Wave energy unit

Abstract

A wave energy unit comprises a primarily vertical column (1), a float (3) designed to float on a water surface at sea and is movable along the column, at least one riser (6a) connected to the float (3) and thereby movable along the column (1) together with the float (3), and at least one feed tank (6b) associated with the column. The feed tank (6b) includes a lower one-way valve (32). The riser (6a) has at its lower end an upper one¬ way valve (31) which is received vertically movable in the feed tank (6b), so that the feed tank (6b) and the riser (6a) function as a piston pump that pumps water from the surrounding sea and up through the riser (6a) when the float (3) moves relative to the column (1) due to wave action.

Description

WAVE ENERGY UNITTechnical Field

[0001] The present invention describes a wave-driven system in the form of a wave energy unit for lifting water to an equalizing tank with sufficient head height to drive a conventional turbine for electric power generation.

[0002] KR 20030000395 describes a hydroelectric power plant where a water tank is placed on top of a barge floating on water. Water from the tank is used to generate electricity by being directed through a generator also located on the barge. Water is pumped into the tank from a pressure tank placed underwater via a riser pipe. An air pump, also located on the barge, provides overpressure in the underwater tank via a bubble pipe.

[0003] This power plant is not a wave power plant as it is evident that it does not rely on level differences. To the extent that any surplus energy is created, energy supply will still be required to operate the air pump.

[0004] NL2012880B1 describes a wave power plant that is fixedly connected to a mountainside and has a floating element that can tilt back and forth in the waves. The tilting drives a pump that pumps water up a riser pipe and into a water reservoir. The water from the reservoir drives a turbine.

[0005] This power plant must be connected to a vertical wall on land, and therefore, its placement is very limited. Since the floating element only tilts, the amount of wave energy that can be utilized is also limited.

[0006] EP2511519A1 describes a wave power plant designed to either stand on the seabed or be firmly anchored to the seabed. A floating element moves relative to the seabed, and the varying distance between the seabed and the floating element drives a pump that pumps water from the sea up onto a fixed platform. Since the power plant depends on a platform standing on the seabed, its placement is limited.

[0007] US5986349 describes a wave power plant comprising a vertical column with a floating element surrounding it. Several hydraulic cylinders are connected between the floating element and the column. Relative movement between the column and the floating element causes hydraulic fluid to be pumped from the cylinders to a generator.Brief Summary of the Invention

[0008] The wave energy unit according to the invention comprises a column, which can be floating or fixed to the seabed, and is placed offshore or in a large lake. The column can also serve as a foundation for a tower for a wind turbine generator. A float, which can be a barge with shallow draft, follows the vertical wave movements. Using one or more installed riser pipes, the barge lifts water to an equalizing tank placed at a suitable head height above the water surface to drive a hydroelectric turbine located inside the column. The turbine can be of a conventional and well- proven type. The column has no heave movement, i.e. , vertical movement, so the relative vertical movement generated by the waves between the barge and the column is used to lift water to the equalizing tank. The system is designed so that the barge has three degrees of freedom of movement: heave, roll, and pitch, while the other three, surge, sway, and yaw, are arrested by the column. The conventional water turbine — preferably of the Kaplan type — is well-proven and has high efficiency and regulation capability. The described invention will also have high efficiency for utilizing wave energy. The system is designed to generate as much electrical energy driven by the waves as the wind turbine generates from the wind, thereby doubling the total energy delivery from the installation.Detailed Description of the Invention

[0009] Figure 1 shows a wave energy unit according to the invention with a tower for a wind turbine,

[0010] Figure 2 shows the unit in Figure 1 viewed from below,

[0011] Figure 3 shows a section through the unit in Figure 2,

[0012] Figure 4 shows a section through the float with riser pipes,

[0013] Figure 5 shows an isometric view and section of a one-way valve connected to the riser pipe,

[0014] Figure 6 shows a schematic section through a feed tank with one-way valves and illustrates an upward movement for the riser pipe,

[0015] Figure 7 shows a column with a turbine and equalizing tank,

[0016] Figure 8a shows the float as it passes a wave crest,

[0017] Figure 8b shows the float as it passes a wave trough, and

[0018] Figure 9 shows a detailed section through the feed tank and illustrates a downward movement for the riser pipe.

