WO2007009464A1

WO2007009464A1 - Plant for exploiting wind energy at sea

Info

Publication number: WO2007009464A1
Application number: PCT/DK2006/000420
Authority: WO
Inventors: Paul Teichert
Original assignee: Pp Energy Aps
Priority date: 2005-07-19
Filing date: 2006-07-19
Publication date: 2007-01-25

Abstract

A plant for exploiting wind energy at sea, which plant (1) comprises a number of wind turbines (10, 12). The plant comprises one or more substantially longitudinal beams (2), a support structure (4, 6, 7) and means (24, 26, 38) for anchoring of the plant. The longitudinal beam(s) (2), whereon the wind turbines (10, 12) are placed, is/are mounted on the support structure. This is supplied with buoyancy elements (4), and the plant is adapted so that it can adjust depending on the direction of the wind. Thus the plant and said wind turbines will in a substantially natural way be aligned in the wind's eye. An increased efficiency can be obtained with the plant compared to traditional sea-based wind turbines, since servicing etc. does not depend on the state of the weather, but can be performed at any point in time. For servicing etc., containers can be transported to the plant, for example in advance, which containers can be elevated on to the plant by means of cranes, which containers can be stored in the plant and returned or exchanged according to needs.

Description

PLANT FOR EXPLOITING WIND ENERGY AT SEA

Technical field of the invention

The invention relates to a plant for exploiting wind energy at sea, which plant comprises a number of wind turbines.

Further, the invention relates to a method of controlling such a plant and a method of operating such a plant.

Background of the invention

In connection with production of energy, preferably electrical energy, by means of wind turbines there has been a widely-spread interest in recent years to establish wind turbine farms or clusters in water covered areas, in particular in sea areas, where there is a sufficiently low depth of the sea, so that foundations, etc. can be set up. The reason for establishing wind turbines at sea has been lack of suitable locations on land, i.e. places where there are suitable wind conditions, and where for instance environmental and/or economic reasons do not prevent the establishment.

In the recent years, sea-based wind turbine farms have been established for instance in Denmark and Germany, where there has been establishment at relatively near- shore areas, where the depth of water is not too deep. For example, about 14 - 20 kilometres northwest of Esbjerg at Horns Rev, a wind turbine farm with 80 wind turbines has been established which wind turbines have been arranged in five rows with 16 wind turbines each. There is a distance of 500 metres between the individual turbines and the rows are placed with a distance of 1000 metres. Thus, it is to be understood that a considerable area, namely about 37 square kilometres, is being occupied by this wind turbine farm. The reason that such a relatively large area is occupied is among others that the individual wind turbine should not give shade to each other. That is why a relatively large distance between the individual turbines is desired. Because of changing directions of the wind though, this will happen to a certain degree anyway.

As mentioned above, many sea-based wind turbine farms will be placed near land, so that undesired environmental impact occur to the population, such as noise effects, disturbing light reflections from rotor blades, and not to mention, in the view of many, the disadvantage of the view over the sea being destroyed by such a wind turbine farm.

Thus, it is a problem to localize further suitable locations for placing sea-based wind turbine farms.

Moreover, the sea-based wind turbine farms have a series of disadvantage caused by the space that they occupy, since for example pleasure boats and fishing vessels, etc. are not admitted in wind turbine farms.

A further disadvantage of these known wind turbine farms is the requirement to search for a sufficient number of suitable locations, where the depth of the sea is sufficiently low for setting up of the necessary foundations.

It is also a disadvantage that in connection with such wind turbine farms a very large part of the work has to be carried out at the chosen location, i.e. in the sea environment. Also, the experiences show that it is difficult and even impossible to be able to work in a relatively large part of the time because of the condition of the weather and the waves, which further increases the costs of establishing such wind turbine farms. A further disadvantage relates to its operation, whereby it would be

' necessary to make some servicing, maintenance work, repairs, etc. through the lifetime of such wind turbine farms. Here, the problem will arise that both personnel and necessary tools, spare parts, etc. would have to be transported to the individual wind turbines (one by one) by means of boats or ships, which again implies a strong dependency of the weather and sea waves, because there are large problems involved in transferring personnel and material to a sea-based wind turbine from a boat, unless the sea waves are insignificant. Also, experiences show that servicing, etc. is a rather significant cost in connection with sea-based wind turbine farms of the prior art, and further that the time, wherein electricity cannot be produced, is larger than expected, because it turns out that in a disproportionate part of the time such turbines are not productive, because service, repair, etc. are being waited for. Thus, an optimal yield is not obtained by such sea-based wind turbine farms through their lifetime.

In the prior art, floating offshore wind energy conversion systems have been disclosed. For example, WO 03/076800 discloses such a system, which according to an embodiment has a number of wind turbines placed on a tower and a semi- submersible hull for supporting the tower. The hull is attached to an anchor. The system is controlled in relation to the wind by controlling the rotors, thereby producing a yawing moment. However, the construction may be expected to be relatively unstable, considering the single submersible hull and the structure of the tower.

DE 201 11 441 Ul discloses a semi-submersible wind farm or wind park, where each wind turbine has its own tower, which is connected directly to a semi-submersible element. Thus, the number of wind turbines and thereby also the produced effect is relatively small, compared with the rather extensive support arrangement.

Furthermore, DE 102 19 062 Al discloses a system comprising a plurality of individual floating wind turbines which can be connected to each other in a cluster arrangement. Due to the nature of the construction, it will not be suitable for use at sea, where the wave activity will be such that the system will behave in an unstable manner. DE 198 46 796 Al also discloses a floating wind turbine system having a relatively small number of wind turbines and thereby a relatively small energy production. Furthermore, the system will due to its construction not be suitable for operation at e.g. high seas, i.e. at a certain distance from shore.

Further examples of offshore wind turbine systems are disclosed in DE 197 14 512 C2, DE 32 24 976 Al and WO 02/10589 Al .

However, neither of the above-mentioned prior art systems provides a plant for exploiting wind energy at sea, which will give a relatively high energy production in a cost-efficient manner, which will be able to operate at sea, also in adverse weather conditions, e.g. with high waves etc, and which will be readily serviceable in practically all weather conditions.

Thus, it is an object of the present invention to provide a plant for exploiting wind energy at sea, which provides an improvement in relation to the cited prior art.

Thus, it is also an object of the present invention to remedy the above mentioned disadvantages in connection with sea-based wind turbines.

In particular, it is an object of the present invention to provide a plant for production of wind energy at sea which allows a location thereof in areas where there otherwise is no other activity, i.e. where yachting, angling, commercial fishing, other leisure activities, regular navigation or other commercial navigation do not take place.

Further, it is an object of the present invention to provide such a plant which can be established in areas with considerable depths of the sea, i.e. in areas where it has not been considered to establish wind turbines with foundations set up in or on the sea bed. Further, it is an object of the present invention to provide such a plant whereby a relatively small number of wind turbines can achieve a relative large production of energy.

Further, it is an object with the present invention to provide such a plant which is relatively simple to establish compared with known sea-based wind turbine farms, and further which is relatively simple to scrap, even in an environmentally correct way, when the lifetime is exceeded.

Further, it is an object of the present invention to provide such a plant which is economical in operation, the costs and resources allocated for repair, service, etc. being lower than for known sea-based wind turbines, and for which an optimal energy yield is obtained through out the lifetime of the wind turbines, the effective operation time being larger than for known sea-based wind turbines.

These and others objects are fulfilled by the present invention, such as it will appear in larger detail in the following.

The invention

The invention relates to a plant for exploiting wind energy at sea, which plant comprises a number of wind turbines. According to the invention, the plant comprises:

- one or more substantially longitudinal beams or beam structures, - a support structure and

- means for anchoring the plant, wherein the longitudinal beam or beams, onto which the wind turbines are placed, are mounted onto the support structure, wherein the support structure is provided with buoyancy elements, and wherein the plant is arranged so that it can adjust its orientation in dependency of the direction of the wind, so that the plant and said wind turbines are substantially aligned in the wind's eye.

