GB2410983A

GB2410983A - A device for converting ocean wave energy into electrical energy

Info

Publication number: GB2410983A
Application number: GB0402340A
Authority: GB
Inventors: Andrew Cassius Evans
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-02-03
Filing date: 2004-02-03
Publication date: 2005-08-17
Anticipated expiration: 2024-02-03
Also published as: GB0616153D0; GB0402340D0; GB2430711A; GB2430711B; GB2410983B

Abstract

The device, to be known as an ocean wave energy converter or OWEC, consists of a container that is installed on the open sea. The container is secured to the seabed to maintain an approximately constant height relative to the ocean floor. As each wave passes, the container is alternately filled and emptied with seawater through pipes in the sides of the containers. These pipes may be fitted with mono or bi-directional valves to regulate the flow of seawater. The pipes may also be arranged at an angle that is not parallel to the direction of the force of the water on the container so that the inflow and/or outflow create a torque, rotating the OWEC. The flow of seawater through the pipes may also act to turn turbine rotors fitted in the pipes. This rotation can be used to power an electrical generator or generators.

Description

1 24 10983

Description

A device for converting ocean wave energy Into electrical energy to be known as the ocean wave energy converter (OWEC) The energy of ocean waves is immense and one of the largest renewable resources of energy that can be harvested by mankind. Ocean wave energy is useful to mankind not only due to its energetic potential but also, unlike wind, is not reliant on local weather conditions, as waves may travel thousands of miles with little energy dissipation.

There have been many attempts to harvest wave energy. The main problems being: 1) The energy of the waves is greatest in open sea far from shore, for example in some area offthe North Atlantic ridge swell heights can average about 8 metros.

Closer to shore, wave energy is dissipated due to bottom friction and diffrachon effects. Under deep-water conditions installation of wave energy converters can be difficult and expensive. Shore based wave energy converters are easier to install but have lower theoretical capacity and a greater environmental impact.

2) Many wave energy converters use floats that bob up and down on the wave with relation to the seabed, this movement may be used to generate electricity. However these type of energy converters intrinsically only harvest a small propose on ofthe wave's energy even reerected in open sea.

3) A wave's kinetic energy could be regarded as linear, either parallel or perpendicular to the gravity of the earth. The energy that is parallel to the earth's gravity can be looked at as alternating in direction. Some of the most common electricity generating methods are based on one way linear flows of kinetic energy that create a rotation of magnets or coils of wire about a central axis (a generator). Many methods for converting wave energy to electrical energy have low efficiencies when attempting to convert alternating linear energy to the unidirectional rotation of a generator shaft.

A successful ocean wave energy converter should therefore comprise some or all of the following It should be easy to erect in the open sea, it should function whatever the direction of the waves, it should harvest a large amount of the total energy of the wave, it should convert the alternating linear kinetic energy of the wave to unidirectional rotation of a generator shaft and it should be relatively simple to construct in open sea and deep water.

The ocean wave energy converter or OWEC described here fulfils all these criteria.

Figure I is a not to scale cross sectional schematic of an OWEC Figures 2S are schematic illustrations of the flow cycle of seawater through the OWEC during operation Figures 6 and 7 give an example of top views of an OWEC showing how the inflow (6 and outflow (7) pipes could be arranged for the flow of a wave (9) through them could create a torque around a central axis, enabling the device to spin.

Figure 8 gives three examples of how the pipes could be shaped as to increase electricity output from the OWEC The OWEC (Figure] ) essentially consists of a container ( 1) tatted with a number of pipes that facilitate the inflow (6) and outflow (7) of water between the container interior and the ocean. The OWEC is placed on the water and is partially submersed to a predetermined depth Id). During operation, the container (I) should be maintained at this approximately constant depth relative to the seabed ('5). This may be achieved by either the use of floats (a) and a cable (3) attached to the seabed or anchored (4) or the placement of the OWEC on a sub-sea platform. As a wave (9) passes the OWEC, seawater flows into the container as the height of water rises relative to the container (Figures 2 to 4). As the wave continues, seawater then exits the container (Figures 4 to 5 to 2). The depth (d) that the OWEC is placed could by determined by obtaining the maximum amount of flow through the pipes. The pipes may be valved as to allow water to flow through them in only one direction. In Figure 1 these valves are represented by (10) and indicate the direction of flow, however they are not totally necessary for some operation.

Much of the energy of waves can be converted to electrical energy in a number of ways. The inlet and outlets may be fitted with turbines, which can generate electricity.

In this case either mono or bi-directional turbines may be used. Another method of converting waves to electrical energy would be to arrange the valved inlets and outlets in such a way that when water enters and exits the OWEC it causes a torque about a central axis or coupling (a). Ides occurs if the inlets and outlets are arranged at an angle that is not perpendicular to the pressure exerted by the ocean on the OWEC.

