WO2024196261A1

WO2024196261A1 - A turbine structure for a plurality of wind turbines

Info

Publication number: WO2024196261A1
Application number: PCT/NO2024/050070
Authority: WO
Inventors: Nils Asbjørn NES
Original assignee: Wind Catching Systems As
Priority date: 2023-03-20
Filing date: 2024-03-19
Publication date: 2024-09-26
Also published as: NO348242B1; NO20230302A1

Abstract

A turbine structure (10) for a plurality of wind turbines (14, 14a,b), comprising at least two upright towers (12) each of which are spaced from the others, each tower (12) being fixed at the bottom thereof to an underlying foundation (20) via a hinge (18). Each tower (12) is connected to a neighbouring tower (12) by a number of tower cables (15) in order to ensure that the towers (12) remain parallel to each other in operation. The turbine structure (10) is secured by front and rear inclined cables (40) connecting the towers (12) to a base (22) in order to control the reciprocating motion of the turbine structure (10) about the hinges (18) against or with a prevailing wind direction. On the front side of each tower (12), a number of wind turbines (14, 14a,b) are mounted one above the other along the length of the tower (12).

Description

A TURBINE STRUCTURE FOR A PLURALITY OF WIND TURBINES

The present patent application discloses a novel type of turbine structure for a plurality of wind turbines that enables the construction of simpler, lighter, larger, and less expensive structures. The scope of the invention is as defined in the preamble of claim 1. Also, using the technology of the invention, it is possible to build significantly higher structures and thereby achieve a smaller area footprint per kilowatt-hour of electrical energy produced.

Structures according to the invention are applicable to both onshore and floating concepts.

BACKGROUND

Wind power technology development: The development of today's wind power technology has its origins in simple windmills that were used for grinding grain and pumping water. It was particularly in the Netherlands that this technology was first developed and deployed. Subsequently, it was realized that windmills could be used as turbines for producing electric energy by connecting the rotor to a generator. The development went on and increasingly bigger and more advanced wind turbines were developed. During this period, all wind turbines were located onshore.

As ever more wind turbines were built, people began to locate the wind turbines in shallow water in the sea, where the wind turbines were founded on the sea floor. Recently, wind turbines have also been located on large floaters in deep water.

Until present, in principle, all wind turbines have been identical. They almost all include a yaw function. That is, the generator and rotor are rotated by means of a small electric motor so that the rotor always faces the direction of the wind. Also, most conventional wind turbines are provided with pitched blades, which blades are rotatable about their longitudinal axis in relation to the wind strength.

It is worth noting that a few concepts have been introduced that challenge the established technology. For example, multi-rotor technology is known, in which several relatively small wind turbines are placed in a large structure mounted on a floater and the entire structure is rotated around a turret so that the turbines always face the direction of the wind. SUMMARY OF THE INVENTION

The turbine structure enables the efficient, cost-saving and area-efficient establishment and use of multi-rotor technology onshore. The solution is useable with both onshore and offshore wind power plants, i.e. with bottom-fixed or floating installations.

To be able to optimally exploit this technology onshore, in most cases, it needs to be established in places having the most unidirectional wind direction possible and where strong winds occur relatively frequent.

To be able to establish wind power plants having multi-rotor technology located both on land and on a floating installation, according to this invention, a number of challenges had to be solved. Such solutions are found and discussed in this patent application.

According to the invention, there is provided a turbine structure for a plurality of wind turbines, comprising at least two upright towers each of which are spaced from the others, each tower being attached at the bottom thereof to an underlying foundation via a hinge. Each tower is connected to a neighbouring tower by a number of tower cables in order to ensure that the towers are kept parallel to each other in operation. The turbine structure is secured by front and rear inclined cables connecting the towers to a base in order to control the reciprocating motion of the turbine structure about the hinges against or with a prevailing wind direction. On the front side of each tower, a number of wind turbines are provided one above the other along the length of the tower.

