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Title:
LIGHT EMITTING UNIT, AND METHOD FOR INSTALLING THEREFOR
Document Type and Number:
WIPO Patent Application WO/2017/146576
Kind Code:
A1
Abstract:
Method for installing a light emitting unit on a wall part of a wind turbine tower having a through-hole therein comprising: providing a light emitting unit, wherein the light emitting unit comprises at least an optic element; - inserting the light emitting unit in the through-hole of the wind turbine wall from an outside of the wind turbine wall part to an inside of the wind turbine wall part such that the optic element remains at least partially at the outside of the wind turbine wall to provide, in use, a light emitting pattern.

Inventors:
DE BRUIJN, Johannes Arie (3125 AT Schiedam, 3125 AT, NL)
ROSKAM, Roelf Albert (3125 AT Schiedam, 3125 AT, NL)
GOEDKNEGT, Pieter Gerardus (3125 AT Schiedam, 3125 AT, NL)
VAN DER HEIDEN, Robertus Everardus Antonius (3125 AT Schiedam, 3125 AT, NL)
Application Number:
NL2017/050113
Publication Date:
August 31, 2017
Filing Date:
February 24, 2017
Export Citation:
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Assignee:
ORGA HOLDING B.V. (Strickledeweg 13, 3125 AT Schiedam, 3125 AT, NL)
International Classes:
F03D80/10; F21S8/02; F21V21/04; F21W111/00
Foreign References:
JP2002279802A2002-09-27
DE202012003935U12013-07-22
US20080192460A12008-08-14
US7494244B12009-02-24
US20110194283A12011-08-11
Other References:
None
Attorney, Agent or Firm:
JANSEN, C.M. (V.O, Carnegieplein 5, 2517 KJ Den Haag, 2517 KJ, NL)
Download PDF:
Claims:
Claims

1. Method for installing a light emitting unit on a wall part of a wind turbine tower having a through-hole therein comprising:

- providing a light emitting unit, wherein the light emitting unit comprises at least an optic element;

- inserting the light emitting unit in the through-hole of the wind turbine wall from an outside of the wind turbine wall part to an inside of the wind turbine wall part such that the optic element remains at least partially at the outside of the wind turbine wall to provide, in use, a light emitting pattern.

2. Method according to claim 1, further comprising, connecting, from the inside of the wind turbine wall part, the light emitting unit to a control unit.

3. Method according to claim 1 or 2, wherein the light emitting unit further comprises a sleeve element, that is connected to the optic element, and inserted in the through-hole from the outside to the inside together with the optic element, such that the sleeve element fits in the through-hole.

4. Method according to claim 3, wherein the sleeve element is provided with a stop element at an outer end thereof, wherein the stop element, after inserting the sleeve element in the through-hole, abuts against an outer side of the wall part of the wind turbine tower.

5. Method according to claim 3 or 4, wherein at an inner end of the sleeve element, mounting elements are provided to mount the light emitting unit to the wind turbine wall part.

6. Method according to any of the preceding claims, wherein the light emitting unit further comprises a light emitting element that is arranged at an entrance side of the optic element.

7. Method according to any of the preceding claims, further comprising, for maintenance, removing a part of the light emitting unit from an inside of the wind turbine wall part, while at least the sleeve element remains in the through-hole.

8. Light emitting unit comprising an optic element and a sleeve element, connected to the optic element, wherein the sleeve element is configured to be inserted in a through-hole in a wall part of a wind turbine tower, such that it can be inserted in the through-hole from the outside to the inside only and the optic element is, after installation, positioned at least partially outside of the wind turbine wall part to provide a light emitting pattern.

9. Light emitting unit according to claim 8, wherein the sleeve element is provided with a stop element at an outer end of the sleeve element, wherein the stop element, after insertion of the sleeve element in the through-hole, abuts against an outer side of the wall part of the wind turbine tower.

10. Light emitting unit according to claim 8 or 9, further comprising a light emitting element arranged at an entrance side of the optic element.

11. Light emitting unit according to any of the claims 8 - 10, further comprising an electrical and/or data connection element at an inner side of the light emitting unit to connect to an electrical circuit and/or a control unit.

12. Light emitting unit according to any of the claims 9 - 11, wherein the stop element is provided with a seahng member to seahngly engage with an outer wall side of the wind turbine wall part.

