WO2009096796A2

WO2009096796A2 - Wave energy device

Info

Publication number: WO2009096796A2
Application number: PCT/NO2009/000031
Authority: WO
Inventors: Runar Tenfjord
Original assignee: Tenko
Priority date: 2008-01-31
Filing date: 2009-01-27
Publication date: 2009-08-06
Also published as: NO20080579L; WO2009096796A3

Abstract

A device for converting wave energy, in the form of a hollow, elongated body that floats on the surface of the water and having one end anchored to the seabed by a mooring line. The elongated body is divided into a plurality of chambers, and at least one of said chambers is partially filled with a liquid. At least one chamber is adjacent to the liquid-filled chamber and is filled with a gas. The liquid-filled chamber is separated from the gas-filled chamber by a movable plate operably connected to a bellows, whereby the bellows is arranged to compress and create a gas flow in the event the device is tilted by a wave such that the liquid presses against the plate. A turbine is arranged in the gas-filled chamber such that the gas flow created by the compressed bellows drives the turbine.

Description

WAVE ENERGY DEVICE

The present invention relates to devices for converting wave energy to another form of energy.

Several devices and systems have been proposed for the generation of useful power by converting the energy from waves. US4145882 discloses a device comprising a bag of flexible, impervious material filled with a liquid. The liquid within the bag is subject to an undulating motion in response to the movement of the waves, which undulating motion creates currents that drive a turbine. WO 84/00583 discloses a device for harnessing surface wave energy comprising a tube divided into sections separated by non-return valves. Each section is divided into chambers by a flexible membrane, one of which chambers is partially filled with liquid. The wave motion creates movement in the liquid, which causes a pumping action of the liquid through the non-return valves that may be used to drive a turbine. US 5329437 discloses a device comprising a float attached to a vertically arranged, extendable pump made of a material that expands radially when shortened in the longitudinal direction. The wave motion displaces the float, which activates the pumping action of the device. GB2261262 discloses a device comprising a float mounted on a column and arranged with shafts and gears that allow pivotal motion. Oscillation of the float results in rotary motion that drives a generator. US 4375151 discloses a device whereby the hydrostatic pressure of a passing wave crest causes collapse of flexible bags pumping air from the bags via a non-return valve into a high pressure air conduit. The bags are refilled in a wave trough from a low pressure air conduit. A turbine is driven by the movement of air between the high pressure and low pressure conduits. WO 2006/079823 discloses a wave energy converter comprising a first container for containing a volume of fluid, the container having a first end and a second end, buoyancy means disposed at the first end of said first container, a turbine disposed in the first container and resistance means disposed adjacent the second end of the first container and means for compressing the first container in response to separation of the buoyancy means and the resistance means. Movement of the buoyancy means by wave motion compresses the first container, which causes a liquid disposed in the container, to pass through and drive the turbine.

All of the above, as well as similar devices have disadvantages known to those skilled in the art, including but not limited to complicated construction, excessive maintenance requirements, limited effectiveness, and inconvenience of construction and use. It is therefore an object of the present invention to provide an improved device for converting wave energy to another useful form of energy.

The objects of the present invention are achieved by providing a device comprising a hollow, elongated body that floats on the surface of the water and having one end anchored to the seabed by a mooring line. The elongated body is divided into a plurality of chambers, and at least one of said chambers is partially filled with a liquid. At least one chamber is adjacent to the liquid-filled chamber and is filled with a gas. The liquid-filled chamber is separated from the gas-filled chamber by a movable plate operably connected to a bellows, whereby the bellows is arranged to compress and create a gas flow in the event the device is tilted by a wave such that the liquid presses against the plate. A turbine is arranged in the gas-filled chamber such that the gas flow created by the compressed bellows drives the turbine, whereby the rotational energy of the turbine can be converted to another useful form of energy by means known in the art, such as for example converted to electrical energy in a generator, hydraulic energy in a pump etc.

Examples of possible embodiments of the invention will be described in detail with reference to the attached figures, wherein:

Fig 1 is a perspective view of a first embodiment of the device according to the invention.

Fig 2 is a longitudinal cross sectional view of the device from fig 1.

