Wind Turbine Regulators

It may not be worth it.

For permanent magnet designs one option is to lower the cut-in-speed and install a field weakening coil. However, for direct driven neodymium magnet generators (below 3-500 RPM), the energy consumed in weakening the magnetic field may offset the extra power produced. (slip-rings also require maintenance)

Another option is to increase the cut-in speed and hook up a boost converter to extract the power available below cut-in.

At the heart of the issue is without control, you can only get about half the KHW out that you could be getting due to the cubic relationship between wind speed and power. There is no simple way to match an unregulated generator to a battery. Whether boost or field weakening (or both even) is cheaper than simply installing another turbine will depend on your capabilities to manufacture it and what wind speed data you have.

While a variable air gap sounds easy, building it is another story.

At the heart of the issue is without control, you can only get about half the KHW out that you could be getting due to the cubic relationship between wind speed and power. REPLY That is what I thought. With a lower cut-in speed you get energy sooner, and then a controller like an MPPT will prevent the excessive high voltage from boiling the battery. Installations such as mountain top repeaters often have multiple smaller wind turbines instead of one big unit. Whether this is for redundancy or to get more power from light wind conditions I don't know. Maybe both. PM generators have lots of advantages but last year when I was looking for such a generator in the 4kW size I could not find one manufacture (at a reasonable price) with any sort of regulation. One manufacturers claimed they could get me regulation but wanted another $1000 on top of a steep price. Final price was twice what a conventional genset would cost I was looking for a DC genset because the sole reason for the generator was to charge batteries. Why go through a double stage of conversion if a single stage would suffice.

Well, I am not electric, electronic nor mechanic engineer (because I am Systems Engineer) but if widening gap between pole pieces and magnets would solve problem of wind speed/rotational speed versus electrical output, then I think I have solution for You, provided I understood nature of system and requirements.

I believe that Your intention is to increase load with speed of wind by making gap less while starting with widest possible gap?

Now, is it possible that both rotor with its magnets be made conical in profile and have matching conical cavity inside of stator? I think there should be no problems in producing such alternator.....

If this is so then simple system of levers pulled away from axle by centrifugal force mounted symmetrically in circle on a ring (actually there is two rings and two sets of levers where free ends of levers are joined and on this joint a weight is fixed) and additional rings to lead axle when moving, then ring that would not rotate but be free to slide over axle and spring(s) that would push back rotor into starting position.

There should be a gap between axle of Elise and axle of rotor, that would be smallest when speed is highest or even completely joined when two rings with levers come together if some sort of radial ridges is made on rings (or flanges) that would mesh together like gears and thus provide stronger torque transfer in highest speed of rotation......

I dont know by which mechanism was working those alternators with variable gap You were using before, but perhaps this centrifugal system can be used to change gap in those alternators, so special alternators need not be built..........

I hope this would help, and sorry that I lack proper technical jargon, so even if my description is little clumsy, I think it would still be understandable.......

That looks like a good idea. Using a spring opposed fly-ball governor to position the tapered rotor inside the tapered stator should make for an relatively easy automatic rotor to stator gap adjustment. The hard part would be getting the linkage/spring ratios correct but it would use little additional power and that frictional to provide the gross starting load regulation in a system like this. It would allow the generator to spin freely being lightly loaded in light winds, so starting would be easier.

Another shunt regulator could be used to add load to keep from over charging the batteries and prevent overspeed during high winds or when the batteries are fully charged. The shunt regulator would only be active when there is surplus generation so it should not put an unnecessary load on the system when power is low.

Multiple generators is the easiest way, switching on and off whenever suitable.

Generators for use in cars or trucks range from 1 to 10 KW - production cost is from 50 to 150 $ a piece, selling price a factor of 10 higher.

Variable magnetic field in a PM generator: not really difficult, coming in some weeks with a tutorial on PM generators I am preparing.

RHABE

asked if such a controller could be adapted to a wind gen which has variable wind affecting the turbine.

I have been told that the minimum start speed of any given wind turbine is dependent on how much of a load is placed on the alternator being turned by the propeller.

I'd agree with exception of the wind speed being a major contributor. For example if you configure with the minimum load being about that which the average low wind speed could produce then you're on the platform and that MPPT may be functional. Conceptually your unit may be more effective if designed for the conditions present.

What do you think...

Conceptually your unit may be more effective if designed for the conditions present.

