How is wind power productivity measured?
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vol. 10
8 March 2023
MEASURING WIND POWER POTENTIAL
By Edoardo Simonelli, Eleonora Cacchio
Global Wind Day is still far away, but we just can’t wait until 15th June to celebrate wind power and tell you about the potential of wind.
First of all, what is wind? It is essentially kinetic energy produced by the movement of air from high-pressure to low-pressure zones, which is then converted via the use of wind turbines into mechanical and eventually electrical energy.
Wind power is among the oldest sources of energy, and was used as early as 3500 B.C. by the Egyptians to manoeuvre boats along the Nile.
Wind speed is measured by means of an anemometer, from the Greek anemos (wind) and metron (measurement), which is an instrument that can detect changes in the physical properties of an air stream and quantify it in multiple scales of wind speed measurement (m/s, km/h, ft/min, MPH and knots). But wind speed is only one factor that determines the extractable power from the wind, the others being air density and swept air, which comes from the radius of the air turbine blades.
The orographic conformation of the terrain must also not be underestimated since natural (e.g., hills) or man-made obstacles (such as buildings) in the terrain exert a frictional force on moving air masses causing the wind to thicken in the higher layers of the atmosphere. For this reason, in areas characterized by significant roughness such as mountainous areas, the average wind profile steeply increases with increasing altitude.
In general, to calculate wind productivity in a given geographical area, it is necessary to cross-reference the data of the frequency distribution of different wind speeds over a certain period (at least one year) with those of the power curve of a wind generator.
Today, the world’s largest wind turbine is the Haliade-X, that is installed in the port area of Rotterdam (NL), 248×220 meters in size and capable of yielding 14 MW of maximum power which is enough to power up to 12’000 households.
But this record may soon be surpassed either by the German-Spanish SG 14-222 DD wind turbine installed in Thy National Park (Østerild locality, DK), which is estimated to be able to supply electricity to 18’000 households or by the Danish V236-15.0 MW wind turbine, which will be able to power up to at least 20’000 households thanks to its annual energy production of 80 GWh.