System for maintenance of a multi-rotor wind turbine assembly

Abstract

The present invention concerns a system for the installation, removal and maintenance of components of a multi-rotor wind turbine assembly. The assembly comprises a track system integrated within the support structure for both installing and removing assembly components, as well as for carrying out the in-situ repair of faulty components.

Description

[0001] SYSTEM FOR MAINTENANCE OF A MULTI-ROTOR WIND TURBINE ASSEMBLY

[0002] TECHNICAL FIELD

[0003] The present invention concerns a multi-rotor wind turbine assembly, comprising a system for the installation, maintenance and / or removal of assembly components.

[0004] BACKGROUND

[0005] In recent years, there has been significant research & development into the use of multi-rotor technology in the wind industry. However, to date, with apparently limited commercialisation, the industry is still dominated by large-component systems which tend to feature a single rotor on a tower, the height of which may typically be around 250-300m tall. The rotor blades themselves are usually 80-100m in length.

[0006] To maximise the benefits of multi-rotor wind turbines, an efficient maintenance system must be included in the design. Ideally, the system will negate the need for external lifting equipment and allow the repair and replacement of rotor and nacelle components in a timely manner.

[0007] The installation, maintenance, service and removal of components of a multi-rotor assembly is a challenge, as component parts need to be fully isolated, and moved, repaired or replaced, without causing disruption to the remaining components of the multi-rotor assembly for these assemblies to be fully effective.

[0008] Current approaches to installation, maintenance and removal of assembly components are usually conducted with cranes; either a ground level crane onshore, or a crane vessel offshore for fixed bottom, or a tow to port approach for floating wind where a port-side crane is used. The use of a crane allows access to and servicing of the components, and technician access is normally achieved from inside the wind turbine tower. However, it can be extremely difficult, or impossible to access all areas of a multi-rotor wind turbine that uses a lattice support structure using cranes. This can cause a narrow design space for multi-rotor wind turbines as the designer must consider a system that is accessible by cranes, leading to sub-optimal designs using large cantilever beams to allow access via cranes. Most wind turbine farms rely on external crane hire services, which can be expensive and require large lead times to secure a crane with adequate lifting capabilities. This is particularly true offshore, where heavy lift vessels and jack up vessels are scarce and can cost upwards of £0.5 million a day to hire. Additionally, the use of cranes is not possible in all weather conditions, such as high winds. A number of different multi-rotor design concepts are reviewed in P. Jamieson et al., “Innovative Turbine Concepts - Multi-Rotor System" in INNWIND Deliverable Report 1.33 (www.innwind.eu / publications / deliverable-reports) (August 2015). The inclusion of lifting equipment built into the structure is mentioned, but assumes a permanent crane positioned near the top of the structure. The disclosures lack any detail and are simply a stated assumption based on modelling work. There would be numerous problems associated with having a permanent crane attached near the top of such a large structure, such as weathering, corrosion, access for servicing, and lack of access to all rotor positions in the multi-rotor system. Similar examples of built in lifting equipment with little detail are made in academic work such as J. McMorland et al., “Operation and Maintenance Modelling for Multi Rotor Systems: Bottlenecks in Operations", J. Phys.: Conf. Ser, 2022, 2265 (4), 042059, P. Pirrie et al., “Comparison of electrical collection topologies for multi-rotor wind turbines", Wind Energ. Sci., 2020, 5, 1237-1252 and II. Giger eta / ., “Design Study of Multi-Rotor and Multi-Generator Wind Turbine with Lattice Tower— A Mechatronic Approach" , Appl. Sci., 2021 , 11 (22), 11043.

[0009] WO2019120460 details a method of handling a wind turbine component in a wind turbine comprising a tower extending in an upwards direction, a load carrying structure fixed to the tower and extending in an outwards direction transverse to the upwards direction. According to the method described a crane with a fixation structure is provided and raised to the level of the load carrying structure by use of a hoisting rope. Once in position, the crane is used for handling the wind turbine component. This would not be possible with a lattice support structure multi-rotor wind turbine as the hoisting rope would need to travel through the lattice framework where the structure would block the path of the hoisting rope and crane.

[0010] WO2018001429 details a wind turbine comprising a tower structure configured to hold a nacelle with a rotor and a parking structure for holding the rotor. To improve the ability to carry out maintenance and to allow easier assembly and disassembly of the wind turbine, the parking structure detailed is configured to connect the rotor directly to the tower structure to thereby allow removal of the nacelle while the rotor remains fixed to the tower structure. This method must either rely on the use of external cranes to move the parking structure and lifting equipment into place or have permanent parking structure and lifting equipment left on the structure, causing increased risk of damage, weathering and failure. A system where the parking structure and crane are hoisted to the required position could be envisaged, but such a system would not be possible in a lattice style support structure required for large amounts of rotors in a multi-rotor system. LIS2018023542 details a wind power plant, comprising a platform having a deck and configured for supporting a frame, where the frame comprises a plurality of generator stations, configured for receiving and supporting a respective removable wind turbine generator, and a generator conveyance means configured and arranged for moving a wind turbine generator between the deck and a generator station. The generator station is moved first along the deck, then upwards to its required position via a series of lifting systems that are built into each column of the structure. The generating units must be tilted 90° from a vertical to horizontal position and vice versa throughout this process, adding considerable complexity and cost to the design. This type of system required highly bespoke generating units and would not be applicable to well established and understood wind turbine generating units.