What do you think...

I don't follow your logic. The conditions present is variable wind which is why I am wondering about a regulator that can handle variable conditions.

I believe Elnaw was thinking about optimizing system for speed of wind that is most frequent at site of wind power generator.

My Wind Power stations optimize Wind instead :-))

Still they could be adjusted for stronger wind if such is prevalent, but then in weaker wind they would not work...........

What I would do is to base capacity of particular PS on speed of wind that is most frequent at site, ignoring weaker wind and stronger one (because system regulate wind, stronger is not problematical) but with my system capacity is fixed, and on speed of most frequently occurring strength of wind would depend whether it would be 1, 3, 7 or 10 MW unit installed.

But then if 1 MW units can work 70% of time, 3 MW 50%, 7 MW 30% and 10 MW just 10%, then it is better to install seven 1 MW units than one 7 MW unit, dont You think? It would cost more, but produce nearly twice as much electricity, and if generator could also handle some range of lower and greater speeds, then we would catch almost all there is to catch, no?

Since my Wind Power Stations dont produce much turbulent flows, and turbulent flow dont matter to them at all as they would work anyhow, they could be packed much more closely together, which means more energy would be reaped from same wind period too.......

Anyhow, I hope soon I would be able to reveal my design when I submit Patent applications form, and then you shall understand this riddle I set You about optimizing the Wind :-))

Hendrik

Sory, you have it backwards I think. The situation is this. Many people do not fully understand how to size a wind gen. They demand a size equivalent to what is needed for an engine driven generator. Quite often I have people demanding a quote for 10kW wind gen installations. They are living in a single family dwelling, often with no kids. I try and tell them a 2kW wind gen will collect enough energy and store it in a battery bank to power their whole house by way of a 2 or 3 kW inverter. And most of that time the inverter will be running at half power. Meanwhile the wind also blows overnight when they are not using any power. So it still collects energy.

So what happens is, the big 10kW windmill cannot start in light winds. Result zero energy collected from wind. Now they complain the "stupid installation is all wrong".

Yet; if you were to disconnect the big wind gen completely from any load, the light wind would often turn the prop, but slowly. If you were to place a small high impedance load across the output, you would get some voltage and small current. But not enough to charge a battery bank.

Photo voltaic installations have a similar problem during early morning and late night when sun angle is low and light is weak compared to noon.

For PV installs the solution is an MPPT controller. I was asking if a similar kind of controller was available for the wind gens. According to SW Wind Power tech support there is no such thuing.

I am familiar with a number of such failed installations. If I could provide a better controller, some of these installations could be salvaged. Hence the query.

Dear Elnav,

Nobody is having it backward and we are both right, because we are speaking of different things when use of electricity is in question.

You want to store it to battery while I would send it to Grid as soon as it is produced.

I believe theme was how to optimally use resources at hand, to be able to produce as much electricity as wind speed permit, with aim to eliminate expensive frequency stabilizers and other electronic that should be necessary to compensate for variations in wind speed...

You are talking DC and we discuss AC production, IMHO.....

I agree with You 100% that people dont understand opportunistic electricity production is different than >>on demand<< production where energy is not stored because production is equall to demand.

Yes, higher capacity units have higher minimum wind speed to start. Now, if I did not mix threads, You asked if there could be alternator with variable gap, and I proposed possible solution with conicall rotor and matching stator, where rotor with its magnets can be moved in with higher speed of rotation, which should enlarge load so range of Wind speeds could be utilized.........

I pointed out that if weak wind meet also big gap between magnets and coils, then rule of diminishing returns would show itself in very weak electricity produced.

However, at least there would be no need to start elise by using electricity, so some would be saved.

Now tell me: would it help You if You would have different elise that can use wind more effectively and need not be stopped in strong wind?

What do You think of another idea of serially connected batteries where each should have its system for limiting strenght of electricity received and system to switch it off the line once it is full (just like some are mentioning >>dumping<< of load when battery is full), and last in the line should have usuall system that preclude damage to battery instead of next one? I would say some system with transistors could be made to effect this.....

Regards, Marijan Pollak

Hendrik wrote: You are talking DC and we discuss AC production, IMHO..... This the first time you have clearly said your design focus was grid tie application. My application is as you realized, purely OFF GRID. Very different systems with quite different requirements. You speak of avoiding the use of electricity to get the turbine started whereas I was talking about how to overcome the issue of insufficient wind to drive large capacity turbines. Again a whole different situation. I am dealing with customers located where there is no grid to connect to. Diesel powered generators are now becoming so expensive to run, alternatives are being sought. Somehow I don't see how such divergent threads would fit together.

