Floating wind energy harvesting apparatus with improved maintenance

Abstract

A floating VAWT comprising a wind turbine body having a lower body portion and an upper body portion; at least one blade attached to the upper body portion for converting wind energy to rotation of the wind turbine body; and an energy converter attached to the wind turbine body for converting the rotation of the wind turbine body to electrical energy. The energy converter comprises a first energy converter part, and a second energy converter part to be kept relatively stationary in relation to the first energy converter part. The energy converter is attached to the wind turbine body by means of a first releasable mechanical coupling between the first energy converter part and the lower body portion of the wind turbine body, and a second releasable mechanical coupling between the first energy converter part and the upper body portion of the wind turbine body.

Claims

1. A floating wind energy harvesting apparatus for offshore installation, said wind energy harvesting apparatus comprising: an elongated wind turbine body extending along a longitudinal wind turbine body axis, said wind turbine body comprising a lower body portion to be mainly below a water surface when the wind energy harvesting apparatus is in operation and an upper body portion to be mainly above the water surface when the wind energy harvesting apparatus is in operation; at least one blade attached to the upper body portion for converting wind energy to rotation of the wind turbine body around the longitudinal wind turbine body axis; and an energy converter attached to said wind turbine body for converting the rotation of said wind turbine body to electrical energy, said energy converter comprising a first energy converter part coupled to said turbine body for rotating in response to rotation of said wind turbine body, and a second energy converter part to be kept relatively stationary in relation to said wind turbine body, the resulting rotation of said first energy converter part in relation to said second energy converter part being converted to electrical energy by said energy converter, wherein said energy converter is attached to said wind turbine body by means of a first releasable mechanical coupling between said first energy converter part and said lower body portion of the wind turbine body, and a second releasable mechanical coupling between said first energy converter part and said upper body portion of the wind turbine body.

2. The floating wind energy harvesting apparatus according to claim 1, wherein said floating wind energy harvesting apparatus is configured in such a way that said energy converter is arranged above the water surface when the wind energy harvesting apparatus is in operation.

3. The floating wind energy harvesting apparatus according to claim 1, wherein: said upper body portion comprises a first body flange; said lower body portion comprises a second body flange; said first energy converter part comprises a first energy converter flange and a second energy converter flange; and said first body flange is releasably connected to said first energy converter flange, and said second body flange is releasably connected to said second energy converter flange.

4. The floating wind energy harvesting apparatus according to claim 3, wherein: said first body flange is releasably connected to said first energy converter flange by means of a first releasable fastening arrangement; and said second body flange is releasably connected to said second energy converter flange by means of a second releasable fastening arrangement.

5. The floating wind energy harvesting apparatus according to claim 4, wherein each of said first and second releasable fastening arrangement comprises a plurality of bolts and corresponding nuts.

6. The floating wind energy harvesting apparatus according to claim 3, wherein at least one of said first body flange and said second body flange comprises: a first set of holes for releasable attachment of said energy converter to said wind turbine body; and a second set of holes for temporary releasable attachment of a wind turbine body holding arrangement to said wind turbine body between said first body flange and said second body flange.

7. The floating wind energy harvesting apparatus according to claim 1, wherein said energy converter further comprises: a braking arrangement mechanically coupled to said first energy converter part and to said second energy converter part; and processing circuitry for controlling said braking arrangement to reduce a rotational speed of said first energy converter part in relation to said second energy converter part.

8. A method of replacing the energy converter of the floating wind energy harvesting apparatus according to claim 1, said method comprising the steps of: attaching a holding arrangement to said upper body portion and to said lower body portion, said holding arrangement being arranged and configured to maintain a relative arrangement of said upper body portion and said lower body portion; releasing said first releasable mechanical coupling and said second releasable mechanical coupling; reducing an axial force between said energy converter and each of said upper body portion and said lower body portion; removing said energy converter; arranging a replacement energy converter between said upper body portion and said lower body portion; attaching said replacement energy converter to said upper body portion and said lower body portion by means of said first releasable mechanical coupling and said second releasable mechanical coupling; increasing an axial force between said energy converter and each of said upper body portion and said lower body portion; detaching and removing said holding arrangement.

9. The method according to claim 8, wherein said energy converter is removed by, at least initially, displacing said energy converter in a direction substantially perpendicular to the longitudinal axis of said wind turbine body.