[0011] GB2577643 details a method for assembling a wind turbine and a wind turbine system. In some aspects it also relates to a vessel, such as a ship, that can be used to transport a rotornacelle assembly, an elevator carriage for a wind turbine, and a method for servicing a wind turbine. Although this system describes a possible solution to no longer rely on external cranes for installation and maintenance of single rotor turbines, the system would not be suitable for multi-rotor configuration as it only allows for a rotor nacelle assembly to be transported from one fixed point to one other single fixed point at the top of a tower. This system also relies on tilting the rotor nacelle assembly during its movement, which adds considerable cost and complexity to the design.

[0012] However, to date none of the prior art satisfactorily provides a system for the simple and easy installation, removal or maintenance of multi-rotor wind turbine assemblies that use lattice style support structures without the use of external lifting equipment such as large cranes or heavy lifting vessels, and in all weather conditions, particularly including high wind conditions.

[0013] SUMMARY OF THE INVENTION

[0014] According to a first aspect of the present invention, there is provided a system for the installation, assembly, removal and / or maintenance of a component of a multi-rotor wind turbine assembly, the system comprising an integrated track extending between an operational site of the component and a transitional site of the component.

[0015] The multi-rotor wind turbine assembly may comprise a multiplicity of wind energy generation components supported by a structural support system. The multi-rotor wind turbine assembly may, for example, comprise a support tower and a structural framework extending laterally from the support tower. The structural support system may comprise for example one or more supporting arms and / or a structural framework upon which components may be securely mounted.

[0016] Alternatively, the multi-rotor wind turbine assembly may comprise a support platform and a structural framework extending from the support platform.

[0017] The integrated track may extend along, or in association with, a structural member of the structural framework or support structure. In particular embodiments the integrated track extends substantially perpendicularly with respect to the support tower.

[0018] Thus, the invention provides means for transferring the component between its operational site (securely mounted on the structural support system) and its transitional site from which the component may be readily accessed or extracted for installation, assembly, maintenance, replacement, remediation or repair. In some embodiments the integrated track may extend through or within the support structure and / or structural framework.

[0019] The component may comprise a rotor-nacelle assembly or a component part thereof. For example, the component may comprise component parts, sub-assemblies (for instance a generator or power electronic converter) or assemblies (for instance the entire nacelle assembly).

[0020] The integrated track may comprise one or more rails.

[0021] In preferred embodiments, the integrated track system is substantially horizontal or parallel to the surface. The skilled addressee would understand that the integrated track would be, in this embodiment, perpendicular to the support tower. Preferably, the surface is the ground, but in some instances may be the surface of a body of water. In such embodiments, elevation to or from the ground is achieved by a lift system. Advantageously, in such an embodiment, only horizontal rail systems are required, as vertical elevation is provided by a lift, which transfers the component from the ground rail system to the elevated rail system.

[0022] A substantially horizontal rail system is preferable to a vertical rail system, as it avoids requiring complex pivoting of components into position, for instance. Components or maintenance equipment are first moved upwards, and then traverse along a row, to the desired location of the modular assembly. Advantageously moving components or equipment upwards first, and then horizontally, simplifies the system considerably, as the lifting process is much more costly and complex to execute compared to the sideways movement. Thus, this embodiment presents a significantly reduced system cost and complexity.

[0023] In preferred embodiments, where the integrated track system is substantially horizontal, the present invention is considerably simpler and provides greater flexibility in arrangement than existing systems in the art, as the rotor nacelle assemblies (RNAs), components or maintenance equipment can be moved around more freely using the horizontal track system, as opposed to alternative systems which require additional tilting assemblies, for example, to move the components between separate track / rail systems. Additionally, the horizontal configuration allows for maintenance to be carried out in situ, which would not be possible in a vertical configuration.

[0024] The component may comprise means for its moveable mounting on the track.

[0025] The system of the invention is adapted to transport the component along the track from the operational site to the transitional site (in a removal or maintenance procedure) or from the transitional site to the operational site (in an installation or assembly procedure).

[0026] The transitional site of the component may be at or towards the support tower and the operational site of the component may be laterally remote from the support tower.

[0027] In some embodiments, there may be more than one operational or transitional site along the integrated track. In such an example, the system of the invention may be adapted to transport the component and / or maintenance equipment along the track to / from a transitional site to a first and / or second operational site.

[0028] In an exemplary embodiment, the operational site may be a rotor nacelle assembly and / or the transitional site may be a lift system.

[0029] Operational and / or transitional sites may be in an elevated position with respect to the surface on which the assembly is mounted. For example, in the case of a ground-based wind turbine the assembly will typically be mounted in an elevated position with respect to the ground by means of a suitable support structure, for example a tower upon which the assembly is mounted. In another example, in the case of a water-based wind turbine, the assembly will typically be mounted in an elevated position with respect to either the surface of the water, or a platform floating on the surface of the water.

