A wind turbine blade is provided including a first and a second blade component connected with each other in an overlap region by thermal welding, the first blade component including a blade shell, a resistive element arranged between the first and second blade components in the overlap region as a remnant of the thermal welding, and an electrically conductive element extending through the blade shell and being electrically connected to the resistive element for supplying power to the resistive element during the thermal welding. The first and second blade components can be joined by thermal welding. Further, the resistive element used as heating element for thermal welding can be heated by electrical current even when the resistive element is difficult to assess from the interior cavity of the blade.

Provided herein are duct support systems and methods for installing and supporting a flexible duct in an interior of a wind turbine blade. The system comprises a duct support including an eyelet and at least one bonding surface, wherein the bonding surface is glued to an interior surface of the wind turbine blade near a tip of the wind turbine blade, and a cable, wherein the cable is connected to a tip-most end of the flexible duct, the cable passes through the eyelet of the duct support, and the cable passes through the flexible duct, whereby the flexible duct can be retracted from or deployed to the tip of the wind turbine blade by pulling the cable in a respective direction.