3 Blades vs 5 Blades

waynefromnscanada wrote: »

It was definitely the yaw of the mill. Think of it this way - - -
Hold an 8 foot board vertically, and see how easily you can move it to face different directions. Almost no inertia. Now hold it horizontal and do the same thing. You'll find a lot of inertia if you try to change it's direction quickly.
What happens with changing yaw on a 2 blade prop, as the blade approaches the vertical, the tail suddenly, very easily swings everything to the new direction. Then as the blades start to swing down to the horizontal, they undergo extreme stress as they "want" to continue traveling in their former direction, but now the bearings are trying to force them in the new direction. The result is that the whole affair goes through a violent convulsion, that repeats every half turn of the blades.
Locking it into one heading, or controlling it's yaw so it could only change very slowly, then there wouldn't be that problem.
Interesting stuff. lol

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WIND TURBINE BLADE FACTS:

REMEMBER! Bigger does not always equal more electricity! While the bigger blade sets do have more torque and thus turn easier in slower wind areas they DO however turn SLOWER when compared to smaller diameter blade sets on the same PMA. Make sure this is what you really need or you could be sacrificing electricity in the higher wind areas since small blades turn faster. Of course we are again assuming you are using direct drive PMA's here.

As a overall rule, larger diameter turbines will always make more power IF they are optimized for a particular generator's output with the proper gearing. Generally speaking 8 foot is the largest diameter you can go with an ECONOMIC direct drive system. After the 8 foot diameter range blades spin so much slower that gearing makes better economic sense for operating most PMA's or generator's. The other option would be to waste copious amounts of copper wire and expensive magnets making for a very wasteful, expensive and heavy direct drive generator or PMA design. It would seem that the 7 to 8 feet diameter range is the transition point between economic direct drive and larger geared systems.
THE "MORE BLADES" THEORY and ARGUMENTS:
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Having lots of blades really gives you the best of both worlds. In low winds speeds, systems with 6 to 12 blades are a real power house! No argument here! They also have an advantage in super high winds since they can't REV as fast so they end up actually protecting themselves by going slower than 3 blade systems would that either self-destruct or become very noisy!!! The more research we do with multiple blade systems the more we believe in the More Blades Theory. These systems always come out on top out performing systems with less blades especially in high amp loaded conditions! Wind turbines experience "PROGRESSIVE LOSS" or Cascade Failure when under heavy loads. This means that the slower the rotor spins under load the MORE likely it is to spin even slower and so on (Cascade Failure) until the blades are moving so slow they can't catch enough wind to be effective anymore because of excessive "Way-Holes". This is why two and three blade systems need a computer to keep the blades rev'd up to speed. The computer removes the load by making fast adjustments and this keeps the blades moving quickly eliminating cascade failure. However a computer is not necessary when you have lots of blades working for you since cascade failure is impossible with all of that surface area!
"Cascade Failure"
The slower a blade spins the more likely it is to spin even slower and so on until it can no longer adequately catch wind as "Way-Holes" form in the propellers diameter matrix area.

"Way-Holes"
A potential power producing area of a wind turbine propellers diameter that is allowing air to pass through in-between blade strikes.
or - The absence of a wind turbine blade in the winds path at any given point in rotation time usually caused by over-amperage loads including connection to lower voltage batteries used in low wind speed areas or high amperage appliances or lack of blade area in the original turbine design.
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IT ALL BOILS DOWN TO THIS ONE SIMPLE LITTLE QUESTION IN THE END
The REAL question becomes, WHAT is cheaper. Extra BLADES or COMPUTER controls???
Well, at least in the case of small wind turbines it's a no-brainer,, Extra blades are much cheaper than electronic controls and definitely more dependable too - no computer electronics to fail!!! In the final analysis more blades equals super low wind speed start up plus the added benefit's of simplicity and dependability.
Final thought,the large commercial wind turbines use 3 large blades but they are also all GEAR DRIVEN,not direct drive and use a computer to control the speed of the blades,otherwise the blades if allowed to speed up in high winds would simply explode.These type of turbines DO NOT REQUIRE HIGH SPEED TO PRODUCE POWER LIKE THE SMALL TURBINES DO.

Missouri Wind And Solar

BB. wrote: »

The WIND TURBINE BLADE FACTS is from Missouri Wind and Solar "Falcon Blades" section.

-Bill

keyturbocars wrote: »

What they state is interesting, but it's good to take things with a grain of salt when people have mixed motives (trying to make a sale).