"700 watt" eBay wind turbine

[makenzie71]

700 watt 3 blade turbine

I had REALLY hoped to be able to put this thing on a lathe and test output per rpm but my machinist is out until nearly February...so no luck there.  I will pull it down in the spring and take it to him to test when I'm painting the pole and cleaning up.

So, to start with, like every chinese thing I've had come in, there were problems right out of the box.  This one did not come with a charge controller and the tail vane was bent.  Not insurmountable problems so I settled with the vendor (very close to 50% off).

Again, measuring stuff...



10g braided wire off the slip ring



Slip ring and brush assembly.  Nothing special.  This is the exact same arrangement as in the 500w turbine but the mounting flange here is larger.



Same 36/12 coil and magnet configuration as the the 500w setup, though it is larger.  The wire is larger, case is larger, rotor is larger, magnets are larger.  Interestingly, to me anyway, the tolerance on this one was tighter.  I had a lot more trouble getting this one apart...I had to give up all together trying to get the rotor out of the coils for fear of damaging teh coils in the process...means I was not able to measure the magnets, unfortunately.  Just like the 500w, one single large bearing supporting the rotor.



18-ish-g wire on the coils.



Broken magnet!!



3/4 flared shaft



Whole body is aboout 6.5"



Blades are a hair under 36" long, and are pretty rough.  The leading edge is clean and smooth but the trailing edge is rough and "unevenly" cut.  They're all done the same.  It looks like maybe the blades are held in a jig and very quickly hit with burr to clean up casting or something.









I've had this thing on a 25ft pole for about a week...



I am dubious of the 24v claim in the listing.  It seems to drag a lot when connected to a 24v battery bank, but I have not been able to see how it handles 20mph+ winds yet.  Most we've seen is 15mph gusts...apparently the way to correct all the "it's too windy to do anything outside" days is put up wind turbines...so jury is still out.  Unloaded, though, the thing spools up pretty fast and easy and kicks out 60+ after the rectifier in a 10mph breeze.  I'm still learning a bit about managing voltages but it seems to me like it might do better on a 48v bank that'll let it spool up more.  My current controller cuts and dumps it after 34v when there's no load on the batteries.

I will be updating this as I have new information and, as with the last one, suggestions and things to try would be appreciated

[makenzie71]

500w turbine for reference

[makenzie71]

Little update:

I did try this thing on a 48v battery bank and it just free wheels and doesn't build any power.

It's currently kicking out 350w in a 17~20mph wind.  It peaked in the last two hours at 550w.  It's tied to a 36v battery bank that's currently running a 1000w grid tie inverter.  It's actually doing pretty okay.

I think this turbine is actually worth checking out.  I'm starting to think that if the thing really got into 25~27mph wind it'd get pretty close to the claimed rating.

[makenzie71]

checked it before going to bed...at some point in the evening the turbine peaked at 676 watts.  It has logged a total of 2.24kw/h in the last four hours...this is going into the 36v bank and into the eBay 1000w grid tie inverter (some loss along the way).

I think I need three more of these things.

[SparWeb]

It's currently kicking out 350w in a 17~20mph wind.  It peaked in the last two hours at 550w.  It's tied to a 36v battery bank that's currently running a 1000w grid tie inverter.  It's actually doing pretty okay.

I agree, this is good performance.

Since it seems to do so well on 36 V, do you want to leave it that way, or get it to work on 24V, too?

The problem you described on 24V sounds like the blades are stalling because the 24V keeps them too slow.
If so, you might try a strange trick: put a large 1/2 ohm or 1 ohm resistor on the output wire to the 24V battery. 
The effect is that the turbine runs faster but still charges at 24V.
It's a bit brutal to waste some heat in the resistor but not a lot, and it's surprisingly effective.

But maybe not urgent, if you're got it working on a 36V bank and you have a 36V inverter, too.

[makenzie71]

Something like this?

I might try it...I wonder why adding resistance to the lead would help it spool up?  If that's a thing that work it'll definitely help with my smaller one.  It's choked down on the 36v bank and only making about 150~175 watts in the same wind.  It was doing 200~250 in similar wind the other day tied to a 48v bank.

[mmurray70]

Nice to see its working as described.

How is the pole doing? What size pipe/wall thickness and how tall? How much unsupported? I was considering doing something similar with my shop but a little nervous it wouldnt be solid enough, or tall enough.

[makenzie71]

Nice to see its working as described.

How is the pole doing? What size pipe/wall thickness and how tall? How much unsupported? I was considering doing something similar with my shop but a little nervous it wouldnt be solid enough, or tall enough.

