Wind energy is a renewable and clean energy. With the continuous increase in human demand for energy, human beings gradually began to increase the use of wind energy. Wind turbines are often found on vast grasslands, hillsides, and even on the sea. Why the blades of wind turbines turn so slowly, can they generate electricity? Adjusting the wind turbine speed to what we see is a combination of many factors.
Wind turbine blades are heavy and laborious to rotate.
Many people think that a wind turbine is like a small windmill. It is not big, especially when we see a big wind turbine from a distance. We have this feeling but this is not the case. A wind turbine can be called a behemoth. The blade of the wind turbine is 60 meters long.
We know that the wingspan of a medium-sized passenger plane is about 30 meters. The wingspan of an ordinary large passenger plane can hardly reach 60 meters. Although such a large blade uses high-strength and low-density materials, the mass is not too small. Usually, more than ten tons in weight, three blades of such high quality are naturally a bit difficult to turn.
Some people might have a question. Since such a big blade is hard to turn, why not make it smaller? This is related to the windward area of the generator. When the blade is too small, the windward area is naturally too small. The wind on the blade is less and less, and the electricity generated by a single generator is less and less. If the number of generators increases, can it be compensated? The increase in the number also increases the construction cost.
Generally speaking, small blade generators will cost more if they emit the same power. However, the fan cannot be too large. On the one hand, it is limited by the material, on the other hand, the installation will be more difficult. After comprehensive consideration, we now use large and small fans.
Higher RPM does not mean more power generation.
As the blades of the wind turbine rotate, it drives a huge internal gear to rotate together. When the big gear drives the small gear, the speed of rotation also changes significantly. We can express ourselves in the way that we are most familiar. This structure is equivalent to a gearbox. We see the blades spinning slowly, but the blade actually drives the generator through the gearbox to spin at high speed.
Of course, the power generated by the wind turbine is not only related to the speed, but also related to the torque. Power is equal to torque speed. When the speed is small, the output power can also be increased by increasing the torque.
Therefore, to prolong the durability of the wind turbine we won’t make the blades spin too fast. As the wind turbine blade is huge and the centrifugal force of high-speed rotation is also large, then long-term high-intensity centrifugal motion will also damage the life of the blade. Therefore, when the wind turbine encounters strong winds, it will turn on the protection mode and stop generating electricity to protect the fans.
Excessive speed will also affect the power generation efficiency.
When the blades of the fan rotate, they also impede the movement of the wind. The higher the speed, the stronger the obstacle. When a certain value is reached, the utilization rate of wind energy will also begin to decrease.
To make it easier for everyone to understand, we can imagine two extreme examples. If the speed of the fan is close to infinity, the rotation of the blades is equivalent to directly forming a sealing plate, blocking the wind flow. At this point, the wind has to take a detour, so naturally this wind energy cannot be used very well. At this time, the utilization rate of wind energy is equivalent to zero.
Another situation is that the blade speed goes straight to zero. At this point, wind energy is not being used at all. In the range of zero speed and infinite speed, the speed with the highest utilization of wind energy exists. This speed is related to many factors. There's just a lot of discussion here. Therefore, the blade speed we see is not much different from the theoretical optimal speed. By adjusting to the optimal rotational speed, the wind energy utilization rate at this time is also the highest.
Summarize
So the wind turbine looks slow and the actual airframe is doing efficient power generation. The seemingly simple fan generator actually considers the influence of various factors on the fan power generation efficiency at the beginning of the design. There are complex and strict scientific truths behind the simple phenomenon.