[0030] The transitional site of the component may be associated with a supporting structure of the assembly. For example, when the support structure comprises a tower, the transitional site may be a location on the tower.

[0031] Consequently, the invention provides a system for installation, removal and / or maintenance of components of a multi-rotor wind turbine assembly, comprising a support tower and a structural assembly, forming a support structure, wherein a track system is integrated within the support structure. The structural assembly may be modular, and in such embodiments the structural assembly may be made up of a multiplicity of structural frameworks.

[0032] In preferred embodiments the multi-rotor wind turbine assembly may comprise a multiplicity of rotor assemblies mounted on a support structure.

[0033] The multi-rotor wind turbine assembly may further comprise a moveable element cooperating with a mechanical transmission means, a generator means and an electrical power transmission means using a rotor shaft, such as in the arrangement of a wind turbine rotor and its associated nacelle assembly. The nacelle assembly may comprise at least one generator means.

[0034] In particular embodiments of the present invention there may be a joint on the rotor shaft, such that the rotor and its associated nacelle assembly can be separated from one another. The joint may be a flanged joint, sliding connection, threaded spin collar arrangement, bolted connection, quick release / lock mechanisms, or another appropriate connection mechanism that allows for disconnection of the rotor and the nacelle components.

[0035] The components may be installed in the assembly or removed from the assembly by means of the track system integrated into the support structure. The components may be moved along the track system using an actuation method, such as a remote-controlled motor, winch system, or through motorised tracks. The components may be moved between their operating position and the support tower of the support structure in this manner, thus providing a simple means for the replacement and maintenance of the components. A remote-controlled motor, which may be referred to as a “track-bot”, may be a small car that travels along the track system and can move the components into position, either automatically or through remote controlled operation. The support tower of the multi-rotor wind turbine assembly may comprise a lift system by which components can be lowered from the track system to ground level, and / or raised from ground level to the track system. The lift system may also comprise its own integrated track, which forms an extension of the assembly track system when at the elevated position. Therefore, in such an embodiment the lift track would link up with the track system integrated into the support structure, facilitating seamless movement of components from the lift system to the integrated track system, and vice versa. The lift system may, in some embodiments, be able to rotate about its vertical axis, in a similar manner to a railway turntable. This provides a means through which the assembly components to be moved around different parts of the structure.

[0036] The lift system may be internal, or at least partly internal, within the structure of the support tower, or external, on the outside of the support tower.

[0037] In embodiments wherein the lift system is internal, components for installation or removal may be introduced / removed from the lift system through an opening at the base of the tower. This operation may be carried out by a service vehicle or an operator at ground level.

[0038] In said embodiments wherein the lift system is internal, the lift platform may be elevated by means of a vertical track system, a hydraulic system, a cable system, a winch system, a counterweight system, or any other suitable method of actuation.

[0039] In embodiments wherein the lift system is external, components for installation or removal may be introduced / removed from the lift system by a service vehicle or an operator at ground level. In said embodiments wherein the lift system is external, the lift platform may be elevated by means of a secondary track system on the outside of the support tower, which may operate by means of a vertical track system, a hydraulic system, a cable system, a winch system, a counterweight system, or any other suitable method of actuation.

[0040] In an additional embodiment where the lift system is external, the lift system may be directly mounted to the support structure, rather than the support tower. In this case, there may be a split present in the lift system to allow the support structure to align with the predominant wind direction, and the lift system may be capable of traversing said split.

[0041] In a particular embodiment of the present invention, the system may be used for maintenance of the multi-rotor wind turbine assembly components. In this embodiment lifting and / or maintenance equipment may be provided in association with the track system. Thus, the equipment may be raised to the level of the assembly components using the lift and moved to a component requiring maintenance using the track system. The lifting equipment may be a fixed, articulating, or telescopic crane arm that is able to move in at least about 3-6 degrees of freedom. This allows for the maintenance of the assembly components in situ, which increases the efficiency and speed of repairs.

[0042] In some embodiments components may be mounted directly to the maintenance and / or lifting equipment, such as a crane, which may in turn comprise means for its moveable mounting on the track system.

[0043] In other embodiments the lifting and / or maintenance equipment may include a base plate capable of mounting components securely for movement along the track system.

[0044] The lifting equipment may also include a base plate on which components, sub-assemblies (for instance a generator or power electronic converter) or assemblies (for instance the entire nacelle assembly) can be securely mounted and moved along the tracks together with the lifting equipment to the lift. The lifting equipment may also optionally be fitted with a cable spool and blade lifting attachment to allow for removal and lowering to ground level of a single blade or rotor, or the entire rotor nacelle assembly. This allows the system to carry out small repairs in-situ and also larger repairs which require the removal and replacement of components, sub-assemblies, or assemblies, while using the same track and lift system.

[0045] The present invention therefore provides the ability to conduct the majority of maintenance operations without the use of external lifting equipment and additional cabling, therefore permitting operation in higher wind speeds, as well as the ability to quickly and safely move the actuation system to the location of the faulty component, and the ability for components to be moved between the turbine and ground level systems (such as service vehicles) more easily without the addition of any ground-level lifting or similar operations.

