As resources of fossil fuels, such as coal, oil or natural gas are depleted, an increasing amount of interest is taken in the possibility of obtaining energy from natural resources. It is also widely accepted that the world's dependence on fossil fuels for energy has resulted in a large number of environmental problems, including global warming, air quality deterioration, oil spills and acid rain, and thus the search for alternative energy resources has gathered speed. Much of the research has focused on utilising resources such as the sun, sea and wind.

Wind energy is recognised worldwide as a proven technology which can be utilised to meet the world's increasing electricity demands in a sustainable, economical and, most importantly, an environmentally friendly manner. In particular, wind power can be used to generate electricity without air emissions, water pollution or waste products, and can greatly reduce the pollution which is currently generated by fossil fuels.

Today wind energy is the fastest growing source of electricity in the world and capable of competing with the well established forms of power generation. However, the use of wind energy is not without its problems.

Whilst most people would agree that the concept of using a natural renewable resource to generate energy in a clean and environmentally friendly manner is a good idea, the erection of on-shore wind 1 turbines, comprised of a tower, a nacelle containing a generator, and 2 a rotor assembly comprised of blades and a hub, is often 3 controversial. Largely, this is due to the visual impact of the 4 large and often cumbersome apparatus, which is required. For 5 example, near populated areas, the construction of wind turbines may 6 be opposed by residents who regard them as unsightly, noisy or that 7 their presence will reduce property values. In addition, a variety 8 of restrictions have effect on the construction of these wind farms, 9 including planning constraints and restrictions on the visual impact 10 and sound emissions from the turbines.

11 12 The idea of taking the wind industry offshore has developed as a 13 result of these issues. The idea of offshore wind farms was in fact 14 raised more than 20 years ago, and has been particularly used in 15 lowland countries such as The Netherlands and Denmark who realised 16 they could take advantage of the less turbulent but higher winds 17 which occurred offshore.

18 19 Offshore wind farms have minimal environmental effects, and do not 20 encounter the same planning restrictions or difficulties with nearby 21 residents that have arisen with the development of on-shore wind 22 farms. As a consequence, the size and sound emissions of the farms 23 do not have to be strictly regulated and, as a consequence, much 24 larger multi-megawatt machines can be used offshore. In addition, 25 the size of the offshore resource is huge, even when restrictions 26 such as shipping lanes, areas of limited sea depth and known dumping 27 grounds are taken into account.

28 29 Today the vast potential of the offshore industry is a key area of 30 research and development in the field of renewable energy resources.

31 Nevertheless, the disadvantage of offshore development lies in the 32 fact that it is much more expensive than on-shore farms. It is 33 estimated that capital costs are in the region of 30% to 50% higher 34 offshore due to the larger machine size, maintenance and operational 35 costs, including the cost of transporting and installing turbines at 36 sea. It will be appreciated that the construction of turbines, 37 delivery to site and assembly of the large machines require 38 specialist equipment and this greatly increases the costs in running 39 an offshore farm.

40 1 At present, a common method of constructing offshore wind turbines 2 utilises a floating or jacked up crane vessel construction.

3 Typically a specially adapted ship is piloted to the area where the 4 turbine is to be constructed. Generally, as a result of the size of 5 the crane and structure they must carry, these vessels are large in 6 size and thus relatively expensive to use. Once the vessel has 7 reached the area where the turbine is to be positioned, a mono-pile 8 foundation or concrete gravity base foundation is placed onto the 9 seabed onto which the offshore wind turbine can be mounted. A gravity 10 base foundation settles on the seabed and rises above the sea 11 surface. If necessary the foundation is further stabilised using 12 sand, rock, or alternatively water. A pylon-like turbine tower can 13 then be fitted onto the concrete foundation, the turbine tower 14 carrying the nacelle and the blades which spin upwind of the tower 15 itself. However, this process incurs significant costs, as it is 16 necessary for the crane carrying vessel to remain in the area in 17 order to support the wind turbine.

18 19 One type of foundation currently used, the so called"gravity base" 20 relies on its own weight to support the turbine and the tower and to 21 prevent the tower from overturning due to the pressure exerted by the 22 wind acting on the tower and rotor blades. However these foundations 23 are large and heavy and require crane carrying vessels for 24 construction. They are also limited to shallow waters because of the 25 high hydrodynamic forces they attract.