In an embodiment, each outer tower of a row of towers is supported by one or more lateral cables for bracing, and for keeping the towers restricted approximately parallel to each other, and so that the tower cables between two towers are kept in tension.

In an embodiment, the cables on the front and back sides of the towers are individually pretensioned in such a manner that when pushed backwards by the wind, the towers will remain approximately aligned and excessive tension and subsequent fatigue of the turbine structure are avoided, and the entire turbine structure moves as a unit on the hinges.

In an embodiment, support cables are mounted perpendicularly to the cables and onto small foundations on the ground, each support cable comprising a coil spring with an associated shock absorber. In an embodiment, the towers are constructed from an extruded light metal divided into sections suitable for helicopter lifting, which sections are then assembled by screwing.

In an embodiment, each wind turbine is mounted at a distance from the front side of its corresponding tower, enabling the establishment of an elevator arrangement on the front side of the tower and inside the wind turbine.

In an embodiment, a lift car is mounted between two towers for the maintenance or replacement of wind turbines on both sides of two adjacent towers, with a said lift car being mounted only in every second tower interspace.

In an embodiment, the lift car is attached to the towers by runners extending inside of partially closed rails/travelling paths being part of the turbine structure, and the lift car is lifted and lowered by means of a wire driven by a winch.

In an embodiment, the lift car is connected to existing wires suspended in partially closed rail systems on the front side of the towers, with said wires running over runners at the top of the towers and down on the back side or on one of the lateral sides of the towers and on to a winch system able to lift or lower the lift car.

In an embodiment, the lift car is attached to a rail carriage able move the lift car sideways on the ground relative to the turbine structure, on which rail carriage one or more winches have been established which are connected to the wires suspended from the towers.

According to the invention, the turbine structure intended for onshore and offshore rig structures.

The challenges solved and discussed in this patent application are:

GUYED DESIGN

CONSTRUCTION METHOD

ELEVATOR SYSTEM

GUYED DESIGN ON A FLOATING INSTALLATION

These essential details will be explained in the following with reference to the attached drawings, in which:

Fig. 1 shows a front view of a wind turbine rig. Fig. 2 shows a side view of a mast or tower with a turbine protruding from the front side thereof.

Fig. 3 shows the manner in which each mast/tower of the rig is hinged to a base.

Fig. 4 shows a plan view of an elevator with a working platform associated with two adjacent towers of the rig.

Fig. 5 shows a side view of parts of a tower and indicates the positioning of the elevator with the working platform relative to the projecting shaft with a turbine and turbine blades.

Fig. 1 shows a turbine structure 10 comprising three juxtaposed masts or towers 12, each having a number of turbine generators such as wind turbines 14a, 14b mounted thereon. On the centre 12 mast in the figure, two such wind turbines 14a, 14b are indicated. The one wind turbine 14b is mounted above the other wind turbine 14a on mast 12. Each wind turbine 14 includes turbine blades 16. As seen in a plan view, masts 12 are aligned, with each mast being partially pivotably supported on a hinge joint 18 of a base or foundation 20 on a surface 22. Surface 22 may be the ground or part of a floating structure, for example. The hinged support of each tower 12 is shown enlarged in Figs. 2 and 3. Such hinge joints are well-known.

GUYED DESIGN

For the construction of onshore multi-rotor wind power plants to be economically viable, such power plants must be built very large, generally with a height of 300 meters or more and a width that is similar or greater. This is challenging, and the turbine structure 10 comprises a great number of towers 12 standing next to each other and being held in place by a plurality of cables 40 anchored to the ground both on the front side (upwind) and on the back side. This is shown in Fig. 2. Typically, on each tower 12, nine or more turbine generators 14a, b may be arranged above each other on each tower/mast.

