How Do Wind Turbines Work?

July 11, 2020
Horizontal axis wind turbine

What is a wind farm? A wind farm is an area that contains many large wind turbines grouped to collect the power of the wind. A large wind farm may have hundreds of wind turbines over hundreds of miles.

When the wind turns the wind turbine blades, it converts this wind’s energy into mechanical energy. Then the generator converts this mechanical energy into electric power to power homes, offices, and every other place.

History of Wind Energy

During the 1st century AD, Hero of Alexandria created the wind-driven wheel used to power a machine. By the 7th to the 9th century, people in Iran’s Sistan region used the windmills to grind corn, flour and pump water. And by 1000 AD, people in China and Sicily used the windmills for pumping seawater to make salt.

People from Northwestern Europe used vertical windmills in 1180, for grinding flour. But Prof James Blyth built the first known wind turbine used for producing electricity in 1887, in Scotland. At Marykirk in Kincardineshire, they used it to charge accumulators to power the lighting in the cottage.

In 1888 Charles Brush built the first US wind turbine for electricity and used it to provide electricity for his mansion in Ohio.

Also, Paul La Cour developed an electricity-generating turbine in 1891. At that time, he figured out how to use a regulator to supply a steady stream of power from the wind turbine. And he also converted his windmill in 1895 into a prototype electric power plant, which was later used to provide electricity for the village of Askov.

Other Developments

Approximately 2500 windmills with a combined peak power capacity of 30 MW were used in 1900 for mechanical purposes such as grinding grain and pumping water. Georges Jean Marie Darrieus designed the vertical axis wind turbine in 1931. People still use it today for niche applications, such as on boats.

The horizontal axis wind turbine was also built in Yalta, and it has a 100 KW of capacity, a 32-meter high tower, and a 32% load factor. The first megawatt-size wind turbine was connected to a local electrical distribution grid in 1941, and it had blades of 75 feet in length.

In 1975 the NASA developed a utility-scale wind turbine, including steel tube towers, variable speed generators, composite blade materials, partial-span pitch control, aerodynamic, structural, and acoustic engineering design capabilities.

The world’s first multi-megawatt wind turbine was produced in 1978 by Tvind school teachers and students, and it is still running today. During 1980 in New England, the first modern wind farm was constructed, including 20 wind turbines.

The first onshore wind farm was constructed in 1991 in Cornwall, and that included 10 wind farms that produced electricity for approximately 2700 homes.

In 2000 about 97 wind farms were used to provide enough power for up to 592000 homes. Now over 7000 wind turbines are used to produce 6.5 GW of power.  Furthermore, there are ongoing initiatives to have 20 GW of power capacity installed by 2020.

Working Principle of Wind Turbine

How does a wind turbine generate electricity?

Firstly, it generates electricity using a wind turbine as the wind’s energy turns two or three propellers around a rotor connected to the main shaft.  Thus, the wind turbine connected to the shaft converts the wind power into mechanical power, converted by the generator to electricity.

Then again, you should know that wind energy is a form of solar energy due to the uneven heating of the atmosphere by the sun and the irrigation of the earth’s surface beside the earth’s rotation.

Types of Wind Turbines

It is important to know the different types of the wind turbine, and the types are:

1. Horizontal Axis Wind Turbine (HAWT)

It’s similar to propeller airplane engines, and it consists of two or three blades that operate upwind. These blades are; a shaft that is horizontal to the ground; a generator connected to the shaft and turned by a gear on the end of the shaft; an anemometer, a wind fan, and a controller that helps the blades to meet the wind all the time.

This plant is as tall as 20-story buildings, and each blade is about 100 feet long. Also, it is usually the type that we use nowadays. It has the following advantages and disadvantages:

Advantages

  • Most types are self-starting.
  • People can build it in the forest above the tree-line.
  • It is also able to pitch the rotor blades in a storm to minimize the damages.
  • Also, it has a high ability to wing warp that gives the blades the best angle of attack.

Disadvantages

  • It is difficult to operate in near ground winds.
  • It is also difficult to transport.
  • The maintenance is difficult.
  • It is also difficult to install.

2. Vertical Axis Wind Turbine (VAWT)

It looks like egg beaters, and it has blades attached to the top and the bottom of a vertical rotor. Some of these plants are 100 feet tall and 50 feet wide. There are two types of these turbines; they are left based and drag based. They have some advantages and disadvantages as:

Advantages

  • The maintenance is easy.
  • Transportation from one place to another is easy.
  • Also, the costs of construction and transportation are low.
  • It’s not directional.
  • Also, It’s most effective at hilltops, passes, mesas, and ridge-lines.
  • And it’s little-used compared to the horizontal one because:

Disadvantages

  • It is less efficient.
  • It operates in the more turbulent wind.
  • The airflow near the ground creates a turbulent flow that produces high vibrations of the blades.
  • It may require energy to start turning, and the starting torque is low.

