Prius.

Nissan 200SX S14 (94-98) 60L plastic fuel tank and its bash plate weigh

20Kg. 60L fuel about 50Kg. Total weight full 70Kg. Fuel empty warning light on weight 25-29Kg.

H2 tanks on Mirai are different sizes, one under the back seat is longer with smaller diameter and 2nd shorter but larger diameter between back axles. It would need additional protection from handling damage. That may not add a lot of weight but would add bulk. That would make all H2 cars an SUV only option as the rear seats would be about 100mm higher. An utterly useless SUV as there is a stack of batteries behind the back seats on top of the 2nd H2 tank that prevent it having a useful flat floor. As getting the tank from under the back seat out requires the back seat to be removed it would be at risk of wear and tear (literally) at every tank swap. You wouldn't want to be doing this on an open forecourt as will have to decant all your passengers and rear interior out into the rain and snow.

Every tank swap station would need to be equipped with whatever system the factory use to purge the air from the pipe work. You may be waiting some time while they recommission your fuel system.

Owners are not qualified to swap tanks. I estimate about £250 for labor on every tank swap - it will be franchise dealer only service. The service dept only opens 9am-5pm and 1pm Saturdays. If you are out of fuel and need your tank swapping any other time then you sit and wait for them to open and then they book in for NEXT WEEK.

Just using that as an illustration. When I went into the nuclear industry in 1970, it was largely on the basis that oil would run out in the 1980's, and that thereafter we would all have electric cars which would be most conveniently charged overnight. And flattening the demand curve is ideal for nuclear. I still reckon batteries will dominate the car market for a while. I can see hydrogen coming first for HGVs, buses, and urban delivery vehicles (white vans).

[snip]

That was me. I did't see that pumping liquid hydrogen from the filling station into the car would be practical. But an exchangeable tank might be practical, and certainly easier to swap than a large battery.

It would of course require a standard tank and a standard coupling in the car. The swap could be mechanised.

It does require some thought, and development. But then, so did our current petrol & diesel distribution scheme.

It's not only practical, there's a filling station (not) near you!

Building and supplying the filling stations is slightly trickier...

Theo