WO2007084013A1

WO2007084013A1 - Electricity generator

Info

Publication number: WO2007084013A1
Application number: PCT/NZ2007/000011
Authority: WO
Inventors: Lindsay Tadman
Original assignee: Lindsay Tadman
Priority date: 2006-01-19
Filing date: 2007-01-18
Publication date: 2007-07-26
Also published as: NZ544812A

Abstract

An electricity generating system for the production of electric power including: a floating body, an electric generator mechanically connected to the floating body, a mechanical movement transmitting means, characterised in that, the generator has an inflexible shaft mechanism that minimises lateral movement of the floating body when the mechanical movement transmitting means converts movements of the floating body to kinetic movements of the generator rotor, and a central drive shaft with a pulley system that enables multiple floating bodies to be attached to the drive shaft in operation with the electric generator.

Description

ELECTRICITY GENERATOR

TECHNICAL FIELD

The present invention relates to improvements in an electricity generator.

Particularly, although not exclusively, the present invention relates to an apparatus and method for producing electrical energy by use of wave motion.

BACKGROUND ART

It is well known that the sea always has waves caused by a meteorological action. The wave movement in the sea and lakes constitutes a potential source of energy.

The waves vary in size because of the height, length, cycle and speed of the waves which in turn affects the available wave energy.

There are calculations which can determine the amount of wave energy that can be converted into electrical energy produced by the upward travel of a buoy.

For example, the amount of power required to turn a 25OkW generator is approximately 345kW. Allowing for power depletion through mechanical application, calculations are based on producing 50OkW of power at initial drive. Therefore, in order to produce 50OkW from a wave with a one metre lift at a frequency of six waves per minute requires a buoy with a diameter of 12.5 metres (assuming displacement of water using the lower half of the sphere of the buoy).

Accordingly, various proposals and attempts have been made to utilise the energy available from the wave movement in the sea or a lake for generating electric power.

However, these have been unsuccessful in competing with conventional production of electric power. A number of wave electricity generators have been primarily experimental plants or have been used to supply power locally for navigation buoys.

A light buoy is disclosed in US 5,176,552 where it is supplied with energy from the movement of the buoy in the waves. A rotating electric generator is arranged inside the light buoy. The rotor of the generator is connected by a cable with a stationary plate located down in the water. When the buoy is moved up and down by the waves, the cable causes the rotor to rotate. However, this device is not very suitable for producing electric power to supply an electric supply network.

Some other known devices for generating electric power from wave energy are based on principles according to which water is pumped or air compressed in order to drive a generator turbine. There are several components and links involved in the energy conversion process, which affects the total efficiency. Such units are also complicated, and therefore expensive.

It is also already known to use electric generators which are directly connected to a floating body. This avoids many of the drawbacks mentioned above.

WO 03/058054 A1 relates to a wave-power unit and plant for the production of electric power and a method of generating electric power. A wave-power unit has a floating body and a rotating electric generator mechanically connected to a floating body. In accordance with this invention a mechanical movement transmitting means is arranged for transmission of vertical movements of the floating body to rotary movements of the generator rotor.

The corresponding New Zealand Patent Application No. 534543 discloses the use of a linear electric generator in place of the rotary electric generator.

However, there are disadvantages with the above two embodiments of WO 03/058054 A1 and NZ 534543. The floating body is connected to the electric generator by an unsupported cable, wire or chain. A considerable amount of energy is lost as lateral movement of the floating body is possible during wave motion reducing vertical transmission movement.

Also, a further disadvantage of this invention is that it requires a number of wave- power units to be connected together to generate enough power from a wave-power plant.

US 5,066,867 relates to a method and device for generating electric power by use of wave force. Power is obtained by using flotation bladders rising and falling repeatedly with waves as a power source and the rotation force of gears connected to the flotation bladders through ropes.

One embodiment of this invention includes two ropes in an attempt to restrain the flotation bladder from moving transversely with the waves. However, the disadvantages of this configuration is that the floatation bladder is still able to pivot around the axis of the ropes and move laterally with the wave motion.

Therefore, the flotation bladder is not always perpendicular to the advancing direction of waves decreasing the efficiency when converting the kinetic energy of the waves into electrical energy.

Another embodiment of this invention includes a horizontal solid lever system to minimise lateral movement. There is greater water resistance associated with movement of the horizontal lever which in turn imparts more stress on the lever compared to a fully vertical shaft.

