GB2517018A

GB2517018A - Impulse generator

Info

Publication number: GB2517018A
Application number: GB1407502.2A
Authority: GB
Inventors: Francis Xavier Kay
Original assignee: FXK Patents Ltd
Current assignee: FXK Patents Ltd
Priority date: 2013-04-29
Filing date: 2014-04-29
Publication date: 2015-02-11
Also published as: GB2516806A; GB201307653D0; GB201407502D0

Abstract

An electrical generator comprises at least one piezoelectric block 20 and an actuator 3, 4 which is movable to provide a force to the piezoelectric block 20. The actuator may be a diaphragm 3a, with a thrust plate 4 for contacting the piezoelectric block 20. The block 20 may be mounted to a lower housing 5 which may be sealed to an upper housing comprising a parabolic reflector 7. There may be an aperture 8 in the upper housing, which allows water, e.g. from waves, to enter the upper housing and actuate the diaphragm 3a to apply force to the piezoelectric block 20. The diaphragm may be replaced by a piston.

Description

Impulse generator The present invention relates to an impulse generator and in particular a device for generating electricity using a piezoelectric material.

There is a need in the art for alternative methods of generating electricity, whether in a large-scale context (e.g. production of electricity for the UK National Grid, for eventual consumer use) or on a smaller scale, such as individual generators for single domestic or commercial applications. In particular there is a need in the art for environmentally-friendly methods of electricity production, often known as "alternative" or sustainable energy sources such as wind or hydro-electric power.

Hydro-electric power refers to the generation of electricity using the potential energy stored in flowing or falling water. One example of hydro-electrical power generation is the flow of water stored (at high potential energy) behind dams. The controlled flow of this water downhill can be used to drive turbines, which in turn generate electricity as known in the art.

Alternatively it is known in the art to provide electrical generators which harness the kinetic energy contained in moving water in tidal water or waves.

However previous attempts to harness energy from waves have been complicated mechanical devices. The present invention provides a far simpler method of harnessing wave energy than any known in the art.

The present invention provides a device capable of generating electricity from wave energy, for example in the sea.

Piezoelectricity is the electrical charge generated in certain solid materials when those materials are subjected to mechanical force or stress.

Deformation of the crystalline structure in piezoelectric materials leads to the generation of an electrical charge, and this charge can be harnessed by connecting the piezoelectric material to an electrical circuit.

For example, the piezoelectric material may be provided with a pair of silvered or metallised surfaces, for connection to a circuit. The ends of a bar of piezoelectric material may be silvered in this way.

As known in the art, piezoelectric materials include quartz and other natural-occurring materials together with man-made materials e.g. gallium orthophosphate crystals, ceramics such as lead zirconate-lead titanate ceramic, and polymers such as polyvinylidene fluoride.

In this specification, the term "piezoelectric generator" means an arrangement including a piezoelectric material which is capable of producing an electrical charge. A piezoelectric generator typically includes a piezoelectric material described above together with means to inflict a stress or force on the material, thereby generating an electrical charge. The means for inflicting a stress or force may be a mechanical means.

The present invention utilises the piezoelectric effect, to generate an electrical charge and thus produce a voltage due to the potential difference (PD) between the generated charge and an electrical circuit.

According to the invention, there is provided an electrical generator comprising at least one piezoelectric block and an actuator to provide force to the at least one piezoelectric block, wherein the actuator is moveable from a rest position to an actuated position, wherein in said actuated position the actuator provides said force to said block.

Preferably the actuator comprises at least one thrust plate, each of which having a surface which corresponds in size and shape to a surface of the block or blocks, for providing force to the block or blocks.

Conveniently the thrust plate is electrically insulated.

Advantageously the piezoelectric block is mounted on an insulated platform.

Preferably the generator comprises a base housing having an open top face which is in sealed engagement with the actuator.

Conveniently the actuator is at least partially surrounded by a parabolic reflector having at least one aperture provided therethrough.

