Turbines with one or two blades are actually even more efficient. But because they’re also lighter and tend to spin faster, they’re also noisier. These designs also require a special tilting hub that acts as a sort of shock absorber, which is expensive. On the other hand, having more than three blades raises other problems. For one thing, the extra material needed to build the blades raises the cost. And the more blades there are, the lighter and thinner they need to be. Relatively thin blades are more flexible, making them prone to bend and break. Three-bladed turbines aren’t perfect, but they avoid many of these problems. They’re powerful enough without being overly expensive. And they’re less noisy than their two bladed cousins.

带一个或两个叶片的涡轮机实际上更有效率。但是因为这样重量较轻，旋转速度更快，噪音也就更大。设计还需要一个特殊的作为一种减震器的倾斜轮轴，它很贵。另一方面，如果叶片超过三个也会引发其他问题。一方面，建造更多的叶片需要更多的材料，这提高了成本。而且叶片，叶片就要更轻，更薄。很薄的叶片也更灵活，但容易弯曲和断裂。三个叶片的涡轮机并不完美，但会避免这些问题。他们造价不高，但是功率足够了。而且两个叶片的涡轮机噪音小。