Honeywell turbine

[fabricator]

I had a chance to get up close and personal with a Honeywell turbine today, it's essentially a 6 foot diameter rotor axial flux machine, they claim it makes cut in at 2mph.

[Frank S]

Fab are you sure it is axial flux? From what I have been looking at it would make more sense for the  design to be radial flux

[fabricator]

Yeah I guess it is radial, there is a "smart box" on it that three wires come out of and go to the inverter, the speed of the outer rim would basically give you the benefit of a geared machine, on a six foot diameter wheel you could get one hell of a bunch of magnets and copper, but apparently they don't because it only weighs 178 pounds.
Thats a 226 inch circumference, room for a lot of magnets and coils.

[Frank S]

A while back I drew up a design of a large diameter radial that was about 52 inches dia between the magnets and coils I had the coils on an inner stater and the magnets on the rotor 108 magnets and 81 coils wiring would be fun though I could go 27 in series with the coils having 200 turns of # 16 or paralel all of them with 5000 turns of # 26 Just think of the wild combinations and voltages that could be produced with a Huge Torque master 20 ft diameter 18 blade fan in 30 MPH winds figuring that would translate to an approximation of 314 Sq ft of area with .007 hp @ 10 MPH  @ 30 MPH it would be about .224 hp sq ft = 70.336 hp @30% =21.1 hp @40% it could make 28 HP @ 60 RPM. a 40 MPH wind will produce 64 times the power of a 10 MPH wind or there a bouts.
 A wild design I'll admit but the way I was figuring it no Turbine could even start to compete with a fan using a generator made like that

[damian]

I don't know a whole lot about wind, which is why I ask this, but I seem to remember reading that rotor efficiency is inversely proportional to rotor torque?

[tecker]

here's the owners manual  . On page 4 there's a slight view of the stator . It may well be an axle . The blade ratio is inverted but the torque would increase the power out .
Like turning a big steering wheel is got some low turning power  power .

[fabricator]

True, with the traditional axial design with the generator in the center you need less blades for more speed to make power, but with this design with the generator on the outer diameter the speed loss from more blades doesn't hurt performance because of the increased speed at the outer diameter.

[gww]

I wonder how jay leno likes his after its been there awile? 
gww

[tecker]

Wooops here's the manual
http://www.teswind.com/docs/Wind-Turbine-Owners-Manual.pdf
There's a nice little nrel map on  page 9
all covered on http://www.nrel.gov/analysis/

[bob g]

the way i see it is this design is a waste of time and money

reasons being

yes the large fan will make lots of torque, but the rpm is very low relative to 3 blade lift type machines.

it takes a combination of rpm and torque to make power, just because you have lots of torque does not mean you will make lots of power especially when the rpm is so low under load.

the alternator design is interesting,  but again it cannot make anymore power that what is available to drive it.

my bet is the unit in question will never see 500 watts maximum output in anything less than very high wind conditions. the cutin of 2 mph might equate to enough power to light a few led's but it surely is not going to make any real power or charge anything more than perhaps a cellphone battery.

also my bet is the honeywell product will not make 1 hp in a 28mph wind, that being a clean non turbulent 28mph wind, something  you are not going to get mounted to a roof of a house.

as far as i am concerned these are one of the biggest jokes on the market right now. people will buy them expecting them to do something to reduce there power bill and my bet is they will see little or no difference in their bill over time.

huge waste of time and money in my opinion

bob g

[Mary B]

If I remember right NorthernTool was selling these for $10k+

[CaptainPatent]

the speed of the outer rim would basically give you the benefit of a geared machine, on a six foot diameter wheel you could get one hell of a bunch of magnets and copper, but apparently they don't because it only weighs 178 pounds.

The problem is they can't pack in copper and mags. At the outer circumference, the electromagnetic force fighing back against the torque caused by the wind is also at its peak, so it creates a huge angular force to fight back against the increased torque. I guarantee if they increased the copper much more, the thing wouldn't spin at all.

Add in the fact that the bracketing and quantity of mags and copper must be the full rotational diamater of outside of the blades and you add tons to the cost of the overall machine. Sure, you'll be able to reduce the size of mags and diamater of copper some, but it'll still cost more than an appropriately compact rotor / stator mounting.

The ONLY situation I can see this setup being beneficial is one where you wanted something crazy strange like 12 phase power (and I can't even fathom why you'd need something like that) and the minimum copper ring was a huge diamater.

