Can a wind turbine be more efficient if it is slow?

The basic principle of the design of wind turbines is that when the power that can be captured by the kinetic energy of the air is less than its rated power, the wind energy can be captured as efficiently as possible, but not beyond some constraints, such as its rated speed. When the kinetic energy of the air that can be captured is greater than its rated power, the capture of wind energy is actively reduced and maintained at the rated power. Friends who know more about it may know that the power curve is such a thing, as the wind speed gradually increases from cut-in speed (cut-in speed), the power curve of steady state can be basically divided into three dash lines:

In the part of the load section lower than the rated speed, the pitch angle is optimal, and the blade tip speed ratio is adjusted by adjusting the motor load torque, so as to maintain the optimal value of the impeller's capture efficiency. The efficiency of the advanced low-speed fan can reach 50%+ in this section, which is very good, but the output power is only half of the rated power. In this range, the wind becomes stronger, the rotational speed increases linearly, and the rated speed of the impeller is reached at a certain wind speed, and then the next section is reached

Located in the partial load section of the rated speed, when the pitch angle is still around 0 degrees, the impeller always works at the rated speed (fluctuations are allowed but the set value is the rated speed), and the speed is maintained by adjusting the load torque of the motor, and the blade tip speed ratio is no longer optimal. As the wind increases, the load on the motor increases linearly and reaches full power at a certain wind speed (i.e., rated nominal wind speed). After the wind speed exceeds the rated wind speed, continue to the next section:

In the full power section, the load torque of the motor can no longer be increased to reduce the speed of the impeller, so it is necessary to increase the pitch angle to reduce the capture of wind energy. As the wind increases, the pitch angle gradually increases (nonlinear), and finally cuts out when the cut-off wind speed is reached. Newer low-velocity fans are rated at only 10 rpm and may only have a minimum operating speed of about half at the first stage of the power curve.

So it looks like it's slow. But if you see an impeller that is really slow but has a constant speed, only two or three revolutions a minute, it is usually in the heat of the car and ready to start. If it is just perceptible to rotate, it can't turn a circle for a few minutes, it is generally in a parking state, but it is not possible to do the wind load completely zero in the case of the propeller, and there is a small torque that can just overcome the damping in the transmission chain and push the impeller a little bit.

There are two kinds, one shaft is directly connected to the synchronous motor, the synchronous motor has a large number of pole pairs, and the synchronous speed is very low. One is to drive a high-speed motor through the speed increase of the speed increase box. I don't know what you mean by efficiency, power generation efficiency is torque multiplied by angular velocity, the middle is transmission loss and electrical loss, transmission loss is mainly some mechanical friction loss, electrical loss of copper and iron consumption of motors, converters are mainly IGBT on-state and switching losses, as well as line capacitance, circuit breakers, contactors and so on.

The efficiency of wind energy utilization, which is related to the control method, is not the faster the rotation, the higher the efficiency, there is a nonlinear relationship, the maximum will not exceed the Bez limit, in fact, there is also the loss of the blade tip and root, which is probably the limit, this ratio is the kinetic energy of the air flow that actually flows through the wind wheel blades into the kinetic energy of the blades. <>

It depends on the capacity of a single unit (850kw, 1mw, etc. must be different in terms of electric energy), and it also depends on the wind power. 1 kWh = 1kw·h, according to this calculation, 850kw wind turbine can generate 850*24=20400kw·h per day, which is a theoretical value. It also depends on the wind situation, power transmission and transformation losses, and so on.

Principles of wind power generation.

1.The principle of wind power generation is to use wind power to drive the windmill blades to rotate, and then increase the speed of rotation through the speed increaser to promote the generator to generate electricity.

Chinese name wind power generation principle.

The foreign name is the principle of wind power generation

Pinyin: feng li fà fàn dàn yǐ li

Position is forming a craze in the world.

Endemic locations Finland, Denmark and other countries.

Wind power generation is forming a boom in the world, and wind power generation is used in Finland, Denmark and other countries. The principle of wind power generation is very popular, and China is also vigorously advocating it in the western region. Because wind power has no fuel problems and does not produce radiation or air pollution, it is a particularly good way to generate electricity.

