WO2020136104A1

WO2020136104A1 - Wind turbine with helihoist and movable cooler

Info

Publication number: WO2020136104A1
Application number: PCT/EP2019/086525
Authority: WO
Inventors: Lars Laursen MØLLER
Original assignee: Mhi Vestas Offshore Wind A/S
Priority date: 2018-12-28
Filing date: 2019-12-20
Publication date: 2020-07-02
Also published as: EP3902997A1; TW202035862A

Abstract

A wind turbine (10) includes a tower (12), a nacelle (16) disposed on the tower (12) that includes a nacelle roof (34), a rotor (14) including a hub (18) and at least one wind turbine blade (20), a helihoist (32) affixed to the nacelle roof (34), and a cooler (30, 60) slidably mounted to the nacelle (16) and having an exposed wind area operable to remove heat from heat-generating components of the wind turbine (10). The cooler (30, 60) is slidably movable between a first position and a second position. In the first position, the height of the cooler (60) may be greater than a height of the helihoist (32), such as a sidewall (38) thereof. In the second position, the cooler (60) may be positioned at a height substantially equal to the sidewall (38) or at a position behind the nacelle (16).

Description

WIND TURBINE WITH HELIHOIST AND MOVABLE COOLER

Technical Field

The invention relates generally to wind turbines, and more particularly to a wind turbine having a helihoist and a cooler slidably movable relative to the helihoist.

Background

Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A horizontal-axis wind turbine includes a tower, a nacelle located at the apex of the tower, and a rotor having a plurality of blades and supported in the nacelle by means of a shaft. The shaft couples the rotor either directly or indirectly with a generator, which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator.

Components of the generator located within the nacelle generate significant heat during operation, which in turn, causes the temperature of the air in the nacelle and the generator components to increase. When the generator components are heated, the overall efficiency of power generation may be decreased. Therefore, the generator components and the nacelle may be cooled to ensure that the heat does not adversely affect power generation and/or damage the components.

Conventional wind turbines may include one or more cooling devices configured to remove the heat generated during operation of the wind turbine. The cooling devices may include standard heat sinks. Another exemplary cooling device is a cooler top positioned along one side (e.g., the roof or sides) of the nacelle and including one or more panels partially enclosed by a cover. The air flowing past the wind turbine cools a second fluid flowing through the panels, the second fluid being directed to other heat exchangers within the nacelle to remove heat from generator components and the nacelle. To this end, the cooling devices operate to thereby reduce the temperature of the nacelle and the generator components.

Wind turbines may include a helihoist platform (“helihoist”) on top of the nacelle for receiving supplies/personnel hoisted from a hovering helicopter to the helihoist. The helihoist includes a platform and a railing surrounding the platform. As the helihoist is configured to support service technicians, the placement of the helihoist in relation to the nacelle is typically subject to numerous safety regulations in certain countries. For example, the railing of the helihoist may have to conform to a minimum height safety standard. In conventional wind turbines, the helihoist is generally positioned at a rear end of the nacelle roof (e.g., opposite to the rotor). In some installations, the cooler is mounted to the most rearward side of the helihoist (e.g., farthest from the rotor). To realize a good cooling effect, the cooler should be exposed to free flow of wind, but this also exposes the cooler to high winds during storms, such as hurricanes and typhoons, and hence high structural loads. By exposing the cooler to high winds, the cooler may be damaged, leading to higher repair and maintenance costs.

As the power production per wind turbine increases, so does the required cooling capacity. Higher cooling capacity near the nacelle may be realized by adding coolers on the side of the nacelle, however, such coolers remains complicated to service as they are not readily accessible. In installations where the cooler is mounted to the most rearward side of the helihoist, the cooling requirements of the wind turbine may require the exposed wind area of the cooler be larger than the rearward side of the helihoist. In such installations, the height of the cooler may be greater than the height of the helihoist including the railing. This could potentially be a problem during operations of the helihoist.

Thus, there remains a need for providing a higher cooling capacity while also retaining an operable and accessible helihoist.

