GB2522455A

GB2522455A - An electrostatic generator with active flow control

Info

Publication number: GB2522455A
Application number: GB1401243.9A
Authority: GB
Inventors: Justin Rorke Buckland; Michael John Brockley; Charles Robert Sims; Matthew John Sims; Stephen Charles Sims
Original assignee: ZICONIX Ltd
Current assignee: ZICONIX Ltd
Priority date: 2014-01-24
Filing date: 2014-01-24
Publication date: 2015-07-29
Also published as: WO2015110838A1; EP3097637A1; GB201401243D0

Abstract

An electrostatic generator for generating a potential difference comprises two conducting elements 204a,b with opposite polarities connected to conducting receptacles 205a,b and active flow controllers 202a,b for controlling fluid flow past the conducting elements 204a,b such that the resulting electrostatic interaction causes a charge separation between the receptacles 205a,b and generates a potential difference. Each flow controller 202a,b may comprise a membrane with at least one aperture and an actuator for vibrating the membrane. Fluid flow may be controlled such that droplets are formed at an optimum point in the electric field near the inducers 204a,b for inducing charged particles therein. Part of the output of the generator may be fed back to the flow controllers 202a,b and may also power a control device comprising a signal generator 206 and sensors for controlling said actuators of the flow controllers 202a,b to produce a greater number of droplets. The Kelvin generator may comprise a single reservoir 201 or two reservoirs in fluid contact with the flow controllers 202a,b.

Description

An Electrostatic Generator with Active flow Control

Field of the invention

The present invention relates to electrostatic generators, more particularly, the present invention concerns improvements to the efficiency of electrostatic generators of the Kelvin water dropper or water dropping condenser type.

Background

Lord Kelvin discovered his water-dropping condenser (Kelvin generator) in 1867.

Figure 1 is a drawing of a simple Kelvin generator. The generator of Figure 1 comprises a reservoir 1; two nozzles 2a and 2b; two receptacles 3a and 3b, one disposed beneath each nozzle, the receptacles 3a and 3b being insulated from each other and the ground; two inducers (or conductors) 4b and 4a, one connected to each receptacle via conducting connection means 5a and 5b with each inducer positioned above the receptacle to which it is not connected; and finally two streams of water 6a and 6b.

As a result of the natural self-ionisation reaction which occurs in water, it is made up of positively charged hydronium ions and negatively charged hydroxide ions.

It is the act of separating these ions which produces an electrostatic charge during the operation of a Kelvin generator as will be described in detail below.

Lord Kelvin used water in his experiments, but theoretically any polar liquid could be used. Accordingly, it should be assumed that, throughout the description, where water is described as the operative fluid, any other suitable alternative solvent, fluid or solution is envisaged. Acetic Acid, Dimethyl Sulfoxide, Methanol are but a few examples. The skilled person would understand that any polar solvent (fluid) may be used.

During operation of the Kelvin generator, the reservoir 1 typically contains water.

A stream of water 6a and 6b runs from each nozzle 2a and 2b in the reservoir 1.

The first stream of water Ga flows through inducer 4b and into receptacle 3a. The second stream of water 6b flows through inducer 4a and into receptacle 3b.

Importantly, each stream of water 6a and 6b is such that the continuous flow of water breaks up to form discrete droplets within the proximity of the inducers 4a and 4b.

The mechanism that causes the breakup may be an amplification of flow instabilities which may or may not be turbulent.

The separation of droplets from the stream of water causes the physical separation of the charged ions in the water. It is also important, in this kind of apparatus that the droplets are formed while the stream of water is within the inducers 4a and 4b for reasons which shall become clear once the underlying mechanisms of the Kelvin generator have been described.

Before operation of the Kelvin generator commences, the apparatus is in a neutral state with neither of the receptacles 3a and 3b and their corresponding inducers 4a and 4b having any net charge. As a result of the specific arrangement of constituent components of the Kelvin generator, once the streams of fluid start to flow from the nozzles 2a and 2b, forming droplets which fall into the respective receptacles 3a and 3b, any natural small charge imbalance between the two receptacles 3a and 3b is amplified.

