Calculating a return period wind speed

A method, comprising:

• selecting a proposed wind turbine site at which the wind turbine is to be located;
• using one or more wind speed sensors, measuring wind speeds at the proposed wind turbine site during a measurement period;
• calculating a wind speed associated with a return period for the proposed wind turbine, comprising;
• providing wind speed measurements measured at the proposed wind turbine site during the measurement period;
• selecting a first set of storms from the wind speed measurements;
• determining a characteristic wind speed for each storm of the first set of storms;
• providing a first set of modelled wind speeds, wherein the first set of modelled wind speeds are estimates of wind speeds at the proposed wind turbine site during the measurement period from a mesoscale data set;
• selecting a second set of storms from the first set of modelled wind speeds;
• determining a characteristic wind speed for each storm of the second set of storms;
• comparing the characteristic wind speeds of the first set of storms to the characteristic wind speeds of the second set of storms to determine a correction factor;
• providing an extended set of modelled wind speeds, wherein the modelled wind speeds are estimates of wind speeds at the proposed wind turbine site during an extended period from an extended mesoscale data set, and the extended period has a greater duration than the measurement period;
• selecting a third set of storms from the extended set of modelled wind speeds;
• determining a characteristic wind speed for each storm of the third set of storms;
• applying the correction factor to the characteristic wind speeds of the third set of storms to provide corrected characteristic wind speeds;
• and
• calculating the wind speed associated with the return period from the corrected characteristic wind speeds;
• and
• altering a design parameter of the wind turbine based on the wind speed associated with the return period.