There are further disadvantages with this invention. The majority of the vital components are exposed to the elements with no enclosed structure. Also, the base frame is not installed on the seabed, but in a fixed depth under the mean sea leve! connected to and supported by an anchor fixed on the seabed through a rope. This makes the apparatus susceptible to ocean currents and a potential for the apparatus to break free from the anchor and be swept away.

US 4,241 ,574 relates to an apparatus for producing electrical energy from multi , directional water wave motion including a central support for placement on the bottom of the body of water with the support extending vertically above the surface of the water. A multiplicity of shafts extend radically and horizontally from the central support with a multiplicity of floats supplied for each shaft.

The disadvantages of this invention is that the floats are connected solely by a cable. There is a significant amount of lateral movement associated with the cable and buoy assembly. This translates to reduced lateral movement and loss of kinetic energy that can be converted to electrical energy.

DE 3116740 A1 is an invention that employs a hollow body held by means of cables fixed to an underwater support or underwater plant, in such a way that it can move freely with the waves of the sea and transform the movements into rotary motion by means of traction cables leading to underwater generating sets to produce power.¹

There are a number of disadvantages associated with this system. Firstly, a hollow . body has to be constructed of considerable dimensions (for example, the size of a football pitch) to enable a number of generator sets to be connected to the hollow body for the required power output. Secondly, a number of wire cables have to be attached to the hollow body and an underwater support. The use of only wire cables gives a large potential for lateral movement corresponding to inefficient conversion of kinetic energy of the waves into electrical energy.

DE 3320755 A1 discloses a wave power plant with a floating body moving with the waves. Generating sets for generating power are constructed within the floating body attached to bollards under the water and is moved up and down by the waves like a see-saw. The floating body is held by wire cables to the bollards with a large potential for lateral movement.

This undesirable lateral movement is addressed in an invention disclosed in FR 2521646. The invention enables the use of energy from sea waves where the movement of a float is forced to move only in a vertical direction, by means of guides attached onto a metal frame supporting the assembly.

This is a complex system requiring a supporting frame work of metal girdlers and guides or a rack system. However, there is a lot of friction associated with the guides as the float moves vertically with the wave motion. This leads to a loss of kinetic energy and therefore electric power. A further disadvantage that occurs with a metal guide system is metal oxidation with salt water, where the float may become stuck in the guide system when travelling up and down the guide system.

It is an object of the present invention to provide a wave electricity generator which addresses the problems highlighted herein with the prior art methods or at the very least provide the public and the trade with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided an electricity generating system for the production of electric power including:

a floating body,

an electric generator mechanically connected to the floating body,

a mechanical movement transmitting means,

characterised in that,

the generator has an inflexible shaft mechanism that minimises lateral movement of the floating body when the mechanical movement transmitting means converts vertical movements of the floating body to kinetic movements of the generator rotor,

and a central drive shaft with a pulley system that enables multiple floating bodies to be attached to the drive shaft in operation with the electric generator.

In preferred embodiments of the present invention the floating body will be a buoy.

However, this should not be seen as a limitation on the current invention. Other embodiments for the floating body may include any distinctively shaped float constructed from plastic, fibreglass, rubber, metal, composite material or any other such material.

In preferred embodiments of the present invention a mechanical movement transmitting means is configured for use with a rotating electric generator.

The advantage of a rotating electric generator is that the wave movements are directly transmitted to the rotary movements of a rotating electric generator.

In preferred embodiments the rotating electric generator includes a magnetic rotor with a rotary body that rotates around an axis.

In another embodiment the rotating electric generator includes a stator, windings on the stator and/or rotor and a plurality of poles.

However, this should not be seen as a limitation of the present invention for any standard type of electric generator could conceivably be used with the invention. Other embodiments envisaged may include a linear electric generator.

In preferred embodiments the generator may include a stator enclosed in a housing anchored in the sea/lake bed.

Enclosing the generator or only its stator in a watertight housing means that it is protected from attack by the surrounding salt water or the influence of living organisms in the water such as barnacles. Also, anchoring the generator in the sea bed via the housing fixes the position of the generator in relation to the floating body and enables optimal utilisation of the vertical movement of the floating body.

In another preferred embodiment of the present invention there may be a waterproof housing which contains all the electrical equipment of the system Therefore, the entire generator is protected from corrosion.

In accordance with another preferred embodiment the housing is secured to a base plate secured to rest on the bed of the sea/lake.

Since the housing is applied on the bed to the generator then all subsequent componentry will be stablised substantially unaffected by underwater currents. The base plate may have a relatively large mass which also increases stability.

