Wind Power


Wind is not homogeneous along the space. Its distribution depends on:

  • The Earth’s rotation
  • Geography
  • Temperature gradients

The kinetic energy has to be converted into useful energy. To achieve that, wind reaches the wind turbines that convert the kinetic energy into mechanical power thanks to the blade motion. This mechanical power can be converted into electricity thanks to a generator for power supply.



There are places in the world that are more suitable than others for wind power harvesting. This suitability depends mainly on the wind speed. Here is an interactive map where we can observe the speed of the wind the world.

A wind speed between 3,5 and 6,5 m/s is suitable. Wind turbines efficiency depends mainly on:

  • Wind power: the faster is the wind speed the greater amount of power can be obtained by a wind turbine.
  • Blades. The design of blades is a very important factor. They must have the suitable shape and size.
  • Altitude: higher altitude places have faster wind speeds. For this reason, these places are the most suitable. A problem is that some places with high altitude are not accessible.
  • Obstructions: trees, buildings and others can create forms of friction that can change the direction or speed of the wind. The project viability is greater in places with no obstructions.
  • Air temperature: the power from a wind turbine increases as the temperature decreases because the cold air is denser and it goes down.

Types of Wind Turbines

Wind turbines can be classified according how it rotates about a horizontal or a vertical axis


Turbines with a horizontal axis have the main rotor and electrical generator at the top of a tower. Small turbines have a simple wind blade, while large turbines use a wind sensor with a servo motor. Most have a gearbox, which turns the rotation into a quicker rotation to achieve a higher efficiency. Turbines that are used in wind farm for large-scale electrical production are normally three-bladed and have computer-controlled motors

Horizontal axis wind turbines can be onshore wind turbines or offshore wind turbines. The advantages of using onshore wind turbines are that they can be easily integrated with electrical grid network, they have an affordable installation and they have a low cost in maintenance operations. The mainly problem of onshore wind turbines is that they are affected to more turbulence in wind.

On shore wind turbines

The main advantages of offshore wind turbines are:

  • Obstruction elements in the water surface are less than in land.
  • Noise pollution is not a problem in the sea.
  • Less affected to turbulence in wind.

However, they are more expensive since their integration to the electrical grid is more complex. Maintenance is also more complex and costly than in onshore wind turbines.

On shore wind turbines

According to the design of the blades, horizontal axis wind turbines can be classified as:


These turbines operate with the blades upwind to the tower. Small-scale wind turbines use a tail vane to keep the blades facing into the wind


They operate in a downwind mode. In this way, the wind passes the tower before striking the blades. The machine rotor tracks the wind in a downwind mode without using a tail vane.


These turbines have an augmentor that increases the amount of wind passing through the blades.

Types of Horizontal Turbines



Wind turbines with vertical axis do not need to be pointed into the wind. This is an advantage in places where the wind direction is highly variable.


They have good efficiency but poor reliability. They also generally require some external power source, or an additional Savonius rotor to start turning. The torque ripple is reduced by using three or more blades which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area.

Darrieus Wind Turbine
Giromill Wind Turbine

Giromill wind turbine is a subtype of Darrieus turbine with straight vertical blade sections attached to the central tower with horizontal supports. Vertical blades change their orientation whilst the rotation of the rotor occurs for a greater use of the force of the wind.


The Savonius turbine is a drag-type device, consisting of two or three scoops. The scoops experience less drag when moving against the wind than when moving with the wind.The differential drag causes the wind turbine to spin. Savonius turbines are used whenever cost or reliability is much more important than efficiency. For this reason, anemometers are Savonius wind turbines since the efficiency is not as important as the reliability. Much larger Savonius turbines have been used to generate electric power in such places where small amounts of power and a low cost of maintenance are needed.

Savonius Wind Turbine
Twisted Savonius


Twisted Savonius turbine is similar to Savonius wind turbines. The difference is that they have longer helical scoops to provide smooth torque. They are normaly used as a rooftop windturbine and have been adapted for ships.

Benefits to the environment

GHG emission reduction, displacing fossil fuels. It is estimated that 160 GW of wind power capacity could generate 340 TWh/yr of electricity and save more than 0,2 Gt CO2/year. Global Wind Energy Council (GWEC) results show that wind energy could achieve up to 65 percent of the emissions reductions pledged by industrialized nations.

Wind energy requires a little amount of water to work.

Producing little waste.

The main disadvantage of the wind power is the huge size of the wind turbines.


IPCC has estimated that on- and offshore wind energy could contribute 7% of global electricity supply by 2030 and nearly 9% by 2050.

Wind turbine installations on depth water and large distances (to shore) are likely to increase.

The general trend in turbine design has been to  increase the height of the tower, the length of the blades and the power capacity



  • IMPLUX wind turbine: the turbine is enclosed, and the enclosure’s slats are spaced close together, it poses no danger to birds and produces very little noise compared to current turbine forms.
  • A company named Solar Aero has designed a wind turbine with no blades, a small footprint and, according to the designers, low enough maintenance costs.
  • Several companies, in various stages of development, are working on maglev turbines. Magnetic levitation, which has propelled clean-energy trains for years, has the potential to increase wind-turbine efficiency by up to 20 percent.
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