13. Assembly of a wind turbine wall part and at least one light emitting unit according to any of the claims 8 - 12.

14. Wind turbine tower provided with at least one light emitting unit according to any of the claims 8 - 12.

Description:
Title: Light emitting unit, and method for installing therefor

The invention relates to a light emitting unit, in particular an aircraft obstruction light emitting unit and a method for installing.

Aircraft obstruction light emitting units are well known and are typically provided on structures, onshore or offshore, of a certain height. Often, regulatory requirements determine for example how many and at what height obstruction lights need to be provided on a certain structure. Also for wind turbine tower, there are requirements as to how many and at what height of the wind turbine tower obstruction lights need to be provided. Also, the regulatory requirements may prescribe the light emitting pattern of such an obstruction light. As such, there is now a need to provide wind turbine tower of a height above a minimum height, with aircraft obstruction lights at an outside of the tower. The aircraft

obstruction lights are then mounted at predefined heights and/or at predefined circumferential positions on the wall of the wind turbine tower. Preferably, the multiple obstruction lights emit a hght pattern that provides for 360 degrees circumferential visibility of the wind turbine tower.

Multiple solutions are suggested to mount the obstruction lights to wind turbine tower wall. There is the possibility to mount the obstruction lights at the outer side of the wind turbine wall. However, then also the cabling and/or electrical connections are provided at the outer side of the wind turbine tower, making them vulnerable for environmental influences. Additionally, servicing, maintenance and/or repair of these lights at the outer side of the wind turbine wall is to be done from outside, using relatively expensive means such as a crane or by means of a person abseiling from the tower. To overcome this drawback, holes were provided in the wind turbine tower, and a cylindrical rod-shaped light was inserted into the hole from the inner side of the tower to the outer side. A drawback of this solution however, is that it may be difficult to align the hght such that it emits the desired light pattern. Furthermore, it may be difficult to provide for water-tightness of the connection between the rod-shaped light and the wind turbine tower to prevent water and/or dirt from entering the wind turbine tower. Furthermore, it may be difficult to determine how far the rod-shaped light needs to be inserted through the hole to provide for the desired light pattern.

Therefore, there is a need for an improved obstacle light and installation therefor that obviates at least one of the above mentioned drawbacks while, preferably, maintaining the advantages.

Thereto, the invention provides for a light emitting unit comprising an optic element and a sleeve element, connected to the optic element, wherein the sleeve element is configured to be inserted in a through-hole in a wall part of a wind turbine tower, such that it can be inserted in the through-hole from the outside to the inside only and the optic element is, after installation, positioned at least partially outside of the wind turbine wall part to provide a light emitting pattern.

By providing a light emitting unit of which a sleeve element is configured to be inserted into the hole from the outside to the inside only, a more reliable and more weather-proof way of installing the light emitting unit into the hole of the wind turbine wall part. It may be more easy to align the light emitting unit such that a desired light pattern is emitted.

Typically, the desired light pattern may have a relatively wide horizontal spread and a relatively small vertical spread. The light emitting pattern may be prescribed by regulatory requirements, such as national regulations or international regulations e.g. ICAO-regulations. As such, the light emitting pattern is not further described in this specification. The light emitting unit is thus an aircraft obstruction light that may need to comply with regulatory requirements.

The sleeve element is connected to the optic element. The optic element can be a lens or a reflector or a lens making use of total internal reflection, etc.. Many variants of the optic element are possible and are all suitable as long as they provide for the required light emitting pattern.

The sleeve element can be a tubular element that fits in the hole of the wall part. The sleeve element can be made of various materials, e.g. it can be a plastic part or a metallic, such as aluminum or stainless steel, part. In an embodiment, an outer wall of the tubular element may be provided with elastic material, such as rubber. This elastic material can be

compressed when the sleeve element is inserted into the hole and, once installed, may expand so much as to tightly fit to the inner wall of the hole. As such, a barrier against environmental influences, such as water and/or dirt, can be formed. Also, the elastic material may provide for a fixation of the sleeve inside of the hole.

