The present invention relates to assemblies for wind turbine generators and to arrangements for accommodating backup generators and/or fuel supplies for backup generators.

Wind turbine generators are arranged to convert energy from wind into electricity which may be supplied to the mains electricity grid. Each generator requires a supply of power for auxiliary equipment such as safety systems, and this is usually supplied from a rechargeable battery which is recharged by a battery charger using power from either the output of the wind turbine generator itself or from the mains grid.

Wind turbine generators are often equipped with a backup generator, such as a diesel generator, for supplying power to the auxiliary equipment and/or the battery charger when there is no wind and/or in the event of the wind turbine generator becoming disconnected from the mains grid.

The present invention seeks to provide improvements to such wind turbine generators.

Thus, in accordance with a first aspect of the present invention there is provided an assembly comprising:

a tower for supporting a wind turbine generator, the tower comprising a wall having an outer surface which in use is oriented substantially vertically; and

a backup generator mounted to the outer surface of the wall, the arrangement being such that the weight of the backup generator is supported substantially only by the wall of the tower.

By using the tower to support the weight of the backup generator, this avoids the need for an additional support structure. Furthermore, by providing the backup generator in a location which is external to the tower, this provides the following technical advantages: (a) the backup generator can readily be accessed by service personnel without having to enter the tower; (b) heat generated by the backup generator can more readily be dissipated; and (c) in the event of the generator developing a fire, this can more readily be extinguished. The backup generator is preferably mounted to the wall of the tower by one or more bolts, since this does not require internal access to the tower.

In a preferred arrangement, the backup generator is housed within a cabinet. This provides protection from rain and other adverse weather conditions.

In this case, the cabinet is preferably mounted to the wall of the tower by one or more bolts. In this way, the cabinet can be attached to the wall of the tower without requiring internal access to the tower.

The backup generator is conveniently powered by a fuel, for example, diesel, gasoline or natural gas. This provides the advantage that, in combination with a supply of the fuel, the generator can be self-contained and not require an external source of power. In the preferred embodiment, the backup generator is powered by diesel fuel.

The assembly preferably further comprises a platform mounted to the tower at a position which, in use, is below the backup generator. This provides a suitable support surface for service personnel when servicing or repairing the backup generator. The platform preferably extends fully around the perimeter of the tower to provide service personnel with suitable access to all sides of the tower.

In the preferred embodiment, a stairway is arranged between the platform and an upper surface which in use is above the backup generator, the arrangement being such that the footprints of the upper surface and the backup generator overlap when viewed downwardly.

The upper surface is preferably attached to the tower such that the weight of service personnel standing on the upper surface is transferred to the tower without requiring additional support from below. The expression "footprints" is here intended to refer to the horizontal area occupied by the upper surface and the backup generator. With such an arrangement, the functionality of the stairway and the backup generator can be combined in a compact arrangement. Indeed, in the preferred arrangement in which the footprint of the backup generator is wholly within that of the upper surface, no additional area of the platform is required for the provision of the backup generator. When the backup generator is housed within a cabinet, the cabinet itself may comprise the upper surface. Thus, when the cabinet is mounted to the tower, the weight of service personnel standing on the upper surface is transferred to the tower without requiring additional support from below.

The stairway is advantageously located adjacent the tower. The word "adjacent" is intended to mean that personnel climbing the stairway do not face the tower. This enables personnel to climb the stairway while remaining close to the tower. Furthermore, if any guiderails are provided on the stairway, these need only be positioned on the one side of the stairway remote from the tower, i.e. on the external side of the stairway.

In accordance with a further aspect of the present invention there is provided an assembly comprising:

a tower for supporting a wind turbine generator, the tower comprising a wall having an outer surface which in use is oriented substantially vertically; and

a fuel tank for a backup generator mounted to the outer surface of the wall, the arrangement being such that the weight of the fuel tank is supported substantially only by the wall of the tower. By using the tower to support the weight of the fuel tank, this avoids the need for an additional support structure.

Furthermore, by providing the fuel tank in a location which is external to the tower, the fuel tank can readily be accessed by service personnel without having to enter the tower.

The fuel tank is preferably mounted to the wall of the tower by one or more bolts, such that the fuel tank can be attached to the wall of the tower without requiring internal access to the tower. Although not a feature of the preferred embodiment, it would be possible to house the fuel tank within a cabinet to provide additional protection from rain and other adverse weather conditions.

Wind turbine towers are typically circular in cross section. When this invention is applied to such circular towers, the fuel tank is also preferably curved so as to match the profile of the outer surface of the tower and thereby reduce the footprint of the fuel tank. Furthermore, by matching the profile in this way, it is easier to mount the fuel tank to the tower.

The above arrangements can conveniently be combined. Thus, the assembly preferably further comprises a fuel tank for the backup generator, the fuel tank being mounted to the outer wall of the tower, the arrangement being such that the weight of the fuel tank is supported substantially only by the wall of the tower.

In embodiments which include both a fuel tank and a platform, the platform is preferably formed with an extended area to enable personal to walk freely around the front of the fuel tank.

