NO332202B1 - System for installing a nacelle for an axial turbine on a submerged foundation, a nacelle, and a saddle for installing the nacelle - Google Patents

Abstract

The present invention relates to a system for installing a nacelle (3) for an axial turbine for the production of electrical 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 attached to the foundation (2). The saddle structure includes at least two front support grooves (8) for receiving the support pins (9). Furthermore, protection is required for a nacelle (3) and a saddle structure

Description

The present invention relates to axial turbines for the production of electrical energy from currents in bodies of water, and specifically to a saddle support structure, an installation system for a nacelle and a nacelle adapted to a saddle support structure. The saddle can typically be used in conjunction with a foundation with an inclined supporting pillar to support a turbine with turbine blades, forming a solution/interface between the nacelle and the substructure. The nacelle, the turbine, the saddle support structure and the foundation or supporting structure form a power plant or device for generating electrical power.

Dynamic effects can occur due to imbalance between the different turbine blades due to flow resistance, especially from the foundation, inhomogeneous flow, and so on, which can impose significant mechanical loads on the electrical power generation device, in addition to the axial and torque loads from the turbine. The dynamic forces occur every time a turbine blade passes in the shadow of the supporting structure. Foundations of the above type typically have an inclined supporting pillar to increase the distance between the turbine blades of the turbine and the supporting pillar to reduce the above effect. The dynamic loads must in turn be taken up between the substructure/foundation and the nacelle. However, the present invention according to the invention is not limited to structures with an inclined supporting pillar. The invention is particularly suitable for a foundation adapted to be placed on a seabed to utilize tidal currents.

Research and development related to tidal power plants or facilities for the production of energy has developed over decades. Tidal power is predictable and independent of the weather.

Such power-generating devices or facilities are often assembled from modules placed on a seabed.

However, installation of modules is challenging due to their considerable dimensions, because the modules must necessarily be placed in flowing bodies of water, and because the modules are in some cases installed relatively deep. The modules are exposed to significant mechanical loads from the flowing water masses and from the turbine. These loads can be fluctuating and produce natural oscillations in the structure. The modules, and especially the module that includes the nacelle and the turbine, should be installed quickly, as the installation should preferably be completed when the tide changes to avoid the current in the area becoming too strong to prevent installation.

Examples of tidal systems assembled from modules can be found in patent applications WO2004022968 and WO2004015264, Hammerfest Strøm. 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 device for subsea modules, a method and a foundation. Parts of the guide device described in this document can be used in connection with the present invention.

The turbine is carried in a nacelle which in turn is attached to a foundation which may include one or more pillars or columns.

The present invention relates to a nacelle installation system or a connection which significantly reduces the negative effects described above, and which has a sufficient mechanical strength to withstand the above-mentioned loads.

The saddle connection according to the invention can be part of the substructure, and can include a curved structure with a bearing groove, installation guides and a locking mechanism.

The bearing grooves can be recesses in the saddle connection where the support pins of the nacelle rest. The support pins can be attached to the nacelle's housing, and are the most important load-bearing elements between the two bodies. The support pins can be integral parts of the nacelle, extending to the outside of the nacelle body. The support pins can be round or wedge-shaped, depending on the choice of saddle track design.

The saddle connection can transfer all nacelle forces to the substructure. Some advantages of using a saddle connection between the nacelle and the substructure include: • Reduced disturbance of the flow field around the turbine, especially when producing downstream of the turbine

• Secure attachment of the nacelle to the substructure

• Self-locking device, depending on the track angle, the connection can be used without active locking

Easy installation and removal

Self-supporting installation, can be used with or without guide wires

Self-locking during descent, no active intervention by diver or

ROV required

The substructure including the saddle connection between the substructure and the nacelle can be optimized to reduce the intensity of the tower slipstream that the blades must pass through when the turbine operates with the substructure upstream of the rotor. The saddle connection has also been designed for ease of installation, requiring only one ROV to attach the nacelle to the substructure and to attach connectors.

The configuration of the present invention is advantageous for the power transfer between the nacelle and the substructure. The requirements for bracing and general reinforcement have been reduced.

