Friday, November 16, 2012

Correcting A Misconception

A recent article in Science dismayed me. The authors wrote one of those "perspectives" articles describing the gist of one of the real peer-reviewed research articles later on in the magazine.

"Getting Moore from Solar Cells" by David J. Norris and Eray S. Aydil, Science 2012238, 625.

After describing some new and interesting materials for solar cells, the authors state:
"Although this sounds exotic, these materials are known to behave like semiconductors, allowing them to absorb the sunlight and create electrons"
At the risk of sounding pedantic, electrons are not created--nor are they destroyed. They are there in the dark in the beginning, and they are still there after the lights go out.  The electrons are merely excited by the light.

Photons knock up electrons and then leave the seen.

8 comments:

  1. There have been so many solar panel scams popping up since USGOV offered to underwrite them with a tax break (this is quite aside from the Obama supporters who received billions in stimulus money and then went bankrupt) that it has become a tough market, populated by a lot of pseudoscience.

    When I wrote my graduate paper/thesis at the Naval Postgraduate School on fractal based encryption (this before fractals were cool - in the dim and distant past), it was "peer reviewed" by three people including a PhD from the English department who didn't understand the math and took issue, not with the grammar, but with the formulaic conclusions. "Too many numbers - without enough verbiage". I sought out the "peer" and explained that numbers were verbiage. He looked at me in much the way as a cow looks at cars passing on a freeway and said, "not in my book". I suspect that he operated in much the same way as your 'electron creators' did in that article.

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  2. LL: If you actually look at the article (which is behind a paywall) the whole titular premise is disingenuous. It shows a graph of kW power generated by solar energy vs time (years) and notes that the amounts have roughly double every 2-3 years. This is likened to Moore's law (the number of transistors on integrated circuits doubles approximately every two years). If Moore's law were interpreted so liberally (kW of power transmitted by intergrated circuits) it would not be 18 months but much much shorter.

    The point is that solar circuits need a measure of efficiency per unit, not a measure of it's absolute increase per year.

    I'm not against solar energy per se. The main article in science talks about the inclusion of lead chloride to boast efficiency, but the backs off with the caveat of gee, maybe putting lead up on roof tops is not such a great idea. I made a similar objection to arsenic in gallium arsenide back here.

    Carbon-based storage of energy is so demonized in the MSM that we need to push back a little.

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    1. I think that inner cities (due to dire need for more power) should be allowed a special dispensation and license for using lead chloride AND gallium arsenic for special solar cells on top of tenement buildings. After all it's only fair to give them the most bang for their energy buck...

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    2. PS - better voting results too.

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  3. I have a question for Mr. Chemistry - I use cyanoacrylate glue in woodworking and have heard that a solution of baking soda in water will accelerate the setting thereof. Not wanting to spend money on the stuff one could buy in a store I made my own and it seemed to work.

    How does that magic happen?

    Thanks, and I'll take my answer off the air.

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    1. Mr Grit: I understand the magic in the following terms: link. Note the scheme depicts the linking up of chains of monomers. "Nu-" stands for nucleophile, negatively charged. In water, Nu- will normally be hydroxyl, OH-. Your bicarbonate increases the concentration of Nu-

      Note that wood consist of lots of hydroxylated phenyls: -C6H5-OH. The proton is easily deprotonated in base and then also serves as a Nu-. Lets call it Wd- (for wood, minus). This is how wood links up to the polymer chain which is the glue. A material like polyethylene has no hydroxyl groups which explains why such plastics are difficult to superglue.

      In my sexed-up version of chemistry, Nu- is the male nucleophile and the free monomer is the female electrophile. (see my "chemistry is like sex" tag for examples).

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    2. Thanks for the answer, CL - that makes the process much clearer.

      However, as with math, the more I learn about chemistry the more I realize I don't know.

      I was just about to ask you another question but did a bit of research and figured it out on my own. Yay me!

      But seriously, thanks again.

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  4. There's probably a 1st order differential equation for the rate of superglue polymerization. There's also probably a pH dependence.

    Of course, conversely, acid might inhibit the polymerization rate.

    You raise an interesting and general topic: the substitution of common, everyday chemicals for expensive commercial products. I will try to think of some other examples and post them.

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