The sleeve element has an inner end which extends, after installation, to an inside of the wind turbine tower wall part, and an outer end which extends, after installation, to an outside of the wind turbine tower wall part. In a preferred embodiment, the sleeve element is provided with a stop element at its outer end. As such, the sleeve element is configured to be insertable in the hole of the wind tower wall part from the outside to the inside only. Also, by providing such a stop element, the sleeve element can be inserted into the hole of the wall part until the stop element abuts against the outside of the wall part. Thus, the distance over which the sleeve element can be inserted in the wall part is determined, and the optic element, which needs to be at least partially outside of the wall part in order to provide a light emitting pattern, can have a predetermined position. This may make the installation of multiple light emitting units more

reproducible and more reliable. In a further embodiment, the stop element may be provided with a sealing element that, after installation, sits between the stop element and the outside of the wind turbine wall part, thus providing for a barrier against environmental influences, such as water and/or dirt. The stop element can be embodied as a flange, or as at least two outwardly extending fingers. The sealing element may be integrated to the stop element, e.g as a rubber flange or a coating onto the flange.

In another embodiment, the stop element may be provided as a skirt provided on the sleeve element near an outer end of the sleeve element. The skirt may comprise multiple skirt elements that flare outwardly from the sleeve element. Preferably, the skirt elements flare outwardly directed towards the outer end of the sleeve element. Preferably, the skirt elements are biased towards the outwardly flaring position, e.g. by means of a spring, or because the skirt elements are made from plastic material and are hingedly connected to the sleeve element and as such are biased towards the outwardly flaring position. When inserting the sleeve element into the hole of the wind turbine tower wall part, the skirt elements are pushed towards the sleeve element against their bias until a firm fixation of the sleeve element in the hole is obtained. By amending the biasing of the skirt, the distance over which the sleeve element can be inserted in the hole may be varied to a predetermined distance.

The sleeve element and the optic element are connected to each other, such that, when the sleeve element is inserted into the hole over a predetermined distance, the optic element is at a predetermined position at least partially outside of the wind turbine wall part. Preferably, the optic element is connected to the sleeve element at an outer end of the sleeve element. The optic element is typically being made from glass or a

translucent plastic material. The optic element may be connected to the sleeve element by means of gluing or another adhesive connection, or by means of a mechanical connection such as screwing, or bolting, or snap- connection, etc. One may also consider of co- extruding the optic element with the sleeve element. Preferably, the optic element and the sleeve element are firmly connected to each other such that they are inserted together at once in the hole of the wind turbine wall part from the outside to the inside. When installing the wind turbine tower, usually the wall parts are mounted and lifted one by one or in segments on the tower to built the complete wind turbine tower. When the wall parts are still on the ground or on site, the holes can be made in the wall parts and the light emitting unit can be inserted in the hole, from the outside to the inside. This can be done on site, or may even be done in a controlled environment, e.g. on a

manufacturing site or in a fabrication hall. Once the light emitting unit is inserted in the hole, it only needs to be connected to an electrical and/or control unit at the inside of the wind turbine wall part. This can be done for example when the wind turbine tower is erected and the inside thereof is closed from environmental influences.

In an embodiment, an inner side of the sleeve element may be provided with a mounting element to mount the light emitting unit to the wind turbine wall part. Such a mounting element may for example be a screw thread and a nut fitting onto the thread. By fastening the nut onto the thread, the sleeve element, and thus the light emitting unit, can be firmly mounted to the wall part, preferably when being held at the outer end by a stop element. Alternative embodiments for the mounting element may be a bayonet-connection, or a pen-hole-connection, or a clickfinger connection etc. Many variants are possible to lock the light emitting unit to the wall part.

In another embodiment, the light emitting unit may comprise a light emitting element. The light emitting element may emit visible light and/or infrared light. The light emitting element may be an LED-light emitting element or may be a fiber optic cable that transports light from a light source to the optic element of the light emitting unit. Preferably, the light emitting element is positioned near an entrance side of the optic element as to optimally use the optic element. The light emitting element may thus be positioned inside of the sleeve element. The light emitting element may be positioned on an inner element that is receivable inside of the sleeve element. The inner element may further be provided with a printed circuit board and/or other electronic components to control the light emitting element. In an embodiment, the inner element may also be provided with a power source. The inner element may be fixedly connected to the sleeve element when inserting the sleeve element from the outside to the inside in the hole. For example, the inner element may be connected to the sleeve element for example via a bus-connection or via an adhesive connection or a press-fitting connection etc. Advantageously, for