[0019] The wave energy unit according to the invention is illustrated in Fig. 1 , where 1 is the column extending through the water surface. It has an equalizing tank 2 mounted on the column 1 at a suitable head height, which can be 2-10 meters or more, above the water surface 4 and above a float 3 floating on the water surface 4. The column 1 , which either constitutes the upper part of a seabed-fixed structure or a semi-submersible floating unit arrested against heave movements, e.g., by tension leg anchoring or by a damping skirt. This can also serve as a foundation for a tower for a wind turbine generator 5.

[0020] Fig. 2 shows the installation viewed from below up towards the water surface 4 and shows the column 1 as well as the float 3 and feed tanks 6b fixedly mounted on the column 1 . The column 1 and float 3 are visible below the water surface 4. The equalizing tank 2 placed at a suitable head height above the water surface is not visible here.

[0021] Fig. 3 shows the installation according to the invention in section. The feed tanks 6b are fixedly mounted on the column at a sufficient depth to clear the float 3 at the deepest wave troughs. Riser pipes 6a extend through the float 3, and each riser pipe 6a has at its lower end an intake 7 fluidly connected to each feed tank 6b. In thefeed tank, there is an upper one-way valve (check valve) 31 and a lower one-way valve (check valve) 32. The upper one-way valve 31 is fixedly connected to the riser pipe 6a and can move inside the feed tank 6b while the lower one-way valve 32 is fixed in the feed tank 6b. The one-way valves will be explained in more detail below. The riser pipe 6a and the feed tank 6b, together with the one-way valves 31 and 32, constitute a riser assembly 6. A turbine and generator assembly 8 is shown inside the column 1 .

[0022] Fig. 4 shows the float 3 and the riser assembly 6 in section. The riser pipes 6a are suspended in a gimbal 9, i.e. , a cardan suspension, so that the riser assemblies can move vertically with the float 3. Instead of a mechanical two-axis cardan suspension, a suitable composite arrangement can be used. Alternatively, another type of flexible suspension that allows the float 3 to move with the waves in pitch and roll directions while still allowing the riser pipes 6a to be held in a vertical position can be used. The riser pipes have a 180-degree bend 11 at the top to direct the water flow into the equalizing tank 2 (not shown in Figure 4). Centering rollers 12 are arranged on the float and rest against the wall of the column 1 (not shown in Figure 4), allowing the float 3 to move unhindered along the column 1 . Alternatively, sliding shoes in some form can also be used. The material PTFE against stainless steel in a marine atmosphere has shown good wear properties. The rollers 12 also have side guides — not shown — to arrest the rotation of the float 3 about the vertical axis. The float 3 has the shallowest possible draft and the largest practical diameter to optimally utilize the surface energy of the waves.

[0023] Fig. 5 shows in section the upper one-way valve 31 , which is connected to the intake 7 of the riser pipe 6a. The upper one-way valve 31 has a housing 31 b enclosing a valve chamber 31a, in which a valve element 13, a seat 14 for the valve element 13, and a stroke limiter 15 are arranged. The valve element 13 and the seat 14 are made of materials that provide optimal sealing and wear resistance. The valve element is here shaped like a ball but can also have an alternative shape. It must have a suitable specific weight to seal against the seat 14 by gravity and easily lift off when the fluid flow acts upwards.

[0024] Fig. 6 shows a section through the feed tank 6a and shows both the upper one-way valve 31 and the lower one-way valve 32. The lower one-way valve is designed in the same way as the upper one-way valve 31 with a valve element 16, a valve seat 17, a valve chamber 32a, and a stroke limiter 18 for the valve element 16.

[0025] The lower one-way valve is open to the sea via the valve seat 17. The upper one-way valve 31 is connected to the riser pipe 6a. The illustration in Figure 6 indicates the riser pipe 6a during the lifting sequence. The riser pipe 6a and the oneway valve 31 move upwards in the feed tank 6b. Due to the weight of the water in the riser pipe 6a, the valve element 13 seals against the seat 14 and holds the fluid volume in the riser pipe 6a enclosed. The suction created in the feed tank 6b as the riser pipe 6a moves upwards causes the valve element 16 to lift off the seat 17 until it is stopped by the stroke limiter 18, allowing the feed tank 7 to fill with water from the surrounding sea in sync with the upward movement of the riser pipe 6a. The outer diameter of the valve housing 31 b is crucial for the system's capacity. This determines the area of the 'pump piston' for each riser pipe, and this multiplied by the number of riser pipes and the actual wave height gives the amount of water lifted to the equalizing tank 2 for each wave.

