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High efficiency solar cells and battery charger

Discussion in 'Electronic Components' started by Huang Paxia, Sep 4, 2003.

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  1. Huang Paxia

    Huang Paxia Guest

    I'm working on a Uni. project in which I need to build the power system for
    a micro satellite. It is in the form of 10x10x10cm cube.

    * Where can I find high efficiency solar cells in Australia? (6 surface x
    10x10cm)
    * Can some one suggest a solar cell powered battery charger circuit ?
    * What difference does it makes in terms of effieceny and life time for
    solar cells when they are on the earth surface or in the sky?
     
  2. This looks like a job for Google.

    You might want to shrink the solar panels a bit to allow for a shield
    and shock absorbing mounting. High efficiency solar cells shatter more
    easily than dry pasta. Your satellite will crush under its own weight
    otherwise, and I'm not even talking about launch forces.
     
  3. mikegw

    mikegw Guest

    Which uni?

    UNSW has the best silicon solar cells around..... At a price.

    Mike
     
  4. Guest

    The original poster might want to have a look at how the Fedsat was implemented.

    http://www.crcss.csiro.au/engin/fsdetail/bus.html

    A description of the solar cells is at the bottom of the page.
     
  5. Eric Scott

    Eric Scott Guest

    Search for Martin Green. He is a professor in Australia who specializes in
    advanced solar technology.
     
  6. Talk to the folks at Amsat
     
  7. You should ask these Qs on the alt.solar.photovoltaic newsgroup.

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  8. Whatever cells you use, add unfolding reflectors to increase the incoming
    light so you can get a little more power out of them. Silver Mylar reflectors
    weigh very little.

    Cheers!

    Chip Shults
    My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
     
  9. mikegw

    mikegw Guest

    Moving parts on a sat gives rise to a hole lot of other issues.

    Mike
     
  10. mikegw

    mikegw Guest

    Sorry some additional stuff. Martin Green is at UNSW. Blue sat at the same
    uni is using the good cells (space rated). If by some chance you are in the
    Sydney region UNSW has an open day this Saturday where among other things
    blue sat will have a display along with the solar car which as some similar
    ( and other very different) issues.

    High energy particles ( ~10MeV IIRC)will eventually degrade the performance
    of cells in space. LEO will have less particles around but it still a nasty
    place.

    Every component that goes into a bird will need to be space rated, and
    that's where you need to talk to people who know a damn sight more about
    this stuff than I.

    Hope this helps

    Mike
     
  11. Reflectors will not help.

    This is a 6-sided application that will most likely rotate in an uncontrolled
    manner. Any reflector extending out will cast a shadow on at least
    part of another surface (except for the instant one surface is perpendicular to
    the sunlight). To get any useful voltage each side must have multiple solar
    cells in series. With cells in series, the current fron the least illuminated cell
    will be the limiting current. The negative effect of shadowed cells is thus
    multiplied by the number of series cells.

    A good design would be to wire the outputs of the six multi-cell cube sides
    in parallel. Even better would be to have maximum power point tracking
    for each of the six sides, but the size/weight constraints combined with a
    possible rapid rotation would make this impractical.


    Bill Kaszeta
    Photovoltaic Resources Int'l
    Tempe Arizona USA
     
  12. Are there antennas or other things extruding from the cube, that might
    cast a shadow on some narrow areas of a single panel ?

    I assume that you must use separate diodes for connecting each panel
    to the main bus to prevent the dark cells from discharging some of the
    currents. But how about the shadows from narrow objects such as
    antennas that might cast a shadow on an otherwise illuminated cell ?

    I assume you would have to use multiple series strings with separate
    isolation diodes to avoid a narrow shadow from taking out a complete
    panel ?
    With multiple independent strings on each side, this would require 12,
    24 or even more regulators.

    Paul
     
  13. So does that mean they blow away easily in a light breeze? :)



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    goes directly to the trash unless you add NOSPAM in the
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  14. Oh, indeed they do- making them ideal for use in a vacuum, of course.

    Cheers!

    Chip Shults
    My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
     
  15. Ian Stirling

    Ian Stirling Guest

    The thermal control systems to dissapate the heat however don't.

    Mylar degrades rapidly due to free O.

    Reflectors mean accurate pointing, otherwise it'll simply shade as often
    as not.
     
  16. R. H. Allen

    R. H. Allen Guest

    You can check with UNSW, as others have suggested, but to my knowledge
    none of their cells are radiation hard. The main US suppliers of
    space-rated solar cells are Tecstar, Spectrolab, and Emcore.
    Efficiency will be a bit less in space, since the UV light filtered out
    by the Earth's atmosphere will still be present in space. However, the
    light intensity is about 35% higher in space, so total power output for
    a given cell will still be higher in space. When investigating solar
    cells, look for efficiency under AM0 test conditions and assume 1353
    W/m^2 insolation. Efficiencies under AM1.5 test conditions are useless
    to you. If AM0 efficiency is not specified, the cell is probably not
    space-rated.

    As for lifetime, electron bombardment is the primary degradation
    mechanism in Earth orbit. Cells can be designed to minimize the effects
    of this degradtion on efficiency, but those designed for terrestrial use
    will not survive long.

    A guy named Rauschenbach from the Jet Propulsion Laboratory published a
    couple of books on solar array design for space in the 1970s. They might
    be a little outdated now, but the basics are still be pretty solid. If
    you can't find them in a library or via interlibrary loan, I suspect
    they can be purchased from www.ntis.gov.
     
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