10. The method according to claim 8, wherein said floating wind energy harvesting apparatus comprises a braking arrangement for substantially preventing rotation of said wind turbine body, said method further comprising the step of: controlling said braking arrangement to prevent rotation of said wind turbine body before attaching said holding arrangement to said upper body portion and to said lower body portion.

11. The method according to claim 8, further comprising the steps of: providing a floating vessel carrying said holding arrangement and said replacement energy converter; and maneuvering said vessel, in relation to said wind turbine body, in such a way that said holding arrangement becomes arranged between said upper body portion and said lower body portion.

12. The method according to claim 8, wherein said step of reducing said axial force comprises the step of: heating said holding arrangement to expand said holding arrangement.

13. The method according to claim 8, wherein said step of reducing said axial force comprises the step of: cooling said energy converter to contract said energy converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:

(2) FIG. 1 is a schematic perspective view of a floating wind energy harvesting apparatus according to an example embodiment of the present invention;

(3) FIG. 2 is an enlarged view of the energy converter comprised in the wind energy harvesting apparatus in FIG. 1 and the connection between the energy converter and the lower and upper wind turbine body portions;

(4) FIG. 3 is a flow-chart schematically illustrating an example embodiment of the method according to the present invention;

(5) FIGS. 4a-b schematically shows an example of a floating vessel that may be used when carrying out the method of the flow-chart in FIG. 3; and

(6) FIG. 5 is a perspective view schematically illustrating the attachment of the holding arrangement to the wind turbine body prior to removing the energy converter.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(7) FIG. 1 schematically illustrates a floating wind energy harvesting apparatus in the form of a floating vertical axis wind turbine (VAWT) 1. In FIG. 1, the VAWT 1 is shown floating in the sea 2 and being exposed to wind 3.

(8) Referring to FIG. 1, the VAWT 1 comprises an elongated wind turbine body extending along a longitudinal wind turbine body axis 5. As is schematically indicated in FIG. 1, the wind turbine body comprises a lower body portion 7 mainly arranged below the water surface 8, and an upper body portion 10 mainly arranged above the water surface 8. The VAWT 1 further comprises blades 11a-c attached to the upper body portion 10, and an energy converter 12 attached to the wind turbine body between the lower body portion 7 and the upper body portion 10.

(9) As will be described below in further detail, the energy converter 12 comprises a first energy converter part 14 and a second energy converter part 15. The first energy converter part 14 is releasably mechanically coupled to the lower body portion 7 and the upper body portion 10 to rotate around the longitudinal wind turbine body axis 5 together with the lower 7 and upper 10 body portions. The second energy converter part 15 is coupled to an anchoring arrangement 17 via arm 18 to keep the second energy converter part 15 relatively stationary in relation to the first energy converter part 14.

(10) As is schematically shown in FIG. 1, the lower body portion 7 comprises a buoyancy-providing portion 20 and a ballast portion 21 that are dimensioned to keep the VAWT 1 generally vertical and the energy converter 12 above the water surface 8.

(11) The buoyancy-providing portion 20 may comprise a foam-filled space, making the VAWT 1 unsinkable, and a reservoir (not shown) for allowing control of the buoyancy of the VAWT 1. The reservoir may be controllably filled with water to control the level of the VAWT 1 to compensate for factors such as variations in the salt concentration in the water and organic growth on the lower body portion 7.

(12) When the wind 3 blows as is schematically indicated in FIG. 1, the forces resulting from the interaction between the wind and the blades 11a-c cause the wind turbine body to rotate around the longitudinal axis 5. This in turn results in rotation of the first energy converter part 14 in relation to the second energy converter part 15. This relative rotation is converted to electrical energy.

(13) Most parts of the VAWT 1 in FIG. 1 may be robust and can be made from relatively cheap and sturdy materials, such as steel and concrete, and will not be moving when in contact with anything but air or water. Therefore, most parts of the VAWT 1 are likely to be operational during the entire lifetime of the VAWT 1. However, the energy converter 12 may need maintenance or replacement at least at some time during the lifetime of the VAWT 1.

(14) To facilitate maintenance or replacement of the energy converter 12, the first energy converter part 14 is, as was described above, releasably mechanically connected between the lower body portion 7 and the upper body portion 10.

(15) An example of the configuration of the energy converter 12 and the mechanical connection between the energy converter 12 and the lower 7 and upper 10 body parts will now be described with reference to FIG. 2.

