Drone access system for wind turbine

Abstract

UAV Wind Turbine Access System. Aspects of the present invention relate to a wind turbine system comprising a tower and a nacelle mounted to the tower, further comprising an access opening configured to permit access to an interior space of the wind turbine system, wherein the access opening has a computer-controlled access hatch, wherein the computer-controlled access hatch comprises: a movable hatch closure element that covers a hatch opening, an access control system configured to control the closure element between open and closed positions, wherein the controller is configured to be responsive to an access request message. A method of retrofitting the system and a method of allowing access to the wind turbine are also provided.

Description

[0001] DRONE ACCESS SYSTEM FOR WIND TURBINE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a controlled access system for a wind turbine. Aspects of the invention relate to a wind turbine system incorporating the invention, a method of accessing a wind turbine and a method of retrofitting a wind turbine.

[0004] BACKGROUND

[0005] Wind turbines for power generation are well known in the art. In a common arrangement, a nacelle is mounted on a tower, with a multi-bladed rotor being mounted on the nacelle.

[0006] Wind turbines require routine maintenance and inspection to minimise downtime and maintain efficient operation. Typically, in the interior of the wind turbine is accessed so that structural elements such as the tower and its bolted joints, electro-mechanical systems such as the yaw drive, main gearbox and generator, and the interior of the hub and the blades can be inspected, so that appropriate maintenance can be carried out if required.

[0007] The use of drones or unmanned vehicles is becoming increasingly popular with wind turbine maintenance and inspection. In some examples drones are used to take still or video images of the wind turbine structure and components, and in other examples drones may deliver spare components or consumables for maintenance operations. In further examples, drones may conduct maintenance operations themselves. Such drones may be controlled remotely or autonomously.

[0008] A problem encountered with the use of drones in the maintenance and inspection of wind turbines is how the drones gain access to the interior of the wind turbine. Oftentimes, the wind turbine access point may be locked, requiring personnel present to open the wind turbine access point so that the drone may access the interior. Furthermore, there is a health and safety risk of operating drones in close proximity to personnel, particularly inside a wind turbine.

[0009] It is against this background that the present invention has been devised. SUMMARY OF THE INVENTION

[0010] According to an aspect of the present invention there is provided a wind turbine system comprising a tower and a nacelle mounted to the tower, further comprising an access opening configured to permit access to an interior space of the wind turbine system, wherein the access opening has a computer-controlled access hatch, wherein the computer-controlled access hatch comprises: a movable hatch closure element that covers a hatch opening, an access control system configured to control the closure element between open and closed positions, wherein the controller is configured to be responsive to an access request message.

[0011] The wind turbine system may further comprise a remote-control station, wherein the remote-control station is configured to transmit the access request message in response to the initiation of a maintenance mode.

[0012] The wind turbine system may further comprise a remote transmission module, wherein the access request message is transmitted by the remote transmission module. The access control system may be configured to be responsive to access messages that are transmitted by the remote transmission module from a position inside or outside of the wind turbine system.

[0013] The remote transmission module may form part of a vehicle, which may be an autonomous vehicle. The autonomous vehicle may comprise propulsion means configured for airborne locomotion of the autonomous vehicle.

[0014] The access control system may be configured to be responsive to the access message which is in a wireless electronic, optical or audio formats.

[0015] The wind turbine system may further comprise a notification system which is operably connected to the access control system, wherein the access control system is configured to cause a notification signal to be emitted by the notification system. The notification signal may be caused to be emitted when the access control system determines that a maintenance mode is active. Else, the notification signal may be caused to be emitted when the controller determines that the remote transmission module is inside the wind turbine system and that a maintenance mode is active. The computer-controlled access hatch may form a part of an existing personnel door, the personnel door comprising a closure which matches the shape of a corresponding structural door opening. The door closure is manually operated.

[0016] The computer-controlled access hatch opening may have an area that is less than 50% of the area of the structural tower door opening, and optionally less than 25%.

[0017] The wind turbine system may further comprise a docking system within the wind turbine system configured to dock the autonomous vehicle wherein the docking system is configured to charge the autonomous vehicle. The autonomous vehicle may be selectively armed or disarmed while docked at the docking station.

