Why Not Yaw Control??

[richhagen]

I don't mean to sound like I am critisizing you, I think it is great what you are working on.  I have watched your posts and enjoyed watching your projects (especially the blades).  I am glad you are here.  Certainly for some applications, there will be a benefit to your approach, and even your electronics.  I just disagree with some of the strategy.  To me, the more important goal is reliability and continuity of supply, these seem more important than upping the total energy harvest a bit.    

For grid tie, I think your strategy is fine, but for batteries, I still disagree.  If you have an 18MPH cut in, you will have days at a string sometimes with little to no power into your batteries.  Load scheduling is great, but sometimes life gets in the way.  It is easier to say than to apply, especially to disinterested power consumers one may share a dwelling with.  Since your storage is limited, the continuity of power becomes more important than the total harvest.  If one had large enough and perfect batteries, or diverse enough sources, then one would be better off to aim for the largest harvest, but larger batteries add cost, and most systems I have had the opportunity to observe, including the three small systems I have, do not have the storage capacity to benefit greatly from increased input, especially if it costs a fair percentage of the time that they would get something. I don't have the time vs. wind speed chart I would need to illustrate more clearly, but there are calm days when the wind speed is generally slow, with little gusts here and there, but probably never above 18mph.  Those days I would get nothing from wind.  If it was winter, I would get little to nothing from sun as well.  Now my small systems are mostly lighting, so there is not much load scheduling to be done there, but you would have similar continuous loads on a larger system as well as some heavy loads you can schedule.  My goal is up time, and getting a little extra heat during high winds, or long periods of sun does me little good, even in the winter when at least I can use the heat.  Keeping the RE lights on when there is little generation, that has more meaning to me.

"Perhaps, it's because people tend to distrust what they don't understand."

Yes this is probably true to some extent.  I like to be able to understand and repair most stuff I use.  I can't always do that, and sometimes it frustrates me.  The mechanical stuff probably is easier for me to visualize and grasp the concepts of, but I have had the opportunity to solder together a circuit or two, or run a servo controller or two as well.  Most furling systems are relatively simple force balances.  When one force, overpowers another the thing moves.  That really is pretty simple.  The electronics may work as well, be just as reliable in the end, and even offer some otherwise unavailable functions, but simpler or cheaper, probably not.  

Rich

   

[SamoaPower]

Rich,

I took no offence to your your first comment and if my reply reflected that, I apologize. Divergent views are what this board is all about in my estimation.

Apparently I didn't make my explanation of a high cut-in alternator very clear. Using Flux's scheme doesn't give up anything at the low end. That's the function of the boost converter. It takes what ever voltage is available below cut-in and raises it to battery charging level. Other than a slight loss due to efficiency, it will recover all the available energy at the lower speeds. In fact, it will probably do better than your standard alternator with a 10 mph cut-in.

"The electronics may work as well, be just as reliable in the end, and even offer some otherwise unavailable functions, but simpler or cheaper, probably not."

Agreed

[hvirtane]

I think that a yaw control for a downwind

machine would be good. I think that a furling

system would be needed as well.

My idea for a simple mechanical system

for 5 kW - 20 kW machines:

What do you think?

- Hannu

[Ungrounded Lightning Rod]

I'd skip the tail and move the pivot farther above the turbine axis, letting the blade drag do all the work, unless you can get a better power vs. windspeed curve with the tail present.

You don't need it to stop when it's furled - just run below the speed where it would take damage.  In fact you'd prefer to keep it spinning at some sane speed.

[Murlin]

Yaw control sure is appealing. As long as you have spare parts around, it will be pretty easy to repair.

I have used to have a machine that was made in 1945.  It was a Cincinatti Hydrotel duplicating machine.  Put in some oil, turn it on and it has been running for what?  60 years....

I also bought some CNC machines that were made back in the 80's.  They broke down all the time and gave me fits......cost thousands of dollars to keep them going....

But have a 5 gal can of oil,  and the old clunker kept right on chugging......dependable as heck.....

Consider this.  

The wind does point the thing in the right direction for free and without any help.

It seems that is half of the Yaw control.

The problem is:

1. :  Furl control.
   
2. : Rotor speed control.
   
   

Furling can be done with a motor, nut, and screw, a hydraulic cylinder and the mechanical ways.  Pretty simple for an on/off application.

Rotor control is where it gets tricky.

I had this wild Idea.  Why not just "give it something else to do"...

It occurred to me, you could bring a shaft of the opposite end of the drive axis and drive a hydraulic pump. There are several ways you could use this.   You could design a hydraulic servo spool to where the faster the pump turned, the more pressure it would put on the spool and start adjusting the check valve pressure.

