Patent Description:
The present invention is characterised in its, painstaking configuration and design, particularly its dimensions, due to which the platform is the optimal result regarding its dimensions and costs; likewise, to its hydrodynamic properties, thanks to which its stability is substantially improved.

Therefore, the present invention is included within the field of means of supporting and installing wind, wave, and ocean current energy generators on the ocean surface.

The different methods of supporting and stabilising marine wind turbine generators may be seen in <FIG> wherein the following are portrayed:.

<FIG> portrays different mooring systems of the "spar" type, tension-leg semi-submersibles (<NUM>), while <FIG> portrays a platform of the "Barge" type (<NUM>) (a group to which the present invention belongs).

Regarding these, the well-known American technician Jason Jonkman states:.

However, these platforms are complex in their execution and assembly, and also very costly, restricting considerably their scope of application and their future availability.

In the state-of-the-art, the following documents are known:.

The document <CIT> discloses a shake-reducing device for marine float that includes one turn of shake-reducing plates with upwards L-shaped outer edge in the bottom of float, one group of supporting plates connecting the shake-reducing plate to the float and set in some interval, one group of flow disturbing ports in the side near the float of the shake-reducing plates, and <NUM>-<NUM> turns of stiffening L bars in the far side of the shake-reducing plates. The present invention can improve the marine environment without lowering the FPSO or FSO functions and may be used in various kinds of marine floats.

The document <CIT> discloses an anti-rolling device of an ocean floating body, which comprises at least one group of anti-rolling components, wherein each group of the components comprises an anti-rolling box body and supporting plates; the anti-rolling box body surrounds the ocean floating body, and is formed by an upper anti-rolling plate, a lower anti-rolling plate and a connecting plate, wherein turbulence holes are arranged on the upper and lower anti-rolling plates; the supporting plates are arranged between the upper and lower anti-rolling plates; and the anti-rolling box body, the supporting plate and the ocean floating body are welded into a whole body. The number of the anti-rolling component is preferably to be two to three groups. In the same group of the anti-rolling components, the space between the adjacent supporting plates is <NUM> to <NUM>, the horizontal width of the upper and the lower anti-rolling plates of the anti-rolling box body is <NUM> to <NUM>, and the space between the adjacent groups is <NUM> to <NUM>. At least one lightening hole is arranged on each supporting plate. The device can realize the gradually reduction of the current damping by combining and using the anti-rolling components, thereby effectively reducing the amplitude of horizontal rolling, fluctuating and the heave motion of the ocean floating body, greatly improving the working environment of the workers and mechanical equipment on the ocean floating body, and the anti-rolling device has the advantages of lowered cost, convenient process and simple realization, and can be widely applied on various ocean floating body.

The document <CIT> discloses an offshore structure having a vertically symmetric hull, an upper vertical wall, an upper inwardly tapered wall disposed below the upper vertical wall, a lower outwardly tapered wall disposed below the upper sloped wall, and a lower vertical wall disposed below the lower sloped wall. The upper and lower sloped walls produce significant heave damping in response to heavy wave action. A heavy slurry of hematite and water ballast is added to the lower and outermost portions of the hull to lower the center of gravity below the center of buoyancy. The offshore structure provides one or more movable hawser connections that allow a tanker vessel to moor directly to the offshore structure during offloading rather than mooring to a separate buoy at some distance from the offshore storage structure. The movable hawser connection includes an arcuate rail with a movable trolley that provides a hawser connection point that allows vessel weathervane.

The <CIT> discloses an offshore depot having a vertically symmetric hull, an upper inwardly tapered wall and a lower outwardly tapered wall that produce significant heave damping in response to heavy wave action. Ballast is added to the lower and outermost portions of the hull to lower the center of gravity below the center of buoyancy. The offshore depot includes a tunnel formed within or through the hull at the waterline that provides a sheltered area inside the hull for safe and easy launching/docking of boats and embarkation/debarkation of personnel. When the watertight tunnel doors are all shut, the tunnel may be drained to create a dry dock environment within the hull. The offshore depot includes berthing and dinning accommodations, medical facilities, workshops, machine shops, a heliport, and the like.

