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Mr Grufty Jim Sir !!
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grufty jim
grufty jim
1978 posts

Re: Hydrogen cells?
Dec 10, 2001, 18:10
> Were a desert annexed and filled with rotating
> banks of photovoltaic cells the energy captured
> would be sufficient to split hydrogen and transport
> it via pipelines etc to fuel cells, generating enough
> energy to fuel our needs?
>
can't say as i'm up to date on the "Z Machine" morfe; but i tend to mistrust anything with that kind of name... there are hundreds (i kid you not) of crazy ideas for "cheap, abundant energy" out there. as a member of a number of energy-related mailing lists, i get to read about lots of them. i think nuclear fusion is the best of those, but even that's only "theoretically possible" in a controlled environment.

as for hydrogen, there are serious drawbacks with that too. hydrogen isn't considered an "energy source" by energy researchers; rather it is an energy carrier (the difference is important). our current primary method for producing hydrogen is through the use of fossil fuels (it's extracted from natural gas). this is obviously a non-starter if we're looking for "renewable" energy.

however, it can indeed be manufactured from water using electricity. the main way people have considered doing this is PV cells on giant rafts (rather than in the desert... as then you'd have to move the electricity to a water source, with a subsequent loss of power... remember energy is lost at every stage of the process; generation, distribution, conversion and usage).

unfortunately, a little known fact about PV cells is that the most efficient ones we currently possess
require twice as much energy in their manufacture (from fossil fuels) than they produce over their average lifespan. so even if we doubled the efficiency of PV cells (possible, but hardly a certainty) we'd need to use all of the power they generate just to build the next lot.

there's also the materials used to produce PV cells... currently mostly plastic (i.e. oil) and aluminium (i.e massive electricity expenditure), plus there's the no small task of hydrogen storage and distribution - fuel cells are high tech; they require precision manufacturing and the use of a lot of refined metals (metal refining is - as mentioned elsewhere - very energy intensive).

and we've yet to get onto the rather important issue of how much of the surface area of the planet we'd need to devote to PV cells in order to transition to a hydrogen economy... don't have the exact figures here; but i recall reading (and don't quote this; it's a vague memory and needs confirmation) that the USA would need to cover the entire planet in PV cells twice over to meet it's current energy usage.

now, the USA is simply not going to be able to maintain that sort of energy consumption; but it indicates the scale of the problem.
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