[0018] According to another aspect of the present invention there is provided a method for accessing a wind turbine system, comprising: manoeuvring a vehicle towards a computer- controlled access control hatch that is controlled by an access control system; transmitting, at the vehicle, an access request message to the access control system, verifying, at the access control system, that the access request message is an authorised request message; controlling, at the access control system, the computer-controlled access control hatch to permit passage of the vehicle through the computer-controlled access control hatch.

[0019] According to a further aspect of the present invention there is provided a method for retrofitting a personnel door of a wind turbine, the personnel door having a closure panel that corresponds to a shape of a corresponding access opening, the method comprising: removing the closure panel from the personnel door, fixing a replacement closure panel into the personnel door, wherein the replacement closure panel comprises a computer- controlled access control hatch having a movable hatch closure element that covers a hatch opening.

[0020] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0023] Figure 1 shows a front view of a wind turbine to which the examples of the invention may apply;

[0024] Figure 2 is a schematic diagram of an exemplary unmanned vehicle system, such as a drone, for use in the examples of the invention;

[0025] Figure 3 is a schematic diagram of a control station for use with the unmanned vehicle system of Figure 2;

[0026] Figure 4 is a schematic diagram of an access control system of a wind turbine;

[0027] Figure 5 is a schematic diagram of communication data flows between various systems of the examples of the invention;

[0028] Figure 6 is a schematic diagram of how a drone might use an elevator path of a wind turbine to ascend inside the wind turbine tower;

[0029] Figure 7 shows a door of the wind turbine having an access control hatch in a closed state;

[0030] Figure 8 shows the door of Figure 7 with the access control hatch in an open state;

[0031] Figure 9 shows an example of an access control hatch fitted with a ramp;

[0032] Figure 10 shows a nacelle with an access control hatch; and

[0033] Figure 11 is a schematic diagram showing access control hatches at the internal structural interfaces of the wind turbine. DETAILED DESCRIPTION

[0034] Examples of the invention provide a wind turbine system comprising a computer-controlled access hatch installed therein. The computer-controlled access hatch has an access closure element, e.g., a hatch, a cover or a door, that covers a hatch opening, and a controller configured to open and close the access hatch upon receipt of a valid access request message.

[0035] The access hatch is intended to be suitable for drones, although this aspect is not intended to be limiting as the access hatch could grant access to personnel or other types of vehicles. For brevity, this discussion will refer to a ‘drone’ as any type of unmanned vehicle. The drone may be an air vehicle such as a relatively small-scale rotorcraft such as a multirotor, for example a tricopter, quadcopter, pentacopter, hexacopter, or octocopter, or else, it may be a ground-based vehicle with wheels, tracks or legs. In the case of the latter, the drone may be capable of travel on substantially vertical surfaces such as a wall of a wind turbine tower, for example. Examples of any of the abovementioned drones are known in the art and discussion of specific configurations of drone locomotion is outside the scope of this document.

[0036] The examples of the invention provide a novel approach for improving access for drones tasked with conducting inspection and / or maintenance operations for wind turbines. Figure 1 shows a wind turbine system 10. The wind turbine 10 is a horizontal axis wind turbine (HAWT) and comprises a nacelle 12 on top of a tower 14. The nacelle 12 houses the mechanical and electrical systems of the wind turbine 10. Protruding from a front of the nacelle 12 is a rotor hub 16 which supports the blades 18 of the wind turbine 12. An interior of the nacelle 12 is accessible from an interior of the tower 14. Likewise, the interior of the rotor hub 16 is accessible from the nacelle 12. The interior of the rotor hub 16 provides access to the interior of the blades 18, which are substantially hollow as is conventional. Conventionally, the tower is accessed through personnel door 20 at the base of the tower 14. The personnel door 20 comprises an access opening that allows access between and interior and an exterior of the wind turbine 10. The access opening is closed by a door panel of corresponding size and shape. The interior of the tower may feature a stairs, ladder or elevator to help personnel ascend to the top of the tower 14 and into the nacelle 12.

