WO2025127951A1

WO2025127951A1 - Platform to support marine activities

Info

Publication number: WO2025127951A1
Application number: PCT/PT2024/050041
Authority: WO
Inventors: Juan CARLOS CHONG PORTILLO; Luís Manuel DE CARVALHO GATO; João Carlos DE CAMPOS HENRIQUES
Original assignee: Universidade de Lisboa
Current assignee: Universidade de Lisboa
Priority date: 2023-12-15
Filing date: 2024-10-31
Publication date: 2025-06-19
Anticipated expiration: 2026-06-15
Also published as: PT119136A

Abstract

The present invention relates to offshore platform structures. It is directed to a platform (1) for supporting marine activities with wave energy conversion systems configured to generate energy from ocean waves. It provides a solution to the low power generation level of wave energy conversion systems and the limited use of offshore platforms in relation to other offshore activities, particularly offshore wind energy generation, while keeping the loads from wind capture within safety limits. The invention consists of a platform capable of converting significant amounts of wave energy into electricity under different sea conditions while also supporting a variety of other marine activities. A possible embodiment of the platform comprises five wave energy conversion systems (100) equipped with systems for converting pneumatic energy into electrical energy (101), a surface (300) adapted to support offshore activities, a payload (400) consisting of a wind turbine, and anchoring or mooring systems (500).

Description

DESCRIPTION

PLATFORM TO SUPPORT MARINE ACTIVITIES

FIELD OF THE INVENTION

The present invention relates to of fshore platform structures . It i s directed to a platform for supporting maritime activities with systems for converting energy from sea waves .

PRIOR ART

The growing demand for energy-autonomous systems to support various activities at sea requires innovative solutions to promote their development . Of fshore platforms , both fixed and floating, have limitations in terms of energy generation, especially for energy-intensive activities . Other limitations are related to the stability of the floating platforms , the survivability, construction, assembly, accessibility, operation and maintenance , and final disposal or decommissioning of the platform at the end of their useful li fe . On the other hand, of fshore activities are constrained by the area of sea available for their development , a fact that will become more pronounced as maritime economic activities continue to grow and become more vulnerable to interference .

These activities can be aquaculture , mineral exploration, oil and gas exploration, large-scale power generation, storage infrastructures , airports and even floating cities or extensions of cities and villages on the coast , among others . Wave energy is an inexhaustible source of renewable energy . Wave energy conversion devices are generally designed to operate at resonant conditions and thus absorb a greater amount of energy from sea waves . This conceptual basis for the design of these systems is generally incompatible with the idea that wave energy converters are an integral part of floating platforms , for certain economic activities , such as floating of fshore wind, due to the tight tolerances of pitch and roll movements .

In recent decades , various systems have been proposed to extract energy from sea waves that have reached varying degrees of development and success . The floating of fshore systems , in waters with depths higher than about 50 meters , have the advantage of exploiting a resource of higher energy level and are less constrained by the geomorphological nature of the coast than the systems built on the coastline or set on the seabed in shallow waters .

There is a wide variety of floating wave energy conversion systems , being mostly of the point-absorber type , which is characteri zed by the hori zontal dimension of the device being much smaller than the wavelength characteristic of the maritime agitation . By the effect of the di f fraction of the waves , these point absorbers , i f properly si zed and controlled, can absorb an energy f lux much greater than the energy flux transported by the incident wave along a crest length equal to the hori zontal dimension of the device itsel f .

In most of fshore wave energy conversion systems , there is an oscillating body ( floating or fully submerged) that reacts against the seabed . This can raise practical di f ficulties i f the distance to the seabed is large or if the tidal amplitude is significant.

An alternative is an energy conversion resulting from the relative movement (rotational or translational) of two bodies oscillating differently under the action of waves.

In some devices, the structure forms an open cavity to the sea in its submerged part - a moonpool - inside which there is an interface between the water and the air contained in the upper part, or head space, of the chamber. The air is alternately compressed and expanded by the action of the waves and forced to pass, usually through an air turbine, which takes advantage of the pressure difference, of an alternating positive and negative signal between the chamber and the atmosphere. Such systems are referred to as oscillating water column (OWC) devices. To avoid the need for air flow rectifying valves, the turbine is generally self- rectifying, i.e. it rotates in the same direction regardless of the direction of the air flow crossing it.

