WO2009141644A9

WO2009141644A9 - Natural and mechanical-driven generator system

Info

Publication number: WO2009141644A9
Application number: PCT/GB2009/050533
Authority: WO
Inventors: Michael David Maimone
Original assignee: Michael David Maimone
Priority date: 2008-05-19
Filing date: 2009-05-18
Publication date: 2010-05-06
Also published as: WO2009141644A3; GB0808998D0; WO2009141644A2

Abstract

An electrical generator which is adaptable to be driven by different energy sources by replacing one or more impellers with an interchangeable impeller of a different specification is provided. Also provided are methods and systems for the generation of electricity utilising the described generator.

Description

NATURAL AND MECHANICAL-DRIVEN GENERATOR SYSTEM

The present invention relates to the generation of electricity. The invention provides a system, and methods, for the generation of "green" (i.e. non-polluting) electricity by harnessing the kinetic energy latent within natural and mechanical systems and converting it to electricity with high efficiency.

With the growing concerns over the use of fossil fuel and nuclear power stations, there is at present a move to replace these energy sources with "clean energy" and reduce the carbon footprint related to the generation of electricity. Various means for reducing a carbon footprint have been proposed, and some are more efficient than others.

Conventionally, the generation of green electricity takes place both on a large-scale, industrial basis and on a smaller, "micro" level. On the industrial scale, one of the best developed approaches involves generation of electricity by using turbines driven by water (i.e. hydroelectricity). Examples include the use of man-made dams such as are to be found in China at the

Three Gorges complex or through dedicated hydroelectric power stations such as that at Dinorwig in Wales. At the smaller scale generally, and at the domestic level in particular, green electricity is commonly produced by use of solar panels and photovoltaic cells capturing the sun's energy and by wind turbines harnessing wind power.

Both of the approaches mentioned above have significant drawbacks. Large-scale hydroelectric plants are often highly damaging to the environment and hugely expensive to build. Small-scale, domestic approaches have yet to reach a stage in their development at which they are economically attractive.

In both cases, continuity of supply is an issue: large-scale hydroelectric plants are at the mercy of the supply of water, which is often seasonal, and so run the risk of "brown outs" (where they fail to generate sufficient voltage to be viable). Smaller scale approaches run the risk of periods of total blackout, where, for example, the sun fails to shine at all or there is no wind to power wind turbines. Each of the forms of green power generation mentioned above is designed to recover energy from a specific environmental source. However, to significantly reduce the carbon footprint one would wish to be able to harness the energy from fluid, heat, light and mechanical sources, as the opportunities arise. The present invention fulfils this need.

A significant drawback of conventional generators of clean energy is that they are redundant when their energy source ends and/or they are removed from their prescribed environment. It is an object of the present invention to provide a readily adaptable generator that can be removed from one dormant energy source and placed in an energy rich environment.

The invention therefore provides an electrical generator comprising a cylindrical core coaxially mounted within a hollow cylinder, said core and cylinder having one or more rotor/stator sets disposed thereon, wherein at least one of the core and the cylinder is coupled to one or more impeller(s) which drives rotation of the coupled core/cylinder relative to the other part, characterised in that the generator is adaptable to be driven by different energy sources by replacing one or more impellers with an interchangeable impeller of a different specification.

The ability of the generator of the invention to function in natural and mechanical systems is conferred by the interchangeability of the impellers, fluid conduits, outer casings, aft sections and components affecting fluid and mechanical dynamics, all of which can be removed and replaced to change the function, for example, from a fluid driven system to one which is driven by heat or light; other changes allow the generator to operate as a generator set (see Figure 1 ).

Accordingly, the generator can be easily "refitted" to function in several different energy sources. So, for example, if an end user were to have multiple generators according to the invention collecting energy from the fluid, heat, light and mechanical processes on their premises, they would have the opportunity to refit individual generators as necessary to concentrate them on the dominant energy source. There is also an opportunity for the generator manufacturers to adapt this concept of the bespoke conversion kit that would enable their models to use this system and method of "changing out" impellers, casings conduits and aft sections. The present invention provides an electrical power generating system that is environmentally friendly, inexpensive, easy to install and maintain and takes advantage of relatively consistent, predictable and reliable sources of energy, as well as being capable of providing power when sources of energy are less regular. The features of the generating system of the invention are described with reference to the appended figures, of which:

Figure 1 is an exploded view of a generator according to the invention showing its component parts, together with examples of interchangeable components adapted for specific applications. Figure 2 shows a longitudinal cross-section of a fluid-driven generating system according to the invention.