Summary

A wind turbine includes a tower, a nacelle disposed on the tower and having a nacelle roof, a rotor including a hub and at least one wind turbine blade, the rotor operatively coupled to a generator, a helihoist affixed to the nacelle roof, the helihoist includes a platform with a working surface, and a cooler slidably mounted to the nacelle and having an exposed wind area operable to remove heat from heat generating components of the wind turbine. The cooler is slidably movable between a first position and a second position. In one embodiment, the cooler has a first height relative to the platform in the first position and has a second height relative to the platform in the second position, wherein the first height is greater than the second height. The first position may be an operable position such that the exposed wind area of the cooler is maximized. In an exemplary embodiment, the helihoist has a height and the first height of the cooler is greater than the height of the helihoist. The helihoist may further include a sidewall surrounding at least a portion of the platform, wherein the first height of the cooler is greater than the height of the sidewall.

In one embodiment, the second position may be a stowed position such that the exposed wind area of the cooler is minimized. The cooler may be positioned vertically at least partially behind the nacelle in the second position, and preferably the cooler is positioned vertically completely behind the nacelle in the vertical direction.

In one embodiment, the second position may be a position such that the second height of the cooler is substantially equal to the height of the sidewall. Accordingly, the helihoist may satisfy applicable regulations. In these embodiments, the cooler may form part of the sidewall when in at least one of the first and second positions.

A method of operating a wind turbine includes providing the wind turbine with a tower, a nacelle disposed on the tower and including a nacelle roof, a rotor including a hub and at least one wind turbine blade, the rotor operatively coupled to a generator, a helihoist affixed to the nacelle roof, the helihoist having a platform with a working surface, and a cooler mounted to the nacelle and having an exposed wind area operable to remove heat from heat-generating components of the wind turbine; and slidably moving the cooler relative to the nacelle from a first position to a second position, wherein the exposed wind area is smaller in the second position than in the first position.

In one embodiment, the cooler has a first height relative to the platform in the first position and a second height relative to the platform in the second position, wherein second height is less than the first height. In an exemplary embodiment, the helihoist has a height and the first height of the cooler is greater than the height of the helihoist. In one embodiment, the helihoist may further include a sidewall surrounding at least a portion of the platform, wherein the first height of the cooler is greater than the height of the sidewall.

In one embodiment, slidably moving the cooler further includes slidably moving the cooler vertically at least partially behind the nacelle when in the second position, preferably the cooler is positioned vertically completely behind the nacelle in the vertical direction.

In one embodiment, slidably moving the cooler further includes slidably moving the cooler vertically such that the second height of the cooler is substantially equal to the height of the sidewall. In this configuration the helihoist is operable for helihoist operations without the cooler extending above the safety barrier in the form of the sidewall.

The term“helihoist operation” in the context of the present application shall be taken to include landing and take-off of an airborne vehicle or transferal of personnel and/or equipment from a hovering airborne vehicle.

Examples of airborne vehicles include unmanned aerial vehicles, such as drones and vertical take-off and landing vehicles, such as helicopters.

In one embodiment, a helihoist operation is performed with the cooler in its second position.

In embodiments of the helihoist without a sidewall, the second position of the cooler includes a position where a top surface of the cooler is level with or vertically lower than a top surface of the platform.

In embodiments of the helihoist with a sidewall, the second position of the cooler includes a position where the top surface of the cooler is level with or vertically lower than the top surface of the sidewall. In another embodiment, which is combinable with all other embodiments of the helihoist, the wind turbine according to the invention comprises a biasing means for biasing the cooler towards the second position.

In case of a failure of the primary system for moving and holding the cooler in the first position the cooler will automatically move to the second position. The second position is a position where the cooler is substantially behind the rear side of the nacelle and hence less exposed to extreme winds for example during a typhoon. Hence, the cooler will move behind the nacelle and reduce the impact of wind on the wind turbine generator during an extreme wind situation even if the primary system for moving the cooler should fail. This is highly advantageous as this redundant system for reducing the wind impact on the cooler allows for designing the wind turbine generator towards only the lower wind impact when the cooler is in the second position.

Moreover, the second position allows a helicopter to approach the turbine such that maintenance personnel can be hoisted down to or up from the helihoist to enable repair of the failed system.

In an embodiment, the biasing means is a spring mechanism.

In another embodiment the biasing means works under the assistance of gravity. As an example, the cooler is moved up and down relative to the helihoist via a lift system. The exemplary lift system may comprise a gear and pinion, an electric actuator, a hydraulic actuator or a chain and gear. The biasing means is integrated with the lift system.

On a lift system comprising a gear and pinion, the threads have an angle such that when the source of motive power for the gear is off the cooler will move towards the second position under the influence of gravity. This would also apply to a system with an electric actuator. For a lift system comprising a hydraulic actuator, the oil may be allowed to flow back to a tank if the hydraulic pressure is off and thus allow the cooler to move to the second position under the force of gravity.

