GB2445284A - A hydro-electric generator arrangement for underwater placement - Google Patents

Abstract

A hydro-electric generator arrangement for underwater placement comprises a housing 210, a waterwheel 7 and an electrical generator (not shown), the housing being dome-shaped and containing a volume of trapped gas, which in use, displaces the water in the housing to a level below the axis A of the waterwheel. The trapped gas may be pressurized and pumped from the atmosphere. The submerged arrangement may be placed on the bed of a river to harness tidal currents, and preferably can be rotated for optimum through-flow. The waterwheel may comprise a first set of paddles 30 of a first diameter attached to the hub, and a second set 31 of concentric nested paddles of a second diameter attached to the hub (see fig.6). An independent claim relates to locating the waterwheel within a sub-surface tidal / river / sea current.

Description

Improvements in or relating to Hydro-Electric Schemes

FIELD OF TI IF INVENTION

The present invention relates to hvdro-e]ectric schemes and in particular, but not necessarily restricted thereto, relates to a scheme for converting the energy of tidal and liver currents into electrical energy and more particularly, the present invention relates to a submerged device which may be positioned within a river or tidal current.

BACKGROUND OF THE INVENTION

As the moon orbits around the earth, the gravitational force of the moon and sun pull the oceans creating the tides. It is undoubtedly the most powerful active force on earth.

An immense amount of energy is inherent in these large bodies of moving water. r() harness a small fraction of this cncrg\ and convert it into electricity, many innovative methods have been conceived. When compared with wind energy and solar energy power systems a fundamental problem is that of a total lack of predictability; to date such power supplies only augment the "ordinary" coal fired, oil fired and nuclear power stations. Wave power systems arc equally disadvantaged by the lack of predictable weather. In contrast, tidal systems operate during four distinct periods of flow every day, associated with each tidal phase, each period being followed by an ebb period, when the tidal flow changes direction, with no effective tidal flow. Whilst the ebb periods of tidal s stems may cause local troughs in output of electrical energy, a number of tidal power stations acting in tandem across a region could ameliorate such troughs in supply; river current flow may also be employed to assist in such hydro-electric schemes.

Whilst it is well known that tidal currents can indeed be used to reliably generate electrical energy, the cost of generation can bc prohibitively expensive, the initial capital cost of the structure and the manoeuvring of the structure to a desired location where it can remain, relatively maintenance free in extreme conditions; tidal currents, sea swell, low temperature, marine growth and the like all contribute to conditions where reliability must he high and ease of conducting even minimal maintenance must be good.

The net energy in a tidal stream can he vei' large. When a tidal stream is restricted, for example, between two land masses, the flow velocity can be increased considerably, condensing the net energy through the constricting points of land. l'o extract a 1-IETBOIO7 28 12 2007 significant amount of energy from this relatively slow moving body of water, a large cross-section of the tidal stream needs to be harnessed. In addition to tidal currents, prevailing sea and OCCfl Currents also exist.

Water turbines have been used in many applications, where there is a constant predictable head of generating high velocity water. Highly efficient designs have become available. Turbines, by the nature of their configuration arc limited as to the depth of water the' can operate by the rotor diameter. I ugh currents are experienced in shallow water and arc correspondingly much lower in deeper water. A turbine is most efficient at a specific water speed. If the velocity changes, the efficiency falls dramatically. This is not the case for a waterwheel which maintains its efficiency over a much wider range of flow rates. The velocity of water entering a turbine may not be uniform over the area of rotation and maximum inefficiency would result. Waterwheels do not, in contrast suffer from this problem. Systems using electromechanical generators driven by propeller-type devices have been used albeit not very successfully -the area subjected to the force of the current is limited, as is the amount of electrical energy generated relative to the capital investment. A propeller-type device is fundamentally a high speed device and is unsuitable for low flow speed applications, due to their small turbine apertures.

A simple method of harnessing the energy due to a mass of flowing water is through the USC of a large paddle wheel. However, if a paddle wheel were to he totally submerged within the water it cannot operate since any current would act substantially equally above and below a rotational axis lying in a horizontal plane. Furthermore, in operation a paddle wheel depends upon, amongst other factors: i) the speed of the water and thereby the forces acting upon each paddle; ii) the net effect of the speed of the water acting upon each paddle; iii) the angular spacing of the paddles; iv) the distance of the paddle axis to the level of the water as it passes through the waterwheel arrangement. From another aspect, for a given current flow of constant velocity, the relative speed of the different areas of the paddle will be different and vary as a function of the radial distance of the paddle part with respect to the hub. The different speeds of the water with respect to the paddle causes turbulence, which reduces the efficiency of the waterwheel.