Figure 3 shows a transverse cross-section of a fluid-driven generating system according to the invention.

Figure 4 shows a self-contained system for generating electricity according to one embodiment of the invention.

Figure 1 shows an example of a generating system according to the invention, in which, the rotor (a) is secured to the stator (b) with internal supports (c). These components are inserted into the outer casing (d). The aft section of the generator (e) is interchangeable with an impeller (g) or other aft sections affecting mechanical or fluid dynamics: examples shown are ballast (f) and weather vane (h). A buffer plate (i) is located between the forward impeller (j) and the rotor (a). The forward impeller (j) is interchangeable allowing the generator to be driven by wind (k), marine (I), light and heat (m) or mechanical (n) energy. All forward and aft sections are secured in place by two bolts (o) that are protected with end caps (p). The generator is inserted into the rear section of the fluid chamber (q) which is then secured to the forward section of the fluid chamber (r).

The generator of the invention may be adapted for generating electricity from controlled fluid flow, i.e. fluids flowing through pipes. Accordingly, in one embodiment, the invention provides a fluid-driven electrical power generating system comprising a tubular conduit within which is coaxially mounted a sealed generator unit comprising one or more rotor/stator sets, said rotor(s) being driveably coupled to an impeller adapted to rotate upon flow of fluid through the conduit. This embodiment of the invention is illustrated in Figures 2 and 3 which also illustrate features applicable to generators of the invention in general, i.e. the features and advantages described below in relation to "pipeline" generators (controlled fluid flow) apply mutatis mutandis to the invention as a whole (any natural, i.e. environmental, or mechanical drive source). Figures 2 and 3 show a generating system which comprises a tubular conduit (s) within which is coaxially mounted a tubular generator unit comprising one or more rotor/stator sets (the rotor (a) being the rotating part of the generator and the stator (b) being the stationary part). Preferably, the generator unit comprises multiple rotor/stator sets arranged in-line. In this example the armature windings (t) in which the electrical current is generated are on the rotor and the magnets (u) providing the magnetic field are on the stator (Fig. 3), but they can equally be arranged the other way around. The magnetic field can be provided by permanent magnets, as in Fig. 3, or by electromagnets. The desired number of rotor/stator sections (magnets and coils) is arranged in-line to create a cylinder with one and a core with the other. As an example, Fig. 3 shows the magnets (u) arranged to form the cylinder and the coils (t) forming the core. The rotor and stator are contained within the generator's outer casing (d) and are held in place fore and aft and, if necessary, mid-section by internal mounts (c) secured to the outer casing. The generator unit can additionally be secured to the tubular conduit (outer pipe) by chamber mounts (v) which hold the generator unit in place. The streamlined shape of the generator unit causes minimal resistance to the flow of fluid through the conduit.

In the fluid driven generator system illustrated in Fig. 2, the generator internal mounts (c) are held in place by bolts (w) that pass through the fluid chamber (s) within the chamber mounts (v). In an alternative embodiment, the internal mounts are still seated in the outer casing's forward and aft sections but are fitted in place by ridges on their circumference. These mounts slot into a corresponding channel on the inner surface of the outer casing. The outer casing also has ridges on its outer surface that do not run its entire length but fall just short fore and aft. For example, there may be four such ridges located at 12, 3, 6 and 9 o'clock. These ridges cooperate with corresponding grooves on the inner surface of the tubular conduit which fall short at the aft acting as a stop and preventing the generator unit from sliding out. The rotor is collared with the forward internal mount, inserted into the outer casing and secured to the forward impeller in similar fashion to Fig. 2. The aft of the generator is secured and sealed similar to the system of Fig. 2. Contacts can be housed in the aft and all wires exit via a single point. The aft of the outer casing is similarly ridged to cooperate with grooves in an aft section of tubular conduit. Tubular conduit aft and mid- sections are secured to one another with external fixings. A forward section of the tubular conduit will have internal ridges corresponding in position and shape to the ridges of the outer casing. The tubular conduit's internal ridges extend into the fluid conduit's midsection grooves and butt against the outer casing's ridges. The tubular conduit's forward section is secured to the tubular conduit's mid- section with external fixings.