Fig 3 is a lateral cross sectional view of the device from fig 1.

Fig 4 is a perspective view of a second embodiment of the device according to the invention.

Fig 5 is a longitudinal cross sectional view of the device from fig 4.

Fig 6 is a lateral cross sectional view of the device from fig 4.

Fig 7 is a perspective view of a third embodiment of the device according to the invention.

Fig 8 is a longitudinal cross sectional view of the device from fig 7.

Fig 9 is a lateral cross sectional view of the device from fig 7.

A first embodiment of the invention is a closed system as shown in figs 1-3. As shown in the figures, the device comprises a floatable, elongated, hollow body 10. Elongated body 10 is preferably cylindrical in cross section as shown in fig 3, and is preferably constructed of welded construction steel or corrosion resistant aluminum, though reinforced plastic or other suitable engineering materials could also be used. Elongated body 10 is intended to float on the surface in an area with sufficient wave motion as to be an attractive area for wave power generation. The length of the elongated body will vary depending upon the expected characteristics of the waves at the intended location of use, but will preferably have a length approximately half of the expected wave length of the major waves occurring at the location. A chain or mooring line 11 is attached at one end of elongated body 10 which is used to anchor the device to the seafloor. (not shown).

Elongated body 10 is divided into three chambers, a first partially liquid-filled chamber 12, a second gas-filled chamber 14 and a third gas-filled chamber 16. The liquid in chamber 12 is preferably water, however other fluids with comparable properties could be utilized, (e.g. brine with higher densities). The gas in chambers 14 and 16 is preferably air, however an inert gas could alternatively be used instead of air. Liquid filled chamber 12 is separated from the respective air-filled chambers by movable plates 18 that are operably connected to flexible bellows 20 disposed in the respective air-filled chambers. Plates 18 are preferably constructed of fiber- reinforced plastic or wood for light weight. A sealing member 22 creates a moveable, yet air and liquid tight seal between the plate 18 and the walls of elongated body 10. Bellows 20 are preferably constructed of reinforced synthetic rubber or an elastomer having similar properties. Third chamber 16 is in fluid connection with second chamber 14 via conduits 24 arranged longitudinally along the outside of elongated body 10.

When the device according the invention is anchored to the seafloor, it will naturally assume an orientation in the direction of the wave propagation. The passage of a wave crest will cause a rocking motion of the device. When the device tilts, the rushing liquid in first chamber 12 will press against one of plates 18, compressing its respective bellows, forcing air through conduits 24 into the other air filled chamber. As shown in fig 2, a unidirectional air turbine 26 (that is, one capable of providing unidirectional rotation from bidirectional air flow) is arranged in second chamber 14, such that the above-described air flow rushes past and rotates the blades of the turbine. The turbine is preferably of the "Wells" type, supported in chamber 14 by aerodynamically-shaped struts 28. A focusing nozzle 30 is arranged to create a Venturi effect increasing the speed of the air directed towards the turbine. When the device tilts back in the other direction, the liquid compresses the opposite bellows, creating a flow of air moving past the turbine in the opposite direction. The unidirectional turbine generates rotating mechanical energy which can be converted to another form of energy, for example electrical energy in a generator, hydraulic energy in a pump etc. A second embodiment of a device according to the invention is shown in figs 4-6. This embodiment is also a closed system as in the case of the first embodiment. In this embodiment, elongated body 10 is divided into five chambers, a first liquid- filled chamber 32, second liquid-filled chamber 34 a third liquid-filled chamber 36, a fourth air-filled chamber 38 and a fifth air-filled chamber 40. In this embodiment, the air-filled chambers are not in fluid connection with each other. Rather, the fourth air filled chamber is arranged between first liquid-filled chamber 32 and second liquid-filled chamber 34, and fifth air filled chamber 40 is arranged between first liquid-filled chamber 32, third liquid-filled chamber 36. As shown in fig 5, a plate 18 and bellows 20 is arranged at both ends of each air-filled chamber separating it on both sides from the two adjacent liquid-filled chambers. As shown in fig 2, when the device tilts to the right, the liquid in first chamber 32 will collapse the left hand bellows of chamber 38 and the liquid in third chamber 36 will collapse the left hand bellows of chamber 40. When the device tilts in the opposite direction, the opposite bellows will collapse, and the previously collapsed bellows will expand. As shown in fig 2, a unidirectional turbine is arranged in each of the air-filled chambers similar to the first embodiment.