Before the Kelvin generator has begun operating it is impossible to predict which way it will charge'. It depends on which way the first natural charge imbalance occurs, i.e. it depends on which of the receptacles 3a and 3b the first excess of either negative or positive ions falls into.

Once a slight charge imbalance has occurred it is amplified as a result of the following processes. Where receptacle 3a experiences a slightly positive charge imbalance (as shown in Figure 1), this net positive charge of the receptacle 3a is transmitted to inducer 4a by conducting connection means 5a such that the inducer 4a also has a net positive charge. The positive charge of inducer 4a acts to attract negative hydroxide ions in the stream of water 6b. As has been described, it is necessary for the stream of water 6b to form into droplets while it is within the inducer 4a.

While the stream 6b is within the inducer 4a, the positive charge of the inducer 4a attracts the negatively charged hydroxide ions and repels the positively charged hydronium ions within the stream Gb. As a result, there is a higher concentration of negative hydroxide ions present in the stream 6b as they are attracted by the positively charged inducer 4a and the positive hydronium ions are repelled back towards the reservoir 1. Accordingly, the droplets which form within the inducer 4a have a net negative charge which they then transmit to receptacle 3b.

Receptacle 3b then becomes increasingly negatively charged with each droplet and the reverse process occurs at inducer 4b which also becomes negatively charged, by virtue of conducting connection means 5b, and attracts the positive hydronium ions in the water stream 6a. These ions are then transmitted by the droplets to the already positive receptacle 3a, which becomes more positive as a resu It.

This amplification process, or positive feedback loop, continues until either an electric discharge between the Iwo receptacles 3a and 3b occurs, the receptacles 3a and 3b become sufficiently charged to start repelling the incoming like charged droplets or the inducers 4a and 4b become sufficiently charged to start attracting oppositely charged droplets which would deposit their charge once they contacted the inducers 4a and 4b. Corona discharge is also a possibility.

Since the invention of the Kelvin generator, although various optimisations and modifications have been made to the above described apparatus by various scientists and science enthusiasts, a commercially useful application of the generator has yet to been found. This is mainly due to the very low efficiencies associated with converting the gravitational potential energy of the water into electrical energy.

Several improvements to original apparatus described by Lord Kelvin have been proposed over the years. Rather than having a single stream of dripping water passing through each of the two conducting rings, multiple streams of dripping water may be used. This increases the total output current as the rate of charge separation is increased as droplets, which act to separate and transmit the charge from the water reservoir to the receiving buckets, are being formed more frequently and are thus transmitting charge more frequently.

Accordingly, it has been proposed to use a ring of nozzles, in place of each of the single nozzles which are traditionally used, each nozzle projecting a single stream of dripping water. Having the nozzles arranged in a ring is advantageous as it allows the stream of dripping water produced by each nozzle to have unimpeded electrostatic interaction with the inducing ring.

Kelvin generators have been used to illuminate light bulbs and power small electric motors. However, such demonstrations have only ever been used to highlight the Kelvin generator's ability to produce electrical energy. As yet there are no practically and/or commercially useful applications for such water-dropping condensers.

The present invention provides a Kelvin generator with greatly improved efficiency such that a useful amount of energy may be extracted from the potential energy of a polar fluid.

Summary of the Invention

An electrostatic generator for generating a potential difference comprising: a first and a second conducting element, each having opposing polarities a first conducting receptacle electrically connected to the first conducting element; a second conducting receptacle electrically connected to the second conducting element; a first active flow controller for receiving fluid and, in use, for controlling fluid flow past the second conducting element into the first conducting receptacle such that the fluid flow interacts electrostatically with the second conducting element; and a second active flow controller for receiving fluid and, in use, for controlling fluid flow past the first conducting element into the second conducting receptacle such that fluid flow interacts electrostatically with the first conducting element, wherein the electrostatic interaction causes a charge separation between the two receptacles, thereby generating a potential difference.

