Seeking advice - DIY wind power generation

[MissouriTiger]

[kenssurplus]

Hi Greg,

I have been running home built windmills for a number of years now. For a highly efficient windmill, please read through this site:

Wind Power | Otherpower

In there it answers most of your questions.

But briefly:
I have used 3 phase induction motors as a generator by using reverse induction (applying capacitors between phases). It worked, but not reliable enough for me.

I have converted an induction motor by machining a slot and gluing in in Neo mags. Resulted in a eddy current heater at high RPMs. But others have had sucess with them.

I used D.C. motors as generators (dificult to find good ones to use - volt/RPM range etc...)

By far the best windmill system I have had is the axial flux air core alternator with capacitor boost converter. Generates power in low wind, matches power curve at higher RPMs. See The back shed - visual effect of capacitors.The Back Shed: visual effect of capacitors

[kenssurplus]

Tried to edit my last post but it went away.

To your idea of 16 small windmills:

1 -wind at or near ground level is lousy with eddys and swirling dust and is slow etc.
2 -small dia. windmills need high RPMs - so they need high winds - so they wont produce anything most of the time.
3 -windmills at fench height are a decapitation machine for anyone / anything mobile.
4 -windmills at 10 ft apart will shadow each other cutting output.
5 -the sound comming from your place will more than outweigh any benefit you may receive and most likely end you up in jail or divorce court. (sound like 16 airplanes lined up for takeoff)

The cost of time and materials to make 16 small windmills is way more disproportionate compared to making a good 10 footer or bigger one done right.

[MissouriTiger]

DIY 1000 watt wind turbine

[Reiyuki]

I pondered on a similar project, though I'd try to help.

- Most wind/solar/hydro systems run on 12v (or 24/48v) DC.
- Alternators output AC/DC at various voltages.
- What we need therefore is a good buck/boost converter circuit. The idea would be to plug-and-play onto as many possible generator types as possible to charge your batteries. Then you power your loads separately (either 12v RV/Marine loads directly or 120/240 via inverter).
- Diversion load is needed because it prevents your turbine from over-spinning and blowing apart in high winds.


You could probably make a decent controller with an Arduino/Atmel, PIC, or equivalent and some tinkering. 50khz switching MOSFETs and voltage feedback. I can help if you need some more detail.

Keep us posted if you build anything cool

-Rei

[Allcanadian]

@kenssurplus

To your idea of 16 small windmills:
1 -wind at or near ground level is lousy with eddys and swirling dust and is slow etc.
2 -small dia. windmills need high RPMs - so they need high winds - so they wont produce anything most of the time.
3 -windmills at fench height are a decapitation machine for anyone / anything mobile.
4 -windmills at 10 ft apart will shadow each other cutting output.
5 -the sound comming from your place will more than outweigh any benefit you may receive and most likely end you up in jail or divorce court. (sound like 16 airplanes lined up for takeoff)

I figured I better jump in to clarify some of the old wives tales repeated here, lol.

1) First the main reason HAWT's are not generally found near ground level is because the long thin blades cannot handle turbulence. The blades fail at the root or the gear box fails and this is the main cause for very large large commercial machines failing. The turbulence is not the cause of the failures bad engineering is as I have tested many machines at ground level with no issues. A turbine mounted on an obstruction such as a hill or roof which accelerates the air around it will generally outperform a similar tower mounted turbine. Did you know that in a 5mph wind the air velocity two feet above a 4/12 pitch roof on a house can reach 65 mph?, now apply the V cubed rule and see what your power calculations tell you. Now let's say the wind direction is only correct 30% of the time, well you still produced three times more energy because wind velocity is the holy grail of wind Power.


2) Another old wives tale, I have built many small very low friction machines with efficiencies/outputs per unit of size on par with larger ones. The issue here is when suppossed experts try to design a small machine just like a larger one, it doesn't work that way. Energy is an average and a small amount of power over a large time frame matters, Energy in Kw/Hrs is what counts not instantaneous power.

3) Small well designed VAWT's work awesome on a fence line and a solid fence will accelerate the wind magnitudes higher than ambient. As you know wind power follows the V cubed rule and I have proven for myself that the wind accelerating effect can make a standard tower mounted HAWT look absurd.

4) It has been proven that groups of windmills can drastically increase power output. Why is that?, because 90% of the energy in the wind simply diverts around a standard HAWT. More turbines can act as a boundary condition which causes the wind to accelerate around them and if the accelerated air is utilized by another machine in close proximity it produces a large power gain. This is the V cubed rule again, a small change in wind speed produces a large change in output power. However we go right back to response #1, a standard HAWT with long thin (weak) blades with high tip speeds will tear itself apart in this turbulent air, it doesn't work.

