Anemometers are a very important equipment of the wind turbines. They obviously allow to monitor produced power for a certain wind speed (with the known uncertainties due to the blades) but they also trigger the start and stop of the turbines (cut-in /cut-out speed).
Cup anemometers are very sensitive to environmental events such a lightning, ice, or even birds which can damage and alter the functioning. The tilt angle can have a big influence on the performance of the turbine as shown below
A 5 degree tilt can increase or decrease the wind speed value of 2%. The impact is even more important for a 15 degree (8%). This impact will translate of the turbine with incoherent power curve and turbines starting at the wrong cut-in speed and stopped at the wrong cut-out speed impacting the production. The consequences can be even worse with safety issues link with turbine producing above the cut-out speed.
Besides solving safety issues, measuring the right wind speed will increase the production by allowing the turbine to start and stop at the right cut in/out speed. The typical situation for a cup anemometer is the tilted inflow from below, i.e. the wind has an upward component which means the wind speed will be sur-evaluated and the turbine will try to start soon without being able to produce.
It is also essential to be measuring the right wind speed in order to monitor closely the power curve and detect potential degradations which will impact the production.
Greensolver strongly advises to check on regular basis the state of the cup anemometers or to add an ultrasonic anemometer to improve the turbine production.