3. Ducted (roof-mounted) Wind Turbine

We find it at the edge of a building roof and utilizes the airflow along the building’s side. The air flows upwards to hug the building wall and enters the front of the duct. The diameter of the blade is around 600 mm. This turbine has these advantages and disadvantages:

Advantages

  • It makes use of the unused roof space in cities.
  • It has a less visual impact on the building’s architecture than the traditional HAWT turbines.

Disadvantages

  • It is only suitable for urban environments and isn’t suitable for households.
  • It is a uni-directional, fixed position and depends upon the wind blowing in the correct direction.
  • Also, We need more research to determine energy production potential.

At the same time, those types are classified as:

1- Utility-scale Wind Turbines:

These ranges in size from 100 kW to as large as they could reach. Similarly, these plants are cost-effective and the bulk power to the electric grid because they are grounded together into wind farms.

2- Distributed (small) Wind Turbines:

For homes, telecommunications dishes, and water, we use below 100 KW. Sometimes connected with diesel generators, batteries, and photovoltaic systems used in remote or off-grid locations where there isn’t availability to a utility grid.

3- Offshore Wind Turbine:

They are large turbines capable of generating more power without the transportation challenges of land-based wind installations as the plant’s large components can be transmitted on ships.

Wind Turbine Parts

The wind turbine is massive and has complex pieces in many sizes and configurations. Additionally, the blades range in size from 34 to 55 meters, and the hub weighs 8 to 10 tons, and the towers are 80-100 meters tall and 55 to 70-ton weight. So the major components of the turbine are:

1- The Anemometer

This measures the speed of the wind and transmits the data of the wind speed to the controller.

2- The Rotor

It consists of:

Blades: This acts as barriers to the wind, and when the wind forces these blades to move, it transfers some energy of the wind to the rotor. Some turbines contain two or three blades.

The hub (shaft): This spins when the rotor spins and transfers the mechanical energy into rotational energy.

Brake: They stop the rotor in emergencies, even mechanically, electrically, or hydraulically.
And the pitch drive system turns the blades out of the wind to control the rotor speed and stop the rotor from working at too high or too low speeds.

3- The Nacelle

This is the external shell structure resting atop the tower, and it contains:

Controller: We use it to start up the machine at wind speeds of about 8-16 miles per hour. Also, shut off the machine at about 55 miles per hour, which is the maximum allowed speed.

A gearbox: This connects the low-speed shaft to the high-speed shaft and increases the rotational speeds, and it’s costly. Thus, engineers explore generators to operates at lower rotational speeds that wouldn’t need gearboxes.

Generator: It connects to the shaft and spins to convert the mechanical energy into electricity.

High-speed shaft: This drives the generator. Additionally, we use electronic components to allow the turbine to monitor changes in wind speed and direction.

4- The Tower

Rolled steel tube sections bolted together compose it, as they provide support for the blades and nacelle.

And there are also other components such as a transformer, circuit breakers, fiber optic cables, and ground-mounted electrical equipment.

Cost of Wind Energy

Having understood wind farms, especially the wind turbine components, it is essential to reflect on wind energy costs. There is no cost for fuel. However, there are other costs.

Capital costs: Involves the wind turbine cost, which is more than 70% of the entire cost. There are also installation costs such as construction costs, cables; turbine foundation; connections to the grid, and transportation. And the average capital costs in 2016 were about $1590/KW.

Maintenance costs: This differs depending on the type of turbine and the technology used. New turbines with new techniques have a cost between 1.5% to 2% per annum.

Component cost: It is the most important thing of the farm cost as the blades occupy 23.3%, the tower 18.9%, the gearbox 16.3%, the generator 3.4%, the pitch system 3.9 %, and the all other component costs are 31.4%.

Uses of Wind Energy

Besides using wind energy in producing electricity, people use it for many other purposes such as:

Wind sports and activities:
Many sports and activities use wind energy like windsurfing, land sailing, kite surfing, and kiteboarding.

Transportation:
Civilizations had used wind energy in transportation in the sailing form, as small and large ships can sail under wind power.

Food production:
Windmills use wind energy for food production purposes, such as for milling grain used for food like bread.

Pumping water:
We can also use wind pumps for pumping water as well as for draining the land.

Advantages of Wind Energy

While the advantages illustrate why wind farms occupy large importance, and there are many advantages of wind energy as:

  • It is a free renewable source that is plentiful and readily available.
  • Also, It is a clean source that doesn’t emit greenhouse gases or pollutants.
  • The wind is cost-effective as it’s one of the lowest-priced energy sources.
  • It can offer many jobs as the U.S wind sector employed more than 100000 workers in 2016.
  • People can build wind turbines anywhere on existing farms or ranches.
  • It is a space-efficient as we use free space for agricultural purposes.
  • Also, the wind turbines are relatively low maintenance.

Disadvantages of Wind Energy

There are some drawbacks to wind energy, such as:

  • Initial costs are so high.
  • The unreliability of the wind.
  • Also, we need a storage device to hold generated power when there isn’t enough wind.
  • It’s noisy and may cause aesthetic pollution.
  • Also, the blades may damage the local wildlife like the birds flying into the spinning turbine blades.

Nonetheless, there are some opinions to use batteries to store wind power for peak demand times, making wind power more popular.

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