Furthermore, a nacelle installation system has been provided which provides a simple and cost-effective installation of nacelle and turbine modules on a substructure, and which simplifies maintenance and replacement of components.

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

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

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

Some advantages of the modular structure include lower installation costs, step-by-step installation and easier dismantling.

One or more guide wires may extend between a floating vessel and the foundation during installation.

One or more lifting cables can extend between the module and a winch on the floating vessel, for raising and lowering the module. However, the use of two wires can be used to facilitate installation and retrieval of the module, as two wires can enable angular adjustment in a vertical plane of the nacelle during installation or retrieval.

The cable or cables attached to the nacelle may be remotely releasable, or may be released by an ROV. Locking means for the receiving elements can, according to the invention, be omitted altogether, but if such locking is found necessary, then these means can include interlocking means that automatically lock the nacelle to the saddle, and which can include spring-loaded locking hooks that slide into recesses.

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

A method for installing a nacelle according to the invention on a saddle according to the invention may include providing a vessel that carries the module over the foundation. The complete routing and assembly should be carried out during a change of tide when the water flow is low. The present invention has been developed to allow the assembly to be carried out in a short period of time, which allows the module to be installed before the water flow becomes too strong.

The guide wires extend between the foundation and the vessel. The module can then be lowered along the guide cables with the lifting cable and the winch.

The module is then fixed to the foundation with the fastening means, by e.g. locking hooks on the foundation engage with recesses on the module. During the retrieval of the module, this process is reversed. When assembly is complete, the lifting cables and guide cables are detached from the module and foundation, and assembly is complete.

The present invention relates to a system for installing a nacelle for an axial turbine on a submerged foundation. The nacelle includes at least two opposed, axially aligned front struts. Each of the forward support pins is adapted to form a nacelle bearing area and for contact with a saddle structure attached to the foundation. The saddle structure includes at least two first support grooves 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 further nacelle bearing area on the nacelle provides contact with at least one further saddle bearing area on the saddle.

The system can further include two axially aligned rear support pins which form two additional nacelle support areas on the nacelle. The saddle structure then includes at least two further rear bearing grooves for receiving the further axially aligned support pins and for forming two further saddle bearing areas on the saddle.

An assembly including the nacelle and the axial turbine may have a center of gravity located forward of the axially aligned front struts when the system includes two axially aligned rear struts.

The center of gravity can be located between the axially aligned front support pins and the turbine.

The bearing grooves can be mainly U-shaped, forward-sloping grooves.

A shark fin-shaped guide surface with a rounded nose portion may be located between the bearing grooves.

A further nacelle bearing area on the nacelle for contact with at least one further saddle bearing area on the saddle can form three bearing areas delimiting a triangular plane. A unit that includes the nacelle and the axial turbine can then have a center of gravity located so that a vertical line through the center of gravity extends through the triangular plane.

The invention further relates to a nacelle for an axial turbine for the production of electrical energy from currents in bodies of water. The nacelle includes at least two opposed, axially aligned support pins, each of which is adapted to form a nacelle support area and for contact with a saddle structure, and at least one further nacelle support area.

The nacelle can further include two further axially aligned rear support pins, for reception in two rear support slots.

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

The center of gravity can be located between the axially aligned front support pins and the turbine.

The nacelle may include an additional nacelle bearing area on the nacelle for contact with at least one additional saddle bearing area on the saddle to form three bearing areas defining a triangular plane. An assembly including the nacelle and axial turbine has a center of gravity located so that a vertical line through the center of gravity extends through the triangular plane.

The invention further relates to a saddle for installing a nacelle for an axial turbine on a submerged foundation. The saddle includes at least two opposed, axially aligned bearing grooves each adapted to receive support pins on a nacelle and to form a saddle bearing area. The saddle includes at least one further saddle carrying area (16b).

The saddle may include two further saddle bearing areas formed by rear bearing grooves for receiving further axially aligned bearing pins.

Brief description of the attached drawings.