[ghurd]

The ONLY situation I can see this setup being beneficial is one where you wanted something crazy strange like 12 phase power (and I can't even fathom why you'd need something like that) and the minimum copper ring was a huge diamater.

12 phase?
Maybe 11 or 13, but not 12.

[ChrisOlson]

12 phase?
Maybe 11 or 13, but not 12.

ROTFLMAO!

but with this design with the generator on the outer diameter the speed loss from more blades doesn't hurt performance because of the increased speed at the outer diameter.

The increased speed at the outer diameter doesn't make any difference.  You can have a 16 pole generator and it don't make one bit of difference if it's 30" in diameter or 10" in diameter.  It will make the same voltage with the same copper and magnets at the same rpm.  The only advantage to the larger diameter is being able to fit more poles and copper in it (and 11 or 13 phases, but not 12).  LOL!
--
Chris

[bob g]

Chris,
"The increased speed at the outer diameter doesn't make any difference.  You can have a 16 pole generator and it don't make one bit of difference if it's 30" in diameter or 10" in diameter.  It will make the same voltage with the same copper and magnets at the same rpm.  The only advantage to the larger diameter is being able to fit more poles and copper in it"

not at all sure i agree with this statement

from what i recall there are at least three factors in design that determine voltage,

number of poles
length of wire in the flux path, and
what i refer  to as "rim" speed.

a 10" rotor at 100rpm will have a rim speed of about 3141 inch/min
while a 20" rotor at 100rpm will have a rim speed of 6283 inch/min

everything else being equal, the larger diameter machine will develop proportionally higher voltage than a smaller diameter machine.

am i wrong?

bob g

[ChrisOlson]

everything else being equal, the larger diameter machine will develop proportionally higher voltage than a smaller diameter machine.

am i wrong?

Yes bob, you are wrong.  The voltage you will get from a particular setup is determined by number of poles x revolutions per second x field strength (tesla) x the field area of one pole x .000645.  It has absolutely NOTHING to do with "rim speed".
--
Chris

[bob g]

Chris

i respectfully disagree

if this was the case your gear drive to increase rim speed would have no effect on voltage

rim speed does have a part to play in generator design.

many years ago, mick sangrillo wrote a paper for homepower magazine outlining the three considerations of alternator design

for a given design, increasing the length of wire in the flux path, increasing the number of poles or increasing rim speed all will increase voltage generated.

one of the easiest ways to increase rim speed is to increase the diameter of the rotor/stator assembly.

i don't follow your reasoning, perhaps you could explain?

bob g

[ChrisOlson]

i don't follow your reasoning, perhaps you could explain?

It's not my reasoning.  It's basic generator design 101.  For a given number of poles, diameter does not do a single thing to voltage when you change the diameter of the rotor.  Only rotational speed changes it  The formula is above.  Don't argue with me - you'll have to argue with Nikola Tesla.  He's the one that thought it up.  That formula has been in use since the first man figured out how the first generator ever built works.
--
Chris

[bob g]

Chris

what you are stating is fine, provided you are explaining what is happening for a given machine diameter, however when  you are looking at machine design with a clean sheet of paper you cannot negate diameter from the equation.

the reason being...

the larger diameter will effectively provide a faster rim speed, which in reality is the same thing as increasing rpm of a smaller machine.

in other words,  for a given machine increasing rpm will increase the voltage generated, if all else remains the same. increasing rpm increases rim speed.

increasing diameter has the effect of increasing rim speed without the need for increasing rpm.

generally speaking the increase in diameter allows for an increase in the pole count (easier to fit) and an increase in the amount of copper (also easier to fit)  however you cannot negate the effective increase in rim speed for a given rpm.

bob g

[southpaw]

The way I understand it. Doubling the rpm Raises the voltage by effectively doubling the poles/ time period. Doubling the diameter with the same number of poles just makes it bigger. There might be an advantage to slower rotation/ rim speed, less wear, better wave form, or lower frequency, but I think it will be small.

[fabricator]

I don't now why you would use the number of poles and coils on a 13" machine on a 70" machine, it only stands to reason you would add coils and magnets, with more flux cutting more copper at a higher rpm you have to make more power.

[ChrisOlson]

the larger diameter will effectively provide a faster rim speed, which in reality is the same thing as increasing rpm of a smaller machine.

No, it doesn't bob.  With a given number of poles and coils frequency stays the same and voltage generated does not increase with an increase in diameter.  You need to increase rpm to get a rise in voltage.  If you don't believe me, I invite you to try it.

