wind turbine and 500 watt grid tie problems

Discussion in 'Start here' started by darryl lan, Jan 11, 2012.

  1. OKAY, I'M GOING NUTS TRYING TO FIGURE THIS OUT.
    I HAVE A DC PMA WIND TURBINE GENERATOR THAT IS PUTTING OUT 60VDC @ 10 AMPS +/-
    IT IS HOOKED TO A 500 WATT GRID TIE INVERTER. THE NEW ONE WITH THE DUMP LOAD CONNECTIONS ON IT.
    THERE ARE NO BATTERIES, JUST HOOKED RIGHT INTO THE HOME GRID, VIA THE INVERTER.
    WHEN I PLUG IT ITO MY KILL-O-WATT METER AT THE WALL, IT FLUCTUATES BETWEEN 0.3 AND 24 WATTS.
    I'M TRYING TO FIGURE OUT WHAT IS GOING ON, IN THAT I AM NOT GETTING EVEN CLOSE TO 500 WATTS!
    ANY COMMENTS WOULD BE WELCOME ---- THANKS WINDY NATION.
    DARRYL
     
  2. Andy R.

    Andy R. WindyNation Engineer

    Do you have the PMA up in the air or are you doing a "bench test" with a drill for example. Any idea of the RPMs? Any more information would be helpful like the type and volt range of the inverter.

    Thanks.
     
  3. Minnesota

    Minnesota WindyNation Engineer

    What is the voltage range specified for the GTI you have? Some only cover up to 30V. Yes, you need to be specific of what turbine and GTI you are using and how you are doing the testing. Please also refrain from using all CAPS.
     
  4. okay, here is my story:
    i live in a subdivision in katy, tx.
    nice 2,500 sq ft. home. and guess what, --- a home owners association.
    they don't allow for wind turbine towers, that's a no-no!
    screw that, screw them - i have 2 a/c units that cool my house - and yes, 2 outside condensor units.
    each with a fan that blows 17-18 hours a day and at who knows what air speed. never measured it...
    anyway, on one of the units i built a rig that i have attached my pma wind turbine to, and it faces strait down into the upflowing
    exhaust air.
    i made my own pvc fan blades and attached 6 of them to the pma hub ( good balance - no vibration). -- span is about 22" total.
    when the a/c unit kicks on and the condensor fan starts to blow, that little wind turbine spins like a bat out of hell.
    i measure 60 volts dc with my volt meter.
    according to the cut sheet that came with the pma, 60 volts and 10 amps is reached at 650 rpm.
    i have 4 gauge wire running thru the wall and into my 500 watt grid tie inverter, inside the house.
    inverter info is sparse:
    nominal ac out is 450w
    max ac out is 500w
    ac volts out is 90-130v @ 46-65 hz
    input voltage is stated at 22-60 volts dc.
    it's a thing of beauty, i'm telling you -- and for all my planing, only 24 watts max out put!
    any guesses or suggestions?
    thanks again.
    darryl
     
  5. Andy R.

    Andy R. WindyNation Engineer

    WOW! never thought of anything like that but it sounds like a cool idea. Harness what you can.

    When you measure 60 volts, are they "open Volts" without a load on it or does it have a load attached like the inverter?

    Do you have any photos?
     
  6. windyguru

    windyguru WindyNation Expert

    You are probably measuring open circuit volts. I assume you have the PMA hooked up directly to a voltmeter when you are measuring the volts? This does not correlate to power production at all. It is like measuring the rpm of a drill/drill bit in open air. Then you take that drill and drill into some stainless steel (the stainless steel is your load) and you assume the rpm of the drill will be the same as in open air. The harder you push on the stainless steel (the load) the slower the drill's rpm.

    In your case, the grid is your load and it is slowing down your PMA which is normal. Power readings must be done under a realistic load to get realistic results.

    A 22 inch blade span is not going to get you much more than 15-20 Watts in decent winds. It seems everything is working as is should. Sorry to be the bearer of bad news.
     
  7. Minnesota

    Minnesota WindyNation Engineer

    The dirty little secret is that those amps in your chart (I suspect the DC-540 PMA) are with the PMA dead shorted, and thus 100% of the watts are dissipated as heat by the PMA itself. Ever try to hand crank a dead shorted generator? Test show humans can only handcrank about 30 watts on average for any extended period of time (a few minutes).

    When you attach the GTI, it wakes up as the voltage hits 22V from the turbine, at which time perhaps 1.4A begins to flow yielding 24w to the grid. The rpm drops to to a fraction of what it was without the load.

    Here is how a well designed 22-inch turbine would perform.
    twentytwo.jpg
     
  8. Umm, yea - no load - just measuring at the terminals on the pma.
    thanks Andy.
    Darryl
     
  9. --No, not bad news at all.
    I'm new at this and still learning - all info is good!
    I will measure the volts at the GTI while under load and see what I get.
    thanks,
    Darryl
     
  10. Nice!
    thanks for the input Minnesota.
    Darryl
     
  11. Andy R.

    Andy R. WindyNation Engineer

    Darryl, real interesting project. Let's see if I have this right. You have an air conditioning unit which has an exhaust fan with a consistant air flow in front of your turbine. That's a real big advantage that you have over the typical wind system.

    As Minnesota's chart indicates, you ain't gonna get too much power with only a 22 inch blade diameter and considering that, 24 watts might not be that bad. That said, I can't think of too much that you're doing wrong other than possibly improving the blade system.

    1. Could you increase your blade diameter size? That would make a big difference.

    2. PVC blades are not the most efficient. I don't think that Windy nation sells blades that size but then again, you have a very unique project.

    I know a guy that carves blades any size you need if you need that option.
     
