FR3106644A1 - Line for the supply of a hydrothermal energy production unit. - Google Patents

Abstract

The invention presents a pipe for supplying a hydrothermal energy production unit consisting of a plurality of segments formed by a module and a connection flange with the consecutive segment, characterized in that said segments comprise at least a positive buoyancy cavity filled with a material of lower density than sea water.

Description

Pipe for supplying a hydrothermal energy production unit.

Field of invention

The present invention relates to the field of ocean thermal energy (ETM) or tidal or hydrothermal energy (OTEC, for "Ocean thermal energy conversion"). This involves the production of renewable energy, in particular electricity, by exploiting the temperature difference between the surface waters and the deep waters of the oceans.

In his book, Twenty Thousand Leagues Under the Sea, Jules Vernes already mentioned the use of "surface waters and deep ocean waters to produce electricity". This idea was developed by the French physicist Arsène d'Arsonval, then Georges Claude, in the form of a closed circuit.

The principle consists in producing the energy thanks to a working fluid (sea water, ammonia or another fluid whose dew point is close to 4°C). This fluid passes from the liquid state to the vapor state in the evaporator, in contact with the hot water drawn from the surface. The pressure produced by the steam passes through a turbogenerator to turn a turbine and produce electricity, after the gas has lost pressure, it passes through a condenser to return to a liquid state, in contact with the cold water drawn from deep.

A floating or coastal power plant operating on this principle suggested by d'Arsonval in 1881 and tested by Georges Claude requires to deliver a power of 100 MW currently envisaged a flow of cold water of about 400 m3 / s drawn from 1000 m deep. . The power required for pumping is directly proportional to the pressure drop undergone by the fluid, itself proportional to the coefficient of friction of the wall and to the length of the pipe and, for a given flow, inversely proportional to the fifth power the diameter of the suction line. Thus, the limitation of this power imposes the installation of a pipe of very large diameter. In this case, for a suction speed close to 1 m/s, the diameter reaches 20 m.

In a floating hydrothermal power plant, the alternating and random forces that the floating platform on rough seas applies to a suspended rigid submerged pipe were the cause of the failure of the tests carried out by Georges Claude near the coast. Cubans in 1929-1930 and prosecuted off Rio de Janeiro from 1934 to 1935. Similar causes led to the abandonment of Engineer Nizery's project near Abidjan in the immediate post-war period.

To solve this problem, it has been proposed to use flexible, extendable and retractable underwater conduits between an undeployed state and an operational state, capable of conducting sea water from a lower end to an upper end at the in operational condition, particularly suitable for use in tropical areas where they generally have to withstand extreme environmental and weather conditions.

For example, a cyclone or a storm can seriously damage the pipe and render it unusable later. In some cases, it is even necessary to raise the pipe on the floating platform, for example if a weather warning announcing storms has been issued. Typically, these weather warnings are available two to three days in advance.

In known flexible pipe systems (see for example US Pat. No. 4,358,225), the pipe consists of a succession of annular modules which are progressively assembled together or disassembled.

Hydrothermal energy needs a very large flow of seawater to compensate for the low efficiency due to the low temperature gradient and large pipe diameters to limit pressure drops, typically HDPE (high density polyethylene) pipes. 1.5 meters in diameter. For a projected 5 MW plant and a flow of 20 m3/s, the pipe diameter still reaches 5 m.

The object of the present invention is to provide a flexible subsea pumping pipe system for supplying a hydrothermal energy production facility.

State of the art

Known in the state of the art is the patent FR3044380B1 water pumping pipe, in particular for an installation for the production of energy from the thermal energy of the seas, produced by assembling flexible pipe sections, using of rigid connecting flanges, characterized in that the opposite ends of the pipe sections comprise ropes adapted to be engaged in corresponding reception grooves of the flanges, in that these flanges comprise access passages to these grooves for a tool in the form of a hook for mounting/dismounting the ropes and in that it comprises motorized means for relative rotation of the pipe and the mounting/dismounting tool

We also know the patent FR2418898 describing a flexible conduit composed of cylindrical sections of reinforced elastic material, connected to each other by circles of rigid material, and an arrangement of cables extending in the longitudinal direction of the conduit and fixed to said circle. The duct can be assembled or disassembled thanks to its modular and composite constitution.