[0046] Advantageously, the present invention provides the option of either complete unit removal and / or replacement, or partial generating unit removal and / or replacement, replacing components for example. Thus, the system of the present invention is much more flexible and allows for an optimised maintenance system in which minor faults can be repaired in situ with the assistance of specialised maintenance equipment, such as a small crane, which may be moved into place with the system. For major faults, the whole generating unit may be removed, for example the nacelle structure can be removed. The decision of which method to use may be determined by the maintenance procedure time. In preferred embodiments, the fastest procedure is used to minimise maintenance time, and reducing turbine downtime.

[0047] According to a second aspect of the present invention there is provided a process for the installation of multi-rotor wind turbine assembly components, comprising: introducing the component to the lift system at ground level; raising the component from ground level to the level of the assembly using the lift system; moving the component along the track system to the assembly; and connecting the component to the assembly.

[0048] According to a third aspect of the present invention there is provided a process for the removal of multi-rotor wind turbine assembly components, comprising: disconnecting the component from the assembly; moving the component along the track system to the lift system; lowering the component to ground level from the level of the assembly using the lift system; and removing the component from the lift system at ground level.

[0049] The user would understand that the process according to the second and third aspects of the present invention could be carried out in unison, or separately.

[0050] According to a fourth aspect of the present invention there is provided a process for the in-situ maintenance of multi-rotor wind turbine assembly components, comprising: introducing maintenance equipment to the lift system; raising the maintenance equipment to the level of the component; moving the maintenance equipment along the track system to the component; carrying out maintenance of the component in situ, and following completion of maintenance of the component, returning the equipment to ground level by means of the track system and the lift system.

[0051] According to a fifth aspect of the present invention there is provided a multi-rotor wind turbine assembly, comprising a multiplicity of renewable energy generation components supported by structural framework, which is held up by a tower, wherein a track system is integrated within the structural framework.

[0052] DETAILED DESCRIPTION One of the core advantages of a multi-rotor wind turbine assembly (with respect to conventional single-rotor turbines), is that smaller components can be used, simplifying manufacturing, logistics, installation, maintenance operations, and transport.

[0053] Scaling down components to a more manageable size reduces reliance on the use of specialised transportation, installation and maintenance equipment; reduces the requirement of large lifting equipment to be used during installation; reduces the requirement of specialised manufacturing techniques - with concomitant reduction in supply chain bottlenecks; and opens up hard-to-reach sites that have previously been deemed infeasible due to access issues. The integrated track system reduces the reliance of heavy equipment for the maintenance and renewal of the assembly, which significantly increases the useful lifetime of the installation.

[0054] The multi-rotor wind turbine assembly may be supported by a superstructure comprising at least a support tower. The support tower may have a yaw system to allow the entire structure to align with the wind, and therefore permit the efficient generation of energy.

[0055] The superstructure of the multi-rotor wind turbine assembly may be manufactured from any suitable material such as metal, metal alloys, steel, aluminium, scandium and alloys thereof, fibre-reinforced plastics, thermoplastic resins and composite materials.

[0056] The superstructure may comprise a structural framework or lattice supported on the support tower. The superstructure may further support a modular framework or comprise the modular framework itself. The structural framework may have a layered structure the interstices of which accommodate, at least in part, rotor-nacelle assemblies (the rotor itself may extend outside the accommodating space formed by the interstices of the layered structural framework). The structural framework layers may be braced for additional strength.

[0057] The structural framework may have a polygonal cross-section, preferably a tessellating crosssection. Thus, the array may be an array of triangles, squares, rectangles, hexagons or substantially any other tessellating shape. In an assembly according to the invention, preferably each of a multiplicity of renewable energy generation components, such as rotornacelle assemblies, within the body of the framework (except around its edges) may be paired together in a connective manner to a plurality of other renewable energy generation components; preferably to n other components, wherein n is the number of sides of the structural framework polygon. The RNAs are preferably mounted on the framework between neighbouring interstices, more preferably on, adjacent to or towards the nodes of the framework between multiple neighbouring interstices. In most preferred embodiments, the RNAs are mounted adjacent to the nodes, as this provides greater access to the framework during assembly. Attachment on a node whilst possible, is a challenge, due to the intersection of multiple components.

[0058] It will be apparent to the skilled addressee that the structural framework may alternatively comprise any suitable means for supporting renewable energy generation components, such as rotor-nacelle assemblies, in association with the superstructure, provided that it is possible to integrate a track system capable of transferring renewable energy generation components along the track to and / or from an operational and transitional locations.

[0059] The structural framework of the multi-rotor wind turbine may be modular as disclosed in our co-pending GB2215766.3 and PCT / EP2023 / 079469, the contents of which are hereby incorporated by reference. Modularity may take several different configurations. Modules may be easily connected and installed on-site, but in some cases groups of modules may be connected off-site first. In some cases, however, it may be desirable to provide a superstructure on which the modular units may be mounted. In some embodiments, the multirotor wind turbines are modular in the sense not only that multiple energy generation components may be cooperatively provided together, but also in that each energy generation component is supported by a modular structural framework such that there exists modularity not just of the energy generation components but also of the supporting structure for the assembly. In embodiments where the multi-rotor wind turbines are modular, individual modules may be paired together structurally, and optionally, electrically. Structural pairing of components of the modular renewable energy generation assembly may be affected by mechanical connection, for example bolted, flanged, threaded, bracketed, clamped interlocking, hook and loop hinge, pinned and / or wedged connections. Adhesive or other form of chemical attachment such as welding may also be envisaged.