The advantages with my geared axial generators is that I can use less poles and get the same frequency as a larger diameter generator by using higher speed.  And because I use less poles the cost of the unit is cheaper (less magnets and steel in it).  I can use windings with less turns (lower resistance) and get the same voltage as a much slower turning larger generator with more poles and coils.  And the torque loading on the stator is way less with the smaller diameter (in proportion to the gear ratio), allowing me to generate incredible amounts of power in a small compact size without stressing generator components.

I get 3 kW continuous out of a little 12" diameter generator with ferrite magnets in it, and only .5 ohm winding resistance  by running it at 1,500 rpm and 120 volts.  It takes a 20 pole 20" diameter direct drive, with bigger and more expensive neo magnets, to match it for continuous output capacity.  The Otherpower 16 pole for their 12 footer can match it intermittent on very short spikes, but not continuous.  It takes a damn big direct drive axial generator to do what it can do, without burning up.

It has nothing to do with diameter, dude.
--
Chris

[bob g]

Chris

lets take a look at the lundel alternator typical of automotive applications
the little car alternators typically have a 12pole rotor

the larger truck alternators also have a 12 pole typically, although there are other pole counts as there are in car alternators

the larger diameter truck alternator such as the leece neville jb series
typically have a quite low cut in rpm, about 33% lower than the car alternator. this is due mainly to the larger diameter rotor allowing for a higher speed in ft/min of the rotor over the smaller counterpart.

i went back and dug out some of my alternator/generator design books and found this.

Pi= total flux * total amp-conductors * rev. per sec / 10^8

which is what i think your formula basically expresses, however i haven't looked at it thoroughly.

however we can express the power formula using this

Pi= (% * pi^2 * d^2 * L * B * K / 10^8 ) * S/60

where
 % = percent of armature core covered by pole faces
L= length of armature core
B= average magnetic density in the air gap
S = rpm
d= diameter of armature (stator in our case)

"the electrical power developed within the armature(stator) is now expressed in terms of the poles, the dimensions of  the core, the magnetic density, of an electrical unit of activity(see note), and of speed. Since the electromotive force, current, number of poles , number of face conductors, and the number of paths do not enter into the equation, the output of an armature/stator, measured in watts, may be calculated independently of the variations of these quantities"

*quote from
 "design of electric machines"
  by s.h. mortensen and robert mcCrae wilson
  1927

and this

"an electromotive force of 1 volt is generated in a conductor when it is cutting magnetic lines at the rate of one hundred million per second"

end quote

at a given rpm the larger the diameter of the rotor, the faster the the lines of force per second passes a conductor. the faster they pass, equates to more "effective" lines of force per unit of time.

from this i will still conclude this, all other things being equal, the larger diameter machine, the higher effective voltage, at a given rpm.

i think i will stand with this until a better explanation comes forth.

bob g

 

[ChrisOlson]

I'm very sorry bob, but you need to go back to square one.  The rotational speed of the rotors and the number of magnetic lines per pole fix the magnitude of the voltage generated in a coil.  The more poles there are, the more lines of magnetic force.  This also means that the more poles there are, the lower the rpm required to produce the same amount of power at the same frequency.  Diameter does not enter into the equation.

As a newbie I thought the same thing as you.  You're only going to learn by trying it like I did.  It's a simple test.  Build yourself a simple two pole, two coil single phase axial generator using plywood discs for the rotors and make it so you can move the coils in and out to accommodate different diameters.  Spin it at a fixed rpm and measure the voltage at like 8" diameter vs 15" diameter.  You will get the same voltage.  Guaranteed.

Then you can sit down, drink some beer and scratch your head for awhile, and come to the conclusion I came to way back when - you may as well cram poles and coils into the smallest diameter possible and spin it as fast as you can instead of building big, heavy monstrosities that cost more money to build and don't make any more power.
--
Chris

[CraigM]

Chris,

So if I understand this correctly….

The key words here seem to be “all else being equal”. If I have a typical 9 coil, 12 pole machine that's 10 inches in diameter or a 9 coil, 12 pole machine that's 10 foot in diameter they both have the same number of coils and poles.

If I rotate the 10 inch or 10 foot machine one revolution there are 12 N-S pole changes per revolution and both see the same frequency. The only difference will be in the speed the magnet is passing over the coil will be greater on the larger diameter machine.

I understand that part of Faraday's law is that EMF is induced by the frequency or number of changes of N-S poles over a given time period and not by the speed of the magnet passing over a coil. This is why higher rpm gives higher output, not from the speed of magnet over coil but from the increased frequency of N-S pole changes.

