Why a slow wind turbine can generate so much electric
Wind turbines are electrical equipment that converts wind energy into mechanical work, mechanical work that drives the rotor to rotate, and ultimately outputs alternating current.
The V164 wind turbine in Denmark, with a height of 220 meters, is equipped with three giant blades, each with a length of 80 meters. It can generate 260,000 degrees of electricity 24 hours a day, enough to meet the electricity consumption of hundreds of households for one month.
However, you may have doubts, can the wind turbines turn so slowly to generate electricity, and is there really so much power generation?
If you have ever used a hand-powered flashlight, you will know when you shake it, the flashlight will shine for a while, though the duration is not long.
In fact, the reason for the slow fan blade speed is very simple, which has a lot to do with its own weight and wind speed.
The larger the fan, the longer the blade, the heavier the weight, the slower the turn. The 1.5 MW wind turbine blade weighs about 6 tons and is 1.8 times the 0.75 MW wind turbine blade, but it only turns 18 laps per minute, only 3/4 of the 0.75 MW wind turbine.
The speed of the fan blades is also closely related to the wind speed. The faster the wind speed, the faster the fan turns. When the wind speed reaches 3 meters per second, the 1.5 MW wind turbine can increase the rotation speed by rotating the gears to drive the generator to generate electricity.
Then, can the fan blade speed increase indefinitely as the wind speed increases?
When the wind speed exceeds the fan’s limited speed, the fan will stop working. Because if the speed is too fast, the eccentricity is greatly enhanced, and the inertia trend will break the balance of the fan itself, and the blade will be easily broken.
Therefore, each type of wind turbine has a maximum speed. When the wind speed is too fast, it is necessary to operate the computer in the background, stop running the wind turbine, and reduce the damage and wear caused by its own inertia.
This is equivalent to two identical cars. One speed is 30 kilometers per hour, one is 200 kilometers per hour. Which brake is easier? Therefore, the slow rotation of the blades can effectively protect the fan from damage.
In fact, the amount of power generated by a wind turbine does not depend on the speed at which the blades rotate. In the case where the blade rotation speed is fixed, the power is increased as long as the blade is subjected to a force increase. The larger the blades of a wind turbine, the greater the force it’ll get, the greater the power, and the more power generation.
For example, a 1.5 MW wind turbine can generate 1500 kWh in one hour at full power. With a family of three in the summer peak season, using an average of 30 kWh per day, it can be used for almost 50 days.
Types of wind turbines
Although wind turbines are diverse, they can be divided into two categories:
- Horizontal axis wind turbine, the rotating shaft of the wind wheel is parallel to the wind direction;
- Vertical axis wind turbine, the rotating shaft of the wind wheel is perpendicular to the ground or the direction of air flow.
Horizontal axis wind turbine
The horizontal axis wind turbines are divided into two types: lift type and resistance type.
The lift type wind turbine rotates at a fast speed and the resistance type rotates at a slow speed.
For wind power generation, lift-type horizontal-axis wind turbines are often used.
Most horizontal axis wind turbines have a windward arrangement that can rotate as the wind direction changes.
For small wind turbines, this wind device uses a tail rudder.
For large wind turbines, a wind direction sensing element and a servo motor are used.
Wind turbine fan in front of the tower is called the upwind wind turbine, while the fan behind the tower is called the downwind fan.
There are many styles of horizontal axis wind turbines. Some wind fans with reverse blades, some have multiple fans which are installed on one tower to reduce the cost of the tower under a certain output power. There are also horizontal-axis wind turbines that generate vortices around the wind fan, concentrating airflow and increasing airflow speed.
Vertical axis wind turbine
The vertical axis wind turbine does not need to be corrected to face the wind when the wind direction changes. At this point, it is a big advantage over the horizontal axis wind turbine. It not only simplifies the structural design, but also reduces the gyro force when facing the wind.
There are several types of vertical-axis wind turbines that use resistance rotation, among which are wind turbines made of flat plates and quilts, which are pure resistance devices; S-type wind turbines with partial lift, but mainly resistance devices. These devices have a large starting torque, but have a low tip speed ratio and provide a low power output with a certain fan size, weight and cost.