Typical waterwheels have a relatively large distance between the huh and the paddle compared with the height of the paddle and as a consequence, are of a large diameter in relation to the area of flow from which energy is converted.

HEIBO1O7 28 12 2007 Of furthcr consideration is that the maximum torque for each paddle is realised where it pros ides maximum resistance to flow. In comparison, at the point of entry of a paddle to the water thc vector direction of thc paddle is not the same as the current flow and, of course, efficiency is low. The paddle blades are not coterminous with the hub A still further consideration is that as the paddles are raised Out of the water further drag is caused, which reduces overall efficiency. Due to these factors, the energy extracted from a current flow need not be proportional to the size of the paddle wheel.

For a paddle wheel to operate efficiently, only the lower half of the wheel should be submerged below the surface of the water. It is known from many existing designs that a paddle wheel which has an axis of rotation above, for example, a tiowing river then the paddle wheel comprises a series of paddles which arc fixed rclativc to a huh which is mounted about an axis for rotation. Each paddle, in use, is successively dipped in the water flow, which flow causes the wheel to rotate. The conventional undershot wheel uses the kinetic and potential energy of the water, but to harness such energy efficiently there should be little variation in the distance from the water level to the axis of rotation.

The paddle wheel structure needs also to contend with surface conditions such as floating debris and slab ice -in cold environments.

1'he original and simplest method of harnessing tidal power was a barrage and paddle wheel. Subsequently, many intricate methods using different systems have been devised.

In recent years, barrage of coastal waters has elicited considerable public opposition.

Barrage restricts recreational activities and commercial traffic. Due to the growing opposition, the focus of harnessing tidal power has shifted to tidal streams and non-coastal barrage systems. lhis shift has introduced new challenges and obstacles, as tidal streams are generally found in deeper and more treacherous waters. Structures built at such locations are susceptible to ocean storms, slab ice and icebergs. There have been systems developed to harness tidal streams in icc-free locations that arc relativel sheltered. Unfortunately, no arrangement capable of withstanding the environmental forces ()! icebergs, slab ice and severe ocean storm waves has become available.

Certain types of structure sucb as those with caissons, are difficult to transport from a port off origin to a destination placement area. The costs of the placement of such structures can he considerable, with a requirement to hire a pair of support boats and associated lifting paraphernalia, which would be required, typically for a couple of weeks.

HEIBOIO7 28 12 2007 It is known in the undersea industry, for example, in the securing of oil platforms that templates are emplo\ ed whereby drilling into rock on the seabed is performed with control and power systems on board support ships situated at the sea surface. As will be appreciated these tcchnic1ues are expensive and employ large vessels with sophisticated positioning systems. The installation of devices to harness the energy in river and tidal currents, poses considerable difficulties; the expcnsivc systems used offshore are not necessarily possible in areas where, for example, the draft of support vessels is too great for the inshore situations favoured.

US4,717,831, (Kikuchi) discloses a power generator, which generator provides a pluralit) of paddle wheels fixed m place. Since the paddles are essentially immovable with respect to a hub and exposed without any coverage from debris, the Kikuchi system would be vulnerable to damage if used in many environments. I1S5,440,1 75, (Mayo, Jr.

et al.) discloses a river bridge electrical generator unit. This unit is for barrage and thus does not overcome the limitations outlined in the discussion herein previously.

US6759757 addresses the issue of strength and ability to withstand ice masses in frozen conditions and water flows which carry ice blocks. Such structures need to be substantial and to this end a concrete caisson device is provided. The caisson is posmoned such that it will be permanenth aligned with a predominant water flow -as would be expected in a river, hut efficiency is reduced as current direction deviates from the perceived normal direction. In coastal areas, for example, this could be significant; furthermore, if a caisson is situated within a tidal channel, then it would prove to be a significant problem to boats and ships.