[0060] Typically, means may be provided for adjusting the height of the assembly, for example elevating the assembly into a higher wind-speed environment. Height adjustment or elevation means may be conveniently provided by a tower provided with means for receiving and mounting the assembly, either pre-or post-assembly. The tower itself may be of modular construction. The structural framework may be mounted directly on the support tower. Alternatively, the structural framework may be mounted on the support tower via an interfacing subsystem. In some embodiments the interfacing subsystem is configured to align the plurality of rotor nacelle assemblies mounted on the structural framework with the prevailing wind direction. The interfacing subsystem may be a yaw system.

[0061] According to the present invention, the renewable energy generation component is a wind turbine, and the assembly is a multi-rotor wind turbine (MRWT).

[0062] One of the core advantages multi-rotor wind turbines (MRWT) is that smaller components can be used, simplifying manufacturing, logistics and transport. However, designing the support structure using large components, or as one monolithic superstructure nullifies this benefit somewhat, as those large components would require highly specialised transport, manufacturing and lifting / installation equipment. Advantageously, the modularity of the supporting structural framework reduces reliance on the use of specialised transportation equipment; reduces the requirement of large lifting equipment to be used during installation; reduces the requirement of specialised manufacturing techniques with concomitant reduction in supply chain bottlenecks; and opens up hard to reach sites that have previously been deemed infeasible due to access issues associated with challenges in transportation of large components parts. The maintenance system of the present invention facilitates the construction and / or maintenance of such MRWT systems, while aligning with the benefits of modularity and improved transportation by removing the requirement of large lifting equipment such as cranes and heavy lift vessels.

[0063] The renewable energy generation component, the wind turbine, typically comprises a moveable element cooperating with mechanical transmission means, generator means, and electrical power conversion and transmission means. These elements when applied to a wind turbine may collectively be referred to as a rotor-nacelle-assembly (RNA). Industrial realisation of multi-rotor wind turbines requires assembly and cooperation of multiple RNAs in a support structure.

[0064] The system according to the invention presents numerous advantages compared to conventional single rotor wind turbines. The system allows the system to be maintained without the requirement of any external lifting equipment, such as large cranes, heavy lift vessels, or jack up vessels. Large lifting equipment used for major component replacement are often scarce, expensive, and take extensive time to set-up on-site. Therefore, the system according to the invention reduces the down time of turbines, removing the need for large lifting equipment hire, reducing the maintenance operational time, and ultimately reducing the cost of maintenance operations for wind turbines. In addition to these benefits, the system minimises the use of cables in lifting operations by utilising the built-in lift system. Maintenance operations may therefore be performed in higher wind speed conditions compared to conventional single rotor turbines. The system allows for either a more traditional approach to maintenance for minor faults, where faults are repaired in situ, or an approach where maintenance times are reduced by simply removing the faulty component, sub-assembly, or assembly and repairing it off site. The system according to the present invention is particularly applicable for major repairs and component replacement, which can cause excessive downtime in current large single rotor turbines.

[0065] The integrated track maintenance system and the associated assembly containing said track system may be land or water based. It may be utilised for onshore or offshore fixed bottom systems, or floating systems. In embodiments where the wind power generation assembly is a floating system, the structural framework may be mounted directly onto a floating superstructure, or may consist of multiple support towers, and it may be tethered to the sea or riverbed by cabling or other suitable means.

[0066] The invention will now be more particularly described with reference to the following examples and figures, in which;

[0067] Figure 1 shows a simplified schematic view of a multi-rotor wind turbine assembly in accordance with the invention, from both the front and the side.

[0068] Figure 2 shows a schematic view of an exemplary embodiment of a multi-rotor wind turbine assembly in accordance with the invention, from the back

[0069] Figure 3 shows a schematic view of the rotor nacelle assembly connection system (3A) and how the nacelle may be disconnected from the rotor (3B).

[0070] Figure 4 shows a schematic view of a MRWT embodiment with numerous rotors on one row and the integrated track system, both during movement of a nacelle to the lift (4A) and when the nacelle assembly is contained within the lift (4B).

[0071] Figure 5 shows a schematic view of an internal tower lift system at it’s base from a top- down view (5A); where the components are moved into and out of the lift by a track system (5B), or by a service vehicle (5C). Figure 6 shows a schematic view of an internal tower lift system at it’s base where maintenance equipment such as a lifting system is moved into and out of the lift by a track system (6A), or by a service vehicle (6B).

[0072] Figure 7 shows a schematic view of an external tower lift system from the front (7A) and from the side as it approaches the structural framework (7B).

[0073] Figure 8 shows a schematic view of a maintenance crane performing a blade lift operation, in accordance with the invention.

[0074] Figure 9 shows a multi-rotor wind turbine assembly in accordance with the invention where RNA maintenance is being carried out, from the front (9A) and another angle (9B).

