Off grid with Grid tie inverter

Discussion in 'Off Grid' started by billi, Nov 20, 2011.

  1. Hi

    Just came accross this Forum , while searching more Infos about the GTI ( Sun G wind grid inverter)

    And was quite impressed about the Information here .....

    I am off grid in Ireland with a 4000 watt PV connected to 2 outback MPPT chargecontrolers

    A 6 kw off grid inverer/charger (Victron energy ) plus a 1600 ah @24 volt battery

    and a 1kw (at 9m/s) Windturbine 24 volt charging through a standard controller and a 2 kw dumpelement ( that i have disconnected cause my off grid inverter switches on a AC Dump at about 30 Volt DC)

    Not 100% happy with my turbine and thought there could be an improvement to look arround MPPT chargers for windturbines , but was not too happy what i found - ok there is the midnite classic now on the market ,....

    So i thought i could go the "AC-coupling" route and connect my 24 volt turbine to a GTI and wire it to my house board
    My off grid inverter will supply the "Grid" to let the GTI connect to my house and the GTI supplys the loads in the house (parallel with my Off Grid inverter and the Offgrid inverter diverts surplus to the battery via its internal charger unit

    So my questions are :

    1. Will it be worth it , ie is there a rough percentage of improved power output with the GTI idea , compared to the basic wind chargecontroller ? ( i guess a significant improvement in lower wind conditions will appear)
    2. If i buy the 500 Watt Sun G wind grid inverter with the internal or external rectifier and dump load controller , and connect my 2000 Watt dump element to it but take the chargecontroller completely out

    Or will the GTI die when my turbine produces 1000 watt
    i guess i need two GTIs then or an additional 22-60 volt GTI ?

    3. Or can i connect a 500 watt DC GTI to my existing chargecontroller in parallel at the 3 wires AC coming from the turbine with an extra rectifier and leave chargecontroller in the system and GTI work in parallel ?

    Please keep in mind that my off grid Inverter will "kick out" the GTI occassionaly , so the turbine is on its own with the GTI for a few seconds and i would like to see these moments save for the turbine

    Thanks Billi
  2. Ok ........ "is there any body out there "?

    I attach an illustration of my system and the new idea that i have with the GTI (marked in Green)

    perhaps someone can have a look , or ;) even advice, or a better suggestion :rolleyes:

    I do not want to go the battery clamp idea in generall , but for a start i bought a 300 watt GTI to see if its worth it ...., on the long runn i would like to just feed the GTI from the Turbine, without Battery connection, and feed AC 230 Volt into my house


    Attached Files:

  3. leamywind1

    leamywind1 WindyNation Engineer

    Billi there is so much information on the GTI's on this forum please look around
  4. ok will look deeper , but have not found information about GTI running parallel to a charge controller ,

    and still not too sure , what will happen with the 1000 watt from the turbine....
  5. TomT

    TomT WindyNation Engineer

    If it looks like ours at all. Then get rid of the dump resistor on the GTI. Then the grid tie will just disconnect when it overloads. Then all power will go to the battery from the controller. I take it you are using the diode to stop back feed to the GTI from the battery. The dump at the controller should be made large enough to handle the wind turbine. If not add more resistors. Just make sure you buy a wind GTI with external dump load terminals.
  6. thanks Tom i still have to get the Diode (s) , but can i just connect the GTI to the 2 DC terminals out of the charge controller ?

    My dump connected to the charge controller can handle 2000 watt
  7. TomT

    TomT WindyNation Engineer

    If the GTI and battery share the same terminals . You will have to install the diode on the battery cable not the GTI cable. Or it will draw current from the battery and you do not want to do that.
    Your dump on the controller should be OK then.
  8. Ok i see , thanks Tom

    can you have a look at my illustration please

    Idealy i would like to have the GTI close to the house and avoid to lay an extra AC cable of 250 foot

    I guess i have to place a diode or thre to cope with my 4 kw PV as well , just in case :confused:

    Attached Files:

    • gti.jpg
      File size:
      339.6 KB
  9. TomT

    TomT WindyNation Engineer

    It looks like you are trying to connect to the battery buss bar. If so the diode will not help and you will be drawing off the battery . This is not recommended as it will run the GTI at full power and can damage it.
  10. Thanks Tom

    I tried something , that i have never thought of before ..............:rolleyes:
    Just wanted to find out , if my wind chargecontroller and its connected dump resistor works as well without battery connection

