WO2013006072A1

WO2013006072A1 - Submerged platform

Info

Publication number: WO2013006072A1
Application number: PCT/PT2012/000026
Authority: WO
Inventors: Tiago COSTA DUARTE PARDAL
Original assignee: Omnidea Lda.
Priority date: 2011-07-05
Filing date: 2012-07-05
Publication date: 2013-01-10
Also published as: WO2013006072A4; PT105792A

Abstract

The present invention is an improvement to waterborne platforms that are used to anchor aerial and airborne systems deployed over water. The system basically consists of a fully submerged main body (1), which is immersed in a body of water and anchored through one or more cables (3) to the bed (8) of said body of water. The platform includes one or more tubes (5) connected to it through watertight articulated joints (6) at one end, and with the other end above the free surface (7) of the water. The tube houses one or more structural elements (9) which connect to the airborne platform located above the water's surface. The submerged platform represents a better way to house and protect any necessary ground equipment related to the airborne system anchored, safer from waves and other undesirable phenomena occurring on the free surface of the water.

Description

Submerged Platform

Field of the invention

The present invention pertains to the field of Mechanical and Marine Engineering and consists of a new type of submerged platform that can be used, for example, as a marine anchoring point for tethered airborne platforms.

Cited documents · Patent WO 2010144984 (Al) - Hydropneumatic power station with a submerged, cylindrical power house and a land platform (23/12/2010);

• Patent CN 101871207 (A) - Offshore wind turbine bearing device (27/10/2010);

· Patent WO 2011050699 (Al) - Platform for collecting marine energy sources (05/05/2011);

• Patent US 2011074160 (Al) - Wave Energy Conversion Plant (31/03/2011).

Background The current background art includes numerous examples of waterborne platforms for supporting energy systems. Many of these platforms are not submerged and are thus subject to the effects of disturbances on the free surface (waves) of the water body in which they are operating. They are suited, but not ideally to serve as waterborne platforms for the anchoring of airborne platforms, unlike the present invention .

Patent application WO 2010144984 (Al) refers to a hydropneumatic power plant, in which the machinery section is contained within a submerged cylinder and additional equipment is installed in a land-based platform. The patent application refers only to submerged platforms which are hydropneumatic power plants and, while the current invention may be used for that end, it is in no way limited to that application. Additionally, the patent application does not claim any sort of tube connected in a flexible and watertight manner to the main structure.

Patent CN 101871207 (A) claims a marine platform for supporting a conventional wind turbine. In common with the present invention is the fact that the platform is submerged and anchored to the bed of the water body in which the platform is operating. However, the platform described in the aforementioned patent is supported by a rigid column instead of being floating, and does not have a tube to connect to the surface.

Patent WO 2011050699 (Al) claims a marine platform that can be used to support diverse renewable energy systems (wind, solar, tides and waves) . Despite floating and anchored, this platform is not submerged and, consequently, doesn't have a tube connecting it to the surface.

Patent US 2011074160 (Al) claims a floating marine platform intended to support devices for producing energy from the waves. This platform is not totally submerged, unlike the present invention.

The background research did not yield any information that challenged the novelty of the current invention.

Disclosure of the invention

The present invention addresses the need for improved waterborne platforms to support airborne systems, for wind energy production or other purposes and which connection to the ground (land or sea) is basically performed by at least one cable

The present invention consists basically of a watertight volume completely submerged in a body of water, with an anchoring system connecting it to bed of said body of water and at least a snorkel-type tube which is connected to the main volume in a flexible manner. This tube allows passage of atmosphere but can also contain cables for transmission of mechanical force, electrical power, data or fluids between the outside and the inside of the submerged body and any equipment contained therein. The platform is submerged to avoid disturbances in the free surface of the water (waves, wind, etc....). 75 Brief description of the drawings

Figure 1 shows a schematic view of the main components of a preferential embodiment of the invention;

Figure 2 shows a schematic view of a preferential embodiment of the invention in which a possibility for the 80 anchoring system is explicitly shown.

Detailed description of embodiments

Submerged body

The main body (1) of the submerged platform may be of single or double hull construction and it may have one or

85 more floodable airlocks to allow access inside to operate or perform maintenance on the platform or its on-board equipment. The dimension and internal volume is sufficient so that the platform maintains positive buoyancy, despite any payload or internal equipment. One or more additional

90 reservoirs for ballast control may also exist on the platform.

The geometry of the submerged body (1) may also be complex, including larger volumes interconnected by more slender volumes, with the overall shape being substantially like 95 that of a star, polygon or any combination thereof where slender volumes form the sides, bulkier volumes are located at the vertices or the star centre and any combination of snorkel tubes is connected to the said bulkier volumes.

Anchoring system

100 The anchoring system's goals are to prevent the drifting of the platform, maintain it in a pre-determined geographical area and to provide a reaction force to the positive buoyancy, thus maintaining the platform submerged.

The anchor system has three main components: the anchor 105 devices (2) on the bed of the water body, one or more anchor cables (3) and their connecting interface to the platform which may be fixed or even mechanism to control the cable (s) (3) length.