Fig. 1 shows an axial turbine for the production of energy from tidal currents,

according to the prior art;

Fig. 2 shows part of a nacelle for a turbine of the above-mentioned type, with two support pins according to the invention; Fig. 3 is a side view of a nacelle attached to a substructure with a system according to the invention; Fig. 3a is a side view of a nacelle attached to a substructure with a system according to a different embodiment of the invention; Fig. 4 is a side view of a saddle structure according to the invention; Fig. 5 is a front view of a saddle structure and a nacelle according to the invention; Fig. 6 is a rear view of the solution shown in fig. 5;

Fig. 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 attached figures.

Fig. 1 shows an underwater power generator or power generator for generating electrical power or power from currents in water, typically ocean currents, according to known technology. The generator can also be used in river currents. An axial turbine 1 is carried in a nacelle 3. The nacelle 3 will typically include a generator, a gearbox and a mechanism for adjusting the pitch of the turbine 1. A guide structure 4 is shown. The guiding structure may include releasable wires that can be used for guiding

the nacelle 3 from the surface down onto 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 attached to the nacelle. The present invention

will typically be used in connection with power generators of the above type. The short vertical section 2a can then be omitted, as the system according to the invention replaces the installation cone, thus improving the flow pattern around the structure, as the vertical section 2a is considered unfavorable. Fig. 2 shows part of a nacelle 3. Four support pins 9, 10 are attached to the nacelle, of which 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 designed as cylindrical pins that extend out from the side of the nacelle. The two front support pins are aligned with each other and share a common central axis. Similarly, the two rear support pins 9 are aligned with each other, and also share a common central axis. Fig. 3 shows a nacelle 3 installed on a substructure 2 with a saddle structure 6 according to the invention. The front support pins 10 and the rear support pins 9 are attached to the nacelle 3. The saddle 6 is shown with a front support track 8 and a rear support track 7. Fig. 3 also shows the geometry of the side of the saddle 6, and different positions of the support pins 9,10 during installation of the nacelle 3 on the saddle 6. The dashed circles show different positions of the support pins 9,10 during installation, and also show the purpose of the rear guide surface 12 and the front guide surface 13. The center of gravity CG (center of gravity) of the nacelle and turbine is in the figure indicated as CG, and is located in front of the front of the front support pins. The front support pins 10 will then be subjected to a force in a direction mainly upwards, and the rear support pins 9 will be subjected to a force in the opposite direction, i.e. a downward force. (Does not consider the forces imposed by the turbine/stream). The four bearing pins in four bearing grooves define four bearing areas. The geometry of the support pins ensures that the rear support pins 9 are held in place, which prevents the nacelle and the turbine from turning forward around the front support pins 10.

The nacelle 3 will typically be lowered from a vessel in two cables, to allow adjustment of the angle of the nacelle, to facilitate installation. An ROV can be used to monitor and make the operation easier. The lifting cables can be released using remote control, or can be released by the ROV. Divers should be unnecessary. Downloading is a reverse operation of installation.

The nacelle can be guided along cables that extend between the saddle structure 6 and a floating vessel, to facilitate installation of the nacelle on the saddle.

In the embodiment shown, the substructure typically includes a support tube with a 200 mm diameter, the saddle length in a horizontal direction being 3940 mm, the distance between the centers of the support pins, and the rounded portions of the support tracks being 1539 mm, the advancing surface 11 being essentially linear, horizontal and has a length of 687 mm, the nacelle has a diameter of 3200 mm, and the support pins have a radius of 200 mm.

Fig. 3a is a side view 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 replaced with a further support area 16. The front support pins 10 are attached to the nacelle 3. The saddle 6 is shown with a front bearing groove 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 further support area 16 are located at each corner of a triangle, seen from above. The unit which includes the nacelle 3 and the axial turbine has a center of gravity CG located so that a vertical line through the center of gravity extends through this triangle, so that the nacelle will rest in these three bearing areas. This is indicated by a vertical line through the center of gravity in fig. 3a. Fig. 3a is shown in an embodiment with the support pins 10 closer to the turbine (not shown) than the further support area 16, but the saddle could have been placed in the opposite direction without deviating from the invention. (The bearing areas would have to be changed accordingly). Fig. 4 is a side view 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 grooves. There are two rear bearing grooves 7, and two front bearing grooves 8. The bearing grooves 7 and 8 include an open inlet portion, and a rounded bottom portion. The rounded bottom parts have a circular part with a diameter adapted to the diameter of the front and rear support pins 10 and 9 respectively. There is a rear support groove 7 on each side of the saddle, and a front support groove on each side of the saddle 6. two rear carrier tracks 7 are axially aligned with each other, and the two front carrier tracks 8 are aligned with each other. The radius of the rounded part of the rear support groove is adapted to allow the fitting of the rear support pin 9, and the radius of the rounded part of the front support groove 8 is adapted to the radius of the front support pin 10. The support grooves 7, 8 are open, and are sufficiently wide to allow the support pins 9, 10 to enter the grooves, and to be located in the rounded portions of the grooves 7, 8. During normal operation of the turbine, the nacelle carrying the turbine is located substantially horizontally, for locating the turbine substantially vertically.

