Lift-on installation crane for an offshore energy platform

Abstract

The present disclosure relates to an installation and maintenance crane (1) and relevant methods, in which the installation and maintenance crane (1) comprises a base (3), wherein the base (3) includes at least one base member having an open section; at least two crane arms (2) connected to the base (3); and at least two crane alignment and connection members (5) disposed on, or in, the base (3); wherein one or more of the at least two crane alignment and connection members (5) are configured to operatively mate with a respective complimentary platform alignment and connection members (6) disposed on the offshore energy platform (8).

Description

[0001] Lift-On Installation Crane for an Offshore Energy Platform

[0002] Field

[0003] The present disclosure relates to an installation crane and, in particular, to a lift-on installation crane to install and / or maintain an offshore wind turbine on an offshore energy platform.

[0004] Background

[0005] As offshore wind turbine deployment increases and shallow water sites become scarcer, projects will venture into deeper waters. As this happens the type of offshore renewable energy platform used to mount offshore renewable energy devices, such as wind turbines, and the methods used to install the platforms and / or the renewable energy devices on the platforms will need to evolve.

[0006] Current installation methods for installing wind turbines in shallow water sites largely rely on the use of jack-up vessels. Jack-up installation vessels use their legs to lift the vessel above sea level. Standing firmly on the seabed, the vessels operate safely without being impacted by the waves and currents. Jack-up vessels are limited to operate in waters where their jack-up legs can reach the seabed. For offshore wind installations in deeper waters, jack-up vessels cannot be used. For installations in deeper waters, crane vessels can be used, but the sea conditions in which it is safe and possible to use them restrict their use. There is also a small number of crane vessels with sufficient lifting capacity, meaning that availability is limited and their use expensive.

[0007] To allow the economic installation of offshore renewable energy, e.g. wind turbine farms in deeper waters, a solution is desirable that enables the installation and maintenance of the offshore renewable energy device, e.g. wind turbine, on an offshore energy platform to be completed without significant sea state limitations and with widely available vessels.

[0008] Summary

[0009] According to a first aspect of the present disclosure there is provided an installation and maintenance crane for installation and maintenance of an offshore wind turbine on an offshore energy platform, comprising: a base, wherein the base includes at least one base member having an open section; at least two crane arms connected to the base; and at least two crane alignment and connection members disposed on, or in, the base; wherein one or more of the at least two crane alignment and connection members are configured to operatively mate with a respective complimentary platform alignment and connection members disposed on the offshore energy platform. In some embodiments, the open section of the at least one base member may permit installation and / or removal of the installation and maintenance crane with an offshore wind turbine installed on the offshore energy platform.

[0010] In some embodiments, the base may be formed of one base member and further comprises: two elongate structural members disposed substantially parallel to each other in a horizontal plane; and an interconnecting structural member disposed substantially perpendicularly between the two elongate structural members

[0011] In some embodiments, the crane alignment and connection members may be disposed on the elongate structural members and / or the interconnecting structural member.

[0012] In some embodiments, the base may be II shaped, H-shaped, or C shaped.

[0013] In some embodiments, the base may include an inner profile that is substantially matched, at least in part, to at least a portion of an outer profile of a tower section of the offshore wind turbine.

[0014] In some embodiments, the base may be formed by two or more base members.

[0015] In some embodiments, each base member may comprise at least one base connection operable to connect adjacent base components.

[0016] In some embodiments, the base formed by the two or more base components may be configured to surround an outer profile of a tower section of the offshore wind turbine.

[0017] In some embodiments, each of the two or more base members may be installed separately on to the offshore energy platform.

[0018] In some embodiments, each of the two or more base members may comprise at least one crane alignment and connection member.

[0019] In some embodiments, at least one of the two or more base members may comprise a crane arm.

[0020] In some embodiments, the at least two crane arms may be spaced apart to permit components of the offshore wind turbine to pass between the two crane arms.

[0021] In some embodiments, the at least two crane arms may be configured to operate cooperatively to lift a component of the offshore wind turbine, such that loads generated lifting the component are symmetrically distributed to the offshore energy platform.

[0022] In some embodiments, the crane arms may be telescopic crane arms and / or folding crane arms. In some embodiments, the at least two crane alignment and connection members may be formed as one or more indentations being shaped to receive complimentary shaped one or more protrusions of the respective platform alignment and connection members.

[0023] In some embodiments, the at least two crane alignment and connection members may be formed as one or more protrusions being shaped to engage with a complimentary shaped one or more indentations of the respective platform alignment and connection members.

[0024] In some embodiments, the indentations and the protrusions may be of a conical shape.

[0025] In some embodiments, the crane alignment and connection members may be configured to distribute loads from the installation and maintenance crane to a structure of the offshore energy platform.

[0026] In some embodiments, the installation and maintenance crane may be configured to be installed in one of a plurality of directions relative to the offshore energy platform based on the prevailing environmental conditions.

[0027] In some embodiments, the at least two crane arms may permit components of the offshore wind turbine to be lifted close to a main pivot point of the installation and maintenance crane without collision with the structure of the installation and maintenance crane.

[0028] In some embodiments, the installation and maintenance crane may have a transportation and installation configuration in which the at least one crane arm is docked with the base.

