Heating mats arranged in a loop on a blade

1. A blade for a wind turbine, the blade comprising:

a heating mat for generating heat is mounted at an outer surface of the blade, the heating mat comprising a first section with a first end section and a second section with a second end section, the first end section and the second end section are electrically connectable to a respective power terminal for supplying power to the heating mat,

wherein the second end section defines an opposite end section of the heating mat in a longitudinal direction of the heating mat with respect to the first end section, and

wherein the first section and the second section run along the surface of the blade in at least one loop from the first end section to the second end section; wherein the first section and the second section are arranged such that the first section and the second section at least partially overlap each other and an insulation layer is interposed between the first section and the second section.

2. The blade according to claim 1 , further comprising:

a power transmitting section located on the outer surface of the blade, the power transmitting section comprising the power terminals for supplying power to the heating mat,

wherein the first end section and the second end section are located inside the power transmitting section and are electrically connected to the power terminals, and

wherein the first section runs from the first end section to a region being located outside of the power transmitting section and the second section extends from the region being located outside of the power transmitting section to the second end section inside the power transmitting section.

3. The blade according to claim 2 , further comprising:

a root end section with a fixing element for fixing the blade to a hub of the wind turbine; and

a tip end section,

wherein the power transmitting section is formed within the root end section, and

wherein the first section and the second section meet at a location in the tip end section.

4. The blade according to claim 1 , wherein the heating mat comprising carbon fibres for generating heat.

5. The blade according to claim 1 , wherein the heating mat is foldable for forming the loop.

6. The blade according to claim 1 , wherein the first section and the second section are mounted to the outer surface such that between the first section and the second section a distance between each other is kept.

7. The blade according to claim 1 , wherein the power terminals comprise an input power terminal and an output power terminal, and wherein the first end section is connected to the input power terminal and the second end section is connected to the output power terminal.

8. The blade according to claim 1 , wherein the heating mat further comprising a third section extending parallel to the first section or to the second section.

9. The blade according to claim 8 , wherein the third end section is electrically connectable to a respective power terminal for power input or power output.

10. The blade according to claim 1 , further comprising:

a further heating mat for generating heat, wherein the further heating mat is mounted at the outer surface of the blade,

wherein the further heating mat comprises a further first section with a further first end section and a further second section with a further second end section, the further first end section and the further second end section are electrically connectable to a respective power terminal for supplying power to the further heating mat,

wherein the further second end section defines an opposite end section of the further heating mat in a further longitudinal direction of the further heating mat with respect to the further first end section, and

wherein the further first section and the further second section extends along the surface of the blade in one or more loops from the further first end section to the further second end section.

11. A method for controlling the heating of the heating mat of the blade according to claim 1 , the method comprising

measuring and controlling the electrical power input to the heating mat by a control unit.

12. The method according to claim 11 , further comprising:

controlling the heating of the heating mat in dependency of a measured electrical conductivity of the heating mat.

13. A method of manufacturing a blade with a heating system for a wind turbine, the method comprising:

mounting a heating mat for generating heat at an outer surface of the blade of the wind turbine, wherein the heating mat comprises a first section with a first end section and a second section with a second end section, the second end section defines an opposite end section of the heating mat in a longitudinal direction of the heating mat with respect to the first end section; and

electrically connecting the first end section and the second end section to a respective power terminal,

wherein the first section and the second section run along the surface of the blade in one or more loops from the first end section to the second end section,

wherein the first section and the second section are arranged such that the first section and the second section at least partially overlap each other and an insulation layer is interposed between the first section and the second section.