Hi Elnav,

I have turbines of new design that would work with weaker wind, if this would help You, and my type of WPS could be used also for such places, with DC, of course.

One of turbines is strictly verticall. but has some speed regulation built in. Other can work both Vertical and Horizontal, but has no speed regulation. At least it cannot break from too high speed. It is simple and inexpensive to make also.

That is the way we can cooperate, and I can sell You Productiom Licence cheaply, once I get patent rights....

Now, please, there is Hendrik on CR4, and this is not even my Nickname (Henrik14)...

Regards, Marijan Pollak

Marijan Pollak, please stop trying to sell me your new wind turbine.

I am trying to fix a problem on an existing unit. The customer is not going to just junk a brand new turbine installed less than 6 months ago.

It seems that we dont understand each other.......

If You take down Elise and put my turbine instead (NOT whole instalation) it would work with much weaker wind because of greater efficiency in using existing wind.

I guarantee at least double to triple eficiency compared to clasical elise!

Now excuse me since I am sick in last 24 hours......

" If You take down Elise and put my turbine instead " What is Elise?

I am sorry that English is not my native language, so I am at loss for words sometimes. Small airplanes use Elise to propell themselves (and of course now I remember it is called >>propeller<<). Since contemporary windpower stations use something very similar to elise/propeller, I call it that way.

Anyhow, this is head with blades that wind turn, OK?

Turbines are used in waterpower stations (hydrocentrals) and they are quite different from propelers. They cannot (in principle) be used for air since water is 10 times heavier than air.

My turbine is someting between propellers and turbines, so lets call it air turbine...

Marijan Pollak wrote:

That is the way we can cooperate, and I can sell You Productiom Licence cheaply, once I get patent rights.....

When you have something I can look at, by all means send me a PM with the details including a landed price for Vancouver, BC, in Canada.

To be honest. There is no manufacturing facility where I am. The company I work for may or may not be keen on setting up a production facility 700 kilometers away. Typically such a deal would require close supervision for the first dozen units and to be honest we would not sell that many in a whole year.

Somehow I doubt you will get very many people interested in handing over money for a piece of paper giving them permission to build a totally unproven design.

You need to demonstrate the worth of your design by building some samples in the first place. Once they have proven themselves in the field for a year or two and proven reliable then you can start to talk about production licences.

Your design has to be compared to existing models and documented as giving a benefit over the norm.

O.K.

We can have an NDA and I guarantee that this is design that anybody can make even with hand tools and it work provenly.

I designed it with India in mind where there is little technology and tools available.

CR4 ADMIN: This post was edited to remove advertising outside the Commercial Space forum. Please review Section 14 of the CR4 Site FAQ about advertising.

Agree?

Thats my take too....

I installed a video system on an offshore platform. I powered the system via solar panel & installed a wind turbine as a back up for those days when I was not able to fully uitilize the solar panel, generally when the sun don't shine offshore the wind is blowing. Both systems fed a battery bank I installed a voltage regulator on both power sources with out any problems.

Regards

I had always heard that regulators were used on wind generators. However I was quite surprised to be told by one manufacturer that regulators for permanent magnet generators do not regulate except to divert to a dump load when battery voltage goes to maximum absorption level. One manufacturer (eCycle) of PM generators said the same thing and wanted to charge extra to engineer a true regulator that would be three stage and switch to float stage if the battery became fully charged.

I subsequently checked out a number of manufacturers and was told by them it was difficult to physically regulate Permanent Magnets alternators.

What a waste! Dumping energy already produced :-((

Please read my solution and tell me what You think, is it possible?

I started from requirement of having variable gap between magnets and coils.........

No need for any electronic switching and multiple coils!

Unfortunately I have feeling that weak wind would produce still weaker electricity.