To obtain an efficient structure, a great number of such towers 12 are placed next to each other, each on a separate hinge 18. Two neighbouring towers 12 are connected to each other by horizontal and inclined steel or synthetic fibre tower cables 15. Neighbouring is understood to mean a tower 12 that is located closest to another tower 12. Preferably, each tower 12 may be constructed as a well-known truss structure having a quadrilateral plan section/outline. From the outer tower 12 of each row, moreover, a number of inclined guys or cables 17 are mounted descending sideways towards a fixture on the surface 22, so that an efficient truss bracing of the wind turbine rig is obtained. Hence, cables 17 are stretched in a direction across the prevailing wind direction. The cables 17 helps tensioning the towers in a sideways direction so that the tower cables 15 between each tower remain tensioned at all times. This set of tower cables 15 between each tower and the laterally stretched cables 17 are indicated in Fig. 1. Also, a set of similar cables is stretched between the towers from different heights descending towards a ground fixture from both the front and back sides of the rig.

When large structures are built in this manner, not only each individual tower but also the entire structure will move slightly back and forth as a result of the wind forces acting thereon. This will lead to very high stresses and fatigue especially of the horizontal beams of each tower. To avoid this, the problem is solved in the following manner:

Each tower is connected to a foundation 20 on the surface 22 by means of hinge joint 18. The foundation 20 may be made of concrete. The foundation 20 and surface 22 may be part of the same member or structure. In addition, the guys (not shown specifically in the drawings) running forward (upwind) and backwards have different pre-tensioning and stiffness/thickness. With this configuration, each tower 12 will rotate back and forth on hinge 18 as an approximately straight line and bending and internal stresses in the rig/structure is avoided. Still however, in some cases, there is a certain risk that the towers 12 and cables 17 may experience resonant oscillations with the subsequent fatigue and destruction of the structure. This can be overcome by adding dampening to the guy cables 17. In practice, this can be accomplished by mounting support cables perpendicularly to the guy cables and onto small foundations on the ground. To these support cables, a coil spring with an associated shock absorber is mounted. The entire damping system is comparable to the suspension system of a passenger car. This will stabilize the entire structure. Fig. 1 shows the sets of horizontal and inclined tower cables 15 between the towers 12, as well as the inclined lateral cables 17. Inclined guys/cables running forwardly (upwind) and backwardly from the towers towards a ground fixture are not shown.

CONSTRUCTION METHOD

It can be extremely challenging to build a structure in the terrain, on a mountain plateau, or similar places. Typically, the height of the structure will be 300 meters or more, and in reality no mobile crane systems exist that would be able to do such a job. The construction of such a turbine structure, therefore, may be carried out by helicopter in much the same way as power lines and tall towers are built today.

To this end, it would be of great advantage if virtually the entire turbine structure were made of aluminium or another light metal to save weight. As seen in the drawings, each tower 12 can have a quadrilateral outline. The entire structure must be designed in such a manner that it can be subdivided into several sections, each having a weight suitable for helicopter lifting, and said sections must then be able to be assembled by screwing. That is, the towers are composed of sections that are lifted in place one after the other up the height of the tower, whereafter the guys are mounted simultaneously. A guiding system must be designed that makes it unnecessary for personnel to be in the structure when the helicopter puts a section in place. This guiding system includes a self-locking snap lock system that automatically locks the tower part suspended from the helicopter to the tower under construction.

ELEVATOR SYSTEM

To make a multi-rotor wind power plant work, it is necessary to be able to maintain and replace turbines in a simple and fast manner. This can be accomplished by way of an elevator system able to serve all the turbines.

An elevator system of a multi-rotor wind power plant on a floating installation is known. This elevator system comprises an elevator mounted behind the front towers on which the turbines are fixed. The elevator is mounted between the towers and is hence located inside the structure. This system will work but it will be challenging at many locations to lift the turbines past the front towers and through the structure.

According to this patent application a number of essential changes are made which make the elevator system significantly simpler and more functional, and so that it will not interfere with the cables mounted between the towers.

