--- In energyresources@y..., Ron Patterson <readyourdarwin@y...>
wrote:
> Oliver, of all the problem with converting sunlight to hydrogen,
> I believe water would be the very least of them. Huge rivers lace
> the land, any one most any one of them would be able to supply
> enough water for the operation.

Hmmm, maybe. The number I came up with (based on the numbers from
earlier in this thread) was 10E12 l/yr that, if entirely
electrolysed, would provide the equivalent amount of H2,
energy-wise, that we currently use in oil (that was my reading of
all the numbers)...

Soooo, based on that number, I get a water requirement roughly equal
to 5% of the flow of the Mississippi, which seems pretty significant
to me (10E12 liters represents about 19 days flow of the Mississippi
on average).

Now, I'm really just interested in this because it seems to be one
more relevant question in whether or not a "hydrogen economy" is
feasible; I don't think it is, but this is just another line of
thought that seems important in explaining why. I think it's
unlikely that we could use hydrogen in the same relative quantities
as we do oil now, so perhaps it's a strawman argument, but if
water is where we plan to get hydrogen from in such a world, I
think it's important to understand whether this is possible. Given
the numbers I think providing enough water for such an
endeavour will be a serious engineering problem, especially given
the amount of fresh water that we are using for other important
things.

Oh well. I'll find something else to dwell on now...

Cheers
Oliver