In preferred embodiments the housing will be filled with an inert gas.

This can be particularly significant if the generator and its components are placed in relatively deep water. Since the pressure difference would otherwise make it difficult to efficiently seal the housing. The inert gas should have the same pressure as the surroundings and provide a workable environment for persons to enter the structure for maintenance purposes.

However, this should not be seen as a limitation of the present invention as the housing may be filled with liquid to equalise the pressure with the surroundings.

This can be particularly significant if the generator and its components are placed in relatively deep water. Since the pressure difference would otherwise make it difficult to efficiently seal the housing. The liquid should have the same pressure as the surroundings.

In yet another preferred embodiment the housing may be constructed out of metal, concrete, composite material, or any other such material.

Concrete is the most economical material and is corrosion resistant. Also, it is important for the invention to have a high ballast weight and the material costs are then of considerable significance.

In preferred embodiments, at least part of the mechanical connection means is flexible. This may include a cable, wire, rope or chain. The advantages of this embodiment is that this avoids the laterally directed wave forces on the floating body being transmitted with full force to the rotor of the generator.

The cable, wire, rope or chain may extend all the way from the floating body to the rotor or it may constitute a part of the connection means. Alternatively, flexibility can be achieved by the connection means being rigid, but provided with universal joints.

In a further embodiment the mechanical movement transmission means is secured by its upper end to the floating body and by its lower end to a bottom pulley so that at least a cable can pass through the lower part of the movement transmission means.

The mechanical movement transmission means comprises a cable running to a drive spool with initial drive gear attached, turning another gear and shaft to a fly wheel which drives the generator rotor.

In preferred embodiments the drive spool includes a one-way bearing assembly on its shaft. This is adapted to allow upward motion of the buoy to produce drive. As the buoy is moving down the back of a wave, no drive is applied.

In preferred embodiments on the same shaft as the drive spool is a counter-weight spool which has cable running through a pulley assembly attaching to a counterweight.

The advantages of the counter-weight system is that it maintains constant tension on the cable between the shaft and the drive spool.

In preferred embodiments of the present invention there is a transmission configured to deliver the optimum revolutions per minute for the generator that is attached.

In preferred embodiments there is a clutch assembly between the fly wheel and the transmission. The clutch assembly may include a generator assembly which is used to disconnect the drive from the fly wheel at a predetermined (high and low) shaft speed.

The advantages of this assembly is to ensure the optimum revolution range is not exceeded.

In preferred embodiments all critical components are monitored with electric sensors such that the related information is transmitted by radio to a receiver/sender unit within the buoy.

However, this should not be seen as a limitation on the embodiments for envisioned for this invention. Other embodiments envisioned for the receiving and sending of information may include a number of devices such as global positioning systems (GPS) and other such electronic information systems.

In preferred embodiments of the present invention there is a solid shaft mechanism.

This minimises the lateral movement of the floating body where the movement of the float is forced to move only in vertical direction, by means of a hollow, but solidly constructed shaft through which a cable passes through attached to the floating body.

The advantages of this mechanism is that it translates to reduced lateral movement and less waste of kinetic energy that can otherwise be converted to electrical energy.

A further advantage of a solid shaft is the floating body is unable to pivot around the axis and move laterally with the wave motion compared to a rope system as disclosed in US 5,066,867.

In preferred embodiments the solid shaft mechanism is vertical.

The advantages of a vertical shaft mechanism compared to a horizontal lever system as disclosed in US 5,066,867 is that there is a greater water resistance associated with movement of a horizontal lever. This in turn imparts more stress on the lever compared to a fully vertical shaft mechanism.

In further embodiments of the length of the solid shaft mechanism is adjustable.

This allows, for instance, for adjustment to different levels of the surface of the sea/lake as in the case of tidal waters.

In preferred embodiments there is a central drive shaft for the pulley system.

The advantages of this system is that it enables multiple floating bodies to be attached to one drive shaft. As and when required, multiple buoys can be installed, enabling the same wave to be used to drive a generator unit thereby producing a greater and continuous power output.

In one embodiment the wave electricity generator may include a plurality of generators.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 : shows a diagrammatic representation of the side profile of one preferred embodiment of the present invention; and

Figure 2: shows a diagrammatic representation of an exploded top view of the drive spool and its components;

Figure 3: shows a diagrammatic representation of the end profile of one preferred embodiment of the present invention. Figure 4: shows a diagrammatic representation of a top view of one of the preferred embodiments of the present invention with multiple buoy application.