[0029] In some embodiments, the installation and maintenance crane may be operably configured to move one or more of the offshore wind turbine components in one or more combined hoists or in a single hoist, wherein the components include a tower segment, a nacelle, a generator, a hub, and a blade.

[0030] In some embodiments, a relative motion between an offshore wind turbine component on a component supply vessel and the offshore energy platform mounted installation and maintenance crane may be minimised by a motion compensated platform on the component supply vessel.

[0031] In some embodiments, the installation and maintenance crane may further comprise a wind turbine blade installation tool attachment, the wind turbine blade installation tool attachment comprising: one or more blade grips to grip a wind turbine blade; a horizontal-to- vertical and / or vertical-to-horizontal motor pivot system, configured to rotate a wind turbine blade; and a pitch motor pivot system, configured to control a pitch of the wind turbine blade.

[0032] According to a second aspect of the present disclosure there is provided an offshore energy platform comprising: at least two platform alignment and connection members disposed on, or in, an upper surface of the offshore energy platform; wherein the at least two platform alignment and connection members are configured to operatively mate with a respective complimentary crane alignment and connection members disposed on, or in, an installation and maintenance crane according to any one of the features of the first aspect.

[0033] In some embodiments, the offshore energy platform may be formed of a truss structure and the at least two platform alignment and connection members are formed in, or on, each chord of the truss structure.

[0034] According to a third aspect of the present disclosure there is provided a method of installing an installation and maintenance crane according to any one of the features of the first aspect on to an offshore energy platform, the method comprising: lifting the base, using a vessel crane, from a vessel on to the offshore energy platform; installing the base by aligning and engaging the crane alignment and connection members disposed on, or in, the base with corresponding platform alignment and connection members disposed on the offshore energy platform; and disengaging the vessel crane.

[0035] In some embodiments, the base may be formed of two or more base members and the method may further comprise: lifting and installing each base member independently; and connecting each of the two or more base members to form the base.

[0036] According to a fourth aspect of the present disclosure there is provided a method of removing an installation and maintenance crane according to any one of the features of the first aspect from an offshore energy platform, the method comprising: lifting the base, using the vessel crane, from the offshore energy platform on to the vessel.

[0037] In some embodiments, the base may be formed of two or more base members and the method may further comprise: lifting each base member independently on to the vessel.

[0038] According to a fifth aspect of the present disclosure there is provided a method of operating an installation and maintenance crane according to any one of the features of the first aspect on to an offshore energy platform, the method comprising: lifting, by the installation and maintenance crane, a component of the offshore wind turbine from a supply vessel; and installing the component of the offshore wind turbine onto the offshore energy platform. It will be appreciated that any features described herein as being suitable for incorporation into one or more aspects or embodiments of the present disclosure are intended to be generalizable across any and all aspects and embodiments of the present disclosure. Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claims.

[0039] Drawings

[0040] Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0041] Figure 1A shows a side view of an energy platform mounted crane on a floating platform according to one or more embodiments of the present disclosure.

[0042] Figure 1B shows a front view of an energy platform mounted crane on a floating platform according to one or more embodiments of the present disclosure.

[0043] Figure 1C shows a plan view of an energy platform mounted crane on a floating platform according to one or more embodiments of the present disclosure.

[0044] Figure 1D shows a side view of an energy platform mounted crane on a floating platform with a wind turbine installed according to one or more embodiments of the present disclosure.

[0045] Figure 1E shows a front view of an energy platform mounted crane on a floating platform with a wind turbine installed according to one or more embodiments of the present disclosure.

[0046] Figure 1F shows a plan view of an energy platform mounted crane on a floating platform with a wind turbine installed according to one or more embodiments of the present disclosure.

[0047] Figures 2A and 2B show a side view of an energy platform mounted crane on a seabed supported platform with and without a wind turbine installed respectively, according to one or more embodiments of the present disclosure.

[0048] Figures 3A and 3B show a side view of an energy platform mounted crane on a truss structure platform with and without a wind turbine installed respectively, according to one or more embodiments of the present disclosure. Figure 4 shows crane alignment features and platform alignment features according to one or more embodiments of the present disclosure.

[0049] Figure 5 shows crane alignment features and platform alignment features on a truss structure platform according to one or more embodiments of the present disclosure.

[0050] Figure 6A shows a crane wind turbine blade installation tool holding a wind turbine blade horizontally according to one or more embodiments of the present disclosure.

[0051] Figure 6B shows a crane wind turbine blade installation tool holding a wind turbine blade vertically according to one or more embodiments of the present disclosure.

[0052] Figure 6C shows a side view of a crane wind turbine blade installation tool holding a wind turbine blade vertically according to one or more embodiments of the present disclosure.

[0053] Figures 7A to 7F show a crane being lifted onto an energy platform and prepared for a wind turbine generator installation onto the energy platform according to one or more embodiments of the present disclosure.

[0054] Figures 8A to 8E show an energy platform mounted crane installing wind turbine generator support tower sections according to one or more embodiments of the present disclosure.

[0055] Figure 9 shows a wind turbine generator nacelle being lifted into place by the energy platform mounted crane according to one or more embodiments of the present disclosure.

[0056] Figures 10A to 10D show an energy platform mounted crane installing wind turbine generator blades using a wind turbine generator blade installation tool according to one or more embodiments of the present disclosure.

