WO2012118383A1

WO2012118383A1 - A system for installing a nacelle for an axial turbine on a submerged foundation, a nacelle, and saddle for installing the nacelle

Info

Publication number: WO2012118383A1
Application number: PCT/NO2012/050002
Authority: WO
Inventors: Hans Olav STRØMME; Michael BETSCHARD
Original assignee: Hammerfest Strom As
Current assignee: Hammerfest Strom As
Priority date: 2011-03-02
Filing date: 2012-01-12
Publication date: 2012-09-07
Anticipated expiration: 2013-09-02
Also published as: NO332202B1; NO20110329A1

Abstract

The present invention relates to a system for installing a nacelle 3 for an axial turbine for the production of electric energy from currents in bodies of water on a foundation 2. The nacelle 3 includes at least two opposing, axially aligned front support pins 10. A saddle structure 6 is secured to the foundation 2. The saddle structure includes at least two front support slots 8 for receiving the support pins 9. Furthermore, a nacelle 3 and a saddle 6 structure are claimed.

Description

A system for installing a nacelle for an axial turbine on a submerged foundation, a nacelle, and saddle for installing the nacelle

The present invention relates to axial turbines for the production of electric energy from currents in bodies of water, and specifically a saddle supporting structure, a nacelle installation system and a nacelle adapted for a saddle supporting structure. The saddle may typically be used in connection with a foundation with an inclined carrying pillar for carrying a turbine with turbine blades and is a

solution/interface between the nacelle and the substructure. The nacelle, the turbine, the saddle supporting structure, and the foundation or carrying structure form a power plant or power generating assembly.

Dynamic effects may occur due to unbalance between the various turbine blades because of drag in particular from the foundation, inhomogeneous flow of current etc. potentially imposing considerable mechanical loads on the power generating assembly in addition to the axial and torque loads from the turbine. The dynamical forces that occur each time a turbine blade passes in the shadow of the carrying structure. Foundations of the above mentioned type typically have an inclined carrying pillar to increase the distance between the turbine blades of the turbine and the carrying pillar to reduce the abovementioned effect. The dynamic loads must in turn be taken up between the substructure/foundation and the nacelle. The present invention of the invention is however not limited to structures with an inclined carrying pillar. The invention is particularly suitable for a foundation adapted for being placed on a seabed for exploiting tidal currents.

Research and development relating to tidal power stations or plants for producing energy has evolved over decades. Tidal power is predictable and independent of weather.

Such power generating assemblies or plants are often assembled from modules placed on a seabed.

Installation of modules is however challenging because of their considerable dimensions, because the modules necessarily must be placed in flowing bodies of water and because the modules in some cases are installed relatively deep. The modules are exposed to considerable mechanical loads from the flowing bodies of water and from the turbine. These loads can be fluctuating and create natural oscillations in the structure. The modules, and in particularly the module that includes a nacelle and the turbine, should be installed quickly as the installation preferably should be completed during the change of tide to avoid the current in the area being too strong to prevent installation.

Examples of tidal plants assembled of modules are found in patent

applications WO2004022968 and WO2004015264, Hammerfest Strom. These publications describe foundations intended to be placed on the seabed, and modules placed on the foundations. The modules may include a turbine, a generator for electric current, a transmission and various electrical components. WO2004015264 describes a guiding apparatus for subsea modules, a method and a foundation. Parts of the guiding apparatus described in this document may be used in conjunction with the present invention

The turbine is supported in a nacelle that again is secured to a foundation that may include one or several pillars or columns.

The present invention concerns a nacelle installation system or connection that substantially reduces the negative effects described above, and that has a sufficient mechanical strength to withstand the above mentioned loads.

The saddle connection according to the invention may be a part of the substructure and may include a curved structure with support slots, installation guides and a locking mechanism.

The support slots may be cutouts in the saddle connection where support pins of the nacelle rests. The support pins may be fixed to the nacelle shell and are the main load carrying elements between the two bodies. Support pins may be an integral parts of the nacelle, extending outside the nacelle body. The support pins may be round or wedge shaped depending on the choice of the saddle slot design.