Alternatively similar system can be used to switch on and off variable number of coils, by pushing and pulling isolated pipe ( made of Novilon, for instance, which is type of plastic more resilient to wear than steel and self lubricating ) on which copper rings are mounted and isolated by plastic rings from one another, under line of contacts in pairs on opposite sides, where each switch on or off one coil in use, those switches that are in air are off, and those on rings are on, all controlled by speed of rotation itself..... To avoid situation where switches can be parked over plastic isolator between copper bands, switches could be doubled with gap equal to width of isolator band or little greater, so one switch would always be on copper band even if other is on isolator band :-))

You wrote:-

I subsequently checked out a number of manufacturers and was told by them it was difficult to physically regulate Permanent Magnets alternators.

I would be interested in such a system, purely to learn more, for no other reason.

The only way I figure such a system could (theoretically) possibly work, would be if coils were added to negate the magnets effect, using of course the output of the Alternator.

Which would usually mean having slip rings to get power to the coils, which negates the reason for having magnets in the first place......(no slip rings needed!).

The only other method would be a possibility to move the coils away from the magnets mechanically......like this?

It would be an engineering nightmare mechanically though, out in all weathers.....but no need for sliprings either.....

Perhaps it could be used for voltage control, but might be a bit slow.....

Andy, Snowmobiles have a variable diameter belt drive. this is achieved by using a centrifugal device to move the two angled side plates of the belt drive pulley in or out to vary the diameter of the contact circle . At first glance this kind of mechanism appears to be promising for doing the variable air gap. But what do I know, I'm not a certified mechanical engineer.

Sounds promising.

Do you "need" to be an Engineer?

"Engineers" are those with common sense, not necessarily ones who visited a University or similar!! I have known several Non-Engineers who could "lose" good Engineers with both theory and practise!

Some people simply could not afford the University for one reason or another......does that make them stupid? I think not.

Have a great day.

Hi,

not to move the coils away but the magnet assemblies.

These have to be located at both sides of the coils (else not at all sufficient flux density).

Take apart an old hard-disk-drive, there is one triangular coil (moving) with two sides magnets (each side one north one south oriented magnet).

So if you complete this arrangements by adding coils and magnets so that a full circular construction is resulting, this is near optimum for motor and generator use (1 phase).

Any even number of coils (minimum 6 but better 8 or 10 or 12) is necessary for optimum use of available magnetic flux.

Two and three-phase versions need two sets (three sets) of coils, magnet assembly is the same.

Moving magnets apart is difficult to realise. So think about switching of coils. If the coils are series connected then using half the coils will generate half the voltage. If the coils are connected in parallel then the current is changed by changing coil count.

More will be available as a tutorial on permanent magnet generator and motor design - pancake style.

RHABE

True, but the design I saw on the web (finished and working) used two sets of fixed coils with a moving plate with magnets on both sides, placed between the coils. In fact it was the disk of a Volvo disk brake front axle.....

But either method should work if a suitable system is worked out, excewpt that leaving coils "open" could result in exceedingly high voltages being developed on them.......some thought needs to be given there as well......feeding into a dummy load is just wasting energy, maybe a method to turn a HAWT out of wind or feather the props might be better.....

Here is a web site that has a generator that has variable resistance to wind loading.

http://www.technologyreview.com/energy/21666/?a=f

Your assumption of variable load to wind is correct.

Silvcrow I saw that announcement and phoned the company since they are not that far away in Vancouver. ( only 700 miles) Apparently this is not yet a production item. They are stil field testing ONE unit. And no; they are not interested in more field testers.

For a new install this is certainly the way to go. However I was looking for a way to salvage existing installations that are not living up to owner's expectations.

The new Air-X Breeze model apparently does something similar to what I wanted with an internal controller. But so far no one has an external bolt-on controller. Pity

Hi Elnav,

I think I have a simple answer to your problem, well, half an answer!

If you add a series resistor in the output line of a fractional ohm value you will get a voltage drop across it which will "devalue" your alternator without disabling it. Since you would wish this to be variable to be part of a MPPT control I would suggest a bank of mosfets (I bet you have quite a few of them laying around). We see this on poor installations of chargers or alternators which have too much resistance in the battery cables (too long &/or too thin).

While this is a "losser" type circuit it will not generate too much heat as at full power the mosfets will be hard on and thus dissipating little power.

How will you go about doing the MPPT control? I have no experience in this area but, If I understand it correctly the MPPT is matching the impedance of the load to that of the source. With the relatively slow changes in source output of a solar installation the MPPT can vary the load presented and detect the best point on a periodic basis but with wind it would seem rather more difficult as the variability is on a much faster time frame.