26 27 It is therefore an object of the present invention to provide a more 28 economical design of installation foundation structure for use in the 29 offshore wind energy industry.

30 31 It is a further object of the present invention to provide a 32 foundation structure which eliminates the need for a floating crane 33 vessel during installation, and thus can be installed and 34 decommissioned in a more cost efficient manner, than conventional 35 foundation structures. It is an object of the present invention to 36 provide a foundation structure for use in the offshore wind energy 37 industry, which can be installed without the need for heavy lifting 38 vessels, and which is simple to recover for decommissioning or 39 reinstallation at a different location.

40 1 According to a first aspect of the present invention, there is 2 provided a self supporting foundation structure for use in the 3 offshore wind farm industry which can be installed on the seabed 4 without the need for support cranes, wherein the foundation structure 5 comprises an elongate body having a personnel landing platform and a 6 plurality of support braces.

7 8 Preferably the foundation structure is provided with buoyant means 9 such that it is self supporting on the surface of a body of water.

10 Advantageously this facilitates towing of the foundation structure 11 from a first location to a second location where the structure is 12 lowered to the seabed.

13 14 Preferably the buoyant means has adjustment means adapted to increase 15 the draught and decrease the freeboard of the structure until the 16 structure is installed on the seabed.

17 18 Preferably the buoyant means has release means, for removal of the 19 buoyant from an operable position, thereby to facilitate lowering of 20 the installation structure to the seabed.

21 22 Preferably the buoyant means is re-usable. Advantageously the 23 buoyant means may include sections of the turbine tower that need 24 transporting to site in any event.

25 26 Preferably, the elongate body is substantially annular.

27 28 The foundation structure is used to hold or secure a turbine tower, 29 nacelle and rotor blades. The tower, nacelle and rotor blades may be 30 mounted on the foundation structure once the structure has been 31 anchored in position on the seabed. Alternatively the tower, nacelle 32 and rotor blades may be attached to or loaded onto the foundation 33 structure and held in an inoperable position prior to towing to the 34 offshore location and during anchoring of the structure on the 35 seabed.

36 37 The turbine tower, nacelle and one or more rotor blades are mounted 38 on the elongate body.

39 1 Preferably the foundation structure has a base portion which is 2 adapted to be driven, sunk or pushed into the seabed. The base 3 portion will typically have a skirting means and may be manufactured 4 from metal.

5 6 Preferably the base portion of the foundation structure comprises a 7 plurality of fronds or frond mattresses to inhibit seabed scour.

8 9 The support braces may be connected to the elongate body of the 10 installation structure. Alternatively the support braces may be 11 connected to the personnel landing platform.

12 13 The personnel platform is adapted to receive personnel landed from 14 marine vehicles or certain types of aircraft.

15 16 Typically the personnel landing platform will have monitoring means 17 to monitor the integrity and stability of the foundation structure, 18 as well as drilling and maintenance tools. The personnel landing 19 platform may have a series of walkways to allow access to the 20 monitoring means, drilling and maintenance tools.

21 22 Advantageously the foundation structure can support itself until it 23 is anchored in position. Once the structure is anchored in position 24 it is capable of supporting the wind turbine tower, nacelle and rotor 25 assembly.

26 27 Most preferably the elongate body has a pumping mechanism which takes 28 up loose material such as sand, silt or mud from the seabed and 29 passes it in a substantially upward direction through the elongate 30 body or alternatively through temporary pipe work. The pumping 31 mechanism may include one or more one way valves. Preferably the 32 elongate body also comprises means for evacuating the loose material 33 from the elongate body such that it is deposited on the upper surface 34 of the base portion. Thus on operation the pumping mechanism is used 35 to secure the base into the seabed and also to inhibit scouring 36 around the base of the structure.

37 38 Typically the plurality of support braces are constructed of tubulars 39 or piping through which drilling or piling apparatus can be passed.

40 In order to anchor the installation structure to the seabed a drill 1 shoe or the like can be passed through the support braces in order to 2 lay tension anchoring means which hold the structure in position. The 3 anchoring process and drilling or piling of the support braces can be 4 operated from the personnel landing platform or from a remote 5 location.