At the slow speeds, the bypass would flow easily across the check valve and not rob much energy. The return line would be very wide.  As the RPM gets close to max, the pressure at the check valve starts to increase exponentially and you could then turn on a motor to furl it in.  Or, if you used a hydraulic cylinder to furl with, it is quite possible to be able to adjust everything down to the nat.

Once it was still fully furled and still making power, the pump could start to rob the kinetic energy from the rotor.  Kind of like a brake with no surface friction.

All the friction would be in the oil and easily cooled with a radiator.

More weight?  I dunno, it could be very compact and not really add that much weight at all.

Anyways....just a crazy Idea.....I got to thinking about the way the Cincinatti Hydrotel was built and said hrmmmmmmmm.....

Murlin

[SamoaPower]

Murlin,

Looks like you've had your thinking cap on again. Great!

"The wind does point the thing in the right direction for free and without any help.

It seems that is half of the Yaw control.

The problem is:

:  Furl control.

: Rotor speed control."

It seems that, perhaps, you're missing one of the main points about yaw control. Maybe I should have phrased it 'controlled yaw'. The main problem is uncontrolled (high) yaw / rate / which is what causes component stress when left to the whim of the wind. Some try to control it with intentional friction in the yaw bearing (pipe on pipe) but it's only effective over a narrow range of input. The seeking force of a given air rotor is difficult to accurately define, as pointed out by Flux, as is the extent of turbulent wind azimuth rate-of-change. I suspect that the usual, free-hinged tail vane actually makes the problem worse but have no data to actually prove it (lots of ill-defined variables).

What we really want is to take the control of yaw rate away from the wind and other mechanics. This is what I proposed.

The points you ascribe to 'the problem is' are actually separate from controlled yaw. In my opinion, they are both most effectively addressed by servo active pitch control. Your idea of hydraulic loss control is okay but why generate heat to be dissipated when you don't have to produce it in the first place?

Active pitch control can maintain a given TSR, can maintain a given RPM, can limit RPM to a value, can maximize RPM, and/or can feather (furl) at a defined RPM/wind speed or all of the above. What more do you need?

[hvirtane]

I'd skip the tail and

move the pivot farther

above the turbine axis,

letting the blade drag

do all the work

That is probably good. Less parts.

And mechanically more sound.

I've seen that the yaw control with

a side vane and worm gear can do a good job.

Using that kind of system you

can easily use a two blade prop.

But some kind of furling is needed.

I know that Danes already a long

time ago made the conclusion

that only pitch controls or

stalling controls with fixed

pitch work with bigger machines,

but I don't know if they

tried furling up.

- Hannu

[hvirtane]

Once it was still fully furled

and still making power,

the pump could start to rob

the kinetic energy from the rotor.

Kind of like a brake with no surface friction.

All the friction would be

in the oil and easily cooled with a radiator.

I think that this is a really workable idea.

I don't like much systems to turn

the wind rotor away from the wind,

because of the gyroscopic forces.

On the other hand all the pitch

control systems I've seen are

a bit costly and complex.

Stall control systems with

an oversized generator

might work, but we would

be dependent on electrics,

which might fail, just when needed

and there is no way to use

such a big generator that it

could stall the wind rotor

with all the possible conditions...

Stall control with air or

oil friction... I like the idea.

- Hannu

[Murlin]

Ah yes... point well taken,  sorry meh inexperience is showing off again

So the whole unit whips around like crazy. But with a controlled furl, wouldn't it would just spin on its yaw axis and the tail feathers would not be freely hinged and could not slap the unit around.

The violent movements would be just a fast spin, without having the tail picking it up and dropping it all the time.

Just my 02.  

But I also see where you are coming from.  You could just keep rotating until the blades stalled just enough to still produce max power. Since there will be no tail feathers to hit, you could also just keep going and stop the mill all together.

That would  be the ultimate......

[hvirtane]

we would be dependent on electrics,

which might fail, just when needed

I agree that it is possible to make

as reliable electronical control

systems as mechanical systems are.

But those systems don't seem to

be existing yet.

If you'll look at any data concerning

problems of modern cars stopping

on the road because of failures,

you'll see that the most

common problems are with the electricity

systems. With the car industry they

are certainly trying to make

reliable electronic systems,

but they haven't been very

successful, yet. Millions and

millions of cars are produced every

year, but still their electrical

systems are unreliable.

- Hannu

[SamoaPower]

"But with a controlled furl, wouldn't it would just spin on its yaw axis and the tail feathers would not be freely hinged and could not slap the unit around."

No, not at all. The machine is locked to a geared motor in yaw. No spinning is allowed except by yaw motor control which only rotates at about one RPM. Also, NO tail feathers are necessary at all.