2.How it works.

The principle of wind power generation is to use wind power to drive the windmill blades to rotate, and then increase the rotation speed through the speed increaser to promote the generator to generate electricity. According to current windmill technology, the speed of a breeze (the degree of the breeze) is about three meters per second, and electricity can be generated.

Wind power is becoming a boom in the world because it has no fuel problems and does not produce radiation or air pollution.

Wind power is popular in countries such as Finland and Denmark; China's wind power industry has developed by leaps and bounds in recent years. A small wind power system is very efficient, but it is not only composed of a generator head, but a small system with a certain technological content: wind turbine + charger + digital inverter.

The wind turbine consists of a nose, a rotating body, a tail, and blades. Each part is important, and the functions of each part are: the blades are used to receive wind power and convert it into electrical energy through the head of the machine; The tail fin keeps the blades facing the direction of the incoming wind for maximum wind energy; The rotating body can make the nose rotate flexibly to achieve the function of adjusting the direction of the tail; The rotor of the machine head is a permanent magnet, and the stator windings cut the magnetic field lines to generate electricity.

Wind turbines are a process that converts kinetic energy into electrical energy. The wind drives the rotors in the generator to turn. The kinetic energy generated by rotation will be electrical.

It rotates through the fan blades of the engine, and the engine generally generates an electric current through a magnetic field when it rotates, and then the effect of power generation can be achieved.

There are some variable speed machines in this kind of generator, although it looks very slow on the surface, but in fact the speed is very fast, and there will be some devices in it to transmit the electricity generated by the wind to other places.

The principle of power generation is to convert wind energy into electrical energy and use power to generate electricity.

Wind turbines don't spin faster and produce more electricity. Note that the output power of a generator can be roughly considered to be proportional to the product of speed and torque. Here the torque is the electromagnetic torque obtained by the generator excitation.

The torque is so great that the wind can't push the impeller. At this time, the speed is 0, the torque is very large, and the power output is 0. When the torque is zero, the speed will accelerate to a very high level, which is actually a flying car, which is extremely dangerous.

Since the electromagnetic torque is 0, the output power is 0. Power is 0 at both extremes, so there is an optimal speed that maximizes power output.

The ideal value for this optimal speed can be calculated from Baez's theory, the ratio of the linear velocity at the tip of the blade to the wind speed in front of the wheel. At a certain wind speed, there is a nonlinear relationship between the fan output and the blade tip speed ratio. Through theoretical derivation, the optimal tip velocity ratio for each wind speed can be calculated.

A wind turbine is a device that converts wind energy into mechanical energy, then makes the mechanical energy do work, and finally produces alternating current. In fact, wind energy can also be said to be solar energy, because it is also used to generate electricity, and there is no harm to our environment.

It is able to have a lot of energy, because of its internal structure, and not depends on the speed of rotation of the external blades, it is better to do the windmill by yourself, in fact, it has a quiet gear rotation inside, the speed of the windmill rotates at a speed of 20 - 30 per minute, the wind is not enough, this is not to say that it can't put the speed faster, this is because of the weight and length of the blade, see it from a distance, don't think how big it is, in fact, its blade is more than 20 meters long, the weight can be imagined, if the turn is too fast, it will exert a lot of pressure on the base. If a generator collapses or a blade breaks, it can cause an accident that injures nearby residents. If it rotates slowly, there will be no such thing, which ensures that the windmill blades are not injured, are not prone to accidents, and will not affect its power generation efficiency, after all, there is a small motor hidden inside!

With it, even if the wind outside turns very slowly, with a reducer and pinion inside, its speed will increase by about fifty times, basically maintaining a speed of about fifteen hundred revolutions per minute.

How wind turbines generate electricity.

Wind energy is a clean energy source, and it is renewable, so it can be said that it is inexhaustible. More than 2,000 years ago, the ancients learned to use windmills to carry water for irrigation and mill grain. After entering the industrial civilization, people are more interested in how to use wind energy to generate electricity, a resource with extremely low development and utilization rate.

