New Member

[Laurie Forbes]

Hello All:

I'm a new member to the forum after having been advised of its existance by Rob Beckers on the A-H-W list. My priimary interest is wind power and have constructed a 12' 4 blade horizontal axis turbine driving a 1 1/2 HP 3 ph motor fitted with ceramic magnets. Power output is about 1 KW. Overspeed control is via a tilt-back mechanism. Blades are laminated lengths of 1x6"finger" board "carved" using a jig and radial arm saw with a belt sander for rounding the edges.

I recently have become interested in speed optimization and control by varying the blade pitch. I am aware there are means of doing it mechanically but was unable to find any relevant plans and did not want to try to develop it from scratch (trying to get all the geometry, spring rates etc. right).

I then considered electronic means with a microcontroller driving a motor in turn driving a screw mechanism which would drive a "spider" at the blade hub to vary the pitch. What I came up with was a cordless drill for the motor, a threaded rod/nut as the screw, and a rod through the main rotor shaft that connects to the spider and the blades. I am using a "PicAxe" microcontroller (an preassembled educational product consisting of a Pic microcontroller and driver chip with other required components all mounted on a PC board). The controller is programmed in Basic and drives the drill motor via four MOSFET power transistors. The basic program is pretty simple - decrease blade pitch as the RPM increases and vice versa; also increase pitch at overspeed to maintain a maximum allowable RPM. I have it all assembled now and am testing on the bench.

I have taken some images and will post them if anyone is interested, if I can find some software to reduce the image file size (they are now about one meg).

If anyone else has ever dabbled in such a thing I would be most interested in reading your comments (or even if you haven't :) ).

Laurie Forbes

[Laurie Forbes]

Here are some images of my pitch control mechanism to date:

The first is the "spider" and rod through the main shaft plus the pitch rotation bearings/shafts (for two blades only so far).

The second is the alternator and associated drive train.

The third is the drill & threaded rod actuator mechanism with the position feedback potentiometer & its actuator (the slotted wood thing).

The fourth is the control board with the PicAxe micro & power supply, drill motor driver MOSFETs (mounted on the pieces of angle iron), manual control switches etc. It's powered by a 12V battery (not shown). Initially at least, this board will be mounted on the ground so it can be connected to the programming computer for testing.

Please excuse the Rube Goldberg appearance of the stuff - I have only minimal metal working equipment and try to use what materials I have on hand to reduce costs.:o

Laurie Forbes

[Rob Beckers]

If nobody else is going to say it I will: I'm very impressed! In a time where very few build things, I also think it's great you're doing this. It's an original idea too! So please keep doing what you're doing, I love it!

There is of course the obvious downside of using electronics to control pitch: If power goes out, or if the electronics fail (and neither is that uncommon), you may well end up with a runaway rotor. That would probably mean it's going to self-destruct. So I think this is indeed great as a test turbine, or for personal use, it's not something I would want to put up lots of. Maybe there's a way to mechanically force the blades to their "off" (stall or feather) position, unless the electronics work actively against it. So in case the electronics stop controlling it would return to "off". That would increase survivability.

As you mention, the alternative is mechanical pitch control. The turbine I peddle, Eoltec's Scirocco, uses mechanical pitch control. It is very simple in its working principle, not many parts involved either. It is essentially just a 'governor' as found on every old steam engine.

-Rob-

[Laurie Forbes]

If nobody else is going to say it I will: I'm very impressed! In a time where very few build things, I also think it's great you're doing this. It's an original idea too! So please keep doing what you're doing, I love it!

Thanks for the kind words Rob - I'll post some more on it once I get it up the pole and running.

There is of course the obvious downside of using electronics to control pitch: If power goes out, or if the electronics fail (and neither is that uncommon), you may well end up with a runaway rotor. That would probably mean it's going to self-destruct. So I think this is indeed great as a test turbine, or for personal use, it's not something I would want to put up lots of. Maybe there's a way to mechanically force the blades to their "off" (stall or feather) position, unless the electronics work actively against it. So in case the electronics stop controlling it would return to "off". That would increase survivability.

Certainly good points except the controller is battery powered so power outage should not be a problem unless an internal fault occures. There is also the possibility of powering the controller directly off the alternator, the theory being that no power is required if the wind isn't blowing.

As for runaway that is certainly not a problem I am not concerned about. Such a setup should have a backup shutdown as you mention, possibly some purely mechanical means of stalling or feathering the blades if uncontroled overspeed occures. I haven't spent a lot of time considering it yet but it will be something I'll add at some point later on if I can get the basics working first.

As you mention, the alternative is mechanical pitch control. The turbine I peddle, Eoltec's Scirocco, uses mechanical pitch control. It is very simple in its working principle, not many parts involved either. It is essentially just a 'governor' as found on every old steam engine.

Mechanical pitch control has obvious advantages but I look on this project as something interesting to work on as it involves a number of things including mechanics, electronics and programming. I believe electronic control also has the advantages of more flexible and easily changable control. I may have mentioned before that I at first designed a mechanical control system but concluded it would take a lot of trial and error changes to get something that would work m/l properly. I also looked for a design already developed and produced but was unable to find anything. Electronic control BTW also allows a lot of the trial and error stuff to be made easily from the ground (via program changes) which I think will be a big plus. It also alows changing of operating parameters on the fly (such as shutdowns or max allowable rotation speed). Anyhow, no matter how it turns out, it's been educational & fun so far!

One question Rob on the Scirocco - does it control pitch for overspeed only or also for better low speed performance??

Laurie Forbes

[Rob Beckers]

One question Rob on the Scirocco - does it control pitch for overspeed only or also for better low speed performance??
Laurie Forbes

The Scirocco does a bit of both: There is a 'start' position, controlled by a weak spring, that puts the blades in a position that makes starting the rotor at low winds easier. This is the position the blades will be in at 0 RPM, when both springs in the governor are full extented. At a fairly low RPM (don't know the number) the two fly-weights will depress the weak spring and pitch the blades to their 'run' position. It'll stay there until close to 245 RPM when the weights will start depressing the stronger spring, which limits rotation to that 245 RPM number.

-Rob-

[Logan Bryce]

Hi Rob

I think under 25 RPM tp override the spring!

I Love Pitch Control!!

Logan

[Laurie Forbes]

The Scirocco does a bit of both: There is a 'start' position, controlled by a weak spring, that puts the blades in a position that makes starting the rotor at low winds easier. This is position the blades will be in at 0 RPM, when both springs in the governor are full extented. At a fairly low RPM (don't know the number) the two fly-weights will depress the weak spring and pitch the blades to their 'run' position. It'll stay there until close to 245 RPM when the weights will start depressing the stronger spring, which limits rotation to that 245 RPM number.

-Rob-

OK, thanks Rob. BTW, the Scirocco is IMO a very impressive looking piece of equipment (looks like industrial quality rather than consumer). I'd be tempted to try such a thing but AFAIK, there are no grid-tie provisions in Alberta.

I should now mention that after looking at the Scirocco web site (and reconsidering the advantages of a purely mechanical system), I came to the realization that what I have constructed to date might easily be converted to such a system simply by adding weights to the spider arms and placing a spring on the small shaft going through the main shaft. I now have it partially constructed and think it will work in a similar way to what you have described above (I will post another pic when I get it going).

What I am waiting for now is a spring of proper length and spring rate (the local building supply joints have only a v limited choice and the spring specialty shops are closed for the holidays).

Am also trying to think of same way of utilizing the other stuff (drill, screw actuator and microprocessor). It could be used to remotely limit the amount of blade pitch reduction from the stop point to reduce the top speed.

Edit:

Here's a pic of pitch control by attached weights & spring (note the spring is smaller than required)

If I was doing this again I think I would dispose of the "spider" stuff and simply offset the blade rotation shafts and extend them inward until they overlap a little. A gear at each end would then mesh and keep the two shafts synced. A torsion spring(s) between the shaft bearings would provide the return torque.

[Rob Beckers]

He Laurie, I really wasn't trying to convince you to switch to mechanical pitch control. I liked the electronic solution! :) (Of course, being an electrical engineer myself, to me every problem looks like it can be solved by a bit of electronics ;) )

That aside, yes, looks like what you have in that last picture would do the job in principle. For appropriate springs, you may also want to take a look at a the motorcycle repair places around there. Something from a motorcycle front or rear suspension looks like it may be about right (when cut to length). Someone may have some old, free, springs somewhere. A progressive spring, regularly used in motorcycle front suspensions, would give you the effect of putting the blades in a 'start' position for weak winds. You can then play with the weights and arm to fine-tune things.

