive than fossil fuels at the current prices, so nobody cares.
Liquid methane is essentially the same as LNG, which is rapidly becoming the most popular fuel for newbuild ships today. But it's about as environmentally friendly as building natural gas powerplant to replace coal - a temporary solution at best.
Future solutions need a carbon-free fuel, period.
Methanol is slightly preferred because methane can leak, and it's a more potent greenhouse gas than CO2. However, even most of the CH4 leaks happen near the drilling wells, and in pipelines. It's unlikely that synthetic CH4 will have to be transported over long distances.
https://gcaptain.com/aet-orders-worlds-first-ammonia-dual-fu...
Ammonia fueling infrastructure does not exist, and its failure scenarios are just not going to be acceptable. Meanwhile, LNG fueling infrastructure is rapidly getting built out.
What's worse, ammonia is also produced from natural gas, it's used for process heat and as a hydrogen source. There's pretty much no "green ammonia". So instead of round-tripping through ammonia production, it's easier to just burn the LNG directly.
In future, we can switch to green ammonia, but then we also can use power-to-gas or power-to-methanol instead. Both are more efficient than ammonia synthesis.
Methanol production, in particular, can potentially scale down to very small facilities. In theory, large utility-scale solar or wind farms can have a methanol synthesizer unit, that will produce it when there's more electricity when needed. It can then be transported by regular tanker trucks.