VAWT: solidity. is there anyone that can say anything about it?

[brandnewb]

We all have heard and read the countless of reports. Also regarding Solidity.

What we need as a community is a simple guideline.

I for one am not looking for an optimal efficiency or setting new world records.
I care about how can people like me simply recreate my work.

So earlier, After far tooooo much effort on my part, I settled on 20cm chord length in a 3 blade VAWT turbine spanning 2m diam x 3m height

now I am constructing the same turbine yet I am doubling the diameter.

What quick formula is there to scale the chord length of the blades? Remember please we are not looking for super optimal we are looking for something that works and is easy to adapt by anyone.

[MattM]

Unless you included twist, strain, and elasticity... you probably already did.

[brandnewb]

I am very sad that there is no fast and loose formula for deciding the chord length depending on the radius of a VAWT.

This is an example of what contributes to the bad reputation the field has, at least for me.

Anyway since it took me ages to settle on 20cm chord length (Lc) on a 200cm turbine diam (Dt), I am introducing the following formula

if (Dt > 1000mm) {
   Lc = Dt / 10
} else {
  Lc = 100mm
}

So this means a chord length of 40cm for a turbine with a 4m diam.

It just feels more intuitive that way.

Really believe this field needs to become less complicated in order for everyone to be able to construct turbines and aid in our carbon goals and energy independence.

[topspeed]

I am very sad that there is no fast and loose formula for deciding the chord length depending on the radius of a VAWT.

This is an example of what contributes to the bad reputation the field has, at least for me.

Anyway since it took me ages to settle on 20cm chord length (Lc) on a 200cm turbine diam (Dt), I am introducing the following formula

if (Dt > 1000mm) {
   Lc = Dt / 10
} else {
  Lc = 100mm
}

So this means a chord length of 40cm for a turbine with a 4m diam.

It just feels more intuitive that way.

Really believe this field needs to become less complicated in order for everyone to be able to construct turbines and aid in our carbon goals and energy independence.

Solidity varies from .15 - 0.5 in various designs.

It depends on what kinda record you are after.

[brandnewb]

Thank you topspeed for pitching in.

Could you please elaborate a bit on what you meant with
"It depends on what kinda record you are after."

[topspeed]

Easy starting... top rpm...huge efficiency ?

[brandnewb]

easy starting is for my scenario the only player in town. The referee is safety.

I am open to any and all suggestions. But please understand that since my progress on this bird is well underway I might not be able to implement all suggestions (that are likely to work for this project) at this stage.

However. Great suggestions might likely be a part of the next cycle.

The cycle being. Set the Apache up. See the bird spin. Record what she is producing. Inspect her for signs of hurt. take her down (in a controlled manner mind you haha ), Do upgrades.

and the cycle repeats.

Now if ever this beast can become both producing enough to get by with and be rock solid that one does not need to worry.
Then it will be time for the structural engineers amongst us to calculate how to keep this bird from flying off while mounted on a roof.
I for one am sooo not capable of that ;(

[Bruce S]

Have a look at some of Windstuffnow's posts about roof mounting and or connecting a Turbine to a building. Ed Lenz did it just so he could give a real world account of what it does

There some very early discussions about why NOT to do this, and posts from people who did anyway and the results.

Bruce S

[Mary B]

Having an antenna tower connected to the west wall of m house is loud enough in high winds when it starts vibrating! And moaning... and howling if an antenna is turned just right to get wind across an open boom end... all transmitted into the house...

[brandnewb]

so I am getting the impression that the general advice is to not do it? ;(

You see the thing is that you guys have so much more experience and there for can take into account a regular roof.
I do not even believe it makes a difference if the build style is American or European.

All I have as a reference is the roof that I have. I have chosen a steel frame structure for it's ease in designing and for the availability of structural engineers that are able to convince the municipality that the design is sound. I for one can not do structural calculations.
This all leads to that I have a roof that one can put 10 elephants on. maybe even an Apache while in service.

But if the average of roofs are not built to handle high loads then it is not looking great for possible wider adoption of the bird on roofs.

[Bruce S]

It's not just the structural loads Mary B is talking it's the transmission of the vibrations stemming from the Mast, the mill and once you get a genset on it, even the frequencies and sub-harmonics involved.

Think of like what Tesla did with his free running oscillator!! on the building he lived in, 'bout brought it down once everything go into sync with the harmonics. Not to mention driving the people bonkers!

Bruce 

[Mary B]

It's not just the structural loads Mary B is talking it's the transmission of the vibrations stemming from the Mast, the mill and once you get a genset on it, even the frequencies and sub-harmonics involved.

Think of like what Tesla did with his free running oscillator!! on the building he lived in, 'bout brought it down once everything go into sync with the harmonics. Not to mention driving the people bonkers!

Bruce

BINGO! The noise will drive you nuts... only a 3mph east wind right now but one of the antennas is at resonance and vibrating making a racket... I can hear the aluminum rattling in the house...

[brandnewb]

ok guys I am pretty sure you are correct.

Yet I am going out on a limb here and make a bold claim.

The Phoenix is silent so far. Let me follow up on this when it has spun during more brutal conditions
{1} I meant with minimal vibrations that can be dampened by a thick rubber layer between the roof and a yet to be calculated base{1}

[Mary B]

ok guys I am pretty sure you are correct.

Yet I am going out on a limb here and make a bold claim.

The Phoenix is silent so far. Let me follow up on this when it has spun during more brutal conditions
{1} I meant with minimal vibrations that can be dampened by a thick rubber layer between the roof and a yet to be calculated base{1}

No matter what you need a solid bolt going into the roof structure... just because you can't hear doesn't mean it is silent... subsonics will set you on edge after awhile!

[brandnewb]

I stand corrected gang!. Wind turbines are easy to get vibrating. If a turbine is not vibrating at the very moment it is being inspected says nothing about the likeliness it will vibrate.

I will admit having to eat all my words here regarding vibrations ;(

I still stand by that it would be great if there would be a fast and loose formula for solidity