The oscillating water column systems are characterised by their simplicity: the only moving part is associated with the system that converts pneumatic energy into electricity, being generally the rotors of the turbine-generator set.

The first successful oscillating water column floating devices in the use of wave energy were navigational signalling buoys commercialized in Japan since the decade of the '60s of the 20th century. These devices consisted of a cylindrical tube of vertical axis, open to the sea at its lower extremity, and rigidly connected to a floater, inside which the pneumatic chamber was located and the air turbine driving an electrical generator. These were the precursors of what later came to be denominated by OWC spar-buoy . In the patent application PT105171 , it describes a buoy of this type , with the special characteristic of the tube being, not of uni form section, but of variable section .

To avoid the large vertical dimension of the duct containing the oscillating water column of the spar-buoy systems , an L- shaped duct was proposed, with the hori zontal branch longer than the vertical branch . The obj ective was to reduce the device ' s draught and allow the installation in intermediate waters . This system, created in the eighties of the 20th century, was designated by Backward Bent Duct Buoy or BBDB . This device has the remarkable fact that the opening of the L-pipe to the sea is facing to the coast and not to the incident waves (which led to the designation by which the device is known) .

Another floating oscillating water column system, called the "Mighty Whale" , was built in Japan and installed at sea in 1998 . This device consisted of a rectangular floating platform ( length 50 m, width 30 m, draught 12 m) equipped with three oscillating water columns , in which the openings to the sea were facing the incident waves .

The use of of fshore platforms to support floating of fshore wind is currently approaching commercial scale , and there are a few platforms proposed for such applications . Patent application EP12705377A/ FR2012050163W/US201213981141A is describes one platform involving a central moonpool to dampen the motion of the barge-type structure and make it more suitable to comply with the movements ' constraints for floating of fshore wind deployment . The proposed invention, despite involving moonpools as wave energy conversion systems , is substantially di f ferent in the design constraints in terms of natural periods . In addition, the proposed platform incorporates wave energy conversion systems , and no other kind of add-on systems or extra systems as inferred in patent application EP12705377A.

PROBLEM TO BE SOLVED

The proposed invention seeks to solve two main problems associated with wave energy conversion systems and their applications . The first problem is the low electrical power generation level of such systems , which also has high energy costs associated with its operation . The other problem is the limitations of the of fshore platforms to support various of fshore activities , in particular of fshore wind energy generation, which have strict requirements in terms of the maximum movements for operation within the limits of reliability and safety .

The proposed invention provides a solution to these two problems . On the one hand, uses wave energy systems that allow the of fshore platform to convert signi ficant amounts of energy from waves , while complying to the tight requirements for various of fshore activities , including wind energy generation .

Furthermore , the proposed invention may also be configured in such a way to provide a positive hydrodynamic interference between two or more wave energy conversion systems due to the local modi fication of the surrounding wave field, which also increases overall power generation .

The proposed invention innovatively provides a solution to these problems . SUMMARY OF THE INVENTION

It is an object of the present invention a platform to support marine activities (1) comprising: at least two wave energy conversion systems (100) configured to generate energy from an oscillating mass of water. Each wave energy conversion system (100) is connected to a pneumatic chamber (200) comprising a plurality of compartments connected to each other by one or more air flow-controlling devices thereby configured to adjust the air volume within said pneumatic chamber (200) . The wave conversion systems (100) are interconnected by at least one rigid structural element (103) . The invention has at least one surface (300) adapted to support at least one offshore activity. The wave energy conversion systems (100) are operatively connected with the at least one pneumatic chamber (200) . The energy generated by the wave energy conversion systems (100) can be adjusted as a function of the air volume within the pneumatic chamber

(200) .

Each wave energy conversion systems (100) comprises a moonpool containing a mass of water is connected to the sea mass of water through a submerged opening (102) . The water mass inside the moonpool oscillates vertically as a piston by the action of the sea waves. At the same time, the sea mass of water drives the oscillation of the platform (1) , as it comprises a floating body, wherein the platform oscillation has a natural period determined by the sea water oscillation .