To balance the pipe, it has also been proposed to provide a reserve of buoyancy.

Patent FR2988424 describes a solution providing buoyancy elements secured to the connection parts and/or on the underside of the upper load-bearing structure to compensate for the weight of the flexible pipes and the various accessories.

US4497342 describes an OTEC cold water pipe designed to draw water to the ocean surface from a selected ocean depth. The proximal end of the cold water hose is attached to a floating surface structure (eg, a ship or a moored platform) on the ocean surface, and a distal end of the hose is expandable in the ocean to the selected depth.

The cold water pipe comprises a tubular fabric membrane surrounded by annular shaping rings to which the fabric membrane is attached.

The cold water pipe further includes annular shaping elements, which are configured as cylindrical rings that coaxially wrap around the fabric membrane. In the preferred embodiment, the shaping rings are floating. According to a variant described in this prior art document, each shaping ring is configured as a metal shell such as steel. Buoyancy can be provided by filling each shaping ring shell with a buoyant material such as a synthetic foam material. Alternatively, buoyancy can be achieved by fabricating the shaping rings to have internal watertight cavities. Shaping rings are attached to the fabric membrane at equally spaced intervals along the length of the pipe.

Patent application WO2010097528 describes a bottom-surface connection installation between a plurality of underwater pipes resting on the seabed and a floating support on the surface, of the multi-riser hybrid tower type comprising:

1. a tower comprising:
   1. a vertical tendon,
   2. a plurality of vertical rigid pipes
   3. a plurality of means for guiding the risers,
   4. buoyancy elements cooperating with said tendon,
2. a plurality of flexible connecting pipes.

The tower comprises a plurality of buoyancy and guidance modules constituting a plurality of independent structures capable of sliding along said tendon and along said risers, said structure supporting said buoyancy elements and guiding said risers in position preferably regularly and symmetrically distributed around said tendon.

Patent US9568133B2 describes a flexible coupling flange between a first fluid transport element and a second element movable relative to each other in the roll and pitch directions, comprising an articulated link which interconnects the first element fluid transport and the second member and a flexible, fluid impermeable bellows adjacent to the hinged link, which includes a first end attached to the first fluid transport member and a second end attached to the second member. The flange may have positive buoyancy to prevent folding of the bellows. The buoyancy of the bridle can be controlled by placing one or more buoyancy elements in the radially outward facing channels of the C-shaped rings of one or more of the ring segments.

Disadvantages of the prior art

The solutions of the prior art are not totally satisfactory because they lead to high manufacturing costs and complex ducts, the installation and maintenance of which are difficult and require interventions carried out by highly qualified operators.

Solution provided by the invention

In order to remedy these drawbacks, the invention relates, in its most general sense, to a flexible pipe consisting of a plurality of flexible modules for supplying a hydrothermal energy production unit, the respective ends of two consecutive modules being connected by a connecting flange, characterized in that the connecting segments consist of two connecting ends and a module comprising a toroidal cavity filled with a material of lower density than sea water.

According to variants:

• the ends of each of said modules have an annular protuberance, and in that said connection flange bears on said annular protuberances and is provided with an annular extension defining said toroidal cavity filled with a material of lower density than water of sea.
• said flange is formed of two complementary flanges and by longitudinal clamping means, and by a tube defining said toroidal cavity connected to said flanges by connectors having fastening means cooperating with said clamping means
• said flange is formed of two complementary flanges and by longitudinal clamping means, and at least one of said flanges having a rigid body having a toroidal cavity filled with a material of lower density than seawater.
• the ends of each of said modules have an annular protuberance defining a transverse shoulder, and in that said connection flange is provided with an extension defining said toroidal cavity filled with a material of lower density than seawater.

According to particular embodiments:

- said material with a lower density than seawater consists of oil.

- said material with a lower density than seawater consists of a syntactic foam.

- said material with a lower density than seawater consists of hexane.

Preferably,

- said modules have a length of between 0.5 meters and 25 meters, and preferably between 5 meters and 10 meters

- Said modules have a diameter of between 60 centimeters and 600 centimeters, and preferably between 1 and 3 meters.

Advantageously, said modules consist of assemblies of sealed flexible panels.