[0057] Figure 11 shows the energy platform mounted crane being lifted off the energy platform after a wind turbine generator installation is complete according to one or more embodiments of the present disclosure.

[0058] Figure 12 shows a crane supply vessel departing the energy platform with the energy platform mounted crane according to one or more embodiments of the present disclosure.

[0059] Figure 13A shows a plan view of one crane arm of an energy platform mounted crane on a floating platform according to one or more embodiments of the present disclosure.

[0060] Figure 13B shows a plan view of an energy platform mounted crane on a floating platform according to one or more embodiments of the present disclosure.

[0061] Description The Applicants have recognised that there is an opportunity for new and improved equipment, e.g. an installation and maintenance crane or cranes, an offshore renewable energy platform to mount the installation and maintenance crane or cranes, and methods for the installation of offshore renewable energy devices, such as wind turbines, on offshore renewable energy platforms that can be co-developed alongside the design and development of the offshore renewable energy platforms, to enable a faster, safer, more weather tolerant installation process that is more economically viable.

[0062] Thus, in embodiments, this patent disclosure describes installation and maintenance cranes that can be securely mounted upon, or attached to, an offshore energy platform. The installation and maintenance cranes can be removably installed on the offshore energy platform by a suitable crane vessel, without requiring specialised vessels which typically incur significantly higher costs and have limited availability. The offshore energy platform can therefore provide a stable foundation for the installation and maintenance cranes, and once installed on the offshore energy platform, the installation and maintenance cranes can advantageously be utilised to provide a safe and economic renewable energy device installation onto the energy platform without significant sea state limitations. The installation and maintenance cranes may also be used to conduct any lifting required for heavy maintenance operations of the offshore wind turbine, again without significant sea state limitations. Thus, the installation and maintenance cranes can be removably mounted on the offshore energy platform for the purposes of installation and / or maintenance, wherein the installation and maintenance cranes can be removed once the installation and / or maintenance has been completed.

[0063] The installation and maintenance cranes may be designed to be lifted onto the offshore energy platform and effectively integrated into the structure of the offshore energy platform such that they can be used for the installation and maintenance of tan offshore wind turbine, to be mounted on, or currently mounted on, the offshore energy platform.

[0064] With reference to the accompanying drawings, exemplary embodiments of the installation and maintenance cranes will be described and, in the following embodiments, will be referred to as a crane for the installation and maintenance of an offshore wind turbine on an offshore energy platform.

[0065] In some embodiments described below, the crane is formed with a single base member that comprises an open section to enable the crane to be installed on and / or removed from the offshore renewable energy platform whilst at least one component of the offshore wind turbine (e.g. tower sections ) is mounted on, or being installed on, the offshore energy platform. In other embodiments described below, the crane base is formed of two or more base members to enable the separate crane base members to be lifted and installed on the offshore energy platform, which can be advantageous to allow the different base members to be installed from different sides or locations around the offshore energy platform in more challenging environmental conditions, e.g. wind or wave conditions, at the time of installation of the crane. Each of the two or more base members may include an open section, wherein the combination of the two or more base members may form a base with an open section or a base that wraps around, or surrounds, the offshore wind turbine tower section when mounted on the offshore energy platform.

[0066] In all embodiments, the crane may include one crane arm, two crane arms, three crane arms, and so on, mounted or provided on the base as required in order to install, or maintain, a particular offshore wind turbine. In preferable embodiments, two crane arms are provided on the base, wherein the two crane arms are spaced apart to permit components, or at least some components, of the offshore wind turbine to pass between the two crane arms, for example the tower sections, or segments of the offshore wind turbine. The crane arms may be symmetrically positioned either side of the area in which the tower sections of the offshore wind turbine are to be installed, such that the loads generated by lifting, or hoisting, the components of the offshore wind turbine are symmetrically distributed to the offshore energy platform via the alignment and connection members.

[0067] As will be appreciated, the advantages of the present disclosure primarily relate to the ability to be able to install the crane onto an offshore energy platform, mount the offshore wind turbine using the crane and then easily remove the crane from the offshore energy platform such that the crane can be used to install an offshore wind turbine on a different offshore energy platform. Furthermore, should any maintenance be required with a currently installed offshore wind turbine then the crane can be easily mounted on the offshore energy platform to perform the maintenance and then subsequently removed. Accordingly, the advantages of the present disclosure are primarily obtained by the base (or base members) having an open section to permit the installation and / or removal of the crane once a wind turbine is mounted, or installed, on the offshore energy platform. As will be appreciated, there may be numerous configurations of the base to provide one or more base members with an open section and the following description describe several configurations that could be implemented to obtain the advantageous effects of the present disclosure, however, other arrangements or configurations are of course possible.