The advantage of such an electrostatic generator is that vastly higher levels of efficiency can be achieved in converting the gravitational potential energy of water into electrical energy. The efficiency of known Kelvin generators is normally in the region of a fraction of a percent. The present electrostatic generator is able to produce efficiencies of at least ten percent. Sufficient electrical energy is produced by the electrostatic generator to self-power the two active flow controllers and provide a surfeit of electrical energy. In the embodiment of the invention which includes a control device, this may also be powered by the electrical energy produced by the electrostatic generator, alongside the two active flow controllers, with a surfeit of electrical energy still being produced.

Either or both of the first and second active flow controllers may be configured to control the fluid flow such that droplet break up occurs at an optimum point in the electric field for inducing charged particles into the droplet.

Either or both of the first and second active flow controllers may be configured to control the fluid flow such that it becomes droplets when the fluid is electrostatically interacting with the respective conducting element.

The droplets may be produced at either or both of the first and second active flow controllers.

The droplets may be produced at a distance of 4mm to 25mm from either or both of the first and second active flow controllers.

A control device may be provided, the control device being configured to control parameters of the electrostatic generator. At least part of the output power of the electrostatic generator may fed back to the control device.

The control device may include one or more of the following: control circuitry, control electronics, signal generator and pressure or flow sensors.

The control device may control the fluid flow produced by either or both of the active flow controllers to become droplets at a region of maximum electrostatic interaction between the fluid flow and the corresponding conducting electrode.

The control device may control the fluid flow produced by either or both of the active flow controllers such that the droplets generated are of a greater number than are produced when the active flow controller[s] is/are inactive.

Either or both of the first and second active flow controllers may generate multiple streams of fluid collectively having the same characteristics as each other.

Either or both of the first and second active flow controllers may comprise a membrane with at least one aperture and an actuator for vibrating the membrane, wherein fluid is supplied to one side of the membrane and vibration of the membrane causes a controlled flow of fluid.

At least part of the output power generated by the electrostatic generator may be fed back to the first and second active flow controllers.

The generator may include a fluid supply and such a fluid supply may be pressurised either by means of hydrostatic pressure generated naturally by fluid in the fluid supply or by means of an artificially generated hydrostatic pressure.

The fluid supply may comprise a single reservoir which supplies fluid to both active flow generators.

Alternatively, the fluid supply may comprise a first reservoir in fluid contact with the first active flow generator and a second reservoir in fluid contact with the second active flow generator. The first and second water supply reservoirs may be electrically insulated from one another or may be electrically connected to one another.

The present invention also provides a method for obtaining a power output using an electrostatic generator as described in any of the options above, the method comprising actively controlling streams of fluid using the first and second active flow controllers which are in fluid contact with a fluid supply.

The streams of fluid may be actively controlled such that they become droplets.

The method may further comprise the step of controlling the parameters of the electrostatic generator such that the fluid droplets are of a predetermined size and are created at a predetermined location.

The first and/or second active flow controller may be configured to cause the fluid flow to become droplets when the fluid is electrostatically interacting with the respective conducting element.

The first and/or second active flow controller may be configured to cause the fluid flow to become droplets such that droplet break up occurs at an optimum point in the electric field for inducing charged particles into the droplet.

Description of the Drawings

The invention will now be described with reference to the accompanying drawings, in which: Figure 1 is schematic representation of a Kelvin generator; Figure 2 is a schematic representation of one example of the present invention; Figure 3 is a schematic cross section through an active flow controller for use in the invention; Figures 4a and 4b show flow generated through the invention when the flow controller is not activated (figure 4a) and when it is activated (Figure 4b) Figures 5a to 5d are perspective views of an active flow controller for use in the invention; Figures 6a and Sb are exploded perspective views of the active flow controller of Figure 5.

