Power curve for Hugh Piggott 8 & 12' turbine please

[dustydudeuk]

Hi All

I am trying to find a wind speed to watt power curve for the Hugh Piggott 8 & 12 foot turbine 24 & 48v. I have looked around the net & on the postings with no luck yet.

Can anyone help?

Thanks

Nathan

[wpowokal]

Nathan, I do not know of one, there are too many variables, however as I fly a 3m (10') duel rotor I will supply my figures.

Now my wind speed measuring is only at 6m (20'), this turbine is at 60', but due to the tower being slightly down hill it is equal to half height, oh yes depending on wind direction, bugger another variable, oh and my system is 24V.

So design calculations were 10A @ 203 Rpm @ 4,5 M/s.

20. A @ 230 RPM @ 5.2 m/s
    
30. A @ 244 RPM @ 5.5 m/s
    
40. A @ 264 RPM @ 6m/s
    
    

Now to date I have seen 50 amps give or take (1.25Kw). Wind speed is very variable so it is dificult to assign a wind speed to output, but suffice to say estimates were possibly on the mark or slightly under for given output.

Now commercial units come with power curve, I do not know how they are derived, perhaps a wind tunnel.

I don't know if any of this helps, but for what it's worth.

allan down under

[dustydudeuk]

Hi Allan

Thanks that great it gives me a more general idea of what to expect.

I am a newbie to this & only received my plans from Hugh yesterday. Now trying

to digest the info.

Thanks again

Nath

[Flux]

Producing power curves is a difficult and few people have the facilities to do this with any degree of accuracy.

I have some reasonable figures for Hugh's 4 ft machine but have never had the chance to test the bigger ones.

Allan's figures I suspect are rather skewed by the fact that the anemometer is not at the same height and in the same place. Small errors in measurement of wind speed result in drastic changes in power out.

Even with an anemometer just up wind of the machine and at rotor height it takes hundreds of readings at each wind speed to produce a reasonably reliable curve. Spot readings tend to be rather on the high side but you can get a rough idea this way on good days. With the anemometer more remote than a few rotor diameters up wind then you may be well of mark.

The better manufacturers curves are taken under reasonably reliable conditions and can usually be verified by other people. Some of the less trustworthy commercial manufactures produce figures that to put it mildly are optimistic and some figures published are well beyond the Betz limit and I really don't know how they are not challenged.

The best that I can offer you is some readings I took from an 8ft machine a few years ago. These were taken from chart recorder runs and averaged out by eye. I  now have better methods of taking data so don't take this too seriously. It was a poor wind site and only about 20 ft from the ground but with no obstructions to wind from the test direction.

The machine was not the same as hugh's machines so it is not a direct comparison.

12. mph   125W
    
15. mph   230W
    
16. mph   400W
    
22. mph   610W  
    
    

Winds above that were so infrequent that I couldn't produce more points.

Flux

[wpowokal]

Permit me some clarification, Flux is correct about the wind speed measurements.

Here in Australia and I suspect world wide, wind speed is measured at 30', therefore I tend to think of this as the prevailing wind speed.

My understanding is that when you double the height you basically double the wind speed.  I take this information from articals such as those here.....

http://www.homepower.com/magazine/downloads_wind_power.cfm

Therefore, my duel rotor is probally seeing double my recorded wind speed.  But as Flux stated it is dificult to quantify output verses wind speed for the majority of us.

Personally I am happy if amps are flowing, if I could re-classify wind speeds I would adopt the following scale...

1.  lifts skirts in the street
   
2.  hang onto your hat
   
3.  Tie the dog down
   
4.  Why am I walking backwards
   
   

Allan down under

[wdyasq]

Allan,

One has to also remember if your wind speed measurement is off the resulting power curve will be off the cube of the difference.  Examples are 9mph actually getting 10mph   is a 37% difference in power seen. That is only a 10% difference. 20% is damn near double in power.

Your "lifts skirts in the street" is an interesting classification.  It may have too many variables to actually plot depending on the length of the skirt, the type of skirt, the shape of the leg and maybe the type/color of under-pinnings. All bets are off for kilts (at least here).

Ron

[wpowokal]

Agreed Ron, it is for me, impossible to develope anything sientific, i'm happy to know that if the weather man predicts winds of x force I will probally get y amps into my batteries.

allan down under

[scoraigwind]

These figures look about right for an 8 foot machine with axial flux alternator.  It's

low compared to a commercial  wind turbine, but its accurate,especially in the low winds where it counts.

Doubling the tower height can produce 10 -30% increases in windspeed, but thse translate into 30-100% increases in available power.