[0068] With reference to Figures 1 to 12, embodiments where the crane is formed of a single base member will now be described. The crane 1 may comprise a single base 3, wherein the base 3 includes an open first section and a closed, or continuous, second section wherein the second section is substantially aligned with at least a portion of the offshore energy platform on which the crane will be mounted. The dimensions of the open section of the base are predetermined to be of a sufficient width to accommodate a diameter of the wind turbine tower section to enable installation, or removal, of the crane base when the wind turbine tower section is installed on, or mounted on, the offshore energy platform. In some embodiments, the internal shape, or inner profile, of the base may additionally be substantially matched, at least in part, to at least a portion of the shape, or outer profile, of a wind turbine tower section. In the examples shown in the accompanying Figures, the base may be formed with two elongate structural members disposed substantially parallel to each other in a horizontal plane and an interconnecting structural member disposed substantially perpendicularly between the two elongate structural members. For example, the base may be formed in a substantially “C”, “H”, or “II” shape. The interconnecting structural member may therefore be straight or may be curved to substantially follow or match the profile of the platform on which the crane is to be mounted. For example, the closed, or continuous section of the “C” or “II” shaped base may be aligned with a portion of the platform structure to which the crane will be mounted. However, as described hereinabove, the shape of the base may be any suitable shape to enable a connection to the platform, to provide sufficient stability when mounted on the platform, and to permit the base to be installed and / or removed whilst a wind turbine is installed.

[0069] The open section enables the crane to be mounted on the platform 8 when the wind turbine, or parts thereof, is mounted on, or being installed on the platform, for example, in order to enable the crane to be removed once the wind turbine has been installed and / or to be used for maintenance of the offshore wind turbine at a later date after the wind turbine has been installed. Thus, a cross-section of the base in the horizontal plane, e.g. a plane substantially parallel to the lower surface of the base, or the upper surface of the platform would, in this example, resemble a substantially “C”, “H”, or “II” shape. However, as will be appreciated, further arms or members may be attached to, or form part of, the base for additional purposes, for example, stability, support (e.g. to support the crane arms when in a transport configuration), and so on and as such the shape of the base may be of any suitable shape for the purpose of the present disclosure.

[0070] In the above description, the outer profile of the base of the crane is described as being substantially of a “C” “H”, or “II” shaped. However, as will be appreciated, the base may have any outer profile, e.g. square, triangular, V-shaped, and so on, where the open section permits the installation and / or removal of the crane when a wind turbine is mounted on the offshore energy platform. Additionally, in some embodiments, the internal shape, or inner profile, of the base formed by the open first section and the closed second section are substantially matched to at least a portion of the shape of the wind turbine tower section .

[0071] The crane 1 further comprises at least one crane arm 2, where each crane arm may be, for example, a twin telescopic boom arm, however, as will be appreciated any suitable crane arms may be implemented. The number of crane arms used (e.g. 1, 2, 3, etc.), may depend upon the dimensions and weight of the offshore renewable energy device (or components thereof) being installed or maintained. In the examples shown in the Figures, two crane arms are shown. The crane arms 2 are connected to the base 3, wherein the connection between the crane arms 2 and the base 3 may be any suitable connection, or type of connection, to enable movement, e.g. lateral, vertical and / or rotational movement, of each arm either independently or cooperatively. The connection of each arm of the crane to the crane base may form a main pivot point 4 for each arm. The crane arms may additionally include a respective winch support arm for the winches that operate the crane lines of each corresponding crane arm. In embodiments, one or more of the crane arms may permit movement in up to three dimensions. However, a crane arm that permit movement in three dimensions is typically heavier (i.e. increased weight) and incurs a higher cost. Thus, the arrangement and configuration of the present disclosure, e.g. having two crane arms symmetrically spaced apart on the base either side of the location of a tower section of the offshore wind turbine means that crane arms that permit movement in only one direction, e.g. a shear leg crane, can be implemented to lift the components of the offshore wind turbine, which reduces both the weight and cost of the crane arms.

[0072] The crane 1 further includes at least two crane alignment and connection members 5 that are disposed on, or in, a lower surface of the closed continuous section and / or the elongate members of the crane base 3. For example, the crane alignment and connection members 5 may be in the form of a protrusion disposed on the lower surface (as shown in the accompanying Figures) or may be in the form of an indentation in the lower surface. Each of the at least two crane alignment and connection members 5 may be the same or different, e.g. each of the crane alignment and connection members 5 may be protrusions or indentations, or a number may be protrusions, and the remaining number may be indentations. There may be a predetermined gap (e.g. defined by the shape and dimensions of the crane alignment and connection members) between the lower surface of the base and the upper surface of the platform, or the lower surface of the closed, or continuous, second section of the base mates, or engages, with an upper surface of the top end of the platform, on which the crane is to be removably, and temporarily, mounted. Thus, the upper surface of the top end of the platform comprises at least two platform alignment and connection members 6 that are complimentary shaped to, and engage with, a respective one of the crane alignment and connection members 5. As shown in the accompanying Figures, the platform alignment and connection members 6 are also protrusions that align with, and engage with, the complimentary shaped crane alignment and connection members 5. However, as will be appreciated other arrangements of the respective alignment and connection members on the crane and the platform are possible. For example, the crane alignment and connection members 5 on, or in, the crane base 3 may be formed of protrusions and the respective platform alignment and connection members 6 of the platform may be a complimentary shaped indentation, or vice-versa, or a combination thereof. The crane alignment and connection members and the platform alignment and connection members may be implemented as a “cup and cone” arrangement,

[0073] The platform may include a number of platform alignment and connection members 6 that is greater than the number of crane alignment and connection members 5 in, or on, the crane base 3. This advantageously enables the crane 1 to be mounted on the platform 8 at different positions, or different alignments, on the platform 8 for the ease of installation and / or maintenance, and to take into account the prevailing weather conditions.