Hereby, it is obtained that the plant is designed as a floating structure which can be towed to suitable locations at sea, where there are suitable wind conditions and where the plant will not cause inconvenience to anybody. Thus, places can be found where there are no shipping routes, where there is no suitable fishing areas and which besides are so far away from shore that it is not areas of interest to yachting enthusiasts or other form for leisure activities at sea. Further, the plant can be placed so that it will not be harmful to animal life or bird life. Further, the plant can be placed so long from shore that the plant will not cause inconvenience to individuals on land so that there will be no problems to achieve the necessary approvals to establish the plant from an environmental point of view. The plant can thus be located far from the shore out of sight, which will be of benefit to the costal habitants, beach guests, nature lovers, etc.

Thus, a plant according the invention can be placed at locations having significant depths of the sea, for example at depths of 50 metres up to 200 metres or more.

As mentioned, the plant can adjust its orientation in dependency of the direction of the wind, so that the plant and the wind turbines are substantially aligned in the wind's eye, meaning that the wind turbines will substantially be facing the wind, i.e. with their axes essentially in parallel with the direction of the wind.

Further, by the invention it is achieved that the individual turbines will not give shade to each other or will not adversely affect each other in any other way, since the wind turbines will be placed next to each other, and since the plant will adjust itself so that the wind will come in substantially at the front. The rotors of the wind turbines will thus receive the optimal wind. A relatively large efficiency and a relatively large production of energy will be obtained with a relatively small number of wind turbines, which can be placed at a relatively small area.

An increased efficiency can be obtained by the plant compared to traditionally sea- based wind turbines, that for example may be placed in clusters or wind farms, since servicing etc. will not be dependent on the state of the weather but can be done at any time. For use in servicing etc. containers can be transported to the plant, for example in advance, which containers can be elevated to the plant by means of cranes, which containers can be stored in the plant and be returned or displaced as needed.

Further, the considerable advantage is obtained that all parts of the plant and even its continuous structure can be realised and even completed on shore, in a ship yard, or the like, so that the building phase will be very effective and resource efficient compared with known wind turbines, which exhibits the disadvantage that building must be done in situ as mentioned. Further, it is obtained that the operation costs will be reduced compared to known sea-based wind turbines, since it is not dependent on the weather in the same way when service, repair, etc. is to be performed, since the service personnel etc. can be expediently transported to the plant for example by means of helicopter, after which the work with the individual turbines can be done under orderly conditions and without being disturbed by possibly bad weather. Further, the necessary material can be transported expediently by ship to the plant in the same way as which it is presently known in connection with offshore drilling rigs and the like offshore-structures. Thus, known cranes, supply ships, and supply systems can be used as they are already known in the off-shore industry, including rough-sea compensated cranes (e.g. heave compensated cranes), by which containers etc. can be lifted on board on the plant from a ship even in relatively rough sea. All- in-all there will be obtained an improved efficiency and an improved yield through out the lifetime of the wind turbines for a plant according to the invention, since fewer resources must be used, including fewer man-hours for establishment and operation, and since the time whereby the individual turbine will not be able to produce electricity because they await servicing, repair, or the like, will be strongly reduced. It should also be noted that since the necessary equipment can be brought to the plant before servicing or optionally be present permanently to a certain degree, it is not required to wait for supply ships to dock at the plant before a servicing operation or a repair is undertaken, since personnel normally will be brought to the plant by helicopter irrespective of the weather, since the plant in itself normally will be stable so that a helicopter can land.

Expediently, as defined in claim 2, the longitudinal beam or beams may be fixed with respect to the support structure, whereby a relatively stable and secure structure is obtained. Here, it should be understood that the support structure will adjust itself in dependency of the direction of the wind. Further, it is to be understood that the mounting of the beam or the beams can be enhanced by means of usual techniques and by use of pylons, wires, and the like, such that it is known for example in building of bridges, etc.

Alternatively, such as defined in claim 3, the longitudinal beam or beams may be moveably mounted with respect to the support structure so that the longitudinal beam or beams can turn in dependency of the direction of the wind. It is to be understood the beam itself with mounted wind turbines can adjust itself in relation to the support structure with respect to the state of the wind, i.e. align itself in the wind's eye₃ while the support structure not necessarily needs to align itself in relation to the wind's eye.

Expediently, as defined in claim 4, the longitudinal beam or beams may be mounted so that they can rotate about an substantially vertical axis with respect to the support structure, optionally supported by a circular guide or the like, whereby the adjustment with respect to the direction of the wind can be obtained relatively easy, since the beam or beams can rotate or move around on the circular guide for example.

In this respect it is noted that the term beam or beam structure in this context shall be construed as any longitudinal structure or collection or combination of structures, which serves the purpose of carrying a number of wind turbines placed essentially next to each other, although not necessarily in a linear arrangement. Thus, also a structure comprising a number of beams or the like, connected to each other and each carrying one or more wind turbines shall be construed as constituting a beam structure for the purpose of this application.

In a further expedient embodiment, as defined in claim 5, said support structure may be provided with one or more buoyancy elements such as pontoons, or the like, designed so that ballast can be taken up or given off, in particular water which can be pumped in and/or out of the buoyancy elements. Hereby, it is obtained that the plant can be placed in a suitable depth in water, e.g. as a semi-submersible plant, since the ballasts in the buoyancy elements in a known manner can be adjusted so that a stable state is obtained, since there will be a balance between the buoyancy and the mass, that is carried by the buoyancy element. Hereby, it is obtained that the plant is more stable, since it will not be affected by the movements of the waves to the same degree as when the buoyancy elements are positioned in the upper layers of the water. Thus, the plant can be in a state with less or no ballast in the buoyancy elements, when it is to be towed, whereby it can be towed relatively easily, while it is brought into a stable condition with a suitable amount of ballast in the buoyancy elements, i.e. sea water, when it has been towed to a permanent location. It should be noted that the buoyancy elements may be used to further purposes as well, since they can be used for storing of fuel for example and thus be designed with tanks therefore. Other elements may be placed in the buoyancy elements as well.

In a further advantageous embodiment, such as defined in claim 6, said support structure may be designed so that said buoyancy elements form a support. Hereby a stable support of the plant itself, dependent of the form and size of an area defined by the position of the buoyancy elements, can be obtained. Further advantages are obtained, when these buoyancy elements are applied for storage of various media in connection with the plant. In connection with the plant, a system for the production of hydrogen by an excess production of electricity for example can be provided whereby the produced hydrogen can be stored expediently in the buoyancy elements, until it can be used, for example to production of electricity, or it can be transported away for other purposes.

Expediently, one of these buoyancy elements, in particular the middle element, may be displaced forward so that it will have a stabilizing effect during operation. The wind will push back the plant so that the front buoyancy element will be affected upwards. Because of the gravity of the water in this element, there will be a downward force optionally being regulated by pumping in more water when the wind blows heavily, and by pumping out water again when the wind calms. Thus, a plant can be obtained which will be stable under substantially all states of the weather and waves.

Various shapes of such a support area defined by the buoyancy elements may be provided.

As defined in claim 7, it may be provided with a vertex whereby a natural mooring point is obtained so that adjustment of the plant can take place with respect to the wind and current.

Further, as defined in claim 8, said support area may be provided with backwards angled sides so that the adjustment with respect to wind and current is further improved.

Further, as defined in claim 9, said support area may be provided in a substantially triangular form.

Alternatively, as defined in claim 10, said support area may be provided in a substantially quadrangular form. Further, as defined in claim 11₅ said support area may be provided in a substantially circular form.

As defined in claim 12, said support structure may be provided with two or more substantially vertical towers connected to the longitudinal beam or beams so that this/these are positioned in a substantially horizontal level over the support structure.

Hereby, a connection between the support structure, including its buoyancy elements, and the beam or beams themselves is established in an expedient way. Further, said structures, including the beam or beams, may preferably serve as crew's quarters for the service personnel, etc., workshop facilities, storage facilities, for example for storing service products, spare parts, etc.

As defined in claim 13, said two or more substantially vertical towers or columns may each be connected to a buoyancy element. Hereby, in a further expedient way, there is provided a connection between the buoyancy elements of the support structure and the beam or beams themselves. It is to be understood that two or more towers or columns may be used for each pontoon, where this is preferable.

