Stepper Motor Genny - Increasing Amps - How?

[wadlands]

 Hey Steve – thanks for taking the time & coming back to me – I really do value it.  Your first sentence made the light bulb go on!!!  Here's what I got out of it:

As soon as the turbine gets upto cut-in volts the battery immediately is able to draw down current from the genny (motor) but immediately its state as a “load” to the genny changes;  ie it incrementally represents a bigger load….which requires more torque from the turbine to even keep delivering the same amps as before (or if it can increase the amps).  This all happens “relatively quickly” - ie a place of equilibrium where the size of the load the battery represents to the turbine and the turbines ability (via torque) to deliver stabilizes out – at what I actually physically observe - which is rotor rpm's. 

As I got that, the second light bulb came on!!!!…..”if you could spin the genny fast enough by hand….”
The fundamental mistake I've been making is in my bench tests with the hand held drill as the motive force and testing at nominal 200rpm and 500rpm …..(time for a Homer Simpson) DOH!!! ….these are no load rpm's DOH!!!

So what I've been forgetting is that the hand held drill's true limitation is its deliverable torque and when I've used it to measure amps from my motor-genny tests then it pretty quickly gets to its point of equilibrium of amps it can push into the battery….and to get that the drill / motive force must be dropping its actual rpm's well below the max of 500rpm….DOH!!!

OK – so I've been dashing in & out of the garage since then – to test with my variable speed mains drill – which is much higher torque.  So much torque that I had to fashion a new coupling for the Brown Pestell motor.  GRRRREAT ……get it:

• Hand held variable speed drill at max speed – max amps into 12v 7AH lead gel = 2.5A dropping to about 1.9 / 2.0A
  
  Mains Variable Speed Drill at max speed – max amps into lead gel = 5A and hold …..BUT the torque nearly tears your forearm off!!

Ok – thank you – I get it – especially the variable load that the battery presents as soon as it receives it first dollop of current from the turbine genny. 

Also I found out a real new & valuable piece of learning with my Mains Variable Speed drill test – it takes a heck of a lot of torque to get 5 amps into a battery. 

With this piece of learning, I can see the results that I am currently achieving (about 0.5Amp) and a goal of 1 Amp from my Mk3 turbine as quite a fair challenge for myself.




Hi Norm – I can see that I've now got two reasons for building that pedgen. 

The above running around I've done and being able to feel the amount of torque required, to get an increase from 3 Amps to 5 Amps into the battery, using my mains variable speed drill, (ie need replaceable forearms) helped me get a realistic perspective on what I should expect as additional torque from my Mk3 turbine –invaluable & timely learning!!!

Gee

[Norm]

Your latest posting gave me so much 'fodder', I hardly know where to
begin.....
Okay to get you started think about this....
 Try different size batterys.....6volt takes less speed....12 volt....what you have now...
now see how much less torque it takes to charge a 2 12 volt batteries in series (24 volts that is)
Norm.

[Madscientist267]

Sounds like you've got it.

Another thing to keep in mind, is that the power that comes out of the genny, is proportional to the power going into the shaft, which is also proportional to the power going into the drill motor to drive it all. No such thing as a free ride.

I have to admit that I didn't quite put the two together when I was writing that last post, or I would have mentioned it as a factor. When your source of torque can't keep up, yes, your output will suffer.

You also may not have noticed it (mainly because you don't have enough arms to hold and connect everything at the same time LOL), but if you had connected the battery to the genny when it was already turning, you would have noticed the drop in RPM as more apparent. Might not have been nearly as obvious doing a run with it disconnected and then again with it connected. Especially if the loading was light (which IIRC it was).

You'll find yourself in the 'addict' stage now - LOL -  You'll easily find out why we all shave so much fat off of the production, control, storage, conversion, and use as we can - it isn't because we feel like it... It's because every electron pumped by an RE system is a precious drop in the bucket because those drops are so hard to come by. The old addage from my parents comes to mind here - "a penny saved..." - Is a watt earned?

Once you're hooked, it is almost as greed-getting as watching a bank account grow (wait, does that actually ever happen?  )

Of course, then there is the concept of dumping - LOL - Completely in contradiction to the above statement, but when you waste it, you want to make sure it's because you intend to waste it, because you need to, and not because your system is inherently inefficient. You'll get into that later...

For now, rock on. You're well on your way.

Steve

[wadlands]

Norm – hi – thanks for the additional follow-up – just being trying out the different voltage batteries…..  If my independently calibrated forearm torq'O-meters are giving true RMS readings then things are very curious indeed and not what I expected – unless I screwed up the “tests”:

Using my Mains Variable Speed Drill:

Yesterday - can get 5A into 12v lead gel with enough torque and hold upto max speed (drill windings give out a whiff of “we don't like this smell”!!)