The saddle connection may transfer all nacelle forces in to the substructure. Some advantages with using saddle connection between nacelle and substructure include:

• Reduced disturbance of the flow field around the turbine especially when producing downstream the substructure

• Secure fixation of the nacelle to the substructure

• Self locking device, dependent on the slot angle the connection may be used without active lockdown • Easy installation and removal

• Self guiding installation, may be used with or without guide wires

• Self locking when lowered, no active intervention by diver or ROV

required.

The substructure including the saddle connection between the substructure and the nacelle may be optimized to reduce the severity of the tower wake which the blades must pass through when the turbine is operating with the substructure upstream of the rotor. The saddle connection has also been designed to ease installation, requiring only an ROV to secure the nacelle to the substructure and to attach connectors.

The configuration of the present invention is favorable for the force

transmission between the nacelle and substructure. The requirements for bracing and general reinforcement are reduced.

Furthermore it is provided nacelle installation system that provides a simple and cost effective installation of nacelle and turbine modules to a substructure and that simplifies maintenance and exchange of components.

It is an object of the invention to provide a system that can be operated without diver intervention.

This is achieved with the present invention as defined in the independent claims.

The modular assembly eases installation and maintenance. During installation the nacelle and the turbine will normally represent one module and the foundation one or several other modules.

Some advantages of the modular structure, include lower installation costs, stepwise installation, and simpler decommissioning.

One or several guiding wires may extend between a floating vessel and the foundation during installation. One or several lifting wires may extend between the module and a winch on the floating vessel, for raising and lowering the module. Using two wires may however be used to ease installation and retrieval of the module as two wires may facilitate angular adjustment in a vertical plane of the nacelle during installation or retrieval.

The wire or wires attached to the nacelle may be remotely releasable or may be released by a ROV. Locking members for the receiving elements may according to the invention be omitted all together but if such locking is found necessary, then these members may include interlocking means automatically locking the nacelle to the saddle and may include spring-loaded pawls that slip into recesses.

Remote control of the various locking components can be executed through a cable from the vessel, or in any other way well known within the field.

A method installing a nacelle of the invention to a saddle of the invention may include providing a vessel carrying the module over the foundation. The complete guiding and assembly should be performed during a change of tide when the water current is low. The present invention is developed to allow the assembly to be performed in an as short time period, allowing the module to be installed before the water current becomes too strong.

The guiding wires extend between the foundation and the vessel. The module may then be lowered along the guiding wires with the lifting wire and the winch.

The module is then secured to the foundation with the securing members, in that for instance pawls on the foundation meshes with recesses on the module.

During the retreival of the module, this process is reversed. When the assembly is completed, the lifting wires and the guiding wires are released from the module and the foundation, and the assembly is completed.

The resent invention concerns a system for installing a nacelle for an axial turbine on a submerged foundation. The nacelle includes at least two opposing, axially aligned front support pins. Each of the front support pins are adapted to form a nacelle support area and for contact with a saddle structure secured to the

foundation. The saddle structure includes at least two first support slots each adapted to receive the support pins and to form a saddle support area on the saddle structure for supporting the nacelle. At least one additional nacelle support area on the nacelle provides contact with at least one additional saddle support area on the saddle.

The system may further include two axially aligned rear support pins forming two additional nacelle support areas on the nacelle. The saddle structure then includes at least two further rear support slots for receiving the further axially aligned support pins and for forming two additional saddle support areas on the saddle.

A unit including the nacelle and the axial turbine may have a centre of gravity located in front of the axially aligned front support pins when the system includes two axially aligned rear support pins.

The centre of gravity may be located between the axially aligned front support pins and the turbine.

The support slots may be substantially U-shaped, forward inclined slots.

A shark-fin shaped guide face with a rounded nose portion may be located between the support slots.