The present invention extends to a wind turbine generator comprising any of the above- described assemblies.

In accordance with a further aspect of the present invention there is provided a method of installing a tower for a wind turbine generator, the method comprising forming an assembly as claimed in any one of claims 1 to 12 prior to installing the tower. Thus, the assembly can be formed at a convenient location, such as within a manufacturing plant, and the completed assembly then transported to the desired location of the wind turbine generator.

This invention is particularly advantageous when the wind turbine generator is to be located offshore, in which case the assembly is preferably formed at an onshore location prior to transportation and installation at the desired offshore location.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 illustrates an assembly of a backup generator, a fuel tank and a wind turbine generator tower in accordance with a preferred embodiment of the present invention;

Figure 2 illustrates the assembly of Figure 1 from a different angle; Figure 3 is a front view of the arrangement of Figure 1 with the backup generator door open;

Figure 4 is a flowchart illustrating a method of installing the assembly of Figure 1 ; and

Figures 5(a) to 5(h) illustrate in pictorial form a method of installing the assembly of Figure 1.

Referring to Figure 1 , a tower 1 for supporting a wind turbine generator (not shown) is mounted in an offshore location. A platform 2 is attached to the tower 1 and enables personnel to perform servicing operations both inside and outside the tower 1. A safety railing 3 is provided at perimeter of the platform 2.

The tower 1 is provided with a side door 4 for use by service personnel for performing maintenance operations inside the tower 1.

The side door 4 is accessed from the platform 2 by means of a stairway 5 which leads to an upper platform 6. The upper platform 6 is formed by the upper surface of a cabinet 7 which houses a diesel backup generator (not shown) for supplying auxiliary equipment within the wind turbine generator with backup power in the event of a failure in the connection to the mains electricity grid and/or when there is no wind to power the turbine. The stairway 5 is positioned immediately adjacent the tower 1 and is provided with a single handrail 8 on the left-hand side of the stairway 5 as viewed when climbing the stairway 5. A safety railing 9 is provided around the upper platform 6. As can be seen from the drawing, the cabinet 7 defines a substantially rectangular footprint on the platform 2 which does not extend beyond the sides of the upper surface of the cabinet 7.

Both the cabinet 7 and the diesel backup generator are mounted directly to the tower 1 by bolts (not shown) such that both the cabinet 7 and the backup generator are fully supported by the tower 1 and not by the platform 2.

An exhaust pipe 10 extends vertically from the backup generator and expels exhaust gases at a position well above the generator cabinet 7. The walls of the generator cabinet 7 are provided with grilles 11 to allow for heat dissipation during operation. Also mounted to the tower 1 is a curved fuel tank 12 containing diesel fuel for the backup generator. Referring to Figure 2, in which the same reference numbers are used to indicate the same or corresponding features, the fuel tank 12 is mounted to the wall of the tower 1 using bolts 13. As can be seen in the drawing, the fuel tank 12 is curved so as to adopt the same profile as the wall of the tower 1. A fuel pipe 14 conveys diesel fuel from the fuel tank 12 to the diesel backup generator within the generator cabinet 7.

The platform 2 is of sufficient size to enable service personnel to walk around the complete perimeter of the tower 1. Since the fuel tank 12 occupies a considerable area of the platform 2, the platform 2 is formed with an extended area 2 (illustrated in the drawing by the shaded area 2'), to enable service personnel to walk freely around the fuel tank 12.

Referring to Figure 3, in which the same reference numbers are again used to indicate the same or corresponding features, the front wall of the generator cabinet 7 forms a door 15 which enables maintenance personnel to access the backup generator 16 inside the generator cabinet 7.

The method of installation of the assembly will now be described with reference to Figures 4 and 5(a) to 5(h).

Referring to the flowchart of Figure 4, a diesel backup generator is bolted to the outer wall of a wind turbine tower in step 17. A cabinet for housing the backup generator is then positioned over the generator and bolted to the outer wall in step 18. A diesel fuel tank is bolted to the outer wall of a wind turbine generator tower in step 19. The resulting assembly is then transported to the desired offshore location in step 20. Finally, the assembly is installed in the desired offshore location in step 21.

Referring to Figures 5(a) to 5(h), support brackets for the diesel generator and diesel fuel tank are first bolted to the tower, in an onshore location (Figure 5(a)). A diesel generator is then mounted on the associated support brackets (Figure 5(b)) and bolted to the outer surface of the tower. The generator cabinet and integral stairway are positioned so as to house the diesel generator and are then bolted to the tower (Figure 5(c)). A diesel tank is then lifted into position on the associated support brackets (Figure 5(d)) and bolted to the outer surface of the tower. The resulting completed assembly is then lifted on to an installation vessel by a crane mounted on the vessel (Figure 5(e)). After being transported to the desired offshore location, the assembly is lifted off the installation vessel by the crane (Figure 5(f)) and moved towards a platform (Figure 5(g)). Finally, the assembly is installed on the platform (Figure 5(h)).

Although preferred embodiments of the present invention have been described above, it will be apparent that numerous modifications may be made without departing from the scope of the present invention which is defined by the following claims.