[0037] Figure 2 illustrates a system diagram of a typical architecture of a drone 100 which may be used in the implementation of the embodiments of the invention. In overview, the drone is a vehicle that includes: a control system 102, one or more propulsion units 104, a power system 106, a communication system 108, a sensor suite 110, mission planning system 112 and a navigation system 114. The drone 100 may be operated in conjunction with a remote computer system, hereinafter referred to as the ‘remote control station’ 300, which will be described in more detail later with reference to Figure 4.

[0038] The control system 102 is the main computing unit that controls the movement of the drone 100 by controlling the propulsion units 104 based on inputs from the sensor suite 110 and navigation system 114. The control system 102 may implement remote control movement based on received control inputs from the remote-control station 300, autonomous movement, based on its internal mission planning algorithms, or semi-autonomous movement, in which a blend of on-board mission planning and control station-based direction are used. The main responsibility of the control system 102 is as a lower layer controller which is responsible for positional control of the drone, attitude control in the case of a flying drone, and velocity control based on remote control actions or based on self-generated movement directions. The control system 102 comprises a suitable processing environment having a processor 116 and a memory 118 with associated onboard communications functionality, such as a data bus, so it is able to communicate with other on-board systems.

[0039] To directly control the movement profile the control system 102 communicates with the one or more propulsion units 104. Four propulsion units 104 are shown here, as would be consistent with the drone system 100 being having a multiple rotors or propulsion units depending on the type of drone. However, more or fewer propulsion units 104 are also appropriate. For example, an autonomous helicopter may have a single propulsion unit 104, but heavy lift flying drones may have six or eight propulsion units 104. The propulsion units 104 may be any suitable units for providing controllable movement for the drone, and may be electric motors driving suitable rotor blades, wheels tracks or legs. However, the propulsion units may also be gas turbines or internal combustion engines, for example.

[0040] The on-board power system is selected to be suitable for the propulsion units. For example, for electric motors the on-board power system may be a battery pack, a fuel cell, or even an external power plug so as to receive electrical power from an external source. Conversely, the power system could be an on-board fuel tank in the event that the propulsion units are gas-turbines or ICEs. The communication system 108 provides the means to send and receive data to and from systems that are external to the drone. For example, the drone 100 may send telemetry data to the remote-control station 300, and may send positional, attitude and velocity data to other drones operating in the area, either as part of a drone swarm or operated independently. The communication system 108 may also receive data from external systems and in this context it may receive remote control commands from the remotecontrol station 300 if the drone 100 is operated in remote control mode. Else, it may download mission data from the remote-control station 300. The communication system 108 may also permit incoming and outgoing communication with other drones so that movement paths and mission objectives can be coordinated with them to achieve a collective goal. The communication system 108 may direct signals by any means known in the art including, but not limited to, cellular or other phone-based networks, over remotecontrol radio frequency links, UHF or L-band frequency links, microwave frequency links, audio, optical systems such as infra-red or ultraviolet or other appropriate datalinks, networks, or communication paths.

[0041] The communication system 108 is configured to communicate with access control systems 200 of one or more wind turbine it has been tasked with inspecting or maintaining. An example of an access control system 200 is discussed below and shown in Figure 3. For example, the drone 100 may communicate its position, velocity, or direction such that the access control system 200 can predict when to grant access to the drone 100 to enter the wind turbine 10. In an embodiment, the drone 100 may simply issue an access request message to the access control system 200 to gain access to the wind turbine 10.

[0042] The sensor suite 110 is operably connected to the control system 102 and provides appropriate sensor data to assist with the operation of the drone 100. For example, the sensor suite 110 may comprise proximity detectors, a satellite-based positioning system, including for example differential GPS, RTK-GNSS, PPP-GNSS or any other local positioning system set up for positioning control, optical still and video cameras for carrying out inspection and guidance tasks, inertial navigation systems to name a few examples. Typically, such a sensor suite 110 would be adaptable to carry more or fewer sensors as required for a particular task. Note that in this context the GPS unit may receive signals directly from satellites to fix the position of the drone 100, although another option would be to implement a differential GPS system (known in the art) which receives signals from a remote differential GPS beacon in order to provide a higher positional accuracy compared to direct GPS. Note that a GPS unit 120 is shown here as integral with the navigation system 114.

