What is Wind Turbine?
A wind turbine is a device that converts the wind’s kinetic energy into electrical energy.
A wind turbine turns wind energy into electricity using the aerodynamic force from the rotor blades, which work like an airplane wing or helicopter rotor blade. When wind flows across the blade, the air pressure on one side of the blade decreases.
The difference in air pressure across the two sides of the blade creates both lift and drag. The force of the lift is stronger than the drag and this causes the rotor to spin.
The rotor connects to the generator, either directly (if it’s a direct drive turbine) or through a shaft and a series of gears (a gearbox) that speed up the rotation and allow for a physically smaller generator. This translation of aerodynamic force to the rotation of a generator creates electricity.
Wind turbines are manufactured in a wide range of sizes, with either horizontal or vertical axes. It is estimated that hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year.
They are an increasingly important source of intermittent renewable energy and are used in many countries to lower energy costs and reduce reliance on fossil fuels. One study claimed that, as of 2009, the wind had the “lowest relative greenhouse gas emissions, the least water consumption demands and… the most favorable social impacts” compared to solar, hydro, geothermal, coal, and gas.
Smaller wind turbines are used for applications such as battery charging for auxiliary power for boats or caravans, and to power traffic warning signs. Larger turbines can contribute to a domestic power supply while selling unused power back to the utility supplier via the electrical grid.
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History of Wind Turbine
In the first century Heron of Alexandria, a Greek engineer, and mathematician, made the earliest accounts of using a wind wheel. William Cubitt was an English engineer and inventor who invented the self-regulating windmill sail in the early 1800s.
Daniel Halladay “the father of the American windmill” invented the self-regulated windpump in 1854. His version was seen in Argentina, South Africa, and New Zealand. In 1887 Professor James Balth of Scotland built the first textile sail wind turbine for electricity generation. This generated enough electricity to illuminate their house.
Charles F. Brush in Cleveland Ohio built the first large-scale wind turbine in America in 1888 with a gearbox.
In 1890s, Paul La Court a Danish inventor and scientist studied the aerodynamics of windmills and methods of storing electrical energy in batteries. He invented a regulator to produce a stable power supply
William Heronmess “the father of modern wind energy” and inventor of wind turbine arrays, wind ships, wind furnaces, and offshore flotilla ideas – in the late 1960s, he correctly predicted the future energy crisis and had a vision on a grand scale. Renewable Energy Development.
Vestas and Siemens Wind Energy are Danish manufacturers that supply a substantial share of wind turbines worldwide.
How do wind turbines work?
Wind turbines operate on a simple principle: fan-like wind turbines use the wind to create electricity, rather than using electricity to produce electricity. The wind rotates the propeller-like blade of a turbine around the rotor, which rotates a generator, generating electricity.
Wind turbine blades spin when hit by the wind. And it doesn’t have to be a strong wind either: the blades of most turbines start rotating at a wind speed of 3 to 5 meters per second, which is a light breeze.
It is this twisting motion that turns a shaft in the nacelle, which is the box-like structure on top of a wind turbine. A generator built into the nacelle then converts the kinetic energy of the rotating shaft into electrical energy. This is then passed through a transformer that boosts the voltage so it can be transported on the National Grid or used by a local location.
From microturbines for a single house to huge offshore wind farms, all wind turbines use the same mechanics to generate electricity.
How much electricity can a wind turbine create?
Most onshore wind turbines have an output of 2-3 megawatts (MW), which can produce over 6 million kilowatt-hours (kWh) of electricity each year. This is enough to cover the electricity needs of around 1,500 average households.
The faster the wind blows, the more electricity is generated to a certain extent. When the wind speed doubles, up to eight times more electricity is generated. However, when the wind is too strong, the turbines shut down to prevent damage.
All of this means that the ability of a wind turbine to produce the maximum amount of energy can depend on the wind. Wind farms are carefully planned to ensure they are in locations with reliable wind levels all year round. This is usually on the top of a hill with lots of open space and in coastal locations. Because of this, there are quite a number of wind farms in places like Cornwall and Scotland.
How efficient is wind power?
A wind turbine usually has an efficiency of 30-45% and increases to 50% at peak times. If this sounds quiet to you, keep in mind that if the turbines were 100% efficient, the wind would drop completely after going through the turbine.
UK wind turbines produce electricity 70-80% of the time, making them a reliable source of electricity year-round.
Wind Turbine Diagram:
Components of a Wind Turbine
The functioning of the wind turbine can be explained in the following steps:
- Anemometer: Measures the wind speed and transmits wind speed data to the controller.
- Blades: Lifts and rotates when the wind is blown over them, causing the rotor to spin. Most turbines have either two or three blades.
