WO2009102210A1

WO2009102210A1 - Method for converting sea wave energy, power plant unit to implement this method, and a sea wave power plant

Info

Publication number: WO2009102210A1
Application number: PCT/NO2009/000035
Authority: WO
Inventors: Reidar Vaardal
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-02-01
Filing date: 2009-01-30
Publication date: 2009-08-20
Anticipated expiration: 2010-08-01
Also published as: CL2009001617A1; EP2240686A1; NO20080605L; NO328044B1; EP2240686A4

Abstract

Method for converting wave energy to an energy form which may be fed into an energy network, particularly an electric network. The waves are guided into a tubular channel (27) with an axially moveable piston (13) which is connected to a rotary converter (14, 16). This is connected to a converter (20 ) for generation of energy which may be transferred to an energy network, particularly electrical. A power plant unit for implementation of this method comprises a piston (13) which is suspended axially displaceable in a tubular channel (12) and whose piston rod (14) is connected to a rotary converter, e.g. by being integrated with or connected to a tubular part with inside threads, which is connected to a ball screw (16) which is connected to an outlet axle (17).

Description

Method for converting sea wave energy, power plant unit to implement this method, and a sea wave power plant

The invention relates to a method for conversion of sea wave energy as described in the first part of claim 1, a power plant unit to implement this method, as described in the first part of claim 4 and a sea wave power plant as described in the first part of claim 11.

Background For a long time attempts has been made to develop suitable sea wave power plants. In recent years a great number of proposed converting concepts have shown up, which in different ways will convert the wave energy in water waves to electrical or hydraulic energy, in the following denoted electrical energy. One can differ between point based and line based plants, over pouring plants and plants where a swinging water column powers a turbine.

The most common of the existing concepts relates to floating bodies placed in open sea and in one way or the other is connected together with hydraulic pumps or electrical generators which are driven when the floating bodies move up or down. This type of wave power plants requires a certain area in open sea. They therefore become vulnerable to strain from wind and weather, and at the same time they represent a hurdle for ship traffic. The energy conversion in such wave power plants is low, and it has not been possible to achieve a satisfying ratio between cost and performance.

It is also known to build platforms which carry floats for driving generators. The costs of such platforms has also given too low EROEI (Energy Return On Energy Investment). In addition such power plants will be exposed to damage in storms.

Coastal based wave power plants are also known, based on gathering of the water from the waves in reservoir above the sea level, and with water turbines which is driven by the gathered water. Neither have been suitable for practical use, mainly due to the high costs.

Purpose

The main purpose with the invention is to create a new concept for energy conversion, which may form the basis for a wave power plant that withstands all types of weather. In addition it must give satisfying energy production compared to investment and operational costs. It is also a purpose to create a sea wave power plant which does not leave practical or unsavoury hurdles in traffic areas in the sea, and which may be a hurdle for fishing and other activity at the sea.

In particular it is a purpose to create a modular sea wave power plant, which is joined by separate units which in an appropriate way may be joined to form energy power plants with varying size, adapted to geography and wave conditions in a certain sea area.

Further it is a purpose to create such a power plant which may be adapted to varying wave conditions and operational circumstances, included variations due to tide water.

It is also a purpose to create power plant units which may be manufactured rationally and cheaply on an industrial basis and which may be assembled to a power plant at suitable places and which may be maintained and possibly repaired in a simple way.

Finally it is a purpose to create a sea wave power plant which in a simple way may removed from the sea area or at least out of the area of influence for the sea waves in periods where the influence from the sea waves may cause damage, for example in a storm.

The invention

The invention is described in the claims. It primary relates to a method for conversion of sea wave energy to a form of energy which may be brought into en energy network, in particular electrical, where water waves is lead into contact with a moveable element which is connected to an energy converter, in particular an electrical generator. The sea waves are lead into a tubular channel with an axially moveable piston which is connected to a rotation converter connected to a converter for generation of transferable energy, in particular electrical.

The energy in the wave movement decreases when the sea waves approaches the sea shore, and come into shallow waters. Therefore it has not been regarded as possible to achieve economic energy conversion in this area. The invention makes this possible, mainly because the units may be built and operated in a simple and cheap way, and because costly protection measures against storm, which known sea wave power plants are depending on, is not required.