(16) As can be seen in FIG. 2, the upper body portion 10 comprises a first body flange 25, the lower body portion 7 comprises a second body flange 26, and the first energy converter part 14 comprises a first energy converter flange 27 and a second energy converter flange 28.

(17) The first body flange 25 is releasably connected to the first energy converter flange 27 by means of releasable fasteners, here in the form of bolts 30a-b and nuts 31a-b (all bolts and nuts are not visible in FIG. 2). In the same way, the second body flange 26 is releasably connected to the second energy converter flange 28 by means of bolts 32a-c and nuts 33a-c (all bolts and nuts are not visible in FIG. 2).

(18) As is schematically indicated in FIG. 2, the energy converter 12 comprises electrical wiring 35 for conducting electrical current generated by the energy converter 12 from the second energy converter part 15 to a remote location.

(19) Moreover, the energy converter 12 comprises a braking arrangement including a disc 37 attached to the first energy converter part 14, and brake calipers 38a-b attached to the second energy converter part 15. The brake calipers 38a-b are controlled by control circuitry (not shown in FIG. 2) included in the energy converter 12.

(20) Having now described an example embodiment of the floating wind energy harvesting apparatus according to the present invention, a maintenance method according to an embodiment of the present invention will now be described with reference to the flow-chart in FIG. 3 and the illustrations in FIGS. 4a-b and FIG. 5, and continued reference to FIG. 1 and FIG. 2 where applicable.

(21) In a first step 100, a specialized maintenance vessel docks with the VAWT 1. Referring to FIGS. 4a-b, an exemplary maintenance vessel 40 has an opening 41, a holding arrangement 42, and a crane 43 for allowing safe docking with the VAWT 1 and replacement of the energy converter 12. On the deck the vessel 40 carries replacement energy converters 45a-b.

(22) To be able to dock the vessel 40 with the VAWT 1, the rotation of the VAWT 1 is first stopped by wirelessly sending a signal to the control unit comprised in the energy converter 12 to brake the VAWT 1 by actuating the brake calipers 38a-b. Thereafter, the vertical level of the vessel 40 is controlled using tanks (not shown in FIGS. 4a-b) in the vessel 40 to align the holding arrangement 42 with the first 25 and second 26 body flanges of the VAWT 1.

(23) The holding arrangement 42 is configured to allow temporary attachment to the lower 7 and upper 10 body portions of the VAWT 1, and, although not visible in FIGS. 4a-b, additionally comprises channels for circulating hot fluid in the interior of the holding arrangement 42 to expand the holding arrangement. As is schematically indicated in FIGS. 4a-b, the vessel 40 comprises a heating arrangement 47 for heating the fluid circulating in the interior of the holding arrangement 42.

(24) Returning to the flow-chart in FIG. 3, the holding arrangement 42 is attached to the lower 7 and upper 10 wind turbine body parts in step 101. As is schematically indicated in FIG. 5, the holding arrangement 42 is connected to the first body flange 25 using bolts 48a-i and to the second body flange 26 using bolts 49a-i. The above-mentioned channels 50 are schematically indicated in FIG. 5.

(25) It may be convenient to first arrange the holding arrangement 42 between the lower 7 and upper 10 body portions with some play, and then heat the holding arrangement to bring it in contact with the first 25 and second 26 body flanges. Thereafter, the upper 48a-i and lower 49a-i sets of bolts can be tightened.

(26) In the next step 102, the energy converter 12 is released by removing the bolts 30a-c, 32a-c and nuts 31a-c, 33a-c attaching the energy converter 12 to the upper 10 and lower 7 body portions.

(27) Thereafter, in step 103, the lower 7 and upper 10 body portions are separated by operating the heating arrangement 47 to circulate more hot fluid through the channels 50 in the holding arrangement 42. After the holding arrangement has expanded, the energy converter 12 is removed in step 104 using the crane 43, and placed on the deck of the vessel 40.

(28) Subsequently, in step 105, a replacement energy converter 45a is arranged between the lower 7 and the upper 10 body portions using the crane 43.

(29) The replacement generator 45a is attached to the lower 7 and upper 10 body portions in step 106, and the holding arrangement is then disengaged in step 107 by removing the upper 48a-i and lower 49a-i sets of bolts and allowing the holding arrangement to cool down (or actively cooling the holding arrangement) and moving the vessel 40 away from the VAWT 1.

(30) The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

(31) In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.