Figure 7 is a schematic cross section through an alternative active flow controller for use in the invention; Figure 8 is a schematic cross section through a further alternative active flow controller for use in the invention; Figures 9a and 9b are exploded perspective views of the active flow controller of Figure 7; Figures 1 Oa and I Ob are perspective views of the active flow controller of Figure 8; and Figure 10 is an exploded perspective view of the active flow controller of Figure 8.

Detailed Description

The electrostatic generator described herein may be considered to be a Kelvin generator or a modified Kelvin generator. It may also be considered to be a completely new kind of electrostatic generator which works on the same principles as known Kelvin generators.

Figure 2 is a schematic diagram showing an exemplary configuration of the electrostatic generator of the present invention. The electrostatic generator comprises a reservoir 201, two active flow controllers 202a and 202b, two conducting receptacles 203a and 203b and two conducting elements (inducers) 204a and 204b which are conductively connected to conducting receptacles 203a and 203b via conducting means 205a and 205b respectively.

The schematic diagram in Figure 2 also shows a signal generator 206 connected to the active flow controllers 202a and 202b and an optional resistor 207 connected between conducting receptacles 203a and 203b the resistor 207 being present to absorb the power generated for measurement purposes. It will be understood that the resistor may be replaced with an output terminal and the power generated may be used to power a load 207.

The flow path of the fluid in the system shown in Figure 2 is similar to the flow path of the fluid of the kelvin generator shown in Figure 1. Fluid flows from reservoir 201 to the active flow controllers 202a and 202b. Upon leaving the active flow controllers, the fluid passes through the inducing elements 204a and 204b and flows into conducting receptacles 203a and 203b. Accordingly, the amplification process occurs and the gravitational potential energy of the fluid is converted into electrical energy, as has already been described in relation to the system ofFigurel.

An exemplary fluid suitable for use with the electrostatic generator shown in Figure 2 is water. The presence of the oppositely charged hydroxide and hydronium ions in water enables the amplification process to occur as a result of the separation of the ions. Other suitable polar fluids, solvents or solutions may also be used. These include Acetic Acid, Dimethyl Sulfoxide and Methanol.

The reservoir 201 may comprise a single reservoir for supplying fluid to both active flow controllers 202a and 202b. Alternatively, instead of a single reservoir, there may be two separate reservoirs each in contact with active flow controllers 202a and 202b respectively (not shown). These two reservoirs may be electrically insulated from one another so that no charge is able to flow between them. Alternatively, they may be electrically connected to one another. Possible reasons for having two separate reservoirs are where two separate supplies of water are to be passed through respective sides of a kelvin generator.

The configuration of the active flow controllers 202a and 202b is discussed in substantial detail below in the discussion of Figure 3 which depicts a schematic diagram of an active flow controller. Receptacles 203a and 203b are electrically insulated from the earth and also electrically insulated from each other. The receptacles themselves may be made of a conducting material. Alternatively, the receptacles 203a and 203b may be made of an insulating material and part of conducting means 205a and 205b may be inserted into each receptacle respectively such that it is in conductive contact with any fluid received within the receptacle.

Optionally, the receptacles 203a and 203b may be conductively connected to each other with a load 207 placed in between them as shown in Figure 2 when operating as a power generator.

Signal generator 206 generates a signal which is passed to the active flow controllers. The active flow controllers 202a and 202b and the inducing elements 204a and 204b and the signal generator shall now be described in detail with reference to Figure 3.

Figure 3 shows an exemplary active flow controller 202 and inducing element 204 which may be used (and is shown) in the system shown in Figure 2. The active flow controller 202 comprises a housing 301 with two apertures 305. One of the apertures is for allowing fluid from the reservoir 201 to enter the housing 301 of the active flow controller 202. The second aperture is for priming the actuator by allowing air to escape and water to fill entirely the space for the connection of an optional monitoring pressure gauge if required.