The air inside the wave energy conversion system (100) , consisting of the head space above the waterplane surface of the water column, is connected to the air inside the pneumatic chamber (200) , thus defining a single air volume above the waterplane surface. The oscillation of the mass of water inside the wave energy conversion system (100) compresses or expands the air above the waterplane surface of said mass of water, thus compressing or expanding the air inside the pneumatic chamber (200) .

The compartments comprised in the pneumatic chamber (200) are connected by airflow controlling devices, such as valves, that control the opening and closing of said compartments to increase or decrease the air volume of the pneumatic chamber (200) . The referred airflow controlling devices can be opened to allow the flow of air from the compartments to the pneumatic chamber (200) , thus increasing the available air volume to be compressed or expanded during the oscillation of water inside the wave energy conversion system (100) . The air volume of the pneumatic chamber (200) may also be decreased by closing the referred airflow controlling devices, thus limiting the available air volume inside the pneumatic chamber (200) to be compressed or expanded.

The variation of the air volume inside the pneumatic chamber (200) allows the adjustment of energy conversion of the wave energy conversion system (100) to different sea states. With high energy sea conditions, the oscillation of the sea mass of water is increased to a point that is necessary to adjust the energy output of the wave energy conversion system (100) to ensure a safer operation of said system. Therefore, the volume of the pneumatic chamber (200) can be physically enlarged by opening the adjacent compartments through airflow controlling devices, such as valves, to an appropriate air volume inside the pneumatic chamber (200) that would not compromise the safety of operation of the wave energy conversion systems (100) . With low energy sea conditions, the oscillation of the sea mass of water inside the wave energy conversion systems (100) is insufficient to fully compress a larger air volume inside the pneumatic chamber (200) . Therefore, the referred air volume is decreased by closing the adjacent compartments of the pneumatic chamber (200) in order to reach a volume inside the pneumatic chamber (200) that is appropriate for wave energy conversion with minimal oscillation from the sea water .

In a preferred embodiment of the present invention, the platform (1) comprises at least one payload (400) . The at least one payload (400) may be a device for harnessing energy, such as a wind turbine, but also other devices for harnessing marine energy such as water turbines, heat energy from the sea, osmotic energy from the sea, or any other types. The payload (400) may also be an electrical energy source to feed other devices, such as an electrical generator .

To increase the operational flexibility, the platform (1) comprises at least one system for converting pneumatic energy into electrical energy (101) , which may be air turbines, water turbines or piezoelectric membranes driving an electrical generator or other kind of payload (400) . The systems that convert pneumatic energy into electrical energy (101) control the damping during operation, adjusting the hydrodynamic behaviour of the platform (1) as a function of the oscillation of the sea water, which also affects the energy output of the wave energy conversion systems (100) . Therefore, the wave energy conversion levels are fine-tuned through the adjustment of the air volume of the pneumatic chamber (200) and through the damping control of the system that converts pneumatic energy into electrical energy, i.e., the system for converting pneumatic energy into electrical energy (101) comprised in the platform (1) , thus maximizing the energy conversion.

In a preferred embodiment of the present invention, at least one system for converting pneumatic energy into electrical energy (101) of the air turbine type is connected to the pneumatic chamber (200) , converting the air flow from the pneumatic chamber (200) and the atmosphere into mechanical energy, which is subsequently converted into electrical energy by an electrical generator.

Another embodiment of the present invention consists in a platform (1) comprising more than one system for converting pneumatic energy into electrical energy (101) connected to the same pneumatic chamber (200) , preferably air turbines, so that these turbines are operated to further tune the conversion capacity of the wave energy conversion systems (100) , while also keeping the turbines within safe operational conditions.

The platform (1) to support marine activities may serve as autonomous structures for offshore aquaculture exploration. It may also be used in farm arrays can generate electricity for large-scale distribution systems, when supporting wind turbines. Other activities may also be supported by the present invention, such as scientific research and oceanographic monitoring; desalination processes; production of offshore hydrogen; and exploration of mineral resources, hydrocarbons, and other oceanic resources. These examples are merely indicative.