The rotor(s) of the generator unit is/are driveably coupled to a forward (upstream) impeller. The forward impeller may be directly connected to the rotor or attached to a forward interface/buffer plate which is in turn connected to the rotor(s), as shown in Fig. 2. Flow of fluid through the conduit causes the impeller to rotate which in turn causes rotation of the rotor(s). The impeller is shaped such that it is caused to rotate by fluid flow when pointed upstream. For example, the impeller may comprise fin shaped blades running fore and aft in spiral or other formations. The dimensions and presentation (e.g. pitch/slope) of the fins are selected to provide efficient drive to the generator while at the same time presenting minimal friction and causing minimal turbulence so as to cause minimal resistance and disturbance to the flow of fluid. Finned impellers of different pitch and/or size may be designed to suit different fluids and conditions. Where a larger impeller sized to reduce the area within the fluid conduit has a convex outer surface, and when inline channels are cut into it to allow fluid to flow through the channel causing the impeller to rotate which in turn causes rotation of the rotor, with the channels preferably spaced far enough apart from one another a venturi will be created in the impeller area of the fluid conduit.

The forward and aft impeller may alternatively comprise a smooth surface while fan blades extend on a prop shaft fore and/or aft into a venturi created in the upstream and downstream of the pipe work. The appropriate shape for the impellers, fluid conduits and aft sections for a particular application can be readily determined by one skilled in the art following well-known principles of fluid and mechanical dynamics.

The outer casing of the generator unit is sealed from the fluid stream providing an airtight/watertight generator. A forward seal with the impeller at the forward buffer (interface) plate allows unimpeded rotation. Because the generator unit is sealed from the fluid stream, the likelihood of foreign object damage to the system is minimised. Also, because the magnets are contained within the generator unit's outer casing, they do not attract any magnetic particles which may be present, e.g. from foreign objects/debris, in the fluid stream, and which might otherwise accumulate on the rotor or stator causing turbulence in the fluid stream, obstruction of rotor movement and damage to generator parts. The sealed generator also has the advantage of reducing the number of moving parts in contact with the fluid; minimising wear and tear and thus maintenance requirements, with associated benefits in terms of reduced cost and down time. If desired, the cylinder of the generator, within the outer casing, may be divisible into two halves along its length. The half sections are secured to one another by locking clips along each side, or locking clips on one side and hinges on the opposite side. This allows the cylinder - once removed from the forward section, outer casing and aft section - to be opened for easy access.

The aft or tail (downstream) end of the generator unit is shaped so as to minimise turbulence and maintain flow/pressure. For example, the aft end may have a convex outer surface. The aft end may be an impeller and directly connected to the rotor or, as shown in Fig. 2, the aft end may be secured to the aft interface/buffer plate which is in turn connected to the mid section, causing an airtight/watertight seal. The contacts can be housed in the internal mounts, forward impeller or the aft allowing the wiring to exit through either mid section or aft or forward mounts. The buffer plates may, for example, be constructed from a durable mesh plate moulded within a suitable material. The forward buffer plate may be provided with appropriate type holes to accommodate fixings for securing the impeller and rotor. Fixings may be of a quick-release design to facilitate easy interchange of parts, e.g. impellers.

In operation, fluid flowing through the electrical power generating system of the invention causes the impeller to rotate, driving the generator and producing electricity. The fluid flows around the generator unit, remaining on course to its destination through the channel created between the generator unit's outer casing and the tubular conduit. The electricity produced can be used, stored or supplied.

If desired, the aft section and/or the outer casing of the mid (main) section of the generator unit may additionally be finned to drive the rotor. The outer casing is secured in place and allowed optimum rotation by seals on the buffer plates. Mid section fins are useful to aid drive when multiple generator units are configured in tandem.

If desired, the system may be modified such that the forward impeller drives the core in one direction and the mid and/or aft impellers(s) rotate the cylinder in the other or vice versa.

The forward impeller and aft section may be conveniently secured by axially arranged bolts (see Fig. 2) whose heads are covered, after fitting, by removable, streamlined end caps to restore the point of the nose cone/aft section.

Another configuration is ideal when the forward, mid and aft sections are impellers. The streamline end caps of the forward and aft sections may incorporate supports that extend forward and aft and slot into corresponding grooves set in the forward and aft sections of the inside of the fluid conduit thereby negating the requirement for other mounts within the fluid conduit.

