Can anyone explain the physics of how Photovoltaic Solar Panels work?

Discussion in 'Physics & Math' started by Tortise, Apr 3, 2005.

  1. Tortise Registered Senior Member

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    I realize it creates a kind of pressure that is the current. But lets say that it is charging a DC battery, in an over simplification, the photons are creating pressure on the electrons and the electrons move into the battery creating more negitive ions in the battery - not increasing the potential difference.
    My question is - Doesn't the voltaic panel run out of electrons? And if not why? The electrons are not making a circut are they? I don't understand.

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    Aren't we pushing the electrons out of the material of the panel and pushing them into the battery?
     
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  3. superluminal I am MalcomR Valued Senior Member

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    When a photon strikes the photocell (usually made of doped silicon - a semiconductor) electrons are knocked loose and flow creating a current.

    In recharging a lead-acid battery for example, you are not cramming electrons into an empty bucket. The charging current reverses the chemical reaction (SO4 / PbSO4) and restores its ability to produce its own current flow. The electrons from the solar cell do make a circuit.

    If you were charging a capacitor, you are filling an electron bucket and the electrons would cease to flow when the capacitor potential equalled the solar cell voltage.
     
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  5. MacM Registered Senior Member

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  7. Tortise Registered Senior Member

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    I understand this, my question is: How is it that the material of the panel is not drained of electrons? If electrons are knowcked loose and flow, do they flow to the battery and back again to the panel?
     
  8. superluminal I am MalcomR Valued Senior Member

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    Yes. The current facilitates the reversal of the chemical process that drained the battery in the first place. The electrons flow in a complete circuit.
     
  9. MacM Registered Senior Member

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    To get current to flow you must have a closed loop circuit. Electrons flow back into the material. When electrons are knocked out of the atom it lacks a valence electron and seeks to absorb one back in. But while the electrons are free they repell each other (like charges) just like two magnets having like poles. This causes the free electron to push down the circuit.
     
  10. bolonny Registered Member

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    thats where science turns into magic ......just like the magic photon....im thinking that when an electron gets excited enough it turns into a photon and when it hit matter it slows and turns back into an electron again....somebody please correct me with proven facts cause i hooked up my solar panels with a gridtie inverter and i cant seam to figure out where the unexcited electrons are coming from
     
  11. billvon Valued Senior Member

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    No, photons don't turn into electrons or vice versa.

    Think of it this way. A solar panel is full of electrons (and protons, and neutrons etc.) just like everything else is. When a photon hits a solar panel it "knocks" an electron towards the - terminal. So all the electrons bunch up at the negative terminal. If you connect a resistive load between the - and + terminals, the electrons flow from the - terminal to the + terminal through the resistor. No electrons gained or lost because it is all a closed circuit.

    Don't think of electricity as "a quantity of electrons" that you buy by the bucket or something. Think of it as electron motion; that's what current is.
     
  12. Pete It's not rocket surgery Registered Senior Member

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    8-year old thread.
    MacM died three years ago (obituary). It gave me a funny feeling when I moused-over his name, and the pop-up said "MacM is offline". Offline indeed.
     
  13. eram Sciengineer Valued Senior Member

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    There's so much history within these forums.
     
  14. RJBeery Natural Philosopher Valued Senior Member

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    Yes, and it isn't the first time I presumed an old thread was a new one. "Hey, I don't recognize any of these names!" heh

    I really hope they get the search feature working on old thread topics again, I'd hate to lose the ability to peruse it all.
     
  15. bolonny Registered Member

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    indeed ...but what the electrons are really doing is not moving through the wire rather they are bumping one another transfering there energy ,passing it from one electron to another
     

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