Wind turbine blade comprises a first and a second electric conductor extending in the longitudinal direction of the blade, and one or more electric heating elements for heating the surface of the blade. The methods include methods of treating a hyper- or hypocholesterolemic mammal comprising contacting the mammal with synthetic compounds having FXR receptor activity. The heat extraction system further includes a pump in fluid communication with the cold plate and a heat exchanger in fluid communication with the pump and the cold plate. The inventive skate also includes a blade chassis.