System and method for ground based inspection of wind turbine blades
A ground based wind turbine blade inspection system and method consists of a thermal imaging camera configured to detect propagating defects by acquiring thermal imaging data from a wind turbine blade when it is substantially at thermal equilibrium with respect to surrounding air and analyzing the thermal imaging data with a processor to identify thermal effects associated with latent defects caused by internal friction due to cyclic gravitational stresses and wind loads during normal turbine operation. The system permits latent defects to be identified using a ground-based in situ inspection before they become visually apparent, which allows repairs to be made economically while the blade is in place.
1. A method of remotely inspecting blades of a wind turbine in situ, the method comprising:
capturing one or more images of at least a portion of each wind turbine blade with a thermal imaging camera as each blade passes through a field of view of the thermal imaging camera while the wind turbine is rotating and undergoing cyclic load due to gravity and variations in wind loads and when the blade has substantially reached thermal equilibrium with ambient air after sunset in order to produce thermal imaging data;
analyzing the thermal imaging data to identify atypical thermal patterns due to thermoelastic heating and/or frictional heating within or around defects within the blades; and
determining at least one dimension of at least one of the defects identified within the blades.
2. The method of claim 1 , further comprising:
calibrating an image scale in at least one of the one or more images using a diameter of a root end of one of the wind turbine blades.
3. The method of claim 2 , wherein the image scale is given by pixels per a selected unit of length.