[0074] The crane alignment and connection members 5 are therefore “co-designed” with the platform alignment and connection members 6 such that the installation, or mounting, of the crane on to the platform can be performed in a weather tolerant process and without requiring precision as the respective alignment and connection members may guide the crane base onto, and into engagement with, the platform with a degree of tolerance, which is advantageous in windy conditions that are often encountered at offshore deployment sites. The crane alignment and connection members 5 may therefore be trumpet (or conical) shaped indentations and the platform alignment and connection members 6 may be complimentary conical shaped protrusions, as illustrated in the accompanying Figures, or vice-versa. However, as will be appreciated other coordinated, or compatible, shapes are of course possible, such that the respective alignment and connection members of the crane and platform enable the crane installation to be effectively self-aligning and able to compensate for prevailing wind conditions.

[0075] The crane alignment and connection members 5 and platform alignment and connection members 6 may be radially spaced from a central axis of the platform 8, which will typically be aligned with a central axis of a wind turbine tower 9, as shown in the accompanying Figures. As described above, there is at least two crane alignment and connection members 5 on the crane and complimentary platform alignment and connection members 6 on the platform. However, in embodiments, and as shown in the accompanying Figures, the crane base includes three crane alignment and connection members 5 which provides a stable and loads efficient arrangement as the crane alignment and connection members 5 and the platform alignment and connection members 6 are designed to distribute the loads from the crane into the structure of the platform 8. As will be appreciated, a greater number of crane alignment and connection members 5 and corresponding platform alignment and connection members 6 can be implemented to further distribute the loads from the crane to the platform.

[0076] In embodiments, the platform alignment and connection members may be equally spaced angularly around the central axis of the platform 8 and the crane alignment and connection members will be located on the crane base such that they mate, or engage, with the platform alignment and connection members. The platform may include a number of platform alignment and connection members 6 that is greater than the number of crane alignment and connection members 5 on, or in, the crane base 3, or the platform alignment and connection members may be disposed at locations on the platform, to advantageously enable the crane 1 to be mounted on the platform 8 at different positions, or different alignments, on the platform 8 for the ease of installation and / or maintenance, and to take into account the prevailing weather conditions.

[0077] To enhance the stability and safety of the crane mounted on the platform, a releasable locking mechanism may be used to lock the crane on to the platform once mounted. The releasable locking mechanism may form part of one or more of the respective complimentary alignment and connection members, or may be separate thereto.

[0078] The crane may also include a crane spreader bar 7, where the spreader bar 7 may be used to enable the crane, during operation, to lift objects from a single point without pulling the crane arms, e.g. twin booms, 10 together.

[0079] The ‘crane base 3 having an open first section, which enables the crane to fit around, e.g. is complimentary to, a structure of the renewable energy device, e.g. the wind turbine tower 9, in combination with extendable crane arm members of the crane arms, e.g., twin booms 10 of the twin boom telescopic crane 2, enables the crane to be lifted on to and off from the platform 8 when the renewable energy device, e.g. wind turbine 11 is fully assembled thereon. The crane 1 enables the renewable energy device, e.g. wind turbine, components to be lifted close to the main pivot point 4 of the crane arms when mounted on the platform without collision with the structure of the crane. The main pivot point 4 additionally enables the crane arms to be placed in a transport and installation configuration in which the crane arms are docked with the base, for example, folded onto, or substantially onto, the surface of the base of the crane, and the main pivot point further provides both lifting strength and stability. The base may include additional arms attached to the closed section of the base and aligned with the elongate members wherein the additional arms support the crane arms in the docked transport and installation configuration.

[0080] In embodiments, the crane arms may be either, or both, telescopic or folding which enables the crane to be more compact, as the crane arms can be retracted, and / or folded, into a docked position when not in use, for example when the crane is in the transportation configuration, and during lifting onto, or off, the platform.

[0081] In embodiments, the platform 8 may be a floating platform as illustrated in Figures 1A to 1 F, and in other embodiments the platform may be a seabed mounted platform as illustrated in Figures 2A and 2B.

[0082] With reference to Figures 3A, 3B and 5, in some embodiments the platform 8 may be a truss structure. In such embodiments the top of the truss main chords 12 of the platform truss structure can be aligned with respective ones of the crane alignment and connection features 5 such that the loads from the crane when mounted on the platform can be transferred directly into the truss main chords 12 of the platform truss structure.

[0083] Returning to Figures 1 A to 1 F, in some embodiments a spreader bar 7 may be used to allow the crane to lift objects from a single point without pulling the crane arms, 10, e.g. twin booms, together, which improves the stability, safety, and functionality of the crane. In embodiments where the platform mounted crane 1 is utilised to install a wind turbine, a wind turbine blade installation tool 13 has also been designed that is compatible with the platform mounted crane 1 to enable the easy rotation and positioning of wind turbine blades for attachment to the wind turbine rotor.

