The kinetic energy of the wind is converted into mechanical energy by a wind turbine, which is a rotating machine. This mechanical energy is subsequently transformed to electricity and fed into the power system. The rotor and generator are the turbine components responsible for these energy transformations.
The rotor is the part of the turbine that includes the turbine hub as well as the blades. The hub of the turbine rotates due to aerodynamic forces as wind strikes the blades. The transmission mechanism then sends this rotation through to reduce the revolutions per minute. The main bearing, high-speed shaft, gearbox, and low-speed shaft make up the transmission system. The rotation division and rotation speed that the generator sees are determined by the gearbox ratio. The generator, for example, sees the rotor speed divided by N if the gearbox ratio is N to 1. Finally, the generator receives this spin for mechanical-to-electrical conversion.
The essential components of a wind turbine are shown in Figure 1: the gearbox, generator, hub, rotor, low-speed shaft, high-speed shaft, and main bearing.
The hub connects the servos that alter the blade direction to the low-speed shaft on the blades. The rotor, which includes both the hub and the blades, is the part of the turbine that rotates. The nacelle is a framework that holds all of the components together.
Increased aerodynamic forces on the rotor blades are dependent on the amount of surface area available for the incoming wind. The angle of attack refers to the angle at which the blade is adjusted. This angle is calculated in relation to the blade’s chord line and the incoming wind direction. There is also a critical angle of attack, crucial, where air no longer flows smoothly over the upper surface of the blade. The critical angle of attack with regard to the blade is depicted in Figure 2.
This section shows how the efficiency of the wind power extraction process is affected. Consider Figure 3 as a representation of the turbine’s wind interaction. This diagram shows that there is wind on both sides of the turbine, and the right balance of rotational speed and wind velocity is crucial for performance regulation. Equation 1 is used to compute the tip speed ratio, which is the balance between rotational speed and wind velocity.
The power coefficient, or, is a measure of a wind turbine’s efficiency. The power coefficient is defined as the ratio of actual to ideal extracted power in theory. Equation 2 contains the formula for this computation. You can also make adjustments by adjusting the angle of attack and the tip speed ratio. Equation 3 shows the calculation for this scenario. In Equation 3, the coefficients c1-c6 and x should be provided by the wind turbine manufacturer. The greatest power coefficient that any turbine may attain is.59, often known as the Betz limit.
Equation 2: The power coefficient is determined by dividing the actual extracted power by the ideal extracted power.
Controlling the angle of attack, as well as the tip speed ratio, allows you to fine-tune the.
Finally, Equation 5 can be used to calculate the wind’s useful power. The blade length and wind speed are the primary determinants of useful power, as shown in this equation.
To identify the appropriate control type, optimization, or limitation, it is necessary to understand the relationship between power and wind speed. The power curve, which is a plot you can use for this, shows how much power you can get from the approaching wind. An ideal wind turbine power curve is shown in Figure 4.
The turbine’s operating limits are the cut-in and cut-out speeds. Staying in this range ensures that the available energy is above the minimum level and that structural health is preserved. The rated power, which is provided by the manufacturer, considers both energy and cost. Furthermore, the rated wind speed was chosen since winds beyond this point are uncommon. A turbine design that extracts the majority of energy over the rated wind speed is typically not cost-effective.
The power curve is separated into three discrete zones, as seen in Figure 4. The turbine is run at optimum efficiency to harvest all power because Region I has low wind speeds and is below the rated turbine output. To put it another way, the turbine controls are optimized. Region III, on the other hand, has strong wind speeds and is operating at full turbine power. When operating in this region, the turbine controls with the generated power limit in mind. Finally, Region II is a transition zone where the focus is on reducing rotor torque and noise.
Why is it necessary to manage the speed of a wind turbine?
Low maintenance costs and effective performance necessitate wind turbine control. The control system also ensures safe operation, maximizes power output, and extends the life of the structure.
What causes a windmill’s speed to be reduced?
The diagram below depicts a turbine’s power production vs stable wind speeds. The blades begin rotating and generate electricity at the cut-in speed (usually between 6 and 9 mph). As the wind speed increases, more power is generated until the rated speed is reached. The turbine produces its maximum, or rated, power at this point. The power generated by the turbine remains constant as the wind speed increases until it reaches a cut-out speed (which varies by turbine) and shuts down to avoid undue strain on the rotor.
Why are there three blades on most wind turbines?
Drag is reduced when there are fewer blades. Two-bladed turbines, on the other hand, will wobble as they spin to face the wind. This is due to the fact that their vertical angular momentum changes depending on whether the blades are vertical or horizontal. Because one blade is up and the other two are oriented at an angle, the angular momentum of three blades remains constant. As a result, the turbine may smoothly revolve into the wind.
In a wind turbine, what is a gearbox?
In a wind turbine, a gearbox is commonly employed to raise the rotating speed from a low-speed main shaft to a high-speed shaft connected to an electrical generator. Due to changing wind loads that are stochastic in nature, gears in wind turbine gearboxes are subjected to intense cyclic loading.
What controls the turbine’s speed?
The governor, which can be mechanical-hydraulic (derived from James Watt’s original flyball governor) or electrical, controls the steam turbine. They all have a pilot valve, also known as a controller, that adjusts the turbine’s inlet valve to keep the shaft speed at the desired level.