The Chinese wind power industry has maintained its position as the world's number one for twelve consecutive years.
Seeing the vast expanse of wind turbines, you may have wondered: Can these slowly rotating three blades actually generate electricity?
The principle of wind turbines is not complicated at all. Unlike household electric fans, they convert the kinetic energy of the wind into mechanical energy, which is then further converted into electrical energy.
Why do wind turbines typically have three blades? What is the reason behind this? Why not four or two blades?
From an efficiency perspective, according to Betz's limit theory, fluid mechanics theoretically can capture a maximum of about 59.3% of the kinetic energy passing through a cross-section.
This means that a wind turbine can convert a maximum of 59.3% of the wind energy.
Through professional calculations, experts have found that under the same wind conditions, three-blade wind turbines increase wind energy utilization by 3% compared to two-blade wind turbines.
However, the efficiency improvement of four-blade wind turbines relative to three-blade wind turbines is very limited, only 0.5%.
However, the choice of the number of blades not only considers efficiency but also cost.
The transportation, installation, and maintenance costs of each blade amount to millions.
Therefore, it is obviously not cost-effective to increase the cost of one blade just to improve efficiency by 0.5%.
Although two-blade wind turbines have lower costs, their wind energy utilization is not as good as three-blade wind turbines.
To improve utilization, the blades of two-blade wind turbines need to be longer, and the rotor speed of the wind turbine also needs to be higher.
However, this will lead to significant noise and centrifugal force, damage the structural stability of wind turbines, increase losses, and reduce service life.
Therefore, currently, three blades are the best choice for wind turbines.
Is the rotation speed of wind turbines close to that of China's high-speed rail?
We often perceive wind turbine rotation speeds as slow, but the reality is different.
Taking a common 2-megawatt wind turbine as an example, its blade length is 50 meters, so the circumference swept by the blade tip is 314 meters.
With a rated power of 15 revolutions per minute, the blade tip sweeps 4710 meters per minute.
Simple calculation shows that the tip speed reaches 78 m/s, equivalent to 280.8 km/h, close to the speed of China's high-speed rail.
Is faster rotation speed better for wind turbines?
However, due to centrifugal force, faster rotation speed of wind turbine blades is not necessarily better.
When the wind reaches a certain intensity, wind turbines will limit the blade rotation speed to no more than 30 revolutions per minute.
Thirty revolutions per minute may seem insignificant, but each wind turbine is equipped with a speed increaser, which can increase the blade rotation speed by about 50 times.
In other words, while the outer blades of the wind turbine rotate at 30 revolutions per minute, the internal speed increaser can rotate at about 1500 revolutions per minute, thereby converting mechanical energy into electrical energy.
After more than 20 years of development, wind power generation and photovoltaic power generation have now reached 13.8% of China's total electricity consumption.
As an important part of the new energy system, wind power generation and photovoltaic power generation will have better development prospects in the future.
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