Advantageously the parabolic reflector is connected at the periphery of the actuator.

Most preferably the actuator comprises or consists of, or is coupled to or with a diaphragm, the diaphragm being moveable from the rest position to the actuated position.

Conveniently the diaphragm is a convoluted diaphragm and preferably a single convoluted diaphragm.

Alternatively the actuator comprises a piston.

Conveniently the piezoelectric block comprises is a crystalline, ceramic or polymeric piezoelectric material.

Advantageously the generator comprises a plurality of piezoelectric blocks in an array.

The invention comprises, consists of or consists essentially of the above features. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 depicts a cross-section of a first generator according to the invention; Figure 2 depicts a cross-section of a second generator according to the invention; Figure 3 depicts schematic view of a test apparatus; and Figure 4 depicts a cross-section of a convoluted diaphragm for use with the present invention.

Figure 1 illustrates a first example of an electrical generator according to the invention. In this first example embodiment, the generator includes a relatively long strip or block of piezoelectric material 2. The material is mounted on an insulated platform 5 within a lower housing 6.

Above the piezoelectric material is mounted a single-convoluted diaphragm 3a. As known in the art, a convoluted diaphragm is a pad of material, which in this case is generally circular, having a peripheral region 3 which is inwardly dished. This permits the central region of the diaphragm Sa to move, in a direction up and down as depicted in Figures 1 and 2. The diaphragm may be moveable from a rest position (its normal conformation absent any external force acting upon it) to an actuated position, wherein the central portion is moved in an axial direction upon application of an axial force.

Figure 4 depicts it in more detail a convoluted diaphragm suitable for use in the present invention. The diaphragm is generally constructed of a material which is resiliently deformable, flexible or semi-flexible, and the diaphragm is mounted i.e. fixed around its periphery in the generator 1. In the accompanying drawings, the diaphragm is shown as being round in shape, but the invention is not to be considered limited to round diaphragms only.

Other shapes could be used e.g. square, rectangular or polygonal.

Furthermore, the invention is not limited to the single-convoluted diaphragm depicted with reference 3a in the diagrams. Rather, it is appreciated that the diaphragm could alternatively be a flat diaphragm, a dished diaphragm or a rolling diaphragm, as known in the art. However, a convoluted diaphragm, in particular a single convoluted diaphragm, has been found to be capable of transferring the largest proportion of kinetic energy to the thrust plate, i.e. gives the smallest energy loss.

Returning to Figure 1, it will be seem that the diaphragm 3a in combination with the lower housing 5 provides a closed or sealed chamber. In the context of the present invention it is to be appreciated that this chamber should be air-tight and waterproof. This is achieved by means of a peripheral sealing bead 3b (Figure 4) which encircles the diaphragm and interlocks between the lower housing 6 and an upper housing of the device 7, which may preferably be a parabolic reflector, as described further below.

On the underside of the diaphragm 3a, at depicted in Figure 1, there is provided a thrust plate 4. The thrust plate 4 is the material that is intended to come into contact with the piezoelectric material 2 and thereby generate an electrical impulse from the piezoelectric material as described above.

Accordingly, the thrust plate may be manufactured from a harder material than the diaphragm (which may be flexible or semi-flexible) in order to provide sufficient force to the piezoelectric material 2. For example, the thrust plate could be manufactured of a rigid plastics material, a metal or carbon-fibre, or a combination of the above, by way of example only. It is however to be appreciated that the thrust plate might be omitted, such that the diaphragm itself may make contact with the piezoelectric material. In this context, the diaphragm itself could have a force-providing central portion formed with the diaphragm.

The generator 1 is further provided with a parabolic reflector indicated by reference numeral 7. The parabolic reflector 7 provides an upper internal chamber which is parabolic in configuration. It is not important for the outside of the generator to have a parabolic shape. As will be described further below, the importance lies in the underside (internal region) of the parabolic reflector being parabolic in configuration. The use of the parabolic reflector results in the thrust of sea water on the diaphragm being evenly distributed over the whole surface of the diaphragm.