6 7 Preferably the tension anchoring or piling means is used to maintain 8 the stability of the foundation structure and prevent movement or 9 tipping of the structure.

10 11 Advantageously the foundation structure is self supporting and thus 12 can be installed in an offshore position without the requirement of a 13 vessel carrying support cranes remaining in the area.

14 15 According to a second aspect of the present invention there is 16 provided a method of installing a structure for use in the offshore 17 wind farm industry, the structure comprising an elongate body which 18 has a pumping mechanism for taking up loose material from the seabed 19 and an evacuation means, and also a plurality of support braces which 20 are constructed of tubulars or piping through which drilling 21 apparatus can be passed, wherein the structure also comprises a 22 personnel landing platform, the method comprising the steps: 23 24 (a) manoeuvring the structure by towing or other means to an 25 offshore position using a vessel; 26 (b) lowering, sinking or placing the structure to the seabed; 27 (c) pumping loose material from the seabed in a substantially 28 upward direction through the elongate body using the pumping 29 mechanism; 30 (d) evacuating the loose seabed material such that it is deposited 31 on the upper surface of the base portion; 32 (e) passing drilling or piling means through the support braces in 33 order to lay tension anchoring or piling means to anchor the 34 structure to the seabed.

35 36 Preferably buoyant means are provided on the structure such that it 37 is self supporting on the surface of a body of water in the step 38 where the structure is manoeuvred to the offshore location.

39 1 In the step where the structure is lowered, sunk or placed on the 2 seabed the buoyant means may be released, removed or altered.

3 4 Optionally the step of drilling or piling through the support braces 5 in order to lay the tension anchoring or piling means can be operated 6 from the personnel landing platform.

7 8 Alternatively the step of drilling or piling through the support 9 braces in order to lay the tension anchoring or piling means can be 10 operated from a remote location.

11 12 Advantageously the steps for installing the structure can be carried 13 out without the need for support cranes to be present. This 14 eliminates the need for a vessel carrying the support crane to remain 15 next to the structure as it is being installed.

16 17 Optionally, the tower, nacelle and rotor blades may be mounted on the 18 foundation structure after the step where the drilling or piling 19 means is passed through the support braces in order to lay tension 20 anchoring or piling means. Alternatively the tower, nacelle and rotor 21 blades may be attached to or loaded onto the installation structure 22 before the step where the structure is towed to the offshore 23 location.

24 25 According to a third aspect of the present invention there is 26 provided a method of installing a wind turbine for use in the 27 offshore wind farm industry, using a foundation structure, the 28 structure comprising an elongate body which has a pumping mechanism 29 for taking up loose material from the seabed and an evacuation means, 30 and also a plurality of support braces which are constructed of 31 tubulars or piping through which drilling or piling apparatus can be 32 passed, wherein the structure also comprises a personnel landing 33 platform, the method comprising the steps: 34 35 a) manoeuvring a self-supporting foundation structure by towing or 36 other means to an offshore location using a vessel; 37 b) dropping, lowering, sinking or placing the self-supporting 38 foundation structure on the seabed; 39 c) anchoring or piling the structure to the seabed.

40 1 Optionally the transportation vessel may be removed prior to the step 2 of anchoring or piling the structure to the seabed.

3 4 Preferably in the step where the structure is manoeuvred to the 5 offshore location, buoyant means are provided on the structure such 6 that it is self supporting on the surface of a body of water.

7 8 In the step where the structure is lowered, sunk or placed on the 9 seabed the buoyant means may be released, removed or altered.

10 11 Optionally, the tower, nacelle and rotor blades may be mounted on the 12 foundation structure after the step where the structure is anchored 13 to the seabed. Alternatively the tower, nacelle and rotor blades may 14 be attached to or loaded onto the installation structure before the 15 step where the structure is towed to the offshore location.

16 17 Following the step where the foundation structure is dropped, 18 lowered, sunk or placed on the seabed the pumping mechanism on the 19 elongate body takes up loose material such as sand, silt or mud from 20 the seabed and passes it in a substantially upward direction through 21 the elongate body. The loose material is then evacuated from the 22 elongate body such that it is deposited on the upper surface of the 23 base portion to secure the base into the seabed and also to prevent 24 scouring at the base portion.