As defined in claim 14, said substantially vertical towers may expediently have such a height that the longitudinal beam or beams are located above the surface of the sea, also when said buoyancy elements are provided with ballast. Hereby, in an expedient way, connection is provided between the support structure, including its buoyancy elements, and the beam or beams themselves so that the wind turbines are lifted up in a suitable height, also when the buoyancy elements are lowered down into a suitable level below the surface of the water for stability reasons during operation.

In a further advantageous embodiment, as defined in claim 15, a number of wind turbines may be mounted on or along said substantially longitudinal beam or beams, for example with mutually uniform distances, so that an optimal position of the wind turbines with respect to the direction of the wind can be obtained. It should be noted that since the plant adjust automatically with respect to the direction of the wind, the wind turbines may be provided with fixed adjusted nacelles so that an economical construction of the wind turbines is obtained. Further, the wind turbines could be placed with an optimal minimum distance so that the size of the plant can be minimized.

Further, it should be noted that the positioning of the wind turbines at the beam provides the further option of utilizing the beam as a means in service and repair, since crane tools etc. which uses the beam as a transport way, etc. can be provided. Such a crane may thus be placed in any position along the beam or beams.

Expediently, as defined in claim 16, said wind turbines may comprise wind turbine towers mounted on said substantially longitudinal beam or beams, and which extends upwards.

Further, as defined in claim 17, said wind turbines may comprise wind turbine towers mounted on said substantially longitudinal beam or beams, and which extends downwards. Hereby, also the area below the beam or beams is used for production of energy.

In a particularly expedient embodiment, as defined in claim 18, said wind turbines may comprise wind turbine towers mounted on or along said substantially longitudinal beam or beams, and which extends both upwards as well as downwards with respect to the beam, which wind turbine towers carry rotor blades, nacelles, etc. both above and below the beam. Hereby a particularly effective structure is obtained whereby optimization of the use of space and consumption of material is obtained.

In an advantageous embodiment, as defined in claim 19, said wind turbine towers may be mounted so on said substantially longitudinal beam or beams that the wind turbine towers can pivot with respect to the vertical plane. It should be understood that the wind turbine towers can pivot a small angle forward or backwards, for example to compensate for movements of the waves. In another advantageous embodiment, as defined in claim 20, said wind turbines, preferably the nacelles on these, may pivot in the vertical plane with respect to the wind turbine towers. It should be understood that the wind turbines and preferably the nacelles on these can pivot a relatively small angle forward or backwards, for example to compensate for movements of the waves.

In a further advantageous embodiment, as defined in claim 21, said wind turbines, preferably the nacelles on these, may rotate in the horizontal plane with respect to the wind turbine towers, said angle of rotation being small though. Hereby, the nacelles are aligned with the wind, if the plant itself should not be completely aligned with the wind, or in the time interval lapsed while the plant is in process of aligning due to a shift in wind.

According to a further expedient embodiment, as defined in claim 22, the plant may comprise two or more substantially longitudinal beams each being mounted with wind turbines.

As defined in claim 23, such beams may be placed above each other, connected with vertical towers, pylons, columns or similar known means, just as known means may be used for stabilising, such as wires, pylons, etc.

Further, as defined in claim 24, the two or more substantially longitudinal beams may be placed end to end of each other.

Further, as defined in claim 25, said two or more substantially longitudinal beams may each be provided with a support structure with buoyancy elements and be placed end to end of each other, a flexible connection being arranged between the beams. It should be understood that two or more identical plants may be utilized, each with pontoons, anchoring, wind turbines, etc., each being towed to the site of operation and here connected to each other with a flexible connection so that the plants can move with respect to each other, for example with respect to the movements of the waves, but so that there can ^"be cable connections from one plant to the next, and so that the personnel can move from one plant to the next plant.

As defined in claim 26, said means for anchoring of the plant may be provided so that the plant can align in a direction with respect to an anchoring point on or at the sea bed, which direction depends on the direction of the wind. Thus, there may be arranged a substantially point-type anchoring to the. sea bed, which can be provided in a known way.

Expediently, said means for anchoring, as defined in claim 27, may comprise, a connection to the support structure or a buoyancy element thereon, so that the adjustment of the plant with respect to the direction of the wind hereby is relieved to a high degree.

Further, advantageously as defined in claim 28, said connection to the support structure or a buoyancy element thereon may be placed substantially in front of the middle of the transverse beam or beams, preferably at a vertex of the plant's support area. There may be a plurality of connection points on the plant and a plurality of anchoring chains, or the like, when only the connections are distributed about the middle of the plant and are connected to a point in front of the middle of the plant or the beam or beams.

According to a further aspect of the invention, as defined in claim 29, said means for anchoring the plant may comprise two or more anchoring points, and the plant may be connected to these by means of connections, for example anchoring cables of which at least one is arranged so that the length can be controlled.

Hereby the plant may be controlled so that it can be placed with wind turbines placed optimally with respect to the wind, in spite of for example strong currents deviating from the direction of the wind. Further means for manoeuvring the plant with respect to directions of the wind and/or the current may be various measuring devices for measuring the state of wind, current, and other conditions which may be of importance for operation and control of the plant. Thus, measuring station for measuring the strength of the wind and its direction, etc. may be positioned at one or more points on the plant and in a distance from the plant. When used in a distance from the plant, the measuring results can be applied to estimate the state of the plant itself in a period to come.

Expediently, as defined in claim 30, said means for anchoring of the plant may comprise a primary anchoring and one, two, three, or more secondary anchorings.

The primary anchoring may be constituted by the normal anchor block, to which for example the electrical connection is led, and this or these secondary anchorings may be connected to the plant, for example to outer points of the plant with for example cables, the length of which may be controlled so that the plant can be turned by appropriate control and further be placed appropriately.

In a further expedient embodiment, as defined in claim 31 , the plant may comprise one or more anchor winches connected to one or more of said anchoring points by means of said connections, for example anchor cables.

Hereby, the length of said connections, and thereby the placing of the plant, may be expediently controlled. Said anchor winches may be placed in connection with said anchoring points, but they will preferably be placed onto the plant itself, for example in connection with pontoons, outer points, or the like of the plant. It is clear that two or more anchor winches can be placed on a single pontoon, or the like, which will operate on each of its own anchor cables, which for instance can be connected to each of its own anchor block, but it is also clear that each anchor winch or windlass can be placed on its own, for example on different pontoons. Advantageously, as defined in claim 32, the plant may comprise connection means to an electrical cable which electrical cable constitutes an energy connection to a plant on land, and which can be placed in connection with an anchoring of the plant.

In a further expedient embodiment, as defined in claim 33, the plant may comprise driven means for use in connection with adjusting the plant, which driven means can comprise propellers. Hereby it is obtained that an optimal adjustment of the plant can be obtained; said means being helpful in adjusting the plant precisely and thus supplement the natural adjustment of the plant. The driven means are controlled by a central control, which for example can receive input from wind measuring devices, etc.

Preferably, as defined in claim 34, said driven means secondary may be operated by electromotors, combustion motors such as diesel motors, or similar motors.

Further, as defined in claim 35, said driven means may comprise control propellers, preferably placed in connection with one or more of said buoyancy elements and optionally in form of 360 degrees rotatable propeller drives such as those known from ships, etc. for example in form of bow propellers. Such control propellers may be placed at each of the buoyancy elements, or only at some of these. Also, a plurality of control propellers can be mounted at one or more of the buoyancy elements.

In a further expedient embodiment, as defined in claim 36, said substantially longitudinal beams may be provided as a tubular body, i.e. a body having an internal cavity but which can be provided in an infinite number of ways, and which can be used as passageway, living tunnel, or working tunnel, and as crew's quarters, workshop facilities, storage facilities, etc;, and which may be adapted with containers or similar modules for these purposes. Further, it should be noted that the plant may be equipped with a landing platform for helicopters, so that personnel for servicing, etc. easily can be transported out to the plant. Further, the plant may be provided with lifts and the like in the vertical towers.