Today can get ~ 9A into 2x lead gel in series ie 24v  and hold upto max speed - torque feels as if its less and the whiff of drill windings frying seems less pungent!!

However, into a 6v lead gel can get in 3A fairly easily but as speed goes up - extremely quickly torque goes sky high, drill windings complain pungently , forearms give up and the nylon hose pipe coupling heats up and melts -  losing drive between drill output & Brown Pestell motor shaft…. ie required torque is substantially higher - almost like a dead short??

Did I screw up the testing – or is this how it should be (it was contrary to what I was expecting I must admit!?). 

Is this why HAWT's are often designed for 48v – higher cut in (rpm's) required - but pushing the resultant current into batteries gets easier – requires less torque from the turbine / blades??




Steve – hi – yes I'm definitely in the “need a daily fix” camp now!!!  But I really do enjoy trying to understand / learn / find the basic principles to this sort of project.  I find it satisfying to be able to go “oh ok I can see why that happens….cause it helps with : I wonder if I tried this – would it be better / worse” 

I agree – conservation is always cheaper than production – the former “only” requires changes in habits – the latter requires…..well this touch of madness!!!

I will try that trick of connecting the battery when the turbines running tomorrow – no wind today;….and thanks again


Gee

[Norm]

Norm – hi – thanks for the additional follow-up – just being trying out the different voltage batteries…..  If my independently calibrated forearm torq'O-meters are giving true RMS readings then things are very curious indeed and not what I expected – unless I screwed up the “tests”:

Ah ha ha ! the moment of truth !

This is why ....when I made the first  pedgen 34 inch wheel driving a 2 inch wheel on an Ametek
things were crazy pedaling 60 rpm into a 12 volt battery and like pedaling a kid's tricycle with the
front wheel off of the ground about 10 watts.
present PedGen: 1:20 ratio charging a 12 volt battery even standing on the pedals can maybe
get 35-40 rpm and 30 watts peak.....
Now 2 -12 volt batteries in series....whole different animal....60-75 rpm .....95 watts peak..
Just wish you could experience this for yourself someday maybe.....it's hard to describe....
you have to actually experience it for yourself!
Using my Mains Variable Speed Drill:

Yesterday - can get 5A into 12v lead gel with enough torque and hold upto max speed (drill windings give out a whiff of “we don't like this smell”!!)

Today can get ~ 9A into 2x lead gel in series ie 24v  and hold upto max speed - torque feels as if its less and the whiff of drill windings frying seems less pungent!!

However, into a 6v lead gel can get in 3A fairly easily but as speed goes up - extremely quickly torque goes sky high, drill windings complain pungently , forearms give up and the nylon hose pipe coupling heats up and melts -  losing drive between drill output & Brown Pestell motor shaft…. ie required torque is substantially higher - almost like a dead short??

Did I screw up the testing – or is this how it should be (it was contrary to what I was expecting I must admit!?). 

No it's exactly what I expected   it's a crazy world of compromise....change one thing just a little bit and everything changes !

Is this why HAWT's are often designed for 48v – higher cut in (rpm's) required - but pushing the resultant current into batteries gets easier – requires less torque from the turbine / blades??

Well partly ....but mostly I guess requires smaller transmission wires.
  Norm 




Steve – hi – yes I'm definitely in the “need a daily fix” camp now!!!  But I really do enjoy trying to understand / learn / find the basic principles to this sort of project.  I find it satisfying to be able to go “oh ok I can see why that happens….cause it helps with : I wonder if I tried this – would it be better / worse” 

I agree – conservation is always cheaper than production – the former “only” requires changes in habits – the latter requires…..well this touch of madness!!!

I will try that trick of connecting the battery when the turbines running tomorrow – no wind today;….and thanks again


Gee

[Madscientist267]

The 6V 3A vs 24V 9A thing is most likely the elusive 'matching' issue.

That opens a whole new can of worms that someone with more direct experience with the windmills can address better than I (being a primarily solar type myself)...

I'll take a short stab, and say that the basic premise is that at a given torque/RPM, the power input is in a different part of the genny's "curve", and this curve more or less translates into the unit's efficiency at different operating voltages.

You are right in questioning the basic idea that what you see appears to be incorrect on an immediate level. Pure logic would imply that it would be able to generate the most current at the lower voltages, but there's more to it than my simplistic explanation, once again, so I defer.