-Rob-

[Stewart Corman]

Laurie,
Just came here from your AWEA post.
I am also a builder and have posted several threads there ...
My ultimate design is a 15 foot HAWT of the Allison helix design whose features are: multiple rotors, lower rpm, higher torque, higher efficiency, fixed pitch, self feathering. I believe in the KISS principle.

I am impressed with the build shown in your photos!
Would like to see some performance curves.

I have three questions on specific areas of your design/build

1) Very few have used chain drives for the transmission, and I was just debating this myself. My preference was to use a 1" flat cogged belt, but I have available numerous chains and sprockets. Questions relate to maintainance ie grease/noise/wear/mechanical efficiency. I have searched for data and seen numbers around 91% for bicycle chain and as high as 98% (but special performance chain?)

2) Have you documented the build of the generator from the 3 phase motor by adding magnets? Any testing for electrical efficiency?

3) How did you decide on four blade configuration? Unless the TSR is low ie 3, there are many "experts" who claim that three blades is the optimum. The fourth slows down rpm, adds weight to assembly, steals wind from the other 3 blades ie no increase in performance.

Please keep this thread alive here, but also email me if you wish to maintain a dialog.

Stew Corman from sunny Endicott

[Laurie Forbes]

He Laurie, I really wasn't trying to convince you to switch to mechanical pitch control. I liked the electronic solution! :)

I know Rob - I came to that conclusion myself :) The mechanical system is so much simpler (and v probably more reliable) that I feel I've got to at least try it.

That aside, yes, looks like what you have in that last picture would do the job in principle. For appropriate springs, you may also want to take a look at a the motorcycle repair places around there. Something from a motorcycle front or rear suspension looks like it may be about right (when cut to length). Someone may have some old, free, springs somewhere. A progressive spring, regularly used in motorcycle front suspensions, would give you the effect of putting the blades in a 'start' position for weak winds. You can then play with the weights and arm to fine-tune things.

Thanks for the idea but I think such springs would be much too long and strong. It looks like a spring about 6" long and with a stiffness that would compress it to about 2 to 2 1/2" with a force of about 40 lbs would be close (the 40 lbs is about the max the two 5 lbs weights would exert on the rod at approx. 300 RPM). I could add more weight but don't want to impose too much side thrust on the spider bearings. Some more experimentation is in order.

I'm also wondering a bit about a requirement for oscillation damping. I could not see anything like that in the Scirroco pics but then again it is kind of hard to see exactly what is happening in the spring assembly.

[Laurie Forbes]

Laurie,
Just came here from your AWEA post.
I am also a builder and have posted several threads there ...
My ultimate design is a 15 foot HAWT of the Allison helix design whose features are: multiple rotors, lower rpm, higher torque, higher efficiency, fixed pitch, self feathering. I believe in the KISS principle.

Sounds interesting - can you post some pics?

I am impressed with the build shown in your photos!
Would like to see some performance curves.

I have three questions on specific areas of your design/build

1) Very few have used chain drives for the transmission, and I was just debating this myself. My preference was to use a 1" flat cogged belt, but I have available numerous chains and sprockets. Questions relate to maintainance ie grease/noise/wear/mechanical efficiency. I have searched for data and seen numbers around 91% for bicycle chain and as high as 98% (but special performance chain?)

2) Have you documented the build of the generator from the 3 phase motor by adding magnets? Any testing for electrical efficiency?

3) How did you decide on four blade configuration? Unless the TSR is low ie 3, there are many "experts" who claim that three blades is the optimum. The fourth slows down rpm, adds weight to assembly, steals wind from the other 3 blades ie no increase in performance.

1) I chose a "gear-up" system as it was a lot easier than building a direct drive alternator of 1 KW output @ 120 VAC & 300 RPM. I would have preferred a cogged belt but the sprockets are pretty pricey and the roller chain stuff is locally available for cheap. I've not researched efficiency but your numbers seem in the ball park. I'm pretty pleased with the performance of the roller chain so far in that there is not much noise and wear rate seems low. I've heard adverse comments as to durability but I keep in mind that motorcycle chains last for years with similar size chains transmitting much more HP (I used 5/8" for the 1st stage and 1/2 for the second, giving an overall ratio of about 5 to 1). Some sort of auto lube system would be useful however. Direct drive would work better but not worth the effort IMO.

2) About all I can tell you about the motor conversion is that I bought a good used Baldor 1 1/2 HP, 900 RPM, 3 ph motor and cut eight 1" wide x 1/2" deep slots in the rotor into which I epoxied 1 x 1/2" x 4 1/2" ceramic bar magnets. I don't have any means of measuring efficiency but I expect it must be pretty good as I don't know where any abnormal losses would occur.
All I know is I was able to drive it on the bench to 1 KW o/p with a 1 HP motor (although the motor was working pretty hard). If I do it again however, I would probably install neo magnets to get similar output at lower RPM (maybe then only a one stage gear-up would suffice).

3) I should have gone with three blades but was under the impression for some reason at the time that four would give better performance (which was wrong for the reasons you point out). I note however that the Scirocco turbine and others from the same manufacturer have only two blades which I understand will tend to give rough yawing (because of changing moment of yaw inertia as the rotor rotates) but I'm not sure that is a big problem for a well constructed machine.

Edit:

I would be interested in hearing Rob's comments on two vs three blade rotors.

[Laurie Forbes]

Hi Laurie,

Wow! That's quite a unit you've got there. Naturally, I have a couple questions about this setup (can't help myself it seems:-)
What are the two additional steel arms for?
What will prevent the blade attachment members (arms like the two I asked above) from flexing in high wind conditions, and (possibly) wreaking havoc with the pitching actuator rods and pillow blocks?
I think that your welded attachment at the point where the push-rod attaches in front looks a little vulnerable, and perhaps doesn't have enough penetration, but maybe it's just the picture. Have you considered a different method of making that connection? Just curious.

Very cool!

Cheers,

Matt

Matt:

I've taken the liberty of responding to your queries (originally posted on AWEA) on this forum as I feel the format here is much more useful than an email list serve (I hope that is OK).

Anyhow, the two additional arms are there because the turbine was originally a four blader (not to be confused with bladder). I'm only going to use two blades, at least initially, for the pitch control experiment.

I hope there will not be too much flexing as the arms are quite solid being constructed of 4" x 3/8" flat steel (and the pivot shafts are 1" dia).

The welding at the push-rod attachment is indeed not elegant but I think it is strong enough to hold (I'm by no means a great welder, have only a buzz box, and find it quite hard to weld small pieces w/o burn through). I'm thinking a MIG welder would have been more suitable (maybe someday). In any case, I've never had a weld break on me :)

Laurie

Edit:

BTW, here's a pic of the four blader (with tip-back furling).

[Rob Beckers]

Edit:

I would be interested in hearing Rob's comments on two vs three blade rotors.

Actually, Matt would be the better guy to ask this. ;) I'm nowhere near the specialist he is.

Since you're asking... My understanding is that there are good two bladed turbines, and good three bladed ones (bad ones for each too). Two blades has the advantage that it is cheaper to construct, can be more easily mounted on the ground (for the larger turbines this is an issue), and is potentially a little more efficient compared to three bladed turbines due to less wake effect and less drag. The (potentially large) downside of two bladed rotors is yaw-shudder. This is because when the two blades are vertical, it is easier for the rotor to yaw, then when the blades are horizontal. In essence the combination of rotation, wind, and blades sets up a stiff spring-mass system that can oscillate in the yaw-axis. If this happens it will drastically shorten the life of the bearings in the genny.

Three bladed rotors don't suffer from yaw-shudder, but potentially loose a bit in efficiency, are more expensive to construct (more material), and are harder to mount on the ground (the third blade gets in the way, so it has to be kept off the ground higher).

More than three blades has the issue that was mentioned before, efficiency goes down. There do not seem to be upsides to more than three blades.

