Offshore wind turbine with liquid-cooling

• US 6,520,737 B1
• Filed: 04/26/2002
• Issued: 02/18/2003
• Est. Priority Date: 05/07/1999
• Status: Expired due to Term

• Current Assignee: MHI Vestas Offshore Wind A/S (Vestas Wind Systems A/S)
• Original Assignee: NEG Micon A/S (Vestas Wind Systems A/S)
• Inventors: Fischer, Torsten, Vilsbøll, Niels
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): NGUYEN, NINH H
• Application Number:
  US09/959,778
• Time in Patent Office: 298 Days
• Field of Search: 415/3.1, 415/4.3, 415/4.5, 415/175, 415/177, 415/908, 290/44, 290/55
• US Class Current: 415/4.3
• CPC Class Codes: F03D 13/25 specially adapted for offshore installation
• CPC Class Codes: F03D 15/00 Transmission of mechanical power
• CPC Class Codes: F03D 80/60 Cooling or heating of wind motors
• CPC Class Codes: F05B 2240/95 offshore
• CPC Class Codes: F16L 39/04 allowing adjustment or movement of the multiline swivel type F16L39/06
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/727 Offshore wind turbines
• CPC Class Codes: Y10S 415/908 Axial flow runner

Abstract

An offshore wind turbine is disclosed wherein the power transmission in the nacelle is cooled by means of a liquid conducted to the nacelle from the tower on which the nacelle is pivotally arranged around a vertical yawing axis. The liquid transfers heat to the seawater near the turbine which is used as a heat sink of low temperature and enormous heat capacity as compared to traditional air cooling. The liquid is conducted in a closed circuit and the cooling system may comprise more than one cooling circuit. The flow of cooling-liquid may be conducted between the tower and the nacelle through a heat transfer unit having a first part that is stationary with respect to the tower and a second part that is stationary with respect to the nacelle. The parts have at least one annular passageway for a liquid flow defined between abutting surfaces of the parts.

Claims

1. An off-shore wind turbine comprising

a stationary part including a tower extending substantially vertically,

a nacelle comprising a wind rotor having at least one blade arranged on a main shaft having a substantially horizontal rotation axis, and a power transmission system,

a yawing system comprising a stationary part being fixed to an upper end of the tower and a movable part being fixed to the nacelle, the stationary part and the movable part being designed so that the nacelle is being supported vertically and horizontally by the tower and may pivot relatively to the tower about a substantially vertical yawing axis, and

a cooling system for transferring excessive heat from the power transmission system to seawater surrounding the wind turbine, the cooling system comprising first conduction means for conducting a flow of cooling liquid from the stationary part of the wind turbine and to the nacelle during normal operational conditions and at most positions of the nacelle relative to the tower, pumping means for pumping the flow of cooling liquid through the first conducting means and first heat exchanging means for transferring heat from the power transmission system to the cooling liquid.

2. A wind turbine according to claim 1, wherein the cooling system further comprises second conduction means for conducting the flow of liquid from the nacelle and to the stationary part of the wind turbine during normal operational conditions and at most positions of the nacelle relative to the tower, the first conduction mean and the second conduction means forming part of a single circuit.

3. A wind turbine according to claim 2, wherein the circuit is a closed circuit and the cooling system further comprises second heat exchanging means for transferring heat from the cooling liquid to the seawater, the second heat exchanging means being placed in or in the vicinity of the stationary part of the wind turbine.

4. A wind turbine according to claim 3, wherein the closed circuit is formed so that the cooling liquid therein can be pressurised, the closed circuit being sealed off from the environment in a substantially pressure-proof manner, and wherein the cooling liquid at least substantially fills the interior of the circuit.

5. A wind turbine according to claim 3, wherein the pumping means for pumping the flow of the cooling liquid through the closed circuit is solely situated in the nacelle.

6. A wind turbine according to claim 3, wherein the second heat exchanging means is placed near an upper end of the tower.

7. A wind turbine according to claim 3, wherein the second heat exchanging means is placed near a lower end of the tower.