[0043] Mission planning system 112 provides a link to the remote-control station 300 to store missions that have been generated on it and to which the drone 100 follows in use. The mission planning system may include suitable memory storage and algorithms to store, provide and generate on the fly appropriate mission objectives, waypoints, operational envelopes and so on.

[0044] Navigation system 114 provides control inputs to the movement control system regarding path following based on input from GPS data from the GPS Unit 120.

[0045] The payload connection system 122 may be configured to hold or support a payload, such as a parts or tools for maintenance operations. Such a payload may be held in a fixed position relative to a main body of the drone 100 or, in other embodiments, the payload may be suspended from the drone by a flexible line, tether or sling or on a trailer towed by the drone 100. To provide flexibility over the type of payload that is carried, the payload connection system 122 may be configured to releasably attach the payload to the drone 100, such that the payload may be removed or replaced after use.

[0046] It should be appreciated that the above description of a drone 100 system is intended as merely an example of the main components of a remote controlled and / or autonomous vehicle and that other components may also be included in a typical system. In general, it should be noted that drones 100 for use in the embodiments of the invention are known and are able to perform in remote control modes, semi- and fully autonomous modes, and are able to carry out manoeuvres in a coordinated fashion in fixed positional relationship with other drones 100.

[0047] The combination of the control system 102 the communication system 108 and GPS unit 120 may be disposed in a remote transmission module which is separate to a drone 100. For example, the remote transmission module may be a discrete component for attachment to a drone, vehicle or carried on a person which is operable to relay global positional data of the module to either or both the access control systems 200 of one or more wind turbines 10 scheduled for inspection or maintenance or the remote control station 300. The remote transmission module allows for drones, vehicles or personnel without communication capability or compatibility to communicate with the access control system 200 or the remote-control station 300.

[0048] Having described the functional components of the drone 100, discussion will now turn to the access control system 200 of the wind turbine 10. Figure 3 illustrates a system diagram of an example architecture of the access control system 200 which may be used in the implementation of the embodiments of the invention. In overview, the access control system 200 features a controller 202, a communications system 208, a power input 210, and at least one motor unit 212 for actuating at least one access hatch.

[0049] The controller 202 is the main computing unit that processes signals based on inputs from the communications system 208 to establish whether to grant access, i.e. , open the hatch, to the interior of the wind turbine 10 or not.

[0050] The controller 202 may receive communications inputs from the remote-control station 300. The main responsibility of the controller 202 is to establish whether a signal received by the communications system 208 is a legitimate access request or not. The controller 202 comprises a suitable processing environment having a processor 204 and a memory 206 with associated on-board communications functionality, such as a data bus, so it is able to communicate with other systems of the access control system 200.

[0051] As has been discussed above, the access control system 200 may be communicated with by the drone 100, or the remote-control station associated with the drone 100. A system schematic of the remote-control station 300 as shown in Figure 4. The remote-control station 300 provides a control hub for one or more drones 100 as described above and is suitably equipped with a computing platform 302 having an appropriate processing module 304 and memory storage 306. The computing platform 302 implements a suitable control station software package 308 to provide appropriate control station facilities for controlling and coordinating the drone 100, together with other drones 100 if necessary. For example, the software package 308 may include telemetry feeds, status information updates, first person visual (FPV) feeds, mission planning interfaces and algorithms and so on. A user interface 310 is provided to enable to a user / operator to view data relating to the drone 100 and to input control and parameter data into the remote-control station 300. The user interface 310 may comprise a display screen, audio output, a user input means such as a keyboard, joystick, mouse, on-screen buttons or a combination of these. The remote-control station 300 also has a communications system 312 in order to send data to and receive data from the drone 100 or the access control system 200. The remotecontrol station 300 could be a remote system that is mounted in a maintenance vehicle, such as a type of ship known as a Service Operations Vessel, for example.

[0052] Figure 5 is a schematic showing the intercommunication between the drone(s) 100, the access control system(s) 200 and the remote-control station 300. It will be apparent to the reader that the exemplary embodiment is a three-way communication between the drone(s) 100, the access control system(s) 200 and the remote-control station 300, although this is not intended to be limiting. The remote-control station could communicate with the drone(s) 100 and the access control system(s) 200 independently or the communication may be executed in a daisy chain where the remote-control station 300 communicates with the drone(s) 100 which, in turn, communicate with the access control system(s) 200.