[0075] Figure 10 shows a schematic view of a maintenance crane performing a maintenance operation in which the generator is removed from the nacelle bedplate, in accordance with the invention.

[0076] Referring to Figure 1 there is shown a schematic view of a multi-rotor wind turbine assembly (100) according to the invention comprising a supporting tower (101), which holds a support structure (102) on which are mounted the individual rotor-nacelle assemblies (103) each comprising a wind-responsive rotor (104) connected to a nacelle assembly (105), which includes a generator and supplying power to a remote location via cabling or other means of power transmission associated with each module. Each rotor (104) may comprise at least two blades. Figure 1 A shows a front view, and Figure 1 B shows a side view of the multi-rotor wind turbine assembly. It will be apparent that many other configurations may be envisaged.

[0077] Referring to Figure 2, there is shown an exemplary embodiment of a multi-rotor wind turbine assembly (200) in accordance with the invention, comprising a supporting tower (201), which holds the support structure (202). In this embodiment, the support structure (202) is shown comprising a structure mounted to the tower (202a) which supports a framework (202b). The support structure (202), and its components (202a, 202b) may be modular in nature. Individual rotor-nacelle assemblies (203) are mounted on the support structure (202), each comprising a wind-responsive rotor (204) connected to a nacelle assembly (205) which includes a generator and supplying power to a remote location via cabling or other means of power transmission associated with each module. Each rotor (204) may comprise at least two blades. When components of the rotor-nacelle assembly (203) are required to be moved (for installation, maintenance, or other), the components may be connected, disconnected and / or repaired by means of a track system (206), which may support a crane (207a, 207b) which may be mounted on a base plate (208) that has space to mount RNA components, subassemblies, or assemblies. Crane (207a) is shown performing a blade lift operation. The same crane (207b) is shown in its compact position, approaching an RNA to perform a maintenance operation on the nacelle assembly (205).

[0078] The components, cranes and / or maintenance equipment may be moved using the track system (206), which may include an additional actuation system, such as a small “track-bot”, which is also mounted on the track system, a winch system, or motorised tracks. In one embodiment, the nacelle assembly (205) may be moved directly along the tracks (206) to the tower (201) of the assembly. In another embodiment, the nacelle assembly (205), its subassemblies, or its components may be removed using the crane (207a, 207b), and mounted on the base plate (208) to be moved along the track (206) to the lift (209). The tower (201) comprises a lift system (209) which contains vertical tracks. The lift system (209) is shown as an external lift system in this figure, but it may also be internal. In the case of an internal lift, the lift system (209) may or may not include the ability to rotate about its vertical axis using a turntable. The lift system (209) raises or lowers the nacelle assemblies, sub-assemblies, and / or components along with maintenance equipment to or from the ground, by moving up or down the support tower (201), by means of a vertical track system (210).

[0079] Referring to Figure 3 there is shown a schematic view of the rotor nacelle assembly connection system (3A) and how the components are disconnected (3B). In Figure 3A it is shown that, unlike a conventional wind turbine, the rotor’s (301) main bearing (302) is supported by the support structure (303) rather than a nacelle or bedplate. A joint (304) is introduced on the rotor shaft (305), such that the rotor (301) and remaining nacelle assembly (306) can be separated. The nacelle assembly (306) may comprise the powertrain components (307), which may comprise the drivetrain components and the power electronics that require maintenance. The joint (304) may be a flanged joint, sliding connection, threaded spin collar arrangement, bolted connection, quick release or lock mechanisms, or any other appropriate connection between the two subsystems. The nacelle assembly (306) is mounted via the bedplate onto a rail system (308) on the support structure (303). In operation, the nacelle assembly (306) is held in position by connections (309). In Figure 3B it is shown that, during a maintenance or installation operation, or similar, the rotor shaft joint (304) and connections (309) can be disconnected, and the nacelle assembly (306) can be moved away along the tracks (308) using some actuation method (310), such as a remote-controlled motor (“track- bot”), winch system, motorised tracks, or other suitable actuation method. Access to the connection points may be provided by a simple nacelle cover that can be opened (by a hinged hatch door or similar) by a technician. In an alternative embodiment, the nacelle assembly (306) may be removed using a crane which is mounted on the rail system (308), instead of the nacelle assembly (306) being mounted directly to the rail system (308).

[0080] Referring to Figure 4 there is shown a schematic view of the integrated track system, both during movement of a nacelle assembly to the lift (4A) and when the nacelle assembly is contained within the lift (4B). Figure 4A shows that when a nacelle assembly (401) is required to be moved (for installation, maintenance, or other), the nacelle assembly (401) is disconnected from the rotor (402) and support structure (403), as described with regards to Figure 3. The nacelle assembly (401) is moved away on the track system (404), by an actuation system (405), such as a small “track-bot”, which is also mounted on the track system, a winch system, motorised tracks, or other suitable actuation method. The rotor (402) remains attached to the support structure (403), and solely the nacelle assembly (401) is moved along the tracks (404) to the tower (406) of the assembly. Figure 4B shows that the nacelle assembly (401) is then moved into the tower (406) and onto an internal lift system (407) which also contains tracks (408). The in-tower lift (407) may or may not include the ability to rotate about its vertical axis using a turntable (409). The lift (407) raises or lowers the nacelle assembly (401) to or from the ground.