W02007053824 Provides a tethered, relatively buoyant main housing having an air chamber with an open bottom, and a paddlewbeel rotatablv mounted therein with an upper portion of the paddlewheel being enclosed by an air chamber and the paddlewheel is operable to generate kinetic energy. An anchor is attached to the main housing, and an electrical generator which converts the kinetic energy of tile paddlcwhccl into electrical energy is coupled to the paddlewheel. When the main housing is submerged underwater and maintained in a level orientation, air within the air chamber remains trapped within the air chamber, thereby reducing resistance to rotation of the paddlewhecl. 1-lowever, in use, the generator is connected to the seabed: as the current increases m strength, then the tethers become increasingly displaced with respect to the vertical allowing the entire structure to become more submerged thereby affecting the efficiency of the paddlewbeel; HETBOIO7 28 12 2007

OBJECT TO THE INVENTION

The present invention seeks to address some of the problems encountered by prior art waterwhcel assemblies. In particular the prescnt invention seeks to provide a vaterwhce1 with improved efficiency. A further object to the invention is to provide an assembly for effectively locating a submarine hvdro-clcctric power supply. The present invention also seeks to provide a secure and easily movable base whereby to locate structures/fixtures with respect to the seabed. The present Invention seeks to provide an underwater structure that is lightweight and easily transportable whereby to provide a versatile, durable and relocatable structure to enable econormc posiuonrng of structures and systems operable in conditions where strong river currents or tidal forces affect the structure.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention, there is provided a hydro electric generator arrangement for underwater placement, for deriving electrical energy from a subsurface current flow, the assembly comprising a housing, a waterwheel and an electrical generator, wherein the electrical generator converts kinetic energy into electrical energy and wherein the housing)attaehed to the bed of a watercourse and is dome-shaped to contain a volume of gas whereby, in use, water within the housing is displaced to a level below an axis of the waterwheel.

By providing the structure as a dome-shaped enclosure, t.he arrangement does not rely upon the weight of a large heavy structure such as a concrete caisson and is relatively easily transportable. The enclosure can comprise of a material selected from steel, aluminium, plastics, and glass reinforced plastics. Conveniently, the structure is manufactured from geodesic panes; whereby assembly of a structure can be enabled proximate to the intended location (if the structure, for example on a nearby shore.

Preferabl1, the arrangement is rotatable, whereby optimum current flow through the device can be achieved.

Conveniently, there is supplied a conduit operable to receive gas from a separate supply.

Alternatively or additionally, there is provided a device operable to produce oxygen from the electrical decomposition of water. In a further embodiment a separate store of HEIBO 107 28 12 2007 compressed gas could he ulilised. The conduit could include an electrical cable whereby electrical energ) output from the generator can be stored or utilised remotc1.

The watcrwhcc] can be mechanically connected to the electrical generator. It is preferred that the waierwheel drives an output shaft having a vertical axis, vherehv to drive the armature of an electric generator with the stator of the generator disposed above the waterwheel, whereby to minimise mechanical losses. Conveniently, the stator for the motor is comprised of a number of arcuate plates which are assembled in a laminated fashion and laminate can be installed once the dome structure has been fabricated, these arcuate plates are preferably machined such that they can be simply he fitted together to define a stator with close tolerances whcrcb to provide a high efficiency electrical generator disposed within a circular dome section In accordance with another aspect of the invention, there is provided a waterwheel for USC ifl an arrangement to derive rotational kinetic energy from a flow of water, the waterwheel comprising a first plurality of paddles arranged about a first circumference with respect to an axis of rotation and a second plurality of paddles arranged about a second circumference with respect to the same axis of rotation, the first circumference being greater than the second circumference; wherein the first plurality of paddles each depend from a hub which is operable to rotate about thc axis of rotation via one or more legs: the one or more]cgs defining an aperture between the paddle and the axis of rotation; wherein the second plurality of paddles each depend from a huh which is operable to rotate about the axis of rotation via OflC or more legs and each paddle is operably arranged to rotate within the aperture defined b' the first plurality of paddles, wherebi each paddle is operable to rotate at a circumferential speed corresponding to the water flow speed of the water.

The first and second plurality of paddles are attached to a common shaft via gearing whcrebv the first and second sets of paddles can travel at a speed approaching the speed of the water current in the flow volume associated with each set of paddles; each set of paddles rotating at different speeds, the gearing enabling the optimisation of relative paddle velocity to the water velocity for each paddle wheel assembly to maximise efficienc for a particular set of conditions.

1-TEIBOIO7 28 12 2007 Thus, for a given area through which there is a tidal or river current, the ability of a waterwhecl to have sets of paddles operable to he rotated at speeds generally corresponding to the actual flow speed of the water, enables the watcrwhcel to operate more efficiently.