BEST MODES FOR CARRYING OUT THE INVENTION

With reference to figures 1 , 2, 3 and 4, there is provided a wave electricity generator.

The invention utilises a flotation buoy which is tethered to a submerged generator assembly. The vertical rise and fall of the buoy occurring with each wave is translated into rotational kinetic energy to power a generator.

Figure 1 shows the present invention in which the buoy (1) is attached to a submerged solid shaft mechanism (3) contained within a tower assembly (2) which is secured to the ocean floor.

A cable from the shaft (3) with a bottom pulley (4) will run to a drive spool (5) which has a one-way bearing assembly on its shaft (6), allowing for the upward motion of the buoy to produce drive. As the buoy is moved down the back of the wave, no drive is applied.

On the same shaft as the drive spool (5) is a counter-weight spool (7) which has a cable running through a pulley assembly (8) attaching to a counter-weight (9). The counter-weight (9) maintains a constant and even tension on the cable between shaft (3) and drive spool (5).

Figure 2 shows an exploded top view of the drive spool (5) with the one-way bearing assembly (6), counter-weight spool (7) spool shaft (10) and spool shaft bearing (11).

Figure 3 shows the shaft from the drive spool (5) which has the initial drive gear (12) attached, and turning another gear and shaft to the fly wheel (13). The fly wheel is used to maintain the rotational momentum through the rest of the drive system. Between the fly wheel (13) and the transmission (15) is a clutch assembly (14) which also contains a governor assembly. These are used to disconnect drive from the fly wheel (13) at a predetermined shaft speed so as to ensure the optimum revolution range is not exceeded. Transmission (15) is configured to deliver the optimum revolutions per minute for the generator that is attached.

The generator assembly enclosure (16) is a sealed area contained within a totally waterproof housing (17). All electrical equipment is isolated and maintained within this housing.

Figure 4 shows a top view of one of the preferred embodiments of the invention with multiple buoy application. There is a central shaft (18) with pulley system (4, 8) so multiple floatation buoys attached to the bottom pulleys (4) may be utilised with a single generator unit (16) and driven from a central shaft (18).

The floatation buoys can be optimally positioned in series (i.e. perpendicular to the wave-front) to provide successive kinetic energy inputs from the passing wave. Alternatively, the multiple buoys attached to a single generator may be positioned parallel to the wave-front to receive a simultaneous input from each buoy.

The electric generator(s) (16) are rotary AC or DC types which are commercially available. The commercially available generators have rotary motion, a rotor that is either permanently magnetic or non-permanently magnetic with a rotary body that rotates around an axis, a stator, winding on the stator and/or rotor and a plurality of poles.

Each unit has a generator(s) (16) fitted that suit the location of where the unit is intended to be installed.

All critical components are monitored with electrical sensors. This and relevant information is transmitted by radio to a receiver/sender unit within the buoy (1). This is then transmitted by radio to land based monitoring facilities.

The entire unit is secured to the seabed, and has entry points for maintenance and service. Entry point is by way of a moon type access in the lowest point of the structure (similar to a diving bell).

The housing (17) is air and water tight and pressurised to maintain an equilibrium between the atmosphere inside and water outside.

The entire housing is double skinned so as to minimise possible impact damage from the outside. A generator and electronics are enclosed in a fully sealable inner room(s) using hatches or access ways similar to those used on commercially available marine and submarine applications.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope of the appended claims.

Claims

WHAT WE CLAIIVUS:

1. An electricity generating system for the production of electric power including:

a floating body,

an electric generator mechanically connected to the floating body,

a mechanical movement transmitting means,

characterised in that,

2. An electricity generating system as claimed in claim 1 , wherein the floating body is a buoy.

3. An electricity generating system as claimed in claim 1 or claim 2 wherein the electric generator is rotating.

4. An electricity generating system as claimed in any one of claims 1 to 3, wherein the electric generator includes a magnetic rotor.

5. An electricity generating system as claimed in any one of claims 1 to 4, where the generator includes a stator enclosed in a housing anchored in the sea/lake bed.

6. An electricity generating system as claimed in any one of claims 1 to 5, which includes a waterproof housing which contains all the electrical equipment of the system.

7. An electricity generating system as claimed in claim 6, wherein the housing is secured to a base plate which is capable of being secured to rest on the bed of the sea/lake.

8. An electricity generating system as claimed in claim 6 or claim 7, wherein the housing is filled with an inert gas or liquid.