25 26 Typically the step where the structure is anchored to the seabed can 27 be operated from a remote source or by machinery and tools located on 28 the personnel landing platform.

29 30 Embodiments of the present invention will now be described by way of 31 example only, with reference to the following Figures in which: 32 33 Figure 1 is a schematic view of the foundation structure being 34 manoeuvred by a towing vessel to its offshore position, according to 35 a preferred embodiment of the present invention; 36 37 Figure 2 is a schematic view of the foundation structure at the 38 offshore area where it is to be installed, when released from the 39 vessel; 40 1 Figure 3 is a schematic view of the foundation structure when 2 submerged into the seabed; 3 4 Figures 4 to 6 are a schematic view depicting the process by the 5 which the foundation structure is secured in position; 6 7 Figures 7 and 8 are schematic views of the foundation structure in 8 position where the base is submerged in the seabed; 9 10 Figure 9 is a schematic view of the foundation structure when 11 anchored in position in the seabed; 12 13 Figure 10 is a schematic drawing of the foundation structure when 14 installed and anchored or piled on the seabed, and when the turbine 15 has been installed to its working position; and 16 17 Figures 11 and 12 illustrate the foundation structure when anchored 18 in position on the seabed and in use.

19 20 Referring firstly to Figure 1, a preferred embodiment of the 21 foundation structure of the present invention is generally 22 illustrated at 1. It can be seen that the foundation structure can 23 be manoeuvred to its offshore position using a vessel adapted for 24 towing 2.

25 26 The foundation structure comprises an elongate body 3 which is of a 27 substantially annular/tubular shape. The foundation structure is 28 adapted to hold a turbine tower 18, a nacelle 19 and one or more 29 rotor blades 4. In one embodiment the turbine tower 18, nacelle 19 30 and rotor blades may be mounted on the installation structure once 31 the structure has been anchored in position as shown in Figure 9. In 32 an alternative embodiment the turbine tower 18, nacelle 19 and rotor 33 blades may be attached to or loaded onto the installation structure 34 before towing to the offshore location. If the turbine tower 18, 35 nacelle 19, and rotor blades 4 are held in an inoperable position 36 during anchoring of the structure they are transferred to an operable 37 position once the structure is securely anchored to the seabed.

38 39 The advantage of the present invention lies in the fact that the 40 foundation structure can support itself until it is securely anchored 1 in position on the seabed. As a result it is not necessary to, 2 maintain a support crane at the site and thus, the vessel which 3 manoeuvres the foundation structure to its position does not need to 4 remain next to the structure as it is being installed. Once the 5 structure is anchored or piled in position it is capable of 6 supporting the turbine tower, nacelle and rotor blades in operable 7 positions.

8 9 The installation structure also comprises a number of support braces 10 6. These may be connected to the elongate body 3 and may act to 11 maintain it in a substantially upright and vertical position.

12 Alternatively the support braces may be connected to the personnel 13 landing platform 8. The structure also comprises buoyancy means 7 to 14 aid transportation, and a personnel landing platform 8 which takes 15 the form of a raised level surface. The lower end of the 16 installation structure, which is eventually submerged in the seabed 9 17 comprises a base 10 which is typically made of metal and has skirting 18 means 11 which can be sunk into the seabed 9.

19 20 To install the structure, the vessel 2 releases the structure, once 21 it has been manoeuvred to a suitable offshore position, allowing the 22 lower sections of the structure to submerge down to the seabed 9, as 23 illustrated in Figures 2 and 3. To facilitate submersion the 24 buoyancy means may be released, removed or altered in order to allow 25 the lower half of the structure to sink below the water line.

26 27 It will be appreciated that it is important that the installation 28 structure is firmly established in position and securely anchored to 29 the seabed prior to erecting or commencing operation of the turbine 30 tower 18, nacelle 19 and rotor blades 4.

31 32 Whilst the design of the installation structure of the present 33 invention is such that it can support itself in position on the 34 seabed, the apparatus is specially adapted to allow the base 10 of 35 the structure to be sunk into the seabed 9 if necessary. This is 36 achieved using a pumping mechanism as illustrated at 12 in Figure 4, 37 where loose material such as sand, silt or mud is pumped into the 38 elongate body 3 and evacuated through a pipe, tubular, pump or 39 alternative evacuation mean 13 which in one embodiment is located on 40 the personnel landing platform 8. It will be appreciated that the 1 evacuating means may also be located on the elongate body itself.