The present invention is not limited to any of its described embodiments . DESCRIPTION OF THE FIGURES

Figure 1 illustrates a perspective view of a preferential embodiment of the platform to support marine activities (1) , comprising five wave energy conversion systems (100) , a surface (300) , adapted to support offshore activities, and a payload (400) , consisting of a wind turbine. Each wave energy conversion system (100) comprises a submerged opening (102) for the entrance of sea water and a system for converting pneumatic energy into electrical energy (101) above the waterplane. One of the five wave energy conversion systems (100) is located at the centre of the platform (1) and comprises a submerged opening (102) that is parallel to the waterplane surface. Each of the other four wave energy conversion systems (100) comprise a submerged opening (102) that is perpendicular to the waterplane surface, resulting in an L-shaped wave energy conversion systems (100) . The preferred embodiment of the platform (1) represented in Fig. 1 is shaped like a decahedron, wherein the top and bottom of the platform (1) have an octagon shape and eight side facets that cross the waterplane surface. The side facets of the platform (1) comprise rigid structural elements (103) that connect the submerged openings (102) of the wave energy conversion systems (100) . These facets comprising each one of the four submerged openings (102) of the wave energy conversion systems (100) are interspersed with facets comprising rigid structural elements (103) to connect each wave energy conversion systems (100) to each other. The eight side facets are centrosymmetric. Anchoring or mooring systems (500) connect the platform (1) to the seabed or to other objects, such as buoys or decks. Figure 2A illustrates a frontal view of the platform (1) to support marine activities, wherein a submerged opening (102) of the wave energy conversion systems (100) is located below the waterplane surface at a perpendicular orientation. A wind turbine payload (400) is comprised on the platform surface (300) being arranged slightly off-centred; as well as several systems for converting pneumatic energy into electrical energy (101) arranged on the platform surface (300) , each one associated to one wave energy conversion system (100) . Figure 2B illustrates the horizontal cross section AA of the platform (1) , defined by the dashed line in Figure 2A above the waterplane surface, wherein several pneumatic chambers (200) are adjacently disposed to each one of the five wave energy conversion systems (100) . The opening and closing of the several compartments of the pneumatic chambers (200) allows a multitude of volume configurations to adjust the energy conversion output of the wave energy conversion systems (100) , depending on the sea conditions.

DETAILED DESCRIPTION

The more general and advantageous configurations of the present invention are described in the Summary of the Invention. Such configurations are detailed below in accordance with other advantageous and/or preferred embodiments of implementation of the present invention.

In a preferred embodiment of the present invention, the platform (1) to support marine activities comprises five wave energy conversion systems (100) , wherein one wave energy conversion systems (100) is arranged to be at the centre of the platform (1) comprising a submerged opening (102) that stands at a parallel position to the waterplane surface, while the other wave energy conversion systems (100) are arranged to be at the periphery of the platform (1) having an L-shape so that each submerged opening (102) is perpendicular to the waterplane surface. The arrangement of the wave energy conversion systems (100) at the periphery of the platform (1) allows the capture of incoming waves from all directions, whereas the central wave energy conversion system (100) is adapted to generate energy from the natural vertical motion of the platform (1) in the sea. The number of wave energy conversion systems (100) may vary according to specific designs and requirements.

In a preferential aspect of the present invention, the platform (1) comprises at least one external rigid structural element (103) adapted to support and connect each wave energy conversion system (100) to another, as well as supporting other payloads (400) and elements that may be connected to the platform (1) ; and a surface (300) to support one or more marine activities.

Inside the platform (1) and above the waterplane surface are comprised several pneumatic chambers (200) in communication with the head space formed above the waterplane surface of the water column inside at least one wave energy conversion system (100) , so that the air volume of the pneumatic chambers (200) and the air volume of the head space inside each wave energy conversion system (100) forms a continuous air volume that is compressed or expanded according to the swell period to adjust the energy conversion from the waves or to modify partially and momentarily the dynamic of the platform ( 1 ) .