Membrane 302 encloses the lower portion of casing 301. The membrane has at least one aperture 306 which allows the fluid to pass through it. The membrane shown in Figure 3 has two apertures 306 visible at either ends of the membrane 302. In one embodiment of the present invention the membrane 302 has a plurality of apertures 306 arranged in a ring around a centre point of the membrane 302. Such an arrangement can clearly be seen in Figures 5a, 5c and 5d and Figures 6a and 6b. An a-ring 309 is provided between the lower portion of casing 301 and the upper surface of the membrane 302.

Other suitable configurations of apertures are envisaged, for example having multiple rings of apertures concentrically arranged around a centre point of the membrane 302.

The membrane may be made of Kapton or any other suitable material.

Attached to the membrane 302 is an actuator 303 for vibrating the membrane. In the exemplary active flow controller 202 of Figure 3, the actuator is attached to the membrane between the two apertures 306. The actuator may be a piezoelectric element connected to an oscillating power supply which may be provided by signal generator 206. As shown more clearly, for example, in Figure 5d, the actuator 303 may be circular in shape such that it sits concentrically within the apertures and its centre point may be located at a centre point of the membrane.

Optionally, a clamping plate 308 (shown clearly in Figures 3, 6a and Sb) may be used to hold the membrane 302 firmly in place.

As shown in the exemplary active flow controller 202 of Figure 3, an inducing element 204 may be attached to the active flow controller via an attachment arm 304. Two such attachment arms are shown in Figure 3, however, it is envisaged that a single attachment arm or a plurality of attachment arms may also be used to attach the inducing element 204 to the active flow controller 202. The attachment arm 304 may be made of an insulating material such that it electrically insulates the active flow controller 202 from the inducing element 204.

In another embodiment, the active flow controller 202 and the inducing element 204 may not be attached to each other. The inducing element 204 may also be removably attached to the active flow controller 202.

In the active flow controller shown in Figure 3, fluid flows into the active flow controller casing 301 via aperture 305 and into the chamber defined by the casing 301 and the membrane 302. Fluid then leaves the active flow controller 202 through the aperture or apertures 306 in the membrane 302. The fluid then flows through the inducing element 204 via apertures 307 in the inducing element 204.

The actuator 303 vibrates membrane 302 whilst fluid is flowing through the active flow controller 202. The vibrations in the membrane 302 caused by actuator 303 act to control the flow of fluid through the aperture 306 such that the stream of fluid leaving the aperture 306 becomes droplets at a predetermined distance from the active flow controller 202.

The distance at which the stream of fluid leaving aperture 306 becomes droplets can be controlled by varying parameters such as the diameter of aperture 306 in the membrane 302, the frequency with which the actuator 303 vibrates the membrane 302 and the pressure of the fluid supplied to the active flow controller 202. Once the distance at which the fluid stream leaving aperture 306 becomes droplets is known, for a specific diameter of aperture 306 and a specific frequency of membrane vibration, the length of attaching means 304 can be constructed such that the conducting element 204 is attached to the active flow controller 202 such that it is preferably situated at or slightly before or after the location of droplet formation in the fluid stream.

For membranes 202 with multiple apertures 306, the configuration of the apertures 306, namely, their location on the membrane and their diameters can be configured such that, in combination with a specific vibrational frequency of the membrane 302, all streams of fluid produced by the apertures form droplets at substantially the same distance from the active flow controller 202.

Accordingly, the electrostatic generator shown in Figure 2, which makes use of active flow controllers 202a and 202b integrated with inducing elements 204b and 204a respectively and which are both of the type of active flow controller shown in Figure 3, is an electrostatic generator with far greater efficiency than that of known kelvin generators.

The vibrations of the membrane 202 also act to produce an increased number of droplets, these droplets being of smaller size than would normally be produced.

The vibrations of the membrane 302 do not necessarily act to accelerate the fluid to flow. As such, the energy consumption of the device is minimised. It is envisaged that some acceleration of the fluid flow could be possible, in which case the energy consumption of the flow controllers would increase.