- Brake: Stops the rotor mechanically, electrically, or hydraulically, in emergencies.
- Controller: Starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 55 mph. Turbines do not operate at wind speeds above about 55 mph because they may be damaged by the high winds.
- Gearbox: Connects the low-speed shaft to the high-speed shaft and increases the rotational speeds from about 30-60 rotations per minute (rpm), to about 1,000-1,800 rpm; this is the rotational speed required by most generators to produce electricity. The gearbox is a costly (and heavy) part of the wind turbine and engineers are exploring “direct-drive” generators that operate at lower rotational speeds and don’t need gearboxes.
- Generator: Produces 60-cycle AC electricity; it is usually an off-the-shelf induction generator.
- High-speed shaft: Drives the generator.
- Low-speed shaft: Turns the low-speed shaft at about 30-60 rpm.
- Nacelle: Sits atop the tower and contains the gearbox, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on.
- Pitch: Turns (or pitches) blades out of the wind to control the rotor speed, and to keep the rotor from turning in winds that are too high or too low to produce electricity.
- Rotor: Blades and hub together form the rotor.
- Tower: Made from tubular steel (shown here), concrete, or steel lattice. Supports the structure of the turbine. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
- Wind direction: Determines the design of the turbine. Upwind turbines—like the one shown here—face into the wind while downwind turbines face away.
- Wind vane: Measures wind direction and communicate with the yaw drive to orient the turbine properly with respect to the wind.
- Yaw drive: Orients upwind turbines to keep them facing the wind when the direction changes. Downwind turbines don’t require a yaw drive because the wind manually blows the rotor away from it.
- Yaw motor: Powers the yaw drive.
Types of Wind Turbines
There are two basic types of wind turbines:
- Horizontal-axis turbines
- Vertical-axis turbines
The size of wind turbines is very different. The length of the blades is the biggest factor in determining the amount of electricity a wind turbine can produce. Small wind turbines that can power a single house can have a power generating capacity of 10 kilowatts (kW).
The largest operating wind turbines have power-generating capacities of up to kilowatts (10 megawatts), and larger turbines are under development. Large turbines are often grouped together to form wind power plants or wind farms that supply electricity to the power grid.
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Horizontal-axis turbines.
Horizontal axis turbines have blades like aircraft propellers and typically have three blades. The largest horizontal-axis turbines are as high as 20-story buildings and have blades over 30 meters in length.
Taller turbines with longer blades generate more electricity. Almost all wind turbines currently in use are horizontal-axis turbines.
Vertical-axis turbines.
Vertical axis turbines have blades attached to the top and bottom of a vertical rotor. The most common type of vertical axis turbine – the Darrieus wind turbine, named after the French engineer Georges Darrieus who patented the design in 1931 – looks like a giant two-winged egg knocker.
Some versions of the vertical axis turbine are 100 feet high and 50 feet wide. Very few vertical-axis wind turbines are used today because they do not work as well as horizontal-axis turbines.
Types of vertical-axis wind turbines
- Darius wind turbine
- Giromill
- Savonius Wind Turbine
- Parallel
1. Darius wind turbine.
The “Agbutter” turbine, or Darius turbine, was named after the French inventor, Georges Darius. They have good efficiency but produce large torque ripples and cyclic stresses on the tower, which contributes to poor reliability.
They typically require some external power source, or an additional Savonius rotor to initiate turning, as the starting torque is very low. Torque ripple is minimized using three or more blades, resulting in greater solubility of the rotor.
Density is measured by the blade area divided by the rotor area. The new Darius-type turbines are not held by male wires but have an external superstructure. That is connected to the top bearing.
2. Giromill Wind turbine.
A subtype of Darius turbine with straight, as opposed to curved, blades. The cycle turbine variation has a variable pitch to reduce torque beats and is self-starting. The advantages of unsteady pitch are high rising torque; A broad, almost flat torque curve; A high coefficient of production; more efficient operation in turbulent winds; And a lower blade speed ratio that reduces the bending of the blade. Straight, V or curved blades may be used.
3. Savonius Wind Turbine.
These are drag-type devices with two (or more) scoops used in anemometers, flattener vents (typically seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops.
The twisted Savonius is a modified savory, with long helical scoops to provide smooth torque. It is often used as a roof-mounted wind turbine and has even been adapted for ships.
4. Parallel Wind Turbine.
A parallel turbine is similar to a crossflow fan or centrifugal fan. It uses the ground effect. This type of vertical-axis turbine has been tried for years. The unit producing 10 kW was built by Israeli wind forecaster Bruce Brill in the 1980s.
