Homebrewed Electricity > Wind
New build- 20 foot diameter variable pitch windmill
windy:
I am in the process of building a 20 foot diameter variable pitch windmill and may need some help in designing the stator and rotor. I have attached a file using the Axial Generator Calculator that was posted a few years back. Could someone look at this and let me know if this looks right.
I will be using this generator for resistance heating only,(water and space heating). There will be no batteries or DC voltage involved. Controlling speed will be with a Arduino microprocessor using solid state relays.
The blades that I am using are the GOE 222 profile that I carved myself and read a few posts back that when using the 222 profile, the stator should be wound accordingly.
I designed the stator and rotor using Solidworks and used these dimensions in the file. I will be using 20 poles with 15 coils. Not sure if I have the wire gauge right.
Take a look and leave any comments or questions and will reply as soon as possible. When I get a little farther with the build, I will post some pictures.
windy
midwoud1:
Hi Windy.
There is a 20 foot diameter on a older Otherpower by the Dan's.
7 pages construction . Images seem to be lost, Reliable mill work for years.
http://www.otherpower.com/20page1.html
SparWeb:
Hi windy!
It's been a while since we heard from you. Glad to see you back.
Are these the same blades? https://www.fieldlines.com/index.php/topic,147424.msg1019120.html#msg1019120
I looked at your spreadsheet.
Something I think we should discuss first is the load you intend to use, connected as resistance heating only. I don't think that spreadsheet works for resistance loads. In fact, resistance heating is so different from battery charging that I think we should discuss your resistance load in detail because it will have a lot of control over what the turbine does.
I remember Oztules hooking up a big turbine to resistance loads so let me look for that while you come back and tell more.
windy:
SparWeb,
Thanks for the reply. Yes, those are the pictures of the blades that I posted 5 years ago. Wow, how time flies.
I planned on using three 3000 or 4500 watt 240 volt water heater elements, wired to three phase star configuration, to heat water in a hot water heater and when that gets hot enough, circulate the water through a heat exchanger in my ductwork to help with space heating. I could also dump excess heat into my heat pump ground loop system in the fall of the year.
I looked at one of the online blade calculators and a 20 foot diameter blade is rated at 10kw @274 RPM. The Axial Generator Calculator show it to be 6.4KW @274 RPM. I am looking to wind the generator for around 9-10 KW@275 RPM.
There will be no offset on the generator. It will face directly into the wind using a tail. Speed will be controlled through the PWM terminals on an Ardunio Uno. The higher the voltage, the longer the PWM pulses are sent to the Solid State Relays which will increase the load to hold down the speed. I am still trying to figure out how to program it, but I think I can get it to work. May have to ask OperaHouse for some help. To protect the generator in high wind conditions, I plan on automatically pitching the blades out of the wind using a switch and timer, wait an hour or two and try again. At 250-275 RPM's, a linear actuator will pitch the blades so it stops rotating. That will be the only time the pitch mechanism is activated. I don't plan on using the pitch mechanism to control speed.
Does the generator resistance have to be wound to match the resistance of the load?
I am sure I will have more questions before I am done, but it will be an interesting project.
windy
Royalwdg:
I have found that properly carved GOE222 blades have extreme torque capabilities. They will walk right through high electrical loads. If you are counting on slowing with adding loads you will probably be frying some stators. Blade pitching forward is a great idea for control.
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