[0081] Referring to Figure 5 there is shown a schematic view of the internal tower lift system at it’s base from a top-down view (5A); and where the components are moved into and out of the lift by a track system (5B), or by a service vehicle (5C). Figure 5A shows the nacelle assembly (501) at the base of the tower (502) having been returned to ground level by the lift system (503), where the lift system comprises tracks (504). The turntable (505) of the lift system (503) may rotate and position the nacelle assembly (501) so that it may be removed from the tower through an opening (506) in the base of the tower (502). Figure 5B shows the nacelle assembly (501) being removed from the tower (502) lift system (503) on a track system (507), and Figure 5C shows the nacelle assembly (501) being removed from the tower (502) onto a service vehicle (508).

[0082] Referring to Figure 6 there is shown a schematic view of the internal tower lift system at it’s base where maintenance equipment such as a lifting system is moved into and out of the lift by a track system (6A), or by a service vehicle (6B). For servicing the rotor nacelle assembly components, lifting or maintenance equipment (601) may be sent up to the relevant rotor components using the same track system as described with regards to Figure 4. The lifting equipment (601) may be a fixed, articulating, or telescopic crane arm that is able to move in 3-6 degrees of freedom, or other examples of rotor maintenance equipment. The lifting equipment (601) may also contain an in-built actuation system to move along the track system or may also use a “track-bot”, winch system, or other suitable actuation method. The lifting equipment dimensions (601) are such that it will be able to fit into the in-tower lift system and may service the rotor nacelle assembly, or its component parts, in situ without the nacelle assembly needing to be removed beforehand. Figure 6A shows the lifting / maintenance equipment (601) being introduced to the tower (602) lift system (603) through the opening at the base of the tower (604), on a track system (605), and Figure 6B shows the lifting / maintenance equipment (601) being introduced to the tower (602) lift system (603) through the opening at the base of the tower (604), using a service vehicle (606).

[0083] Referring to Figure 7, there is shown a schematic view of an external tower lift system from the front (7A) and from the side as it approaches the structural framework (7B). The figures show a schematic view of a support tower (701) with an external lift (702). The external lift

[0084] (702) is moved up (and down) the height of the support tower (701 ) and the associated support structure (703), which is attached to the support tower (701) by means of a vertical track system (704), which may be integrated into the tower. At the top part of the multi-rotor wind turbine assembly, where the support structure (703) is mounted to the support tower (701), the vertical track system (704) may be directly mounted to the support structure (703), rather than the support tower (701). In this case, there is a split present in the track system (704) to allow the top portion of the multi-rotor wind turbine assembly, which is the support structure

[0085] (703) to align with the predominant wind direction, and the lift system (702) is capable of traversing that gap. The lift (702) is moved about the track system (704) by means of an actuation system (705), which may consist of a winch system, or a counterweight system, or any other suitable apparatus. Whilst this figure shows an external lift, the skilled artisan would know that the lift could be internalised within the support tower (701) as described with regards to Figure 3 and Figure 4. The lift (702) may be used to transport objects (706), which may comprise component parts, such as a generator, sub-assemblies such as the complete drivetrain, or assemblies such as the nacelle assembly, or maintenance equipment, such as cranes. In Figure 7B, the lift (702) is shown approaching, or moving away from, the structural framework (703), which holds the nacelle assemblies (707).

[0086] Referring to Figure 8, there is shown a schematic view of a maintenance crane (801) performing a blade lift operation, in accordance with the invention. Support tower (802) holds a support structure (803). In this embodiment, the support structure (803) is shown comprising a structure mounted to the tower (803a) which supports a framework (803b). The support structure (803) contains a track system (804), which is used to transport maintenance systems, such as the maintenance crane (801) from the support tower (802) lift system (805) to a nacelle assembly location. In Figure 8, the maintenance crane (801) is shown lifting a rotor blade (806) into position at a rotor (807), to assemble a rotor nacelle assembly with three blades.

[0087] Referring to Figure 9, there is shown a multi-rotor wind turbine assembly in accordance with the invention where RNA maintenance is being carried out, from the front (9A) and another angle (9B). In Figure 9A, the multi-rotor wind turbine assembly (900) comprises a support tower (901), which holds a support structure (902). Integrated within the support structure (902) is a track system (903) which enables the maintenance equipment (904) to access the rotor nacelle assemblies (905), which comprise the wind turbines. The maintenance equipment (904) may be introduced to the track system (903) from ground level, by means of the tower lift (906), which moves up and down the support tower (901) and support structure (902). In Figure 9B, there is shown the multi-rotor wind turbine assembly in accordance with the invention of Figure 9A, where RNA maintenance is being carried out, but from a different angle, which more clearly shows the track system (903), which is integrated into the support structure (902), and allows maintenance equipment (904) to easily reach the rotor nacelle assembly (905). Figure 9B also shows how the tower lift (906) is able to move up and down the support tower (901), by means of a vertical track system (907).