The OWEC can then spin about its coupling. This subclass of OWEC can be known as a spinning OWEC or sOWEC. The inlets and outlets may be arranged so that the jetting or flow of water in and out rotates the OWEC unidirectionally. This spinning may then be converted into electrical energy using a generator. Examples of a possible arrangement of inlet and outlet pipes in a sOWEC are given in Figures 6 and 7. In Figure 6, water flowing into the container through the inlet pipes would cause the OWEC to experience a torque in a clockwise direction. In Figure 77 water Bowing out of the container through the outlet pipes would also cause the OWEC to experience a torque in a clockwise direction. The arrows denote these forces. These rotations could be used to generate electricity. Some of the variables that could be considered in increasing the conversion of wave energy to electrical energy include the shape (Figure 8), number, diameter, length and arrangement of the inlet and outlet pipes. The use of nozzles and the angle (a) in Figure I, (b) in Figure 6 and (c) in Fig,uTe 7 could affect conversion efficiencies. j

Claims

(:lalms I A wave energy converter including a container which IS partially

submerged In open sea and maintained at an approximately constant distance to the seabed so that, as an ocean wave passes the container, seawater enters and leaves the container through pipes In the container's sides.

A wave energy converter as claimed in claim I where seawater enters the container with a period approximately equal to half the wave period and seawater leaves the container with a period approximately equal to halfthe wave period.

3 A wave energy converter as claimed in claim I or claim 2 which is either buoyant and maintained at the required depth using an anchored cable or Is mounted on a suh sea platform.

4 A wave energy converter as claimed in any preceding claim where mono or bi directionai valves regulate the inflow and outflow of seawater.

A wave energy converter as claimed in any preceding claim where the inflow and/or outflow pipes are not parallel to the pressure ot' the seawater on the cylinder so that the flow of seawater through the inflow and/or outflow pipes causes the device to rotate about a central axis.

6 A wave energy converter as claimed in claim 5 where the rotation of the device is coupled to an electrical generator to produce electricity.

7 A wave energy converter as claimed in any preceding claim where the inflow or outflow pipes are tatted with turbines that: convert the kinetic energy of the seawater flowing through them into electrical energy.

8 A wave energy converter substantially as herein described above and illustrated In the accompanying drawings.

Amendments to the claims have been filed as follows Claims 1 A wave energy converter which m use is partially submerged in open sea and maintained at an approximately constant distance from the seabed, the converter comprising a container whose interior Is connected to its exterior via two sets of valved pipes, whereby in response to a rise in water leve] relative to the container due to the passing of a wave peak, water flows into the container through one set of valved pipes and is retained inside and in response to a further drop in water level relative to the container due to the passing of a wave trough, water leaves the container through the other set of valved pipes, the force of the water entering and leaving the container being used to cause the rotation of an axis or axes resulting in the generation of electricity.
2 A wave energy converter as claimed in claim 1 where the container comprises a substantially circular section cylinder with a single axis at the centre where the inlet pipes are arranged at an angle that is not para]]el to the force of the incoming water so that as water flows into the device a torque is created causing the device to rotate about the axis whilst the outlet pipes are arranged at an angle so that as water flows out of the container a torque is created as to reinforce the rotation in the same direction and about the same axis.
3 A wave energy converter as clawed in claim I or 2 where the inflow and outflow pipes are fitted with turbines that convert the energy of the seawater flowing through them into electrical energy.
4. A wave energy converter as claimed in any previous claim where the flow of water into and out of the container is regulated by valves.

A wave energy converter as claimed in any previous claim which is either buoyant and maintained at the required depth using an anchored retractable cable or is mounted on a sub-sea platform.

4 A wave energy converter as claimed in any previous claim which is either buoyant and maintained at the required depth using an anchored retractable cable or is mounted on a subsea platform.

Amendments to the claims have been filed as follows Claims 1 A wave energy converter which in use is partially submerged in open sea and maintained at an approximately constant distance from the seabed, the converter comprising a container whose interior is connected to its exterior via pipes, whereby in response to a rise in water level relative to the container due to the passing of a wave peak, water flows into the container through the pipes and is retained inside and in response to a further drop in water level relative to the container due to the passing of a wave trough, water leaves the container through the pipes, the force of the water entering and leaving the container being used to cause the rotation of an axis or axes resulting in the generation of electricity.

2 A wave energy converter as claimed in claim 1 where the container comprises a substantially circular section cylinder with a single axis at the centre and whose interior is connected to its exterior via two sets of pipes where the inlet pipes are arranged at an angle that is not parallel to the force of the incoming water so that as water flows into the device a torque is created causing the device to rotate about the axis whilst the outlet pipes are arranged at an angle so that as water flows out of the container a torque is created as to reinforce the rotation in the same direction and about the same axis.

3 A wave energy converter as claimed in claim 1 or 2 where the pipes are fitted with turbines that convert the energy of the seawater flowing through them into electrical energy.