The fluid stream leaving aperture 306 of the active flow controller 202 may become droplets as it leaves the aperture 306. The fluid flow may also become droplets at a predetermined distance from the aperture 306 of the active flow controller 202. Preferably, the fluid stream leaving the aperture 306 becomes droplets when the fluid is electrostatically interacting with the conducting element through which it passes. An exemplary distance at which droplet formation occurs might be a distance of 19 millimetres from the aperture 306.

The signal generator 206 shown in Figure 2 controls the frequency at which the actuator 303 vibrates the membrane 302 of the active flow controllers 202a and 202b shown in Figure 2. The signal generator 206 may be one of many types but, for example purposes, the signal generator 206 might be a general purpose waveform generator chip such as the Analog Devices chip AD9837 or a general purpose laboratory instrument such as the Thurlby Thandar Instruments (TTi) TG1006 DOS Function Generator. The signal generator may have very low power consumption in use and it may be powered by the power generated by the electrostatic generator whose active flow controllers it is connected to. The signal generator 206 may comprise part of a control device configured to control the parameters of the active flow controllers 202a and 202b.

The control device may comprise control circuitry, control electronics and the signal generator. At least part of the output from the electrostatic generator may be fed back into the control device which in turn may power the active flow controllers 202a and 202b. The active flow controllers 202a and 202b may have a very low consumption such that the energy produced by the electrostatic generator is sufficient to power the control device, the active flow controllers 202a and 202b and produce a surfeit of energy.

In one example of a low power active flow controller, this is constructed as a moulded plastic chamber with a Kapton disc forming the bottom of the chamber in which a plurality, for example 60 of laser machined holes of diameter 0.20mm in a circular pattern arranged concentrically with the chamber to which is bonded on the underside a circular nickel disc with a diameter smaller than the pitch circle diameter of the orifices. Preferably the brass disc diameter is around 85% of the diameter of the orifices and the kapton disc being fixed at a diameter of around 130% the diameter of the orifices. With this configuration the brass disc which is stimulated by an electrically excited bonded piezo material can vibrate with a low energy input typically around 350 microWatts to produce sufficient stimulation to control the droplet break up distance. It will be obvious to the skilled person that alternative configurations could be utilised, for example a linear array of orifices could be used in a rectangular construction.

A possible start up process of the electrostatic generator shown in Figure 2 will now be described. This is merely an exemplary process and there are other ways in which the process of power generation may commence. In this example, reservoir 201 is filled with water such that hydrostatic pressure is generated naturally by the water contained therein. This pressure is transmitted to both active flow controllers 202a and 202b and fluid streams pass through the apertures 306 and each of the active flow controllers 202a and 202b. Some electrostatic power generation will occur as the streams of fluid pass past inducing electrodes 204a and 204b and into conducting receptacles 203a and 203b and the previously described amplification process will occur. After a period of time, enough charge will have built up such that the control device comprising the signal generator 206 may be powered by the generated energy.

The signal generator 206 then sends a signal to the actuators 303 of the respective active flow controllers 202a and 202b. As the membranes 302 of the active flow controllers 202a and 202b are vibrated, the efficiency of the electrostatic generation process is increased and more power is generated.

An alternative start-up process may involve providing the signal generator 206 with power from a start-up power supply such that the membranes 302 of the active flow controllers 202a and 202b are oscillating from the outset.

If, during start-up, the electrostatic generator is initially operating without the membrane 303 of the electrostatic flow controllers 202a and 202b vibrating, some charge separation still occurs as the fluid streams leaving the apertures in the membranes 303 are still becoming droplets. However, the droplets are not formed in a controlled and predetermined location and the efficiency of the generator is therefore significantly lower.

This effect is shown in Figures 4a and 4b which show fluid streams leaving an active flow controller 202 and passing through a inducing element 204. Figure 4a shows the droplet generation when the membrane 302 of the active flow controller 202 is not being vibrated and Figure 4b shows the droplet generation when the membrane 302 of active flow control generator 202 is being vibrated.