In a particularly advantageous embodiment, as defined in claim 37, the plant may comprise means for receiving and handling containers or similar modules, which containers or the like for example are transported out with ship to the plant, which ship is anchored to the plant in a known manner, so that containers can be transferred to or returned from the plant. Further, containers or the like can be transferred from the plant to the ship, for examples containers which have been used, and/or containers replacing new containers with supplies.

In a further advantageous embodiment, as defined in claim 38, the plant may comprise means for receiving and handling articles such as containers, wind turbine parts, spare parts, etc., which means for example may comprise cranes and/or winches for unloading and/or loading. Hereby supplies, spare parts, personnel facilities, etc., may easily and effectively be transferred to the plant, since such crane systems for handling articles in rough sea are already known and can immediately be used in connection with the invention. The application of containers is particularly advantageous, since these can easily be handled, can easily be placed and transported in the plant itself, for example in the beam structure using the means commonly used in the industry today. Thus, the task of being able to supply the plant according to the invention with the necessary supplies could preferably be solved in an optimal way, and so that the plant in an optimal way could perform its primary function, viz. to produce energy, without unnecessary stop of operation. Further, it should be noted that said cranes or the like which can be applied for loading and unloading of containers, spare parts, etc. also may be applied for servicing the wind turbines on the plant, for example by exchanging of parts or inspecting and/or other work on the wind turbines.

In still an advantageous embodiment, as defined in claim 39, the plant may comprise solar cells and/or diesel generator plants, for example for supply of electricity for the control equipment and emergency equipment in calm periods. Other energy forms may be used so that the plant can function as a total self supplying unity in an environmentally correct way.

According to further aspects of the invention, as defined in claim 40, the plant may comprise means for exploiting the energy of waves and/or currents, for example wave mechanisms, turbines, or the like.

Thus, the plant may comprise an apparatus for exploiting the energy of waves, which apparatus can be arranged in various ways, as known within the field of wave energy. Such an apparatus can for example be mounted on or in pontoons, connected to the support structure or be placed in another way. Also, mechanisms can be arranged for exploiting the energy of the current, which mechanisms can also be mounted on or in pontoons connected to the support structure or be placed in another way.

According to a further expedient embodiment, as defined in claim 41, the plant may comprise means for storing energy, for example in form of means to produce and store hydrogen, for example in said buoyancy elements, pontoons, or the like.

Thus, for example hydrogen can be produced which can be stored in tanks such as it is known from other plants, when for example more electric energy is produced that can be sold to distribution companies, etc. considering the market conditions. Such tanks can be placed in pontoons or in other parts of the structure elements of the plant. The produced hydrogen can later be exploited for the production of for example electrical energy, either on the plant or some where else, for example transported into shore. Other ways of storing the energy is naturally also possible.

It should be understood that a plant according to the invention may be produced and assembled completely in a shipyard, after which it can be towed to sea, where it is placed in a permanent location. More modules or plants can be towed individually and assembled on the site of operation. Further, a plant according to the invention could be applied as a mobile energy supply plant, and it would be very easy to scrap or take it out of operation, when it is desired, after which it can be scrapped in a conventional manner, for example in a shipyard, contrary to existing sea-based wind turbine farms.

Furthermore, the invention relates to a method of controlling a plant for exploiting wind energy at sea which plant comprises a number of wind turbines according to one or more of claims 1 — 41, whereby the plant is arranged so that the orientation of the plant is controlled in dependency of the direction of the wind, so that the plant and said wind turbines are substantially aligned in the wind's eye, whereby drive means are provided for facilitating and/or enhancing said control of the orientation of the plant, whereby measurement means provide input signals for a central control, which effects a control of said drive means.

Hereby an optimal adjustment of the plant can be achieved, since said drive means ca assist in adjusting the plant precisely and thus supplement the natural adjustment of the plant. The drive means are controlled by a central control, which for example can receive input from wind measuring devices, etc.

Preferably, as characterized in claim 43, said drive means may comprise propeller drive means.

According to a further advantageous embodiment, as characterized in claim 44, said drive means may comprise means for controlling the effective length of one or more connections, e.g. anchor cables, from the plant to one or more anchoring points such as for example anchor blocks.

Hereby it is obtained that the plant may be controlled so that it can be placed with wind turbines placed optimally with respect to the wind, in spite of for example strong currents deviating from the direction of the wind. Furthermore, it is hereby achieved that the plant may be withheld in e.g. a position in spite, of e.g. a strong current in an energy saving manner since the connections, e.g. anchor cables, or rather the drive means herefore can be arrested at the appropriate length(s), whereby it will not be necessary to use power to maintain the desired position

Expediently, as characterized in claim 45, said measurement means may provide signals relating to wind and current directions and/or speeds.

Furthermore, as characterized in claim 46, said measurement means may provide signals relating to wind and current directions and/or speeds at the plant and at one or more positions located at a distance from the plant.

Hereby, it is obtained that for example measuring stations for measuring the strength of the wind and its direction, etc. may be positioned at one or more points in a distance from the plant, whereby the measurements can be applied to estimate the condition that will apply at the position, where the plant itself is located in a period to come.

The invention also relates to a method of operating a plant for exploiting wind energy at sea, which plant comprises a number of wind turbines mounted on one or more substantially longitudinal beams or similar structures, said plant further comprising a semi-submersible support structure having buoyancy elements and means for anchoring the plant, whereby the plant is arranged so that it can adjust its orientation in dependency of the direction of the wind, whereby said substantially longitudinal beam(s) or similar structures is/are adapted for accommodating containers or similar modules for supplying necessary equipment, spare parts, etc., whereby said containers or similar modules are hoisted from a supply vessel onto said plant, when supplied, and lowered again to a supply vessel when appropriate.

Hereby, it is obtained that the operation and service of the plant can be performed in an expedient and cost-efficient manner, since necessities can be transported to the plant without consideration of weather, rough sea, etc. Hoisting may be performed by means of cranes and winches of known types, for example such that are used in offshore oil plants and gas plants, where wave-compensated (heave compensated) winches can be applied, whereby unloading and loading of ships can be done in spite of the rough sea. Hereby supplies, spare parts, personnel facilities, etc., may easily and effectively be transferred to the plant, since such crane systems for handling articles in rough sea are already known and can immediately be used in connection with the invention. The application of containers is particularly advantageous, since these can easily be handled, can easily be placed and transported in the plant itself, for example in the beam structure using the means commonly used in the industry today. Thus, the task of being able to supply the plant according to the invention with the necessary supplies could preferably be solved in an optimal way, and so that the plant in an optimal way could perform its primary function, viz. to produce energy, without unnecessary stop of operation. Containers can be in the plant in longer periods or all the time, but they can also be transported to the plant when there is servicing, repair or the like, where personnel have to be present for a certain limited period, for example for a week, two weeks, or more, and following which the containers can be transported to shore again (or to another plant). Hereby, an effective servicing is obtained whereby the personnel can work effectively over a period of time, and whereby large time consumption for transportation of personnel is avoided. The personnel can be transported out to the plant by a helicopter for example, after which the personnel can concentrate on the work to be done, as all necessities have been transported out to the plant in advance. Subsequently, the personnel can be flown back to shore, after which used containers, etc. can be removed, when this is appropriate.

Advantageously, as specified in claim 48, said one or more substantially longitudinal beams or similar structures may be provided as tubular bodies or the like, which can be used as a passageway or working tunnel, and as crew's quarters, workshop facilities, storage facilities, etc., and which can be adapted with said containers or similar modules. Hereby, containers or similar modules adapted for accommodation of personnel such as it is known from construction sites can be used, for example a modular system completed with sleeping facilities, lavatory facilities, kitchen, living room, etc. Thus, there will be no need for transporting personnel to and from the plant for example every day while a service job is being performed.

Expediently, as specified in claim 49, said plant may comprise means for receiving and handling articles such as containers, wind turbine parts, spare parts, etc., which means comprises cranes and/or winches for unloading or loading. It should be noted that said cranes or the like which can be applied for loading and unloading of containers, spare parts, etc. also may be applied for servicing the wind turbines on the plant, for example by exchanging of parts or inspecting and/or other work on the wind turbines.