If I had to give an analogy, think of it in terms of say, the everyday car engine. The engine is capable of producing a given amount of horsepower at a given RPM. Let's say 5K RPM is what this imaginary engine is rated for, at 100HP.

At 500 RPM, it will barely generate enough power to keep itself running, and at 10K, it would be in danger of flying apart.

The genny has a similar thing working for/against it, and has a "butter zone" that it will perform very well in, and likewise a set of ranges where it's just not practical to design the "gear ratios" (analogy=system voltage).

Sounds like yours is geared toward the 24V range at the very least, as it is currently wound.

There are ways to find the basic curve by comparing known RPM and/or torque inputs to the output from the genny into a known load. You'll need something that won't change it's value very much over a wide range of power input to calculate this with any accuracy. That can be tricky.

If all else fails, and you have 6V batteries of equal sizes, all known to be in good shape, you can increase cut-in by 6V increments and log the results over different RPM/torque ranges to get you closer; better than nothing. Just remember that as batteries charge, they get 'loose', and will throw your numbers. You will have to watch both voltage and current (and ultimately calculating wattage) for your measurements to be meaningful.

If you have the means to also calculate how much your drill is using at the same time, you can also learn more about the efficiency of the overall "system".

Like I said, someone else can surely grab hold of this and run with it better than I can to get you where you want to be.

Steve

[oztules]

I completely don't get it at all.

For me something is terribly wrong ............ for generators.... torque is amps........ volts is revs........(generalization)

If we get very little torque at open circuit, but max volts, and it gets hard to turn when we load it up... this relationship still works.

When you can have less torque for more amps....( regardless of voltage ... thats a power problem), all bets are off for me.

I understand the torque to be an interaction of magnetic fields. When we have no current flowing (open volts), we have no magnetic field developed by the stator.... no MMF to oppose the main permanent field.... so easy to turn.

When we draw current from the stator, then MMF is set up proportional to current running within the stator. This opposes the rotor, and we feel drag as we try to turn it.
If this remains true, then the more current we draw, the more torque will be needed to overcome the repulsive force of the stator to the rotor.

The only time I see this changing is when the opposing MMF degrades the main field (permanent magnets) so that less flux links the coils in the stator, and at some point we cease to make any more current as we cease to link all the coils...... Even if we spin it faster....we are  current limited from  armature reactance.



something is wrong here (to my way of thinking anyway)




................oztules

[Norm]

Oztules,

When you can have less torque for more amps....( regardless of voltage ... thats a power problem), all bets are off for me.

If you have noticied ...
the speed of the drill isn't really specific.....how much faster is that drill going
when it's charging 9 amps?  as he said:
Today can get ~ 9A into 2x lead gel in series ie 24v  and hold upto max speed - torque feels as if its less and the whiff of drill windings frying seems less pungent!!
Like what he needs is a tachometer......so he can see what rpm the drill is actually turning.

None of us are 'getting it' not completely....not even Gee....because he needs a little bit more
equipment to test with....probably a Tachometer and a Pronybrake....(he's becoming addicted
so I think he'll have all of these and more in time...LOL )

Fun fun fun !

Norm.

 

[Norm]

I think your drill still isn't really in the right range now try 30 and 36volt battery 'bank'
....if you haven't already.....

Norm.

[Madscientist267]

I agree with the torque/amps - RPM/volts thing, and almost mentioned it myself, but didn't want to add more confusion.

There's clearly something counterintuitive about this, but matching is where it leads me.

The other possibility is that the loads are not as consistent as math would have us believe. 3A into 6V and 9 into 24, I agree are not in line with general consensus. But if that single 6V is weak (in terms of health) and is presenting a high impedance, then it makes sense that less current would flow. This of course assumes that the voltage of the battery is not being monitored during the test (which I suspect is the case; the actual CTV wasn't mentioned, or I missed it somewhere  )...

If that battery is part of the 24V chain where the 9A is showing up, then all bets are off as far as that goes. The maximum current will only be as much as the highest impedance cell allows to pass, so the current would still be capping at 3A.

So, that being said, I think it may be one of those "can't short it cuz it runs away" kinda deals and the genny is letting go at the lower voltages... ?

I have no idea really, but these are some of my thoughts.

Steve

[Norm]

Yeah ...Steve...lot of variables .....compromises, but still things work ?
Like I take 10-14 Ni-Cad batteries (12-13.65v ,2.6 amp/hr)....put each one in series
with a 12 volt deep-cycle 75/amp. hr. SLA....pump 5 watt/hrs at a 30 watt/hr
average rate.