[0088] Referring to Figure 10, there is shown a multi-rotor wind turbine assembly in accordance with the invention where nacelle assembly maintenance and / or installation is being carried out, from the rear (10A) and another angle (10B). In Figure 10A, maintenance crane (1001) is shown lifting a nacelle assembly generator (1002) into / out of position within the rotor nacelle assembly (1003). The crane (1001) is shown as being attached to a base plate (1004), which in turn is mounted on the track system (1005), which is mounted onto the structural framework (1006). The base plate (1004) can serve as a location for storing or holding components and / or further maintenance equipment. In Figure 10B, the crane (1001) is shown performing a maintenance operation in which the generator (1002) is being removed or installed from or into the nacelle bedplate (1007). Prior to installation or following removal, the generator (1002) would be stored and secured on the base plate (1004) for safe movement to and from the lift system in the support structure, and ultimately the ground. For simplicity, the rest of the support structure and the associated lift system are not shown.

Claims

CLAIMS1 . A system for the installation, assembly, removal and / or maintenance of a component of a multi-rotor wind turbine assembly, the system comprising an integrated track extending between an operational site of the component and a transitional site of the component.

2. A system according to claim 1 wherein the operational and / or transitional sites occupy an elevated position with respect to the surface on which the assembly is mounted.

3. A system according to claim 1 or claim 2, wherein the multi-rotor wind turbine assembly comprises a support tower and a structural framework extending laterally from the support tower.

4. A system according to claim 3, wherein the transitional site of the component is at or towards the support tower and the operational site of the component is laterally remote from the support tower.

5. A system according to claim 3 or claim 4, wherein the integrated track extends along a structural member of the structural framework.

6. A system according to any one of claims 3 to 5, wherein the integrated track extends substantially perpendicularly with respect to the support tower.

7. A system according to any one of claims 3 to 6, wherein in association with the support tower of the multi-rotor wind turbine assembly there is provided a lift system by which components can be lowered from the track system to ground level, and / or raised from ground level to the track system.

8. A system according to claim 7 wherein the lift system comprises its own integrated track which forms an extension of the assembly track system when at the elevated position.

9. A system according to claim 7 or claim 8, wherein the lift system can rotate about its vertical axis.

10. A system according to any one of claims 7 to 9 wherein the lift is external to the support tower, and components for installation or removal are introduced to the lift system by a service vehicle or a further track system at ground level.11 . A system according to any of claims 7 to 9, wherein the lift is contained at least partly within the support tower, and components for installation or removal are introduced to the lift system through an opening at the base of the tower; optionally wherein this is carried out by a service vehicle or a further track system at ground level.

12. A system according to claim 1 or claim 2, wherein the multi-rotor wind turbine assembly comprises a support platform and a structural framework extending from the support platform.

13. A system according to any of claims 1 to 12, wherein lifting and / or maintenance equipment is provided in association with the track system.

14. A system according to claim 13, wherein the equipment comprises an articulating and / or telescopic crane arm that is able to move in at least about 3-6 degrees of freedom.

15. A system according to any one of claims 1 to 14, wherein the integrated track comprises one or more rails.

16. A system according to any one of claims 1 to 15, wherein the component comprises a rotor-nacelle assembly or a component part thereof.

17. A system according to any one of claims 1 to 16, wherein the component comprises means for its moveable mounting on the track.

18. A system according to any one of claims 1 to 17 adapted to transport the component along the track from the operational site to the transitional site (in a removal or maintenance procedure) and / or from the transitional site to the operational site (in an installation or assembly procedure).

19. A system according to any one of claims 1 to 18, wherein the multi-rotor wind turbine assembly comprises a moveable element cooperating with a mechanical transmissionmeans, generator means and an electrical power transmission means using a rotor shaft.

20. A system according to claim 19, wherein there is a joint on the rotor shaft, such that the rotor and any associated nacelle assembly may be separated from one another, optionally wherein the joint is a flanged joint, sliding connection, threaded spin collar arrangement, bolted connection, quick release / lock mechanisms, or another appropriate connection mechanism.21 . A system according to any of claims 1 to 20, wherein the component is movable along the track system using an actuation method, such as a remote-controlled motor, winch system, or motorised track.

22. A process for the installation and / or removal of multi-rotor wind turbine assembly components wherein, during installation, the process comprises: introducing the component to a lift system at ground level; raising the component from ground level to the level of the assembly using the lift system; moving the component along a track system to the assembly; and connecting the component to the assembly, such that the component is installed; and during removal, the process comprises: disconnecting the component from the assembly; moving the component along the track system to the lift system; lowering the component to ground level from the level of the assembly using the lift system; and removing the component from the lift system at ground level, such that the component is removed.

23. A process for the in-situ maintenance of modular renewable energy generation assembly components, comprising: introducing maintenance equipment to the lift system at ground level; raising the maintenance equipment to the level of the component; moving the maintenance equipment along the track system to the component; carrying out maintenance of the component in situ; and following completion of maintenance of the component, returning the equipment to ground level by means of the track system and the lift system.

24. A process according to claim 22 or claim 23 wherein the track system comprises the integrated track of the system of any one of claims 1 to 21.

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