Brief description of the drawings

In the following, the invention is explained in more details with reference to the drawings, wherein

fig. 1 shows a front view of a plant according a first embodiment of the invention, fig. 2 shows a top view of the same embodiment as shown in fig. 1, fig. 3 shows a perspective view of a model of a plant according to an embodiment of the invention, fig. 4a — 4d show a schematic view of various possible basic constructions of a plant according to the invention, fig. 5 shows in a similar way a further embodiment of the invention, fig. 6 shows a side view of an anchor arrangement according to a still further embodiment of the invention, fig. 7 shows an end view of the plant shown in figs. 1 and 2, fig. 8 shows an example of a plant with two transverse beams placed above each other, fig. 9 shows an example of a plant wherein two (or more) plants are placed side by side and end to end of each other, fig. 10 - 13 show a further embodiment of the invention where among others a number of anchorings are applied for controlling the plant, and fig. 14 shows a further embodiment of a plant according to the invention for illustrating servicing possibilities, etc.

Detailed description

In fig. 1 there is shown a front view of a plant 1, which is also called a turbine rig, according to a first embodiment of the invention. Thus there is shown that the plant comprises a longitudinal beam (or boom) 2 which can be substantially linear or which can have other shapes, such as it will be described later. This beam 2 can be in form of a tube or otherwise hollow and it can have a circular cross section, a quadrangular cross section, or other shapes. Furthermore, the beam may comprise a number of components, such as girders, lattices, pipes, rods, etc. making up the beam or part of the beam.

The beam 2 carries a number of buoyancy elements or pontoons 4. Thus, it is shown in fig. 1 that three of these are applied, but other numbers can be used, both fewer as well as more, for example four, five, six, or seven, etc. The buoyancy elements 4 and the beam 2 are connected by means of elements such as towers 6 and there can be provided various stiffenings of the structure such as girders 14 as shown, wires, etc. such as it is known for example from construction of bridges, deep-sea oil and gas platforms, etc.

Further, it is shown that the mid/middle pontoon 4 is connected by means of a connection element 7, the middle pontoon being displaced forward with respect to the plant, such as it is shown in fig.2. Thus there can be a connection from this pontoon to the beam in form of a tilted tower that extends to the beam.

On the longitudinal beam 2 there are placed a series of wind turbines 10 and 12 next to each other, a number of wind turbine towers 8 being connected with the beam 2. These towers can extend above the beam 2 and carry wind turbines 10. Instead of or preferably simultaneously, the wind turbine towers 8 can extend down under the beam 2 and also here carry wind turbines 12. These wind turbines can be designed in a normal manner, i.e. in the same way as conventional wind turbines with a generator, gear, electric equipment, etc. in a nacelle 22 which also carries the rotor blades. Thus, the nacelles can be adapted so that they rotate with respect to the direction of the wind, but according to a preferred embodiment, such as it shall be described later, the nacelles 22 are placed so that they do not rotate with respect to the turbine towers 8 according to the direction of the wind. On the other hand, the nacelles 2 can pivot in the vertical plane, which will be described later.

As shown in fig. 1 a plant can have a width of about 500 metres for example corresponding to the length of the beam 2 so that there can be about 100 meters between the wind turbines.

It should be understood that it is a floatable plant, carried by the buoyancy of buoyancy elements or pontoons in the water. As shown in fig. 1, the complete buoyancy of the pontoons is used during towing, where the plant is lying high in the water such as shown by the surface of the sea 20a. When the plant 1 is brought out to the production site, water is pumped or let into the buoyancy elements 4 until there is obtained such a balance between buoyancy and mass that the buoyancy elements are located in a predetermined level below the surface of the sea 20b, so that now the plant 1 will be in a very stable state, where it is essentially not affected by movements of waves, etc. As shown in fig.2 the plant 1 can be anchored by means of a coupling arrangement 24 on the middle pontoon 4, which can be displaced forward as mentioned earlier. Here the plant can be anchored with for example an anchor chain 26, and there can also be mounted a connection in form of a cable 28, which serves to bring the energy produced into shore. There can be more anchor chains or the like that are connected to a plurality of points on the plant, for example also to pontoons, which lie next to the middle pontoon. Generally, the connections will be distributed so that the connection points lie forward of the middle or the centre of the plant, and so that the anchoring point for example on the sea bed is located in front of the middle of the plant.

For use in the manoeuvring and operation of the plant with respect to the direction of the wind and/or current, measuring devices for measuring conditions of wind, current and other relations can be placed on the plant itself. Further, such devices can be placed in a certain distance from the plant, i.e. measuring stations for measuring strength and direction of wind and/or current, etc. which measuring stations can be placed on buoys or the like, placed for example in a distance of 500 metres — 1000 metres or still further, for example up to several kilometres from the plant in different directions, and being adapted so that there can be communication, preferably wireless with the plant. The measuring results can be used to predict states at the plant itself in a period to come when such measuring stations are applied in a distance from the plant, so that gusts, wave changes, etc. can be predicted, whereby the plant can adapt accordingly.

Moreover, in fig. 2 it is shown that the plant 1 can be provided with a landing site for helicopters - or a heliport - 30, and also in this connection it should be mentioned that the used elements are of such dimensions that for example in one or more of the towers 6 there can be accommodated lifts, and that the beam 2 can have crew's quarters, living facilities for personnel such as cabins, etc, just as there can be workshops facilities and service facilities. Further, it should be noted that on the top of the beam 2 there can be placed lifting facilities in form of for example a crane or the like, that can run along the beam 2 and which can be used in servicing the wind turbines 10 above the beam 2 as well as the wind turbine 12 below the beam 2. Further, such a crane can be applied at unloading and loading of service boats etc.

It should be understood;, cf. fig. 2, that a plant according to the invention will adjust itself in dependency of the wind, since because of the anchoring and the effects of the wind on the wind turbines on the beam, the plant will rotate about the anchoring so that the plant always will be directed against the wind, when smaller short changes in the direction of the wind are neglected.

A plant according to the invention is shown in a perspective view in a model in fig. 3. It is shown on the model that because of the anchoring in front of the middle of the plant or rather the transverse beam 2, the plant will adjust itself according to the direction of the wind. Also, with reference to fig. 3, it should be noted that the pontoons 4 because of the submerged state and because of their mass implies that the plant will be stable in the water. The effect of the wind on the plant in a direction backwards will be restricted in particular by the front pontoon, which will be affected upward by such an effect. The position of the plant can be adjusted by controlling the content of the ballast, i.e. water, in this pontoon, when there is a permanent effect by the wind. More water can be pumped into the pontoon, when the wind blows hard, so that its mass is increased, whereby it will be affected downward. This is reversed when the wind calms again.

Further, in fig. 1 it is shown that propellers 18 can be placed on the pontoons 4, for example under or in the bottom thereof. These can be driven in various ways, for example by means of auxiliary engines such as diesel motors or the like, but they can also be units powered by electricity. These propellers 18 can be rotatable and can preferably be rotated 360° so that the pontoons can be pushed and controlled in any direction using these. Thus, these propellers 18 can be used to get the plant adjusted in the direction of the wind. This can take place when the wind is so weak that the effect of the sea currents is significant, but the propellers can also be used to quickly adjust the plant in the direction in the wind.

It should be understood that the plant preferably will be adjusted in a natural manner by the forces of nature, but that the adjustment can take place in cooperation between the forces of nature and the function of the propeilers. The propellers will be controlled by a central control, which among others can receive input from anemometers, current meters, etc.

In fig. 1 it is shown that there can be a propeller 18 on each pontoon, but there can be more propellers on each pontoon, and there need not necessarily be propellers on each pontoon.

In fig. 4a-4d there is generally shown different constructions which are possible in connection with the invention.

In fig, 4a there is shown a construction corresponding to that shown in figs. 1 and 2. The middle or foremost pontoon is designated 4b and the others are designated 4a. As explained earlier, an anchoring is arranged so that it is placed in front of the middle of the plant and possible to the pontoon 4b.

In fig. 4b there is shown a similar construction where the three pontoons are placed so that they form a triangle. This triangle will define the area by means of which the plant itself is being supported. The larger this support area is, the more stable the plant will lie in the water. In fig.4b it is shown that the beam 2 can have a construction where a backwards angled part T is associated with each side.