Furthermore the parabolic reflector is provided with an aperture 8 therethrough. This will be described further below with reference to operation of the generator of the invention.

Turning now to Figure 2, this figure depicts a similar arrangement to the embodiment of Figure 1 and like reference numerals have been used in Figure 2. However, in the Figure 2 embodiment, the generator is provided with a block of piezoelectric material 20 instead of a strip 2. As will be described further below with reference to the test data, the inventor of the present application has discovered that blocks of piezoelectric material are particularly useful in the generator of the invention. In one embodiment of the invention, the block could have a diameter of 6, 8 or 10 mm, with a length of 12 mm.

In the embodiments of Figures 1 and 2, the piezoelectric material is connected by wires to positive and negative electrical terminals designated by reference numeral 9. For example, the top and bottom faces of the block of the piezoelectric material may be coated in a metallic or other conductive material and this material in turn is connected to wires. The wires should exit through the lower housing 6 in a sealed (water and air tight) manner. These wires carry the charge produced by the piezoelectric material during operation of the invention.

It will also be seen from Figure 2 that the thrust plate 4 is dimensioned and configured to be of approximately equal size to the dimension of the piezoelectric block 20. This is contemplated by the present invention. Whilst Figure 2 depicts just one piezoelectric material 20 with a corresponding thrust plate 4, it is to be appreciated that the generator of the invention could include a number of blocks of piezoelectric material 20 together with a corresponding respective number of thrust plates or a smaller number of thrust plates 4, but wherein the combined service area of the thrust plates 4 is sufficient to correspond to the dimension of blocks 20. A number of blocks or 2 may be provided in an array of blocks.

In use, the embodiments of Figures 1 and 2 operate in a similar manner. As generally designated with reference numeral 10 in both diagrams, water is allowed to enter the top chamber of the generator defined by the parabolic reflector, via aperture 8. It is to be appreciated that the present invention is for use to harness wave energy. Accordingly, the generator may be placed in the sea, outside of or within the tidal zone, such that the water provided by a wave or current may enter the generator through aperture 8. The water entering the aperture has a kinetic energy. When the water hits the diaphragm 3a, it provides a force to the diaphragm thereby deflecting the diaphragm from its rest position to an actuated position. Accordingly, the diaphragm Sa moves downwardly as depicted such that the thrust plate 4 strikes the piezoelectric material 2 or 20 and thereby generates an electrical charge, which is carried by electrical connectors 9 to an external circuit, wherein the electrical power may be used.

Once the wave or flow or current of water has subsided and the pressure on the diaphragm Sa is released, the diaphragm 3a will revert to its rest position, before the cycle of actuation proceeds once more.

The parabolic reflector 7 is useful in the present invention as it can provide a power gain of the wave or current energy. As is known in the art, parabolic reflectors (for example for use in telecommunication devices) can concentrate beams of light forward in parallel rays. The same holds true for fluids (gases and liquids). Accordingly, in the present invention, the parabolic reflector concentrates the flow of water in a parallel fashion towards the diaphragm, thereby enhancing the power of the wave energy and minimising losses.

Accordingly, the present invention provides an apparatus which can harness the kinetic energy contained in waves, current or flows, for example in sea water, and convert it to electrical energy by way of a piezoelectric material, preferably a block of piezoelectric material.

The electrical power generated by the piezoelectric material may be drawn off and stored by way of a capacitor or battery or may be immediately used.

Further circuitry or components may be used in combination with the generator in order to realise the end use. For example, as the generator produces an alternating current (AC) then a rectifier could be added to produce direct current (DC). There now follows an explanation of the testing of the present invention which has been carried out by the inventor, with reference to Figure 3 which is a schematic of a test rig.

