Mitigating adverse wake effects in a wind farm using non-optimum operational conditions

• An operational strategy is developed for a wind farm in complex terrain.
• The strategy employs non-optimum turbine operation to increase total farm power.
• The operational strategy is derived using a novel CFD approach.
• The CFD approach allows simultaneous simulation of atmospheric flow and wakes.
• The approach is well suited for operational optimisation of existing farms.

Non-optimum operation of wind turbines is used in wind farm control to mitigate adverse wake effects, which result in a lower annual energy yield of wind farms. The current study investigates an operational strategy where upstream turbines are operated at non-optimum conditions thereby weakening the wakes. This approach is demonstrated for an existing wind farm in complex terrain. The computational fluid dynamics method allows the atmospheric flow and wakes, as well as their interaction with the terrain, to be accurately and simultaneously simulated. For a given wind direction, a 12.5% reduction relative to optimum in the power coefficient of an upstream turbine results in a 2.5% increase of the sum power production of the upstream and downstream turbine. The non-optimum operation can be accomplished with a 3.5° change in the blade pitch angle of the upstream turbine. The demonstrated approach in this work is thus well suited for the development of more advanced and complex operational strategies for other existing wind farms.