Understanding Wind Turbines and their Lubrication

The use of wind turbines for harnessing wind Energy can be traced back to 5000 B.C when the early Egyptians used wind turbine generated power to propel boats in the Nile River. It has been used in one form or the other, ever since. Large-scale development of wind turbines in India began in 1986 starting from coastal areas of Maharashtra, Gujarat and Tamil Nadu. 

When running at its maximum performance, a wind turbine generates power equivalent to its power rating, it’s commonly known as nameplate capacity. For example, 1000 KW as a nameplate capacity would indicate that the wind turbine will produce 1000 kilowatts (Or 1 MW) of energy every hour if it’s running in optimum conditions.

The main components of a wind turbine that indicate its mechanical integrity and power-generating capacity are its gearbox and its generator. While there are numerous designs for windmills, let's consider the typical propeller-type wind turbine for the purposes of this article.

The basic structural components that make up most of the modern wind turbines consist of -
  1. A wind turbine propeller that captures the wind; it has a rotor that consists of two or more blades housed in a hub. The diameter of the rotor can be up to 75 meters.
  2. A shaft which is spun due to the wind energy.
  3. A generator that converts the movement of the shaft into electricity. This generator is usually a common induction generator that produces 50 or 60-cycle AC electricity.
  4. A tower that provides height to the entire assembly so that it is away from the turbulent air present close to the ground.
  5. A nacelle, which sits on top of the tower and houses the generator, controller gearbox, and brake. It is attached to the turbine propeller from the front and it pivots to maintain perpendicular contact as the wind shifts.
  6. A gearbox connects the low-speed shaft to the high-speed shaft. This increases the average RPM from 40 to 60 to about 1,500 to 1,800 RPM (Rotations per Minute), because that is the speed required by most generators to produce electricity.
  7. A yaw drive located in the tower, below the nacelle grants control of the wind turbine to the operator. It connects a computer controlled system which orients the nacelle according to the wind. The Blades are turned or pitched to prevent the rotor from turning in winds that are too high or too low for electricity generation.
  8. A disc brake that can stop the rotor in case of emergencies, it can be applied electrically, hydraulically or mechanically. Modern turbines have systems that can automatically switch-off the turbine in a very high-speed wind or extreme temperatures.
The operator analyzes the wind conditions and adjusts the settings of the wind turbine to maximize its output and minimize its depreciation. The turbines should ideally be started when the wind speeds go above 8 and 16 MPH (Miles per Hour) depending on the size of the wind turbine and it should be stopped when it reaches 65 MPH. 

Windmills are highly reliable machines as compared to other conventional power generating technologies, especially considering the extreme mechanical and environmental pressures they endure. Mechanical and structural failures (which may result in the collapse of the tower) mainly occur due to the control system error and lack of proper maintenance. Field operating failures occur primarily due to the gearbox bearing failure. This is always the consequence of poor lubrication and lack of periodic maintenance.

The bearings in the gearbox of a wind turbine take extremely high loads and there are variations in the bearing’s required performance criteria in various parts of the gearbox. 

As per the operating conditions it may be required for the bearings to carry a medium level load at low speed while in another part of the gearbox, low-level load at much higher speed might be required.

When the wind is slow, a part of the gearbox has to handle high load with low speed, this leads to the breakdown of the lubricating film that prolongs the bearing’s life. This is why lubricants from reputed companies like Castrol are recommended, they are engineered by keeping all these factors into consideration. 

Proper maintenance is crucial to preventing your gearbox from failure. Use a special gearbox oil filter to keep the oil free from contaminants that usually get into the oil in desert regions or in arid conditions. The airborne dust can easily enter the gearbox and act as an abrasive; this can lead to a contact fatigue failure.
This information is provided for guidance and informational purposes only. This website and information are not intended to provide investment, laboratory or manufacturing process advice.
The information contained herein has been compiled from sources deemed reliable and it is accurate to the best of our knowledge and belief. However, Castrol cannot guarantee its accuracy, completeness, and validity and cannot be held liable for any errors or omissions, as the results change depending on the working condition/environment.  Changes are periodically made to this information and may be made at any time.
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