Each of the two carrier tracks 7, 8 has two essentially straight side parts joined by the circular bottom part. The two mainly straight side sections are inclined upwards and forwards towards the front of the nacelle. The front of the nacelle is considered in this context as the side of the nacelle that carries the turbine. Water flowing through the turbine upstream of the nacelle (from the left in the figure) will therefore tend to push the nacelle and support pins down into the support grooves. The saddle 6 further includes a front guide surface 13 for the front support pin 10, and a rear guide surface 12 for the rear support pin 9. During installation, when the nacelle, usually with a turbine, is to be installed on a base or substructure 2 that is already installed on a seabed, the nacelle 3 is lowered using one or more cables extending from a floating vessel. The nacelle with the guide pins 9,10 is landed on the front guide surface 13, respectively the rear guide surface 12, and the rear support pin 9 will slide along the inclined rear guide surface 12, which pulls the front support pin 10 into the front support groove 8, while the rear support pin 9 lands in the rear bearing groove 7. The rounded parts of the bearing grooves now rest against the rounded cylindrical parts of the bearing pins.

A locking mechanism to hold the carrier pins in the carrier grooves can be used, if this is considered necessary. The nacelle lock can be schematically represented as 11. The nacelle lock 11 can include spring actuated hooks, or any other locking mechanism. The locking mechanism can be remotely operated to facilitate installation and retrievable by the turbine, nacelle device.

Fig. 5 is a front view of the embodiment shown in fig. 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, fig. 5 a guide tower 14 located on each side of the saddle 6. The guide towers 14 have inward sloping surfaces to facilitate installation and alignment of the nacelle in the saddle. When the nacelle is lowered from the surface of the saddle, the nacelle can slide along the inclined surfaces of the towers 14, seduction of

the nacelle to the correct location.

Fig. 6 corresponds to fig. 5, but shows the rear part of the saddle 6. As in the previous figures, the saddle 6 is supported by a substructure 2. As fig. 6 shows a rear view, only the rear support pins 9 are shown. Fig. 7 is a top view of the saddle 6 shown in figures 4, 5, 6. Fig. 7 clearly shows the four support pins 9,10 and how they are located on each side of a nacelle. Figures 8-11 are almost identical, so that the different reference numbers will be relevant for all the figures even if some reference numbers are not shown. These figures are included to emphasize 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 attached to the nacelle and have a fixed distance between them. The purpose of the geometry of the saddle structure 6 is to facilitate installation of the nacelle on the saddle 6. As can be seen in fig. 8, the saddle includes a slightly inclined front guide surface 13 followed by a surface in the front bearing groove 8 with a steeper slope. This surface ends in a rounded bottom part of the front bearing groove 8, which is again 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 surface 12. This rear guide surface 12 is followed by a more or less straight section of the rear bearing groove 7. This straight section of the bearing groove 7, has a steeper slope than the rear guide surface 12. This sloped surface is followed by a rounded bottom part of the rear carrier track 7, which in turn is followed by a sloped straight part which is followed by a mainly vertical part on the guide towers 14. The front and rear carrier grooves 8, respectively 7 are mainly U-shaped. The part of the saddle 6 between the two bearing grooves can 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 by a line, but it is clear that this line is only shown to show the relationship between the support pins, and could be replaced with the nacelle. The various circles which are interconnected by lines show how the nacelle can be guided into or out of the front and rear support tracks. For example, it is clearly shown how the rear carrier pin 9 can slide along the guide towers 14 and into the rear carrier groove, and how the front carrier pin 10 can move into the front carrier groove 8. The lowest position of the front and rear carrier pins is shown , when the front and rear support pins are located in the rounded part of the support