Details regarding this method are given in claim 2, where the rotation converter transfers the energy to a driving gear which is common for several axially moveable pistons in an arrangement with several similar power plant units, and that this driving gear drives an electrical generator or a pump.

According to claim 3 it is an advantage if the axially moveable piston and its surrounding tubular channel is controlled in the longitudinal direction and with regard to angle of inclination in relation to the wave front.

In order to implement the method according to the invention, a power plant unit as described in claim 4 may be used. This comprises a piston which is suspended axially moveable in a tubular channel, and which piston rod is connected to a rotational converter. The rotational converter may be a ball screw arranged as described in claim 5.

To give the power plant a suitable form, with regard to production, transport, mounting and eventually mounting together, it is practical to design it as described in claim 6, where it is suspended in a tubular channel, preferably with a quadratic cross section, with a transverse wall which delimits a front piston chamber, and that serves as a carrier for an axial bearing for the piston rod.

Further it is an advantage for the smoothing out of the wave strokes, if the power plant unit as described in claim 7, has an outlet axle which carries or is connected to a flywheel via a free wheel mechanism, which may be integrated with the flywheel.

The outlet axle may also be designed as described in claim 8, arranged to engage a gearwheel or a similar rotary part, which is common for more power plant units. The free wheel mechanism will then have to be integrated in the axle or its connection to the rotary part.

Further details regarding the power plant unit according to the invention are described in claim 9, where it is arranged to be axially moveably carried, preferably with remote control of the movement, at a sloping carrier in the waterside.

Further it may be possible to whip, preferably with remote control, about a transverse axle, to be able to adjust the front towards the incoming sea waves, as described in claim 10.

In order to build larger power plants it is practical if more power plant units according to one of the claims 4 to 10, are arranged in an assembly, with at least two units in the height and at least two units in the width. A favourable example is an arrangement of 3X3 power plant units which drives a common flywheel and a common generator. Such a battery like arrangement will facilitate the mounting and provide the possibility for a common control of several power plant units.

It is also possible to arrange several power plant units with the axis generally vertical, carried by a sea based structure, like a platform or quay structure.

Further details regarding the invention will appear from the following example description.

Example

Below the invention is more closely described with reference to the drawings, wherein

Fig. 1 shows a vertical cross view through one embodiment of a power plant unit according to the invention,

Fig. 2 shows a perspective view of a wave power plant according to the invention, composed by several power plant units as shown in Fig. 1,

Fig. 3 shows a schematic and sectioned perspective view of a further embodiment of the invention, with four piston units, the outlet axles engaging a common gear wheel, while Fig. 4 shows a schematic and sectioned sideview of still a further embodiment of the invention, with three piston units powering a common axle over a belt.

The power plant unit 11 in Fig. 1 is build with a tubular channel 12 with a quadratic cross view. The tubular channel 12 serves as housing for the equipment that collects the wave energy and converts it into electrical or another form of energy which may be feed into an energy network, for example hydraulic or heat energy in a fluid.

The electrical energy may be transmitted over land or in the water, in order to be feed into an existing power network or to be used in a local power network. Building of local power networks is particularly relevant at islands or in other areas, where public power networks do not exist. In such areas the power production may be based on a combination of wave power plants and one or more electrical power aggregates, tide water power plants and windmills. In some cases hydro electric power plants may also be a part of the power production facilities.

Each power plant unit 11 has a piston 13 placed in the tubular channel 12, the piston 13 is facing the open end of the channel 12, pointing towards the sea. The piston 13, which is adapted to the opening of the tubular channel 12, is carried by a tubular piston rod 14 which is displaceable suspended in a transverse wall 15 in the channel 12.

In an alternative embodiment the piston may be circular and suspended in a tubular channel. The piston rod 14 forms the external part of a ball screw 16, so that axial movement of the piston is converted to a rotary torque at the outlet axle end 17 of the ball screw 16. The axle end 17 carries a flywheel 18 with a free wheel mechanism 28, and, over a flange coupling 19 or similar, connected to an electrical generator 20. The electrical generator is placed at the inner end of the channel 12, which is closed with an end wall 21. Close to the ball screw 16, the end of the axle 17 is supported by a transverse wall 22 with a bearing.

The tubular channel 12 with its piston 13 and associated conversion equipment is in the example placed at a sea shore 23, which is sloping towards the water level 24. In the shown embodiment the sea shore 23 is provided with a sloping base 26, which may comprise rails, to form a track for a couple of wheels 25 at the same axle.

