Grid Tie Inverter Efficiency

Discussion in 'General Electronics Chat' started by gregtomko, Jan 4, 2009.

  1. gregtomko

    Thread Starter Member

    Sep 29, 2008
    16
    0
    When a grid tied inverter is sourcing electricity into the grid from an on site power source, such as a photovoltaic panel, what is the loss in efficiency for a standard household if they are sinking an equivalent resistive load as the PV panel is sourcing. More specifically, if a house is sinking 1KVA of resistive rated incandescent lighting, and the PV panels are at the same time sourcing 1KVA actual energy into the system, what is the loss of efficiency because the lights are experiencing higher voltage than the grid line voltage, and how do you calculate the loss, does it depend on the parameters of the transformer (pole pig) feeding the house, and are there any universal generalities?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Have you approached any utility companies on this subject? The state of California has a fairly extensive program with PV panels and synchronous inverters on residential housing.
     
  3. floomdoggle

    Senior Member

    Sep 1, 2008
    217
    2
    Hey Greg,
    @ 1kva, you only have enough power to light a couple of lights from the battery you are charging. On an average sunny day. Solar charging of batteries is the only way to go. Your average from 1kva, on a daily basis will probably run about a usable amount of 300 - 450 watts. Believe me I am on your side.
    Tying that amount of power to the grid will be a waste of money. You would use up that amount trying to turn the meter backwards. Unless you have an electric company willing to install a meter able to run backwards.
    Try using the energy to supplement your usage.
    Dan
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    Grid tie inverters should match frequency, phase, and voltage to the grid. A few volts of potential difference between the inverter and the pole pig will be a very very bad thing.

    Consult your local utility company for advice regarding grid tie inverters. Comply with all applicable codes!
     
  5. gregtomko

    Thread Starter Member

    Sep 29, 2008
    16
    0

    How would the inverter supply excess on site power back into the grid if there were no potential difference?
     
  6. italo

    New Member

    Nov 20, 2005
    205
    1
    You have to do what every source of power to the grid does. Meaning detect the power and transmit these results to the power source that you are buyng power at the time. Belive it or not this power can come not even from that source but far away depends whether where they are buyng power from at this instant. The power level that you are interested is insignificant to mega watts sources. For instance all those wind sources in CA. supply 40 mega watt with a strong wind. With no wind the generators use power to min-spin.Even with 40 foot blades to begin spinning is a problem. Of course it is free but the initial cost was very high and maintanance is high too . without the CA. taxes help it would have never happened.
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    Think of the magnitude of the load impedance. The secondary of a pole pig is going to be on the order of 1 ohm, and the primary will look into a few milliohms at most. Won't take much actual potential to push current.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    Taking Beenthere's comment further, a couple hundred amps times a few milliohms is a couple tenths of a volt. The service feeders to your residence can safely handle only a couple hundred amps.

    Long before any potential difference has noticeable effect on the lights, breakers will trip.
     
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