Detailed description of non-limiting embodiments

The present invention will be better understood on reading the following description, with reference to the appended drawings illustrating non-limiting examples of embodiment, where:

FIG. 1 represents a schematic view of a first embodiment variant

FIG. 2 represents a view of a second embodiment variant

FIG. 3 represents a view of a third embodiment variant

FIG. 4 represents a sectional view of an example of means for locking the flange in the unlocked position

FIG. 5 represents a sectional view of an example of means for locking the flange in the closed position.

FIG. 6 represents a sectional view of an example of means for locking the flange in the locked position.

First embodiment: corrugated tubes

FIG. 1 represents a schematic view of a first embodiment variant, with part of the duct formed of two consecutive modules (100, 200) connected by a flange (150).

The modules (100, 200) are formed by segments of corrugated tube which can be either flexible or rigid, covered with a skin (102, 202).

The tube (101, 201) is in the example described in FIG. 1 ringed on the outside and smooth and cylindrical on the inside. It is for example a PVC or HDPE tube with an outside diameter varying sinusoidally between 1200 and 1220 millimeters and an inside diameter of 1100 millimeters, and a length of 6 meters, with walls of a thickness varying between 80 and 100 millimeters. It has a rigidity of CR8 (≥8 kN/m ² ).

The outer skin (102, 202) surrounds the tube (101, 201), its inner section being approximately 1220 millimeters, and the helical channel (103, 203) formed by the space between the outer wall of the corrugated tube (101 , 201) and the inner surface of the skin (102, 202) forms a volume in which is poured a material with a density lower than that of sea water, for example an oil or vegetable with a density between 0.840 and 0.960, a hydrocarbon with a density of between 0.6 and 0.8 or a syntactic foam with a density of the order of 0.6.

The two consecutive modules (100, 200) are joined by an assembly flange (150) consisting of two shells (151, 152) joined together by bolts (153 to 155). These shells (151, 152) have shoulders bearing on the ends of the tubes (101, 102) flared in the shape of a tulip having an outer diameter of 1380 millimeters.

Second embodiment: flotation tube surrounding the flange

This second embodiment is not exclusive of the first embodiment. It is perfectly possible to add to an embodiment conforming to the first mode buoyancy rings (160) which are fixed on the flange (150).

The modules (100, 200) are made in the example described in a flexible material, for example high density polyethylene (HDPE) 1.5 meters in diameter in the non-limiting example described, and a length of 5 meters each. They are advantageously made by assemblies of sheets (201 to 208) of rubber or other or waterproof material, connected by waterproof seams to form a tile.

The two ends of the modules (100, 200) have annular sections (110, 120; 210, 220) of larger section to form shoulders intended for the attachment of a connecting flange formed of two flanges (130, 140 ; 230, 240).

These two flanges (130, 140; 230, 240) have a tubular skirt (131, 231) whose inner section corresponds to the outer section of the annular sections (110, 120; 210, 220), and a disc restriction (132 , 232) are joined by bolts (131, 132; 231, 232) corresponding to the front surface of the shoulders formed by the annular sections (110, 120; 210, 220) and transverse lugs (134 to 136) for connection by the bolts (137; 138).

Peripheral fittings (150, 160) fixed by the same bolts (137; 138) on the flanges ensure the maintenance of positive buoyancy tubes (180, 280) containing an element of density lower than that of sea water, for example a mineral or vegetable oil, with a density of between 0.840 and 0.960, a hydrocarbon with a density of between 0.6 and 0.8 or a syntactic foam with a density of the order of 0.6.

The volume of the toric cavity formed by the tube (180, 280) is defined to compensate for the weight of the module and the fitting in sea water.

Third embodiment: toroidal buoyancy reserve integrated into the module

This third embodiment is also not exclusive of the first two embodiments. The solution of a toroidal buoyancy reserve integrated into the module can be associated with the above solutions.

According to this third mode, the tube (100) has an enlarged end (106) of tubular or toroidal shape, hollow to form a toric cavity (180, 181; 280) defined to compensate for the weight of the module and of the fitting in the water. of sea.

The assembly flange (150) is made up of two disc flanges joined by bolts. These modules also include vertical or helical reinforcement elements in order to limit the displacements of the pipe during the flow of the cold water pumped inside the pipe and also the drag or resistance forces of the pipe in the pipe. environment marine environment, sea currents.