Although the outer blades rotate slowly, each wind turbine is equipped with a speed-increasing machine inside, which can drive the gears of the generator to rotate rapidly, increasing its speed by about 50 times. In this way, the blades on the outside of the wind turbine can rotate 30 revolutions per minute, and the generator gears inside the wind turbine can rotate 1,500 revolutions per minute, so that a large amount of electricity can be generated.

Because wind is a resource that can be recycled, and nature's wind energy is relatively sufficient, it will be used in large quantities.

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

Wind turbine is to use wind power to rotate machinery, drive the generator rotor to make the stator output electrical energy. There are two types of wind turbines, medium and high speed doubly-fed and low-speed permanent magnetsThe doubly-fed unit is equipped with a gearbox that can change the low speed from a dozen revolutions of blade rotation to a medium to high speed (more than 1,000 revolutions) to be suitable for generator power generation.

The low-speed permanent magnet generator can be operated at a low speed of more than ten revolutions, because of its large number of magnetic poles, and the low-frequency electrical energy can be converted into power frequency electrical energy through the frequency converter to be utilized.

In single-phase electricity, the power of the generator p=uicos In the three-phase electricity, the power of the generator p=1 In the three-phase electricity, the power is divided into three kinds of power, there is power p, no power q and apparent power s. The cosine of the phase difference ( ) between voltage and current is called the power factor, which is represented by the symbol cos, and numerically, the power factor is the ratio of power to apparent power.

That is, cos = p s The three power and power factors Cos is a right-angled power triangle: the two right-angled edges are power p, no power q, and the hypotenuse is the apparent power s. In a three-phase load, all three types of power are always present at the same time at any time

s=p+q s= (p+q) apparent fibrillation power s=1 with power p=1 without power q=1 power factor cos = p s.

Precautions. The wind is mainly gravitational and sun, the sun causes uneven heating of the ground and the atmosphere and then leads to the density difference between the atmosphere, with the assistance of gravity to form atmospheric circulation, the flow of gas forms wind, the wind acts on the blades of the wind turbine, so that the blades 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 hydroelectric power, which is to convert mechanical energy existing in nature into electrical energy, which is convenient for transportation and utilization, and of course thanks to the discovery of electromagnetic effects.

The first mechanical energy is due to the existence of the earth's gravity, the water naturally flows lower, the greater the drop of the water, the greater the pressure, the higher the efficiency of the driving generator, but the hydropower generation is directly impacted by the water turbine first, and then the turbine drives the generator.

The above content reference: Encyclopedia - Wind Turbine.

It depends on which type of wind turbine you choose.

There are two main types of wind power generation systems: constant speed and constant frequency wind turbine systems and variable speed and constant frequency wind turbine systems.

The constant speed and constant frequency wind power generation system generally uses a synchronous motor or a squirrel cage asynchronous motor as a generator, and the speed of the generator is kept at a constant value through the wind turbine controlled by the fixed pitch stall to ensure the constant frequency and amplitude of the output voltage at the generator end, and its operating range is relatively narrow, and the wind energy can only be captured at a certain wind speed, and the power generation efficiency is low.

The variable speed constant frequency wind power generation system generally uses permanent magnet synchronous motor or doubly-fed motor as the generator, and the whole system runs according to the best efficiency in a wide range of speed through variable pitch control of the wind wheel, which is the development direction of wind power generation technology.

For the fan, its speed range is generally between 50% and 150 of the synchronous speed, if the ordinary squirrel cage asynchronous motor system or permanent magnet synchronous motor system is adopted, the capacity requirements of the inverter are equivalent to the capacity of the dragged generator, which is very uneconomical.

The stator of the doubly-fed asynchronous wind power generation system is directly connected with the power grid, and the rotor is connected with the power converter, and the power through the converter is only the slip power, which is relatively high efficiency in various transmission systems, and the structure is suitable for the wind power generation system with a wide range of speed regulation, especially the wind power generation system with large and medium capacity.