One additional nacelle support area on the nacelle for contact with at least one additional saddle support area on the saddle may form three support areas defining a triangular plane. A unit including the nacelle and the axial turbine may then have a centre of gravity located such that a vertical line through the centre of gravity extends through said triangular plane.

Furthermore, the invention concerns a nacelle for an axial turbine for the production of electric energy from currents in bodies of water. The nacelle includes at least two opposing, axially aligned support pins, each adapted to form a nacelle support area and for contact with a saddle structure, and at least one additional nacelle support area.

The nacelle may further include two further axially aligned rear support pins, for being received in two rear support slots.

The nacelle further includes a turbine, and a unit including the nacelle and the axial turbine may have a centre of gravity located in front of the axially aligned front support pins.

The centre of gravity may be located between the axially aligned front support pins and the turbine. The nacelle may include one additional nacelle support area on the nacelle for contact with at least one additional saddle support area on the saddle to form three support areas defining a triangular plane. A unit including the nacelle and the axial turbine has a centre of gravity located such that a vertical line through the centre of gravity extends through said triangular plane.

Furthermore, the invention concerns a saddle for installing a nacelle for an axial turbine on a submerged foundation. The saddle includes at least two opposing, axially aligned support slots each adapted to receive support pins on a nacelle and to form a saddle support area. The saddle includes at least one additional saddle support area (16b).

The saddle may include two additional saddle support areas formed by rear support slots for receiving further axially aligned support pins.

Short description of the enclosed drawings.

Figure 1 shows an axial turbine for production of energy from tidal currents, according to the prior art;

figure 2 shows a part of a nacelle for a turbine of the above mentioned type, with two support pins according to the invention;

figure 3 is a side elevation of a nacelle attached to a substructure with a system according to the invention;

figure 3a is a side elevation of a nacelle attached to a substructure with a system according to a different embodiment of the invention;

figure 4 is a side elevation of a saddle structure according to the invention; figure 5 is a front view of a saddle structure and a nacelle according to the invention;

figure 6 is a rear view of the solution shown on figure 5;

figure 7 is a top view of the solution shown in figures 5 and 6; and

figures 8-11 show a saddle and different positions of support pins during installation or disassembly.

Detailed description of an embodiment of the invention with reference to the enclosed figures.

Figure 1 shows a subsea power generator for generating power from currents in water, typically ocean currents, according to the prior art. The generator may also be used in river currents. An axial turbine 1 is supported in a nacelle 3. The nacelle 3 will typically include a generator, a gear box, and a mechanism for adjusting the pitch of the turbine 1. A guide structure 4 is shown. The guide structure may include releasable wires that may be used to guide the nacelle 3 from the surface and on to a substructure 2. The power generator is located on a seabed 5. The substructure 2 includes a short vertical section 2a for receiving an installation cone secured to the nacelle. The present invention will typically be used in connection with power generators of the above mentioned type. The short vertical section 2a can then be omitted as the system according to the invention substitutes the installation cone, and thus improves the flow pattern around the structure as the vertical section 2a is considered unfavorable.

Figure 2 shows a part of a nacelle 3. Four support pins 9, 10 are attached to the nacelle, whereof two support pins are located on each side. There are two rear support pins 9, and two front support pins 10. The support pins 9, 10 are shaped as cylindrical pins extending out from the side of the nacelle. The two front support pins are alined with each other and share a common central axis. Similarly, the two rear support pins 9 are alined with each other, and also shares a common central axis.