Having said all that, in practice I believe it is more important how the turbine is designed and constructed. A good airfoil can make a 4-bladed rotor outperform a 3-bladed one (or a 2-bladed one). A well designed and constructed 2-bladed turbine can outlive a badly made 3-bladed one. For what it's worth, as far as the Scirocco is concerned, a 2-bladed turbine, the very first question I asked Eoltec was about yaw-shudder. They claim it is not an issue with their turbine. Until there are enough of them flying around here I can't confirm or deny that, but that's the word from the manufacturer.

At least that's what I heard. I'll now gladly let the experts correct me...

-Rob-

[Stewart Corman]

More than three blades has the issue that was mentioned before, efficiency goes down. There do not seem to be upsides to more than three blades.
-Rob-

Well, sort of ..I agree if you limit the "more than three blades" to a single rotor plane.

Here are some links for a different paradigm:-
diagram:
http://i145.photobucket.com/albums/r203/scorman1/Wind/Allison4.jpg

first the original article from Pop Science 1980:
http://i145.photobucket.com/albums/r203/scorman1/Wind/AllisonPg64.jpg
http://i145.photobucket.com/albums/r203/scorman1/Wind/AllisonPg67.jpg
http://i145.photobucket.com/albums/r203/scorman1/Wind/AllisonPg67.jpg

perfomance curve from a 20 ft prototype that ran for 6 months:
http://i145.photobucket.com/albums/r203/scorman1/Wind/EEI_5.jpg

Allison's hand drawn projected curve:
http://i145.photobucket.com/albums/r203/scorman1/Wind/Allison5.jpg
note the self feathering effect - rpm only doubles as WS doubles

my project:
http://www.geocities.com/scorman/turbine1.html

why it all works:
http://www.arvelgentry.com/techs/A%20Review%20of%20Modern%20Sail%20Theory.pdf


offline discussions welcome

Stew Corman from sunny Endicott
scorman@stny.rr.com

[Rob Beckers]

offline discussions welcome


Hi Steward,

The beauty of a Web discussion forum is that you can simply create a new thread and discuss. No need to take it offline. It's RE, so it is a perfect topic for online discussion (besides, we can use more threads and more discussion). :)

I certainly would be very interested in your project, and as you can see from the number of people viewing Laurie's, many others would too I'm sure.

By the way, yes, my comments about blade numbers was based on HAWT single rotor/plane gennies. I know almost nothing about multi-rotor (or in your case multi-plane) machines. I'm willing to learn though!

-Rob-

[Laurie Forbes]

Actually, Matt would be the better guy to ask this. ;) I'm nowhere near the specialist he is.

Since you're asking... My understanding is that there are good two bladed turbines, and good three bladed ones (bad ones for each too).....snip....



Rob, your analysis of two vs three is exactly to my understanding. One other thing occurs to me - yaw shudder could be reduced by adding weights, a couple of feet or so, to the rotor on either side of the blades (kind of a X shaped thing with the weight arms shorter than the blades. Such weights could be shaped in a streamlined form to reduce drag and, if heavy enough, should add a good measure of yaw inertia when the blades are vertical. The additional rotational mass would also tend to dampen rotor speed fluctuation in gusty winds (for whatever that is worth). Considering all this, I think my next mill will have two blades.

Back to my pitch control project, I have found that mounting the fly weights on the "spider" is resulting in uneven operation with poor repeatability. This seems to be occuring due to the centrifugal force and dead weight the fly weights are putting on the spider rotation points. So, I am contemplating moving the fly weights to the pitch rotation shafts (between the two bearings) and placing brass bushings in the spider joints (they are steel on steel now which is not great). The return spring also puts pressure on the joints so I would also like to replace it with torsion springs on the rotation shafts (the spider would then only serve to connect the two blades). Trouble is, I cannot find a supplier with torsion springs of the right size (1" plus a bit inside diameter) with large enough spring rate (I need about five inch/lbs per degree of rotation and the largest I can find, even by web search, is much lower). If anyone has any ideas where to get such a thing I would appreciate it.

[Laurie Forbes]

As an update to the pitch control project, I have moved the fly-weights from the spider to the pitch rotation shafts and added bronze bearings to the spider joints. This has made the shaft rotation (and motion of the spider) smoother and more repeatable.

I have also moved the return springs to the shafts, this too to reduce pressure on the spider joints. I was having trouble finding suitable torsion springs but chanced across large "safety pins" at a local surplus place and installed one on each shaft after a bit of modification. They work pretty well but have two problems: not quite strong enough and only about 30 deg rotation before they stretch (I would like about 45 min). So, I will try larger versions that I found today at a spring supply shop or, if they also cannot rotate enough, will wind my own from "piano" wire and using more coils to increase the rotation range.

Also went to a gear shop to see what was available off the shelf for possible later connection of the pitch shafts by two gears instead of the spider. They had a 1 1/2" dia steel spur gear with a 1" hub & keyway for $68 ea - a little pricey but doable I guess.

Anyhow, here's a pic of the latest incarnation (the drill in the left background is used to spin up the stuff via the jackshaft for testing):

BTW, a question: Roughly how much does a typical HAWT blade have to rotate from the normal full power position to go into complete (or nearly complete) stall??

[Rob Beckers]

BTW, a question: Roughly how much does a typical HAWT blade have to rotate from the normal full power position to go into complete (or nearly complete) stall??

Laurie already asked me this by PM, but maybe other are interested too. Hopefully it'll help breath more life into this marvelous thread!

The Scirocco wind turbine (http://www.solacity.com/scirocco.htm) uses blade pitch change to control RPM. The blades go from about 8 degrees (0 - 60 rpm), to 2 degrees (60 - 220 rpm), then variable from 2 to -10 degrees (220 - 245 rpm). I'm not entirely sure what the reference plane is for the angle, possibly the plane of rotation? It can't be angle-of-attack as this changes with the wind speed. The initial 8 degree is to help start the turbine, and it lowers cut-in speed by about 1 m/s. The normal 'running' angle is 2 degrees, until close to the governing speed of 245 rpm. The blades then move more and more into stall, as wind speed picks up, with a maximum of -10 degrees (which would normally never be reached, in any case at this angle the blades are completely stalled).

So in the case of the Scirocco wind turbine there are two springs controlling the blade angle: A weak one that is only used for start-up, and a much stronger one that regulates stall.

If designing a turbine with variable pitch it is important to completely reach stall through the governing mechanism. Anything short of that and there will be a wind speed where one runs out of pitch change, and for stronger winds the turbine will start accelerating again (and self-destruct).

-Rob-

P.S. Matt Tritt can comment on the angles used for the turbine he sells, made by Iskra. If I remember right they too use variable pitch blades.

[Laurie Forbes]

Laurie already asked me this by PM, but maybe other are interested too. Hopefully it'll help breath more life into this marvelous thread!

The Scirocco wind turbine (http://www.solacity.com/scirocco.htm) uses blade pitch change to control RPM. The blades go from about 8 degrees (0 - 60 rpm), to 2 degrees (60 - 220 rpm), then variable from 2 to -10 degrees (220 - 245 rpm). I'm not entirely sure what the reference plane is for the angle, possibly the plane of rotation? It can't be angle-of-attack as this changes with the wind speed.

It looks like the reference plane must be the plane of rotation as measured at the blade tip(?) Two deg AoA at the tip at the normal speed range sounds about right IIRC.

The initial 8 degree is to help start the turbine, and it lowers cut-in speed by about 1 m/s. The normal 'running' angle is 2 degrees, until close to the governing speed of 245 rpm. The blades then move more and more into stall, as wind speed picks up, with a maximum of -10 degrees (which would normally never be reached, in any case at this angle the blades are completely stalled).

So in the case of the Scirocco wind turbine there are two springs controlling the blade angle: A weak one that is only used for start-up, and a much stronger one that regulates stall.

I'm a bit surprised the weak spring allows going to 2 deg at such a low RPM (60) and that it starts at only 8 deg. I was thinking along the lines of maybe 30 deg at start and reaching maybe 50& of normal speed at maybe 10 deg however, the additional drag created by the higher angle of attack may negate any gains.

If designing a turbine with variable pitch it is important to completely reach stall through the governing mechanism.

An important point however I would guess one would also want to avoid overshoot as the blade pitch would perhaps then oscillate.

P.S. Matt Tritt can comment on the angles used for the turbine he sells, made by Iskra. If I remember right they too use variable pitch blades.