9. An electricity generating system as claimed in any one of claims 1 to 8, wherein at least part of the mechanical connection means is flexible.

10. An electricity generating system as claimed in any one of claims 1 to 9, wherein the mechanical movement transmission means is secured by its upper end to the floating body and by its lower end to a bottom pulley so that at least a cable can pass through the lower part of the movement transmission means.

11. An electricity generating system as claimed in claim 10, wherein the mechanical movement transmission means includes a drive spoo! shaft with a one-way bearing assembly.

12. An electricity generating system as claimed in any one of claims 1 to 11 , wherein there is a counter-weight spool attached to the drive spool shaft.

13. An electricity generating system as claimed in any one of claims 1 to 12 which includes a clutch assembly positioned between a fly wheel and the mechanical movement transmission means.

14. An electricity generating system as claimed in claim 13, wherein the clutch assembly includes a generator assembly to disconnect the drive from the fly wheel at a predetermined shaft speed.

15. An electricity generating system as claimed in any one of claims 1 to 14, wherein all critical components are monitored with electric sensors such that the related information is transmitted by radio to a receiver/sender unit within the buoy.

16. An electricity generating system as claimed in any one of claims 1 to 15, wherein the length of the solid shaft mechanism is adjustable.

17. An electricity generating system as claimed in any one of claims 1 to 16, wherein the wave electricity generator includes a plurality of generators.

18. A method of operating an electricity generating system for the production of electric power that has:

a floating body connected to an electric generator with an inflexible shaft mechanism minimising lateral movement of the floating body,

a central drive shaft with a pulley system enabling multiple floating bodies to be attached to the drive shaft in operation with the electric generator, and

a mechanical movement transmitting means,

characterised by the step of,

the mechanical movement transmitting means converting vertical movements of the floating body to kinetic movements of the generator rotor.

19. A method of operating an electricity generating system as claimed in claim 18, wherein the floating body is a buoy.

20. A method of operating an electricity generating system as claimed in claim 18 or claim 19, wherein the electric generator is rotating.

21. A method of operating an electricity generating system as claimed in claims 18 to 20, wherein the electric generator includes a magnetic rotor.

22. A method of operating an electricity generating system as claimed in any one of claims 18 to 21 , wherein the electric generator is enclosed in a housing anchored in the sea/lake bed.

23. A method of operating an electricity generating system as claimed in any one of claims 18 to 22, which includes a waterproof housing which contains all the electrical equipment of the system.

24. A method of operating an electricity generating system as claimed in claim 23, wherein the housing is secured to a base plate which is capable of being secured to rest on the bed of the sea/lake.

25. A method of operating an electricity generating system as claimed in claim 23 or claim 24, wherein the housing is filled with an inert gas or liquid.

26. A method of operating an electricity generator as claimed in any one of claims 18 to 25, wherein at least part of the mechanical connection means is flexible.

27. A method of operating an electricity generating system as claimed in any one of claims 18 to 26, wherein the mechanical movement transmission means is secured by its upper end to the floating body and by its lower end to a bottom pulley so that at least a cable can pass through the lower part of the movement transmission means.

28. A method of operating an electricity generating system as claimed in claim 27, wherein the mechanical movement transmission means includes a drive spool shaft with a one-way bearing assembly.

29. A method of operating an electricity generating system as claimed in any one of claims 18 to 28, wherein there is a counter-weight spool attached to the drive spool shaft.

30. A method of operating an electricity generating system as claimed in any one of claims 18 to 29 which includes a clutch assembly positioned between a fly wheel and the mechanical movement transmission means.

31. A method of operating an electricity generator as claimed in claim 30, wherein the clutch assembly includes a generator assembly to disconnect the drive from the fly wheel at a predetermined shaft speed.

32. A method of operating an electricity generating system as claimed in any one of claims 18 to 31 , wherein all critical components are monitored with electric sensors such that the related information is transmitted by radio to a receiver/sender unit within the buoy.

33. A method of operating an electricity generating system as claimed in any one of claims 18 to 32 wherein the length of the solid shaft mechanism is adjustable.

34. A method of operating an electricity generator as claimed in any one of claims 18 to 33, wherein the wave electricity generator may include a plurality of generators.

35. An electricity generator for the production of electric power substantially as herein described with reference to and as illustrated by the accompanying drawings.

36. A method of operating an electricity generator for the production of electric power substantially as herein described with reference to and as illustrated by the accompanying drawings.