To ensure the return movement of the piston 13 after been pushed in, it may be arranged a screw spring surrounding the outgoing axle, the screw spring serves as a combined damper and as a return force. Instead of or in addition to this, it may be made openings in the piston which let an amount of water through, which at the end of the in stroke serves as a damper and which thereafter carries the piston down to the starting position before the next sea wave hits.

It may be appropriate to provide the sea shore with guiding structures that collect the sea waves towards the opening of the tubular channel 12.

The power plant unit 11 is connected to means for moving the power plant unit 11 in its longitudinal direction at the foundation 26 and further whip it around the axis formed by the wheels 25. For example electro mechanical mechanisms based on prior art technology may be used.

When a wave hits the sea shore 23 it will, when the tubular channel 12 is correctly adjusted, make a trust on the piston 13 and press it into the channel 12. The starting position of the piston 13 corresponds to what is shown in Fig. 1, slightly retracted into the channel 12, so that a piston chamber 27 is formed which may gather the impact energy from the sea wave and conduct it towards the piston 13. Power plant units as described may be produced in a factory and be transported to the plant area ready for mounting, as it will be given examples of in the following. The dimension of the tubular channel may for example be 0,5 - 2,0 meters in square or rectangular, for example 1,25 X 1,25 metres. The length of the front part of the piston chamber 27 may be 1 meter, the stroke of the piston 2 -3 metres and the length of the generator housing may be 2 metres.

Such a power plant unit may be provided with mechanical and electrical dimensions, so that it may be used to supply power to small networks, an individual user and as power supply for equipment arranged isolated in or by the sea.

In Fig. 2 a power plant is shown, with power plant units according to the invention. In the example there is shown several power plant units 11 that are built together in a row, for placement along a sea shore, with two power plant units in the height. In Fig. 2 it is shown a section of four such pairs of power plant units placed side by side, but this number may be adapted to a sea shore, with an arbitrary length. Such an assembly may be called a power plant battery, and several such power plant batteries may be placed in a row, being controlled from a common centre, for feeding of a common network.

In an alternative embodiment, the individual outgoing axles 17 from several power plant units are mechanically coupled together, for common driving of an electrical generator. For example four axle ends 17 may, via a free wheel mechanism, be engaged with a common flywheel, which again drives a common electrical generator.

In particular, an actual embodiment is 3 X 3 power plant units put together in a power plant battery, with a common generator and a common flywheel.

Figure 3 shows a battery 29 comprising four piston units 30, 31, 32, 33, which are arranged in two layers corresponding to the embodiment of Figure 2. The number of units stacked may be larger, but it is assumed that this is a favourable number. The number of units assembled sideways may be adapted to the available space and optimal drive shaft length.

Each piston unit 30 - 33 has a piston 34, a piston rod 35, a transverse wall 36 and a ball screw 37 engaging the piston rod. At the free end of each ball screw 37 a gear wheel 38 is arranged to engage a centrally arranged gear wheel 39. This gear wheel is suitably joumalled at the joint of the four piston units 30 - 33 at the end thereof. The gear wheel 39 is integrated with a pulley 40 driving a generator 42 over a belt 41. The gear wheel 39 may also function as a flywheel.

The battery 29 of piston units may be carried correspondingly to the embodiment of Figure 1.

Figure 4 shows a battery 43 of three piston units 44, 45, 46, each with a piston 47 which may be moved in a channel. Each piston has a bracket 48 extending through a longitudinal slot 49 at the bottom of each channel.

Under each piston unit a runner wheel 50, 51 with a horizontal axis is arranged at each end, to carry a belt 52 the upper side 53 of which is arranged under the slot 49. The bracket 48 is connected to the upper side 53 to power the belt 52.

The pulleys 50 at the sea facing end is journalled by brackets 54 connected to a not shown base. The pulleys 51 at the back end of the piston unit battery is connected to corresponding brackets 55 and carried by a common drive shaft 56 extending to a generator 57 at one end. The generator 57 and the drive shaft 56 is connected over a free wheel 58 allowing the pistons 47 to return from an inner end position to a front end position. The drive shaft 56 carries a flywheel 61.

In Figure 4, a box shaped piston 47 is shown, with side walls 59 to guide in the channel and with bracing elements 60.