These forward and aft mounts are secured to the forward and aft sections of the generator that are in turn secured to the generators mid section. Once fitted to the respective ends of the generator, these end cap mounts will allow the generator to rotate freely within the fluid conduit. In this embodiment, a fixing - which extends from the aft end cap mount directly to the aft internal mount within the generators mid section - keeps the stator (cylinder or core) from rotating. Any fin/blade (impeller) faces may be adapted to maximise surface contact with the fluid flow e.g. with surface ridges or golf ball-like pitting.

In liquid, e.g. water, systems, the generator system can be fitted with an integral automatic air vent, as well as an integral drain off valve for ease of maintenance. If desired, multiple generators can be configured in tandem by coupling the aft of one generator mid section to the forward of other generators mid section.

If required, heat can be removed from the generator and dissipated into the atmosphere without affecting the fluid's temperature, by the internal mounts absorbing and relaying the heat to their support bolts whose heads are located outside the unit and can be designed to radiate heat. The relevant chamber mounts will also insulate the bolts thereby further protecting the fluid from heat.

Another means to cool down the generator is to have air/liquid drawn through tubes that extend from the surface of the outside of the fluid chamber and travel around the inner casing of the generator collecting heat and then back to the out side of the fluid chamber expelling the heat by using micro pumps that can be powered by the generator.

The heat can also be converted into energy with the use of thermal electric strips shrouding the outer casing and or the cylinder. The system may further comprise a cistern supply loop to feed the generator in the event of an interruption to the regular supply or as a mobile unit (see Fig. 4 ).

In a further embodiment, the invention provides a method of generating electricity, in which compressed gas is used to pressurize a fluid through the fluid conduit of one or more fluid-driven generators as described above, thereby causing the impeller to rotate. The compressed gas may be from cylinder, cartridge, electronic or mechanical means.

In a related embodiment, the invention provides a self-contained system for generating electricity according to the above described method. An example of such a system is illustrated in Fig. 4, wherein two vertically stacked tanks are used, with the top tank (A) filling the lower tank (B) via a supply pipe (C) that incorporates an inline strainer (D) and a non return valve (E) preventing back flow from (B) to (A). Pipe (C) also has a small inline fluid driven generator (F) to generate electricity for system controls. Once (A) has filled (B), the fluid in (B) is compressed by using the compressor/control panel (G) to send compressed gasses via a pipe (H) fitted with a non return valve (I), a mini generator (J) and a pressure regulator (K). The pressure regulator (K) is wired to the compressor/control panel (G) calling for more or less pressure from the supply (L). Once operating pressure is reached, the automatic gate valve (M) in the return pipe (N) opens and the pressurised fluid escapes tank (B) and empties into tank (A) via pipe (N) which is also fitted with a non return valve (O) and a mini generator (P). The required operating pressure is maintained by the pressure regulator (K). The fluid of tank (B) can only exit via the main generator's fluid conduit (S) in tank (B) causing rotation of the impellers and thereby generating electricity. Compressed air is supplied via compressed air cylinders, electrically or mechanically operated compressor (R) micro generators in the system pipe work or by electricity generated by mechanical force, the main generator (Q), or by an external power source. Multiple units according to the present embodiment may be supplied compressed air from one unit.

The methods and system of this present invention allow the manufacturer of this product to present the user with a "plug and play" system of differently specified interchangeable fittings - in particular, the impeller, generator unit outer casing and aft sections - optimised for different specific applications so that the user is able to adapt the generating system to their particular application with minimum effort (such as adjustment). The interchangeable impellers, mid and aft outer casings and fluid conduits, configurations of magnets/coils, rotor/stator and materials offer one skilled in the art the possibility to construct a bespoke generator. This flexibility is an advantageous feature of the design such that the generator will find applications in aeronautical, automotive, rail and marine design, as either an integral or "bolt on" component.

The generator system described herein overcomes the limitations of existing green electricity generation systems, with reduced environmental impact, by efficiently and economically harnessing previously untapped latent energy in natural and mechanical systems. One example outside the controlled fluid environment would be a row of generators according to the invention elevated from the river bed, sea floor or placed in a sluice, which could be used to generate electricity from river or tidal flow.

This convenient, efficient, adaptable, zero emission fluid-driven electrical power generating system operates near unobtrusively in a fluid supply while avoiding waste, misuse, undue consumption, interruption to the required fluid flow, contamination and cavitations.

