Re: [PSUBS-MAILIST] Water-powered Sub...

[TeslaTony@aol.com]

In a message dated 4/4/02 3:45:24 PM Pacific Standard Time, sirius@riverstyx.com writes:


> Is anyone interested in a water-powered sub? All you have to do is hook
> either a fresh-water tank or an intake/desalinization line into a hydrogen
> generator ( http://www.eren.doe.gov/RE/hydrogen.html ,
> http://www.nature.com/nsu/011206/011206-11.html ), pump the output into a
> PEM Fuel cell ( http://www.ballard.com/portable_app.asp ), hook the
> batteries up, and you're ready to jam. Imagine being restricted in your sub
> dives only by the amount of food on board and the sanity of the crew! You
> could tap the freshly desalinated water for drinking and sanitation, and
> bleed off oxygen from the hydrogen generator for breathing. Hey, the Navy
> does it... Isn't it about time the technology became widespread? Of course,
> something like this would only be worth putting in a sub like CSSX because
> of the cost... Give it 5 years though... You'll see ;)
>
> - Jacob Lauser
>   University of Arizona


Nice idea, in theory, but mostly useless in actual operation.

Hydrogen needs electricity to be generated from water, which means that if you generate electricity, split the water, put the hydrogen through a fuel cell, charge your batteries then run your motors, you've lost something like 75% of the power, depending on the efficiency of all the gear. Just charge the batteries instead.

There are cases when Hydrogen is practical, such as when you need more range or power than batteries might offer, but you'd have to store the Oxygen onboard for underwater runs. An advanced version of the old diesel boats would work better.

There are three ways to store hydrogen:

Cryogenics, which will turn you into a popsicle (and your sub into an iceberg, in all likelyhood) if it bursts, but ounce-for-ounce stores more power than Gasoline (not, however, by volume, which is something to consider).

High pressure, which can have a fairly high storage density, although is prone to blowing up if abused, just like a SCUBA tank.

Or there are Hydrides, which are very heavy (400lbs for a tank the size of a spare tire), but have the same hydrogen density as cryo, minus the freezing and explosion hazards (handling a .50 tracer round with no leakage is pretty impressive).

For now, Hydrogen is a nice toy for experimenters and hobbyists, although I suspect that it may never go beyond that due to how battery technology is advancing. We'll see.

Anthony