There is a reason for this. The old electric fan is composed of three blades.
A few days ago, the old electric fan at home broke down, and then I bought a new one. This fan no longer has only three blades like the traditional electric fan, but is composed of many small blades. This design looks like It sounds much better than a traditional electric fan. At the same time, this also reminds me of another problem, which is the wind turbines used in wind power generation. Without exception, they are composed of three blades. Why is this? You can't create energy out of thin air, so wind power doesn't create electricity out of thin air, it just converts energy and turns wind energy into electricity. Since it is the conversion of energy, it will inevitably involve a problem, that is, conversion efficiency. The conversion rate of wind energy is closely related to two factors, one is wind power and the other is wind speed.
Wind force is equal to wind power times wind speed.
Now imagine that our wind turbine has many blades that combine to form a closed disk. What about wind power conversion? Basically zero. Because when the wind turbine becomes a closed disk, the wind force acting on the disk can indeed be maximized, but no wind can pass through the disk and can only go around the disk, so the wind speed acting on the disk is zero. Any number multiplied by zero is zero, so even if the wind is very strong and there is no wind speed, there is no way to achieve the conversion. It can be seen that in order to convert wind energy into electrical energy, the number of blades must be reduced so that the wind can pass quickly. As the number of blades decreases, the wind speed will gradually increase and the wind force acting on them will gradually decrease. In order to achieve maximum conversion power, a balance point must be found.
Now, you might think that since a wind turbine has three blades, it must be because the wind is strongest with three blades, but that's not the case.
Calculations show that the wind power conversion rate of the four blades is the highest. So why do wind turbines have three blades instead of four? When we encounter a problem, if we cannot find the answer in scientific principles, then the answer must be related to another factor, and that is money. The fan is not an electric fan. It has to withstand a lot of force and bending moment when working, so the material must be hard. The blades of modern large-scale wind turbines usually use steel pipes or D-shaped steel as longitudinal beams, steel plates as cross beams, filled with foam inside, and covered with fiberglass skin outside.