Wind farm blockage

A system, comprising:

• a physical measurement apparatus comprising a plurality of physical measurement masts for location at a site of a proposed wind farm and at least one data recorder connected to the physical measurement masts;
• a computer system communicatively coupled with the data recorder and being arranged to:
• receive a definition of the wind farm, the definition including at least a layout of a plurality of wind turbines of the wind farm at a predetermined site and rotor size of each of the plurality of wind turbines;
• model a wind field of the wind farm for each of a plurality of freestream wind speeds in each of a plurality of wind directions;
• define locations for a plurality of virtual measurement masts upstream of upstream turbines in each of the plurality of wind directions, wherein the upstream turbines are defined relative to the wind direction and the locations are defined at a horizontal distance from each upstream turbine for identifying wind farm blockage effects;
• determine a wind farm blockage factor for each of the plurality of freestream wind speeds in each of the plurality of wind directions, the wind farm blockage factor being based on wind speed data from the plurality of virtual measurement masts located in the modelled wind field at the locations defined for the wind direction;
• receive, from the data recorder, a plurality of measurements indicating wind speed and wind direction from at least one of the physical measurement masts located at the site of the wind farm;
• and
• determine an annual energy production for the wind farm based on one or more adjusted wind speeds obtained by applying one or more determined wind farm blockage factors to one or more measurements from the physical measurement masts.

A method for determining annual energy production of a proposed wind farm, the method comprising:

• receiving a definition of the proposed wind farm, the definition including at least a layout of a plurality of wind turbines of the wind farm at a predetermined site and rotor size of each of the plurality of wind turbines;
• modelling a wind field of the wind farm for each of a plurality of freestream wind speeds in each of a plurality of wind directions;
• defining locations for a plurality of virtual measurement masts upstream of upstream turbines in each of the plurality of wind directions, wherein the upstream turbines are defined relative to the wind direction and the locations are defined at a horizontal distance from each upstream turbine for identifying wind farm blockage effects;
• determining a wind farm blockage factor for each of the plurality of freestream wind speeds in each of the plurality of wind directions, the wind farm blockage factor being based on wind speed data from the plurality of virtual measurement masts located in the modelled wind field at the locations defined for the wind direction;
• receiving a plurality of measurements indicating wind speed and wind direction from at least one physical measurement mast located at the site of the proposed wind farm;
• determining an annual energy production for the proposed wind farm based on one or more adjusted wind speeds obtained by applying one or more determined wind farm blockage factors to one or more measurements from the at least one physical measurement mast;
• and
• constructing a physical wind farm comprising the plurality of wind turbines according to the layout of the plurality of wind turbines.