The Ni-cads voltage comes up from varying voltages of  12-13volts....while the SLA
starts out at 12.5 and gradually increases to  13.6 as I fully charge the Ni-Cads every
day after 2 or 3 days the SLA is fully charged ....so I have 1 cup of coffee from my
12 volt coffee maker.

So the whole bunch survives in spite of variables....Right?

Norm.

[wadlands]

 Hi guys – I've also been scratching my head and trying to get the little grey cells to line up and I think I can get to mental grips with half of it so to speak; and it does bump into what you, Steve, referred to as the “genny's “curve” etc:

Using the dialogue and suggestion from the from the WindyNation threads to “Understanding Motor Characteristics” at http://lancet.mit.edu/motors/motors3.html#power for the motor Torque & Power vs Speed chart. 

I followed the suggestion to consider its mirror reflection as the Torque & Power Vs Speed chart for a wind turbine.  At the same time translating Torque Vs Speed  into Amps Vs Volts for the turbine – the numbers in the charts are of course make believe but I can now visualise it (it helps me!!) in sort of four parts:




Where I get to first is that at a particular windspeed, after all the conversion efficiency losses from turbine and generator – the complete unit is able to generate some level of power (watts / hp etc).  Then for a given load (ie particular battery 6v or 12 v or 24v) the complete unit will have a sweet spot / butter zone which is the maximum amps it can deliver at an optimum voltage (rpm) – which if you've got the turbine design correct is also the cut-in voltage. 

Secondly, from the chart then I would expect if the wind now speeds up the rpm will go up but the amps will drop into the battery cf the optimum sweet spot.  If the wind slows down then the amps will also drop below the sweet spot into the battery - until the volts also drop to below cut-in, in which case amps into the battery will be zero.

Thirdly, as the battery takes on charge it represents a different load to the turbine and essentially a new chart is required – ie the sweet spot moves – probably to the right

Fourthly, different voltage batteries (6v, 12v 24v) have their own charts for that particular turbine at a particular wind speed???

Oztules – hi - yes I'd also got to the torque is amps & volts is revs – hence my attempt to “chart it”  and the results I got (from an extremely crude test) are to me also intuitively wrong.

And as Norm you suggested – I had also come to the conclusion that my forarms as a torq'O meter are far too crude and as a minimum I'll need to monitor the rpm's of the motive force (drill) more accurately; as well as measuring its V&A draw under load to make better sense of it.

………….like all projects ………..here's the domino / cascading  effect!!!!…..have to dig out the PWM drive circuits , finish that tacho I was always going to build……serves me right for wanting to understand and learn more.

And to paraphrase Scott's famous words (but with a much more lively outcome) : "I may be some time”


Gee

[Norm]

When all is said and done you may find it more convenient to just have a WattsUp meter
or something similar....and a tach on the motor......
  When the wind is blowing and you are charging your battery
and the WattsUp meter tells you you've put 30 watts in and you've had it
running for an hour.....
   Can make some pretty neat curves by checking every hour.
.....different days a steady 8 mph wind for example...

at least that's what I'm planning on doing when I get a WT going again !

I used to use a threaded rod for a rpm guage put it in your drill chuck ....
How many seconds it takes a nut to travel from one end to the other on a 36 inch rod?
So many threads per inch....Crude but it works.

Course you may need an extra pair of hands LOL !

Norm.

[jaysicle]

Hello,

After noodling with the the cordless, then the mains drill, then the drill press (chewing drive belt a bit as A's increased) - I mounted the device (AF generator) to my excercise bike because I decided that I could produce more short term measurable torque with my legs.

I picked up an accurate tachometer for about $15 from E-bay very similar to this one...



...and started riding and (graphing) into a known resistance - (8ohm power resistor + generator resistances + wire resistances - prior to trying with battery).

The battery clamping voltage / generator cut-in was given to me by ghurd, and is KVL (Kirchoff's Volage Law).  Riding into the battery gave me reason to change gearing to optimize RPM vs. Ride resistance vs. Amperes out so that I didn't feel like I was climbing all day. Ride longer at a little less current = more Amp hours resultant.

I don't understand the 3.6X power delta with the same drill into different batteries that you are experiencing, maybe limit variables and try it again with a known power resistor - or maybe a patent is on the visible horizon.  

[wadlands]

Norm – I'm unclear are you putting a pack of 10-14 cells in series with a 12v SLA – ie now a 24volt battery assembly and charging OR just adding one NiMh cell in series with the SLA and changing a nominal 13.2v battery assembly?

Yes – I was thinking of something like a WattsUp meter  - I have an Astro Flight watt meter I use with my RC models and motors. ….your threaded rod rpm guage – I thought I was trying to keep it simple ….but you set new horizons here!!!