If this is true and “all else being equal” the 10 inch diameter 9/12 machine will have the same output as a 10 foot diameter 9/12 machine that are traveling at the same rpm.

Am I in the ballpark?

Thanks,
Craig

[ChrisOlson]

I understand that part of Faraday's law is that EMF is induced by the frequency or number of changes of N-S poles over a given time period and not by the speed of the magnet passing over a coil.

Craig, exactly.  It's the change and frequency that induces the voltage and current.  Not the linear speed.  Back when I was still wet behind the ears I remember discussing this with Ed Lenz and he had to set me straight.  Now it's my turn.
--
Chris

[Flux]

Frequency doesn't change with diameter, it depends on number of poles and rotational speed.

The only thing a larger diameter can do to help you is to give more space for more poles ( increase frequency) or for larger poles ( more flux) with the same frequency.

The speed that matters is angular velocity and that doesn't change with diameter.  Forget that stupd equation that states that volts = Blv.  Go back to thinking about flux linkage.

If you use a large diameter it stands to reason that you have a lot of space for a lot of magnet and copper but the material needed increases vastly as you drop the rotational speed so whatever you do for a given output a very low rpm alternator turns out to be a monster.

Flux

[fabricator]

What if you have a 72" diameter 45/48 machine and an 10" dia 9/12 machine? Just asking stupid questions man because this is like Japanese arithmetic to me.

[Flux]

Basically for a given space you can get so many magnets of a certain size in. Within reason the output stays the same regardless of the number of poles. You could use 4 large poles or 12 little ones, the frequency would be very different but when rectified the output would be similar.

If you had those 12 magnets on a 10" diameter and then mounted them on a 72" diameter the flux per pole ( magnet ) would stay the same and for the same rotational speed the frequency would stay the same. It would probably have a very strange waveform and the step is really too big for sensible working but the idea still holds and output is similar.

At 72" you can fit a lot more of the same size magnet or you could use fewer much bigger magnets, either way you get more output as you are increasing the total flux. ( more flux per pole or more poles with the same flux).

The increase comes at great cost in terms of magnet and copper. using faster blades or a transmission would let your little 10" machine do the same job with a tiny fraction of the magnet and copper.

This is always a problem with wind machines, the larger the prop the lower the rotational speed and the larger the power it can produce. You then have a problem of making a more powerful alternator to deal with the lower speed or use a speed increasing transmission.  The most sensible starting point is with the fastest blades you can reasonably use. If you use 3 blades at tsr 6 you have a very big head start on something like a wind pump rotor with tsr 1 or less. To deal with the low speed rotor you need a speed increasing transmission with a step up of 6:1 to even get back to the same starting point.

To do this by using a huge amount of copper and magnet is possible but can hardly be cost effective and you end up with a very heavy machine. It may work with this little baby honeywell thing but the prospects of taking this approach to large machines is not very attractive, it has been done but apart from cost and weight there are serious mechanical problems to overcome with an alternator mounted outside the blades.

There can be confusion when comparing wind alternators with engine driven ones. With wind we use raw ac but most engine driven generators are confined to a fixed frequency 60Hz in N America and 50Hz most other places. This constraint forces low speed alternators to have a large number of poles and hence a large diameter.  This gives a situation where high speed alternators are long and small diameter ( power station turbo alternators) while waterwheel alternators are large diameter and very short.

Flux

[ChrisOlson]

The increase comes at great cost in terms of magnet and copper. using faster blades or a transmission would let your little 10" machine do the same job with a tiny fraction of the magnet and copper.

An engineer at Vestas in Denmark told me a few years back (Re: utility scale turbines):

......eventually the folly of direct drive generator designs in wind turbines will be become evident.  It is inefficient and you are wasting available wind power by using it unless you throw huge amounts of materials at the problem, which then becomes ineffective due to cost, size and weight.

--
Chris

[bob g]

please note the following

i never stated it was desirable to go to larger diameter, nor did i state it would be more efficient to do so, all i am saying is the larger the diameter the faster the rim speed for a given rpm.

if you take a test pole, (similar to a briggs and stratton ignition magneto
and test its output at the same rpm but with a small diameter rotor vs a large diameter rotor, and i will guarantee the test with the larger diameter will produce a higher voltage.

the reason goes back to the formula for what it takes to make a volt, it is the number of magnetic lines cut per sec, if you cut the lines faster the effective lines per second is higher,  the higher this number the higher the voltage produced.