There can be provided a further plurality of paddles arranged to rotate about a further circumferences with respect to the same axis of rotation.

In accordance with a further aspect of the iflvenion, the arrangement includes a waterwhcel paddle operable to rotate about an axis of rotation about a hub, wherein the paddles each have a proximal end and a distal end with respect to the hub, the paddles comprising two parts connected via a pivot; the jDlvot having a pivot axis parallel with the axis of rotation of the watcrwhccl, wherein the pivot has a stop operable to limit the extent of movement at a first limit position when subject to forces arising from water flow, whereby, in use, each paddle is operable to pivot to a second limit position as it is removed from the water flow, to reduce turbulence; the arrangement further assisting the efficiency of the warerwhcel as the paddle approaches the surface of the water the distal paddle section is raised slightly by forces due to the water current acting upon a first paddle face until the paddle abuts against a stop to limit further pivot movement until, as the paddle unit is lowered still further, there conies a point where the forces acting on the second paddle face are greater than the forces acting upon the first paddle face whereby the distal paddle section pivots about the pivot clement until the first stop is abutted against and the whereby maximum use of the forces by the current can be utilised to advantage. Further, as the paddle enters the water, the distal paddle section deflects the current so as to impinge upon the adjacent paddle already in the water.

In accordance with a still further aspect to the invention, there is provided a method of usc of the watcrwheel, comprising the step of locating the waterwheel within a sub surface tidal, river or sea current, providing the enclosure with gaseous atmosphere whereby to enable the waterwheel to operate as an undercurrent waterwheel and generating electricity therefrom.

BRIEF DESCRIPTION oF TIlE 1)1WINGS

HEIBOIO7 28 12 2007 For a better understanding of the present invention, reference will now be made, by way ()f example only, to the Figures as shown m the accompansing drawing sheets, wherein:-Figure 1 shows a sectional view of an underwater installation in accordancc with the invention; Figure 2 shows a part plan view of an underwater installation shown in Figure 1; Figure 3 is a view of the waterwheel shown in Figure 1 rotated through 90; Figure 4 is a perspective view of an electrical generator in accordance with one aspect of the invention; Figure 5 shows a further embodiment with paddles of differing depth being mounted abut a common axis; Figure 6 is a partial view of one set of nested paddles of Figure 5; Figures 7 detail how paddles of a nested paddle waterwheel can be connected to a common output shaft; Figure 8 a, h & c detail a pivotal paddle; Figure 9 shows an attachment point in accordance with another aspect of the invention; and, Figure 10 shows the attachment component in plan view; Figure 11, shows a simple directly connected motor-waterwheel arrangement; Figure 12 shows an implementation of the embodiment shown in Figure 11; and, Figure 1 3 shows a group of waterwheels mounted for rotation.

DETAILED DESCRIPTION OF THE INVENTION

in order to provide a better understanding of the present invention an embodiment of the invention will now be described. It will be apparent, however, to one skilled in the art, that the present invention mar be practised without these specific details. This should not he construed to limit the present invention, but should he viewed merely as an HEIBOIO7 28 12 20()7 example of a specific way in which the invention can be implemented. Well known features have not been described in dctail So as not to obscure the present invention.

Referring now to Figure 1, there is shown an enclosure I 0() suitable for fitmeni of a waterwheel arrangement in accordance with the invention, as viewed from a position forward of the waterwheel towards a flow inlet. The enclosure comprises a gas-and water-tight dome structure 102 which is adapted to overlie a waterwhcel arrangement 104, the enclosure being such that it encloses a volume of gas; the gas is convenientl air or oxygen being the result of the electrolytic decomposition of water, is at a pressure corresponding to the depth of water in which ii. is situated, which gas is replenished to take into account losses due to changes in pressure with tide, and loss over time due to absorption by unsaturated water. The size of the enclosure can he as much as 20m in diameter or more; the height can he as much as 8 meters or more. The dome structure -the shape being such that undersea pressures can be tolerated whilst the structure does not present a significant barrier to the flow o the air is provided at a level whereby to enable the waterwheel 104 to operate as an under-current watcrwheel, such that the paddles of the waterwheel can enter the water at a level below the axis of rotation of thc waterwheel. l'he axis of rotation of the waterwhe.el A is indicated. An atmosphere suitable for a watcrwheel without the necessity of compensating for the drag of the watcrwhccls against a water current on a "return stroke" is thereby provided. Duct:ing elements 119 comprising a circumferential brim about the dome assist in directing current flow through the waterwhcel enclosure 102. Optionally, there arc provided walls of a channel (not shown) which define a conduit for the flow of a tidal or river current through a lower section of the enclosure, with a floor preferably being provided. Screed and rock fill (not shown) ma' be provided on the floor for this purpose. This can reduce turbulence and thus increase efficiency of the enclosure. Alternatively or additionally, the sidcwalls may comprise polymeric sheets depending down in a skirt- like fashion, which may assist in reducing dispcrsion of gas as a result of paddle action, whereby gas can be returned to the chamber. Other types of sheet materials may also he used.