The pipe is oilfield drill stem.  It measures 3.5” OD and has a wall thickness of .375” (3/8”).  I asked around about using this stuff and got a lot of feedback about it not being stable, especially with my planned footer...and i was honestly concerned about rigidity as well...but i went with it anyway because it's cheap and the risk was pretty low.  I have my 500w ebay turbine on a 22ft stick sunk 4ft in the ground with 600lbs of concrete...18ft above ground, it is unsupported and stays stable, it has seen 45-50mph winds with no trouble.  The 700w turbine above is on a 25ft stick supported approximately 12” off the ground and is braced at 9ft off the ground.  There is about 16ft unsupported.  I think highest peak wind it's seen is 35mph, maybe 40, but has not show any signs of stability issues.

This one i made on a hinge so i can tilt it down.  The other one is just a stick in the mud, as it were...to get to the turbine i have to break out the tall ladder and climb up and i can tell you that with 180lbs of me up at 18ft up it stays put mostly but feels like you're riding a spaghetti noodle.

I am strongly considering buying two more of thes 700w models and, if i do, i would put them on full 30ft sticks.

[MagnetJuice]

Adding resistance to the line after the rectifier is a good way to tune the turbine to the right RPM. (The resistance can be added before the rectifier, but you will be dealing with 3 wires instead of just one) The resistors that you showed on the ebay link are only 10 watts. You need to use power resistors that can dissipate about 75% of the rated power of your turbine. For your 700-Watt turbine, you will need a resistor that can dissipate over 500 Watts.

The resistance suggested by SparWeb (1/2 ohm or 1 ohm) is good for 24 volts. For 12 volts you would need more resistance (½ ohm or less) and for 48 volts you need less resistance (around 2 ohms) These numbers are approximations, experimenting with different values will give you the right results. That is what I meant by “tuning”.

It seems like a waste of power to add resistance to the line of a turbine, because less power is going into the battery, but if the turbine is not running at the right RPM, it is not making a lot of power either. At lest you can use the heat from the resistors to heat your room a little in the winter.

For all the experiments that you are doing, you should get about 8 of these and try combining them in series, parallel and/or series/parallel to get the right resistance and power value.

https://www.mpja.com/2-Ohm-120W-Power-Resistor/productinfo/17786+RS

You asked this question, “I wonder why adding resistance to the lead would help it spool up?”

Here is a short answer to help you visualize it. What happens if there is no resistance to the turbine? (open line) The wind will make the turbine speed-up and run fast.

What happens if there is a lot of resistance on the turbine? Like 0 ohms? (Short-circuit).

The turbine will stop turning, unless there are extremely high winds.

The combined resistance of the cables, rectifiers and the batteries is somewhere between those two extremes.

The turbine sees the battery as “resistance”, usually 1 ohm or less. That is why the turbine slows down at the cut-in voltage.

By the way, thank you for all the useful testing that you are doing. I am sure that it is helping a lot of people here.

Ed

[DamonHD]

The resistance suggested by SparWeb (1/2 ohm or 1 ohm) is good for 24 volts. For 12 volts you would need more resistance (½ ohm or less) and for 48 volts you need less resistance (around 2 ohms) These numbers are approximations, experimenting with different values will give you the right results. That is what I meant by “tuning”.

Less is more?  Did you get some words in the wrong order?  I am befuddled!  B^>

Rgds

Damon

[makenzie71]

I'm curious if i'm understanding this resistance thing properly.  If i ad a 500w/1ohm resistor inline with the output wouldn't it basically be eating up (up to) 500 watts that would otherwise be going to the battery?  It seems like a steep price to pay for keeping the rpm up.

[mab]

magnetjuice is in essence right  but has confused us slightly by going against convention and referring to lower resistance values and 'more'.

the point is that with the turbine connected directly to the battery, the turbine speed is effectively clamped to the speed it's going when the batteries start charging, so when the wind speed increases the turbine speed doesn't, eventually the aerofoils stall - i.e. they're no longer 'flying' - so they are not harvesting the energy from the wind effectively - so the output from the turbine drops sharply.

the resistance softens the 'speed clamping' caused by the battery, allowing the turbine to keep flying and keep producing lots of amps - yes you are wasting power in the resistor but as long as you're getting more amps into the battery than you would with the turbine stalled you are winning.

[MagnetJuice]

I am sorry for the confusion about “more” or “less” resistance.

The resistance is in series with the load (added to the line). Yes, ½ ohm is less resistance than 2 ohms.

I hope that your mind gets unbefuddle Damon 

Makenzie, a resistor in series with the line will consume power but not 500 watts. The 500 watt rating means that the resistor has to be capable of letting that much power pass through it. The resistor has to be able to handle the more than 20 Amps of current coming from the turbine at 24 volts. Most of that current will go into your battery.

