A wind turbine is an electrical device that converts wind energy into mechanical work, which drives the rotor to rotate and finally outputs alternating current.
We have reported on the V164 in Denmark, which is 220 meters high and has three giant blades, each 80 meters long. It can generate 260,000 kWh of electricity in 24 hours a day, enough to meet the electricity consumption of hundreds of households for one month.
Regarding this power generation, the editor has received many questions from everyone. Can the wind turbine generate electricity when it rotates so slowly? Is the power generation really that much? Everyone has played with a hand-cranked flashlight. If you shake it hard a few times, the flashlight can really light up for a while, but it doesn't last long. The most classic one is the hand-cranked razor. I remember it was very popular when I was in high school (I accidentally exposed my age).
Of course, the wind turbine is different from this hand-cranked toy. It really generates electricity! In fact, the reason why the wind turbine blades rotate slowly is very simple. This has a lot to do with its own weight and wind speed. The larger the wind turbine, the longer the blades, the heavier the weight, and the slower it rotates. The blades of a 1.5 MW fan weigh about 6 tons, which is 1.8 times that of a 0.75 MW fan, but they only rotate 18 times per minute, which is only 3/4 of that of a 0.75 MW fan. The rotation speed of the fan blades is also closely related to the wind speed. The faster the wind speed, the faster the fan rotates. When the wind speed reaches 3 meters per second, the 1.5 MW fan can increase the rotation speed by turning the gears, thereby driving the generator to generate electricity. So, can the speed of the fan blades increase infinitely with the increase of wind speed? That is definitely not the case. When the wind speed exceeds the speed limit of the fan, the fan must stop working. Because if the speed is too fast, the eccentricity is greatly enhanced, the inertia trend will break the balance of the fan itself, and the blades will easily break. Therefore, each model of fan has a maximum speed. When the wind speed is too fast, the computer needs to be operated in the background to stop the fan and reduce the damage and wear caused by its own inertia. This is equivalent to two identical cars, one with a speed of 30 kilometers per hour and the other with a speed of 200 kilometers per hour. It is the same as which one is easier to brake. Therefore, slow blade rotation can more effectively protect the fan from damage. In fact, the power generation of a fan does not depend on how fast the blades rotate. When the blades rotate at a constant speed, the force on the blades increases, and the power will increase. The larger the blades of the fan, the greater the power, and the more power it generates. For example, a 1.5 MW fan can generate 1,500 kWh of electricity per hour when generating electricity at full power. Calculated based on an average daily electricity consumption of 30 kWh for a family of three during the peak summer season, it can be used for about 50 days.
Types of wind power generation
Although there are many types of wind turbines, they can be summarized into two categories: ① horizontal axis wind turbines, the rotation axis of the wind rotor is parallel to the wind direction; ② vertical axis wind turbines, the rotation axis of the wind rotor is perpendicular to the ground or the airflow direction.
Horizontal axis wind turbines
Horizontal axis wind turbines are divided into two categories: lift type and drag type. Lift type wind turbines rotate fast, while drag type wind turbines rotate slowly. For wind power generation, lift type horizontal axis wind turbines are mostly used. Most horizontal-axis wind turbines have wind-facing devices that can rotate as the wind direction changes. For small wind turbines, this wind-facing device uses a tail rudder, while for large wind turbines, a transmission mechanism consisting of a wind direction sensor and a servo motor is used.
The wind turbine with the rotor in front of the tower is called an upwind wind turbine, and the wind turbine with the rotor behind the tower is called a downwind wind turbine. There are many styles of horizontal-axis wind turbines, some of which have rotors with reverse blades, some of which are installed on a tower to reduce the cost of the tower under the condition of a certain output power, and some horizontal-axis wind turbines generate vortices around the rotor to concentrate the airflow and increase the airflow speed.
Vertical-axis wind turbine
Vertical-axis wind turbines do not need to face the wind when the wind direction changes. This is a major advantage over horizontal-axis wind turbines. It not only simplifies the structural design, but also reduces the gyroscopic force of the wind rotor facing the wind.
There are several types of vertical axis wind turbines that use resistance to rotate, including a flat plate and a quilt made of wind rotors, which is a pure resistance device; S-type windmills, which have some lift but are mainly resistance devices. These devices have a large starting torque, but a low tip speed ratio, providing low power output at a certain rotor size, weight and cost.