[0084] An exemplary embodiment of the wind turbine blade installation tool will now be described with reference to Figures 6A to 6C. The wind turbine blade installation tool 13 may comprise blade Grips 14 to hold a wind turbine blade 15 at or near the blade’s centre of gravity, a horizontal to vertical motor pivot system 16, and a pitch motor pivot system 17. The wind turbine blade installation tool 13 may be attached to the crane’s lifting wires 18, such that the blade installation tool 13 can be lifted, or hoisted, by the crane 1. The wind turbine blade grips 14 are configured to grip a wind turbine blade 15 to be installed in a horizontal orientation. The horizontal to vertical motor pivot system 16 can then be used to rotate the wind turbine blade 15 from a horizontal orientation to a vertical orientation after the wind turbine blade has been lifted, or hoisted, to sufficient height by the platform crane 1 to avoid any damage to the wind turbine blade. The pitch motor pivot system 17 can be used to change the pitch of the wind turbine blade 15 to the required pitch for installation into the wind turbine rotor. Accordingly, the above-described crane 1 together with the blade installation tool 13 can be used to efficiently install and maintain renewable energy devices, preferably wind turbines, without significant sea state limitations.

[0085] An installation sequence process will now be described, by way of example, and with reference to Figures 7 to 12.

[0086] With reference to Figure 7A, a crane supply vessel 19 equipped with a vessel crane 20 delivers the installation and maintenance crane 1 to an energy platform 8. The installation and maintenance crane 1 may be positioned on a motion compensated platform 21 on the crane supply vessel 19 in a compact transportation configuration.

[0087] With reference to Figure 7B the vessel crane 20 of the crane supply vessel 19 is used to lift the installation and maintenance crane 1 off the motion compensated platform 21 and onto the energy platform 8.

[0088] With reference to Figure 7C the installation and maintenance crane 1 is latched on to and engaged with the platform alignment and connection features 6 on the energy platform 8.

[0089] With reference to Figure 7D, a walk to work system 222 is deployed from the crane supply vessel 19 for technicians to board the energy platform 8 to erect and operate the installation and maintenance crane 1.

[0090] With reference to Figure 7E the installation and maintenance crane 1 is erected on the energy platform 8, wherein the installation and maintenance crane 1 is designed to selferect from the transportation configuration to an operation configuration on the platform, however, as will be appreciated the installation and maintenance crane may be manually adjusted from the transportation configuration to an operation configuration.

[0091] With reference to Figure 7F a wind turbine component supply vessel 23 is sent to the platform with the necessary components of a wind turbine, wherein the component supply vessel 23 may also be equipped with a motion compensated platform 24. The component supply vessel 23 is positioned below the installation and maintenance crane 1 so that the installation and maintenance crane can lift, or hoist, the wind turbine components off the component supply vessel 23 and onto the energy platform 8.

[0092] With reference to Figure 8A a first wind turbine tower section 25 is moved onto the vessel motion compensated platform 24, wherein the vessel motion compensated platform 24 can be used to compensate for motion relative to the now platform mounted installation and maintenance crane 1. With reference to Figure 8B the first wind turbine tower section 25 is rigged to the installation and maintenance crane 1 and lifted, or hoisted, by the installation and maintenance crane 1.

[0093] With reference to Figure 8C the first tower section 25 is lifted into place and installed on the energy platform 8.

[0094] With reference to Figures 8D and 8E the process used to install the first wind turbine tower section is repeated to install the second turbine tower section 26 and the third turbine tower section 27. Wind turbines typically have two to four tower sections in total, but the process can be applied to any number of tower sections, or to lift a single complete tower. It is also possible to lift a single tower with the nacelle already attached, known as a towernacelle assembly.

[0095] With reference to Figure 9, the same process used to install the wind turbine tower sections is used to install the nacelle 28 on top of the wind turbine tower 9.

[0096] With reference to Figure 10A, the wind turbine blade installation tool 13 is loaded onto the vessel motion compensated platform 24 and rigged to the installation and maintenance crane 1. The first wind turbine blade 15 is loaded onto the vessel motion compensated platform 24 using the supply vessel crane 29, and the installation and maintenance crane 1 is rigged to lift the wind turbine blade 15 using the wind turbine blade installation tool 13, wherein the installation and maintenance crane 1 lifts the wind turbine blade in a horizontal orientation.

[0097] With reference to Figure 10B, when the wind turbine blade 15 is lifted to sufficient height, the wind turbine blade installation tool 13 is used to rotate the blade by substantially 90 degrees, so that it is substantially vertically oriented with the blade root pointing towards the wind turbine rotor 30. The wind turbine blade installation tool 13 is used to pitch the wind turbine blade by a few degrees (typically approximately 5 degrees) to be in the correct position and orientation for installation into the bottom of the wind turbine rotor 30.

[0098] With reference to Figure 10C, the installation and maintenance crane booms 10 are positioned to allow the wind turbine 11 to be rotated to the correct position to install the second wind turbine blade, and the same wind turbine blade installation process is repeated as for the first wind turbine blade. This whole process is repeated to install the third wind turbine blade. This installation sequence example is for a three bladed turbine, but the same principle can be applied to wind turbines with any other numbers of blades. With reference to Figure 10D, after all three wind turbine blades have been installed the wind turbine 11 is rotated through 60 degrees and the installation and maintenance crane 1 places the blade tool 13 back on the component supply vessel 23.

[0099] With reference to Figure 11, the installation and maintenance crane 1 is folded back into a compact transportation configuration. The crane supply vessel 19 returns to the energy platform 8, where the installation and maintenance crane 1 is unlatched, or detached, from the energy platform 8 and is lifted off the energy platform 8 by the crane supply vessel crane 20.

