Wind power is one of the fastest-growing renewable energy technologies, it describes the process by which the power of an inexhaustible resource that is wind is converted into mechanical power or electricity. This conversion is made possible by the movement of turbines or wind energy conversion systems.
The mechanical power generated can either be used for specific tasks such as grinding grain and pumping water or converted into electricity using a generator. (Source: energy.gov)
Wind turbines emerged more than a century ago, wind power generation took place in the United Kingdom and the United States in 1887 and 1888, and It is considered that modern wind power was first developed in Denmark, where horizontal-axis wind turbines were built in 1891 and a 22.8-metre wind turbine began operation in 1897. (Source: irena.org)
How it works
A wind turbine turns wind energy into electricity using the aerodynamic force from the rotor blades, that 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 a lift and drag force. The lift force being stronger causes the blades of the turbine to rotate and spin the rotor attached to them, this spinning movement changes the kinetic energy to rotational energy, that is then converted by the generator to electrical energy. As illustrated in the figure below. (Source: energy.gov)
The amount of power that can be harvested using wind hinges on the size of the turbine and the length of its blades, the output is proportional to the dimensions of the rotor and to the cube of the wind speed. In theory, the potential of wind power rises by a factor of eight when wind speed doubles.
In 1985, turbines had a rated capacity of 0.05 megawatts (MW) and a rotor diameter of 15 meters. Today’s new wind power projects have turbine capacities of about 2 MW onshore and 3–5 MW offshore. (Source: irena.org)
Types of wind turbines
There are two main types of wind turbines, Horizontal-axis turbines and Vertical-axis turbines.
Horizontal-axis turbines (HAWT)
Horizontal axis wind turbines are the most commonly used turbines owing to their strength and efficiency.
The base of the towers has to be very sturdy in order to allow the rotor shaft to be installed at the top of the tower, which enables the turbine to be exposed to stronger winds. The rotation of the blades can generate more power compared to the vertical axis wind turbine since the blades of the turbine are perpendicular to the wind.
However, the construction of this type of turbine requires a heavy support for the tower to support the weight of the blades, gearbox and generator. (Source: energyeducation.ca)
Vertical-axis turbines (VAWT)
Vertical axis wind turbines are less affected by frequent wind direction changes compared to the horizontal axis wind turbines since the blades are rotated on the rotor shaft perpendicular to the ground.
The shaft is installed near ground level, which enables easier maintenance of the turbines. Disadvantages to this turbine installation is that the efficiency is lower due to air drag and the lower wind speeds. (Source: energyeducation.ca)
These two types of turbines are illustrated in the figure below.
Types of wind energy
There are two types of wind energy, onshore wind energy and offshore wind energy.
Onshore wind energy is produced through large installations of wind turbines located on land, (onshore wind farms). Whilst offshore wind energy is produced through large installations located in bodies of water, (offshore wind farms) as illustrated by the figure below. (Source: storymaps.arcgis.com)
The largest offshore wind farm in the world is called the Walney Extension, it is located in the Irish Sea approximately. It covers a massive area of 149 square kilometers (56 square miles), which makes this wind farm bigger than the city of San Francisco, California, or the island of Manhattan in New York. (Source: nationalgeographic.org)
Wind energy data
According to the International Renewable Energy Agency (IRENA):
Global installed wind-generation capacity onshore and offshore has increased by a factor of almost 75 in the past two decades, jumping from 7.5 gigawatts (GW) in 1997 to some 564 GW by 2018 and about 733 GW at the end of 2020 covering 16% of EU electricity demand in 2020. (Source: irena.org)
According to Wind Europe wind power numbers daily:
-Share of wind energy in electricity demand accounted for 12.6% in November,4rd 2021. 11.3% was generated by onshore farms which equals to about 947 GWh and 1.4% was generated by offshore farms, that’s about 116 GWh.
-Share of wind energy in electricity demand accounted for 21.9% in November,6th 2021. 18.4% was generated by onshore farms which equals to about 1377 GWh and 3.4% was generated by offshore farms, that’s about 258 GWh. (Source: windeurope.org)
The following figure gives numbers of European wind energy generation in 2020, offshore and onshore data and highest country shares.
The following figure gives wind energy and solar energy prices compared to natural gas, coal and nuclear.
As shown in the figure below, the most ambitious scenario by the Global Wind Energy Council (GWEC) shows that a global wind energy capacity growth of about 1,000GW by 2020 and 2,400 GW by 2030 would result in annual CO2 savings of more than 1.5 billion tons in 2020 and 3.2 billon tons in 2030. (Source: gwec.net)