Furthermore, each pneumatic chamber (200) comprises a plurality of compartments comprising additional air volume that can be connected or disconnected through one or more air flow-controlling devices, such as valves, wall gate systems, penstocks, to enlarge or shrink the pneumatic chamber volume during the piston-like movement of the water column inside the wave energy conversion systems (100) . This feature allows the incorporation of large air volume changes necessary to significantly modify the spring-like compressibility effect, as the air volume may be adjusted in several times, for example, two to five times, without introducing volume elements above the deck of the platform (1) •

The ratio between the natural period of a "piston", T_piston, which simulates the behaviour of the free surface of the water mass that oscillates in the wave energy conversion systems (100) , and the natural period of the platform (1) in heave, 7h_eave/ when the platform (1) moves in a linear vertical motion, can thus be expressed by the following formula:

T ¹ pi ■ston p S_o (d + 0.52

where p is the density of the water, S_o is the platform' s waterplane area, S is the total waterplane area of all wave energy conversion systems (100) comprised in the platform (1) , d is the draught of the platform, M the mass of the platform, and Ma the added mass of the platform, considering all wave energy conversion systems (100) .

The configuration of the platform (1) is characterized as satisfying the relationship:

1,25.

The aforementioned configuration results in that the natural period of the piston formed by the water columns inside the wave energy conversion systems (100) is not too long compared to the natural period of the platform (1) in heave, determined by the oscillating sea water mass. Depending on the sea conditions, the behaviour of water mass inside the wave energy conversion systems (100) may be closer to its resonance condition when excited by the sea waves - when the ratio is smaller than 1.0 - therefore maximizing the energy conversion efficiency of the wave energy conversion systems (100) .

In a preferential embodiment of the present invention, the platform (1) comprises at least one system for converting pneumatic energy into electrical energy (101) . The referred systems (101) can be adapted to control the damping during operation, thus adjusting the hydrodynamic behaviour of the platform (1) at sea. The systems for converting pneumatic energy into electrical energy (101) may be air turbines, water turbines or piezoelectric membrane driving an electrical generator or other payload (400) .

The referred systems for converting pneumatic energy into electrical energy (101) are configured to control the damping generated in the platform (1) . When the systems (101) are of the air turbine type, the volume inside the pneumatic chamber (200) is connected to the atmosphere so that the kinetic energy of the air flowing from the pneumatic chamber (200) through the system (101) can be converted into electrical energy by a conventional generator. When using more than one air turbine connected to the same pneumatic chamber (200) , these turbines can be used to further tune the conversion capacity of the wave energy conversion systems (100) , while keeping the air turbines in optimal operating conditions. Alternatively, the systems for converting pneumatic energy into electrical energy (101) of the water turbine type can be connected to the wave energy conversion system (100) . As such, the flowing water mass inside said wave energy conversion system (100) drives the water turbine, which then drives a generator to convert the mechanical energy into electrical energy.

The proposed damping control, performed when several systems for converting pneumatic energy into electrical energy (101) are associated to one pneumatic chamber (200) , increases the flexibility of the operation as it allows the fine tuning of the hydrodynamic properties of the platform (1) and of the power generated by the wave energy conversion system (100) .

In a preferential embodiment of the present invention, the platform (1) comprises a payload (400) , being said payload (400) an air turbine or other devices adapted for harnessing marine energy, heat energy from the sea, osmotic energy from the sea, or any other type of device. Among wind turbines, all types of turbines can be considered, such as turbines of horizontal or vertical axis, having any number of blades, one or more rotors, and being equipped with or without a gearbox interposed between the rotor and the generator.

Preferably, the platform (1) comprises a polyhedron shape, wherein the top and bottom sides comprise a polygonal shape and may be symmetric to one or more axes. An octagonal shape for the top and bottom sides of the platform (1) is advantageous because the side facets have an angle of less than 90° between them, resulting in an edge that reduces the external wave loading on the platform (1) . Furthermore, an octagonal shape for the top and bottom sides provides at least four sides with wave energy conversion systems (100) installed, and at least four sides adapted to safely dock vessels, such as ships or boats, for maintenance and marine activity operations of the platform (1) .