Fig.4c shows a similar construction but where the beam 2 consists of two parts T that forms a vertex. It should be understood that wind turbines are placed on these parts 2' next to each other and so that they point into the direction of the wind. Fig.4d shows also a construction with three pontoons, but where a beam construction is applied with a substantial quadrangular shape, and where wind turbines can be placed on either the front beam and/or the back beam.

Fig. 5 shows a general view of a further embodiment. Here there are used for example four pontoons 4a and 4b. These are carrying a circular rotational guide 32 that carries the beam 2 with mounted wind turbines 10. For this construction the pontoons, etc. do not need to move in dependency of the direction of the wind, since the beam 2 is placed so that it can rotate as shown by the double arrow 34 which illustrates that the beam can adjust itself when the wind changes direction. It should be understood that the plant itself with pontoons will change position in dependency of the direction of the wind and current, when this construction is anchored, e.g. to the front pontoon 4b_s but that the beam 2 itself first and foremost will adjust itself according to the wind.

In fig. 6 there is shown a side view of an anchoring arrangement according to a further embodiment of the invention. There is shown the middle or foremost pontoon 4b, which is submerged below the surface of the sea 2Ob₅ i.e. the plant being in an operational position. As shown the anchoring chain 26 can be led to an anchoring point 38 on the sea bed 36, which anchoring point for example can be in form of a concrete block, or the like. The electrical cable 28 can be led along with the anchoring chain 26 to the bed 36, where it can be led further to shore in a normal way for sea cables. Alternatively, as shown there can be used a floatable construction 40 which can be in form of a connection island or transformer island, and to which the cable 28 is led from the plant itself. This cable can optionally be kept floating by floats or the like on its way to the floatable construction 40. From here a connection cable 42 is led down to the anchoring point 42, from where it is led 44 to shore.

It should be understood that for the shown arrangements there is a possibility for the plant to turn about the anchoring point 38 or optionally about the anchoring chain itself 26 which because of its mass serves to hold the plant in place. There must be a possibility for the electrical connection to follow these movements without being damaged or become tangled with or about the anchoring chain 26. These problems can be solved by the described arrangements. It should be understood that the general control system of the plant can assist in controlling whether the connection cable becomes twisted around the anchoring chain etc. Further, connection means can be provided which allows rotation of cables etc., such as rotating current collectors etc.

In fig. 7 there is shown an end view of a plant corresponding to that shown in figs. 1 and 2. It should be understood that because of movements of the waves, minor movements of the plant can occur in the forward and backwards directions, whereas the plant will not rock sideways. For accommodating these minor rocking movements the wind turbine towers 8 can be carried on the beam 2 such that they can pivot in a small angle with respect to the vertical direction, i.e. in the plane for fig. 7, i.e. corresponding to movement of a pendulum. Alternatively, each individual nacelle 22 can be placed on the wind turbine towers 8 so that they can pivot in a small angle such as shown in fig. 7, whereby the wind will come directly onto the rotor blades, even during movements of waves. The movements of the nacelles or the wind turbine towers can be gyroscopically controlled.

Further, it should be noted that for a particular embodiment, the nacelles 22 could also move sideways in a small angle, for example about 20 degrees to the right and to the left with respect to a middle position. Hereby, the wind turbines are adjusted in these angles, for example if the plant itself is not completely aligned in the wind's eye, which can occur if there is a very strong side current, or while the plant is in the process of adjusting itself following a shift in wind, which can occur.

In figs. 8 and 9 there is shown examples of plants according to the invention where there are more transverse beams or turbine rigs present. Thus, in fig. 8 there is shown a plant as disclosed in connection with fig. 1 but where there is placed a further beam 2 above the first beam, the vertical towers 6 being extended upwards. The two beams 2 are in principle designed in the same way and with the same number of wind turbines 10 and 12. It is to be understood that there can be more decks or layers of beams and wind turbines on a plant.

In fig. 9 there is shown how two in principle identical plants can be connected into one plant, when both are towed out to a production site. Here both are anchored next to each other, a connection being established to a point lying in front of the middle of the assembled plant 1. This can for example be a connection to the two middle pontoons 4, or there can be more or other connections, as long as these are distributed about the middle of the plant, i.e. so that the connection points are located in front of the middle of the plant. The two beams 2 are brought together by means of a flexible connection 46, which can be in form of a tube or a bellow which allows that the two beams can be angled with respect to each other, for example caused by movements of waves. Cables, etc. can be led through this connection 46 and it is also possible for service personnel etc. to move through it. It should be understood that there can be more modules connecting each other as described.

In fig. 10 there is illustrated a plant according to a further embodiment of the invention wherein the plant 1 is schematically shown, comprising a number of pontoons 4 and a wind turbine beam 2. It should be understood that the plant 1 can be realized in a multitude of ways by using different number of pontoons 4 and beams 2 and with various forms thereof, which is of less or no importance for this embodiment of the invention, such as it will be explained in the following.

As explained earlier, the plant can be moored with a cable 26 to an anchoring point 38, such as an anchoring block, but the plant can further be anchored to one or more secondary anchoring blocks 50 with anchor cables 52 and 54 as shown in fig, 10.

This is of particular importance if there can be deviations between directions of wind and current, in which case the plant 1 would have difficulties aligning itself in the wind's eye, unless propellers, or the like, are used to control the plant, such as it is explained above. In connection with secondary anchorings 50 the plant 1 can be provided with one or more winches 56 and 58, which each can be placed on its own pontoon 4 for example as shown in fig. 10, and so that they can pull in each anchor cable 52 and 53 so that it can be obtained that the plant will always be optimal with respect to the wind by controlling the length of the these cables. This is illustrated in fig. 10 and figs. 11 and 12 showing various combinations of directions of wind and current. As it is show, an optimal placing of the plant 1 can be obtained by a suitable control of these winches 56 and 58.

Also, as shown in fig.. 13 there can be placed a further anchor cable 26' to the primary anchor block 38 so that the length of this can be controlled by the winch 58. Further, a winch 60 can be placed on the pontoon 4, to which the anchor cable 26 is connected so that the length of this can also be controlled and participate in the control of the placing, e.g. positioning as regards direction and location, of the plant 1.

It is clear that there can be two secondary anchor blocks instead of a single secondary anchor block 50, for example connected to each its anchor cable 52 and 54. It is also clear that there can be more than two such anchor blocks 50, for example three, four, five, etc. just as the number of anchor cables 52, 54, 26, 26' can vary.

Fig. 14 shows an embodiment of a plant according to the invention for illustration of the service aspect etc. according to the invention. Generally, the plant 1 is built as previously described, i.e. with a number of buoyancy elements or pontoons 4, which are submerged during operation of the plant, and which carries a longitudinal construction or beam 2 by means of towers 6 or the like, on which construction or beam a number of turbine towers 8 with turbines 10 and 12 are placed. The plant can be anchored by anchor cables 26 as previous described so that it can adjust itself in dependency of the wind and/or it can be controlled such as it is also described above.

The plant 1 can be provided with one, or as shown, more cranes 62, winches, or the like, which can be mounted on the beam construction 2. As mentioned, such cranes

62 can be used for servicing the wind turbines 10 and 12, for example for mounting or demounting the individual elements such as rotor blades, gear boxes, generators, etc, and also the cranes 62 can be moved along the beam construction for example so that a single crane can service a plurality of wind turbines.

Further these cranes 62 can be used to lift material up to the plant or down from the plant, for example supplies, spare parts, wind turbine components, tools, etc. Preferably containers or other forms of modular transport devices are used, which preferably can be transported out to the plant 1 by ships, such as shown by the ship 70, which schematically is shown at the middle pontoon 4 in fig. 14. This ship, which can be a supply ship for example as it is known from the offshore oil industry, can be loaded with a number of containers 72 as shown, which in a simple manner can be lifted up to the beam construction 2 by means of a crane 62. Also, corresponding containers can be lifted down on the ship 70 by means of the cranes 62, for example containers which previously have been transported to the plant and which are now being replaced by fresh containers. It can be arranged that the containers with content of spare parts, supplies for the personnel, or the like, are transported out to the plant, and after a certain time interval or according to needs these containers are replaced by other containers filled again or being supplemented with respect to content.