Once removed from a controlled fluid environment, the generator is easily modified for use in different environments. The impellers and mid and aft outer casing and or aft components are replaced with impellers, mid and aft outer casings and aft components designed to improve fluid and or mechanical dynamics constructed to higher tolerance levels allowing the generator to operate within other fluid systems. Another set of interchangeable impellers, mid and aft outer casings and aft components designed to improve fluid and or mechanical dynamics allow the same generator to operate in and be driven by the elements or run as a directly or indirectly powered genset. As an example, an inline fluid driven generator system as exemplified herein may be converted to run on wind, solar or heat power as follows: the generator system is removed from the pipeline; the generator unit is removed from the tubular conduit; forward and aft sections are removed by releasing the respective fixing bolts; the outer casing is removed and replaced with an appropriate casing suited for the new environment; the new casing is then made secure (the new casing may be provided with retractable, telescopic legs to create a stand for the generator when disposed vertically). Other attachments allow the generator to be disposed horizontally; new forward and aft sections are secured to buffer plates (when configured to operate in the wind the aft section may be an impeller or provided with fins to act as a weather vane when the generator is disposed horizontally, or weighted to act as ballast when disposed vertically; if the generator is disposed vertically, an adjustable impeller may be provided, fixable between 0 and 90°, which may be locked facing the prevailing wind or manually of automatically rotatable to adapt to changing wind direction).

Impellers that operate by heat and or light are similar in shape to a paddle wheel; whereby one side of each paddle is designed to reflect heat or light and the other is designed to absorb heat or light. This then applies to each paddle and is laid out in such a way that when the paddles are exposed to heat or light, rotation of the paddle wheel occurs thereby causing rotation of the rotor and the generation of electricity.

The embodiments of this present invention may be hardwired or wirelessly connected to a control panel displaying the condition/efficiency of the generating system. The generating system of the invention is scalable to any required size. The inherent flexibility within this system is particularly suited to most markets, reducing the consumer's energy costs as well as reducing the total demand for electricity placed upon suppliers.

The generator systems of the invention may be modified and/or added to in accordance with what is known in the art, depending on the intended application, without departing from the scope of the claimed invention. Examples of such modifications include:

• Increasing output by using a series of single magnets and coils running the length of the generator unit • Reducing diameter by embedding the magnets, coils and contact wires into rotor/stator

• Liquid magnet used as bearings, seals, superconductors etc.

• Using an Archimedes screw in the axial centre of the rotor, leaving the forward and aft impellers as static or aiding the foreword/aft impellers as an additional rotation provider

A further application of the electricity generating system of the invention can be envisaged in deep-sea exploration, where descent through the water causes rotation and electricity is stored. At the prescribed depth the generators can become motors for navigation. Recharging the batteries can be achieved by filling a balloon with compressed air such that the unit is drawn to the surface, generating electricity along the way. Units of this kind may be used in lengthy operations by having several balloons in store to inflate one at a time each time the batteries are exhausted. The material used to construct these tethers and balloons may be bio-degradable/water soluble. At a predetermined depth the tether between unit and balloon is disconnected at the unit end and the unit again descends nose first charging the remaining batteries. There may be a balloon fixed permanently to the unit and inflated by a stand alone compressed air cartridge for the final accent of sortie or for emergency retrieval. The material used to construct this tether and balloon should not be bio-degradable/ water soluble. Internal and/or external motors can be used alone in navigation or with other "flight control" systems. Internal or external buoyancy compensators can be used.

Claims

1. An electrical generator comprising a cylindrical core coaxially mounted within a hollow cylinder, said core and cylinder having one or more rotor/stator sets disposed thereon, wherein at least one of the core and the cylinder is coupled to one or more impeller(s) which drives rotation of the coupled core/cylinder relative to the other part, characterised in that the generator is adaptable to be driven by different energy sources by replacing one or more impellers with an interchangeable impeller of a different specification.

2. A generator according to claim 1 , which comprises one or more impeller(s) that is/are adapted to rotate when placed in a fluid flow, when subjected to light and/or heat, or when mechanically driven.

3. A generator according to claim 1 , wherein the generator is coaxially mounted within a tubular conduit.

4. A generator according to claim 3, which doubles as an inline pump.

5. A generator according to any of claims 1 to 4, which comprises an interchangeable impeller on one or more of the forward section, the mid section and the aft section of the generator.

6. A generator according to any of claims 1 to 5, wherein one or more of a forward, mid or aft impeller drives rotation of the core.

7. A generator according to any of claims 1 to 5, wherein one or more of a forward, mid or aft impeller drives rotation of the cylinder.