Figure 3 shows a nacelle 3 installed on to a substructure 2 with a saddle structure 6 according to the invention. Front support pins 10 and rear support pins 9 are attached to the nacelle 3. The saddle 6 is shown with a front support slot 8 and a rear support slot 7. Furthermore, figure 3 shows the geometry of the side of the saddle 6, and different positions of the support pins 9, 10 during assembly of the nacelle 3 onto the saddle 6. The dashed circles indicate various positions of the support pins 9, 10 during installation, and also show the purpose of the rear guide face 12 and the front guide face 13. The center of gravity CG of the nacelle and turbine is indicated on the figure as CG, and is located in front of the front of the front support pins. The front support pins 10 will then be exposed to a force in a direction substantially upward direction, and the rear support pins 9 will be exposed to a force in the opposite direction, ie, a downward force, (not considering the forces imposed by the turbine/the current). The four support pins in four support slots define four support areas. The geometry of the support slots ensures that the rear support pins 9 are held in place, preventing the nacelle and turbine from pivoting forwards around the front support pins 10. The nacelle 3 will typically be lowered from a vessel in two wires to allow adjustment of the angle of the nacelle to ease installation. A ROV may be used to monitor and facilitate the operation. The lifting wires may be released by remote control, or may be released by the ROV. Divers should be unnecessary. Retrieval is a reversed operation of installation.

The nacelle may be guided along wires extending between the saddle structure 6 and a floating vessel to ease installation of the nacelle to the saddle.

In the shown embodiment, the substructure typically includes a support tube with a 2000mm diameter, the saddle length in a horizontal direction is 3940mm, the distance between the centers of the support pins, and the rounded portions of the support slots is 1539mm, the front guide face 1 1 is substantially linear, horizontal and has a length of 687mm, the nacelle has a diameter of 3200mm, and the support pins have a radius of 200mm.

Figure 3a is a side elevation of a nacelle attached to a substructure with a system according to a different embodiment of the invention, where the rear support pins 9 are substituted with an additional support area 16. The front support pins 10 are attached to the nacelle 3. The saddle 6 is shown with a front support slot 8.

The additional support area 16 includes a nacelle support area 16a on the nacelle and a saddle support area 16b on the saddle in contact with each other. The two support pins 10 and the additional support area 16 are located at each corner of a triangle when seen from above. The unit including the nacelle 3 and the axial turbine has a centre of gravity CG located such that a vertical line through the centre of gravity extends through this triangle, such that the nacelle will rest in these three support areas. This is indicated with a vertical line through the centre of gravity on fig 3a. Figure 3a is shown in an embodiment with the support pins 10 closer to the turbine (not shown) than the additional support area 16, but the saddle could be placed in the opposite direction without departing from the invention, (the support areas would have had to be changed accordingly)

Figure 4 is a side elevation of a saddle 6 attached to a substructure 2. The substructure 2 is typically a foundation or a base founded on a seabed. The saddle 6 includes four slots. There are two rear support slots 7, and two front support slots 8. The support slots 7 and 8 include an open inlet portion, and a rounded bottom portion. The rounded bottom portions have a circular portion with a diameter adapted to the diameter of the front and rear support pins 10, 9 respectively. There is one rear support slot 7 at each side of the saddle, and one front support slot at each side of the saddle 6. The two rear support slots 7 are axially lined with each other, and the two front support slots 8 are aligned with each other. The radius of the rounded portion of the rear support slot is adapted to allow fitment of the rear support pin 9, and the radius of the rounded portion of the front support slot 8 is adapted to the radius of the front support pin 10. The support slots 7, 8 are open, and are sufficiently wide to allow the support pins 9, 10 to enter into the slots, and to be seated in the rounded portions of the slots 7, 8. Under normal operation of a turbine, the nacelle supporting the turbine, is located substantially horizontal, for locating the turbine substantially vertically.

The two support slots 7, 8 each have two substantially straight side portions joined by the circular bottom portion. The two substantially straight side portions are inclined upwards and forwards towards the front of the nacelle. The front of the nacelle in this context is considered as the side of the nacelle carrying the turbine. Accordingly, water flowing through the turbine upstream of the nacelle (from the left of the figure) will tend to press the nacelle and the support pins down into the support slots. The saddle 6 furthermore includes a front guide face 13 for the front support pin 10, and a rear guide face 12 for the rear support pin 9. During installation, when the nacelle, usually with a turbine, shall be installed onto a base or substructure 2 that already is installed on a seabed, the nacelle 3 is lowered by one or two wires extending from a floating vessel. The nacelle with the guiding pins 9, 10 is landed onto the front guide face 13 and the rear guide face 12 respectively, and the rear support pin 9 will slide along the inclined rear guide face 12, pulling the front support pin 10 into the front support slot 8, while the rear support pin 9 lands in the rear support slot 7. The rounded portions of the support slots are now resting against the rounded cylindrical portions of the support pins.

