mettleramiel said:
dogman said:
Just to throw a wrench in the works, why build the wind turbine? Small ones are quite cheap compared to solar panels. The expensive part is the controller, inverter, battery storage. Won't really save a ton of money building the turbine.
Because if you build it yourself, you can spec it to your average wind speed. A turbine has its highest efficiency at a certain RPM. A store bought turbine will work best at whatever average wind speed they designed it for, but that's doesn't mean it will be optimal for you. Most small cheap, mills aren't very efficient at all.
Plus, as long as you don't value your time, building one can be much cheaper, depending on size, the bigger you make it, the more you save. Besides that, it's fun and rewarding!
Yes and no...
Actually the efficiency of the turbine is mostly concentrated in the rotor's speed / wind speed ratio for fixed pitch turbines and blade angle/wind speed ratio for variable pitch turbines.
In order to get the best results you have to set the load on the rotor for each wind speed and so for each rotor's speed. That's why there is so much development (and I have worked two years on it) on MPPT controllers. The solution of Hugh is a bullet-proof system which will have a wide range of "best efficiency" because of the small TSR (Tip Speed Ratio). This helps also the reliability of the rotor BUT it's not what we call Efficient (aim about 15% max efficiency). To compensate this fact the Hugh's turbines are quite big for the power they deliver and for that reason, heavy and Tank build.
That's not bad at all! it's just a way to detour the bunch of problem we got when we try to extract energy from the wind.
For your info. Wind speed is everything except regular. The more efficient rotor should be light weight (slow inertia) and will extract every burst of power as soon as it is hitted
This is unfortunately it's very hard to make. I know only a few little wind turbines controller which aim to do it (they don't, they are just "close" to it)
There is some tools on internet which will help you to design your turbine with any motor/generator. Beware that even if it is quite simple from outside, correctly extracting power from the wind is quite complex.
At last.. some simple rules:
-there is a ² in the power formula... that means that the bigger the rotor is, the ²the power will be.
-the width of your blade is related to the TSR. And as crazy as it sound the "perfect" rotor is a rotor with an infinity of infinitely thin blades
-as mentioned before, wind turbine HATES turbulence. A wind turbine, even little under 10 meter is an abjection.
-There is tons of exotic designs, but there were a very clever guy called Betz. He was no physician but a Mathematician. He has evaluated that the maximum power extractible from a fluid is 16/27 from the initial power. NOBODY can go against it... If they claim to do it.. they lie or they are cheating the game (like with a duct or any trick of this scale...) or they have make wrong measurement.
- Write you the theoretical power curve of a rotor and go with the maximum wind speed you could have (in one burst) in your area.. then calculate the thrust on the rotor and the necessary load on your generator... you will have a good idea why you shouldn't let your rotor spinning freely (solar_controller) and why you need a TANK design
Hope this helps! Read the book of Hugh if you are really interested in building a WT. And don't even think to build a vertical one!! ^^
Gruß,
H.