In relation to a chain and gear-based lift system the gear should allow the cooler to move towards the second position when unpowered.

Embodiments of the lift system may include springs to force the cooler towards the second position if the force of gravity is insufficient to move the cooler and dampers to ensure that the acceleration of the cooler during a sudden loss of power in the lift system is small enough to prevent the cooler form moving to fast and thereby get damaged, when the second position is reached.

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

Fig. 1 is a perspective view of a wind turbine;

Fig. 2A is a partial perspective view of the nacelle of the wind turbine of Fig. 1 , including a cooler and a helihoist arrangement according to a first embodiment with the cooler in an operable position;

Fig. 2B is a partial perspective view of the cooler and helihoist arrangement of Fig. 2A with the cooler in a stowed position;

Fig. 3A is a partial perspective view of the nacelle of the wind turbine of Fig. 1 , including a cooler and a helihoist arrangement according to a second embodiment with the cooler in an operable position; Fig. 3B is a partial side view of the cooler and helihoist arrangement of Fig. 3A with the cooler in an operable position;

Fig. 3C is a partial side view of the cooler and helihoist arrangement of Fig. 3A with the cooler in an intermediate position; and

Fig. 3D is a partial side view of the cooler and helihoist arrangement of Fig. 3A with the cooler in the stowed position;

Detailed Description

With reference to Fig. 1 , a wind turbine 10 includes a tower 12, a nacelle 16 disposed at the apex of the tower 12, and a rotor 14 operatively coupled to a generator 26 housed inside the nacelle 16. In addition to the generator 26, the nacelle 16 houses miscellaneous components required for converting wind energy into electrical energy and various components needed to operate, control, and optimize the performance of the wind turbine 10. The tower 12 supports the load presented by the nacelle 16, the rotor 14, and other components of the wind turbine 10 that are housed inside the nacelle 16, and also operates to elevate the nacelle 16 and rotor 14 to a height above ground level or sea level, as may be the case, at which faster moving air currents of lower turbulence are typically found.

The rotor 14 of the wind turbine 10, which is represented as a horizontal-axis wind turbine, serves as the prime mover for the electromechanical system. Wind exceeding a minimum level will activate the rotor 14 and cause rotation in a substantially perpendicular direction to the wind direction. The rotor 14 of wind turbine 10 includes a central hub 18 and at least one blade 20 that projects outwardly from the central hub 18. In the representative embodiment, the rotor 14 includes three blades 20 circumferentially distributed about the central hub 18, but the number may vary. The wind turbine blades 20 are configured to interact with the passing air flow to produce lift that causes the rotor 14 to spin generally within a plane defined by the blades 20. The tower 12 includes a base 24 fixed to a support surface 22 which may, for example, be the ground or any other suitable support surface including a platform at sea. In order to provide cooling for the generator 26 and other heat-generating components associated with the wind turbine 10, the wind turbine 10 according to a first embodiment includes a cooler 30 as shown in Fig. 2A. The wind turbine 10 also includes a helihoist 32 for receiving, for example, turbine components and/or service technicians hoisted from a hovering helicopter or a landing airborne vehicle. The nacelle 16 has a nacelle roof 34 to which the helihoist 32 is attached. The helihoist 32 has a platform 36 fully surrounded by a protective barrier such as sidewalls 38 fixed to the platform 36. The sidewalls 38 may be tall enough to allow service technicians to work on the platform 36 without having to be tethered to either the platform 36 or the sidewalls 38. In one embodiment, the cooler 30 may extend across the entire width of the rear edge of the platform 36 and may be essentially the same height as the sidewalls 38 which may be arranged in front of the cooler 30.. Other protective barrier arrangements may also be employed besides the sidewalls 38 illustrated in Figs. 2A and 2B so long as those protective barrier arrangements prevent a service technician from falling off the platform when they are not tethered.

Examples of airborne vehicles that can land on the helihoist platform 36 can be an unmanned aerial vehicle (UAV) or a so-called drone or a helicopter, wherein in at least in the latter case the helihoist platform 36 should have no barrier.