A third embodiment of a device according to the invention is shown in figs 7-9. This embodiment is an open system. In this embodiment, elongated body 10 comprises a single partially liquid-filled chamber 42. At each end of this chamber is arranged a vertical, tower-like chamber 44. At the bottom of each chamber 44 is arranged a plate 18 and bellows 20. Chambers 44 are open to the outside at their upper ends, and are protected form rain and spray by domed covers 46. As illustrated, a unidirectional turbine is arranged in each of chambers 44. In this embodiment, when the device tilts, water in chamber 42 will rush to one end, and press plate 18 upwards, forcing air out of the chamber through the open top, thus creating a flow of air that drives the turbine. When the device tilts in the opposite direction, gravity will force the plate downward, creating an intake of air into the chamber that also creates a flow of air past the turbine. Plates 18 may in this embodiment be weighted.

Claims

1. A device for converting wave energy to another form of energy comprising a hollow, elongated body that floats on the surface of the water characterized in that a. The elongated body is divided into a plurality of chambers, b. At least one of said chambers is partially filled with a liquid, c. At least one chamber is adjacent to the liquid-filled chamber and is filled with a gas, d. The liquid-filled chamber is separated from the gas-filled chamber by a movable plate operably connected to a bellows, whereby the bellows is arranged to compress and create a gas flow when the device is tilted by a wave and the liquid presses against the plate, and e. A turbine is arranged in the gas-filled chamber such that the gas flow created by the compressed bellows drives the turbine, whereby the rotational energy of the turbine can be converted to another useful form of energy.

2. A device according to claim 1, characterized in that a. the device is anchored to the seabed by a mooring line, b. the bellows is arranged to expand in the event the device tilts in the opposite direction, thereby creating a reverse gas flow past the turbine in the opposite direction, c. the turbine is a unidirectional turbine of the type that creates unidirectional rotation from bidirectional fluid flow.

3. A device according to claim 2, characterized in that the device further comprises venturi means for increasing the speed of the gas flow towards the turbine.

4. A device according to claim 3, characterized in that the liquid is water and the gas is air.

5. A device according to claim 4, characterized in that elongated body is cylindrical in cross section, and that the length of the device is approximately equal to half the expected average wavelength at the intended site of deployment.

6. A device according to any one of claims 1-5, characterized in that the interior of the elongated body is closed to the outside atmosphere, the liquid filled chamber is intermediate a first gas-filled chamber in which is arranged the turbine, and a second gas-filled chamber, both of which are separated from the liquid-filled chamber by respective plates operably connected to respective bellows, and that a conduit extends from the second gas-filled chamber to the first gas filled chamber for passage of gas as the respective bellows expand and contract.

7. A device according to claim any one of claims 1-5, characterized in that the interior of the elongated body is closed to the outside atmosphere, that a first gas-filled chamber in which is arranged a first turbine is intermediate a first liquid-filled chamber and a second liquid-filled chamber, and a second gas- filled chamber in which is arranged a second turbine is intermediate the first liquid-filled chamber and a third liquid-filled chamber, and that the gas-filled chambers are separated from their adjacent liquid-filled chambers by plates operably connected to bellows.

8. A device according to claim any one of claims 1-5, characterized in that a liquid-filled chamber is arranged longitudinally along the length of the elongated body, that at each end of the elongated body is arranged a vertically oriented chamber, said vertical chambers being in fluid connection to the outside atmosphere, and being separated from the liquid-filled chamber at their lower ends by movable plates operably connected to bellows, and that a turbine is arranged in each of the respective vertical chambers.

9. A device according to claim 8, characterized in that the device further comprises a covering on the upper end of each vertical chamber, said coverings having openings on their lower sides allowing the passage of air into the interior of the vertical chambers.

10. A device according to claims 9, wherein the plates are weighted.