Jaysicle – hi – that laser rpm meter – definitely will look into – thanks for the tip.  And I don't understand the differences I got – may just reflect the crudity of the tests and will redo when I can control the parameters a bit better – especially the motive force; a mains drill with a trigger control does not lend itself to controllable rpms!!

You've cornered in some way what I'm trying to understand – to manage the torque required (down) for the high amps you  were getting , at the muscle power that you'd like into your chosen battery voltage – you used gearing to manage the amps to the right level with your generator.





Where I'm trying to get to (and I think Norm you have already got there??) is : given my turbine generator combo and the rotor rpms that it achieves in the available winds – then if one starts with a nominal 12v battery would I be able to harvest “more” electrical energy by choosing a nominal 10v battery or 14v battery (in the same state of discharge).

From reading some of the other forum posts (and if I grasped the content correctly) in HAWT design the approach is almost for a given wind speed (range) & cut in voltage the variables you choose are either the alternator to design effectively OR the prop size and pitch effectively (ie turbine), OR both to get the best extraction of electrical energy into your chosen nominal battery voltage.

I'm just trying to come at it from the “other side”: the spread of very average winds I have to deal with is a given, I will do the best I can to maximise the efficiency of my VAWT while keeping it simple to construct, I have a 2 or 3 different types (& volts per rpm) motors I can use as genny's.  So the variable that I have left to play with is – what battery (voltage) pack should I hang off it at the end to maximise the electrical energy extraction.  Perhaps I will need to change the nominal voltage of the battery pack hung off the genny at certain step changes of rotor rpm (wind speeds) as well?

To me it just seems that I am choosing a different variable out of the set of four : 

live in a very windy area, alternator design, turbine blade design and battery “bank” voltage

that are available to maximise the electrical energy harvested. 

There appears to be a lot written on the two & three but not much on the fourth – understandable cause it would be a totally inappropriate to a big HAWT on top of a big mast in a high wind area.

Gee

[Norm]

Norm – I'm unclear are you putting a pack of 10-14 cells in series with a 12v SLA – ie now a 24volt battery assembly and charging OR just adding one NiMh cell in series with the SLA and changing a nominal 13.2v battery assembly?
 I have LED lamps that each one used originally 3LEDs, 3 of these $1 push button lights  put in series with a 100 ohm resistor
and hooked to a 2.6 amp/hr. 12 volt NiCad battery pak. (10-1.2 NiCad cells in series = 1 set) and 2 sets in parallel make 1 pak.
 powers these 9 LEDs.
I've got 5 of these so far as nite lites....they're on all night for about 6 to 8 hrs. in the morning they are down to anywhere from 11
to 12.5 volts from 13.6 volts.
Okay....I start charging these Nite Lite batteries thruout the day one at a time in series with this 12 volt 75 amp/hr battery that
may anywhere from 12 volts to 13.65 volts at the beginning of the day (depends on when I used it to have my last cup
of coffee)
I do this routine of first 2.6 NiCad batt.pak and the SLA 12 volt in series for 5 watt-hrs., second 2.6 NiCad batt.pakand the SLA. , .....third & SLA etc.
for a total of 50 watt.hrs per day. Yes – I was thinking of something like a WattsUp meter  - I have an Astro Flight watt meter I use with my RC models and motors. ….your threaded rod rpm guage – I thought I was trying to keep it simple ….but you set new horizons here!!!

 Gee

[Madscientist267]

I knew some others would have a more firm understanding of the exact dynamic involved.

A couple things come to mind on the other stuff -

You mentioned the 'trigger chopper' in the corded drill - Very true, it's good for 'close enough' when you're turning a drill bit, but even though under load it can hold a fairly steady RPM, the ability to fine tune is crap. Just the nature of the beast.

For this, and where a drill motor (or any other 'universal' series wound motor) is involved, a VARIAC is invaluable. They are a little more rare than they used to be, but short of a full range (pronounced 'high end') variable power supply capable of 0-150V @ several amps, DIY or otherwise, it's really the best way (IMHO) to tame such a motor. As long as the load doesn't change (which during tests it wouldn't need to), you can dial the RPM right on in to exactly where you want it to be and hold it there. If the load does change, just adjust to suit.

They're not entirely cheap, but well worth the money just to have around for such an occasion.

Note that this doesn't work with any other kind of motor. You'll probably just make heat and some humming.....

The other thing I think of as worth mentioning is that for any kind of scale (and really even just in general), the genny is the device that gets the 'dialing'. While it is entirely possible, and may even seem practical at first glance, to dial in a battery bank's voltage to within a couple of volts of the genny's natural cut-in, this line of thinking will turn on you a little bit on down the road, when you go to use the energy you've produced.