The power plant according to the invention is primarily provided for instalment in a natural waterside or shore. But it is also possible to place it at moles, by quays, by platforms at sea and on specially built carrying structures which may be anchored at pillars at the sea bottom.

The invention is associated with generation of electrical energy. It may however be areas of use, where the rotary energy is transferred to a pump or a compressor which feeds pressure media into a network where this may be used for driving motors. This may for example be of interest when using the invention close to platforms at sea.

It is also possible to let the rotary energy heat a liquid for circulation in a network, but in most cases this will be a less valuable form of energy, with poor transmission qualities. The positioning of such a power plant or an individual power plant unit may be controlled with one controlling circuit which receives signals from wave measuring equipment, power meter, and impact measuring equipment. The main purpose of such a controlling circuit, for example a PLS system, will be to provide an optimal position, including height and oblique position, to maximize the power outlet. In addition it will comprise controlling functions for parking such a plant in inactive and secured position under storm and/or other strains which are causing a risk for damage, for example high water.

In some cases it may be appropriate to design a "garage" in a safe distance from the sea, for parking the plant where it is not exposed for waves. The power plant could then have guiding rails at the sides for controlling the position when driving in or out.

Claims

1. Method for converting sea wave energy to an energy form which may be fed into an energy network, where the sea waves are guided into contact with a moveable element which is connected to an energy converter, characterized in that the waves are guided into an tubular channel (27) with an axially moveable piston (13) which is connected to a rotary converter (14,16) connected to a converter (20) for generation of energy which may be transferred to an energy network, in particular electrical or hydraulic.

2. Method according to claim 1, characterized in that the rotary converter (14, 16) transfer its energy to a driving wheel which is common for multiple axially moveable pistons in one arrangement, and that this driving wheel drives an electrical generator (20) or a pump.

3. Method according to claim 1 or claim 2, characterized in that the longitudinal position of the axially moveable piston (13) and its surrounding tubular channel (27) are controlled as is the angle of tilt in relation to the wave front.

4. Power plant unit for implementation of the method according to claim 1, characterized in that it comprises a piston (13) which is suspended axially displaceable in a tubular channel (12) and whose piston rod (14) is connected to a rotary converter (14,16).

5. Power plant unit according to claim 4, characterized in that the piston rod (14) is integrated with or connected to a tubular part with inside threads, which is connected to a ball screw (16) which forms or is connected to an outlet axle (17).

6. Power plant unit according to claim 4 or claim 5, characterized in that the tubular channel (12) preferably has a quadratic cross section, with one transverse wall (15) which delimits a front piston chamber (27) and which serves as a carrier for an axial bearing for the piston rod (14).

7. Power plant unit according to one of the claims 4 to 6, characterized in that the outgoing axle carries or is connected to a flywheel (18) over a free wheel mechanism (28).

8. Power plant unit according to one of the claims 4 to 7, characterized in that the outgoing axle (17) is adapted to engage a gear, or similar rotary part, which is common to multiple power plant units.

9. Power plant unit according to one of the claims 4 to 8, characterized in that it is provided to be axially displaceable, preferably with remote control of the movement, at a sloping base (26) at a seashore (23).

10. Power plant unit according to claim 9, characterized in that it is possible to whip, preferably with remote control, about a traversing axis, in order to adjust the front against the incoming waves.

11. Wave power plant, for generation of wave energy, characterized by comprising multiple power plant units according to one of the claims 4 to 10, where it is arranged a close setting up with at least two units in the height and at least two units in the width.

12. Wave power plant according to claim 11, characterized in that two or more power plant units (11) have a common driving connection with a common generator or pump.

13. Wave power plant according to claim 11, characterized in that the power plant units are arranged with the axis generally vertical, carried by a sea based structure, like a platform or quay structures.

14. Wave power plant according to claim 12, characterized in that four piston units (30 - 33) are engaging a common gear wheel (39) powering an electric generator.

15. Wave power plant with a power unit for conducting the method according to claim 1, characterized in that it comprises at least one piston (44 - 46) which is received in a tubular channel to be reciprocally operated, and that the piston is connected to an element (48) extending through a slot (49) in the tubular channel and is connected to a longitudinal belt (52) making a loop over a pair of pulleys (50, 51), one of which being connected to an electric generator (57) over a shaft (56) being common to multiple piston units.