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Comment by supernova87a | Hacker News Reader

I am no expert in hydrogen fuel cells and am interested to know. Do fuel cells deliver enough instantaneous power that batteries do, for the weight of all the associated equipment? Certainly the power density of the fuel is high, but given all the membranes, plates, etc. (all the "bubbling chemistry that has to happen"), how is the power delivery per hardware weight? Sometimes I imagine that exploding hydrogen in an engine (if it were possible) would be more power dense than sending it through fuel cells.

(as I said I'm clearly no expert about fuel cells)

And separate minor point, while it's pointed out as a novelty, I somehow doubt the composite construction is really targeted at anti-corrosion (I mean it might contribute a little on this front I guess). Corrosion issues in seaplanes are well understood for 50+ years, right? It's for the weight savings mostly.

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> Do fuel cells deliver enough instantaneous power that batteries do, for the weight of all the associated equipment?

I don't know about planes, but fuel cell cars have batteries, although smaller ones that EVs, which are actually used for the motors. HFC cars are basically EVs plus the hydrogen system.

Almost all flying boats (seaplanes which have a fuselage for a hull instead of floating landing gear) in the past 50 years have been built with fiberglass hulls for this exact reason. Aluminum has a durability problem more than a corrosion problem, and steel has a weight problem and a major corrosion problem. At the speeds that they hit the water, anti-corrosion coatings don't last long, and with a non-amphibious flying boat, repainting requires a haulout, which is very expensive.

> and steel has a weight problem and a major corrosion problem

if i want a salt water low tech floating shed (not mission critical), can you make it work with galvanized/re-painting schedule? or is marine grade steel a must ? (man, its expensive... )

Galvanized steel has almost no protection against continuous contact with salt water. There aren't even any stainless steels that I know of that can handle it well (just varying levels of resistance). I would say if you absolutely need a metal, you'd need marine grade stainless as well as a strong protective coating that you need to repaint on a regular basis, or possibly aluminum (as long as it's not going to have impacts or stresses that could bend it repeatedly).

If it were me, and it really is low tech and not mission critical, I'd probably use wood, fiberglass, or PVC.

Without having specific numbers in front of me, yes fuel cells are delivering comparable power as batteries. Plus the hydrogen is lighter than batteries.

Combusting may save on some of the complexity fuel cells but you are losing efficiency in heat losses, both from the act of combusting and with gears that deliver the power to your wheels or propeller.

They can produce the same levels of continuous power, but their spin up (think throttle response) is drastically slower. FC Cars definitely need a battery or supercapacitor to handle instantaneous power needs.

For planes and ships, that responsiveness is not needed.

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