It should be noted that standard containers according to standards used in the industry in various sizes can be used, or sizes and/or shapes especially provided for this purpose can be used.

Further, containers adapted for accommodation of personnel such as it is known from construction sites can be used, for example a modular system completed with sleeping facilities, lavatory facilities, kitchen, living room, etc. Such containers can be in the plant 1 in longer periods or all the time, but they can also be transported to the plant when there is servicing, repair or the like, where personnel have to be present for a certain limited period, for example for a week, two weeks, or more, and following which the containers can be transported to shore again (or to another plant). Hereby, an effective servicing is obtained whereby the personnel can work effectively over a period of time, and whereby large time consumption for transportation of personnel is avoided. The personnel can be transported out to the plant by a helicopter for example, cf. the helicopter landing site 30, after which the personnel can concentrate on the work to be done, as all necessities can be transported out to the plant in advance. Subsequently, the personnel can be flown back to shore, after which used containers, etc. can be removed, when this is appropriate.

The applied cranes and winches 62 can be of known types, for example such that are used in offshore oil plants and gas plants, where wave-compensated (heave compensated) winches can be applied, by which unloading and loading of ships can be done in spite of the rough sea. Thus, necessities can be transported to the plant 1 without consideration of weather, rough sea, etc.

As shown in fig. 14, the beam construction 2 is provided with a relatively flat profile, which provides a possibility for using the top side for transportation, working area, parking of containers, etc, but as described earlier, the beam construction itself 2 can be provided in an indefinite number of ways and with other forms. As described earlier the internal of the beam construction 2 can be applied for many different purposes, including storage, working area, workshop facilities, and/or living facilities, etc., and there can be hatches 64, openings or the like, as shown in fig. 14, through which material, containers, etc. can be let into the beam construction 2. These hatches 64, openings, or the like, can be placed at the top side of the beam 2 as shown, so that for example a container 72 can be lifted from the ship 70 by the crane 62 directly up from the ship and down through a hatch 64. Such hatches, or the like, can also be placed at the underside of the beam 2 so that containers, or the like, can be lifted up into the beam construction 2 from below and placed there, for example by a winch, or the like, which is placed in the interior of the beam 2.

Besides the mentioned devices for producing electric energy primarily by means of wind turbines, but as mentioned also by means of for example solar cell plants, generator plants for example diesel generator, plants, etc., the plant preferably can comprise other devices for the production of energy. For example the plant can comprise means to exploit energy of waves and/or currents for example wave mechanisms, turbines, or the like.

Thus, the plant can comprise an apparatus for exploitation of wave energy which apparatus can be arranged in various ways such as it is known within the field of wave energy. Such an apparatus can for example be mounted on or in pontoons, connected to the support structure or be placed in another way. Also, there can be arranged mechanisms for exploitation of the current energy itself, which mechanisms also can be mounted on or in pontoons, connected to the support structure or be placed in another way.

Also, the plant can comprise means for storage of energy, for example in form of means for production and storage of hydrogen, which can be placed in said buoyancy elements, pontoons, or the like, for example.

Thus, for example hydrogen, which can be stored in tanks such as it is known from other plants, can be produced when for example more electric energy is produced than can be sold to the distributions channels, considering the market conditions. Such tanks can be placed in pontoons or in other parts of the structural elements of the plant. The produced hydrogen can later be used to produce electric energy for example, either on the plant or in another place, for example transported to shore. Other ways to store the energy are also possible.

The invention is described above with reference to the drawings, which show specific embodiments, but it should be understood that the invention can be varied in an indefinite number of ways within the scope of the following claims.

Thus, the number of buoyancy elements or pontoons in a plant can vary, just as the form of the pontoons can be varied in respect to those shown in the drawings. Thus, it may be desired that the pontoons are made pointed in front so that towing etc. is made easier, while the rest of the form shall be so that the pontoons as far as possible are not affected by the sea currents, since these do not necessarily need to coincide with the direction of the wind.

Further, it should be noted that a plant according to the invention can be built in optimal materials with respect to properties such as strength, weight, durability, corrosion (decomposition because of salt water, UV irradiation, etc.).

Further, it should be noted, that the term beam in the foregoing and in the claims is to be construed in a broad context, since there can be many forms. Generally, these are longitudinal elements, on which the wind turbines can be mounted, and there can be relatively flat or tall structures, circular, quadrangular, or the like, As mentioned previously, hollow structures can be used, but lattice elements, or the like, can also be used.

On the plant special emergency devices and life-saving measure can be mounted. Thus, there will of course be life-saving equipment for the personnel, which occasionally will be present in connection with servicing, repair, and the like, such as life-saving fleets, etc. Further, the plant can be provided with emergency anchors, for example one or more placed on each pontoon, in dependency of the size of the plant. These emergency anchors can preferably be activated automatically, for example in dependency of a position signal from e.g. a GPS unit. If for instance, if it is registered that the plant is outside a certain area, which could indicate that the anchoring of the plant has been broken, for example caused by an extraordinary storm, or the like, the emergency anchors are released, so that the floating of the plant can be stopped or limited.

Finally, it should be noted -that special means may be placed on the plant to help adjust the plant with respect to the direction of the wind, such as control surfaces, wind sails, or the like, which can be placed on the towers, the beam, or other places, and which can be affected by the wind so that the plant can be aligned quickly in the wind's eye.

List of reference numerals

1 Plant for wind energy production

2 Longitudinal beam

4, 4a, 4b Buoyancy element, pontoon

6 Tower on pontoon

7 Connection to middle pontoon

8 Wind turbine tower

10 Wind turbine at the top of tower

12 Wind turbine at the nethermost of tower

14 Girder for stiffening

18 Controlling propeller

20a Sea surface at towing

20b Sea surface at operation

22 Nacelle

24 Arrangement of coupling to anchoring

26 Anchoring chain

28 Cable connection

30 Helicopter landing site

32 Rotational guide

34 Adjustment movement for transverse beam

36 Seabed

38 Anchoring arrangement, anchoring block

40 Connection float, connection island, transformer island

42 Connection cable

44 Cable connection to shore

46 Flexible connection

50 Secondary anchoring point

52, 54 Anchoring cables

56, 58, 60 Anchor winch

62 Crane, winch or the like Hatches or the like Ship, supply vessel or the like Container, modules or the like

Claims

1. A plant for exploiting wind energy at sea which plant comprises a number of wind turbines, characterized in, that the plant (1) comprises: - one or more substantially longitudinal beams (2),

- a support structure (4, 6, 7) and

- means (24, 26, 38) for anchoring the plant, wherein the longitudinal beam or beams (2), onto which the wind turbines (10, 12) are placed, are mounted onto the support structure, wherein the support structure is provided with buoyancy elements (4, 4a, 4b), and wherein the plant (1) is arranged so that it can adjust its orientation in dependency of the direction of the wind, so that the plant and said wind turbines (10, 12) are substantially aligned in the wind's eye.

2. A plant according to claim 1, characterized in, that said longitudinal beam(s) are fixed with respect to the support structure (4, 6, 7).

3. A plant according to claim 1, characterized in, that said longitudinal beam or beams are (2) are mounted moveably with respect to the support structure (4, 6, 7) so that the longitudinal beam or beams can rotate in dependency of the direction of the wind.

4. A plant according to claim 3, characterized in, that the longitudinal beam or beams (2) are mounted so that they can rotate about an substantially vertical axis with respect to the support structure, optionally supported by a circular guide (32), or the like.

5. A plant according to one or more of claims 1 -4, characterized in, that said support structure is provided with, two or more buoyancy elements (4, 4a, 4b) such as pontoons, or the like, designed so that ballast can be taken up or given off, in particular water which can be pumped in and/or out of the buoyancy elements.

6. A plant according to one or more of claims 1 -5, characterized in, that said support structure is designed so that said buoyancy elements (4, 4a, 4b) together form a support.