Almost everything is designed for 12, 24, (some) 36, and 48V nominal banks, and don't tolerate being much outside the normal operating ranges for the specified voltage. Even if you're close, but still not on, ie 22V bank on a 24V inverter, it will not play nice, and (in this example) will cut-off early, because it thinks that the battery is too low too soon, while there would still be usable power left in the battery.

If rewinding the genny isn't practical, your next best bet is what's called a 'buck' converter (if the butter zone is above the battery voltage) - this converts the surplus voltage into current at the lower voltage of the battery so that the genny is better matched to the bank. A variant of the basic buck converter is called MPPT (stands for Maximum Power Point Tracking), and uses a 'brain' to find the sweet spot for you so that regardless of the output from the genny (within reason), it will provide as much power to the bank as possible. One caveat - they are quite expensive. Not 'tinkering' equipment - I don't even have one, and I've been in this for a while now. I use a buck converter (that I built with the help of Commanda and others) from time to time, but a full blown MPPT is a little out of my reach ATM... 

For experimentation and learning purposes, if you want to play around with the 'in-between' voltages, this is fine, just keep in mind that they are not standard and you will have hurdles down the road to work around when it comes time to use the juice.

Other than that, sounds like you're gripping the ideas rather well. As the saying goes, "Having fun yet?" 

Steve

[wadlands]

Steve – hi – thanks for this 5 star follow-up!!

I had been so used to using the battery powered drill for my initial bench tests that I totally forgot about using the Variac for the mains powered drill…too close to the problem.  I have a  240v 8amp Variac which will be just the ticket for controlling rpms finely and with jaysicle's laser rpm meter idea ….I'm more than halfway there to better quality bench tests.

I understand the standardised 6/12/24/48 voltages and downstream needs of inverters etc tied to these standard multiples.  My experimentation is only intended at the charging end – I use 8000mAh NiMh D-cells to make up packs for some of my RC boats.  Having this flexibility of adding cells was what got me thinking about how to load the genny “better”.  Once the cells were charged they would be regrouped into the standard 6 or 12volt combos that I would then use around the house – I'm just trying to think of my approach as “energy harvesting” rather than major battery bank charging with inverter outputs etc.  Bit like a small backyard “vegetable patch” rather than a large “agricultural farm” …. using food production analogies!!

I will follow up on the Buck Converter & MPPT reading (had come across MPPT when I was tinkering with solar cells – before I got distracted with wind power!!) and I had tripped across some circuit design & build by Commanda in some of the forum posts – will now be more motivated to digest and understand this better.  Much of it is for me about “gripping the ideas” and I am enjoying it, I like to be able to get to the core principles of whatever I'm doing ….that'sjust me!!! – I think I've learned a lot so far with my small scale attempts. 

Currently planning to make the existing wooden tower more stable – with outriders at the bottom – so I can leave it unattended.  Planning to monitor what current v rpm the stepper motor produces with this Mk2 turbine into at least 6v and 12v lead gels.  Will need to make a better anemometer than I have at the moment which is too directional (really just a hand held device)…need to knock up a cup type and stick it on top of the tower.

Gee

[Norm]

Suppose you have a small widmill that can't quite get up to speed ...only puts out almost enough for
cut in at 200 rpm.
If you were to have a small reduction gear to hoist a weight.
For example a weight x lbs. is hoisted up x No. of feet. takes an hour....
then disengaged from the windmill and engaged to the generator and unwinds in
10 minutes producing 6 times the power (disregarding friction).
I've never had a windmill hoist a weight before....but I have done the unwind part
on a real small scale....and it does work.

Norm. 

[wadlands]

Couple of nice windy days - so finally managed to get some decent current into battery measurements with the stepper motor and this Mk2 turbine:



I'm pleased with the results at a max of 440mA in 15mph winds.
Previous best with Mk1turbine was 480mA but the Mk1 & stepper would only start turning in winds of 12 to 15mph.

Objective of Mk2 was to get the turbine to have enough torque to start turning in lower winds and cut in earlier - objective achieved!!!
May only be 20mA but it cuts in at 5 to 6mph and delivers current all the time - nice baseline for the Mk3 turbine.

Objective of Mk3 turbine is to have more torque still, without losing rpm's - so that it can deliver more amps into the battery - here's hoping....time to start building Mk3



Hi Norm - intriguing concept that!!!