Ed

[makenzie71]

I think since it's peaking out pretty well on the 36v bank that I'm going to leave it as is, but I did order a resistor for the littler turbine.  The 36v bank chokes it down a bit...it hasn't exceeded 250w on it while it was cruising closer to 300w on a 48v bank.  It might help that one out.

[makenzie71]

Little update

[makenzie71]

Wind is gusting to 25~27mph.



I think if you're going to buy a chinese turbine, this is the one to go for.

[makenzie71]

I've been thinking I'd like to have two or three more of these things but I got no idea how the hell I'll manage them when we have these 25mph days.  I'm half on the fence to turn them off but the wind is suppose to be slowly dying out over the next three hours...and I really like seeing the watt meter off the panel running close to 500w going back in the grid.

[MagnetJuice]

Maybe you already know about this wind tracking website, but in case that you don't, here it is:

https://www.fieldlines.com/index.php/topic,149723.0.html

It could be useful to you to help you see the winds expected in your area ahead of time.

Ed

[makenzie71]

I try to check them, the weather channel, google, and a local weather station to get an idea (when I really, really care and it does seem as though I'm going to have start caring more often).  I generally just hit the local weather station (less than a mile from me) to see what they're reading.

[makenzie71]

6 minutes of run time.  It's not an exciting video, but it gives a good idea of how this turbine is running in 15~20 mph winds.

https://youtu.be/PuH0gOSlg-s

[kitestrings]

That's pretty respectable Mak.  I assume that is the blade noise in the background...sounds like it's spool up pretty fast.  Hopefully the periodic clang/bang noise is not related.

I'm not sure how long the wire run is, but with #10, if it is more than ~150', or if you should add another, you might want to increase size. Even at 400 watts that is probably putting your losses close to double digits.  Although... that added resistance may in fact be a benefit as discussed earlier.  Would be interest to see if it made a difference I guess.

[makenzie71]

It's roughly 45ft from stator to battery.  I thought it would be more than adequate but when i was setting it up the idea of a coming within spitting distance of 1kw was laughable.  I'm starting to prepare for two more of these things and the runs will be a little longer...about 50ft on one side and 75 on the other....if thus 900w business is a common occurrence i'll run it in 8g.

  The 500w one has a royghly 95ft run and it's in 12g so i try to consider it about 10% robbed.

The banging is a vent thst gets a klittle enthusiastic with a south wind

[SparWeb]

Mak,
This is pretty good for the size of turbine blades, for what you paid for it, and what you were expecting anyway.
I'd sure like to know what speed the blades are turning to figure out if they're still turning under-speed.  It tells you a lot to know the RPM exactly.

[makenzie71]

I don't have a way to measure rpm, but it's come up enough now that I suppose it's something I need to look into.

[makenzie71]

A laser tach isn't very expensive so I suppose that's an option, but all the ones I see on ebay only have a 15ft range.  I know in the spring I'll be pulling all of them down to paint poles and check them out, I can put the generators on a lathe then and measure up close.  I'll try to sort something out prior, I do see that information's convenience.

[margusten]

Hi makenzie71
I wonder how are You using this electricity You got from wind turbines?
Your grid tie inverter is connected to grid.
You must use this power at real time.
Or it just goes to electricity company.
Do You have electricity meter that counts both way ?

[makenzie71]

Hi makenzie71
I wonder how are You using this electricity You got from wind turbines?
Your grid tie inverter is connected to grid.
You must use this power at real time.
Or it just goes to electricity company.
Do You have electricity meter that counts both way ?

I'm using a grid tie inverter to dump it into the grid.

https://www.fieldlines.com/index.php/topic,150046.0.html

[makenzie71]

Update on tonight's little blow:

https://youtu.be/bVieuY2otak

[SparWeb]

Holy smokes it's really going.  I prefer a much more tame turbine!

[makenzie71]

yeah i'm impressed and pleased that it's managed to pull off that kind of output but i like standing by it a whole lot more when it's only kicking out 600-700 watts lol

[oneirondreamer]

A laser tach isn't very expensive so I suppose that's an option, but all the ones I see on ebay only have a 15ft range.  I know in the spring I'll be pulling all of them down to paint poles and check them out, I can put the generators on a lathe then and measure up close.  I'll try to sort something out prior, I do see that information's convenience.

you might be able to use a clamp on meter, pre rectifier, to measure frequency, and then use slow mo video at low wind speeds to relate freq to turbine speed.

[MagnetJuice]

I bought two of these digital tachometers to use with my VAWT's


I tested them powered with a small 9 VDC wallwart using 60 Ft. of wire.

They worked fine and seem to be very accurate.

Ed

[ToraKe30]

Hello, I want to buy the same Turbine, but in this kit there is no mounting Flange included.

Can you tell me pleas the diameter of bolt holes pleas...

Best regrads from Germany