This elevator system is described with reference to Figs. 4 and 5:

The turbines mounted on the towers are moved forward, so that the distance between the turbine blades and front side of the tower structure is increased. Typically, the distance may be 4 meters or more to make room for an elevator having a working platform that is movably anchored to the front side of the towers. When this change is made, it will be possible to mount the elevator system on the front side of the towers. It then becomes significantly easier to maintain or dismount/replace turbines or blades.

A novel lifting system for the elevator has been developed. The lift car 30 is mounted between two towers 12 but at the front edge of two juxtaposed towers 12, as shown in Figs.

4 and 5, and the elevator is used for maintenance or for replacing turbines on both sides (of the two adjacent towers 12). It is only necessary, therefore, for the lift car 30 to be mounted in every second tower interspace. The lift car 30 can be attached to the towers 12 by runners extending inside of partially closed rails/travelling paths (in beams which together form undercut guiding grooves) being part of the tower structure, particularly at the front corners 36, 38 (fig. 4) of the respective towers.

Inside these partially closed rails (grooves), a wire in each rail runs all the way up to the top of the towers, over a runner and back down inside a separate travelling path behind the partially closed rails.

Along the front side of the multi-rotor structure, on the ground, a rail track (which may constitute the working platform with its elevator) is mounted, on which rail track a wheeled carriage is located. The carriages may have a propulsion engine (powered hydraulically, electrically or by diesel/gasoline) or a winch arrangement for propulsion.

On this wheeled carriage there are mounted two large winches, 32 and 34, respectively, which are connectable to the cables running along the length of the towers. Additionally, there is also a lift car on top of the wheeled carriage. This lift car is also connectable to the cables suspended from the towers. The front part of the platform includes a fold-out grating/railing 33 which can be used as a base to facilitate the access to parts of the turbine and propellers protruding forwardly from the rig.

The elevator system works in the following manner: When a turbine is to be replaced or a service is to be performed, the wheeled carriage 31 is run to the proper tower interspace. The lifting wires (which are suspended along the length of the towers) are connected to the two winches on the wheeled carriage and to the lift car. In addition, the wheeled carriage must be secured, e.g. by cables, to the ground surface so that it is not lifted off the ground. The lifting wires are also connected to the lift car.

Now, a system exist that is able to lift the lift car all the way to the top of the towers and serve turbines attached to the towers on both sides of the lift car.

- On the lift cars there are mounted various equipment such as cranes, jacking systems and the like, which are used for replacing turbines or carrying out service.

-On the lift car, it is also advantageous to provide a small occupiable room and a toilet for the personnel who will be working from the lift car.

GUYED DESIGN ON A FLOATING INSTALLATION

If the turbine structure is to be established on a floating installation, a number of modifications need to be made. On a floating structure, the guy cables both in front of and behind the sail structure would have to end at approximately a single point. In this case, lateral fixation of the structure using guys will not be possible. This means that when the cables in front of and behind the structure end at a point in front of the structure and a point behind the structure, respectively, the guy cables will pull the juxtaposed towers towards the centre of the structure. To prevent this, relatively strong horizontal girders must be designed across the structure and the guy cables must be fixed to these horizontal girders or at the same height as the girders.

Also, on such a floating construction, pre-tensioning of the guy cables will be necessary. However, it is desirable for such pre-tensioning to be as small as possible to avoid having to oversize the turbine structure and the floater because of the high pre-tensioning.

A consequence of the use of a relatively low pretension is that the sail structure will move somewhat and be pushed backwards because of the wind. This, in turn, will result in that the guy cables on the back side of the structure becomes slack. This, combined with movements of the floating structure generated by waves, could easily cause the entire turbine structure to come into resonance with potentially disastrous results.

This can be solved by keeping the pretension of the rearmost cables constant. This can be accomplished hydraulically or electrically/mechanically, although perhaps the simplest solution would be to use weights attached to the rear cables.

Example:

There are 36 guy cables on the front side of the structure and 36 guy cables on the back side of the structure. Each cable has a Mean Breaking Load (MBL) of 400 tonnes. The maximum theoretical load to which each cable can be subjected is 100 tonnes.

