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Old 20-07-2020, 07:43   #1
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Vision of the future? H2-powered vessel.

A very interesting article. Is this our future?

https://www.cnet.com/news/this-boat-...from-seawater/
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Old 20-07-2020, 08:36   #2
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Re: Vision of the future? H2-powered vessel.

Not anytime soon, if ever. The article correctly states that hydrogen carries more energy by weight compared to batteries, about 10x. The article was silent on the volume of hydrogen compared to batteries.

Storing hydrogen as a gas is energy intensive, as it must be compressed. This compression requires as much as half the energy of the gas being compressed, and even more when it is stored as a liquid at cryogenic temperatures. In addition, it is highly flammable, tends to escape containment and reacts with metals in a way than renders them more brittle and prone to breakage. These are very difficult technical problems to solve on a boat. If a common rail diesel looks hard to maintain, a hydrogen system would be unimaginable.

Note that diesel contains about 40x the energy of a lithium battery by weight. My boat holds about 1,200 pounds of diesel. The equivalent in lithium batteries would be 48,000 pounds, or 50% more than my boat weighs.

Diesel is still hard to beat.
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Old 20-07-2020, 14:01   #3
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Re: Vision of the future? H2-powered vessel.

Hmmm what if you could make the hydrogen on demand? I wonder what that would look like?
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Old 20-07-2020, 14:42   #4
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Re: Vision of the future? H2-powered vessel.

The military who's biggest vessels are powered by nuclear reactors, have enough power on board to be able to produce fuel from hydrogen and carbon to fuel their planes. But that is not exactly a balanced energy equation at all.
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Old 20-07-2020, 15:30   #5
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Re: Vision of the future? H2-powered vessel.

The risk of fire would be another consideration. Remember the Hindenburg.

https://images.app.goo.gl/6d9cREh6UqfLQJTi7
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Old 20-07-2020, 15:58   #6
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Re: Vision of the future? H2-powered vessel.

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Originally Posted by Chris31415 View Post
The risk of fire would be another consideration. Remember the Hindenburg.

https://images.app.goo.gl/6d9cREh6UqfLQJTi7
Remember the Hindenburg? How old are you?

Are Honda still driving around their Hydrogen fuel cell car? It must have been 10-15 years ago, they were driving around a lot. It was on every car show.
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Old 20-07-2020, 16:07   #7
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Re: Vision of the future? H2-powered vessel.

Depending on the efficiency, it would be really cool to have a huge hydrogen tank and make H2 from sea water via wasted solar energy.

Imagine large arrays on Catamaran’s being put to full use making hydrogen for propulsion after they met house demands.

A big tank could be slowly filled and then used when needed.
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Old 20-07-2020, 19:13   #8
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Re: Vision of the future? H2-powered vessel.

So lets see: To produce 1kg of Hydrogen by electrolysis takes 180-200MJ of energy using the best known techniques.

https://en.wikipedia.org/wiki/Electr...ustrial_output


The resulting hydrogen has a calorific value of 141.8MJ


Taking the hydrogen (and oxygen) and running it through a fuel cell has a practical efficiency of ~36%. Citation: https://en.wikipedia.org/wiki/Fuel_cell#In_practice


Dang, sounding a lot like an ICE....


So overall efficiency is (141.8*0.36)/190 =26.8%


We are missing parts of the puzzle though. Seawater is hardly a good electrolyte, so one would first have to do reverse osmosis then make up a suitable electrolyte, manage the condition of the anode and cathode. Find a way to reliably separate hydrogen and oxygen, compress both gasses into storage tanks which would have to be large if pressures are not to be excessive. Then you need all the unobtanium - the fuel cell which is generally loaded with a lot of platinum



It just seems like it would be much more practical to drive the propulsion motors directly using PV panels and use excess to charge good quality batteries which can run the motors overnight, possibly at reduced power. If you consumed diesel overnight with the batteries adding to available power one would still achieve very good efficiency, especially in northern climates where heat recovery from the genny can provide the heating needed for the interior, hot water etc. In this scenario one could maintain cruise speed through the night. So put a lot of miles under the keel every 24 hours.





Quote:
Originally Posted by Chotu View Post
Depending on the efficiency, it would be really cool to have a huge hydrogen tank and make H2 from sea water via wasted solar energy.

Imagine large arrays on Catamaranís being put to full use making hydrogen for propulsion after they met house demands.

A big tank could be slowly filled and then used when needed.
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