maintenance purposes, e.g. when the light emitting element and/or some electronic components may be repaired, the inner element may be removed from the light emitting unit, from the inside of the wind turbine tower, while at least the sleeve element remains firmly connected to the wind turbine wall part. Preferably, the optic element remains connected to the sleeve element as well. However, in an alternative embodiment, the optic element may be removable from the sleeve element, for example to exchange and/or repair the optic element. However, the connection between the optic element and the sleeve element is preferably of such a nature that the elements are inserted at once together from the outside to the inside into the hole of the wind tower wall part. When removing the optic element from the sleeve element, the connection may be broken and a new connection may have to be established between the optic element and the sleeve element. Similar, the inner element, when provided, is preferably connected to the sleeve element in a firm way, such that, when removing the inner element the connection with the sleeve element may be broken. When inserting another inner element, a new connection may have to be established. This is in particular the case when an adhesive connection may be used. When using a glass fiber cable, this cable may be inserted from the inside of the wind turbine tower after installation of the light emitting unit with the sleeve element and the optic element.

The inner element may be provided with electrical and/or other connecting elements, e.g. data connecting element, for connecting the inner element to a power source and/or a control unit. Typically, such connecting element may be provided as a socket in which a plug of a cable connecting to a power source and/or a control unit can be inserted to establish the connection. Many variants are possible and known for this type of

connection. Advantageously, the connecting element is provided at an inner end of the light emitting unit, such that it is facing towards the inside of the wind turbine tower and is relatively easily accessible after installation of the light emitting unit.

The invention further relates to a method for installing a light emitting unit on a wall part of a wind turbine tower having a through -hole therein comprising: providing a light emitting unit, wherein the light emitting unit comprises at least an optic element; inserting the light emitting unit in the through -hole of the wind turbine wall from an outside of the wind turbine wall part to an inside of the wind turbine wall part such that the optic element remains at least partially at the outside of the wind turbine wall to provide, in use, a light emitting pattern.

By inserting the sleeve element with the optic element from the outside to the inside of the wind turbine wall part, alignment of the optic element to provide the determined light emitting pattern may be more easy and/or providing a weather-proof connection between the light emitting unit and the wind tower wall part may be more easy. When inserting the light emitting unit from the outside to the inside, it may become easier to align the optic element to provide for the desired light pattern, as one may have a visual confirmation of the light pattern when being at the outside. This is advantageous with respect to a prior art rod light that is installed from the inside of the tower to the outside, as, when being inside, it is very difficult to check the alignment of the light.

The invention further relates to an assembly of a wind turbine wall part with a light emitting unit, as well as to a wind tower provided with multiple light emitting units inserted in through-holes in the wind turbine tower wall.

Further advantageous embodiments are represented in the subclaims.

The invention will further be elucidated on the basis of exemplary embodiments which are represented in a drawing. The exemplary

embodiments are given by way of non-limitative illustration. It is noted that the figures are only schematic representations of embodiments of the invention that are given by way of non -limiting example.

In the drawing:

Fig. 1 shows an embodiment of a wind turbine tower provided with light emitting units according to the invention;

Fig. 2 shows an embodiment of a light emitting unit when being inserted from the outside to the inside of the wind turbine wall part;

Fig. 3 shows another embodiment of a light emitting unit when inserted in a hole of the wind turbine wall part;

Fig. 4 shows another embodiment of a light emitting unit when inserted in a hole of the wind turbine wall part;

Fig. 5 shows another embodiment of a light emitting unit when inserted in a hole of the wind turbine wall part;

Fig. 6 shows the installation of the light emitting unit from the outside to the inside of the wind turbine wall part;

Fig. 7 shows the light emitting unit of Fig. 6 when installed; Fig. 8 shows the light emitting unit of Fig. 6 for maintenance.

In the figures, the same or corresponding parts are designated with the same reference numerals.

Figure 1 shows a general arrangement of a wind turbine 1 having a wind turbine tower 2, a nacelle 3 and a wind turbine rotor 4 with rotor blades 5. The wind turbine 1 can be relatively high, in particular with the continuing development of increasing sized wind turbines, for producing more electricity and having larger rotor blades. Such wind turbines may form an obstacle for flying objects such as aircrafts and/or helicopter.

Thereto, the wind turbines are provided with obstacle lights. It is known to provide at least one obstacle light on top of the wind turbine tower, preferably on top of the nacelle. Due to the ever larger size of the wind turbine tower, it has become in use to provide the wind turbine tower with obstacle lights 6. The obstacle lights 6 typically are positioned at a certain height H above surface level L and there may be provided two, three or four obstacle lights evenly positioned on the circumference of the wind turbine tower at a certain height. Depending on the height of the tower, obstacle lights may be provided at multiple levels of different height above the surface level. In this general arrangement, four obstacle lights 6 are provided, evenly distributed over the circumference at height H, so with an angle of approximately 90 degrees inbetween. The surface level L may be a ground surface L or a water surface level L depending on the wind turbine being positioned onshore or offshore.