FigureS depicts a block of piezoelectric materials 20 which is connected to electrical terminals 9 in the same way as the generator depicted in Figures 1 and 2. Therefore is also provided a thrust plate 4. However, in the test rig of Figure 3, the thrust plate 4 is not connected to a diaphragm and exposed to wave impulses but is instead connected to a fluid power cylinder actuator 30 (e.g. a hydraulic or pneumatic actuator) which is connected to a fluid supply 31. This arrangement provides controlled force to the thrust plate 4, causing the thrust plate 4 to strike the piezoelectric material 20, generating an electrical charge in the same way as in the present invention but under test conditions. This test rig depicted in Figure 3 was developed in order to test various sizes and configurations of piezoelectric block materials.

It must be noted that the invention is not limited to the diaphragm embodiment depicted in Figures 1, 2 and 4. Whilst a diaphragm may be preferred, as a simple solution which also presents a circumferential edge that may be sealed to the lower housing to give a closed chamber, other actuators are envisaged. For example, the actuator can alternatively be a piston which, as known in the art, is a moving component in a cylinder. Thus, the generator could include a piston mounted within the housing, sealed at the periphery by piston rings, and movement of the piston from a rest to an actuated position provides force to the piezoelectric block.

Furthermore the actuator could comprise a sprung pad, i.e. a panel of material, which could be the thrust plate itself, mounted in the generator by means of a resiliently deformable material, including a spring or springs. The resiliently deformable material, spring or springs may be biased to the rest position but may be moveable to the actuated position as described above, by the action of waves.

Test data Power output of various blocks or energy, slugs of piezoelectric material has been tested as set out below. Testing was performed using blocks of piezoelectric material having dimensions 10mm by 10mm by 12mm length (i.e. diameter 10mm and length 12mm) and 6mm diameter by 12mm length and 8mm diameter by 12mm length. In other words, all three test materials had a 12mm length and the diameter was either 6mm, 8mm or 10mm. The piezoelectric material was obtained from Morgan Electro Ceramics, and was provided by the manufacturer pre-polarised (i.e. with defined positive and negative electrical terminals) in which the ends of the blocks are silvered i.e. coated with a metallic material for conductivity.

Table 1 below sets out below the power output measured when striking the piezoelectric blocks of different sizes with different amounts of thrust.

Readings were taken using a UNI-T UT58A multi meter.

Table 2 below sets out the measured voltage and current provided by various commercially available batteries, together with the charger outputs (manufacturer's claimed outputs) using the same test equipment.

Table 1

Block Air Thrust Voltage Current Block Block Stress size pressure (Ib) AC (mA) Surface volume pounds Diameter (bar) (9 Area (cubic per x length (square inches) cubic (mm) inches) inch 6 x 12 a 4 47 22 2.6 0.0438 0.01 72 2,733 b 7 81 32 2.4 0.0438 0.01 72 4,708 8 x 12 a 4 47 28 14 0.078 0.031 1,516 b 7 81 50 21 0.078 0.031 2,612 lOx 12 a 4 47 38 32 0.122 0.0575 817 b 7 81 60 42.5 0.122 0.0575 1,408.7

Table 2

Battery Type and Number. Volts Current ________________________ ___________ ___________ ___________ milliAmp 8mm diameter Button Cell __________ 1.3 __________ 0.lSma Pancake Battery: Sony 7487 0.18 0.15 ma Energizer 357/303 1.56 0.lS7ma Alkaline: AM Duracell Plus Power 1.58 6Oma AM Duracell Ultra Power 1.59 6Oma AA Duracell Ultra Power 1.63 200+ma Maplin Long Life 1.6 200+ma C Kodak XTRALIFE KC ___________ 1.57 ___________ 200+ma C Duracell Ultra 1.53 200+ma D Energizer ___________ 1.48 36ma Some Charger Outputs. (Claimed) :-Blackberry 5 550ma Stontronics ModeISAW-0501 200 5 l200ma BT Wireless Phone 6 SOOma Discussion The readings presented in Table 1 above show that a block of piezoelectric material having 6mm diameter can produce more than 30 volts under thrust from the thrust plate. As the thrust plate of the test rig depicted in Figure 3 was around 1 inch diameter, the thrust provided to the block was in the order of 47 pounds. Without wishing to be bound by theory, it is believed that halving the amount of thrust or pressure provided to the block would provide half the power output (i.e. half the measured voltage).