I like Henrik14's idea of the conical rotor/stator pair where an axial displacement will produce a change in the air gap. There are already motors out with this sort of arrangement.

Kind Regards

Chas

I agree Henrik's idea is good for when you have the option of starting from scratch.

In the case where a customer has already invested considerable money into a wind gen and tower installation, it becomes a case of convincing him to spend even more money in the hopes of getting something but less than full rated output. Except during sustained high winds.

Regarding your idea of a voltage dropping series resistor, I'm having a little difficulty figuring out how the whole system will react. I likely need to think about it more.

None of the MPPT regulator descriptions give details. It doesn't sound like it actually places an impedance across the output of a solar panel, but rather uses a lower voltage due to low light level and a variable DC -DC converter to juggle this into a higher voltage above 13.8V but at much less current. At least this way you get some charge curent at a voltage suitable for the battery. Then as output increases both voltage and current also increases. Now the DC-DC converter regulator adjusts to keep the voltage down to 13.8V but increases the output current as much as possible.

My example was of necessity simple and crude. A totally unburdened propeller will still have some torque resistance. If nothing else, the mass of the blades come into play. Presumably the larger air foil shape will have enough force to move the larger mass and still start the rotation. But the slowness also means very little generation.

Compare this with a situation where a much smaller turbine with correspondingly smaller mass is seeing the same light wind condition. It will have a much lower wind velocity start point and will reach its maximum output sooner. This is lilely one reason why I have seen many installations with multiple smaller turbines. The other reson being that multiple generators are cummulative in terms of total charging current.

In applications with a round the clock demand such as communications towers, the connected loads will often drag down the battery voltage below the critical level where the battery starts to boil off electrolyte. This would be equally true for solar and wind.

Hi Elnav,

Your problem, if I've understood the theme correctly, is the effort to start a 10kW wind generator when there is only say 2kW worth of wind.

There is no resistance to the rotor electrically until it is turning fast enough to generate a emf > V_NOM of the system.

As the rotor spins up and the open circuit voltage increases above V_NOM the current developed will be (V_OC – V_batt)/ R, where R is the total series resistance of the circuit. However this current puts a brake force on the turbine and it is this matching that the MPPT has to accomplish. It would seem logical that the best designs would be variable dc/dc converters controlled so as to adjust the current flow to avoid the blades stalling. The MPPT's job is not to limit the voltage as a regulator, although it may well incorporate that function, it is to get the best out of a non linear generation system. ( this could be related to the way an automatic gear box draws power from an engine with a non-linear power curve).

If we look at the extremes, O/C (no current, blades turn freely) and S/C (no voltage, blades are braked) we will obviously be drawing no power from the wind. If now we vary the load between the extremes we will find a point where the max power con be drawn from the system. My idea of using a simple variable (mosfet) resistor is simply to vary the braking effect on the rotor. This could also be achieved by a chopper circuit but the system loads other than the battery may not like it.

I don't see any reason why a 10kW system should be more reluctant to start turning than a 2kW system since it is only a question of accelerating the rotor mass to the required speed. In all of this I have been assuming that the generators are optimised for the same wind speed, with their rotor blades suitably scaled.

Kind Regards

Chas

What about using a small, very simple, low power PLC to monitor the frequency of the output from the PMG and have it drive a series switching regulator which adjusts the duty cycle of the output from the generator by switching the output with a transistor or FET switch. Even SCRs can be used if they are applied to the AC output of the PMG. The program for the PLC could set the maximum power extracted from the generator based on speed (determined by the generator frequency). Low power extraction for low speeds, more power to the load when the generator is turning at higher speeds. Switch in the load dump when the batteries are fully charged and the speed is approaching a dangerously high speed.

The PLC could be in sleep mode for most of the time when the generator is not turning to minimize power drain and only "wake up" when the generator output reaches a pre determined level. If the generator is disconnected from the batteries and house load, except for the regulator when the regulator is off, there will be no additional drain on the batteries when the wind is calm.

for interest, here is a page I came across, where the author seems knowledgeable about the basics of wind power, and is a DIY guy. I don't know if this link has been posted anywere else here on CR4. I haven't seen it before anyway.

Chris

Dear Mr.chrisg288,

You have provided a page "here" without web link. If you click it opens. What should be done for this.? How to provide with out web-link.? pl. inform.

Many CR4 Members also posting like this, I want to know about this.

DHAYANANDHAN.S