Usually, the wind turbine tower 2 is manufactured from multiple wall parts that may be built together onsite, or, for example in case of an offshore wind turbine, off-site. In such a wind turbine wall part, a through- hole may be provided in which a light emitting unit 6 may be inserted from the outside to the inside of the wind turbine wall part.

Figure 2 shows a schematic cross-sectional view of an obstacle light 6 according to the invention. A wind turbine tower wall part 2p is

schematically shown with the through-hole 7 provided in it. The light emitting unit 6 comprises a sleeve element 8 and an optic element 9 that is connected to the sleeve element 8. The optic element 9 can be configured to provide the desired light emitting pattern. The optic element 9 may also be configured as an optical neutral element, such as a dome, wherein the optic that provides for the light pattern may be behind the optic element 9. The sleeve element 8 is configured to be inserted from the outside to the inside only into the hole 7 in direction A. The wind turbine wall part 2p has an outer side 10 and an inner side 11. The sleeve element 8 has an outer side 8a that, after installation, is at the outside 10 of the wind turbine tower wall part 2p, and an inner side 8b that, after installation, is at the inner side 11 of the wind turbine tower wall part 2p.

The sleeve element 8 is configured such that it can be inserted from the outside to the inside only, along direction A, into the hole 7. Thereto, advantageously, the optic element 9 is connected to the sleeve element 8 at the outer side 8a of the sleeve element 8. When inserting the light emitting unit 6 into the hole 7, the inner side 8b of the sleeve element 8 is inserted first into the hole 7. Here, the inner side 8b of the sleeve element 8 is provided with a mounting element 12. Here, the mounting element 12 is embodied as a screw thread, which can cooperate with a nut to firmly lock the sleeve element 8 to the wall part 2p.

The sleeve element 8 is provided with a stop element 13, such that the sleeve element 8 can only be inserted in one direction into the hole 7. The stop element 8 is here provided at the outer end 8a of the sleeve element 8, such that the outer end 8a inner end 8b is to be inserted first into the hole 7. The stop element 13 is configured as to prevent insertion thereof into the hole 7, for example because the diameter of the stop element 13 is larger than the diameter of the hole 7. The stop element 13 may be embodied as a flange, or as outwardly extending fingers etc. Many variants are possible.

The optic element 9 can be connected to the sleeve element 8 in various ways, e.g. by means of an adhesive connection, or by means of a mechanical connection such as screwing or bolting or clicking, etc.

In figure 3, the light emitting unit 6 is shown to be inserted in the hole 7 of the wall part 2p. The stop element 13 abuts against the outside 10 of the wind turbine tower wall part 2p. Here, a sealing member 14 is provided to the stop element 13 that fits between the stop element 13 and the outside 10 of the wind turbine tower wall part such that the stop element 13 sealingly engages the wind turbine tower wall. Thereby, the sealing member 4 may provide for a barrier to environmental influences such as water and/or dirt, thus a safe and/or reliable connection of the light emitting unit 6 to the wind turbine tower wall 2 may be provided. Also at other positions a sealing member may be provided, for example between the sleeve element 8 and a wall 15 of the hole 7.

In the embodiment of figure 3, the light emitting unit 8 further comprises an inner element 16 on which a light emitting element 17 can be arranged. The light emitting element 17 can be an LED, and the inner element 16 may comprise some electronic components, e.g. a printed circuit board, for controlling the LED. In an embodiment, the inner element 16 may also be provided with an optic element providing the light pattern, for example when the optic element 9 may be a optical neutral dome.

The inner element 16 is preferably be provided with a connecting element 18 that may cooperate with a corresponding connecting element 19, e.g. at a cable end 20 to connect the inner element 16 with a power source and/or a control unit. The inner element 16 may be firmly connected to the sleeve element 8 via various well known techniques, such as adhesive, screwing, gluing, press-fitting etc. A nut 21 is provided that cooperates with the mounting element 12, here a screw thread, to fix the light emitting unit 6 to the wind turbine tower wall 2.