A locking mechanism for holding the support pins in the support slots can be utilized if considered necessary. The nacelle lock may be schematically represented as 11 . The nacelle lock 1 1 may include spring actuated dogs, or any other locking mechanism. The locking mechanism may be remotely operated to ease installation and retrievable of the turbine, nacelle assembly.

Figure 5 is a front view of the embodiment shown on figure 4, where the nacelle 3 is shown as a circle in the center of the drawing. The front support pins 10, the saddle 6 and the substructure 2 are clearly shown. Furthermore, figure 5 shows one guiding tower 14 located at each side of the saddle 6. The guiding towers 14 have inward inclined faces for facilitating installation and alignment of the nacelle into the saddle. When the nacelle is lowered from the surface onto the saddle, the nacelle may slide along the inclined surfaces of the towers 14, for guiding the nacelle to the correct location.

Figure 6 correspond to figure 5, but shows the rear portion of the saddle 6. As in the previous figures, the saddle 6 is supported by a substructure 2. As figure 6 shows a rear view, only the rear support pins 9 are shown.

Figure 7 is a top view of the saddle 6 shown in the figures 4, 5, 6. Figure 7 clearly shows the four support pins 9, 10 and how they are located at each side of a nacelle.

The figures 8-11 are similar such that the various reference numerals will be relevant to all the figures even if some reference numerals not are indicated. These figures are included to highlight the purpose of the geometry of the saddle structure 6 in relation to the front support pin 10 and the rear support pin 9. The support pins 9, 10 are fixed to the nacelle and have a fixed distance therein between. The purpose of the geometry of the saddle structure 6 is to ease installation of the nacelle on the saddle 6. As can be seen on figure 8, the saddle includes a slightly inclined front guide face 13 followed by a face in the front support slot 8 with a steeper inclination. This face ends in a rounded bottom portion of the front support slot 8 that again is followed by an inclined straight section. This inclined straight section extends further into a rounded nose section 15 and then into an inclined rear guide face 12. This rear guide face 12 is followed by a more or less straight section of the rear support slot 7. This straight section of the support slot 7 has a steeper inclination then the rear guide face 12. This inclined face is followed by a rounded bottom portion of the rear support slot 7, that again is followed by an inclined straight portion that is followed by a substantially vertical portion on the guiding towers 14. The front and rear support slots 8, 7 respectively are substantially U-shaped. The portion of the saddle 6 between the two support slots could be expressed as shark fin or wave shaped. The front support pin 10 and the rear support pin 9 are shown in different positions. The pair of support pins are schematically attached to each other with a line, but clearly this line is only indicated to show the relationship between the support pins, and could be substituted with the nacelle. The various circles interconnected with lines show how the nacelle can be guided into or out of the front and rear support slots. For instance, it is clearly shown how the rear support pin 9 can slide along the guiding towers 14 and into the rear support slot, and how the front support pin 10 can move into the front support slot 8. The lowermost position of the front and rear support pins are shown, when the front and rear support pins are seated in the rounded portion of the support slots, and shows the position of the pins when the nacelle is installed. Due to the location of the center of gravity of the nacelle and turbine structure, the front support pin 10 will impose a downward directed force onto the saddle, and the rear support pin 9 will impose an upward directed opposite force onto the rear support slot. The nacelle will thereby be held in position by gravity. The inclined U-shaped rear support slot 7 prevents the rear support pin 9 from moving in an upwards direction. Figure 8 shows how the nacelle can be installed while maintaining a substantially horizontal position.

