Is wind power and hydraulic power related? The answer will be “No” if you are not from the hydraulic industry or related. But the truth is, hydraulics plays a key role in the operation of most of the wind turbines. As you know, wind energy is generated by the rotation of turbine blades. At the same time, hydraulic power is applied to this turbine for the rotation of blades that weighs tons. Hydraulics is not the only solution to power wind turbines. The electric power can also be used for this process. Usually, electric devices are adapted for small wind applications that rate below 2.5MW while hydraulics can be implemented in all types of wind applications.
Why are hydraulics mostly preferred in wind turbine systems? Hydraulics has many advantages over the electric. The most important factor is that the hydraulic system is more safe, reliable and cost-effective. Also, the hydraulic devices are comparatively lighter and reduce vibrations to a greater extent. So, systems with less vibration will reduce premature failure of components and improves the productivity and lifespan of the system.
The most important functions of hydraulics in wind turbines include pitch adjustment, yaw and rotor braking, cooling & lubrication, and power transfer. For wind turbines, it is necessary to control the rotation of blades that weigh tons. At high wind speed, the blades will rotate faster and damage the turbine. This problem can be resolved by adjusting the pitch angle and by using the brake control.
A drivetrain along with different other components are required for converting wind power to electricity. For larger turbines, it is a crucial task to regulate the pitch angle. For this pitch angle adjustment, the turbine system requires hydraulic pumps, motor, reservoir, and other components. The pump, motor, and other related components are mounted on the nacelle(the housing that covers all the generating components). Whereas the piston is mounted in the hub(that connects blades to the main shaft). The fluid from the reservoir will be passed through the rotary joint between the stationary and rotating sides.
The primary responsibility of drivetrain is to convert the variable angular speed-variable torque input shaft to a constant angular speed-variable torque output shaft. For this, the turbine uses a fixed displacement pump and variable displacement motor. The pump will be driven by the wind turbine and the motor is controlled by a servo variable cylinder. The wind power transfer occurs when the hydraulic fluid inside the hoses and pipes will get pressurized by the action of mechanical input energy and it is transferred to the hydraulic motor.
Some of the important applications of wind turbines are discussed below.
Hydraulic Pitch System: For optimizing the wind energy production, it is important to adjust the pitch angle of the rotor blades. The hydraulic pitch system in wind turbines is used for this. By adjusting the pitch angle, the load on the rotor blades during strong wind and the risk of structural failures can be reduced. Pitch cylinder, pitch accumulator, power pack and control panel are the important parts in the hydraulic pitch system. Among this, the pitch cylinder is considered as the necessary part of the pitch system. Other than the pitch angle adjustment, fail-safe function and the feedback on blade position are the other functions that are fulfilled with the hydraulic pitch system.
Cooling System: Similar to other overheated systems, wind turbines also will not offer the desired performance at high temperatures. With an increase in system temperature, many issues like system wear, loss of coolant, water evaporation, etc… will occur. So, it is necessary to choose an appropriate cooling system in the hydraulic wind turbine. Forced air cooling system and liquid cooling system are the two major categories of cooling system used. By maintaining the required temperature, the best performance of the wind turbine can be achieved.
Braking System: The braking system in a wind turbine is necessary for slowing and halting its operations. The hydraulically activated rotor brakes are commonly used to shut down the system manually. The rotor brake in wind turbine uses hydraulic pressure for this operation. When the pressure applied to the top pad, then the brake disk will apply force to the brake pad and then the system will come to rest. Yaw brake is another category of hydraulic brake that contains several hydraulically-activated brake calipers.
Read More: How Hydraulics Rule Wind Turbines Systems