Tuesday, November 19, 2002 :::
Steve seems to have understood that Kate Malcolm was getting the Ark ready; I did not. If she derives comfort in my brother's suggestions, I'm not sure I want to upset that, but, you know, what the hey:
Fuel cells, at least, don't get their hydrogen from water (for conservation of energy reasons that have been discussed); further, if the hydrogen is derived from water, the energy for deriving that hydrogen came from somewhere, simply shifting the problem. As for water coming in from the heavens, I would expect that there are natural processes for maintaining an equilibrium, but I don't know how substantial they are. Maybe they'd save us.
I'm not sure I'm going to convince residents of the Boston and New Haven areas that there's not that much worth saving near the oceans anyway, so let's try a different tack: me, I just can't imagine this is that much water. Let's make up some numbers: suppose burning hydrogen yields energy on the order of an electron volt per molecule -- chemical processes tend to be on that order -- then that gives us 100,000 Joules (a "faraday-volt") per mole, or about 5,000 J per gram, or what would be substantially more than a kW-hr per kilogram if any of these assumptions were precise. That's about 10 cents in electric power -- not quite, nor are other uses of power necessarily the same, but we're doing order of magnitude here -- so about 10 cents of energy gives us a liter of water, and $100 gives us a cubic meter. 3% of the U.S. economy goes to oil, I believe; as an estimate of global energy use, let's suppose 10% of the U.S. economy of $10 trillion a year, so $1 trillion, or 10^10 cubic meters. The world is 4*10^7 meters around; the area is the square of this divided by pi, so about 5*10^14 (check my zeroes), so that all that water, in liquid form, is about 20 microns a year. Presumably that will increase some day, but I don't think it would be a problem in the next fifty years at least.
By the way, I do my math in pen because it's easier to read. I used pencil in high school, but switched over in college. Where possible, though, I do my math in my head, where it erases more cleanly than pencil or erasable pen do.
::: posted by dWj at 10:39 AM
