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where does silicon come from
Sunday, August 26 2007
This morning Gretchen and I went over to our neighbor Andrea's place to join her extended family for brunch. This included Andrea's daughter and that daughter's husband. Also Andrea's brother was there, along with two more generations and a long-haired Dachshund. We'd brought our two dogs, who are always very well behaved in situations like this (so long as the cheese dip is placed more than two feet above the floor), but their presence drove the Dachshund to endless monotonous barking, to the point where he eventually had to be isolated in a bedroom.
Before the actual meal (which was to consist largely of fried bread stuffed with fruit), I was talking with Andrea's brother about things like high mileage vehicles and sustainable energy. He was a kind of a know-it-all type, which really had a way of setting his thermodynamic ignorance in high relief. He predicted, for example, the eventual triumph of hydrogen as a fuel technology, quickly explaining (as is often done) that burning hydrogen produces water as a waste product. I had to explain to him that the oxygen-hydrogen bond in water is an extremely powerful one that takes a great deal of energy to break when one decides one wants to make hydrogen. Where, I wanted to know, was all that energy supposed to come from. Later we were talking about why photovoltaic solar was having such difficulty taking off and I explained how much energy is required to make a solar panel. "But where does silicon come from?" he wanted to know. "Sand," I said. But then I explained how the oxygen-silicon bond in sand is also enormously strong and that breaking it to make elemental silicon crystals takes so much energy that, in many cases, silicon panels fail to generate as much energy as was required for their manufacture. There's an awful lot of hand waving and wishful thinking these days when it comes to alternative energy sources. But the reality is that there just is no easy way to replace the easy extraction of millions of years worth of stored solar energy once that extraction becomes hard (and it's steadily becoming harder).
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