Hey Matt, I'd be interested too.

BTW, I find it kind of awkward to reply to posts with comments embedded in the original. I use the "Wrap quotes tags around selected test" which helps but one always has erase either the "[/QUOTE]" or the "[QUOTE]" to make it work right. Is there an easier method anyone could suggest?

[Rob Beckers]

It looks like the reference plane must be the plane of rotation as measured at the blade tip(?) Two deg AoA at the tip at the normal speed range sounds about right IIRC.

Even the blade tip has some angle to it, if not much. I'd think it's simply the plane that's normal to the axis of rotation (or in other words, the plane in which the blades spin). Either way, the more important part is probably the range. You can always change the starting position.


I'm a bit surprised the weak spring allows going to 2 deg at such a low RPM (60) and that it starts at only 8 deg. I was thinking along the lines of maybe 30 deg at start and reaching maybe 50& of normal speed at maybe 10 deg however, the additional drag created by the higher angle of attack may negate any gains.

Well, these angles are not angle-of-attack. The angle of attack for the blade is the vector that's the combination of rotational speed and wind speed. The rotational speed varies with wind speed, probably not entirely linearly though. But by and large this maintains some reasonable angle of attack in the 'running' position at 2 degrees throughout a range of wind speeds (with somewhere around 11 m/s a the point where the strong spring kicks in and starts moving the blades to stall).

From airplane wing profiles I remember the angle-of-attack range between 'flat' with no lift and full stall is really quite small. Depending on the profile a number of around 15 degrees comes to mind (it's been a while that I looked at those though, so don't quote me on that). A turbine blade is of course nothing more than an airfoil, just like an airplane wing.

An important point however I would guess one would also want to avoid overshoot as the blade pitch would perhaps then oscillate.

One would have to simulate the whole thing using some combination of CFD and mechanical model to be sure. That's what Eoltec did. While I do aerodynamic modeling (for atmospheric dynamics, ie. meteorology) I'm not a mechanical engineer. Maybe we have a real expert on the forum that can help out. There's no specific damping in the Scirocco's pitch control mechanism that I'm aware off. Just the friction of the bearings. There's quite a lot of mass though, because of the blades and the governor weights, making it pretty high-inertia. I suspect that the airflow itself creates its own dynamic with the blade, making it much 'stiffer', resisting dynamic (rotational) forces, that probably is part of it. But yes, you're right of course that one wouldn't want this to set up some oscillation mode. Unless you can do your own modeling there's only one way to find out... :D


BTW, I find it kind of awkward to reply to posts with comments embedded in the original. I use the "Wrap quotes tags around selected test" which helps but one always has erase either the "[/QUOOTE]" or the "[QUOOTE]" to make it work right. Is there an easier method anyone could suggest?

I've not come across anything better. What I do is copy "[QUOTE]" to the clipboard (Ctrl-C), and simply insert it twice (Ctrl-V, Ctrl-V) where I want to insert my own text, then add a slash to the first one. Works pretty fast, but is error prone. So "preview" is a must.

-Rob-

[Laurie Forbes]

Even the blade tip has some angle to it, if not much. I'd think it's simply the plane that's normal to the axis of rotation (or in other words, the plane in which the blades spin).

My poor wording. What I meant was the pitch angle, relative to the rotational plane as you state above, measured at the tip.

Well, these angles are not angle-of-attack. The angle of attack for the blade is the vector that's the combination of rotational speed and wind speed.

Quite so - incorrect choice of words again.

I suspect that the airflow itself creates its own dynamic with the blade, making it much 'stiffer', resisting dynamic (rotational) forces, that probably is part of it.

Thanks for mentioning that as it's another factor I've been wondering about (the blades resisting (or assisting) pitch rotation via influence of the airflow, if I understand you correctly). In any case, I will start out with the mechanism set to stall at fairly low RPM and work up from there.

I've not come across anything better. What I do is copy "[QUOoTE]" to the clipboard (Ctrl-C), and simply insert it twice (Ctrl-V, Ctrl-V) where I want to insert my own text, then add a slash to the first one. Works pretty fast, but is error prone. So "preview" is a must.

That's the way all web forums I've visited seem to work - I don't understand why the software can't take care of it i.e. place the required quote/unquotes automatically.

[Rob Beckers]

That's the way all web forums I've visited seem to work - I don't understand why the software can't take care of it i.e. place the required quote/unquotes automatically.

Not to keep whipping this (almost) dead horse, but I did just remember one feature that may help a little: There's a button at the top of the editing window that'll auto-insert the "quote" tags around selected text. So, select the 'middle' parts of the text that you want to comment about, and for each part hit that "quote" button. Not spectacularly better than just pasting with Ctrl-V, but it may help in a hurry.

And now I'll shut up about it and let everyone get back to the subject at hand! :cool:

-Rob-

[Rob Beckers]

Laurie, any news on your wind turbine?
It's been a while since we last heard from you. Who knows, maybe it's already up on a tower and lighting up the house! :)

-Rob-

[Laurie Forbes]

Laurie, any news on your wind turbine?
It's been a while since we last heard from you. Who knows, maybe it's already up on a tower and lighting up the house! :)

-Rob-

Not quite yet. I've just constructed a new yaw axis (this one has a hollow shaft (actually just a piece of pipe) so I can run the power cable thru and do away with the previous slip rings (which didn't work that well)).

Am now working on the pitch change mechanism enclosure. I'm a bit stuck on how best to seal the pitch rotation shaft(s) where they exit the enclosure without introducing too much friction.

In any case, it will probably be into spring b/f I can raise the thing as my small tractor won't get enough traction when the ground is frozen (good excuse to buy a bigger tractor I guess).

[Tony Savage]

Hi Laurie, I really like your ideas. I have started the planning for my own turbine which is going to use a 10 HP, 3 phase, 600 volt motor. My experiments so far are to spin the motor in my lathe using capacitors for self excitation. At 1000 rpm, it was powering 500 watts of light bulbs at 260 volts and 36 Htz. The lathe goes to 1400 rpm but it is difficult to load with light bulbs without blowing them. With no load at 1400 rpm I generate 460 volts. My thoughts are to use a transformer to drop down to 120 volts (or less) and then into a controller (or two). I was wondering if anyone has any thoughts on using magnets as compared to using the capacitors. One nice thing about the capacitors is that there is no danger of a dead short or an overload as it just kills any power output. I'm not sure about the efficiency though, 500 watts at 1000 rpm seems a little low for output.

Back to your turbine, Laurie. One thought that occurred to me is that the axis for the counter weights is perpendicular to the major force acting on them. At least it looks that way in the photos. I just wondered if they could be turned 90 degrees somehow and that would make them operate more smoothly and consistently. Just a thought. My intention is to use chains and sprockets too. They are dirt cheap, available anywhere and easy to change the gear ratio if required. They should last a long time too if they get regular lubrication. I was thinking of running a brake line up the tower and inject oil at the bottom to spray on the the chain and sprockets. Still mulling over the blade/hub design. Was thinking of self regulating blade but not sure that I could pull that off easily. Your idea with the pillow block bearings seems like a good one though, hope you have some feedback soon as to how everything works out.

[Laurie Forbes]

Hi Laurie, I really like your ideas. I have started the planning for my own turbine which is going to use a 10 HP, 3 phase, 600 volt motor. My experiments so far are to spin the motor in my lathe using capacitors for self excitation. At 1000 rpm, it was powering 500 watts of light bulbs at 260 volts and 36 Htz. The lathe goes to 1400 rpm but it is difficult to load with light bulbs without blowing them. With no load at 1400 rpm I generate 460 volts. My thoughts are to use a transformer to drop down to 120 volts (or less) and then into a controller (or two). I was wandering if anyone has any thoughts on using magnets as compared to using the capacitors. One nice thing about the capacitors is that there is no danger of a dead short or an overload as it just kills any power output. I'm not sure about the efficiency though, 500 watts at 1000 rpm seems a little low for output.

Hi Tony:

Sounds like an interesting project you have going. As it happens, my alternator (with magnets in the rotor) peaks out at about 1400 RPM at which point it produces 120VAC and about 1 KW. I don't have any numbers but I think you will find magnets will give much better perfromance then the capacitors (500 W at 1000 RPM from a 10 HP motor does seem quite low). Another advantage of magnets is that the RPMs required for a given output should be a lot lower especially if neos are used (I used ceramic in mine). Maybe only a one stage "gear-up" from turbine to alternator would then be required.