  12. Andy,
    Yes, you have the right idea of my set up. I will post a picture, as soon as I figure out how to do that!
    I just got done hooking everything up again and measuring volts while under load.
    Big difference! The voltage coming in from the PMA was really all over the place.
    It jumps wildly from 21v to 28, 36, 24, even 44v! and so on, up and down... you get the idea.
    As it does, the watts on the kill o watt meter also fluctuate, .5w - 8w, 24w even up to 40w!
    I'm not sure what would cause these changes.
    I went outside to check the turbine and I could visually see that the RPM's where slowing down and picking up again.
    This is all while plugged into the GTI.
    Nothing like the,"no load", test of 60 volts!
    Perhaps your right about the blades.
    Maybe they are not really that great? I was wrong about the blade span, the opening where the air rises from the a\c unit is 22"+ ---
    the actual blade span is 27"!
    I'm just going to keep at.
    Something will pop and I'll get it right - and I do, wholeheartedly, appreciate every ones input!
    Thanks ANDY --
    DARRYL
     
  13. Okay folks, here it is!
    I don't no if I posted correctly or not.
    Only way I could figure to do it!
    thanks,
    DARRYL

    PICT5761.JPG PICT5760.JPG PICT5762.JPG
     
  14. Andy R.

    Andy R. WindyNation Engineer

    The blades look good and it looks effecient the way you have it close to the unit.

    I'll let someone else chime in on the PMA. ;)
     
  15. leamywind1

    leamywind1 WindyNation Engineer

    LOL. I had the same idea a few years ago. Do you think a shroud to funnel more air into the blades could be used and would work?

    Is it a wind rated GTI? Sun G WDL?

    You could try tieing to a 24v bat bank, use a dump load controller to dump at 26v and use a GTI 10-30 or 22-60v. This may keep your watts more steady at the dump time.
    You may want to try like smaller tractor batteries since the wind speed is always going to be at a steady rate from the condensor fan. There are a few ways you can do this thta's for sure.

    Just a thought.:)
     
  16. Hi Leamywind1,
    This GTI is for wind only but,
    I think I actually figured things out!
    My own miss conception of how the inverter its self is supposed to work.
    I thought it was like a standard inverter, like the kind that you hook up to a car battery-
    and it converts the 12 volt, into household 120v. and what ever watts the unit is rated for.
    Stupid me, I see this 500w wind turbine inverter, with 22v-60v input, and figure -wow, I can hook a small wind turbine
    to this inverter and get 500 watts into the grid.
    Now I understand; it can handle up to 500w, not it produces 500w from my 25 to 40 volts coming in.
    My turbine pushes 20-30 watts or so, so that's what goes int the grid. The inverter just passes it on!
    So I guess in the end, it was a fun project and it's working as it should!
    What would be cool is, if all the WAL-MART, TARGET and other big box and grocery stores could harness their A/C unit fans, the big ones, and make
    a little ELECTRICITY!
    Over and out,
    DARRYL
     
  17. leamywind1

    leamywind1 WindyNation Engineer

    Ok well done. Good experiment though.:)
     
  18. windyguru

    windyguru WindyNation Expert

    What would be cool is, if all the WAL-MART, TARGET and other big box and grocery stores could harness their A/C unit fans, the big ones, and make
    a little ELECTRICITY!

    Daryl,

    That is a common misunderstanding of energy production that I must address. There is NO free lunch. In our universe, if you want energy you must extract that energy from something. Summarizing the first law of thermodynamics: Energy or matter can neither be created nor destroyed.... just transferred from one state/phase to another. In your case, you are transferring the kinetic energy in the wind created by the AC fan to your blades, then to your PMA, which is then transferred to the grid tie inverter (This is important AC fan to blades to PMA to grid tie inverter.)

    Without going into the 2nd or 3rd law of thermodynamics, you can already see there is a problem here. Nothing operates at 100% efficiency. So the AC fan, your blades, the PMA, the grid tie inverter all operate at well below 100% efficiency. To keep it simple, let's pretend they all operate at 75% (Some better than this and some far worse.). Then the energy harvested is 0.75 x 0.75 x 0.75 x 0.75 = 32%. Thus, in this example, one could only harness 32% of the electricity supplied to the AC fan!

    Now, I now what you are thinking. Well, the AC fan has run anyways so why not harness some of its energy and turn my meter backwards? This theory is also flawed. (1) By putting blades in front the AC fan, you are blocking the air from flowing freely from the AC unit. The fan must work harder to move the same amount of air. Thus, the fan must consume more energy to move the same amount of air compared to if no blades were there. The system (blades, PMA, GTI) cannot "collect" 100% of the extra energy the AC fan must produce to move the same amount of air. Therefore, YOU WILL ALWAYS BE CONSUMING MORE ENERGY FROM THE ELECTRICAL GRID THAN YOU ARE PUTTING BACK IN.

    Also, by obstructing the AC fan with blades and making it work harder than it is designed to, you run the risk of overheating the AC fan motor and destroying it. You also lower the efficiency of the AC unit so you are paying more money to keep the house at a constant temperature (compared to if the blades/PMA/GTI were not there). All in all, it is a lose/lose situation.

    Remember, there is NO free lunch and perpetual motions machines do NOT exist in our universe.
     
  19. I see what you mean --
    Point well taken!
    To tell the truth, I did wonder if the PMA blades were making the AC work harder - perhaps just on start up I thought...
    But I never did want to run my meter backwards, just return some watts back to the grid while the air movement was there.
    I need to get a house out in the country where I may erect a tower. Until then, this is just a toy.
    Thanks GURU!
    DARRYL
     

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