4. The French are so cute, they save weight by taking out the need for hydrides but needs weight and space in the complex hydrogen reforming and Shift reactor to make enable the conversion of water into hydrogen — it’s space packaging really help it to complete with the Swedish stirling AIP engine system — unless Singapore wants to cut the hulls of the Archer class again, the French are out of luck in trying to sell the system to a Swedish and German submarine user. In any submarine design, there are weigh, volume and other design limits — this system is not plug and play for a German or a Japanese submarine design.
I don't think many AIP solutions are plug and play, even if they are sometimes advertised that way, subs have tight margins, and everything needs to be matched. I would imagine the French are chasing new submarine builds. Indian, Malaysian, Brazilian and Indonesian subs, and any new customers.
The French solution is interesting, because it does remove a lot of "dead weight" in the hydride storage, also there is significant room for improvement, with hydrides there isn't a whole lot more you can do. Its also a bit more flexible as you can build subs with or without AIP fairly easily. Scaling up hydrogen storage has also been an issue with hydride storage. While the dead weight of the reformer is significant, its of a different type, can be integrated into the sub.
Not having hydrogen stored in the submarine is a great advantage. Hydrogen has a range of issues beyond explosive or oxygen displacement.
Oxygen is less problematic. While it can certainly be dangerous, its possible to handle it. Asphyxiant gases there are often no warning signs at all, you just pass out, hydrogen does have a neater habit of going up generally. Hypoxia due to altitude has very different symptoms to that of displacement, displacement you basically go to zero oxygen, and zero CO2 build up. While pure oxygen is toxic at high pressures, it is a nicer option than pure hydrogen. Also you are only storing one gas inside, not two. But again, diesel is really easy to store, refill etc. The key thing is fuel is outside, if you can get the reformer smaller enough it becomes a big win.
I don't think the Japanese are desperate to get in on this. I think the point they are making is that lithium and AIP are complimentary, they don't have to be exclusive. But as lithium gets better, it will make the less effective AIP redundant, generally.
Just playing around with numbers.
Eg 1.5 kg of oxygen per crew member per day, say 60 crew, say 10 day endurance, its about a ton of oxygen per 10 days, just in crew oxygen.
Say a container cylinder 4m x 5 so say 70 cubic metres, so say around 80 tons of liquid oxygen. Wow, crew usage is tiny. Say 18 day endurance, around 3.5t per day.
Say 70t of o2, system has to produce about 8.75 t of hydrogen. So the hydrogen reformer needs to weigh less than about 9 tons of stored Hydrogen. But as hydride, say 70kg per m3, thats around 125m3 of storage. So it needs to be smaller than that ballpark amount. All wild guesses and estimates.
The advantage of this system is put in a bigger liquid oxygen tank.