5) Wrong again, as you may know almost all the noise is generated at the tip of the airfoil because the tip speed is excessive. This is because the engineers have never actually solved the problem and just keep repeating what everyone else does. I curved the airfoil tip inward/upwind to move the pressure gradient back towards the mid span covering a larger area and have no noise issues with small turbines.

The fact of the matter is most want to be experts are little more than sheep simply following others and have never really improved anything in their life. I mean come on let's be honest here how many people have you seen actually "improve" anything worth mentioning?. The real problem is that they are not actually solving any of the real problems which is unfortunate. Repeating others mistakes is not progress solving them is.

I would suggest people experiment and prove the matter for themselves, get motivated, get creative and think outside the box.

AC

[MissouriTiger]

Thanks again

Once again, I appreciate all the good information. I am going to post a new thread regarding a DIY project on the Web.

-Greg

[kenssurplus]

A/C Thank you for your reply,

With regards to # 1

It is usually suggested by most reputable installers and manufacturers that the most cost-effective arrangement will be to get your wind turbine 30 feet above anything withing 300 feet. If you have turbulent 10 mph winds at 30 feet up and smooth 13 mph winds at 70 feet up then it makes sense to go a bit higher, get out of the turbulence and get into a slightly higher windspeed where you might have *twice* the energy available! This is not the sort of talk that sells wind turbines, but it is reality.

- otherpower.com

with regards to #2,

The power in the wind is related to the *square* of the blade diameter (double diameter and you get 4 times the power) and the *cube* of the wind speed (doulbe the wind speed and you get 8 times the power)

- otherpower website.

With regards to #3
Yes! I have wanted to build a magnetic levetation bearing VAWT with an alternator sufficient to match my HAWT, but doing the numbers, I would have to have a bigger footprint and tower for the VAWT than for my HAWT! At least I couldn't figure out how to make the numbers equal out.

With regards to #4
Yes strategic placement of wind barriers, funnels, and enhancemant rings do increase output. Really we go back to responce #1, higher speed and cleaner wind has more power (elevation gains both).

With regard to # 5,
Most of the power in a windmill is at the tips of the blades. Yes you can run your windmill in stall mode and have very little noise, and also live with drastically reduced power out. Also if your alternator is mismatched to the power curve of the blades, then you can experience runaway speed where the blades will malke the swish swish sound. The smaller the dia. the machine is, the faster the RPMs are so the noise increases with frequency. A large windmill properly loaded makes hardly any noise.

Thank you again for you insights A/C as I too have built and flown many windmills including VAWT designs. When I found the capacitor boost converter matching circuit from Gordon, I truly found an improvement that doubled power out at cut in and reduced cut in speed too. This can be taken to winding with thicker wire thus improving on the copper wire loss.
Don't be too quick to gloss over experience.

[Allcanadian]

@Kenssurplus

With regards to #3
Yes! I have wanted to build a magnetic levetation bearing VAWT with an alternator sufficient to match my HAWT, but doing the numbers, I would have to have a bigger footprint and tower for the VAWT than for my HAWT! At least I couldn't figure out how to make the numbers equal out.

I know the feeling, I used a stepped up DC motor as a generator measuring power through a micro-processor to plot the torque per unit of degree on damn near everything out there... I was not happy. All the testing told me something I already knew, a HAWT with every airfoil performing work 100% of the time produces more power. I like the giro-mill and the torque curve can be extended through 270 degrees but has issues in itself I'm still working out. The plus of a Darrieus design is that the whole airfoil is equally active unlike a HAWT where the hub to mid span is practically useless, it's just a holder for the outer span doing all the work,lol. All have good and bad aspects I think and balancing them out is the hard part.

Thank you again for you insights A/C as I too have built and flown many windmills including VAWT designs. When I found the capacitor boost converter matching circuit from Gordon, I truly found an improvement that doubled power out at cut in and reduced cut in speed too. This can be taken to winding with thicker wire thus improving on the copper wire loss.
Don't be too quick to gloss over experience.

Is that a switch mode converter(inductor) or a capacitor (series/parallel) doubler?. You just gave me an awesome idea, I'm building a 100w LED flashlight (9800 Lumen) and am about 3v short of the turn on threshhold. Why not use a cap doubler with a series choke to smooth it all out and act as a current sense/limiter. Woot thanks.

AC

[kenssurplus]

boost converter doubler

Hi A/C

Series / parallel doubler - tripler - quadrupler capacitor diode configuration. however, the design was still undergoing simplification and testing when I stopped following it.

Please see the development thread here:
The Back Shed: visual effect of capacitors

And the final paper here:

TheBackShed.com - Cap mod