Can wind turbines achieve higher efficiency even if they rotate very slowly?

Introduction Can wind turbines achieve higher efficiency even if they rotate very slowly? Just because a wind turbine spins slowly does not mean it is inefficient. In fact, it is more interesting. It is effective to rotate slower than the rated speed during normal ope

Can wind turbines achieve higher efficiency even if they rotate very slowly?

Slower wind turbine rotation does not mean lower efficiency. In fact, it is more interesting. During normal operation, the efficiency is highest when the speed is slower than the rated speed, but the net power to the Internet is relatively small. (Wind turbine is a kind of power generation equipment. Each type of wind turbine has its own specific rated power/speed/operating wind speed, etc. There is a global optimal value of wind energy capture efficiency in its impeller design, which corresponds to a specific set of (variable The combination of propeller angle) and (blade tip speed ratio), generally speaking, the pitch angle is close to 0 degrees, and the blade tip speed ratio is about 7 to 8. The basic principle in the design of wind turbines is to be able to capture. When the power brought by aerodynamic energy is less than its rated power, the wind energy should be captured as efficiently as possible, but it cannot exceed some constraints, such as its rated speed. When the aerodynamic energy that can be captured is greater than its rated power, the capture of wind energy should be actively reduced. Maintain the rated power. Friends who know more about it may know the power curve. As the wind speed gradually increases from the cut-in wind speed, the steady-state power curve can be basically divided into three segments: the part below the rated speed. In the load section, the pitch angle is optimal at this time, and the blade tip speed ratio is optimized by adjusting the motor load torque, thereby maintaining the optimal capture efficiency of the impeller. The efficiency of this section of the advanced low-speed fan can reach 50. %+, which is very good, but the output power is only less than half of the rated power. Within this range, the wind speed increases and the speed increases linearly. At a certain wind speed, it reaches the rated speed of the impeller, and then the next paragraph: located at In the partial load section of the rated speed, the pitch angle is still near 0 degrees, and the impeller always works at the rated speed (fluctuations are allowed, but the set value is the rated speed). The speed is maintained by adjusting the motor load torque, and the blade tip speed is The ratio is no longer optimal. As the wind speed increases, the motor load increases linearly, reaching full power at a certain wind speed (that is, the rated wind speed). After the wind speed exceeds the rated wind speed, it continues to the next section: the full power section. The motor load torque can no longer continue to increase to reduce the impeller speed. At this time, the pitch angle needs to be increased to reduce the capture of wind energy. As the wind becomes stronger, the pitch angle gradually increases (non-linearly), and finally reaches the cut-out wind speed. When cutting out. The rated speed of the newer low-speed fan is only 10 rpm, and the minimum operating speed may be only about half in the first section of the power curve, so it seems to be very slow. The impeller is indeed very slow but the speed is relatively constant. It only rotates two or three times a minute. This is usually when the car is warm and ready to start. If the rotation is just noticeable and cannot rotate in a few minutes, it is usually during parking. In this state, the wind load cannot be completely zero even in feathering conditions. There is a very small moment that can just overcome the damping in the transmission chain and push the impeller a little.

Excuse me. If wind energy is used to generate electricity, will the wind speed slow down? Will it affect the climate?

Although wind power generation is slow, the fans used in wind power generation are very large. . This kind of fan can drive a lot of force every time it rotates.So it will generate electricity.

Wind turbines use wind power to rotate machinery, driving the generator rotor and causing the stator to output electrical energy. There are two types of wind turbines, medium-high speed doubly-fed type and low-speed permanent magnet type. The doubly-fed unit is equipped with a gearbox, which can change the speed of the blades from a low speed of more than a dozen turns to a medium-high speed (above a thousand turns). ) to suit the generator to generate electricity.

The low-speed permanent magnet generator can operate at a low speed of more than ten revolutions because of its large number of magnetic poles and the ability to convert low-frequency electrical energy into industrial frequency electrical energy through a frequency converter for utilization. Therefore, although the wind speed is The rotation speed of the blade is very low, but suitable electrical energy can be output and utilized using both mechanical and electrical methods.

In single-phase power, the power of the generator is P=UIcosΦ. In three-phase power, the power of the generator is P=1. In three-phase power, the power is divided into three types: power P and no power. Q and apparent power S. The cosine of the phase difference (Φ) between voltage and current is called power factor, represented by the symbol cosΦ. Numerically, power factor is the ratio of active power to apparent power.

That is, cosΦ=P/S. The three powers and the power factor cosΦ are a right-angled power triangle relationship: the two right-angled sides are the power P and the non-power Q, and the hypotenuse is the apparent power S. In a three-phase load, these three powers always exist at the same time: S=P+Q S=√(P+Q) Apparent power S=1 Power P=1 No power Q=1 Power factor cosΦ=P/ S.

Notes

The main sources of wind are gravity and the sun. The sun causes uneven heating of the ground and the atmosphere, which leads to density differences between the atmospheres. With the assistance of gravity, atmospheric circulation is formed. The flow of gas forms wind, which acts on the blades of the wind turbine, causing the blades to rotate, similar to a water turbine, and then drives the generator to do work, converting wind energy into electrical energy.

The principle of wind power generation is actually the same as that of hydropower generation. They convert mechanical energy existing in nature into electrical energy, which is a form that is easy to transport and different from utilization. Of course, it benefits from the discovery of the electromagnetic effect.

The source of mechanical energy is due to the existence of the earth's gravity. Water naturally flows lower. The greater the water drop, the greater the pressure, and the higher the efficiency of driving the generator. However, hydropower generation starts with a water turbine. It is directly impacted by water, and then the water turbine drives the generator.

Reference for the above content: Baidu Encyclopedia - Wind Turbine

All human actions will affect nature directly and indirectly, intentionally or unintentionally. The use of wind energy to generate electricity is no exception, but the impact is almost negligible, not to mention that wind energy generation is a green energy. Through further innovation in science and technology, through further efforts of scientific and technical personnel, and through changes in people's life attitudes and consumption concepts, maybe from there Be able to feed back to nature from the beginning of the day.

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