Back to your turbine, Laurie. One thought that occurred to me is that the axis for the counter weights is perpendicular to the major force acting on them. At least it looks that way in the photos. I just wondered if they could be turned 90 degrees somehow and that would make them operate more smoothly and consistently. Just a thought.

I see what you mean but that would take extra linkage to translate the rotation of the weights to rotation of the blades so I'm not sure one would gain much by doing that (it seems to work as is even though larger weights are required).

My intention is to use chains and sprockets too. They are dirt cheap, available anywhere and easy to change the gear ratio if required. They should last a long time too if they get regular lubrication. I was thinking of running a brake line up the tower and inject oil at the bottom to spray on the the chain and sprockets.

I've been thinking how best to do that and have not come up with an especially good solution. A line up the tower would work but would have to have a swivel joint at the top to get it past the yaw axis. I suppose it would have to go up the centre of the axis but it should work I would think.

Still mulling over the blade/hub design. Was thinking of self regulating blade but not sure that I could pull that off easily. Your idea with the pillow block bearings seems like a good one though, hope you have some feedback soon as to how everything works out.

We shall see. I think it's the only way to go for larger turbines (mine is 12 ft and I would like to go larger if I can get this one to work). It wouldn't be especially hard to build if you have a welder, drill press and chop saw (and access to a Princess Auto :))

It will be a while b/f I get it up, so to speak, as there is still snow on the ground here and my small tractor needs all the traction it can get.

[Laurie Forbes]

Tony:

I should have added that my next effort will probably not use the "spider" linkage to sync the two blade shafts. What I think I might do is simply offset the shafts a bit and overlap them with a couple of gears connecting them (a lot simpler with less friction).

[Tony Savage]

I've been thinking how best to do that and have not come up with an especially good solution. A line up the tower would work but would have to have a swivel joint at the top to get it past the yaw axis. I suppose it would have to go up the centre of the axis but it should work I would think.
Don't I feel dumb, I keep forgetting about the yaw axis. Maybe an airline swivel fitting might work. The other thought I had was a resevoir with just a drip lube system. Top up once a year??

Also, have you checked the waveform of the output of your motor? Would it be single phase or three phase? With the capacitor setup the output is single phase.

[Mark Parsons]

Greetings Tony,

I will attempt to answer your induction generator question. I have also used capacitors for self excitation on an induction motor. I used a C-2C configuration. My research indicates that:
1.) Efficiency is close to nameplate at 110% nameplate RPM. Lower RPM significantly reduces the efficiency.
2.) Power available is about 60% (or more with adequate cooling) of nameplate at 110% nameplate RPM to get around 60 Hz. Reactive power circulating through the excitation capacitors limits the available true power. Using a C-C-C configuration allows you to use the 3 phase power instead of single phase for full power utilization.
3.) Be sure to spin up and down unloaded otherwise remnant rotor magenetism will be cleared and motor will need to be re-magnetized using a DC voltage source.

If you plan on a grid connected application or using the induction motor - you should see the Prairie Turbines site for ideas if you haven't already - http://www.prairieturbines.com/

Where is Wyevale? I look forward to seeing your bird flying.

Mark

[Tony Savage]

Hi Mark, Thanks for the good info. I am using the C-2C set-up to keep the output single phase. Right now I am using 30 and 60 micro-farad capacitors. Do you have any good info on what size works best with what size motor? I'm not sure if the capacitors affect the output or if they are just used for excitation purposes. Wyevale is about 80 miles north of Toronto. It will be a while before I get anything in the air though. This is planning for the future for a piece of property we own and will be building on in the next couple of years. The house is going to be about 1000 ft from the nearest hydro line so the idea is to be off grid and use the money that we save from not running the hydro line (plus a couple of bucks more...lol) to pay for Solar panels etc.. I can't buget for a new medium size wind generator hence the interest in a home made one. I did see the Prairie Turbines web site but have some doubts to the output numbers he quotes and besides, I think there's a bigger wealth of info to draw from in this forum. Anyway, that's my long winded story and I'm sticking to it...

[Mark Parsons]

Greetings Tony,

I used this reference.
http://www.redrok.com/cimtext.pdf

It shows sizing only for a C-C-C configuration. I found other references when experimenting showing the C-2C option but without sizing data. Your 30 - 60 microfarad for 10HP, (I assume 4 pole motor - around 1800RPM nameplate based on your post data) sounds a little light. However, capacitor sizing is not an exact science due to many construction differences in motors. If you have the motor self-excited, which you do, and it remains self-excited when fully loaded you have the right amount of capacitance. Adding more doesn't provide any gain to my knowledge other than maybe more inductive load capacity.

The capacitors will raise the unloaded voltage output. The voltage output also varies with RPM. To use these for harvesting wind energy, a good variable pitch blade system is required to keep voltage and frequency in efficiency tolerances as well as some controls to connect the load when up to speed. They lend themselves better for microhydro applications with fewer complications.

My situation sounds very similar to yours. We built a log home cottage 1.4km from the grid in the upper Ottawa Valley 2 years ago. We decided to keep it off grid. We are lucky enough to also have microhydro at our disposal. I have been thoroughly enjoying the challenge of DIY renewable energy systems for the cottage. I have solar PV and HW, DIY wind (vertical and horizontal axis)and DIY hydro electrical and pumping systems. Mostly test machines at this time while I evaluate and design more permanent solutions from the knowledge gained. It is quite enjoyable to read at night by light created from the local environment and without a monthly bill.:D

Regards,
Mark

[Tony Savage]

Thanks for the good info Mark. It sounds like you have a great thing going there at your cottage. I would love to experiment more with all of this stuff too but find it difficult to find the time. I'm sure that I'm not alone in that regard.

With the motor that I am using my initial thoughts were to use large blades that produced good torque at low wind speeds but were very in-efficient at higher speeds. Self regulating is the expression I think, please correct me if I'm wrong. If this is achievable, then my hope is that the range of rpm for the motor/generator will be 1000-2000. Am I out to lunch on this? Any input is welcome.

I am reluctant to use magnets in the motor for two reasons. 1). Easy to replace if it goes south for some reason. 2). Without the magnets it is very easy to turn so it should have a low start up speed. I'm thinking that the magnets will give the motor a "notchy" feel and will require some force to get it started turning. I've never seen an AC motor fitted with magnets to know if this is an issue. Again, all comments are welcome. When chucked in my lathe producing 500 watts of power at 1000 rpm, I can hold the motor frame from turning with my pinky finger. The resisting force is totally smooth.

I have a line on a used 600 to 120 volt transformer which is single phase. Am holding off buying for now until I know if my generator will be producing single or three phase output. Will have to wait until I get transformer so that I can load up my generator and check it's output at higher rpms. Kind of a catch 22.

[Laurie Forbes]

Don't I feel dumb, I keep forgetting about the yaw axis. Maybe an airline swivel fitting might work. The other thought I had was a resevoir with just a drip lube system. Top up once a year??

I considered a drip system but the drip rate would have to be so low that I wonder if it could be designed to perform consistantly. If a good chain lube is used, I expect one could go several months at least w/o servicing but OTOH maybe not as I've had no direct experience. Cogged belts & pulleys are another way of doing it, require no lube, but are quite a bit more pricey. One other alternative would be a serpentine belt as used in cars - should be lower loss than V belts and cheaper than cogged. The pulleys could also be fairly readily constructed with a lathe I would think.

Also, have you checked the waveform of the output of your motor? Would it be single phase or three phase? With the capacitor setup the output is single phase.

The waveform is a pretty good sine wave, three phase. Single phase o/p is an advantage alright but I wonder at what cost to efficiency or capacity? Frankly I surprised a 3ph motor can be used to deliver 1ph power (assuming all 3 phases are tied in).

[Tony Savage]

I considered a drip system but the drip rate would have to be so low that I wonder if it could be designed to perform consistantly. If a good chain lube is used, I expect one could go several months at least w/o servicing but OTOH maybe not as I've had no direct experience. Cogged belts & pulleys are another way of doing it, require no lube, but are quite a bit more pricey. One other alternative would be a serpentine belt as used in cars - should be lower loss than V belts and cheaper than cogged. The pulleys could also be fairly readily constructed with a lathe I would think.