The cooler 30 is shown in Fig. 2A in a first or normal operable position. That is, the cooler 30 is positioned in its most upward position relative to the helihoist 32 so that the cooler 30 may receive optimal airflow to cool the generator 26 and other components housed within the nacelle 16. In the normal operable position, a front face 42 of the cooler 30 has a maximum exposed wind area, i.e. , the largest surface area exposed to the wind. In accordance with one aspect of the invention, when the wind turbine 10 is exposed to excessive high winds, such as during a storm, hurricane, or typhoon, the cooler 30 may be moved downward relative to the helihoist 32 so that the cooler 30 is substantially behind the rear side of the nacelle 16 as shown in Fig. 2B. The term“behind” means that the front face 42 of the cooler 30 confronts the rear wall of the nacelle 16 such that at least part of the cooler 30 is not subjected to the on coming wind. In Fig. 2B, the cooler 30 is in a second position. In this embodiment the second position is a stowed position with the cooler 30 in its lowermost vertical position, where it is level or below the surface of the platform 36. In the stowed position, the front face 42 of the cooler 30 has a minimum exposed wind area, i.e. , the least surface area exposed to the wind. To facilitate moving the cooler 30 downward, the cooler 30 may include sliding guides 40 affixed to the front face 42 of the cooler 30. The sliding guides 40 engage complimentary stationary guide members 44 affixed to the rear edge of the platform 36. In one embodiment, the sliding guide 40 and the stationary guide members 44 may be configured such that the cooler slides vertically between the operable and stowed positions. The cooler 30 is moved up and down relative to the helihoist 32 via a lift system 46, such as a gear and pinion, electric or hydraulic actuator, chain and gear, or other actuation system. It should be appreciated that other mechanical arrangements can be used to move the cooler 30 up and down relative to the helihoist 32 besides the sliding guides 40 and stationary guide members 44 shown in Figs. 2A and 2B.

In another aspect according to the invention, the cooler 30 may also be moved to a second which is an intermediate position (not shown) between the normal operable position (Fig. 2A) and the stowed position (Fig. 2B). In this intermediate position, the cooler 30 has an intermediate exposed wind area that is less than the maximum exposed wind area and greater than the minimum exposed wind area. In this way, the wind force may be reduced, but some level of cooling may still be provided. In other words, the cooler 30 may remain operable in the intermediate position, but perhaps at a diminished capacity compared to being in the normal operable position.

In another aspect according to the invention, the nacelle 16 may include an anemometer, i.e., a wind sensor 48 (e.g., cup, hot wire, pressure tube, ultrasonic, laser doppler, etc.) that monitors the speed of the wind at or approaching the nacelle 16. The wind sensor 48 may be operably coupled to a controller 50 that may be configured to move the cooler 30 from the normal, operable position to the stowed position when the wind reaches a predetermined critical wind speed. For example, the wind turbine may reduce production at wind speeds above a first threshold, e.g. 25 m/s and completely shut down its production when the wind speed increases above a second threshold, e.g. 30 m/s and thus the controller 50 may be configured to lower the cooler 30 to the intermediate position and continue operation at reduced capacity between the first and second thresholds and to the stowed position to protect the cooler 30 at higher wind speeds. The controller 50 may be configured to move the cooler 30 back to the normal operable position after the winds drop below the above threshold for a predefined period of time, for example, at least a period of 30 minutes. The wind turbine 10 may also include a manual control that a service technician could use to move the cooler 30 between the operable, intermediate, and stowed positions.

While the sidewalls 38 fully surround the platform 36 in Figs. 2A and 2B, it will be appreciated that the rearward side of the sidewall 38 may be eliminated and the cooler 30 in its operable position may serve as a protective barrier across the rear edge of the platform 36. In this arrangement, the cooler 30 may extend across the entire width of the rear edge of the platform 36 and may be essentially the same height as the sidewalls 38 of the helihoist 32.