In a preferred embodiment, the payload (400) is positioned off-centre relative to the buoyant body and ballasting systems are configured to balance the weight of the payload (400) . In addition, at least one roll damper device may be comprised to stabilize and prevent rolling of the platform (1) , such as an anti-roll keel, an anti-roll tank, or a plurality of anti-roll tanks interconnected via U-shaped tubes. Roll damper devices may be placed at the periphery of the platform (1) to reduce roll motions, such as fin stabilizers, wedges/ flaps , interceptors, bulbous bow types, or ducts.

To keep the platform (1) in position, at least one mooring system and/or anchoring device (500) is provided, such as a fixed-heading anchoring device, a cable or chain, and other devices which are suited to anchor the platform (1) to the sea bed.

Another embodiment of the present invention consists in a platform (1) that comprises at least one external appendage adapted to increase the mass of water that tails said platform (1) during its vertical motion, thus adjusting the dynamic properties of the platform (1) . Examples of the referred external appendages are skirts, plates, fin stabilizers, wedges/ flaps , interceptors, bulbous bow types, or ducts. In an advantageous aspect of the present invention, it is possible to incorporate at least one external appendage inside the central wave energy conversion system (100) to adjust both the heave natural period and also the swell period at which the mass of water inside the central wave energy conversion system (100) oscillates in phase opposition relative to the swell of the sea water.

In another embodiment of the present invention, the platform (1) may also comprise at least one storage compartment adapted to house mechanical and electrical equipment, instrumentation, gas storage tanks, and/or other elements for supporting activities at sea.

In an advantageous aspect of the present invention, the platform (1) may comprise wave energy conversion systems (100) manufactured as standardized modules made of concrete, to reduce potential material, manufacturing and maintenance costs .

The preferred embodiments shown above are combinable, in different possible configurations, being the present invention not limited to the embodiments previously described .

Claims

1. Platform to support marine activities (1) characterised by comprising: a) at least two systems for converting wave energy (100) into pneumatic energy, consisting of a hollow structure open to the sea below the inner free surface, whose oscillating water mass alternately compresses and expands the air enclosed in the pneumatic chambers (200) above the said free surface;

- the pneumatic chambers (200) consisting of a plurality of air compartments connected to one another by means of one or more air flow control devices, thus configured to adjust the volume of air inside said pneumatic chambers (200) to the state of the sea;

- the pneumatic chambers (200) being composed of a plurality of air compartments interconnected by one or more air flow control devices thus configured to adjust the volume of air inside said pneumatic chambers (200) to the sea state;

- the pneumatic chambers (200) being operatively connected to at least one system for converting pneumatic energy into electrical energy (101) ;

- wherein the air flow across the system for converting pneumatic energy into electrical energy (101) is controlled in conjunction with the air flow between the pneumatic chambers (200) , thereby varying the hydrodynamic damping of the platform; and b) at least one rigid structural element (103) configured to connect at least one of said wave energy conversion system (100) to another; and c) at least one surface adapted to support at least one offshore activity.

2. Platform to support marine activities (1) according to the previous claim characterised in that at least one wave energy conversion system (100) is positioned at the centre of the platform (1) .

3. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one payload (400) .

4. Platform to support marine activities (1) according to claim 3 characterised by comprising ballasting systems configured to balance the weight of the payload (400) .

5. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one system for converting pneumatic energy into electrical energy (101) configured to drive a payload (400) .

6. Platform to support marine activities (1) according to the previous claim, characterised in that the system for converting pneumatic energy into electrical energy (101) is included in the wave energy conversion system

(100) .

7. Platform to support marine activities (1) according to claim 6, characterised in that the system for converting pneumatic energy into electrical energy

(101) is connected to the pneumatic chamber (200) .

8. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one mooring and/or anchoring system (500) .

9. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one roll-damping device.

10. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one external appendage.

11. Platform to support marine activities (1) according to claims 2 and 10 characterised in that said external appendage is incorporated in the central wave energy conversion system (100) .

12. Platform to support marine activities (1) according to claims 10 or 11 characterised in that the external appendage is selected from the group of appendages consisting of skirts, plates, fins, wedges, flaps, interceptors, bulbous bows and ducts.

13. Platform to support marine activities (1) according to any of the previous claims characterised by comprising at least one storage compartment.

14. Platform to support marine activities (1) according to any of the previous claims characterised by comprising a polyhedron shape.