The attachment to the platform may be done in such a way as 110 to permit free rotation of the platform in the horizontal plane without disturbing the anchoring system. For such, a rotary joint may be used. To avoid the need for a submersion-resistant joint, there may be a volume of trapped non-water miscible fluid (for instance air or a 115 lubricant fluid) in a chamber similar to a diving bell in which the rotary joint is contained thus keeping it out of contact with the water.

The anchoring cables (3) may be proper cables, or chains or similar devices capable of bearing the required traction 120 load and be flexible enough to absorb energy from the platform's motions and to be wound and unwound in order to change the depth of the platform when such a mechanism is installed.

The anchor device (2) may consist of a single or multiple 125 individual anchors (4). Multiple anchors may be arranged in a frame, with regular or irregular spacing between them and articulated joints connecting each anchor to the frame. Alternatively, sets of other fixating devices such as foundations or stakes embedded in the bed (8) of the body 130 of water may also be used.

Snorkel tube

Each interface (6) between the surface and the inside of the submerged body consists mainly of a tube (5) , similar to a snorkel, in which one end is connected to the 135 submerged body and the other is above the free surface of the water body (7) .

The connection between the tube (5) and the submerged body is preferably done by an articulated joint (6), which as a non-limitative example may be a flexible membrane, a

140 section of tube constituted by an elastomer or a sealed rotary joint allowing unconstrained movement in at least two rotational degrees of freedom. This joint must have a bore, cavity or be otherwise hollow in order to allow passage of structural members (9) and atmosphere between

145 the inside of the snorkel tube and the inside of the submerged body, despite the relative orientation between the tube and the submerged body.

The length of the snorkel tube (5) should be adequate in order to ensure that the end is kept above the free surface 150 (7) of the water body during all expected operating circumstances. Adequate seals and valves may also be added to reduce the incursion of water into the snorkel tube in conditions outside the operating parameters. A subsystem for draining out any (expectedly small) amount of water 155 that enters the interior of the platform may be added.

Aside from a structural connecting element (9), which may be, for example a tether cable or a shaft, there may be other elements passing through the snorkel tube (5) between the inside of the submerged body (1) and the atmosphere. In 160 some embodiments, there may be cables for transmission of electrical power or signals, optical fibres or tubing for transmission of fluids.

The open end of the tube (5) may include rollers or bushings made from a self-lubricating material or other

165 devices to limit the friction of the structural member on the end of the tube whenever the two are in contact, these rollers or bushings can also be installed inside the tube to avoid friction in its interior. The geometrical shape of the tube's end may also be such that said friction is

170 minimized like for example tube top(s) with outwardly curved shape.

Whenever a connection to dry land is necessary, be it to transmit energy, data or fluids, the necessary connection lines may be attached directly to the outside of the 175 submerged body (1) by watertight connections or may run through the snorkel tube (5) , exit at the end above the water and then drape back to the bed of the water body, running along it to dry land

Application examples

180 This platform may be equipped with different subsystems, rendering it able to perform a variety of tasks for which its main features are desirable. The fact that the waterborne platform is submerged means it is much less vulnerable to free surface disturbances than floating

185 platforms. In preferred embodiments, the submerged platform is used as an anchor point for tethered airborne platforms deployed offshore. These airborne platforms may fulfil a variety of roles including monitoring, telecommunications and energy production. Therefore, the submerged platform is

190 used to house all the auxiliary systems that would be the ground segment of a land-based system.

Lisbon, July 5th,

Claims

1. Submerged platform comprising a watertight body, anchoring cables and anchoring devices at the ends of the cables characterized in that:

a. the body is buoyant and therefore there is a net positive force pulling it upwards and

b. a snorkel tube connects the inside of the watertight body to the atmosphere above the free surface of the body of water wherein the platform is submerged.

2. Submerged platform according to claim 1 in which the watertight body includes any combination of:

a. a double hatch and a pumping system to allow access to the interior of the platform;

b. a watertight articulation which allows the orientation of the snorkel tube to be changed; c. watertight reservoirs for buoyancy control via variable ballast and

d. a subsystem which allows the platform to rotate freely in the horizontal plane without disturbing the anchor cable (s)

e. a mechanism to control the length of the anchor cable (s) .

3. Submerged platform according to claims 1 and 2 in which there is a watertight articulation for the snorkel tube and in which said articulation is:

a. enveloped by a flexible membrane or

b. comprised by a tubular section made in a flexible material .

4. Submerged platform according to claim 1 in which the anchoring device consists of:

a. one or more anchors arranged in a matrix or b. a combination of foundations, stakes or similar devices embedded in the bed of the body of water wherein the platform is operating.

5. Submerged platform according to claim 1 in which the snorkel tube contains and envelopes a structural member connecting the submerged platform or devices contained in it to a subsystem above the free surface of the water and in which the contact between the snorkel tube and said structural member is made by any combination:

a. rollers;

b. bushings and

c. outwardly curved smooth surfaces.

6. Submerged platform according to claim 1 in which the snorkel tube contains a structural member which may be :

a. a cable, comprising a combination of:

i. structural elements;

ii. electrical cables;

iii. optical fibre cables;

iv. tubing for fluid transmission.

b. a transmission shaft, flexible or rigid.

7. Submerged platform according to claim 2 in which the articulation that allows the platform to rotate freely in the horizontal plane despite the anchoring cables is contained in a volume of non-water miscible fluid trapped in a compartment similar to a diving bell.

Lisbon, July 5th,