Finally, document <CIT> relates to the field of floating bodies, and more particularly to an annular floating body (<NUM>) comprising a central opening (<NUM>) in a well, configured such that, in water, with a swell of a period substantially equal to one own period of the floating body (<NUM>) heave, vertical forces exerted on the floating body (<NUM>) by a body of water oscillating in the central opening (<NUM>) in phase opposition with respect to the swell, compensate at least partially vertical forces exerted on the floating body (<NUM>) by the swell, and a method of extinguishing at least partially a heave movement of the floating body (<NUM>) at a specific period of the floating body (<NUM>).

The prior art reveals patent <CIT>, which discloses a multi-purpose disc-shaped floating platform for supporting marine wind turbine generators and other marine energy generators, which claims to be a floating platform that supports wind turbine generators or generators driven by waves and/or ocean currents or the tides, where the platform has a height-to-diameter ratio of less than <NUM>%, stating that its weight is considerably less than that of other platforms.

Although said platform fulfils the requirement sought, it nonetheless presents several aspects which clearly leave room for improvement. Indeed, on the one hand, with the height-to-diameter ratio of the platform, it must necessarily have a relatively large radius, resulting in greater dimensions, a greater quantity of material and therefore a greater environmental impact, and consequently, significantly high manufacturing, testing and transport costs. Furthermore, additional factors have not been considered, such as the period of the waves, which may cause the platform to enter into resonance and even overturn.

A solid, when disturbed from its resting position, tends to vibrate at certain frequencies, called natural frequencies, when excited. For each natural frequency, the solid acquires a particular shape, called mode shape. Frequency analysis calculates the natural frequencies and the associated mode shapes. When the frequency of the wave-emitting source coincides with the natural frequency of the resonator (the object that oscillates), a condition known as resonance is reached. Resonance is defined as the tendency of a physical system to oscillate with a much higher amplitude at some frequencies. If the platform amplifies its oscillation with lists of <NUM>, <NUM> degrees or more, said movements might even cause the platform to overturn.

Therefore, the object of the present invention is to overcome the drawbacks stated concerning the floating disc-shaped platform disclosed in <CIT>, fundamentally concerning its excessive size, and therefore costs and associated complexities, likewise the possibility of entering into resonance with the movement of the ocean waves and even overturning, by developing a platform which overcomes the aforementioned drawbacks and which takes into account all the possible factors that come into play in its stability on the ocean surface.

This platform has the characteristics described below the essential nature whereof is described in claim <NUM>.

The object of the present invention is a floating platform for supporting marine power generators of any type and nature, either wind turbine generators, or generators that exploit the movement of the tides or the undulating movement of the waves.

It will be disc-shaped, and its perimeter may be circular or multiple-sided polygonal, this choice depending solely on the ease of construction.

It will be located by means of anchoring, and due to it being totally regular, it will present an identical surface to the waves, wherever they come from. However, the nacelle (where the wind power generator is housed) will swivel, to absorb the energy of the wind, from whichever direction it comes.

The power generators driven by the waves and currents will consist of devices specifically designed for this purpose, with either vertical-shaft rotors (waves) or horizontal-shaft (currents), or other devices which, located on the periphery of the platform at the height of the waterline, enable the collection of the energy foreseen to be performed.

For the design of the platform which is the object of the invention, the following factors, described below, and the inter-relationship between them, have been considered.

For the stability study, the following have been considered: the action of the wind on the generator blades, the swell against the assembly, and the inter-relationship between the inertias, the centres of gravity, the flotation inertia, the metacentric height, the centre of buoyancy, etc. all given in the following expressions: <MAT> <MAT>.

T = is the period, expressed in seconds.

It is related to the mass (Ig) and the stability (P x (r-a)) by the expression: <MAT>.

K = being the coefficient established by various hydrodynamic tests which includes the additional inertia due to the mass of water associated with the floater in question, ship, or platform, when it oscillates in the water.

Given that the period of the waves varies between <NUM> and <NUM> seconds, it has been adjudged that, at least, the period of these platforms must be greater than <NUM> seconds, as this is in the region of <NUM>% more than the smallest period of the swell and is the proportion that is considered minimal to prevent phenomena of resonance.

All the above formulae and the parameters taken into account enable the design of an approximately disc-shaped floating platform that fulfils the conditions sought regarding the smallest size possible and therefore likewise costs and complexities, has an acceptable wind-caused list for the equipment installed, slamming does not occur, as it is "glued" to the ocean surface at all times, and it prevents the possibility of entering into resonance with the ocean wave movements, and thus does not damage the equipment installed and can never overturn.