the tracks, showing 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 force on the saddle, and the rear support pin 9 will impose an upward opposite force on the rear support track. The nacelle will thus be held in place by gravity. The inclined U-shaped rear support groove 7 prevents the rear support pin 9 from moving in an upward direction. Fig. 8 shows how the nacelle can be installed while maintaining a substantially horizontal position. Fig. 9 corresponds to fig. 8, but highlights how the nacelle will move if it enters the bearing grooves at an angle pointing down the front. The front surface of the front support groove 8 will push the support pins backwards and into the position where they sit in place. Fig. 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 into place. Fig. 10 corresponds to the previous figures, but shows how the guide surface of the guide 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 correctly guided into it rear support track 7. Fig. 11 corresponds to the preceding figures 8-10, and is included to describe further scenarios during installation or retrieval of the nacelle. From fig. 11, it is clearly shown how the nose section 15 will prevent the rear carrier pin 9 from being installed without the front carrier pin being properly seated.

Claims (14)

1. System for installing a nacelle (3) for an axial turbine on a submerged foundation (2), characterized in that: the nacelle (3) includes at least two opposed, axially aligned front support pins (10), each of which is adapted to form a nacelle support area and for contact with a saddle structure (6) attached to the foundation (2); wherein the saddle structure includes at least two first support grooves (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 further nacelle bearing area on the nacelle for contact with at least one further saddle bearing area on the saddle. 2. System as set forth in claim 1, further including two further axially aligned rear support pins (9) which form two further nacelle bearing areas on the nacelle, and where the saddle structure (6) includes at least two further rear support grooves (7) for receiving the further axially aligned support pins (9) and the formation of two further saddle bearing areas on the saddle. 3. System as stated in claim 2, where a unit including the nacelle (3) and the axial turbine has a center of gravity located in front of the axially aligned front support pins (10). 4. System as stated in claim 3, where the center of gravity is located between the axially aligned front support pins (10) and the turbine. 5. System as stated in claim 2, where the bearing grooves (7, 8) are mainly U-shaped, forward-tilting grooves. 6. System as stated in claim 2, where a shark fin-shaped guide surface with a rounded nose part (15) is located between the bearing grooves (7, 8). 7. System as set forth in claim 1, including a further nacelle bearing area on the nacelle for contact with at least one further saddle bearing area on the saddle, to form three bearing areas defining a triangular plane; and a unit including the nacelle (3) and the axial turbine has a center of gravity located such that a vertical line through the center of gravity extends through the triangular plane. 8. Nacelle for an axial turbine for the production of electrical energy from currents in bodies of water, characterized in that: the nacelle (3) includes at least two opposed, axially aligned front support pins (10), each of which is adapted to form a nacelle support area and for contact with a saddle structure (6); and at least one additional nacelle bearing area. 9. Nacelle as set forth in claim 8, further including two additional axially aligned rear support pins (9), to be received in two rear support grooves (7). 10. Nacelle as stated in claim 8, further including a turbine, and where a unit including the nacelle (3) and the axial turbine has a center of gravity located in front of the axially aligned front support pins (10). 11. Nacelle as stated in claim 10, where the center of gravity is located between the axially aligned front support pins (10) and the turbine 1. 12. Nacelle as set forth in claim 9, further comprising a further nacelle bearing area (16a) on the nacelle for contact with at least one further saddle bearing area (16b) on the saddle (6), to form three bearing areas delimiting a triangular plane; and where a unit including the nacelle (3) and the axial turbine has a center of gravity located so that a vertical line through the center of gravity extends through the triangular plane. 13. 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 opposite, axially arranged bearing grooves 8, each of which is adapted to receive support pins (9) on a nacelle, and to form a saddle bearing area; and at least one further saddle carrying area (16b). 14. Saddle as stated in claim 13, comprising two further saddle bearing areas formed by rear bearing grooves (7) for receiving further axially aligned bearing pins (9).