It is also believed that there is a straight-line relationship between voltage generated by the block according to variation in pressure applied. For example, if 47 lbs thrust from a 1 inch diameter piston produces around 30 volts, this leads to a figure of around 0.638 volts per pound thrust. Therefore, it should be possible to generate 240 volts from a thrust of approximately 376 pounds, which would require a piston of 2.8 inches diameter.

By further extrapolation, 480 volts would be producible from a piston of 4 inches diameter, giving 738 pounds thrust at 60 psi.

Alternatively, instead of increasing the size of the thrust plate or piston, the size of the block of material could be increased. If the present 6mm (0.157 inch) diameter block of material, having 0.0193 sq. inch area, gives 30 volts then to generate 480 volts, this should require a block of the order of 1.9 sq.

inches i.e. 1.5 inches in diameter.

Calculations show that the diaphragm diameter required to provide sufficient thrust for 440 volts output, at a nominal depth of 10 feet of sea water, would seem to be in the order of around 40 inches.

Such a large diaphragm could provide thrust onto an array of blocks of piezoelectric material rather than a single block.

Finally, it should be appreciated that the device of the invention is not limited to actuation by wave energy. Rather the movement of the actuator may be effected by any means providing kinetic energy, including but not limited to gas flow (including wind energy) and mechanical thrust, which may be provided, for example, by a moving part of a separate apparatus. For example the inventive generator could be coupled to a separate pump with a moving part, and the kinetic energy from the moving part used to actuate the generator. The invention therefore harvests wasted kinetic energy.

As can be seen from the above test data, even a relatively small block of piezoelectric material, in a generator of the invention, can produce a useful amount of charge, which is favourably comparable with the outputs of various batteries and chargers, measured under the same conditions. Accordingly the present invention provides a useful, environmentally friendly and simple arrangement for the production of electricity.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

Claims 1. An electrical generator comprising at least one piezoelectric block and an actuator to provide force to the at least one piezoelectric block, wherein the actuator is moveable from a rest position to an actuated position, wherein in said actuated position the actuator provides said force to said block.
2. A generator according to claim 1, wherein the actuator comprises at least one thrust plate, each of which having a surface which corresponds in size and shape to a surface of the block or blocks, for providing force to the block or blocks.
3. A generator according to claim 2, wherein the thrust plate is electrically insulated.
4. A generator according to any preceding claim, wherein the piezoelectric block is mounted on an insulated platform.
5. A generator according to any preceding claim, wherein the generator comprises a base housing having an open top face which is in sealed engagement with the actuator.
6. A generator according to any preceding claim, wherein the actuator is at least partially surrounded by a parabolic reflector having at least one aperture provided therethrough.
7. A generator according to claim 6, wherein the parabolic reflector is connected at the periphery of the actuator.
8. A generator according to any preceding wherein the actuator comprises or consists of, or is coupled to or with a diaphragm, the diaphragm being moveable from the rest position to the actuated position.
9. A generator according to claim 8, wherein the diaphragm is a convoluted diaphragm and preferably a single convoluted diaphragm.
10.A generator according to any of claims 1 to 7, wherein the actuator comprises a piston.
11.A generator according to any preceding claim wherein the piezoelectric block comprises is a crystalline, ceramic or polymeric piezoelectric material.
12.A generator according to any preceding claim, comprising a plurality of piezoelectric blocks in an array.
13.An apparatus substantially as herein described, with reference to Figures ito 4.
14.Any novel feature or combination of features described herein.