2 Using this process, loose material 14 Erom the seabed 9 is taken from 3 the lower surface of the base 10 and pumped onto the upper surface of 4 the base 15. This may be achieved using one or more one-way valves 5 along the system.

6 7 The advantage of pumping the loose seabed material 14 onto the upper 8 surface 15 of the base 10 is two-fold. Firstly, the loose material 9 acts to secure the base 10 into the seabed, thus anchoring the 10 installation structure by exerting weight onto the upper surface 15.

11 In addition, the pumping of loose material 14 onto the upper surface 12 15 of the base 10 also helps to prevent scouring of the bottom of the 13 structure. Scouring is often seen in underwater structures which are 14 positioned on or near the seabed and occurs as a result of the 15 turbulence of the water on the seabed. Typically sand, silt or mud is 16 washed away and the area of seabed near the structure is eroded away.

17 It will be appreciated that this would be detrimental to the 18 functioning of a wind turbine, as it would affect the stability of 19 the apparatus. However, by pumping the loose material 14 through the 20 pipe 13 onto the upper surface 15 of the base 10, the effects of 21 scouring are eliminated.

22 23 The base may also comprise a plurality of fronds or preferably a 24 concrete frond mattress. Mattresses of this type are known in the 25 art and comprise a plurality of plastic or metal sections which act 26 to maintain the loose material around the base, and thus prevent 27 erosion.

28 29 It can be seen from Figures 5 and 6 that the process of removing 30 loose material from the seabed and pumping it onto the upper surface 31 of the base acts to sink the base 15 into the seabed 9, securing the 32 installation structure in position. Once this process is complete, 33 operators and crew can be landed onto the personnel landing platform 34 8 from vessel 2, as shown in Figures 7 and 8. Crew can be landed 35 from marine vehicles or alternatively certain types of aircraft.

36 37 Typically the personnel landing platform will comprise a series of 38 walkways (not shown) which allow access onto the apparatus for the 39 next stage in the installation procedure. At this stage in the 40 installation procedure, the installation structure is stabilised in 1 the seabed and can adequately support itself in position. However, 2 in order to support the extra weight once the wind turbine is 3 constructed and functioning, the method described herein also 4 comprises an anchoring process which can be seen in Figure 9.

5 6 In addition to providing access to operators and personnel, the 7 personnel landing platform 8 will be fitted with monitors and 8 drilling and maintenance tools which allow the foundation structure 9 to be anchored or piled into the seabed, as shown in Figure 9.

10 11 To anchor the structure in position the support braces 6 which 12 support the elongate body 3 in a substantially upright position can 13 be drilled or piled through, in order to position pre-stressed 14 tension anchoring or piling means 16 into the seabed. This is 15 possible as the braces will typically be constructed from piping or 16 tubulars, which allow passage of a drill shoe or other drilling or 17 piling apparatus (not shown). The tension anchoring or piling means 18 16 can be used to both stabilise and anchor the installation 19 structure in place, and also to maintain it within this position.

20 21 For example if erosion of the seabed, due to scouring or general wear 22 and tear begins to occur, tension monitors on the platform 8 will 23 notify personnel and re-tensioning can be performed as necessary.

24 25 Once the installation structure is secure, the wind turbine generally 26 depicted at 17 in Figures 10,11 and 12 and comprising turbine tower 27 18, nacelle 19 and rotor blades 4 can be installed, or moved to an 28 operable position. Operation of the turbine can thereafter be 29 commenced. As the installation structure is securely anchored in 30 place, no external supporting means such as a crane or vessel is 31 required.

32 33 An important aspect and advantage of the present invention lies in 34 the fact that the installation structure does not require support 35 cranes when being installed on the seabed. This greatly improves the 36 ease by which a wind turbine can be constructed, by facilitating the 37 manner in which the structure can be installed, thus reducing the 38 cost involved in installing wind turbines offshore. Most 39 importantly, the structure is constructed to be able to support 40 itself in its offshore position on the seabed, without the

requirement of a support mast or crane, until it has been securely anchored in place.

Various modifications may be made to the invention herein described without departing from the scope thereof.