8. A generator according to any of claims 1 to 5, wherein one or more of a forward, mid or aft impeller drives rotation of the core in one direction and one or more other impellers drive rotation of the cylinder in the opposite direction.

9. A generator according to claim 1 , further comprising an interchangeable outer casing.

10. A generator according to claim 3, wherein the conduit containing the generator is sized such that a venturi effect is created within the conduit.

11. A generator according to claim 10, having one or more grooved impellers situated in said venturi.

12. A generator according to any of claims 1 to 11 comprising one or more impellers with golf ball-like pitted surfaces

13. A generator according to any preceding claim, further comprising one or more thermal electric devices to convert the generator's operational heat into electricity.

14. A generator according to any preceding claim, comprising internal mounts which additionally dissipate heat from the generator by conducting it to the atmosphere.

15. A generator according to any preceding claim, which further comprises an air or liquid cooling system comprising tubes extending from the surface of the outer side of the fluid chamber, around the outer casing of the generator and back to the outer side of the fluid chamber through which said air or liquid is drawn and expelled by micro pumps powered by the generator.

16. A generator according to any preceding claim in which the coils and/or magnets are embedded in the core and/or cylinder material, thereby reducing the overall diameter of the generator.

17. A generator according to claim 3, which further comprises an integral draw off valve by which the fluid conduit may be purged of fluid.

18. A generator according to claim 17, further comprising a manually or automatically operated air admittance (anti vac) valve to work in unison with the draw off valve.

19. A generator according to claim 1 comprising a removable outer casing which is adapted to secure one or more mounts, brackets, stands or tripods.

20. A method of generating electricity, in which compressed gas is used to pressurize a fluid through the fluid conduit of one or more generators according to claim 3, thereby causing the impeller to rotate.

21. A method according to claim 20, wherein the compressed gas is from cylinder, cartridge, electronic or mechanical means.

22. A self-contained system for generating electricity according to the method of claim 20, which comprises: i) a top tank (A) which feeds a lower tank (B) containing a generator (S) according to claim 3 via a supply pipe (C) that incorporates an inline strainer (D) and a non return valve (E); ii) a compressed gas supply (L), connected to tank (B) by pipe (H) fitted with a non return valve (I), a mini generator (J) and a pressure regulator (K) which maintains the operating pressure set by compressor/control panel (G); and iii) a return pipe (N) fitted with non return valve (O), a mini generator (P) and an automatic gate valve (M) which allows the pressurised fluid from tank (B) to empty into tank (A) when operating pressure is reached.

23. A system for generating electricity from fluid flow in a pipe, which comprises a ring of generators in a parallel alignment to the pipe work that they encircle and from which they draw their source of flow to create energy.

24. An electrical generator according to claim 1 , further comprising a cone shaped aft section directly connected to the rotor.

25. An electrical generator according to claim 1 , further comprising a cone shaped aft section attached to an aft interface plate of the generator unit.

26. An electrical generator according to any preceding claim, which comprises a sealed generator unit comprising an outer casing, within which the rotor/stator set(s) are held in place fore and aft by internal mounts, said internal mounts being secured to the outer casing by an interlocking ridge and groove arrangement.

27. An electrical generator according to claim 26, wherein the sealed generator unit comprises an outer casing having longitudinal ridges or grooves that cooperate with corresponding grooves or ridges on the internal surface of the tubular conduit to secure the generator unit in place.

28. A generator according to claim 26, wherein the cylinder of the generator, within the outer casing, is divisible into two halves along its length.

29. A generator according to claim 26, wherein the outer casing of the generator is divisible into two halves along its length.

30. A generator according to claim 1 , further comprising mounts that protrude from the fore and aft of the generator and may be secured to the fore and aft sections of the inside of the fluid conduit.

31. A method for generating electricity which comprises placing one or more generators according to claim 1 in a fluid flow.

32. A method for generating electricity which comprises providing a submersible unit comprising one or more generators according to claim 1 , and causing said unit to descend or ascend, whereby fluid flow through the generator(s) as a result of descent or ascent of the unit causes the generator(s) to generate electricity.

33. A method according to claim 32, wherein the ascent/descent of the unit is controlled by means of biodegradable tethers or balloons.

34. A generator substantially as hereinbefore described with reference to and as illustrated by any of Figures 1 , 2 and 3 of the drawings.

35. A self-contained system for generating electricity substantially as hereinbefore described with reference to and as illustrated by Figure 4 of the drawings.