Figure 9 corresponds to figure 8, but highlights how the nacelle will move if it enters the support slots at an angle pointing downwards at the front. The front face of the front support slot 8 will push the support pins backwards and into the seated position. Figure 9 however shows a threshold angle, where the upper position of the rear support pin 9 is shown as an angle where the nacelle is prevented from being installed, and the lower position shows an angle where the nacelle will slide in place.

Figure 10 corresponds to the former figures, but shows how the guide face of the guiding towers 14 will guide the rear support pin 9, and how the nose section 15 will guide the front support pin 10 to ensure that the rear support pin 9 is properly guided into the rear support slot 7.

Figure 1 1 corresponds to the previous figures 8-10 and is included to describe further scenarios during installation or retrieval of the nacelle. From figure 1 1 , it is clearly shown how the nose section 15 will prevent the rear support pin 9 from being installed without the front support pin being properly seated.

Claims

1 . A system for installing a nacelle (3) for an axial turbine on a submerged

foundation (2),

c h a r a c t e r i z e d i n t h a t:

the nacelle (3) includes at least two opposing, axially aligned front support pins (10), each adapted to form a nacelle support area and for contact with a saddle structure (6) secured to the foundation (2);

wherein the saddle structure includes at least two first support slots (8) each adapted to receive the support pins (9) and to form a saddle support area on the saddle structure for supporting the nacelle; and

at least one additional nacelle support area on the nacelle for contact with at least one additional saddle support area on the saddle.

2. The system according to claim 1 , further including two further axially aligned rear support pins (9) forming two additional nacelle support areas on the nacelle, and wherein the saddle structure (6) includes at least two further rear support slots (7) for receiving the further axially aligned support pins (9) and forming two additional saddle support areas on the saddle.

3. The system according to claim 2, wherein a unit including the nacelle (3) and the axial turbine has a centre of gravity located in front of the axially aligned front support pins (10).

4. The system according to claim 3, wherein the centre of gravity is located between the axially aligned front support pins (10) and the turbine.

5. The system according to claim 2, wherein the support slots (7, 8) are substantially U-shaped, forward inclined slots.

6. The system according to claim 2, wherein a shark-fin shaped guide face with a rounded nose portion (15) is located between the support slots (7, 8).

7. The system according to claim 1 including one additional nacelle support area on the nacelle for contact with at least one additional saddle support area on the saddle to form three support areas defining a triangular plane ; and

a unit including the nacelle (3) and the axial turbine has a centre of gravity located such that a vertical line through the centre of gravity extends through said triangular plane.

8. A nacelle for an axial turbine for the production of electric energy from currents in bodies of water c h a r a c t e r i z e d i n t h a t:

the nacelle (3) includes at least two opposing, axially aligned front support pins (10), each adapted to form a nacelle support area and for contact with a saddle structure (6); and

at least one additional nacelle support area.

9. The nacelle according to claim 8, further including two further axially aligned rear support pins (9), for being received in two rear support slots (7).

10. The nacelle according to claim 8, further including a turbine, and wherein a unit including the nacelle (3) and the axial turbine has a centre of gravity located in front of the axially aligned front support pins (10).

1 1. The nacelle according to claim 10, wherein the centre of gravity is located

between the axially aligned front support pins (10) and the turbine (1 ).

12. The nacelle according to claim 9, including one additional nacelle support area (16a) on the nacelle for contact with at least one additional saddle support area (16b) on the saddle (6) to form three support areas defining a triangular plane ; and

wherein a unit including the nacelle (3) and the axial turbine has a centre of gravity located such that a vertical line through the centre of gravity extends through said triangular plane.

13. A saddle for installing a nacelle (3) for an axial turbine (1 ) on a submerged

foundation (2), characterized in that:

the saddle (6) includes at least two opposing, axially aligned support slots (8) each adapted to receive support pins (9) on a nacelle and to form a saddle support area; and

at least one additional saddle support area (16b).

14. The saddle according to claim 13, comprising two additional saddle support areas formed by rear support slots (7) for receiving further axially aligned support pins (9).