I wonder if you could scavenge an oiler pump from an old chainsaw, drive it from the main shaft and oil it that way. They are adjustable and the rpm would be so low that the oil should last a long time. The belt drive idea doesn't appeal to me personally. You would have to have an automatic belt tensioner which wouldn't be too hard to make I suppose, but water and or ice getting on it may be a concern too. Brute strength is another advantage with chain. Usually on electric motors 5 hp and bigger they use multiple belts, which again is possible but then the whole thing starts to get a bit complex, matched belts, etc. On the other hand it may work really well. You never know unless you try it first. I was planning on using only one chain on my rig with approx 10 to 1 ratio to start.

[Stewart Corman]

Why aren't people considering planetary gear assemblies like these:
http://www.surpluscenter.com/item.asp?UID=2007032219470787&item=13-1350-10&catname=powerTrans

forget belts and chains

note: I am presuming >=15ft diameter turbine capable of 3.5+ KW max = 2.6+ hp @ 20mph WS and 250 rpm ...spec'd out larger size for overspeed conditions

they have lighter gear units rated at 2.85HP and 6:1 ratio for a 10ft turbine running at 350rpm = <1.5hp ...only weighs 27 pounds
http://www.surpluscenter.com/sort.asp?UID=2007022614554375&catname=powerTrans&keyword=PGRI

note also the following generator/motor:
http://www.surpluscenter.com/item.asp?UID=2006062721573810&item=10-1672&catname=electric

[Laurie Forbes]

I wonder if you could scavenge an oiler pump from an old chainsaw, drive it from the main shaft and oil it that way. They are adjustable and the rpm would be so low that the oil should last a long time. The belt drive idea doesn't appeal to me personally. You would have to have an automatic belt tensioner which wouldn't be too hard to make I suppose, but water and or ice getting on it may be a concern too. Brute strength is another advantage with chain. Usually on electric motors 5 hp and bigger they use multiple belts, which again is possible but then the whole thing starts to get a bit complex, matched belts, etc. On the other hand it may work really well. You never know unless you try it first. I was planning on using only one chain on my rig with approx 10 to 1 ratio to start.

Don't know much about chainsaw oilers but it sounds interesting. Are they some sort of positive displacement device (like a plunger pump)? If so, and they can be adjusted low enough they should flow reliably w/o plugging or becoming erratic I would think.

10 to 1 is a pretty high ratio if you consider the driven pulley should be as large as is practicable (a small pulley puts a lot more load & wear on the chain, both in tension and flexing). 10 to 1 in turn makes the drive pulley v big, that is, 30" if the driven pulley is 3". That in short is why I went with a two stage as the ratio(s) then are in your case are sq root 10 or about 3.2

IIRC you can get single cogged or serpentine belts that should handle the load quite readily. For example, a timing belt in a diesel engine typically drives the cam shaft(s), fuel inj'n and water pumps so they are pretty tough. Automotive serpentine belts drive the alternator, PS pump, AC compressor etc. so are also quite capable. You would still probably want to go with a two stage IMO.

[Mark Parsons]

One of a few companies that offer self contained automatic lubrication for oil or grease dispensing.

http://www.agslube.com/products.htm

[Tony Savage]

Mark, It's funny that you mention that planetary reduction. I had originally planned to use one my father in-law has (he has a saw mill). That is until I picked it up or tried to. It is way too heavy. The unit you pointed out isn't too bad though, 78 lbs I think. Always nice to have options.

Laurie, Yes, the chain saw pump is a mechanical plunger, positive displacement pump. Most of them have some kind of adjustment and I'm not sure how that works, maybe a helix and slot arrangement. Mark points out a nice alternative too. You're right about the cogged style of belt, they are quite strong. The serpentine belt is probably strong enough too. Decisions decisions....

Yes, I realize that the large pulley would be about 24" in diameter and that the smaller pulley is likely to wear more quickly. That same setup with the small pulley driving the large one would have a reasonable life expectancy, I'm not sure how well it would work the other way around. The beauty of a single chain of course, is that there are fewer moving parts. I don't think that losing 2 feet in the center of the blades is an issue with 10 ft blades (20 ft diameter)

[Tony Savage]

I sure wish every day could be a weekend!! It sure is nice having a little extra time to play around. I went down to my father in-law's saw mill and rummaged around and found a much lighter helical gear reduction box. At 15:1 ratio it's a little higher than I wanted but close enough to play with. I wanted to see what the losses were in terms of efficiency by just turning the gears with no load. It seemed quite stiff to turn by hand. Chucking the unit in my lathe and running at 200 rpm input resulted in a large amount of drag. I drained out the 90 weight gear lube and re-filled with 5W50 synthetic motor oil. I let it run at 200 rpm for 30 mins. Temp of gear box was 100 degrees F. Measured torque was approx 9 ft.lbs.

Taking Marks advice, I picked up some extra capacitors. Now I have 75 and 150 microfarad caps. on the same 10 HP motor. Wow! What an improvement. At approx. 800 rpm, the motor/generator can carry a 1000watts of lights at 250 volts. I also measured the torque on casing and it was about 12 ft.lbs. If someone had the right formulas, we should be able to figure out input power versus output power.

Conclusions: The gear box seems way too in-efficient. Will have to try a belt or chain setup for comparison. A 100 tooth sprocket doesn't appear to be common so it looks like I'll have to try Laurie's idea of two smaller reductions that he used in his unit. I'm going to pick up more capacitors and see if there is any more improvement to be had with the motor.

[Mark Parsons]

Greetings Tony,

Sounds like you made some progress today. I too wish every day was a weekend day.

Glad to hear that the added capacitance bumped up your output. Be sure to use only motor run or power factor correction capacitors rated for a voltage at least double your expected use. Capacitors can let their magic smoke out quite explosively.;)

Power = torque * RPM, 1HP = 746 Watts = Torque (ft.lbs) * RPM / 5252
From your data = 12 ft.lbs * 800RPM / 5252 = 1.82HP = 1,363 Watts

Efficiency = output power / input power * 100%
From your data = 1000 watts / 1363 watts * 100 = 73%
Better than some small brushed DC PM motors commonly used as generators.

If you're planning for battery charging with this motor you need to design for motor RPM at cut-in to exceed battery terminal voltage. Example - 24V battery bank charging with above motor that makes 250VAC at 800 RPM cut-in is only 55RPM (24VDC/(250VAC*1.4for peak)*800RPM). However, with many low RPM losses on induction motors you would likely need about 80RPM to be sure. You may not need as much of a gear ratio as you were thinking.

Regards,
Mark

[Stewart Corman]

Tony,

Measured torque was approx 9 ft.lbs.how are you measuring torque on a rotating shaft??

BTW, a planetary gearbox 10:1 supposedly has 95% efficiency, flat cogged belts 98% , chain drives 92% but had better be well oiled and add extra friction from extra idler shaft if used

Stew Corman from sunny Endicott

[Tony Savage]

Hi Mark...

Thanks for the formula and plugging the numbers. It doesn't get much easier than that. Don't be sending me a bill for doing all my work for me... lol. If my measurements are correct then it looks like I've got something that will work. The motor seems to generate power at 800 rpm every time. Even after I let it stall out under load. If it doesn't stop under load (remove load and then shut off lathe) it will start to generate at 600 rpm. I'm using motor run capacitors which I think are the correct ones. They are rated at 460 volts. I was going to run two together in series which will double the voltage rating and keep the capacitance at the rating as one capacitor by itself, correct???

I not sure I follow what your thoughts were on the gear reduction. My thoughts are 10 to 1 ratio. Ergo 80 rpm on the blades equals 800 rpm on the motor. Is that what you meant? Hoping to regulate max blade speed to 200 rpm or less. Do these seem like realistic numbers for a 20 ft diameter blade. What kind of wind speed is needed to get 1000 watts of output from this particular motor?

Hi Stewart,

Because the shaft of the motor is chucked in my lathe, the frame of the motor is free to rotate. I just use a digital scale on the frame to measure the resistance to rotate. I then measured the radius from the measuring point to the center of the shaft and converted to ft lbs.