Gee

[Norm]

Nice to see everything coming along.
Remember that a little charge in a little battery is
better than a little charge in a big battery  tried the latter
a couple of times.... waste of time.
been working on a nice 6 hp. self propelled lawnmower the
last few days just isn't getting the gas....thought I had it today
was a definite clog....fixed it ...but still doesn't run....Gah !
...I'm stumped carb isn't a regular one either.....
Norm.

[jaysicle]

I understand the standardised 6/12/24/48 voltages and downstream needs of inverters etc tied to these standard multiples.  My experimentation is only intended at the charging end – I use 8000mAh NiMh D-cells to make up packs for some of my RC boats.  Having this flexibility of adding cells was what got me thinking about how to load the genny “better”.  Once the cells were charged they would be regrouped into the standard 6 or 12volt combos that I would then use around the house – I'm just trying to think of my approach as “energy harvesting” rather than major battery bank charging with inverter outputs etc.  Bit like a small backyard “vegetable patch” rather than a large “agricultural farm” …. using food production analogies!!

I think that is a brilliant way to really truly learn this stuff. - And I say that as someone who is continuously learning about it - usually just when I think I have it covered. 

[ghurd]

The numbers still sound out of kilter to me.
Only thing I can think of that makes the slightest bit of sense is 'slow rectifiers', and I don't think that makes very much sense either.

Any chance of replacing the rectifiers with Schotky diodes?
G-

[wadlands]

Hi Norm – self propelled lawnmower….remote controlled!!! Or just means you don't have to push it!!!

It was the idea of getting a little charge (ie in low winds) into a small battery that originally got be trying out the 6v / 12v / hand made low voltage pack idea.  But these initial tests I need to repeat in a more controlled manner.

I also did follow up on your idea, Steve (Madscientist),  of linking the battery once the turbine is running.  Tried that with 6v, 12, 18v, 24v and 4x1.2 NiMh cells ie 4.8v.  and definitely see the drop in rotor speed happen – but happens more dramatically for the nominally lower battery voltage packs.  Didn't get to take any current measurements as the wind was only happening in mini-gusts.  But definitely got the feeling that with say the 4.8NiMh and 6v lead gel cut-in wasn't really happening at much earlier wind speeds as the rotor was spinning itself at much lower relative rpm's ….trying to deliver the current?  I'm going to repeat these “tests” on the turbine when I have a better way of recording the amps into the battery & wind mph / rotor rpm.  At higher battery voltages 18v and 24v – yes the wind had a much easier time to get the turbine spinning earlier and faster until some current would flow….from these crude tests I appear to get the “better” delivery of current into a battery at 12volts.

I got to thinking about the “problem” with the smaller batteries and the additional torque required from the turbine:  At a particular wind speed the turbine extracts and delivers a certain amount of energy to turn the stepper motor as a generator.  If I choose a low voltage battery, say 6v then the excess energy tries to be delivered as amps into the battery.  But these “extra” amps are also flowing through the coils of the stepper on their way to the battery.  This current creates an opposing magnetic force on the rotor of the stepper motor….ergo I now need more torque into the lower voltage battery – although it cuts in at a lower rpm???  Have I got it right in my head now?

Higher voltage battery, yes will cut in at a higher rpm, but from the total energy in the turbine there will be correspondingly less converted into amps – and less creating the resisting magnetic force in the stator – so the turbine gets away with the torque its already delivering??

ghurd – hi – the rectifier bridges I only used when I was testing out the various combos for the CW multiplier. 

My different size battery tests and current V torque are just with a high volts/rpm DC motor (the green Brown Pestell) and I only use a 1N5819 1A 40V diode which I think is Schottky. 

The rectifier bridge for the voltage multiplier used on the stepper motor is made from separate 1N5819 diodes.



Gee

[wadlands]

Just a short update – starting cutting pipe blades for Mk3 – going to make a four stager!!! (madness creeping in now!!) bit larger diameter than Mk2, but with each stage a bit shallower. Overall height should be about 4ft.  Intention is to see if it starts easier than Mk2 and to see if has a bit more torque as well.

In the meantime got my NEW improved cup anemometer up and running – just need to calibrate rpm's against wind mph's now. 



Also got a bargain £2 cycle computer to use for monitoring rotor rpm's – showing about 100 rpm on readout (if I've put in the correct conversion factor) – max I got today was about 120 rotor rpm in 8 to 10mph winds while delivering about 40 to 50mA into 12v lead gel…..not much in the big scheme of things – but still – “One Small Step” for me!!




Gee

[ghurd]

"got a bargain £2 cycle computer"
"just need to calibrate rpm's against wind mph's now"

Don't beat yourself up over it.
The RPM : MPH is not linear.  Nothing you can do about that.
Magnet to sensor distance is picky.  If it reads obviously incorrect at very high or very low RPM, adjust the magnet to sensor distance.

