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Renewable Energy: Small wind turbines?

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  1.  
    • CommentAuthorXT600
    • CommentTimeOct 1st 2022 edited
     
    I am considering getting a small turbine to supplement my solar pv during the winter. Currently my pv generates enough to keep the 250l tank of water hot from April to October without any intervention. Typically during the winter I may have to turn on the gas boiler once or twice a week for 20 minutes to top it up. Wondering if I could connect a small wind turbine 500-1000W to the existing PV Inverter to help during the cloudier days. ( or a separate inverter, I have a spare) Anyone have any experience with this? Small Chinese turbines seem incredibly cheap at the moment...:bigsmile:
    • CommentAuthortony
    • CommentTimeOct 1st 2022
     
    There was a very nice one based on F1 technology that was small and silent, it had an annular ring round it.

    Noise and vibration will be biggest problems with turbulence due to land, roofs and buildings a close second.
    • CommentAuthorrevor
    • CommentTimeOct 1st 2022
     
    Might be easier to set up a separate system rather than try and integrate the turbine with your solar PV. The turbines can output DC or AC and different voltages depending on design so you will have bit more choice. I wanted to add turbine to my solar pv but as I have a Li battery it is not possible because of conflicts between the BMS of the inverter/battery and the turbine controller. My friend experimented with a cheap Chinese made turbine it looked well-made but did not give anywhere near the stated output. He abandoned the trial. I came across a number of American you tube videos on small wind turbines do some googling you may pick up some ideas there.
    • CommentAuthorGareth J
    • CommentTimeOct 3rd 2022 edited
     
    Be very, very skeptical about any cheap turbines, particularly anything vertical axis. An off-grid chap down the road has a cheapish horizontal one with a body just bigger than a rugby ball. Maybe about 20kg. I don't know the rating but would guess between 1 and 2kW. Despite being on quite a tall pole, it takes a significant amount of wind to get going.

    I doubt anything in a residential setting would prove cost effective and I definitely wouldn't want one bolted to the house - vibration.

    If you've a field, with clear views all around, a small HAWT could be a great option. Although planning is a whole another ball game.
    • CommentAuthorSimonD
    • CommentTimeOct 5th 2022
     
    Posted By: XT600Small Chinese turbines seem incredibly cheap at the moment...


    As Gareth J says, be careful. The smaller the turbine, the higher the average wind speed needs to be to generate anything near useful. So first check the wind data for your geographic location and go from there. You'll probably find you need something with a tall-ish pole and few meters diameter blade, even for something like 3kW.
    • CommentAuthorGareth J
    • CommentTimeOct 5th 2022
     
    Every manufacturer who's done testing should be able to provide at very least a basic chart of wind speed Vs output and really should also have average windspeed vs annual production data available too.. lack of testing data suggests lack of testing. Or, I suppose, unflattering testing results.
    • CommentAuthorXT600
    • CommentTimeOct 13th 2022
     
    Thanks all for your comments :-) Instead of buying a cheap Chinese turbine I managed to get a cheap second hand UK made model, of 1kw. I've mounted it only about 5 meters above ground and now waiting for some wind to see what happens! It's a 48v output with built in rectifier. It appears to work in that spinning the blades produces a voltage. I have no idea if my old Sunny boy grid tie inverter will work with this turbine, so plenty of experimentation to look forward to. Grateful for any tips /advice from anyone who knows about this stuff :-)
    • CommentAuthorGareth J
    • CommentTimeOct 14th 2022 edited
     
    First thing to probably check is the permitted development rules. Not that you can't break them, just good to know if you are going to. There are some, frankly, ridiculous rules, like you can't have a turbine if you already have an ASHP.

    I don't know masses about it but turbine inverters are generally different to solar ones. They have to have a power curve programmed in to make the most of differing windspeeds, allowing the turbine to more or less idle at a low windspeed and increase turbine load to keep its speed in check as windspeed ramps up. I don't know if a solar inverter would be able to do that. There also needs to be some kind of failsafe, so, if there's a grid failure and high winds, or just very high winds, something to inject DC to act as a brake.

    Does the turbine site have a good aspect without many trees or obstacles? They really like "clean" wind. Turbulence from obstacles causes gusts that a setup will struggle to make use of, compared to a strong, steady breeze, even if it's pretty windy.
    •  
      CommentAuthordjh
    • CommentTimeOct 14th 2022
     
    Posted By: Gareth JThere also needs to be some kind of failsafe, so, if there's a grid failure and high winds, or just very high winds, something to inject DC to act as a brake.
    I'd have thought the failsafe needed to be integrated with the turbine itself? Else what happens if the cable linking it to the inverter fails? I also thought they were slowed by shorting the turbine (or nearly so) so that they generate their own braking EMF. And/or mechanical or aero brakes.
  10.  
    IDK much about it, but my neighbour who had a turbine thought their controllers come with large dump load resistors, which the controller can use as an electronic brake if it detects excess speed (the almost-short-circuit mentioned above).

    He also mentioned that the AC current from the wind turbine generator needs rectifying with quite a lot of smoothing as it is pretty spiky compared to the DC from a solar panel.

    The current is quite high (1kW at 48 V =20A) so cables need to be short and beefy and connections made well.

    There was something about the turbine earthing being kept isolated from the mains/house earth but I didn't understand it (not sure he did either).

    Not sure that PV inverters would be able to do this kind of stuff, or that it would be safe to try without knowledgeable helpers...
    • CommentAuthorGareth J
    • CommentTimeOct 14th 2022
     
    I'd have thought the failsafe needed to be integrated with the turbine itself? Else what happens if the cable linking it to the inverter fails? I also thought they were slowed by shorting the turbine (or nearly so) so that they generate their own braking EMF. And/or mechanical or aero brakes.


    Yes, you might well be right. I've a slightly bigger turbine. I don't know exactly how it all works but there's a very uncomplicated "brake" box in the tower that you can manually set or have to reset in the event of an overspeed situation. Would make sense that it's just shorting some wires together. Before that happens though, the inverter should load up the turbine and if that's exceeded, the blades should feather to reduce their efficiency. Only if both of those methods don't sufficiently slow it should the brake come on. I think some smaller turbines don't have mechanical stalling functionality though, they just hit the brakes if speed it too high. Decelerating the machine from full speed to nearly nothing in a second or two puts quite some force on the tower!

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