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Solar Cells R Fun — Parallax Forums

Solar Cells R Fun

ercoerco Posts: 20,261
edited 2011-04-24 19:52 in General Discussion
Just got my Ebay China solar cells in today (lightning airmail free shipping) and I played around with them in the bright SoCal sun today. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=160574296057

Very interesting voltage-current output characteristics, quite different from what I anticipated. 60 mA short circuit current, 6.2V no load voltage. 60 mA output current down to 5.5V, then it drops off slowly. Getting peak power out is a game, like driving a Prius. Looks like quite an interesting subject, no wonder Matt Gilliland is having fun with his solar-powered BoeBot. Interesting website with some characteristic curves at http://www.californiascientific.com/resource/Solar%20Cell.pdf

Chime in with your suggestions and experiences!

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2011-04-23 20:25
    erco,

    I would be interested to see the actual characteristics of the solar panel you have and compare that to one that we sell. I did this with our 9V 1Watt cells (see attached) ... Something interesting to note. the operating characteristics are different after the solar cell has been heated up sitting in the sun, versus 'just placed' in the sun. The measurements that I took were after the cells had been sitting out in the sun for at least 30 min. ... Also, all of the tests were done with various combinations of 47 Ohm resistors. (I just happened to have a handful of 47 Ohms that I used)
    xls
    xls
    MPP measurements on solar cell.xls
    33K
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2011-04-23 23:04
    erco, I wonder how hot a solar panel can get before it will be damaged?

    I say this wondering how much light you could place on it before it failed.
    like take an old satellite dish and cover with foil and put the small panel
    at the focal point and track the sun. The power output should go way up right?

    Or use one of those flat plastic magnifying sheets to concentrate the light
    on the panel.

    Be fun to play with and see what could be done.
  • vaclav_salvaclav_sal Posts: 451
    edited 2011-04-24 08:32
    Just to illustrate how behind the times, in my opinion, we in US are when it comes to serious usage of solar panels.

    While recently visiting Germany I was astonished seeing acres and acres of solar panels everywhere. Entire fields and every other milk barn covered !

    Sorry but it became so normal that I did not take any pictures to show all your folks from Missouri!

    I am not sure what is the holdup here, we have plenty of space and sunshine too.

    Would be nice if someone from “over there” ( Bavaria) posted some pictures.
    I never did find out how much it cost to build all these solar collectors. I think the “going rate “ in US in about $300 per 100 watts panel. Not too cheap, but it is green!
    Vaclav
  • ercoerco Posts: 20,261
    edited 2011-04-24 14:38
    Thanks Beau, I did see that the electrical output drops as the cells' temp increases. We need to keep these babies floating in a kiddie pool! I always wondered about the new Prius solar roof, which I believe is supposed to cool the interior of a parked car. Wouldn't a simple white roof be cooler than a black solar cell roof anyway? Seems like diminishing returns...
  • vaclav_salvaclav_sal Posts: 451
    edited 2011-04-24 19:52
    Erco,
    I bet white roof would work, but it is not high-tech. Maybe that is a hidden reason why white is a popular car color.
    I drove Prius once as rental a was totally distracted by the "what is happening" display. I suppose folks who talk on the phone do not notice that.
    I have `12V 2 W about 6 by 6 inches cell and it gets pretty hot in full sunlite. Have not found a real application for it.
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