The profi]c of the structure 102 is such that it presents a svmmeti-ical resistance to the flow of water -this is especially important during anchoring of the structure, whereby it can maintain its location for the time necessary to attach it to the seabed where a functional structure 1)ccause of its size and profile may not otherwise l)C capable of being fixed without being tethered. The external structure, also referred to herein as a dome HLIBO1O7 28 12 2007 11) can be fabricated from relatively lightweight materials such as steel or aluminium plate or glass reinforced plastics. This is of considerable advantage hcn the structure is transported: fewer and sma]lcr vessels would be required to transport such a structure. It may also be possible to airlift by helicopter such a structure. Inside the structure. it would be possible to have accommodation/ safety / workshop/ stores deck for maintenance crew and equipment; indeed living accommodation could he provided. Typically, the maintenance staff would have their own breathing apparatus, since the air within the compartment could well be stale within a short period of time, although torced induction of fresh air may well ameliorate this problem. Whilst the dome is strong, by creating the dome from strong lightweight materials, the dome would be expected to able to flex to a certain extent, responsive to current forces and differences in water pressure arising from a change in the tide etc..

A preferred form of construction is one which employs geodesic principles where part-spherical structural components, based on a network of struts arranged on great circles (geodesics) lying approximately on the surface of a spherical element. The geodesic panels conveniently comprise planar sheets which arc connected together to form elements that have local rigidity and yet also distribute the stress across the entire structure. Such structures benefit from the feature that it becomes proportionally stronger as it increases in size; a geodesic dome provides a high ratio of enclosed volume to weight. Geodesic domes are far stronger as complete units than the individual struts would suggest. It is preferred that the panels are substantially flat, whereby they are relatively easily manufactured and transported. For example, they can he transported to a shore proximate an area of intended deployment of the structure; the dome ma' be fabricated from the panels between low and high water levels; as the tide rises, once constructed, the structure can be moved with the aid of bouyancy tanks / clcvices. As will be appreciated, quick and simple erection of the dome can provide significant cost advantages in installation of sub-sea structures. By constructing the panels from steel, which is subsequently galvanized or electroplated, a large galvanized or electroplated structure can he provided reducing the need for costly materials and elaborate corrosion protection. Initial bolting of section together and then welding and sealing is an option.

With reference to Figure 2, the waterwheel and generator are shown convenienti mounted upon a chassis whereby they rotate within the enclosure, so that the waterwheel can face the flow of current; a vane or rudder 116 being provided. The waterwheels can HLIBOIO7 28 12 2007 he mounted on a chassis comprising a basic cross-like frame having arms 121, 122, 123, 124; Rollers 120 within bogc s or other t\ pc's of bearing surfaces can be provided at the ends of the arms to assist rotation, the co-operating rolling or sliding track 1 25 of the wateiwheel structure 102 lying upon a gantry 108 supported by spars 112, which are attached to a base 110. As will be known to the skilled man there arc several ways of enabling a rotatable support. The watcrwheels may be moved in combination with a anc; motors, hydraulic or otherwise may be used; a vane could be uSed as a feedback control arrangement, whereby movement of the vane causes switching means to be actuated and thus motors to operated, whereby to enable the waterwheel to be optimally positioned in a water current. It is preferred that only the waterwhccls/generator unit is rotated, hut it is possible to enable the whole structure to rotate, but this would probably not be particularly beneficial in terms of overall efficiency, taking into account maintenance.

The cover of the structure 102 is supported by a series of struts 112 and which support the gantry rmg 108 upon which the rollers rotate and which enable the watcrwheel and its support to be rotated. Preferably support member 123 has a vane 116 depending therefrom. The vane structure can assist in movement of the device, conveniently with electric motor assistance, as described above.