In order to satisfactorily resolve the aforementioned conditions, stability calculations and a scale model test have been performed, defined by the equality of the Froude's number (which relates the forces of inertia with those of gravity and is represented by the quotient between velocity and the square root of the product of gravity by length) in a model and a prototype (according to the table below) in a hydrodynamic Test Canal with reference OTI <NUM>, equipped with a suitable anchoring system and using an optical monitoring system (Krypton) with an incident wave sensor, a relative wave sensor, accelerometers, load cells and cameras to film the <NUM> different regular and irregular surges to which the platform was subjected.

List of dimensions between model and prototype.

Considering the calculations performed and the subsequent verifications in hydrodynamic tests, the floating platform presents a ratio between the depth or height of the platform and the diameter thereof, excluding the bulwarks and keels, of between <NUM> and <NUM>.

In order to verify all the above calculations, a prototype was constructed and subjected to a hydrodynamic test. The first test was a so-called "extinction test", or verification of calculations, and next the <NUM> different types of swells were produced, from <NUM> (service) to <NUM> (extreme or survival), overcoming all of these. The survival swells were none other than the maximum swells that occur in the North Atlantic. The tests have proven the correct sizing of the floater, of its weight and thrust distribution, its inertias, buoyancy, or response to undulating movements, its anchoring system, its vertical and horizontal accelerations, velocities, period, etc..

This test is highly significant, as it is set at the most demanding extreme, but there are many other intermediate states where the proportions may be varied to comply with requirements, and therefore we must work on a group and not a single point.

The dimensions of the platform tested were: <NUM> radius, <NUM> depth, with a bulwark of <NUM> and a keel of <NUM>. Draught was <NUM>. The distance between the waterline and the top of the bulwark: <NUM>.

This survival test was performed without generating power; the list angle caused by the wind is therefore zero.

The fact that the survival test was passed with these dimensions tells us that with the maximum incident wave measured, this being <NUM>. , the height of <NUM>. was sufficient.

With this datum, the platform was resized for a wind thrust of <NUM> MW (<NUM> kN), resulting in the following:.

The stability tests reveal that, when exploiting the maximum energy from the wind, there is a list of <NUM>°. A list that is produced from the Centre of Gravity of the assembly.

As the height of the incident wave with service (not survival) swell was <NUM>. , the free height from the waterline to the top of the bulwark must be:<MAT>.

Combining this distance with the <NUM>° list, the new radius of <NUM>. gives a depth of <NUM>. plus bulwark and keel of <NUM>.

Conversely, the depth could be reduced, and the height of the keels and bulwarks increased; thus, the ratio could be reduced as deemed appropriate, although this may be unworkable.

Thus, with <NUM>, the depth would be <NUM> x <NUM> = <NUM>. , and the bulwark would be: (<NUM>-<NUM>) / <NUM> = <NUM>. , and the keel also <NUM>. , so the sum of depth + bulwark + keel = <NUM>.

These dimensions could result in an insufficient structural resistance to the impact of the waves and to undersea movements due to the excessive cantilevered height, although this solution might be chosen for small swells, with keels and bulwarks of a lesser height.

However, a similar sizing might be feasible if the power of the generator is reduced, e.g., from <NUM> MW to <NUM> MW.

Therefore, bearing in mind that the proportions are highly variable, depending on:.

It is considered that the relationship or ratio between the depth or height of the platform and the diameter thereof, this being between <NUM> and <NUM>, satisfies the stability requirements that consider all the physical variables that may affect its stability (wind, force of the swell, period of the waves, period of the platform itself, list of the assembly, etc.).

Finally, it must be stated that this platform may be <NUM> or smart, as it features some of the means described below or combinations thereof:.

Unless indicated otherwise, all the technical and scientific elements used in this specification have the meaning usually understood by a person skilled in the art to which this invention belongs. In the practice of this invention, methods, and materials similar or equivalent to those described in the specification may be used.

In the description and claims, the word "comprises" and its variants do not intend to exclude other technical characteristics, additives, components or steps. For persons skilled in the art, other objects, advantages, and characteristics of the invention will be partly inferred from the description and partly from the practice of the invention.

In order to complement the description being made herein, and with the objective of better understanding the characteristics of the invention, in accordance with a preferred practical embodiment thereof, said description is accompanied, as an integral part thereof, by a set of drawings where, in an illustrative and non-limiting manner, the following has been represented:.