7. A plant according to claim 6, characterized in, that said support has a form with a vertex.

8. A plant according to claims 6 or 7, characterized in, that said support has a form with backwards angled sides (2').

9. A plant according to claims 6, 7, or 8, characterized in, that said support area has a substantially triangular form.

10. A plant according to claim 6, characterized in, that said support area has a substantially quadrangular form.

11. A plant according to claim 6, characterized in, that said support area has a substantially circular form.

12. A plant according to one or more of claims 1-11, characterized in, that said support structure is provided with two or more substantially vertical towers (6) connected to the longitudinal beam or beams (2), so that this/these are positioned in a substantially horizontal level over the support structure.

13. A plant according to claim 12, characterized in, that said two or more substantially vertical towers (6) each are connected to a buoyancy element (4, 4a, 4b).

14. A plant according to claims 12 or 13, characterized in, that said substantially vertical towers (6) have such a height that the substantially longitudinal beam or beams (2) are located above the surface (20a, 20b) of the sea, also when said buoyancy elements are provided with ballast.

15. A plant according to one or more of claims 1 - 14, characterized in, that a number of wind turbines (10, 12) are mounted on or along said substantially longitudinal beam or beams, for example with mutually uniform distances.

16. A plant according to claim 15, characterized in, that said wind turbines comprise wind turbine towers (8) mounted on said substantially longitudinal beam or beams (2), and which extends upwards.

17. A plant according to claim 15 or 16, characterized in, that said wind turbines comprise wind turbine towers (S) mounted on said substantially longitudinal beam or beams (2), and which extends downwards.

18. A plant according to claim 15, 16, or 17, c h a r a c t e r i z e d in, that said wind turbines comprise wind turbine towers (8) mounted on said substantially longitudinal beam or beams (2), and which extends both upwards as well as downwards with respect to the beams (2), which wind turbine towers carry rotor blades, nacelles, etc. both at the top (10) and nethermost ( 12).

19. A plant according to one or more of claims 15-18, characterized in, that said wind turbine towers (8) are mounted so on said substantially longitudinal beam or beams (2) that the wind turbine towers can pivot with respect to the vertical plane.

20. A plant according to one or more of claims 15-19, characterized in, that said wind turbines (10, 12), preferably the nacelles (22) on these, can pivot in the vertical plane with respect to the wind turbine towers.

21. A plant according to one or more of claims 15-20, characterized in, that said wind turbines (10, 12), preferably the nacelles (22) on these, can rotate in the horizontal plane with respect to the wind turbine towers (8).

22. A plant according to one or more of claims 1-21, characterized in, that the plant (1) comprises two or more substantially longitudinal beams (2) each being mounted with wind turbines (10, 12).

23. A plant according to claim 22, characterized in, that said two or more- substantially longitudinal beams (2) are placed above each other.

24, A plant according to claim 22 or 23, characterized in, that said two or more substantially longitudinal beams (2) are placed end to end of each other.

25. A plant according to claim 22, 23, or 24, characterized in, that said two or more substantially longitudinal beams each are provided with a support structure with buoyancy elements and is placed end to end of each other, a flexible connection (46) being arranged between the beams.

26. A plant according to one or more of claims 1 - 25, characterized in, that said means for anchoring of the plant are provided so that the plant can align in a direction with respect to an anchoring point (38) on or at the sea bed (36), which direction depends on the direction of the wind.

27. A plant according to claim 26, characterized in, that said means for anchoring comprises a connection (24, 26) to the support structure or a buoyancy element thereon.

28. A plant according to claim 27, characterized in, that said connection (24, 26) to the support structure or a buoyancy element thereon is placed substantially in front of the centre of the transverse beam or beams (2), preferably at a vertex of the plant's support area.

29. A plant according to one or more of claims 1-28, characterized in, that said means for anchoring of the plant comprises two or more anchoring points (38, 50), and that the plant is connected to these by means of connections, for example anchoring cables (26, 26', 52, 54) of which at least one is arranged so that the length can be controlled.

30. A plant according to claim 29, characterized in, that said means for anchoring of the plant comprises a primary anchoring (38) and one. two, three, or more secondary anchorings (50).

31. A plant according to claims 29 or 30, characterized in_} that the plant comprises an anchor winch (56, 58, 60) connected to one or more of said anchoring points (38, 50) by means of said connections, for example anchor cables (26, 26', 52, 54).

32. A plant according to one or more of claims 1 -31, characterized in, that the plant comprises connection means to an electrical cable (28, 42) which electrical cable constitutes connection to a plant on land, and which can be placed in connection with an anchoring of the plant.

33. A plant according to one or more of claims 1 -32, characterized in, that the plant comprises driven means for use in connection with adjusting the plant, which driven means can comprise propellers (18).

34. A plant according to claim 33, characterized in, that said driven means are operated by electromotors, combustion motors such as diesel motors or similar motors.

35. A plant according to claims 33 or 34, characterized in, that said driven means comprise control propellers (18), preferably placed in connection with one or more of said buoyancy elements and optionally in form of 360 degrees rotatable propeller drives.

36. A plant according to one or more of claims 1 - 35, characterized in, that said substantially longitudinal beam(s) is/are provided as tubular bodies or the like, which can be used as a passageway or working tunnel, and as crew's quarters, workshop facilities, storage facilities, etc., and which can be adapted with containers, or similar modules for these purposes.

37. A plant according to one or more of claims 1-36, characterized in, that the plant comprises means for receiving and handling containers or similar modules.

38. A plant according to one or more of claims 1 - 37, characterized in, that the plant comprises means for receiving and handling articles such as containers, wind turbine parts, spare parts, etc., which means for example comprises cranes (62) and/or winches for unloading or loading.

39. A plant according to one or more of claims 1 - 38, characterized in, that the plant comprises solar cells and/or diesel generator plants, for example for supply of electricity for the control equipment and emergency equipment in calm periods.

40. A plant according to one or more of claims 1-39, characterized in, that the plant comprises means for exploiting the energy of waves and/or currents, for example wave mechanisms, turbines, or the like.

41. A plant according to one or more of claims 1-40, characterized in, that the plant comprises means for storing of energy, for example in form of means to produce and store hydrogen, for example in said buoyancy elements, pontoons, or the like.

42. Method of controlling a plant for exploiting wind energy at sea which plant comprises a number of wind turbines according to one or more of claims 1 - 41, whereby the plant is arranged so that the orientation of the plant is controlled in dependency of the direction of the wind, so that the plant and said wind turbines are substantially aligned in the wind's eye, whereby drive means are provided for facilitating and/or enhancing said control of the orientation of the plant, whereby measurement means provide input signals for a central control, which effects a control of said drive means.

43. Method according to claim 42, whereby said drive means comprise propeller drive means.

44. Method according to claim 42 or 43, whereby said drive means comprise means for controlling the effective length of one or more connections, e.g. anchor cables, from the plant to one or more anchoring points such as for example anchor blocks.

45. Method according to claim 42, 43 or 44, whereby said measurement means provide signals relating to wind and current directions and/or speeds.

46. Method according to claim 45, whereby said measurement means provide signals relating to wind and current directions and/or speeds at the plant and at one or more positions located at a distance from the plant.

47. Method of operating a plant for exploiting wind energy at sea, which plant comprises a number of wind turbines mounted on one or more substantially longitudinal beams or similar structures, said plant further comprising a semi- submersible support structure having buoyancy elements and means for anchoring the plant, whereby the plant is arranged so that it can adjust its orientation in dependency of the direction of the wind, whereby said substantially longitudinal beam(s) or similar structures is/are adapted for accommodating containers or similar modules for supplying necessary equipment, spare parts, etc., whereby said containers or similar modules are hoisted from a supply vessel onto said plant, when supplied, and lowered again to a supply vessel when appropriate.

48. Method according to claim 47, whereby said one or more substantially longitudinal beams or similar structures are provided as tubular bodies or the like, which can be used as a passageway or working tunnel, and as crew's quarters, workshop facilities, storage facilities, etc., and which can be adapted with said containers or similar modules.

49. Method according to claim 47 or 48, whereby said plant comprises means for receiving and handling articles such as containers, wind turbine parts, spare parts, etc., which means comprises cranes and/or winches for unloading or loading.