It can clearly be seen in Figure 4a that many of the fluid streams are not producing droplets until after they have passed through the inducing element 204. Conversely, the fluid streams in Figure 4b are all producing droplets as they pass through the inducing element 204 resulting in an increase in ion separation and, consequently, efficiency. It can be seen that the fluid streams in Figure 4b also form droplets at substantially the same distance from the active flow controller 202.

During the operation of an electrostatic generator such as the electrostatic generator of Figure 2, the mass of water in reservoir 201 may reduce as water flows through the apparatus. As such, the pressure generated by the water in reservoir 201 may reduce over time. This reduction in pressure may act to reduce the distance from the electrostatic generators 202a and 202b at which droplet generation occurs. This change may be accounted for by changing the vibrational frequency of the membranes 303 of the active flow controllers 202a and 202b. This may be achieved by changing the signal produced by the signal generator 206 as the pressure changes using feedback from a pressure transducer located in the resevoir.

The active flow controllers, such as those used in the system shown in Figure 2, may have very low power consumption. For example, an exemplary active flow controllers may have a power consumption of less than 6 milliwatts.

Figure 5a to 5b show a perspective solid and wireframe views of an exemplary active flow controller such as the active flow controller shown in Figure 3.

Figures 6a and 6b also show the exemplary active flow controller in an exploded perspective view. The constituent parts, which have been described in detail above, can be seen.

In an alternative embodiment (shown in Figures 7, 8, 9a, 9b and lOa to bc), the active flow controller may be constructed differently. In place of the membrane 302 connected to an actuator 303 (as described above and shown in Figure 3), a membrane or plate 302 with at least one aperture or a plurality of apertures 306 which may be arranged in a similar fashion to the apertures of the membrane of Figure 3 (as described above). However, in this embodiment, no actuator 303 is connected to the membrane or plate 302.

Instead, the actuator 803 is present elsewhere in the system and is in communication with the fluid which is supplied to the active flow controller 202 via aperture 305 in such a way that waves or pressure waves are created in the fluid. These waves are communicated to the membrane or plate at which point the above described droplet breakup effect occurs.

The actuator 803 may be connected to a further membrane 802, which when actuated, is capable of generating waves or pressure waves in the fluid.

Alternatively, the actuator itself may be constructed in such a way as to generate pressure waves in the fluid itself (not shown).

The actuator and (if present) further membrane may be, but is not limited to being, present in the reservoir 201 which supplies the active flow controller 202 with fluid (not shown). Upon actuation of the actuator, waves or pressure waves may be generated in the reservoir and are then transmitted to the membrane or plate of the active flow controller creating the above described droplet break up effect.

Figures 9a and 9b show an active flow controller which does not include an actuator. Such an actuator would be present in the embodiment of the present invention where the actuator is located elsewhere in the elsewhere in the system and is in communication with the fluid which is supplied to the active flow controller.

The further membrane may also be contained within the housing 301 of the active flow controller 202. The waves or pressure waves would then be generated within the fluid contained within the active flow controller 202 and would cause the droplet break up effect upon reaching the membrane. Figures 6 and ba to bc show an embodiment where the actuator 803 and further membrane 802 disposed at the opposite end of the active flow controller housing 301 to the membrane 302. Thus, any pressure waves generated would be directly incident upon the membrane 302. In this instance, the apertures 305 have been moved to the side of the housing to accommodate the inclusion of the actuator 803 and further membrane 802. The actuator 803 and further membrane 802 may also be disposed elsewhere within the housing 301.