[0053] Communication strategies may include, for example, microchip with communication by RFID, Bluetooth, NFC, Wi-Fi, UWB or other wireless communication formats. In embodiments, the communication may be in an audio or optical format. The remote-control station 300 or the access control system 200 may communicate with the drone 100 to ensure the drone 100 is at the correct entrance, for example if there is no GPS module on the drone 100 or if the wind turbine in question has multiple access openings and the GPS resolution is insufficient to distinguish the precise location of the drone 100 relative to the relevant access opening. For example, the drone 100 may use an optical sensor to scan a QR code on or near the access opening to verify the location.

[0054] The signals transmitted between the drone(s) 100, the access control system(s) 200 and the remote-control station 300 should be encrypted for cybersecurity reasons, i.e., to prevent unauthorised access to wind turbines or hacking of the drone(s) 100.

[0055] The remote-control station 300 communicates to the access control system(s) 200 of the wind turbine(s) 10 set to undergo inspection or maintenance. For example, the remotecontrol station 300 may communicate with the access control system(s) with a message to enter a ‘maintenance mode’. The access control system 200 of a wind turbine 10 will then communicate with the other systems of the wind turbine 10 to enter the maintenance mode. An example of action taken for a wind turbine 10 to enter into a maintenance mode may be: ensuring the nacelle 12 yaws head to wind; reducing the rotational speed of the rotor hub 16 to a stop state by pitching the blades 18 to zero degrees and applying a brake to the rotor hub 16; and setting the access control system 200 into a state in which it is ready to receive a communication to grant access to an incoming drone 100. The maintenance mode may also set personnel doors 20 of the wind turbine to lock, to prevent personnel from entering the wind turbine 10 which is about to grant entry to a drone 100. Additionally, if the wind turbine 10 comprises an elevator, i.e. , a lift or a hoist, the elevator can either ascend to the top or descend to the bottom of the tower 14 so that the drone 100 can utilise vacant elevator path 22 to ascend the tower 14 as demonstrated in Figure 6.

[0056] Once the access control system 200, and therefore the wind turbine 10, is in the maintenance mode, the access control system 200 could take into account the position and heading of a drone 100 dispatched for maintenance operations on the wind turbine 10. The access control system 200 receives signals from either the drone 100 or the remote-control station to open in a timely fashion as the drone 100 approaches to allow the drone 100 access to the wind turbine interior. Likewise, either the drone or the remotecontrol station 300 may signal the access control system 200 to close either after the drone 100 has entered the wind turbine interior or after the drone 100 has left the wind turbine 10.

[0057] In embodiments, a drone 100 may enter the wind turbine 10 whilst it is still operational for interior inspection of the turbine 10. In this case, the wind turbine 10 may continue normal energy production as hazards to personnel health and safety are nil if there are no personnel on site. In this situation, a maintenance mode could include setting the access control system 200 into a state in which it is ready to receive a communication to grant access to an incoming drone and locking the personnel door to prevent personnel from entering the wind turbine 10.

[0058] Figures 7 and 8 show an example of an automated access hatch 400 with a moveable closure element 404 in non-structural portion of wind turbine tower 14. Figure 7 shows the moveable closure element 404 in a closed position and Figure 8 shows the moveable closure element 404 an open position. In this example, the automated access hatch 400 is integrated into personnel door 402 of the wind turbine 10. Beneficially, integrating the automated access hatch 400 into a personnel door 402 means that the overall structure of the tower 14 is unaffected upon installation of the automated access hatch 400. This makes retrofitting the automated access hatch 400 in an existing personnel door 402 or providing a replacement personnel door 402 with the automated access hatch 400 already installed quite straightforward. The automated access hatch 400 may have an area that is less than 50% of the area of the personnel door 402 opening area, and optionally less than 25% of the personnel door 402 opening area.

