How Do Wind Turbines Work?
Besides generating electricity from the sun’s energy, the wind is also an effective, clean and renewable means of generating electricity. This is done using a system called a wind turbine. We have harvested wind energy in the shape of windmills for centuries. In the past, windmills were widely used to grind grain to make flour or to pump water. Modern-day wind turbines utilise the same technology but more efficiently. How do wind turbines work?
Wind turbines take the look of airplane propellers, but while airplane propellers are to keep the airplane in the air, wind turbines have nowhere to go. They rotate to collect the energy in the wind and convert it to electricity. If you drove past one and wondered exactly how wind turbines work, you have come to the right place.
How Do Wind Turbines Work to Generate Electricity?
A wind turbine contains two or three rotor blades on the front, known as the ‘’turbine” parts. Each blade has a curved shape, which allows it to accumulate energy in the wind.
When the wind blows past the curved blades at a certain angle, they will spin around. Every object that is moving contains energy called motion energy or kinetic energy. When the object hits another object, it passes some or all of its kinetic energy to the other object. Similarly, the wind loses its kinetic energy to the turbine blades and as a result, the blades rotate.
The amount of energy the wind turbine gains is proportional to the blades’ capacity to collect kinetic energy from the wind. Hence, a turbine with longer rotor blades generates more energy than one with shorter blades.
The speed of the wind also influences the amount of energy gained. A wind turbine accumulates more energy when the wind blows quicker, producing more electricity. The wind has to blow at least 8 to 15 miles per hour (13 to 24 km/h) to be able to generate electricity.
However, if the wind is too strong, the wind turbine cannot operate for safety reasons. The upper cut-off speed is 65 miles per hour (105 km/h). It is at this speed wind turbines are turned off to prevent any damage.
The amount of energy available in the wind is proportional to the cube of its speed. This means that when the speed of the wind doubles, the amount of energy available to be accumulated increases to eight folds.
How Do Wind Turbines Work: Key Parts of a Wind Turbine
The turbine blades are not the only components of a wind turbine to produce electricity. The turbine works with other, equally essential parts.
One of the most important parts of a wind turbine is a gearbox, whose function is to convert the blades’ slow rotation into higher-speed rotation.
This is necessary as the electricity generator requires a higher-speed motion to function. The rotational movement from the blades is passed to the gearbox through a shaft.
The turbine’s shaft only moves at around 25 to 60 spins per minute (rpm). Such slow motion is not sufficient for the generator, which requires speeds between 1000 and 1800 rotations per minute (rpm).
The generator is an essential part of a turbine because it is the component that converts wind energy into electricity. The generator works similarly to the dynamo on a bicycle. The dynamo on a bicycle produces light as it spins around with the rear wheel.
The turbine generator also works on the same principle. The only difference is that the wind turbine rather spins with the turbine’s rotor blades to generate electricity. The components mentioned above are enclosed in a nacelle. The nacelle is a casing that houses and protects the mechanism inside.
Another important component in the wind turbine is the yaw drive. The yaw drive allows the body of the turbine to turn to the direction of the wind. Imagine the swivel chair in your office and you will get the idea.
What Happens with the Electricity Generated?
Electricity generated by wind turbines is of a very low voltage. Therefore, it needs to be passed through a transformer that steps it up. It is at this high voltage that the electricity is transmitted to the power grid network. With this, electricity can be used in homes and businesses.
An individual or set of homes can also invest in a small wind farm or single wind turbine to generate electricity. Typically, wind turbines generate electricity 80% of the time. The remaining 20% accounts for wind conditions unsuitable for power generation or maintenance.
Also Read: How Does Geothermal Energy Work?
Vertical-Axis vs. Horizontal-Axis Wind Turbines
Wind turbines are classified into two types: horizontal-axis and vertical-axis wind. Though they work similarly, each has its advantages and disadvantages.
Horizontal-Axis Wind Turbine
Horizontal wind turbines are the most common wind turbines and are mostly found in big wind-farm applications. They are tagged “horizontal-axis” because the rotational axis is horizontal and parallel to the ground.
Horizontal-axis wind turbines have higher efficiency than vertical-axis turbines. This means that the horizontal wind turbine will convert a given amount of wind to more electricity than the vertical wind turbine. Hence, the horizontal-axis wind turbines are a better choice where more electricity is to be generated with a lower amount of wind.
Vertical-Axis Wind Turbine
This is the direct opposite of the horizontal-axis turbine. Vertical-axis turbines have their rotational axis standing vertically or perpendicularly to the ground.
They are mostly found in small and residential wind applications. Vertical-axis wind turbines are great for regions where the direction of the wind is not constant.
This is because the system is versatile enough to work with wind from all directions. In other words, vertical wind turbines work with wind from all 360 degrees.
How Strong Should the Wind Be to Generate Electricity?
Wind turbines are capable of generating electricity from wind that blows faster than 8 miles per hour (the lower boundary). However, the sweet spot lies between 20 to 50 miles per hour. They generate up to 50 % of their capacity most of the time but not always full capacity. When the wind tends to be stronger than what the turbines can accommodate, the turbines are shut down to prevent damage.
Furthermore, as for the horizontal-axis type, the turbine’s blades have to be positioned at the right angle for the wind to make them rotate. Apart from the yaw motor that allows the turbine to swivel on the mast , modern-day wind turbines have blades that can tilt back and forth to adjust to the wind conditions. This further increases its efficiency.
How Do Wind Turbines Work: Does Location Matters?
Yes, where a wind turbine is located contributes to its efficiency. This is why they are usually located in areas with high-speed winds. Prime locations are open and elevated areas such as hillsides free of woodland. Areas close to the sea are also a suitable option.
Wind turbines are categorized into two categories based on where they are located: Wind turbines located on dry land are tagged onshore, and the ones in the sea are termed offshore.
Did you know that offshore wind farms are far more effective at generating electricity than their onshore counterparts? It is due to the higher intensity of winds at or near the sea. On the other hand, onshore wind turbines are cheaper to install. Offshore wind turbines have to be built more robust to withstand the stronger winds while accessibility plays a part as well.
Why Are Wind Turbines Usually White or Pale Grey?
The color of a wind turbine does not affect its production capacity. Wind turbines are usually in white or pale grey only for visibility purposes. Discussion is ongoing on whether some settings should paint them other colors so that the system can blend with its environment.