Cooling a wind turbine

1 . A cooling system for a wind turbine, the cooling system comprising:

a fluid circuit arranged to convey a working fluid to and from at least one component of the wind turbine to exchange heat between the working fluid and the at least one component;

a main pump configured to circulate the working fluid around the fluid circuit; and

at least one branch line connected to the fluid circuit, said at least one branch line comprising:

an inlet arranged to receive working fluid from the fluid circuit;

an outlet arranged to return working fluid to the fluid circuit;

a branch pump arranged to pump working fluid through the at least one branch line from the inlet to the outlet; and

a cooling device arranged to cool working fluid flowing through the at least one branch line,

wherein an entirety of the working fluid in the at least one branch line is received from the fluid circuit.

2 . The cooling system of claim 1 , wherein the branch pump is operable to produce a variable output.

3 . The cooling system of claim 2 , wherein the branch pump comprises any of: a variable-frequency drive; a variable-voltage drive; and a variable-speed drive.

4 . The cooling system of claim 1 , wherein the at least one branch line comprises a valve configured to prevent fluid flow through the at least one branch line when the branch pump is inactive.

5 . The cooling system of claim 4 , wherein the valve is configured as a normally-closed valve.

6 . The cooling system of claim 1 , comprising a flow director that comprises a main inlet configured to receive working fluid from the fluid circuit, a main outlet configured to discharge working fluid into the fluid circuit, and a port connected to the outlet of the at least one branch line.

7 . The cooling system of claim 6 , wherein the flow director is configured to direct working fluid discharged from the outlet of the at least one branch line away from the inlet of the at least one branch line.

8 . The cooling system of claim 6 , wherein the flow director comprises a further port that is connected to the inlet of the at least one branch line.

9 . The cooling system of claim 8 , wherein the port and the further port of the flow director are at positions in the flow director that are at equal pressure when the branch pump is inactive.

10 . The cooling system of claim 8 , wherein the further port is disposed between the main inlet and the main outlet of the flow director.

11 . The cooling system of claim 6 , wherein the flow director comprises at least one axis of symmetry.

12 . The cooling system of claim 6 , wherein the flow director comprises a barrier that is configured to obstruct working fluid flowing from the outlet of the at least one branch line to the inlet of the at least one branch line.

13 . The cooling system of claim 12 , wherein the barrier is parallel to a direction of flow of working fluid through the fluid circuit.

14 . The cooling system of claim 12 , wherein the barrier is orthogonal to a direction of flow of working fluid discharged through the outlet of the at least one branch line.

15 . The cooling system of claim 12 , wherein the barrier extends between the inlet and the outlet of the at least one branch line.

16 . The cooling system of claim 6 , wherein the port is disposed between the main inlet and the main outlet of the flow director.

17 . A wind turbine comprising the cooling system of claim 1 .

18 . A method of cooling one or more components of a wind turbine with the cooling system of claim 1 , the method comprising:

operating the main pump to convey the working fluid around the fluid circuit to and from each component of the wind turbine, to exchange heat between the working fluid and each component; and

operating the branch pump to draw at least a portion of the working fluid into the at least one branch line that is connected to the fluid circuit and that comprises the cooling device arranged to cool the working fluid flowing through the at least one branch line.

19 . A cooling system for a wind turbine, the cooling system comprising:

a fluid circuit arranged to convey a working fluid to and from at least one component of the wind turbine to exchange heat between the working fluid and the at least one component;

a main pump configured to circulate the working fluid around the fluid circuit; and

at least one branch line connected to the fluid circuit, said at least one branch line comprising:

an inlet arranged to receive working fluid from the fluid circuit;

an outlet arranged to return working fluid to the fluid circuit;

a branch pump arranged to pump working fluid through the at least one branch line from the inlet to the outlet; and

a cooling device arranged to cool working fluid flowing through the at least one branch line,

wherein the at least one branch line is devoid of a wind turbine component, spaced from the branch pump, that heats the working fluid flowing through the at least one branch line.

20 . A cooling system for a wind turbine, the cooling system comprising:

a fluid circuit arranged to convey a working fluid to and from at least one component of the wind turbine to exchange heat between the working fluid and the at least one component;

a main pump configured to circulate the working fluid around the fluid circuit; and

at least one branch line connected to the fluid circuit, said at least one branch line comprising:

an inlet arranged to receive working fluid from the fluid circuit;

an outlet arranged to return working fluid to the fluid circuit;

a branch pump arranged to pump working fluid through the at least one branch line from the inlet to the outlet; and

a cooling device arranged to cool working fluid flowing through the at least one branch line,

wherein an entirety of the working fluid in the at least one branch line flows through the cooling device in the at least one branch line before being returned to the fluid circuit.