In regards to the efficiency of the gear box. Could it be that because we are driving it backwards that the efficiency is so poor? I am hoping to cobble up some sprockets and chain and do a comparison soon.

[Mark Parsons]

Hi Tony,

Putting equal capacitance values in series will half the voltage exposure for each capacitor. I would definitely recommend putting 2 in series for your application with only 460V rated motor run caps. When your motor is rotating at 2000RPM the terminal voltage will approach 700VAC.

Great information by the way on the reduced speed and power testing of your motor. I didn't get as comprehensive in my brief experimenting with induction motor as generator.

I went back and read your previous posts. Your plan is to use the wind turbine along with solar for your off-grid cottage / home, which means battery system. Any thoughts yet on battery system voltage? Higher is normally better. 24V is very common and 48V is becoming more common these days. I went 0-12-24 in my cottage and ran all lighting circuits 12V due to common availability of 12V bulbs. My inverter will run from 24V. The reason I ask is for transformer ratio selection.

It is important that you keep the continuous amperage draw from the motor at or below nameplate for thermal protection. You indicated the motor is a 10HP, 600V, 3ph - therefore nameplate should read about 10amps. Intermittent short duration spikes of up to 3 times rated current during gusts should not hurt the induction motor.

I would also size the transformer conservatively. e.g. 7.5KVA 600V/120V. At 800RPM = 26Hz = 250VAC primary then secondary should be about 50VAC. I am very interested to see data on the transformer efficiency at the lower frequencies. I expect that efficiency will drop off, but I don't know to what extent. Little is published for this and I haven't experimented. Perhaps someone else on the forum can comment.

If you haven't figured this out yet, my background is electrical. I will defer to Stewart as the better expert to provide you with guidance in swept area and power harvesting expectations, airfoil selection, TSR, and hence RPM. Stewart also has a comprehensive Excel spreadsheet he has posted on another thread to help model a design. 20 foot diameter is definitely ambitious for a first project.

I found the Ontario Wind Atlas to be a good place to start for site area wind resource information. http://www.ontariowindatlas.ca/

Mark

[Tony Savage]

Hi Mark,

Thanks for confirming the capacitor issue. High school electronics class was a long, long time ago. What I hope to end up with is this:

- 600 volt generator to minimize losses from tower to house. (approx 800ft)
- capacitor/transformer in power room in house with min. voltage cut in and high voltage cut out circuitry.
- transformer output into charge controller(s) hoping to use 0-120vac. Will rectify to dc if necessary
- 48 volt battery bank, around 4000 amp hours
- two Trace 4000 watt inverters, will run stacked at 120 volts or in tandem for 240/120 volt. Trying to talk myself out of needing 240volts.
-4000 watts of solar panels with appropriate charge controllers
-7.5 kw Kohler generator

How do you like that for a shopping list? Well, I have the Kohler generator and the capacitors and a couple of years to sort the rest out. Would like to get wind generator to output close to a 1000w at 10 mph ws. I couldn't care less what the max output is at higher speeds.

"Play big or stay at home"

BTW I stopped by Princess Auto and picked up some sprockets, chain etc. Also got some more capacitors and started to experiment again but blew a 500 watt bulb. It was putting out 200volts, 3.8 amps, at 640 rpm It seems that the more capacitors the better.

[Mark Parsons]

Hi Tony,

Sounds like you have your plan in hand. Nice shopping list. Set your budget yet?:)

I am very interested in more data on your self excited induction motor experiments. I am looking to apply one in a microhydro application and if you are successful, I have a wind application too. I'm sure I'm not alone in this.

I think the group is also very interested in your project progress and data.

I would suggest that you start your own thread(s) in this forum so that ideas can be shared specifically on your project. Laurie may have issues with your hijacking of his thread. Plus this one is getting to be a long scroll down...

Mark

[Tony Savage]

Yes, I was wondering what Laurie might be thinking about that. I'm kind of new to this forum thing. I'll try to start a new thread and call it "self excited induction motor/generator". Budget for entire project....$50,000.

[Laurie Forbes]

Yes, I was wondering what Laurie might be thinking about that. I'm kind of new to this forum thing. I'll try to start a new thread and call it "self excited induction motor/generator". Budget for entire project....$50,000.

Makes no diff to me - the orig thread was pretty much moribund anyhow.

In regards to the input to your gen calculation, I calculate:

12 ft-lbs * 800 RPM * 3.142 / 33,000 ft-lbs/minute = 0.913 HP = 681 Watts

Since that is quite a bit less than your estimated 1,000 Watts gen output, either I have made an error, your estimation of input or output is in error, or you have invented a perpetual motion machine :)

With regard to the planetary gearbox, that would be nice alright if one could be found at the right price but that is a lot of loss. I'd be tempted to try a lighter oil still, maybe ATF? Does the gear box use ball or journal bearings?

BTW, Princess Auto is where I bought my chain/sprockets (cheap China stuff but not too bad IMO). Are you going with a two stage? As for shafts, I just use _cold_ rolled - a lot cheaper than ground and works just as well.

[Laurie Forbes]

Just took a look at the gearboxes mentioned here before.

http://www.surpluscenter.com/item.asp?UID=2007032820203759&item=13-1342-6&catname=powerTrans

Weights only 27 lbs and they ship to Canada - tempting....

[Ralph Day]

Hello Tony

Your project list sounds ambitious. Here's a few observations from someone off-grid and comfortable.

Unless you have an extreme level of loads, 4000amp hours of batteries is way too much. Lots of people want lots of reserve, but risk damaging their expensive investment (in batteries) by deficit cycling resulting in sulfation. You already have a genset, if your state of charge gets low enough, you fire it up for a few hours. November and December are the only months when I have to regularly run my genset. By regularly I mean once per week, twice per week, three times in two weeks, it's really not as bad as some make out.

I've got 1750watt pv, 1kw wind, 1156amp hours surrette batteries. Total genset run time for last 2 years...60 hours per year. That includes exercise and vacuuming days (.5hrs per run). Daily loads about 7kw per day.

I've found there's actually very few stretches of time where there's no inputs and you need to run the genset more than 1x per week. maybe 3 times in the past 3 years. IMO it's better to have less batteries and treat them well than have more batteries and treat them poorly.

Just ballparking the rough numbers: 4000watts pv $20K, 4000amp hours batteries $30-40K, Inverters $7K. Once you get some real numbers from suppliers you might realize the wish list is a little heavy on some wishes. Maybe "get what you need, need what you get" would be a more affordable axiom.

Just some thoughts. Didn't have a clue when I started out, one book, no forums, no nuttin. Hope some of this helps and doesn;'t disturb. Best of luck

ralph

[Mark Parsons]

Greetings Laurie,
In regards to the input to your gen calculation, I calculate:

12 ft-lbs * 800 RPM * 3.142 / 33,000 ft-lbs/minute = 0.913 HP = 681 Watts

Since that is quite a bit less than your estimated 1,000 Watts gen output, either I have made an error, your estimation of input or output is in error, or you have invented a perpetual motion machine

I've never seen that horsepower formula before. The 33,000 ft-lbs/minute value is correct. Your formula is missing another PI constant to make it complete. Circumference is 2*PI*R. Torque is a moment force referenced to center of rotation. Change the 3.142 to 6.28 and your formula is correct. HP=ft-lbs*RPM/5252. 5252 = 33,000 / 6.2833.
http://en.wikipedia.org/wiki/Horsepower
http://vettenet.org/torquehp.html

BTW - any new pics of your variable pitch machine or status updates?

Greetings Tony,
I have to agree with Ralph about the battery capacity issue. Batteries need to be exercised regularly with 20% or so discharge cycles. 48V * 4,000Amp-hours = 192kWh capacity. At 7kWh per day usage this is 27 days worth. I am planning on 4 days of battery capacity in my cottage system (26kWh). With the 20% rule this really means a full day with no inputs, is no problem. A full day with no sun, wind or water flowing will be unlikely.

Greetings Ralph,
Do you use a battery de-sulfator pulser on your system? I have found a few devices online with wildly different prices but have not invested in one yet.