8. A wind turbine according to claim 3, wherein the cooling system further comprises second pumping means for forcing a flow of the seawater past heat exchanging surfaces of the second heat exchanging means.

9. A wind turbine according to claim 3, wherein the cooling liquid is an oil.

10. A wind turbine according to claim 9, wherein the closed circuit comprises a lubrication circuit of at least a part of the power transmission system, the oil being a lubricant of said part of the power transmission system.

11. A wind turbine according to claim 3, wherein the cooling liquid comprises water.

12. A wind turbine according to claim 11, wherein the cooling liquid further comprises an agent for lowering the freezing temperature of the water.

13. A wind turbine according to claim 12, wherein the agent is glycerol.

14. A wind turbine according to claim 4, wherein the cooling system further comprises at least one further closed circuit according to any of said claims for conducting a flow of a cooling liquid between the nacelle and the stationary part of the wind turbine during normal operational conditions and at most positions of the nacelle relative to the tower.

15. A wind turbine according to claim 14, wherein the at least two circuits of the cooling system comprises different types of cooling liquids.

16. A wind turbine according to claim 1, wherein the liquid flowing in the conduction means of the cooling system is seawater.

17. A wind turbine according to claim 1, wherein the tower is hollow, partly submerged into the sea and partly filled with seawater, the heat from the power transmission system being transferred to said seawater within the tower by means of the cooling system.

18. A wind turbine according to claim 1, wherein the cooling system comprises system control means for controlling its operation, the control means comprising

a plurality of temperature sensors each adapted for detecting a temperature of a part of the transmission system or the cooling liquid and for producing an output accordingly to the system control means,

heat exchanger control means for controlling the operation of at least two heat exchanging means of the first heat exchanging means, said at least two heat exchanging means transferring heat from separate parts of the power transmission system, and

pump control means for controlling the operation of the pumping means, the system control means being adapted to control the operation of the cooling system so that the temperature of the parts of the power transmission system is aimed to be within predefined temperature ranges.

19. A wind turbine according to claim 18, wherein the cooling system further comprises a heat pump arranged for transferring heat from the seawater to the cooling liquid so as to heat the cooling liquid, the system control means being adapted to control the cooling system to raise the temperature of parts of the power transmission system if the temperature of said parts is below a predetermined threshold value.

20. A wind turbine according claim 1, wherein an opening is defined between the nacelle and the tower, said opening being positioned so that the vertical yawing axis passes through the opening, at least one power cable for transferring power from the power transmission system passes through the opening.

21. A wind turbine according to claim 20, wherein at least one liquid conducting means forming part of the cooling system passes through the opening.

22. A wind turbine according to claim 21, wherein at least one of the at least one liquid conducting means is a pipe being concentric with the vertical yawing axis.

23. A wind turbine according to claim 22, wherein at least one of the liquid conducting means is a flexible hose.

24. A wind turbine according to claim 21, further comprising heat isolating means between at least one of the at least one power cable and at least one of the at least one liquid conducting means so as to-reduce heat transfer there between.

25. A wind turbine according to claim 20, wherein the wind turbine comprises drive means for driving the pivoting of the nacelle relatively to the tower and control means for controlling said drive means so that the nacelle will pivot less than a predetermined number of turns relatively to a predetermined position of the nacelle so as to prevent excessive twisting of flexible parts passing through the opening and being fixed at one end to the nacelle and at an other end to the stationary part.

26. A wind turbine comprising

a stationary part including a tower extending substantially vertically,

a nacelle comprising a wind rotor having at least one blade arranged on a main shaft having a substantially horizontal rotation axis and a power transmission system,

a yawing system comprising a stationary part being fixed to an upper end of the tower and a movable part being fixed to the nacelle, the stationary part and the movable part being designed so that the nacelle is being supported vertically and horizontally by the tower and may pivot relatively to the tower about a substantially vertical yawing axis, and