As the power production per wind turbine increases, so does the required cooling capacity. In order to provide cooling for the generator 26 and other heat-generating components associated with the wind turbine 10, the wind turbine 10 according to a second embodiment includes a cooler 60 that is of a similar configuration and function as cooler 30 but has a height greater than the height of the helihoist sidewalls 38, as shown in Figs. 3A-3D. This larger cooler 60 is intended to provide greater cooling capacity than the smaller cooler 30. Reference numbers from the first embodiment (Figs. 2A-2B) are used on similar structures in the second embodiment. The second embodiment includes the helihoist 32 with sidewalls 38 and the platform 36 of the helihoist 32. As shown in Fig. 3A, the cooler 60 extends across the entire width of the rear edge of the platform 36. It should be appreciated, however, that in another embodiment, the width of the cooler 60 may be wider than the entire width of the rear edge of the platform 36 such that the sides of the cooler 60 extend beyond the width of the platform 36 and sidewalls 32. Similar to the first embodiment, the cooler 60 may move between a first or normal operable position (Figs. 3A and 3B) and a second or stowed position (Fig. 3D). In the normal operable position, a front face 64 of the cooler 60 has a maximum exposed wind area, i.e. , the largest surface area exposed to the wind. In the stowed position, the front face 64 of the cooler 60 has a minimum exposed wind area, i.e., the least surface area exposed to the wind. To facilitate vertical movement, the cooler 60 may include sliding guides 62 affixed to the front face 64 of the cooler 60. The sliding guides 62 engage complimentary stationary guide members 66 affixed to the rear edge of the platform 36. The sliding guides 62 and stationary guide members 66 may be configured such that the cooler 60 slides vertically between the operable and stowed positions. The cooler 60 is moved up and down relative to the helihoist 32 via a lift system 46, such as a gear and pinion, electric or hydraulic actuator, chain and gear, or other actuation system. It should be appreciated that other mechanical arrangements can be used to move the cooler 60 up and down relative to the helihoist 32 besides the sliding guides 62 and stationary guide members 66 shown in Fig. 3A.

By locating the cooler 60 in the operable position, as shown in Figs. 3A and 3B, the cooler 60 may be the highest point of the wind turbine 10, excluding the blades 20. In countries with safety standards requiring the helihoist 32 (e.g., including the sidewalls 38) be the highest point of the wind turbine 10, excluding the blades 20, the operable position of the cooler 60 may render the helihoist 32 outside applicable regulations. Additionally, the height of the cooler 60 may interfere with receiving supplies/personnel hoisted from a hovering helicopter to the helihoist 32. In another aspect according to the invention, the cooler 60 may be moved to a second position which is an intermediate position somewhere between the normal operable position (Figs. 3A and 3B) and the stowed position (Fig. 3D). As shown in Fig. 3C, for example, the cooler 60 may be lowered to an intermediate position such that the highest point of the cooler 60 is substantially equal to the highest point of the helihoist 32, which in Fig. 3C is the sidewalls 38. In this way, the cooler 60 is no higher than the sidewalls 38 of the helihoist 32 to comply with applicable regulations and also provides an operable and accessible helihoist 32.

The term intermediate position means the intermediate position as shown in Fig. 3C or any other position between the normal operable position (Figs. 3A and 3B) and the stowed position (Fig. 3D). In the intermediate position, the cooler 60 has an intermediate exposed wind area that is less than the maximum exposed wind area and greater than the minimum exposed wind area. Furthermore, the wind force may be reduced, but some level of cooling may still be provided. In other words, the cooler 60 may remain operable in the intermediate position, but perhaps at a diminished capacity compared to being in the normal operable position. In another aspect of the second embodiment, the nacelle 16 may include a wind sensor 48 for monitoring the speed of the wind at or approaching the nacelle 16. The wind sensor 48 may be operably coupled to the controller 50 that may be configured to slidably move the cooler 60 from the normal, operable position to the stowed position when the wind reaches a predetermined critical wind speed. For example, the wind turbine 10 may reduce production at wind speeds above a first threshold, e.g. 25 m/s and completely shut down its production when the wind speed increases above a second threshold, e.g. 30 m/s and thus the controller 50 may be configured to slidably move the cooler 60 to the intermediate position and continue operation at a reduced capacity between the first and second thresholds and to the stowed position to protect the cooler 60 at higher wind speeds. The controller 50 may be configured to move the cooler 60 back to the normal operable position after the winds drop below the above threshold for a predefined period of time, for example, at least a period of 30 minutes. The wind turbine 10 may also include a manual control that a service technician could use to move the cooler 60 between the operable, intermediate, and stowed positions.

While the sidewalls 38 fully surround the platform 36 in Figs. 3A, it will be appreciated that the rearward side wall 38 may be eliminated and the cooler 60 in its operable position may serve as a protective barrier across the rear edge of the platform 36. The cooler 60 may also serve as a protective barrier in an intermediate position so long as the top of the cooler 60 is at least as high as the top of the sidewalls 38.