[0026] Fig. 7 shows a section of the upper part of the system. Here, the column 1 with the equalizing tank 2 and a downflow opening 19 from the equalizing tank 2 to the turbine and generator assembly 8 are shown. The turbine preferably has adjustable guide vanes 20 and adjustable runner blades 21 . The centering rollers 12 are also shown.

[0027] Fig. 8 shows the system in two extreme operational phases. Fig. 8a shows the float 3 at the top of a wave crest — indicated with the water surface 4 and here illustrated with 5 degrees of inclination — in pitch and roll directions. Fig. 8b shows the float 3 at the bottom of a wave trough — indicated with the water surface 4 and here illustrated with 5 degrees of inclination — in pitch and roll directions in the opposite direction.

[0028] Fig. 9 shows an enlarged section showing parts of the upper one-way valve31 and the lower one-way valve 32, with parts of the valve housing 31 b, the feed tank6b, the valve elements 13 and 16. The slot opening 22 indicates a contactless and seal-free clearance between the outer wall of the valve housing 31b and the inner wall of the feed tank 6b. The limited slot opening and the length of the overlap are intended to provide enough backpressure properties for acceptable leakage loss. Here, it is illustrated that the riser pipe 6a with the upper one-way valve 31 moves downwards relative to the feed tank 6b. The valve element 13 then lifts off the seat 14 while the valve element 16 is pressed down against its seat 17. Thus, the riser pipe 6a is filled with water from the feed tank 6b.

Claims

Patent Claims1 . A wave energy unit, characterized by comprising a primarily vertical column (1 ), a float (3) arranged to float on a water surface (4) at sea and movable along the column (1 ), at least one riser pipe (6a) connected to the float (3) and thereby movable along the column (1 ) together with the float (3), and at least one feed tank (6b) connected to the column (1 ), where the feed tank (6b) comprises a lower oneway valve (32) and the riser pipe (6a) at its lower end has an upper one-way valve (31 ), received vertically movable in the feed tank (6b), so that the feed tank (6b) and the riser pipe (6a) function as a piston pump that pumps water from the surrounding sea and up through the riser pipe (6b) when the float (3) moves relative to the column (1 ) due to wave action.

2. The wave energy unit according to claim 1 , characterized by comprising an equalizing tank (2) placed at a level above the water surface and that the upper part of the at least one riser pipe (6a) is fluidly connected to the equalizing tank (2).

3. The wave energy unit according to claim 2, characterized by the equalizing tank (2) being placed lower than the upper end of the at least one riser pipe (6a) and that the riser pipe (6a) comprises a bend (11 ) directing water down into the equalizing tank (2).

4. The wave energy unit according to claim 2 or 3, characterized by the equalizing tank (2) being fluidly connected to at least one turbine (8) placed lower than the equalizing tank (2).

5. The wave energy unit according to claim 4, characterized by the at least one turbine (8) being placed inside a cavity in the column (1 ).

6. The wave energy unit according to any of the preceding claims, characterized by the float (3) surrounding the column (1 ) and being equipped with rollers (12) or sliding shoes acting against the surface of the column (1 ) and allowing the float (3) to tilt relative to the column (1 ).

7. The wave energy unit according to any of the preceding claims, characterized by the at least one riser pipe (6a) being suspended in the float (3) via a flexiblecoupling (9) allowing tilting movement between the riser pipe (6a) and the float (3), such as a gimbal or an elastic element.

8. The wave energy unit according to any of the preceding claims, characterized by the one-way valves (31 , 32) comprising a valve element (13, 16) with negative buoyancy and a seat (14, 17) against which the valve element (13, 16) is arranged to seal, as well as a stroke limiter (15, 18) preventing the valve element (13, 16) from moving far from the valve seat (14, 17).

9. The wave energy unit according to claim 8, characterized by the feed tank (6b) having a larger diameter than the riser pipe (6a).

10. The wave energy unit according to any of the preceding claims, characterized by comprising several riser pipes (6a) and feed tanks (6b) arranged around the column (1 ).11 . The wave energy unit according to any of the preceding claims, characterized by the column (1) constituting a foundation for a tower (5) for a wind turbine.

12. The wave energy unit according to any of the preceding claims, characterized by the column (1) being fixed to the seabed or anchored so that it is minimally vertically movable.

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