Fieldlines.com || Make your electricity from scratch!

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products

Homemade Windmill with CNC machined blades
By taylorp035, Section Wind Posted on Tue Jun 30, 2009 at 12:40:01 AM MST
My most powerful one yet

This is my 4th major windmill. It has a diameter of approximately 30 inches. The generator is a motor that I found in my grandfather's trash can on vacation, originally served as a pump motor. Estimated rpm on the blades at about 20 mph is 2,000 rpm. No load voltage at 1,400 rpm is 12 volts.
The blades were made as a last minute project as a senior in high school this year on a 3 axis CNC router. I drew the blades up in the 3D CAD software Inventor, which I included a near perfect airfoil and a nice twist from the root to the tips. The hole for the shaft was drilled exactly where the center of gravity was, therefore automatically balancing the blades.
The tower is a 4", 10ft tall pvc drainage pipe in the ground. The rotating base was made out of an old lawnmower blade bearing.
Here is a link to a youtube video of it in action. The yellow meter is amps and the red is the voltage of my batteries. The battery is made up of (6) 2500mah nimh AA's, set up in a 3s2p configuration for 3.6volts and 5 amp hours.
www.youtube.com/watch?v=m_QE991BDKU
The max power that I have recorded would be 20 watts, 4 volts and 5 amps. I hope you guys like it! Im sorry that I don't have ant pics of it yet, maybe later.

Homemade Windmill with CNC machined blades | 10 comments (10 topical)

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#1)
by ghurd on Tue Jun 30, 2009 at 10:54:33 AM MST

Very Cool!

With 2 blades, that close to a 4" tower, there may be some issues with wind shadow.
It can be a lot more detrimental than you'd think. My open hand 3' behind a 1 dia meter blade dropped the output considerably.
Might try to extend the 4" pipe a ways with 1.5 or 2" pipe?
G-

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#2)
by taylorp035 on Tue Jun 30, 2009 at 01:11:25 PM MST

Yeah, you are right. I do notice the pole shaking at medium speeds. Once the blades get up to full speed (15+ mph), it is as smooth as a bmw v12 engine :)

The set up is not permanent, as it is not water proof yet. The windmill is easily detached by lifting it out of the pipe while on a step ladder.

[ Parent ]

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#3)
by Ungrounded Lightning Rod on Tue Jun 30, 2009 at 07:33:37 PM MST

Nice. Time to scale it up. B-)

By the way: Those foam covers for microphones are about keeping the wind from making noise that gets recorded due to vortex peeling near the opening of the microphone. You should see about getting a nice fat one for when you're videotaping a mill in the wind.

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#4)
by taylorp035 on Tue Jun 30, 2009 at 08:38:30 PM MST

I also have video that I haven't uploaded yet, that shows the tower bend significantly in heavy winds (it also shows me being surprised by the large gust of wind...lol). It is rather long (3 min and 200+ megabytes), and my upload internet speed is very slow (approximately a 4 hour job). I will try to upload it tonight and give you guys a link when it is ready.

By the way, I was wondering if you guys think I would get more power out of the windmill if I was charging two batteries instead of three? I have done as high as 4, but the voltage rarely gets that high. I have also charged just one cell.

I would think someone out there would have hooked up a 24v windmill to a 12volt battery bank.

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#5)
by ghurd on Wed Jul 01, 2009 at 08:38:01 AM MST

There is a magic point where everything comes together.
The voltage, amps, RPM, blades, wind speed, etc.

Connecting a decent 24V windmill to a 12V battery will make it reach cut in too soon.
Then amps start to flow, which puts load on the blades before there is enough energy in the wind to remove any energy from the wind.
The generator wants to extract 20W where there is not 20W available.
This causes stall.

A simple demonstration of stall is with almost a 0V load. Shorted output.
A decent windmill will violently slow down, like it has brakes. It will rotate at a very low RPM. This is the extreme example of stall.

I expect the motor in your windmill is fairly high resistance, which makes stall less obvious, and makes the windmill less efficient.
The blades are overly powerful for the output, so the blades sort of use brute force to keep pushing when stalled.

Typically, the magic point should be when it is charging at 1ma in 6.5MPH wind. Whatever voltage that happens to be is the voltage the system should work best.

Your blades seem pretty fast. The 6.5MPH RPM is about 600RPM, so cut in voltage should be reached at about 600RPM.
The generator makes about 5.1V at 600RPM.
Therefor, working with what we have in hand, the optimum battery voltage should be 5.1V.

All that assumes the blades are a good match for the motor (they most probably are not)
and the motor is relatively efficient as a generator (it most probably is not).

That is greatly over simplified.
G-

[ Parent ]

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#6)
by taylorp035 on Wed Jul 01, 2009 at 10:01:08 AM MST

Thanks for the input.

With my observations, I did not see a difference between a no load situation and when I connect the batteries. When I short it out, it stops the blades very fast. I think I will experiment with 3 or 4 cells in parallel to make a 1.2v pack and see if it makes a difference.

Here are some more videos that I uploaded last night.

http://www.youtube.com/watch?v=h5pBxgW4duM

http://www.youtube.com/watch?v=ZjHCulkKFwI

http://www.youtube.com/watch?v=-N0PWif6jtw

The last one has a very windy moment at about 2:50.

Unfortunately, I can't go outside today because it rained 6" yesterday in 4 hours.
I'm going to work with a spare alternator today to see if it is any good for a turbine.

[ Parent ]

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#7)
by taylorp035 on Thu Jul 02, 2009 at 03:10:41 PM MST

Do you guys think smaller windmills have lower TSR's than say 8? Because this thing at 1400 rpm with a TSR of 8 makes 15.6 mph wind.

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#8)
by ghurd on Thu Jul 02, 2009 at 06:00:08 PM MST

My old computer has a black 6' cord with 3 things on each end.
Is it 220V or 110V?
Is it a PC or a Mac?
Is it a desktop or laptop?
How much RAM does it have and how fast is the RAM?

You really do need to understand some of the terms used here.

[ Parent ]

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#9)
by Madscientist267 on Fri Jul 03, 2009 at 07:02:54 AM MST

<shakes head> ... all of that really depends... does it have a big screen or a little screen? ;P

[ Parent ]

Re: Homemade Windmill with CNC machined blades (3.00 / 0) (#10)
by wdyasq on Fri Jul 03, 2009 at 08:24:37 PM MST

I painted a motorcycle one time.

Ron
Adventure is just bad planning." -- Roald Amundsen
[ Parent ]

Homemade Windmill with CNC machined blades | 10 comments (10 topical)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board

Login

Make a new account

Username:

Password:

Total Views

��187 Scoop users have viewed this posting.

Related Links

� Also by taylorp035

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!