20 foot diameter turbine - is there more information?

[altenergy]

I read through the pages that documented the 20 foot diameter wind turbine build on otherpower.com but can't seem to get additional information on it. I've emailed otherpower but have not received a response back. Does anyone know what the status of this turbine is? Did it produce the power they thought it would? Does anyone have a power out vs wind speed graph or data? Did it have issues and was not persued because of problems? Has or is anyone building a design similar to it? If so any information you would be willing to share would be greatly appreciated. Regards, altenergy

[freejuice]

Hi Alt,
 Maybe DanB will chime in here, he has one up and running. I think he mentions there was a bit of a stall problem but it nevertheless made good power.
 I think a few others on this forum have made them too.
Somewhere...someone, (if my memory serves me right) mentioned that they could almost get the same amout of power out of a 17 footer on a good wind site as they could out of a 20 footer.

I have a 17 footer and I can say they can produce some good useable power...on a good wind day ...say about 10-15 mph its not very long before I have the batteries topped off and I'm  burning the excess off as wasted heat through resistors. ( groan I should be dumping this into a water heater element)

[fabricator]

Dave Brugge has extensive experience with 20 foot turbines.

[Dave B]

Dave Brugge has extensive experience with 20 foot turbines.

Hello there,

  Thanks for the plug, Dave B. here. I have not built duplicate 20' machines of the Dan's design so as far as any data, comments or suggetions on that plan I cannot offer much help. I have built several 20' and using the different blade profile creates a whole new set of design parameters. Believe me when I say that it has taken a huge number of hours to get a handle on how everything works together with a machine of this size. Application also is a big design factor and of course the biggest challange is keeping things under control. Swept area this size after say 20 MPH means thousands of watts increase in output for just a few MPH increase in wind speed. The numbers don't lie and if your 20' machine or larger is not highly underated and greatly overbuilt it will be destroyed, period. Take a real good look at the power curves before building. It's only a matter of time before the big winds come, it's too bad that from destruction is when we usually learn the most.

  Dave B.   

 

[Volvo farmer]

Hi Alt,
 Maybe DanB will chime in here, he has one up and running. I think he mentions there was a bit of a stall problem feature but it nevertheless made good power.
 

FTFY 

[DanB]

I've made two so far...  my first one has been documented to some degree here:  http://otherpower.com/20page1.html

It worked well for the first 9 months or so and produced lots of energy - in fact I never turned it off except to just show that 'it could be turned off' even on windy days when gusts were exceeding 80mph.  Then we got an extreme wind event, with gusts (nearby anyhow) exceeding 100 mph and the blades struck the tower.

So I repaired it and ran it again for a while - blades struck the tower again.

About a year and a half ago I took the blades off (to use on another machine) and replaced them with some blades off an old Jacobs machine (I cut them down to 20').  These blades behave well, but they're somewhat narrower and they do tend to stall in higher winds.  Since then I've pretty much not turned it off though and it's still producing plenty more energy than I usually need - so i probably will not fit wider blades to it again.

The other one has also been well behaved - it's been up for a year and a half now with no problems.  However - as I said originally, to do it over again...  I would use a larger bearing if possible.  I would also improve the yaw bearing/yaw spindle setup - mine has shown significant wear over the last 4.5 years.  A machine this big... many would say - should have some sort of mechanical shutdown.  I have no problem shutting down by shorting the alternator - even 1 phase shorted will shut it down in any wind that I've experienced and it will not startup, however, it two wires broke it'd be a mess.

Overall though -  the two I have made have served well.  Both machines are in the mountains - it is turbulent, I cannot say how they might behave somewhere that got high, sustained winds (we don't see that much around here - we turbulent wind and extreme gusty conditions sometimes).

[mikeacs]

Another 4 years have gone by since the last post from DanB about the 20 foot turbine.  Besides the the notes above about larger bearing, better yaw bearing, and narrower blades - is there any other improvements that you would do? 

Would a degree or two of more tilt keep the blades from hitting the tower?  Would the blades be better if they were about 10" at the widest point?

Thanks,
Mike

[MattM]

I really think aerofoils are the biggest issue with blade bend.  As the blade goes around the aerofoil shape creates lift in the wrong direction, back towards the tower.  The blade also twists front edge down.  An S-shape design on the backside would basically use supercritical airflow under it to support the force of the air pushing it from above.  It would also help keep the front edge from twisting down.

[Dave B]

If anyone is interested in building a 20' axial please check out the classifieds here first. http://www.fieldlines.com/index.php/topic,148700.0.html  I am accepting offers on these 2 complete systems and or will divide the equipment as well. My contact information is on the ad. Anyone familiar with the investment of materials alone will understand these systems are a great value. Thanks, Dave B

[mikeacs]

I really think aerofoils are the biggest issue with blade bend.  As the blade goes around the aerofoil shape creates lift in the wrong direction, back towards the tower.  The blade also twists front edge down.  An S-shape design on the backside would basically use supercritical airflow under it to support the force of the air pushing it from above.  It would also help keep the front edge from twisting down.

Is there a link or article that you could recommend to follow the blade design you are talking about?  I'm fine with scaling it up or down.

The used turbines and towers are a great deal!  If I wasn't a "want to do everything myself" type of person, I jump at the chance.

[MattM]

What I am suggesting is using the leading edge influenced by the airflow perpendicular to the wind to push the blade back towards the source of the wind.  Conventional shaping takes this perpendicular airflow to actually increase the bend of the blade.  Think of the conventional wing at a high angle of attack, the airflow goes mostly under the wing and the overwing airflow-generated lift becomes negligible above to a certain point under the stall speed.  In a conventional civilian aircraft flying at stall angle is extremely dangerous due to inability to get thrust necessary for recovery.  Modern jets are pushing twice the angle of attack of previous fighters due to careful balance of forces of airflow and airspeed, because lift can be generated both airflow above or below wing.  The advantage fighters have over civilian aircraft is the gobs of thrust the former enjoys.  The wind turbine at its maximum wind ratings is suffering from excess forward speed rather than lacking.  By treating the leading edge as a high angle wing, you lift away from the support pole.