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Fuel cells - a few doubts


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friends, have a few doubts regarding fuel cells, hope you guys will be able to enlighten me.

 

1. How much would it cost to make a fuel cell that gives a net output of 1KW?

 

2. What alternatives are available to platinum as a catalyst to produce the above mentioned power?

 

3. How much power would it consume to power an electrolysis unit to provide hydrogen for the above unit?

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...3. How much power would it consume to power an electrolysis unit to provide hydrogen for the above unit?
More than you'd get out of the fuel cell. But the usual plan is to strip the hydrogen from a hydrocarbon, oxidizing the leftover carbon to supply the heat needed to run the stripper.

 

did I just say "run the stripper"?......:confused:

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thank you guys for the prompt and useful reply. though i had an objection about the stripping, being POLLUTION. that was the reason i wanted to stick with electrolysis.

 

the concept was like this.

1) i need a fuel cell device that will provide me a net of 500W.

2) i therefore wanted to make one that would provide 1KW, and use 500W from that to run an electrolysis unit to provide further hydrogen.

3) what i really wanted to know was whether it was practically possible to run an electrolysis unit capable of supplying the required hydrogen for the 1KW cell using only 500W or thereabouts.

 

the other thing that was bothering me was the cost of platinum, so i had wanted to know if there was an alternative that was atleast 70% as effective, with about half the cost.

 

would sure appreciate some info on that.

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3) what i really wanted to know was whether it was practically possible to run an electrolysis unit capable of supplying the required hydrogen for the 1KW cell using only 500W or thereabouts.....
That would be a 2nd Law violation. It's absolutely impossible, cannot be done. The patent office wouldn't spend a nanosecond on your application.

 

Sorry to have to break bad news.

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3) what i really wanted to know was whether it was practically possible to run an electrolysis unit capable of supplying the required hydrogen for the 1KW cell using only 500W or thereabouts.
That would be a 2nd Law violation. It's absolutely impossible, cannot be done.
As chilehed notes, such a scheme is impossible. It’s pretty straightforward to see how such a one could use, say, 2 device capable of outputting 2 units of power for every one unit of power input to 1 unit of power output for every zero units of power input, a fairly sure sign of a TANSTAAFL violation.

 

You can, of course, run a hydrogen fuel cell on found energy sources – essentially anything that can be made to release hydrogen, such as methane ([ce]CH4[/ce], natural gas) or ethanol ([ce]C2H6O[/ce]). Many commercial fuel cells do. Such schemes, however, produce [ce]CO2[/ce] and [ce]CO[/ce] waste.

 

If you could find a supply of fairly pure hydrogen, say by skimming it from the sun’s corona, you could combine it with atmospheric oxygen to get more energy than you used getting the hydrogen (if your “hydrogen harvester” was very efficient). Too much of this scheme would deplete the atmosphere’s oxygen, binding it into water ([ce]H2O[/ce]). Free oxygen is hard to come by in the solar system, Earth’s atmosphere being the best source, so getting hydrogen in an ordinary “found fuel” manner appears an unworkable approach.

the other thing that was bothering me was the cost of platinum, so i had wanted to know if there was an alternative that was atleast 70% as effective, with about half the cost.

There are many sorts of hydrogen fuel cells that don’t use platinum – any of many sources, such as this wikipedia article, give good summaries of the more common ones, as well as of ones that don’t use hydrogen, or oxygen. Most very large fuel cells are non-platinum using types, such as molten carbonate, but suffer from low power/mass ratios, making them suitable for fixed, but unsuitable for small vehicle, applications.

 

There’s promising but to date unsuccessful research into making “quantum dot” materials that “fool” hydrogen into “thinking” it’s platinum, discussed several places in hypography.

 

Some have suggested that a good solution to the platinum cost problem is to make platinum cost less by greatly increasing the world’s supply of it. As planetary astronomers expect there’s a lot of it to be found in asteroids, schemes to get it from there abound, and have also been discussed here.

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thank you people so much for the replies.

 

i must admit i wasnt entirely forthcoming in the question, what i had actually wanted to say was that,

 

1. i was talking about 1KW net electricity, so obviously the rest of the output of the cell would be in the form of heat, because the electricity and heat combined have been known give an output of around 80 to 85%.

 

2. so i had planned to use a stirling engine on the heat output, in a way making it a kind of CHP device, using all of the current from the stirling, and about 500W of current from the fuel cell to power the electrolysis unit.

 

3. in such a case would it be possible, was what i had really wanted to ask.

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