In view of the figures, a preferred embodiment of the proposed invention is described below. In <FIG> we can see a lateral view of the floating platform, showing the depth or height of the platform (<NUM>), the diameter (<NUM>), the draught (<NUM>), the distance between the water surface and the base of the platform, likewise the free distance (<NUM>), this being understood to be the distance between the surface of the sea and the upper edge of the platform. Also visible are several additional complementary elements, consisting of sloping keels or skirts (<NUM>) that provide stability, and optional sloping bulwarks or profiles (<NUM>) which surround the perimeter of the platform and prevent the entry of water to the surface thereof.

<FIG> portrays the structure of the floating platform which, as may be seen, consists of a series of carlings (<NUM>) disposed radially with regard to a central axis (<NUM>), where the carlings (<NUM>) are connected by means of a series of stringers (<NUM>) to endow the platform with greater structural rigidity; in addition, a series of transversal perimeter reinforcements (<NUM>), disposed in the final span of each circular section, where all the aforementioned elements are housed in the internal space defined by an external shell or external sheathing (<NUM>) to compensate the external pressure of the sea.

The tower has a series of ribs, in such a way that said element is positioned so that these are in correspondence with the carlings.

In <FIG> and in the detail in <FIG>, a series of angular reinforcements or bulb flats (<NUM>) may be seen; these are disposed on the interior of the external plates. Said bulb flats (<NUM>) on the external sheathing are installed vertically, as are the ribs of ships, while on the decks and base the bulb flats (<NUM>) are installed radially in the intermediate space defined by the carlings (<NUM>). Their purpose is to reduce the opening and to reduce the thicknesses of the plate.

The platform may be constructed from Steel, Marine Steel A or glass-fibre reinforced polyester (GRP).

By way of an example, for the twelve-sided polygonal platform described above, with a radius of <NUM>. and a height of <NUM>. , we should proceed as follows:.

These modules would be constructed in a workshop, welded with construction procedures and details approved by a Classification Society and with careful preparation of the surfaces for the application of rust-preventive and anti-fouling paints (this last on the external submerged section - underwater body).

The twelve modules would be assembled on the shipyard slipway due to its surface area and its proximity to the sea, locating them with cranes and a construction cradle, observing the construction plan.

Finally, the watertightness tests would be performed, and it would be launched into the sea.

Next, with the platform now floating, the tower and nacelle would be installed, coupling its vertical reinforcements with the carlings of the bulwark, should there be one, or on the deck, exactly in the area where the carlings are located, to endow the assembly with the appropriate structural continuity.

Finally, the assembly would be towed to its definitive offshore location.

This procedure, due to the exclusive nature of the project, saves significant installation costs.

Conversely, the platforms resting on and anchored to the ocean floor, as they do not float, involve high production costs as they require the use of a considerable tonnage of material, and furthermore, the logistics for their transfer and placement are highly complex, as they must be transported in costly vessels especially constructed for the performance of these delicate operations.

On the other hand, floating platforms of the spar type, due to their great height and draught, must be transported lying flat and then erected to the vertical at their final location by auxiliary ships which are also complex and costly.

The floating platform, which is the object of this invention, by floating and having a reduced draught, may be transported by simple towing, with no need to perform any special manoeuvre in its placement. It may be considered a "plug & play" platform, as once disposed on the sea, it is ready for use. This property of installing and operating is highly important for the logistics of this invention in comparison with those existing.

Finally, it should be mentioned that the structure may also be designed straight, with parallel carlings, modifying the connection with the tower in comparison with that described herein.

Claim 1:
A floating platform for supporting generators of power derived from the wind and/or the waves and/or ocean currents, comprising an approximately disc-shaped general configuration in which a completely watertight radial structure is defined with a circular or polygonal perimeter, wherein the disc has a height or depth (<NUM>) and a diameter (<NUM>), characterised in that the floating platform presents:
(<NUM>.a) a ratio between the platform height or depth (<NUM>) and diameter thereof between <NUM> and <NUM>; (<NUM>.b) a natural period greater than <NUM> seconds, as this is in the region of <NUM>% more than the smallest period of the swell, and (<NUM>.c) a sloping keel (<NUM>) acting as a skirt arranged to improve the floating platform behaviour against the swell.