The cables on the back side of the structure are each attached to a free-hanging weight having a weight of 8,000 kg. A stop is fitted so that the weights cannot be lifted higher than a certain point. The length of the cables is adapted so that when the weighs reach the highest point, the tower structure will be positioned vertically.

The cables on the front side are then pre-tensioned by 10 tonnes. This means that the free- hanging weights are pulled up to their highest point and then stopped by the stop, which prevents them from being lifted further. The cables on both the front and back sides of the structure now will have a pretension of 10 tonnes. When this structure is now subjected to strong head winds, the structure will be pushed slightly backwards, with the result that the weights attached to the cables behind the structure pull the cables down due to the weight of the weights and the cables on the back side of the structure will never experience a pretension of less than 8,000 kg. This system then may prevent the turbine structure from entering into resonance.

Claims

1.

A turbine structure (10) for a plurality of wind turbines (14, 14a, b), comprising: at least two upright towers (12) each of which is spaced from the others, each tower (12) being attached at the bottom thereof to an underlying foundation (20) via a hinge (18); wherein each tower (12) is connected to a neighbouring tower (12) by a number of tower cables (15) in order to ensure that the towers (12) remain parallel to each other in operation; the turbine structure (10) is secured by front and rear inclined cables (40) connecting the towers (12) to a base (22) in order to control the reciprocating motion of the turbine structure (10) about the hinges (18) against or with a prevailing wind direction; at the front side of each tower (12), a number of wind turbines (14, 14a, b) are provided one above the other along the length of the tower (12).

2.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to claim 1, wherein each outer tower (12) of a row of towers (12) is supported by one or more lateral cables (17) for bracing, and for keeping the towers (12) restricted approximately parallel to each other, and so that the tower cables (15) between two towers (12) are kept in tension.

3.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to claims 1 and 2, wherein the cables (40) on the front and back sides of the towers are individually pretensioned in such a manner that when pushed backwards by the wind, the towers will remain approximately aligned and excessive tension and subsequent fatigue of the turbine structure (10) are avoided, and the entire turbine structure (10) moves as a unit about the hinges (18).

4.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to claims 1 and 2, wherein support cables are mounted perpendicularly to the cables (40) and onto small foundations on the ground (22), each support cable comprising a coil spring having an associated shock absorber.

5.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to any of claims 1-4, wherein the towers (12) are constructed from an extruded light metal divided into sections suitable for helicopter lifting and wherein the sections are assembled by screwing.

6.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to any of claims 1-5, wherein each wind turbine (14, 14a,b) is mounted at a distance from the front side of its corresponding tower (12), enabling the establishment of an elevator arrangement on the front side of the tower (12) and inside the wind turbine (14, 14a, b).

7.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to any of the preceding claims, wherein a lift car (30) is mounted between two towers (12) for the maintenance or replacement of wind turbines (14, 14a, b) on both sides of two neighbouring towers (12), a said lift car (30) being mounted only in every second tower interspace.

8.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to claim 7, wherein the lift car (30) is attached to the towers (12) by runners extending inside partially closed rails/travelling paths being part of the turbine structure (10 ), and the lift carriage (30) is lifted and lowered by means of a wire driven by winch.

9.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to claims 7 and 8, wherein the lift car (30) is connected to existing wires suspended in partially closed rail systems on the front side of the towers, said wires running over runners at the top of the towers (12) and down on the back side or on one of the lateral sides of the towers (12) and on to a winch system able to lift or lower the lift car (30).

10.

The turbine structure (10) for a plurality of wind turbines (14, 14a, b) according to any of claims 7-9, wherein the lift car (30) is attached to a rail carriage able to move the lift car (30) sideways on the ground (20) relative to the turbine structure (10), on which rail carriage one or more winches have been established which are connected to the wires suspended from the towers (12).

11.

Use of the turbine structure (10) according to any of the preceding claims for application on onshore and offshore rig structures.