[0100] With reference to Figure 12, the installation and maintenance crane 1 is transported away from the energy platform 8 by the crane supply vessel 19 and the wind turbine 11 is fully installed on the energy platform 8.

[0101] Turning now to the embodiments where the base of the crane is formed with at least two sections, this will be described with reference to Figures 13A and 13B. As will be appreciated, many features described hereinabove in relation to the base being formed of a single component equally apply to the embodiments of the crane base being formed of two or more base components. For example, the features of the crane / platform alignment and connection members, the one or more crane arms, and so on.

[0102] In these embodiments the crane 1 may comprise a base 3 that is formed of at least two base members 3a, 3b, which enables the two base members 3a, 3b to be installed and / or removed separately, or independently. The at least two base components of the base of the crane may totally encompass, e.g., wrap around or surround, the outer profile of the offshore wind turbine tower section wherein each of the base members include an open section which when installed forms a base without an open section. Alternatively, the base formed of the two or more base members may, when formed as a base, includes an open section, as described in the above embodiments, where the base including the open section is split into two or more base members that can be installed separately, or independently.

[0103] One or more of the base members 3a, 3b of the base may have a crane arm 2 mounted thereon depending on the requirements, dimensions, and weight of the renewable energy device to be installed or maintained. In the current example shown in Figures 13a and 13b two crane arms are used with a crane arm 2 mounted on each of the two base members. However, other arrangements are of course possible, such as one crane arm mounted on one of the at least two base members, two on one of the base members, three crane arms on one base members or split between the two base members. If there are more than two base members then any number of cranes may be attached to each of the base members. The arrangement, or configuration, of at least two base members3a, 3b forming the base of the crane has the advantage of enabling two or more members of the base of the crane to be installed separately, or individually, on the energy platform in two (or more depending on the number of base components) separate lifting operations.

[0104] It is preferable, but not essential, that each of the base members include at least one of the crane alignment and connection members that were described above in order to provide stability and a secure connection between the crane base and platform. Thus, if three crane alignment and connection members are implemented with a base comprising two base members then two crane alignment and connection members may be provided on one of the base members and the remaining crane alignment and connection member may be provided on the other of the two base members. As will be appreciated, the number and split of the crane alignment and connection members across the number of base members can be configured as required. In some embodiments, two adjacent base members may at the join therebetween, or via an overlap between adjacent base members, cooperatively form a crane alignment and connection member. Furthermore, each base member may include a base alignment and connection member to securely engage and attach two adjacent base members at the join therebetween as shown in Figure 13B.

[0105] An advantage of providing a base formed of two or more base members is that the lifting operation to install each of the base members individually requires a smaller vessel crane with a lower lifting capacity, in comparison to a single base. A further advantage to a base split into two or more members, wherein at least one of the base members include a crane arm mounted thereon, is that the lifting operation to install the base member with a crane arm can be made from the side of the crane arms. This enables the installation crane to have a shorter reach, and it enables the base with a crane arm mounted thereon to be lifted to include a longer crane arm, or the crane arm can be lifted in its fully extended state, e.g. the crane arm may not require to have a shortened state. A crane arm not requiring a shortened state, e.g. achieved through being a telescopic crane arm is advantageous as it is often simpler and cheaper to manufacture and is lighter.

[0106] As described hereinabove, in embodiments where two crane arms are implemented each crane may operate independently or cooperatively.

[0107] Figure 13A shows the first base member 3a of a platform mounted crane with a single crane arm installed on an energy platform with two of the crane alignment and connection members 5, connected to two of the platform alignment and connection members 6. Figure 13B shows the second of the two base members 3b of a platform mounted crane installed in addition to the first base part 3a. One of the crane alignment and connection members 5 on the second base member 3b, is connected to one of the platform alignment and connection members 6. In addition, a further crane alignment and connection member 5 on the second base member 3b is connected to the same platform alignment and connection member 6 as the other base member 3a is already connected to.

[0108] In the foregoing embodiments, features described in relation to one embodiment may be combined, in any manner, with features of a different embodiment in order to provide a more efficient and effective installation of an offshore wind turbine using an installation and maintenance crane. Note that, the above description is for illustration only and other embodiments and variations may be envisaged without departing from the scope of the invention as defined by the appended claims.

Claims

Claims1. An installation and maintenance crane for installation and maintenance of an offshore wind turbine on an offshore energy platform, comprising: a base, wherein the base includes at least one base member having an open section; at least two crane arms connected to the base; and at least two crane alignment and connection members disposed on, or in, the base; wherein one or more of the at least two crane alignment and connection members are configured to operatively mate with a respective complimentary platform alignment and connection members disposed on the offshore energy platform.

2. The installation and maintenance crane according to claim 1, in which the open section of the at least one base member permits installation and / or removal of the installation and maintenance crane with an offshore wind turbine installed on the offshore energy platform.

3. The installation and maintenance crane according to claim 2, in which the base is formed of one base member and further comprises: two elongate structural members disposed substantially parallel to each other in a horizontal plane; and an interconnecting structural member disposed substantially perpendicularly between the two elongate structural members4. The installation and maintenance crane according to claim 3, in which the crane alignment and connection members are disposed on the elongate structural members and / or the interconnecting structural member.

5. The installation and maintenance crane according to any one of the preceding claims, in which the base is II shaped, H-shaped, or C shaped.