[0059] The automated access hatch 400 may be above ground level or at ground level. For example, if the automated access hatch is above ground level, it would be accessed by either flying or climbing type drones 100. If the automated access hatch is at ground level, access is also granted to ground moving drones 100 such as wheeled, tracked or legged type drones 100.

[0060] Figure 9 shows an automated access hatch 500 at ground level or, in this particular example, at platform level for a wind turbine 10 positioned offshore. Oftentimes, a personnel hatch 502 features a step that may prove to be an obstacle to ground moving drones 100. To facilitate this, the automated access hatch may feature a deployable ramp 506 to allow the ground moving drone to navigate the step with ease. In a further embodiment, the moveable closure element 504 of the automated access hatch 500 may pivot downwards such that one end is on the ground or platform and the other end remains at the threshold of the hatch, the movable closure element 504 serving as an access ramp 506 for the drone 100.

[0061] Figure 9 also shows a flying drone 100A with a ground moving or climbing drone 100B as a payload. Using a flying drone 100A to deliver a ground moving or climbing drone 100B is an efficient way of moving ground moving or climbing drones 100B to wind turbines in otherwise difficult to access locations, for example in mountainous areas or offshore.

[0062] Figure 10 shows an embodiment of the invention where the automated access hatch 600 is disposed on the nacelle 12. A flying or climbing drone 100 may utilise the automated access hatch 600 to gain access into the nacelle 12 directly. Although the automated access control hatch 600 in Figure 10 is shown to be disposed on a top face of the nacelle, embodiments may position the access control hatch 600 on a side face or a rear face of the nacelle 12.

[0063] Figure 11 shows another embodiment where there are access control hatches 700A, 700B disposed internally in the wind turbine 10. For example, a first access control hatch 700A may control access between the nacelle 12 and the hub 16. Additionally, a second access control hatch 700B may control access between the tower 14 and the nacelle 12. Such access control hatches may be defined within access openings between interior spaces within the wind turbines, and in some instances may be disposed within existing door panels located within those access openings.

[0064] Beneficially, zoning or separating the spaces of the wind turbine interior in this way allows for a drone 100 to safely occupy and operate in one space within the wind turbine 10 and personnel may occupy a separate space of the same wind turbine while safely isolated from the operating drone 100. For example, a flying drone may enter the hub 16 through access control hatch 700A in order to inspect or maintain the hub 16 and the blades 18. Once the access control hatch 700A closes after the drone has gained access to the hub 16, personnel may enter the tower 14 and / or the nacelle 12 safely.

[0065] The access control system 200 may operate to lock personnel doors 20 of the wind turbine 10 while drone is inside to prevent personnel from entering the potentially hazardous environment of a drone operating in a confined space.

[0066] A notification system may be operable by the access control system 200. Such a notification system may comprise status indicators such as lights, an intercom or a siren. The notification system would serve to notify personnel in the wind turbine 10 or the surrounding area that the wind turbine is entering or has entered the maintenance mode, that hatch is about to open or close, that a drone is operating inside or that a drone is about to exit the wind turbine, for example.

[0067] An auxiliary use for the access control system 200 and any corresponding access control hatches present in the wind turbine 10 is opening the hatch in emergency situation for faster evacuation. In further embodiments, the access control system could be configured to allow third parties to deliver goods to the inside of the wind turbine 10 without a need for authorized personnel presence.

[0068] The wind turbine 10 may feature a dock within the wind turbine 10 configured to dock the drone 100. The docking system is configured to charge, communicate and / or transfer data with the drone 100. The dock could also serve to disarm or maintain the drone in a dormant state while it is docked. The active state of the drone 100 in the dock is controlled by the access control system 200 such that the drone is selectively armed or disarmed when personnel are permitted access to the wind turbine interior.

[0069] The inventive concept further contemplates a method for accessing a wind turbine tower, comprising: manoeuvring drone towards a computer-controlled access control hatch of the wind turbine, wherein the computer-controlled access control hatch that is controlled by a access control system; transmitting, at the drone, an access request message to the access control system, verifying, at the access control system, that the access request message is an authorised request message; controlling, at the access control system, the computer-controlled access control hatch to permit passage of the drone through the computer-controlled access control hatch.