The flanges also include several rings between 4 and 8 per flange in order to be able to keep the pipe in a vertical position. The structure is therefore composed of 4 lines to 8 lines linked to the platform, holding a dead body of sufficient weight to overcome the drag forces of the pipe.

To lighten the pipe, the assembly flange can be made of fiberglass.

Cam lock system

The connection of the flanges of the flange by bolts can be replaced by a locking (600) by a lever-cam system illustrated in Figures 4 and 5, consisting of a lever (310) articulated with respect to a transverse axis (315) linked to one of the flanges (130). The other end of the lever (310) carries a second axis (325) parallel to the first axis (315).

This second axis (325) ensures the articulation of a cam (350) with respect to the lever (310). This cam (350) has a lever (351) and a curved part defining a sliding surface (352) whose radius, relative to the axis (325), evolves between a minimum value, to increase up to a value corresponding the distance between the two axes (315, 325) less the cumulative thickness of the two flanges (130, 140), then to decrease very slightly to ensure a stable locking position.

A compressible O-ring (330) is disposed in a groove between the two flanges (130, 140).

The operation is as follows:

The assembly is first tilted by pivoting the lever (310) supporting the cam (350) by 90° so that the axis (325) is aligned vertically to the axis (315). During this movement, the cam (350) maintains its initial orientation with respect to the lever (310), and its sliding surface (325) comes to bear against the lower surface of the flange (140), with a play due to the radius reduced in this position.

The next step is to rotate the cam (350) around its axis (325) through an angle slightly greater than 90°. At 90°, the cam (350) ensures maximum tightening of the two flanges (130, 140). By exceeding this angle, the radius of curvature being reduced slightly, a stable relaxation position is found in which the cam (350) ensures the locking of the two flanges (130, 140) in a durable manner.

Holding structure

In order to ensure the maintenance of the distal end of the duct, one solution consists in providing a ballast connected to the platform by cables passing in a sliding manner in the guides provided in the connection flanges of the duct modules. The modules have neutral buoyancy, and there is therefore no mass gradient acting on the conduit, the verticality of which is ensured by the cables connecting the ballast to the platform.

Claims (15)

- Pipe for supplying a hydrothermal energy production unit consisting of a plurality of segments formed by a module (100, 200) and a flange (150) for connection with the consecutive segment, characterized in that said segments include at least one cavity (103, 203,180) of positive buoyancy filled with a material of lower density than sea water. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules (100, 200) consist of a corrugated tube (101, 201) covered with an outer skin (102 , 202), the space (103, 203) comprised between the ringed outer surface and said skin constituting said cavity of positive buoyancy. - Pipe for supplying a hydrothermal energy production unit according to claim 1 or 2 characterized in that the ends of each of said modules (100, 200) have an annular protrusion, and in that said connecting flange bears on said annular protuberances and is provided with an annular extension defining said toroidal cavity filled with a material of lower density than sea water. - Pipe for supplying a hydrothermal energy production unit according to claim 1, 2 or 3 characterized in that the module (100, 200) comprising a toroidal cavity filled with a material of lower density than water of sea. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said flange is formed of two complementary flanges and by longitudinal clamping means, and by a tube defining said toroidal cavity connected to said flanges by connectors having fastening means cooperating with said clamping means. - Pipe for supplying a hydrothermal energy production unit according to claim 2 characterized in that said flange is formed of two complementary flanges and by longitudinal clamping means, and at least one of said flanges having a rigid body having a toroidal cavity filled with a material of lower density than sea water. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that the ends of each of said modules have an annular protrusion defining a transverse shoulder, and in that said connection flange is provided with an extension defining said toroidal cavity filled with a material of lower density than sea water. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said material of lower density than sea water consists of oil. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said material of lower density than seawater consists of a syntactic foam. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said material of lower density than sea water consists of hexane. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules have a length of between 0.5 meters and 25 meters, and preferably between 5 meters and 10 meters. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules have a diameter of between 60 centimeters and 600 centimeters, and preferably between 1 and 3 meters. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules (100, 200) consist of assemblies of sealed flexible panels. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules (100, 200) consist of rigid tubes. - Pipe for supplying a hydrothermal energy production unit according to claim 1 characterized in that said modules (100, 200) are connected by an assembly flange comprising at least one lever-cam system.