Thanks.
Mark

[Ralph Day]

Hi Mark

I put nothing on/in or around the batteries, except what's supposed to be there. Only distilled water (which i can make on my own when needed, and sunny) goes in, and charged by installed equipment. Running a pulse unit would be using the battery to charge the battery here, a less that zero sum game.

http://www.sandia.gov/Renewable_Energy/renewable.htm

Check out the above and find the caploss.pdf. it's about battery capacity loss and regeneration. There's pics of batt plates that have been abused in various ways. it seems that the batt companies parameters for charge, watering and such are the best to follow (experience with lead acid only). Even with the lesser efficiency of FLA batts, they are more forgiving and cheaper than AGM or gel types. I'll stick with them

ralph

[Laurie Forbes]

Greetings Laurie,


I've never seen that horsepower formula before. The 33,000 ft-lbs/minute value is correct. Your formula is missing another PI constant to make it complete. Circumference is 2*PI*R. Torque is a moment force referenced to center of rotation. Change the 3.142 to 6.28 and your formula is correct. HP=ft-lbs*RPM/5252. 5252 = 33,000 / 6.2833.
http://en.wikipedia.org/wiki/Horsepower
http://vettenet.org/torquehp.html

BTW - any new pics of your variable pitch machine or status updates?

Blush - too long out of school I guess :p. I was thinking PI*D instead of 2PI*R. I guess you don't have an over-unity device afterall....

No new pics or status updates yet - am tinkering with the blade return torsion springs (a spring supplier gave me samples of larger safety pin springs that I am moding to replace two smaller springs). Haven't been in much of a hurry lately as I need the snow to melt and ground to thaw b/f my small tractor will have enough traction to raise the beast (may be a good excuse for a bigger tractor or maybe some Viagra in the fuel tank :D ).

[Tony Savage]

Hi Laurie,

Darn, I was kind of hoping for a perpetual motion machine there for a second!!! I have decided to go with a two stage set-up using the princess auto sprockets and hi-tensile chain. For shafting I am using old stainless steel prop shafts out of boats. I am a marine mechanic by trade. I took a look at the gear box. It looks good but is a little light for me. I could be dealing with 10 hp if everything goes well.

[Laurie Forbes]

Hi Laurie,

Darn, I was kind of hoping for a perpetual motion machine there for a second!!! I have decided to go with a two stage set-up using the princess auto sprockets and hi-tensile chain.Tony, was the high ten chain obtained elsewhere (the PA here doesn't carry it that I know of)? You know of course that the second stage chain can be lighter than the first.
For shafting I am using old stainless steel prop shafts out of boats. I am a marine mechanic by trade. I took a look at the gear box. It looks good but is a little light for me. I could be dealing with 10 hp if everything goes well.Are you cutting keyways in the shaft? I cut mine using an abrasive blade in a radial arm saw and a jig to hold the shaft - took a while and was kind of crude but works fine.

Yes, the gear box I looked at would be a little too small for you but about right for my prop. I wonder about the quality though - the castings look pretty rough (made in China I expect).

[Tony Savage]

Hi Ralph,

Your numbers actually confirm my own calculations for power requirements. You see, I had to promise my wife that we wouldn't be in a situation where we wouldn't be able to do something electrically because "there's not enough power to do that". That means maintaining our present electricity usage which is 30 kw hours per day. That's about four times what you said you use and my system is about four times bigger. Just for reference, I have an inverter and about 1000 amp/hrs of batteries at home for emergencies thru the night (my neighbours and I don't have to listen to the generator run all night). They get us thru the night but they are definitely less than 50% capacity in the am. Keep in mind these are "recycled" batteries, and are not 100%. I also have 1100 amp/hours in my boat. We get about 3 days before reaching 50% discharge. In regards to battery sulphation, equalizing with the inverter seems to take care of any sulphation, at least I've had no issues. I equalize once a month during the boating season. It's good to get actual usage info for genset etc. Thanks.

[Ralph Day]

Hi Tony

I guess I can get tunnel vision when it comes to loads etc. We've always line hung laundry (don't use a dryer), heated with wood, cooked with propane and been generally CHEEP! Too cheap to want to pay Hydro One any more than was absolutely necessary!:p

There's three loads that can dramatically reduce consumption...propane dryer, propane water heat, propane cooking appliance. Better yet, line dry, wood heat, solar/propane hot water, and cook over a fire outside!

Around here i'm the one who gets quizzed about wether what i'm doing will overtax the system. Janet is very up on all of this. She even dries her hair at work. When we spent 8 months reducing loads and living at that level, she is the one who said we should just go totally off grid...forget net metering, Hydro one and all that. Gutsy!

Have to celebrate! I got my Sunlawn reel type push mower yesterday! No more walking in the fumes of Lawnboy, no more earplugs and safety boots to cut the lawn. Can hardly wait for spring.:D

ralph

[Tony Savage]

Hi Laurie,

I bought the hi-tensile chain at PA. It just has a "-H" at the end of the chain designation number. I haven't done anything with the shaft and sprockets yet. Still thinking about how I want to build the frame work. Things are starting to come together in my head though. Trying to keep it light as possible and have it so that adjusting one chain won't affect the adjustment of the other chain. I decided to use the same chain on both ends. It keeps everything the same for repair purposes if necessary. I will take the shaft to a machine shop to get the keyways cut.

[Tony Savage]

Hi Ralph,

I know that our usage is fairly high but with two teenage kids and with the work I do in my shop, it will be hard to trim it by too much. We have a natural gas hot water heater and dryer. The stove is electric but will be propane in the new house. To offset that gain, though, we will have to power the well pump which we don't have now. Most of our light bulbs are fluorescent so not much to gain there. We do have two large side by side refrigerators and one is 20 years old. I'm sure replacing it with a smaller and newer more efficient one will help quite a bit. I still think that I'll need 20 kwhrs per day.

[Laurie Forbes]

Hi Laurie,

I bought the hi-tensile chain at PA. It just has a "-H" at the end of the chain designation number. I haven't done anything with the shaft and sprockets yet. Still thinking about how I want to build the frame work. Things are starting to come together in my head though. Trying to keep it light as possible and have it so that adjusting one chain won't affect the adjustment of the other chain. I decided to use the same chain on both ends. It keeps everything the same for repair purposes if necessary. I will take the shaft to a machine shop to get the keyways cut.

Tony, I don't see that in my '05' catalogue - must be a newer item.

When you say adjusting a chain are you referring to chain slack (and how do you do that (adjust one only) with an intermediate (jack) shaft arrangement)?

BTW, how much roughly would a machine shop charge for the keyways?

Oh, and what size chain did you buy (I've got 5/8 & 1/2 on mine)?

Please post some pics when able...

[Tony Savage]

Hi Laurie,

The idea for chain slack adjustment is this. Mount motor to its own frame. Mount jack shaft to its own frame. Attach the two frames together with a pivot on one side parallel to motor shaft, and adjusters on the opposite side. These adjusters would tighten the chain from motor to jack shaft. Then pivot the entire assembly (it would have to be an extension of the jack shaft frame) again paralled to shafts, on the main frame of turbine. Put adjusters on opposite side to adjust the slack in chain from the other end of jack shaft to the main turbine shaft. Hope that makes sense. I don't have anything built yet to take pictures of and I don't think I could draw anything that I could post here.

I am using #60 chain which is 5/8 ths I think.

I am guessing about 20 bucks for two keyways at the machine shop. It's a simple thing to do with the right equipment. One day, maybe...

[Laurie Forbes]

Tony, no need for a pic - I can see what you are planning re chain slack adjust and it should work alright, even if a little complicatred, but if you are building a custom mount for the stuff why not just build it so the main sprocket to jack sprocket and other jack sprocket to gen sprocket are the correct distance to begin with (I don't think slack adjustment for a roller chain is nearly as critical as for a belt drive ie. a little slop here or there won't hurt). OTOH I can see the advantage if you plan on trying different sprocket ratios to get best performance.

Wow, if you can get a machine shop to do two keyways for $20, I wish I'd known about that b/f I cut my own. Minimum charge around here is upwards of $100. BTW, I'm curious why only two keyways - won't you need one for the main shaft plus two for the jackshaft (assuming the gen has one already)?

[Tony Savage]

I kind of know the machine shop guy and I pay him cash. Sometimes I have to leave it for a week or so but the price is always right. I actually will only have to get one keyway cut because the shafts I am using already have a keyway cut in the ends. It is the other end of the shaft that is bent and will get cut off.