Source: Huaxia Energy Network Huaxia Wind Power
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 3 giant blades mounted on it, each 80 meters long. It can generate 260,000 kWh of electricity 24 hours a day, which is enough to meet the electricity consumption of hundreds of households for one month.
There are many questions about this power generation, can the wind turbine rotate so slowly to generate electricity, and is there really so much power generation?
Everyone has played with the hand-cranked flashlight, shake it a few times, and the flashlight can really light up for a while, but it doesn't last long. The most classic is the hand-cranked razor, I remember when I was in high school, it was very popular (if you accidentally reveal your age).
Of course, the fan is not different from this hand-cranked toy, it really generates electricity!
In fact, the reason for the slow speed of wind turbine blades is very simple, which has a lot to do with its own weight and wind speed. The larger the fan, the longer the blades, the heavier the weight, and the slower it turns. The blades of a 1.5 MW wind turbine weigh about 6 tons, which is 1.8 times that of a 0.75 MW wind turbine blade, but it only makes 18 revolutions per minute, which is only 3/4 of the blade of a 0.75 MW wind turbine.
The speed of the wind turbine blades also has a lot to do with the wind speed, the faster the wind speed, the faster the fan will rotate. When the wind speed of the 1.5 MW wind turbine reaches 3 meters per second, the speed can be increased by turning the gears, thereby driving the generator to generate electricity.
So, can the speed of the wind turbine blades increase infinitely with the increase of wind speed?
That's certainly not the case.
When the wind speed exceeds the limit speed of the fan, the fan will stop working. Because if the rotational speed is too fast, the eccentricity will be greatly enhanced, and the inertia trend will break the balance of the fan itself, and the blades will be easy to break.
Therefore, each model of fan has a maximum speed. When the wind speed is too fast, it is necessary to operate the computer in the background to stop the operation of 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 km/h and the other at 200 km/h, which brakes is easier. Therefore, the slow rotation of the fan blades can more effectively protect the fan from damage.
In fact, the amount of power generated by a wind turbine does not depend on how fast the blades rotate. In the case of a constant speed of the blade, the force on the blade increases, and the power increases. The larger the blades of the wind turbine, the greater the power and the corresponding more power generation.
For example, a 1.5 MW wind turbine can generate 1,500 kWh of electricity per hour at full power. Based on the average daily electricity consumption of a family of three at 30 kWh during the peak summer season, it can be used for almost 50 days.
1 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, where the axis of rotation of the wind wheel is parallel to the direction of the wind, and (2) vertical axis wind turbines, where the axis of rotation of the wind turbine is perpendicular to the ground or the direction of the air flow.
2. 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 a counterpoint that rotates as the wind direction changes. For small wind turbines, this wind countering device uses tail rudders, while for large wind turbines, a transmission mechanism composed of wind direction sensing elements and servo motors is used.
The wind turbine in front of the tower is called the upwind wind wind turbine, and the wind wheel behind the tower is called the downwind wind fan. There are many styles of horizontal axis wind turbines, some have wind wheels with reversed blades, some install multiple wind wheels on a tower, so as to reduce the cost of the tower under the condition of a certain output power, and some horizontal axis wind turbines produce vortices around the wind wheels, concentrate the air flow, and increase the air flow speed.
3. Vertical axis wind turbines
Vertical axis wind turbines do not need to face the wind when the wind direction changes, which is a major advantage over horizontal axis wind turbines, which not only simplifies the structural design, but also reduces the gyroscopic force of the wind wheels against the wind.
There are several types of vertical-axis wind turbines that rotate with resistance, including wind wheels made of flat plates and quilts, which are pure drag devices, and S-shaped windmills, which have partial lift, but are mainly drag devices. These devices have a large starting torque, but a low point-to-speed ratio and provide a low power output given the size, weight and cost of the rotors.