The sleeve element 8 is preferably tubular, having preferably a cylindrical outer wall to fit into the hole 7. The cross-section of an inner wall of the sleeve element 8 can have various shapes. For example, the cross- section may be triangular or star-like to allow easy cooperation with a triangular or star-like shaped inner element 16. Or, the cross-section of an inner wall of the sleeve element 8 may be provided with a screw thread that may cooperate with a correspondingly threaded inner element 16. Many variants are thus possible.

Figure 4 shows an alternative embodiment of the light emitting unit 6. The stop element 13 is here configured as a skirt at the outer end 8a of the sleeve element 8. The skirt 13 opens outwardly and is being closed by entering the sleeve element 8 into the hole 7. The skirt elements of the skirt 13 open outwardly and towards the outer end 8b of the sleeve element, as such, there is only one way of inserting the light emitting unit 6 into the hole 7. Preferably, the skirt 13 is biased towards their open position, and, by inserting the light emitting unit 6 into the hole 7, the skirt 13 is being closed against the bias until a fixed position is reached. The bias of the skirt 13 then may determine the position of the light emitting unit 6 in the hole 7. The stop element 13, as a skirt, may at the same time act as a sealing to prevent ingress of dirt and/or water. In this embodiment also the mounting element 12 is embodied differently. The mounting element 12 is embodied as a wing-like element that opens after insertion through the hole 7 and as such may provide for a firm mounting of the light emitting unit 6 to the wind turbine wall 2.

Further, in the embodiment of figure 4, it can be seen that the optic element 9 is provided onto a bus-shaped element 22, acting as an

intermediate sleeve element 22, which can be fixedly connected to the sleeve element 8. The inner element 16 may then be fixedly connected to the intermediate sleeve element 22.

In an embodiment, the light emitting unit 6 may comprise the sleeve element 8 and the optic element 9, wherein the light emitting element may be provided by a fiber optic cable or by a light emitting element e.g. on an inner element. The outer diameter of the sleeve element 8 may thus be reduced as to minimally allow for a fiber optic cable or an inner element with an LED. As such, the hole in the wind turbine tower may be reduced as well. The optic element 9 often may have certain dimensions as to provide for a determined light emitting pattern. As the optic element 9 may mainly be at the outer side of the wind turbine tower wall 2, the diameter of the sleeve element 8 behind the optic element 9 may even be smaller, thus the size of the hole 7 may possibly be reduced further.

The embodiment of figure 5 comprises a flange as a stop element 13 and a screw thread as mounting element 12 which can engage with nut 21. Further, a sealing member 14 is provided between the flange 13 and the outside 10 of the wind turbine tower wall part 2p. An inner element 16 is provided with an LED 17 at one end thereof and a connecting element 18 for a cable 20 at an opposite end thereof. The cable 20 connects the hght emitting unit 6 to a control unit 23 for controlling the light emitting units, e.g. flash patterns and/or light emitting characteristics, e.g. visible or infrared light.

Figure 6 shows the installation of the light emitting unit 6 from the outside to the inside, with the light emitting unit 6 configured such that it only can be inserted along the direction A into the hole 7. In this

embodiment, the inner element 16 with the light emitting element 17 is already provided to the light emitting unit 6.

During use, in figure 7, the light emitting unit 6 is inserted in the hole 7 and, via a cable 20, connected to a power source and/or a control unit. The optic element 9 extends partially outside of the wind turbine wall part as to provide a determined light pattern. For example, when in

circumferential direction two light emitting units 6 are provided, each light emitting unit 6 may have to emit light over an angle of at least 180 degrees, thus the optic element 9 may have to extend somewhat outside of the wall.

For repair and/or maintenance, for example for revising or upgrading the inner element or for replacing the hght emitting element, the inner element 16 may be removed from the light emitting unit 6. Then the inner element 16 may be replaced and/or repaired and may be re-inserted into the light emitting unit 6 and may be re-connected to the optic element 9 and/or the sleeve element 8.

Advantageously, the sleeve element 8, the optic element 9 and/or the inner element 16 are so connected as to form a single unit that can be installed at once in the hole 7. Preferably, it is only upon maintenance and/or repair that the connection between the sleeve element 8 and/or the optic element 9 and/or the inner element 16 is undone to remove the inner element 16 and/or the optic element 9. The sleeve element 8 is preferably permanently mounted to the wind turbine wall 2.

For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include

embodiments having combinations of all or some of the features described.

Many variants will be apparent to the person skilled in the art. All variants are understood to be comprised within the scope of the invention defined in the following claims.