Site-specific wind characteristics pertinent to wind turbines include:
- Mean wind speed: Only interesting as a headline figure, but does not tell how often high wind speeds occur.
- Wind speed distribution : diurnal, seasonal, annual patterns.
- Turbulence: short-term fluctuations.
- Long-term fluctuations.
Mean Wind Speed and Energy Distribution: The mean wind speed can be defined as time-averaged wind speed, averaged over a specified time interval. The mean wind speed varies with elevation above mean sea level and the averaging time interval; a standard reference elevation is 10 m and a standard time interval is 1 h. In practice this implies that we should carefully define our energy demands
- Minimum energy production (water/electricity) per week/month/year. This value, together with the average wind speed, will give the minimum rotor size (and a first estimate of cost price).
- Allowance of no energy production during a certain period (giving an impression about water storage tanks or batteries).
- Time of the year that the system is really producing energy.
In order to decide whether or not a wind energy system will satisfy our energy needs, we have to know more about the prevailing wind speeds at the future wind turbine site.
