Wind, a renewable power now to be reckoned with

 wind, renewable power, Betz’ law, home wind turbineIn Greek mythology, Aeolus is the master and keeper of the winds. The wind’s kinetic force, sometimes referred to as “aeolian energy”, has been used by men since the Antiquity, with for instance the first sailing vessels and the first grain mills. Nowadays wind energy is harnessed to generate electricity thanks to wind turbines. How do they work? What is the share of wind power in worldwide electricity generation and how is it likely to evolve?

A rather simple energy transformation process

Contemporary wind turbines are nothing but a modern version of the old-fashioned windmill. The latter transforms the wind’s kinetic energy, i.e. the energy deriving from the wind’s speed, into mechanical energy in order to pump water for irrigation purposes or to drive a mill and make flour. Today’s wind turbines just replaced the millstone or the pump with an electric generator. Immense turbine blades measuring up to 100 metres in diameter are used to produce as much energy as possible. Wind sensors feed information into a computer which then controls the rotor’s movement so that it generates maximum power, whatever the wind [1].

Betz’ law expresses the maximum energy that can be derived from a wind turbine: P = .37.S.V3, with P being the power generated in Watts, S the blades’ surface in m2 and V the wind’s speed in metres per second (m/s). It should be noted that the power generated depends on the third power of the wind speed, which means that when the wind blows twice faster, 8 times more energy can be produced.

Industrial and domestic exploitation

The overwhelming majority of windmills are part of a large complex, a wind farm connected to the electricity distribution grid. However, it is also possible for households to purchase a home wind turbine to cover their electricity needs. But as yield is difficult to measure since it depends on weather conditions, return on investment of such an undertaking is still uncertain today.

A booming energy worldwide

According to the 2009 World Wind Energy Report, wind power generated 340 million MWh that year, that is to say 2% of the annual worldwide electricity consumption, which equals Italy’s yearly electricity needs. This proportion looks minute, but it has been growing steadily since the 1990s. Moreover, statistics vary widely across different countries and continents. According to the European Wind Energy Association, Europe is clearly a pioneer with a wind power capacity of 94,000 MW, which would be enough to cover 6.3% of the continent’s electricity needs. Moreover, the European wind power industry has experienced a 16% growth since 1995.

Every year in France, 500 new wind turbines are installed, generating another 1GW of electricity, as an average nuclear power plant would. Asian countries also prove to be great investors: in 2011 China was the leader of the wind turbine market, with 6,000 MW installed. The same year, India added an extra 3GW wind power capacity to reach 16,000 MW. Wind power capacity worldwide in 2011 represented 238 GW worth of installations, i.e. an impressive 20% growth from the prior year [2].

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[1] Comment ça marche, David Macaulay, Larousse
[2] Statistics from the Global Wind Energy Council

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