a cooling system for transferring heat from the power transmission system and comprising first conduction means for conducting a flow of cooling liquid from the stationary part of the wind turbine and to the nacelle during normal operational conditions and at most positions of the nacelle relative to the tower, pumping means for pumping the flow of cooling liquid through the first conducting means and first heat exchanging means for transferring heat from the power transmission system to the cooling liquid, the cooling system further comprising

a transfer unit for transferring liquid between the nacelle and the stationary part of the wind turbine, the unit comprising a first part being at least substantially stationary relatively to the tower and a second part being at least substantially stationary with respect to the nacelle, the first part and the second part being designed so that at least one passage way for a liquid flow is defined between substantially abutting surfaces of the parts during normal operational conditions and at most positions of the nacelle relatively to the tower, the passage way being part of the first conduction means of the cooling system for conducting the flow of cooling liquid.

27. A wind turbine according to claim 26, wherein at least a part of the at least one passage way for the liquid flow between the nacelle and the stationary part of the wind turbine is defined by means of a surface of the first part, a surface of the second part and by means of a first and of a second sealing means.

28. A wind turbine according to claim 27, wherein the first and the second sealing means each forms a circle with its centre on the vertical yawing axis and each of the first and the second sealing means extends in a plane being perpendicular to the yawing axis, whereby an annular passage way for liquid flow is defined between the first and the second sealing means and said surfaces of the first and the second part.

29. A wind turbine according to claim 28, wherein the first and the second sealing means extend in substantially the same plane and form concentric circles.

30. A wind turbine according to claim 28, wherein the first and the second sealing means extend in planes having a mutual distance along the vertical yawing axis.

31. A wind turbine according to claim 30, wherein the first and the second sealing means form circles having substantially the same diameter.

32. A wind turbine according to claim 30, wherein the first and the second sealing means form circles having different diameters.

33. A wind,turbine according to claim 27, wherein at least one of the sealing means comprises an O-ring formed from a resilient material.

34. A wind turbine according to claim 33, wherein only one of the first and second part of the transfer unit comprises a recess for retaining said O-ring.

35. A wind turbine according to claim 27, wherein at least one of the sealing means is a narrow clearance formed by surfaces of the first and the second part of the transfer unit so that said surfaces constitute a labyrinth packing.

36. A wind turbine according to claim 27, wherein at least one of the sealing means comprises a flexible elongated strip of which one edge is fixed to the first part, respectively to the second part, and the other edge is forced into abutting contact with a surface of the second part, respectively the first part.

37. A wind turbine according to claim 36, wherein the edge of the strip is forced into abutting contact at least partly by the pressure of the fluid.

38. A wind turbine according to claim 37, wherein the strip is formed from a resilient material and the edge of the strip is forced into abutting contact at least partly by resilient forces.

39. A wind turbine according to claim 26, wherein the first part and the second part of the transfer unit each has at least one channel formed therein between the exterior and each of the at-least one passage ways for a liquid flow defined between surfaces of the -parts of the transfer unit, said channels being parts of the conduction means for conducting a flow of liquid.

40. A wind turbine according to claim 26, wherein the transfer unit is supported by the tower and the second part is induced to follow the pivotal movements of the nacelle by a carrier mounted on the second part and engaging with the nacelle.

41. A wind turbine according to claim 26, wherein the transfer unit is supported by then nacelle and the first part is induced to remain stationary with respect to the tower by a carrier mounted on the first part and engaging with the tower.

42. A wind turbine according to claim 26, wherein the transfer unit constitutes an integrated part of a yaw bearing of the yawing system, said bearing being designed for absorbing forces between the nacelle and the tower.

43. A wind turbine according to claim 26, wherein more than one passage way for a liquid flow for the cooling system is defined similar to the one described.

44. A wind turbine according to claim 26, wherein at least a part of the transfer unit is formed from a synthetic material.

45. A wind turbine according to claim 26, wherein at least a part of the transfer unit is formed from an aluminium alloy.

46. A wind turbine according to claim 26, wherein at least a part of the transfer unit is formed from a stainless steel alloy.

47. A wind turbine according to claim 26, wherein at least a part of the transfer unit is formed from cast iron.