In my mind I have images of sail like blades. Would they not catch more wind if they were wider?
In: Engineering
As explained by others, wind turbines are…. turbines. They aren’t a pseudo-engine requiring winds to “push” them forward, they are turbines which generate energy by turning. As you increase the length of the blade, you are also exponentially increasing the area of rotation of the blades. In addition, the same force at a further distance produces more torque. So, the winds at the tips are responsible for generating more of the energy than the winds on the rest of the blade anyway.
A wider blade is significantly heavier and won’t catch that much more energy, but a longer one will.
A blade that’s 10% thicker will catch more wind, maybe 10% but also weighs at least 10% more and won’t necessarily give you 10% more power. Most of the energy capture is from the tips of the blades which capture wind from the largest area and can turn a given force from the wind into a much larger torque
If you instead use that 10% weight increase to have longer blades they’ll be a bit over 10% longer and capture a bit over 21% more wind(its the area of the disc, not just the length) so the goal is pretty much always to have longggg skinny lightweight blades so you can capture as large of a disc of wind as possible with the least material
The intention is not to catch wind, but to use the wind to rotate the blades. If they were bigger like a sail, the blades wouldn’t rotate. Hence they are designed aerodynamically so that they rotate with lesses wind speeds.
I’m not sure what the other answers here are talking about, I believe the reason that wind turbine blades are long and thin is to have a high aspect ratio. Wind turbine blades are basically wings, and in aerodynamics at low speeds a high aspect ratio, or a long and thin wing, will produce less drag for a given amount of lift then a lower aspect ratio, or a short and wide wing. On wind turbines, drag is a loss, as they are driven by lift, so minimizing drag by having a very high aspect ratio makes a wind turbine more efficient.
The type of drag that is caused by generating lift is called induced drag, and it is generally inversely proportional with the aspect ratio of the wing. This is also why most subsonic airplanes have long and thin wings. In particular, if you look at gliders and sailplanes, they also have extremely high aspect ratio wings for the same reason.
There are vertical axis wind turbines that use drag to drive the blades, which do have very wide, sail-like blades.
Hijacking the question to ask another one. Why do they turn them off? I see multiple turbines with some on and others off. Surly on a breezy day you’d want to make the most of wind and have them all in use?
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