    So i tried it and disconnected the battery connection in the charge controller at about 26 Volt , it was quite windy ....
    chargecontroller stayed online with no battery connection and the digital meter in it went up instantly to 29.8 Volt and the dump resistor kicked in to hold that level

    So this sounds to me , i can disconnect the whole turbine from the battery and connect the GTI to the charge controller s DC output and feed my AC Grid
    Unfortunatly i only ordered a 300 Watt one ..... , but will see first how that will perform

    Thanks Billi
  11. so [​IMG]

    I figured out that my chinese wind-chargecontroller and its connected dump can work even without a connection to the battery .
    This means the turbine speeds up to about 30 volt and the dump holds her at around 29 volt then , without battery connection .
    So pretty safe not to overload the GTI

    That lesson learnt , there was nothing that spoke against a try out with the Sun G 300 watt Wind DC GTI (range 10.5-30 Volt about 100 euro delivered [​IMG] ) and a calm day as well so no charge at all and even without the battery connected the windturbine hardly managed to climb over 24 volt

    Connect the GTI to the outlet of my wind controller , connected the GTI to a house-socket , switched it on [​IMG] synchronised without any problem with my off-grid inverter/charger

    And it works great ..... voltage at DC input from the turbine drooped from about 22 Volt to 11 (when Gti was switched on ) and used my DC Clamp meter to measure Amps and get now mostly between 1 - 5 Amps so not a lot about 11 Watt to 60 Watt , but still better than nothing [​IMG]

    I connected my laptop to my Off Grid inverter to see how Hz are all fine at constant 50 Hz and i could see how the Amps from the Battery into the house where going up and down in relation to the Amps the GTI was feeding in

    So that seems to work , will think about it , and see how to optimise it , perhaps a second 600 Watt Gti in parallel , later , at least i know it can work..... off Grid with a GTI
    Here you see the back of the GTI with the clamp meter and 4.37 A @ about 11 Volt and 100 % certain these watts would have never seen my battery [​IMG]

    Edit : was curious to see if the bidirectional Ac -coupling idea works , so switched of nearly all loads in the house
    and surplus power from the GTI , that could not get absorbed from AC in the house , was transferred into my battery managed by the off- grid Inverter ,

    So many thanks to information i have received here

  12. Hi again .....

    So it seems to work , but it seems as well the turbine is slowed down a lot and does not catch up speed like before , i assume its because the 10-30 Volt of the -Too small- GTI "holds" her back from spinning faster , so is there anything i can do to it ?
  13. leamywind1

    leamywind1 WindyNation Engineer

    Yes, you can switch them to a higher voltage inverter. That is what i am doing and having great sucess at it. You must be very savoy to do this.
    Please see my post under wind relays for my work. I recommend using a wind switch from Inspeed if you are to do this. I would start off with a manual switch at first and switch between inverters to get an idea of how if works to make sure your turbine and system can co-exist together. You can get more watts out of runnng at a higher voltage (22-60) as well as all of your components running cooler. However every site is different. This does require alot of knowledge knowing your site and your controls to ge this all right, test,test,test.:)
  14. Hi and thanks , so just adding a 22-60 volt inverter parallel without the relay will not work good enough....#

    But , if i connect the turbine to my 24 volt battery again and the GTI in parallel with the diode , she will speed up again ( i hope )
  15. leamywind1

    leamywind1 WindyNation Engineer

    It may or may not b good enough. Every turbine is different. I have mine (windmax's 24v) with a 10-30v 250w gti and a 22-60v 1kwinverter and it works well. if you use a 22-60v inverter and clamp at 24v the all of the power will goto the bank more then the GTI. That will also depend if your bank is at t24-28v. Personally i have found that it is one way or another either batteries or grid tie. howerver i have had good luck using a 10-30v inverter and battery clamping at 24v but things get real hot.your turbine is a 1kw at what volatge is it rated at for cut in.12,24,48 and what wind speed does this voltage occur at? If you can hit 24v in 8-10 MPH winds then a 22-60v inverter may need to be used at 1kw. You do need to know the volatges of the turbine to get a close match to the inverter.
    Hope this helps
  16. Just an update , i use now an 600 w Sun G 22-60 Volt version instead .... , since a week and seems perfect and turbine speeds up nicely at arround 25 Volt i am measuring 10 A at the GTI input .... have seen 19 A as well and chargecontroller kicks in in parallel :)


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