Sometimes good enough is good enough, and this anemometer is one of those times.
G-

[Norm]

I made an anemometer once from 6 of those plastic
dome shaped drink cups with a hole in the top tape over
the holes.....long arms and 6 cups goes very slow so
you can easily count the revolutions pretty accurate in a
3-15 mph breeze/wind.
 Figuring out how many turns it will make in X mph is a
simple straightforward math problem.

I have also used a cycle computer....using a psuedo
wheel size (especially an anemometer with large diameter
 RPM:MPH can be almost linear.....well psuedo linear 

Norm.

[wadlands]

Hi ghurd I agree “good enough…is good enough” and I have to keep reminding myself the point of it all is to get amps into batteries!! 

So I'm trying not to get lost in the woods with over analysis …but I like to get a feel for things, eg it was very satisfying to see that the rotor was doing 120rpm – which I believe is quite good for a savonius type?

Norm – yes I was going to use plastic cups for the anemometer but then came across this “proper” anemometer plastic cup & hub cheap – so I cheated!!! And saved all the agro of fabrication & balancing.

To get to a “ballpark” figure of  wind mph from anemometer rpm I was going to use:

Convert anemometer rpm to hertz
Multiply by reed switch sensor radius (inches) from cycle hub centre
Divide total by 17.6 (conversion from inches per second to miles per hour)

Answer = anemometer rotational speed as mph – which should be the wind speed in mph?

What formula do you use to get from rpm to mph?


Gee

[ghurd]

Start with the cube root of Pi multiplied by N, figure how it relates to C when a 3 dimentional universe is implied, then... 

"reed switch sensor radius"
No?  Could be I misunderstand.
Radius to the center of a cup, and a bit more.  Maybe use the radius to the center of the cup, plus 1/4 of a single cup's diameter?

I calibrated my easter egg & cycle computer anemometer with my factory made anemometer.
(I used things I had on hand, so it was not cheating)
It was frustrating.
Low wind was the worst.  I suggest not even considering measurements in winds below about 8 or 10MPH.
G-

[Norm]

Gee,
Being the math illiterate that I am, I take the easy way for me,
I just * hot glued the cups to a 20 inch bicycle wheel at the time.
The formula was already figured out with the instructions that I got
with the digital bike speedometer.
The digital thing can tell me the average speed, distance traveled after
reset, time of day, etc.
The bike wheel rode the wind .....well actually it was a VAWT with a TSR
of 1....theoretically.....

Glen....BTW are all brands of duct tape the same quality?
the brand I used from DollarTree wasn't/isn't ....I used it to
hold the windshield rubber strip in and after about 2 weeks the
plastic biodegraded leaving only the 'gauze' and adhesive.....hmmm?

Norm.

[Norm]

Start with the cube root of Pi multiplied by N, figure how it relates to C when a 3 dimentional universe is implied, then... 

"reed switch sensor radius"
No?  Could be I misunderstand.
Radius to the center of a cup, and a bit more.  Maybe use the radius to the center of the cup, plus 1/4 of a single cup's diameter?

I calibrated my easter egg & cycle computer anemometer with my factory made anemometer.
(I used things I had on hand, so it was not cheating)
It was frustrating.
Low wind was the worst.  I suggest not even considering measurements in winds below about 8 or 10MPH.
G-

.....with longer and more and larger cups instead of 'easter egg cups you could probably measure 4mph or less ?

[TomW]

Glen....BTW are all brands of duct tape the same quality?
the brand I used from DollarTree wasn't/isn't ....I used it to
hold the windshield rubber strip in and after about 2 weeks the
plastic biodegraded leaving only the 'gauze' and adhesive.....hmmm?

Norm.

I am not Glen, nor do I play him online but...
A couple years back I found some (mispriced @ $1.25 each?) rolls of black "Gorilla Tape". Bought all 6 rolls they had on the shelf. At the time it was just cheap for duct tape.

Some has been outside for a couple years with no signs of deterioration and even the part exposed to sunlight looks like it came off the roll yesterday.

Seen the cheap grey stuff fall off in a few weeks time.

Down to a couple rolls left but it is on my resupply list.

This stuff survives outdoors quite well and as tough and sticky as any tape I ever used.

Tom

[wadlands]

....and the cry went out More Duc k Tape waiter......

ghurd - I meant circumference ie distance travelled in one revolution at the radius of the reed sensor. 
But I also see now that actually it should be the radius of the cups from the centre point of the axle and the distance (circumference) that they travel in one revolution.

Gee