It should further be appreciated that in alternative embodiments the platform 36 may have no sidewalls 32 surrounding it like the embodiments shown in Figs. 2A, 2B, and 3A. In this case, the helihoist operates as a helipad wherein a UAV, drone, helicopter or other air vehicles may land. Without any sidewalls 32, a UAV, a drone, or a helicopter may land on the platform 36. Without the sidewalls 32, however, service technicians would need to be tethered to platform 36, for example, in order to work out on the platform 36. In this embodiment, aspects of the invention may be used to position the cooler at a height substantially equal to the platform such that the platform forms the highest aspect (excluding the blades). For example, in this position, the cooler may be in or near the stowed position. A helihoist operation may be performed with the cooler 60 in the positions shown in fig. 3C or 3D.

While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.

Claims

1. A wind turbine (10), comprising:

a tower (12);

a nacelle (16) disposed on the tower (12) and including a nacelle roof (34); a rotor (14) including a hub (18) and at least one wind turbine blade (20), the rotor (14) operatively coupled to a generator (26); and

a helihoist (32) affixed to the nacelle roof (34), the helihoist (32) having a platform (36) with a working surface; and

a cooler (30, 60) slidably mounted to the nacelle (16) and having an exposed wind area operable to remove heat from heat-generating components of the wind turbine (10), wherein the cooler (30, 60) is slidably movable between a first position and a second position.

2. The wind turbine (10) of claim 1 , wherein the cooler (30, 60) has a first height relative to the platform in the first position and has a second height relative to the platform in the second position, and wherein the first height is greater than the second height.

3. The wind turbine (10) of claim 1 or 2, wherein the first position is an operable position such that the exposed wind area of the cooler (30, 60) is maximized.

4. The wind turbine (10) of claim 2 or 3, wherein the helihoist (32) has a height, and wherein the first height of the cooler (60) is greater than the height of the helihoist (32).

5. The wind turbine (10) of claim 4, wherein the helihoist (32) further comprises a sidewall (38) surrounding at least a portion of the platform (36), and wherein the first height is greater than the height of the cooler (60) of the sidewall (38).

6. The wind turbine (10) of any of the preceding claims, wherein the second position is a stowed position such that the exposed wind area of the cooler (30, 60) is minimized.

7. The wind turbine (10) of claim 6, wherein the cooler (30, 60) is positioned vertically at least partially behind the nacelle (16) in the second position, preferably the cooler (30, 60) is positioned vertically completely behind the nacelle (16) in the vertical direction.

8. The wind turbine (10) of claims 5, wherein the second position is a position such that the second height of the cooler (60) is substantially equal to the height of the sidewall (38).

9. The wind turbine (10) of claim 5, wherein the cooler (30, 60) forms part of the sidewall (38) when in at least one of the first and second positions.

10. A method of operating a wind turbine (10), comprising:

providing the wind turbine (10) with a tower (12), a nacelle (16) disposed on the tower (12) and including a nacelle roof (34), a rotor (14) including a hub (18) and at least one wind turbine blade (20), the rotor (14) operatively coupled to a generator (26), a helihoist (32) affixed to the nacelle roof (34), the helihoist (32) having a platform (36) with a working surface, and a cooler (30, 60) mounted to the nacelle (16) and having an exposed wind area operable to remove heat from heat-generating components of the wind turbine (10); and

slidably moving the cooler (30) relative to the nacelle (16) from a first position to a second position, wherein the exposed wind area is smaller in the second position than in the first position.

1 1 . The method of operating a wind turbine (10) of claim 10, wherein the cooler (30, 60) has a first height relative to the platform (36) in the first position and a second height relative to the platform (36) in the second position, and wherein second height is less than the first height.

12. The method of operating a wind turbine (10) of claim 1 1 , wherein the helihoist (32) has a height, and wherein the first height of the cooler (60) is greater than the height of the helihoist (32).

13. The method of operating a wind turbine (10) of claim 12, wherein the helihoist (32) further comprises a sidewall (38) surrounding at least a portion of the platform (36), and wherein the first height of the cooler (60) is greater than the height of the sidewall (38).

14. The method of operating a wind turbine (10) of any of claim 10-13, wherein slidably moving the cooler (30) further comprises slidably moving the cooler (30, 60) vertically at least partially behind the nacelle when in the second position, preferably the cooler (30) is positioned vertically completely behind the nacelle (16) in the vertical direction.

15. The method of operating a wind turbine (10) of claim 13, wherein slidably moving the cooler (60) further comprises slidably moving the cooler (60) vertically such that the second height of the cooler (60) is substantially equal to the height of the sidewall (38).

16. The method of operating a wind turbine (10) of any of claim 10-15, wherein a helihoist operation is performed with the cooler (60) in its second position.