we can test this effect using an alternator with using the same excitation, and two different rotational speeds, (which mimic's an increase/decrease in rim speed without having to change diameters) the higher rotational speed with produce a higher voltage with the same excitation, same pole count, same stator windings, same flux density, etc.

now it is fair to state that  this doesn't account for changes in pole design of a larger diameter machine for a give pole count, but it will demonstrate that there will be an increase in voltage.

perhaps i am not presenting this clearly.

let me do a bit more digging,

i have about 2 dozen books on alternator/generator design, and i know there is some text that better illustrates what i am trying to get across.

again, please note,
i am not saying a larger diameter machine is better or worse than any other design
i am not stating that one would want to keep the same pole count, increase or decrease it over a smaller machine.
i am not stating it would increase efficiency, or
anything other than

we cannot state categorically that an increase in diameter will have no effect on voltage generated for a given rpm, or we cannot neglect or dismiss this phenomena.

bob g

 

[ChrisOlson]

the reason goes back to the formula for what it takes to make a volt, it is the number of magnetic lines cut per sec, if you cut the lines faster the effective lines per second is higher,  the higher this number the higher the voltage produced.

I think you perhaps misunderstand how this works, bob.  It has nothing to do with cutting magnetic lines.  It has do to with flux linkage and the change and frequency is the determining factor.  Not linear speed of the pole.

Flux already explained it pretty well, so no sense to going over it again.  I would suggest at this point that you gather up some materials and build a unit to prove it to yourself as I noted in another post.  A simple two-pole generator with one coil will be sufficient as a learning experience.
--
Chris

[bob g]

Chris
your assessment assumes i have not built and done such testing

what you state is patently false, and here is the reason

if you take a machine such as a 12 inch neo rotor job typical of those built here, (for the sake of discussion)

now rotate the rotor very slowly past one of the stator poles, and measure the voltage of that poll. you  will find it to be very low

now speed the rotor up and you will find the voltage to increase, \

everything is the same, the magnets have not changed, so the magnetic flux has not changed, the coil has not changed so the flux linkages have not change, only thing that has change is the velocity, so...

velocity certainly has a function here.

lets do a little mental experiment here.

lets take a bicycle wheel that is say 24 inches in diameter, we will also affix to the wheel a smaller diameter wheel made of plywood that is 12 inches in diameter, when spinning both rotor turn the same speed in rpm, however rim speed of the outer rim is double that of the inner 12inch rotor.

if we affix the inner 12inch rotor a magnet, and using an arm to affix a coil with 30 thousand clearance, and we turn the wheel at 100rpm we end up getting X volts. the magnet passes the coil in this test at ~3770 inches per minute.

now if we move the magnet to the outer 24 inch rim, and move the arm which mounts the coil to the outer position, and set the clearance to 30 thou as the first test, and turn the wheel at 100rpm the impressed voltage will be proportionally higher at around ~2X volts. the reason being we have an outer rim speed in this case that is twice that of the previous test which is now ~7540 inches per minute.

this is no different than if we were to go back, remount the magnet to the inner rotor, and move the arm that mounts the coil, set the airgap, and then turn the wheel at 200rpm, the voltage will now be approx twice that of what it would be when turning at 100rpm.

there really is no difference!

my only point is we cannot summarily dismiss the effect of diameter on the voltage produced, diameter has a function in the formula, or at least can when it comes to designing an alternator.

one last point before i get told to go out and build something to prove your point.

long ago i learned from an instructor smarter than most of us will ever be,  he  posited this

"why do we draw,  or use drafting, instead of just going out to the shop and building something?"

the answer

"paper is far cheaper than any building material"

now this doesn't have direct application here, but i figure it has a correlation when it comes to design of any machine.

"we study, we research, we learn and use theory/formula etc. we then draw it out on paper, use logic and when all else fails and we can't get the answer we need we then go out in the shop and build"

otherwise we never learn why something works, or perhaps more importantly why it works better than some other way.  we can certainly determine if something works, but we generally cannot quantify or qualify our findings in a manner that anyone else is going to understand. we certainly cannot predict with any certainty what effect a change might make in a design before building it.

now having said all that,

i would not expect a doubling of voltage with a doubling of diameter, because of the time factor between poles, the gaps between the poles (assuming the same pole count as a smaller diameter unit) will certainly impact the change in voltage to the point the we won't generally see a doubling, but with careful design we can see an increase.

this was all i was saying to start with, we cannot summarily dismiss diameter effects on generated voltage.

now if we want to talk about what increased diameter allows in design, that would be a useful topic in my opinion. 

bob g