[0070] The inventive concept also contemplates a method for retrofitting a personnel door 20 of a wind turbine 10, the personnel door having a closure panel that corresponds to a shape of a corresponding structural opening, the method comprising: removing the closure panel from the personnel door, fixing a replacement closure panel into the personnel door, wherein the replacement closure panel comprises an access control hatch having a movable hatch closure element that covers a hatch opening.

[0071] It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1. A wind turbine system (10) comprising a tower (14) and a nacelle (12) mounted to the tower (14), further comprising an access opening (20) configured to permit access to an interior space of the wind turbine system (10), wherein the access opening (20) has a computer-controlled access hatch (400), wherein the computer-controlled access hatch (400) comprises: a movable hatch closure element (404) that covers a hatch opening, an access control system (200) configured to control the closure element (404) between open and closed positions, wherein the controller (200) is configured to be responsive to an access request message.

2. The wind turbine system (10) of Claim 1 , further comprising a remote-control station (300), wherein the remote control station (300) is configured to transmit the access request message in response to the initiation of a maintenance mode.

3. The wind turbine system (10) of Claim 1 or Claim 2, further comprising a remote transmission module, wherein the access request message is transmitted by the remote transmission module.

4. The wind turbine system (10) of Claim 3, wherein the remote transmission module forms part of a vehicle (100).

5. The wind turbine system (10) of Claim 4, wherein the vehicle (100) is an autonomous vehicle.

6. The wind turbine system (10) of Claim 5, wherein the autonomous vehicle (100) comprises propulsion means configured for airborne locomotion of the autonomous vehicle (100).

7. The wind turbine system (10) of any one of the preceding claims, wherein the access control system (200) is configured to be responsive to the access message which is in a wireless electronic, optical or audio formats.

8. The wind turbine system (10) of any one of the preceding claims, when dependent on Claim 3, wherein the access control system (200) is configured to be responsive to access messages that are transmitted by the remote transmission module from a position inside the wind turbine system (10).

9. The wind turbine system (10) of any one of the preceding claims, when dependent on Claim 3, wherein the access control system (200) is configured to be responsive to access messages that are transmitted by the remote transmission module from a position outside of the wind turbine system (10).

10. The wind turbine system (10) of any one of the preceding claims, further com prising a notification system which is operably connected to the access control system (200), wherein the access control system (200) is configured to cause a notification signal to be emitted by the notification system.11 . The wind turbine system (10) of Claim 10, wherein the notification signal is caused to be emitted when the access control system (200) determines that a maintenance mode is active.

12. The wind turbine system (10) of Claim 11 , when dependent on Claim 3, wherein the notification signal is caused to be emitted when the controller determines that the remote transmission module is inside the wind turbine system (10) and that a maintenance mode is active.

13. The wind turbine system (10) of any one of the preceding claims, wherein the computer-controlled access hatch (400) forms part of an existing personnel door (20), the personnel door comprising a closure which matches the shape of a corresponding structural door opening.

14. The wind turbine system (10) of Claim 13, wherein the door closure is manually operated.

15. The wind turbine system (10) of any one of the preceding claims, when dependent on Claim 5 further comprising a docking system within the wind turbine system (10) configured to dock the autonomous vehicle (100) wherein the docking system is configured to charge the autonomous vehicle (100).

16. The wind turbine system of Claim 15, wherein the autonomous vehicle (100) is selectively armed or disarmed while docked at the docking station.

17. A method for accessing a wind turbine system (10), comprising: manoeuvring a vehicle (100) towards a computer-controlled access control hatch (400) that is controlled by an access control system (200); transmitting, at the vehicle (100), an access request message to the access control system (200), verifying, at the access control system (200), that the access request message is an authorised request message; controlling, at the access control system (200), the computer-controlled access control hatch (400) to permit passage of the vehicle through the computer-controlled access control hatch (400).

18. A method for retrofitting a personnel door (20) of a wind turbine, the personnel door (20) having a closure panel that corresponds to a shape of a corresponding structural opening, the method comprising: removing the closure panel from the personnel door (20), fixing a replacement closure panel into the personnel door (20), wherein the replacement closure panel comprises a computer-controlled access control hatch (400) having a movable hatch closure element (404) that covers a hatch opening.

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