6. The installation and maintenance crane according to any one of claims 1 to 5, wherein the base includes an inner profile that is substantially matched, at least in part, to at least a portion of an outer profile of a tower section of the offshore wind turbine.

7. The installation and maintenance crane according to claim 1 or 2 in which the base is formed by two or more base members.

8. The installation and maintenance crane according to claim 7, in which each base member comprises at least one base connection operable to connect adjacent base components.

9. The installation and maintenance crane according to claim 7 or 8, in which the base formed by the two or more base components is configured to surround an outer profile of a tower section of the offshore wind turbine.

10. The installation and maintenance crane according to any one of claims 7 to 9, in which each of the two or more base members are installed separately on to the offshore energy platform.

11. The installation and maintenance crane according to any one of claims 7 to 10, in which each of the two or more base members comprise at least one crane alignment and connection member.

12. The installation and maintenance crane according to any one of claims 7 to 11 , in which at least one of the two or more base members comprises a crane arm.

13. The installation and maintenance crane according to any one of the preceding claims, in which the at least two crane arms are spaced apart to permit components of the offshore wind turbine to pass between the two crane arms.

14. The installation and maintenance crane according to claim 13, in which the at least two crane arms are configured to operate cooperatively to lift a component of the offshore wind turbine, such that loads generated lifting the component are symmetrically distributed to the offshore energy platform.

15. The installation and maintenance crane according to any of the preceding claims, in which the crane arms are telescopic crane arms and / or folding crane arms.

16. The installation and maintenance crane according to any of the preceding claims, in which the at least two crane alignment and connection members are formed as one or more indentations being shaped to receive complimentary shaped one or more protrusions of the respective platform alignment and connection members.

17. The installation and maintenance crane according to any one of claims 1 to 15, in which the at least two crane alignment and connection members are formed as one or more protrusions being shaped to engage with a complimentary shaped one or more indentations of the respective platform alignment and connection members.

18. The installation and maintenance crane according to claim 18 or 19, in which the indentations and the protrusions are of a conical shape.

19. The installation and maintenance crane according to any of the preceding claims, wherein the crane alignment and connection members are configured to distribute loads from the installation and maintenance crane to a structure of the offshore energy platform.

20. The installation and maintenance crane according to any of the preceding claims, wherein the installation and maintenance crane is configured to be installed in one of aplurality of directions relative to the offshore energy platform based on the prevailing environmental conditions.

21. The installation and maintenance crane according to any of the preceding claims, wherein the at least two crane arms permit components of the offshore wind turbine to be lifted close to a main pivot point of the installation and maintenance crane without collision with the structure of the installation and maintenance crane.

22. The installation and maintenance crane according to any of the preceding claims, wherein the installation and maintenance crane has a transportation and installation configuration in which the at least one crane arm is docked with the base.

23. The installation and maintenance crane according to any one of the preceding claims, wherein the installation and maintenance crane is operably configured to move one or more of the offshore wind turbine components in one or more combined hoists or in a single hoist, wherein the components include a tower segment, a nacelle, a generator, a hub, and a blade.

24. The installation and maintenance crane according to any of the preceding claims, wherein a relative motion between an offshore wind turbine component on a component supply vessel and the offshore energy platform mounted installation and maintenance crane is minimised by a motion compensated platform on the component supply vessel.

25. The installation and maintenance crane according to any of the preceding claims, further comprising a wind turbine blade installation tool attachment, the wind turbine blade installation tool attachment comprising: one or more blade grips to grip a wind turbine blade; a horizontal-to-vertical and / or vertical-to-horizontal motor pivot system, configured to rotate a wind turbine blade; and a pitch motor pivot system, configured to control a pitch of the wind turbine blade.

26. An offshore energy platform comprising: at least two platform alignment and connection members disposed on, or in, an upper surface of the offshore energy platform; wherein the at least two platform alignment and connection members are configured to operatively mate with a respective complimentary crane alignment and connection members disposed on, or in, an installation and maintenance crane according to any one of claims 1 to 31.

27. The offshore energy platform of claim 26, wherein the offshore energy platform is formed of a truss structure and the at least two platform alignment and connection members are formed in, or on, each chord of the truss structure.

28. A method of installing an installation and maintenance crane according to any one of claims 1 to 25 on to an offshore energy platform, the method comprising: lifting the base, using a vessel crane, from a vessel on to the offshore energy platform; installing the base by aligning and engaging the crane alignment and connection members disposed on, or in, the base with corresponding platform alignment and connection members disposed on the offshore energy platform; and disengaging the vessel crane.

29. The method of claim 28, in which the base is formed of two or more base members and the method further comprises: lifting and installing each base member independently; and connecting each of the two or more base members to form the base.

30. A method of removing an installation and maintenance crane according to any one of claims 1 to 25 from an offshore energy platform, the method comprising:lifting the base, using the vessel crane, from the offshore energy platform on to the vessel.

31. The method of claim 30, in which the base is formed of two or more base members and the method further comprises: lifting each base member independently on to the vessel.

32. A method of operating an installation and maintenance crane according to any one of claims 1 to 25 on to an offshore energy platform, the method comprising: lifting, by the installation and maintenance crane, a component of the offshore wind turbine from a supply vessel; and installing the component of the offshore wind turbine onto the offshore energy platform.

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