Claims

CLAIMS1. An electrostatic generator for generating a potential difference comprising: a first and a second conducting element, each having opposing polarities a first conducting receptacle electrically connected to the first conducting element; a second conducting receptacle electrically connected to the second conducting element; a first active flow controller for receiving fluid and, in use, for controlling fluid flow past the second conducting element into the first conducting receptacle such that the fluid flow interacts electrostatically with the second conducting element; and a second active flow controller for receiving fluid and, in use, for controlling fluid flow past the first conducting element into the second conducting receptacle such that fluid flow interacts electrostatically with the first conducting element, wherein the electrostatic interaction causes a charge separation between the two receptacles, thereby generating a potential difference.
2. The electrostatic generator of claim 1, wherein either or both of the first and second active flow controllers are configured to control the fluid flow such that droplet break up occurs at an optimum point in the electric field for inducing charged particles into the droplet.
3. The electrostatic generator according to either claim I or claim 2, wherein either or both of the first and second active flow controllers are configured to control the fluid flow such that it becomes droplets when the fluid is electrostatically interacting with the respective conducting element.
4. The electrostatic generator according either of claim 2 and claim 3, wherein the droplets are produced at either or both of the first and second active flow controllers.
5. The electrostatic generator according to either of claim 2 and claim 3, wherein the droplets are produced at a distance of 4mm to 25mm from either or both of the first and second active flow controllers.
6. The electrostatic generator of any preceding claim, further comprising a control device configured to control parameters of the electrostatic generator.
7. The electrostatic generator of claim 6, wherein at least part of the output power of the electrostatic generator is fed back to the control device.
8. The electrostatic generator of claim 6 or claim 7, wherein the control device includes one or more of the following: control circuitry, control electronics, signal generator and pressure or flow sensors.
9. The electrostatic generator of any preceding claim, wherein the control device controls the fluid flow produced by either or both of the active flow controllers to become droplets at a region of maximum electrostatic interaction between the fluid flow and the corresponding conducting electrode.
10. The electrostatic generator of any preceding claim, wherein the control device controls the fluid flow produced by either or both of the active flow controllers such that the droplets generated are of a greater number than are produced when the active flow controller[s] is/are inactive.
11. The electrostatic generator of any preceding claim, wherein either or both of the first and second active flow controllers generate multiple streams of fluid collectively having the same characteristics as each other.
12. The electrostatic generator of any preceding claim, wherein either or both of the first and second active flow controllers comprise: a membrane with at least one aperture; and an actuator for vibrating the membrane, wherein fluid is supplied to one side of the membrane and vibration of the membrane causes a controlled flow of fluid.
13. The electrostatic generator of any preceding claim, wherein at least part of the output power generated by the electrostatic generator is fed back to the first and second active flow controllers.
14. The electrostatic generator of any preceding claim, further comprising a fluid supply.
15. The electrostatic generator of claim 14, wherein the fluid supply is pressurised either by means of hydrostatic pressure generated naturally by fluid in the fluid supply or by means of an artificially generated hydrostatic pressure.
16. The electrostatic generator of any claims 14 and 15, wherein the fluid supply comprises a single reservoir which supplies fluid to both active flow generators.
17. The electrostatic generator of any of claims 14 and 15, wherein the fluid supply comprises: a first reservoir in fluid contact with the first active flow generator; and a second reservoir in fluid contact with the second active flow generator.
18. The electrostatic generator of claim 17, wherein the first and second water supply reservoirs are electrically insulated from one another.
19. The electrostatic generator of claim 17, wherein the first and second reservoirs are electrically connected to one another.
20. A method for obtaining a power output using the electrostatic generator of any preceding claim, the method comprising actively controlling streams of fluid using the first and second active flow controllers which are in fluid contact with a fluid supply.
21. The method of claim 20, wherein the streams of fluid are actively controlled such that they become droplets.
22. The method of claim 21, further comprising controlling the parameters of the electrostatic generator such that the fluid droplets are of a predetermined size and are created at a predetermined location.
23. The method of any of claims 20 to 22, wherein the first and/or second active flow controller is configured to cause the fluid flow to become droplets when the fluid is electrostatically interacting with the respective conducting element.
24. The method of any of claims 20 to 22, wherein the first and/or second active flow controller is configured to cause the fluid flow to become droplets such that droplet break up occurs at an optimum point in the electric field for inducing charged particles into the droplet.