Figure 3 shows a perspective schematic representation of the watcrwheel assembly of the first embodiment. The output power of the waterwheel is provided by a rotation of an output shaft rotating about a horizontal axis A; a crown wheel assembly can translate the rotational movement about a horizontal axis to rotational motion of spindle 43 about a vertical axis VA. Suitable gearing can he provided tO) reduce or increase the rotational speed of the spindle. hilst the paddlewheel can be mechanically connected to and operable to drive am' form of electrical generator, such as a dynamo or alternator, within the dome enclosure 102, it is preferred that a custom arrangement is utilised. Spindle 43 drives armature 45 with magnetic pole pieces 46 about stator elements 44 to provide a simple yet efficient electrical current generating means. The diameter of the armature is large, being about 2 -10 metres, enabling relatively low armature revolutions per minute to provide high pole piece speeds, whereby to induce current in the stator windings. It would be possible to have multi-speed gearmg systems, whereby to enable optimal generator output when tidal flow change occurs, but this could cause unnecessary complication in terms of maintenance and reliability. The stator is conveniently formed HEIBOIO7 28 12 2007 from arcuate poruons which are assembled in situ; they are connected together and freely mounted, remaining relatively immobile due to the considerable weight of the laminar arcuatc stator portions, which arc fixed together as is known to the skilled man. Prior to the fitting of pole pieces of the armatures, theinside face of the stator can he pmgressivelv skimmed by mean of a cutting tool that is attached to the armature. The cutting tool is adjusted so that a uniformly circular aperture is defined by the stator; after completion of the skimming, the pole pieces are attached to the armature. Due to the fine tolerances achievable, the gap G is very small and allows a high operating efficiency of a resultant electrical generator to be obtained. The stator can be wound with wire to give a variety of electrical outputs to match the power a ailable from the waterwheel and corresponding to its speed of rotation.

The length of the legs 1 1 supporting the waterwheel arrangement 102 can be of variable lengths, so as to enable the arrangement to be positioned in water providing maximum current. Figure 4 shows a second ernhodliment wherein the length, L, of the legs allow the enclosure 102 to he positioned several meters above a floor of a watercourse. l'he legs will l)e manufactured to provide sufficient support, as will be known to those skilled in the art, and bracing means, lattice type elements and the like may he used. It will also be appreciated that the operational length of the legs could be varied in certain embodiments, where it is appropriate to do SO, for example, where there is a high tidal fall and the water current strength differs significantly over a few metres. In this Figure, the axis of rotation of the waterwheel A is perpendicular to the plane of cross-section.

An inlet orifice can he determined by converging boards (not shown), which assist in direcftng water current through the structure by circumferenriallv peripheral upper and lower lips 119 of the dome enclosure so that the how of the water current is directed towards the waterwheel. Side walls operable to lie closely adjacent the outer edges of the waterwheels, whereby to increase water flow towards the waterwheels may assist the vane or rudder in having the axis of rotation of the watcrwhccls substantially normal to the direction of how. It is to be noted that tidal currents are typically never bi-directional as such; differences in outcrops of rocks, deposits of sand and the like will cause the direction of tidal currents to vary over the course of a change in tide. Rock, sand and other types of ballast may he placed upon the roof of the enclosure; the upper lips serving to retain the ballast, whereby to provide habitat fro wild life and to reduce buoyancy of the enclosure and aid stability of the structure.

HEIBO1O7 28 12 2007 The level of water within the enclosure is indicated at w/1, just below the rotational axis of the watcrwheel. l'he preferred level of the waterline will var', dcpcndcnt upon the type of waterwheel employed. As will be apprcciatcd, thc flow of the water current acts against the paddles of the watervheel in one direction only: Above the surface of the water, the waterwhccl paddles arc relatively unhindered in moving above the water level.

After passing through the paddles of the waterwheel, the water current tiows via an outlet, opposite the miet-. A preferred watcrwheel will be described below, which, especially with multiple units and preferably pivotal paddles (either in whole or in part), can enable the size of the structure to be reduced, whereby to be more economically produced and more simply be placed at the bed of a watercourse. This is important for economic reasons as the capital costs have to be repaid from the energy generated and sold. This presents a major problem with known systems.

Pressurised gas, conveniently air, is maintained within the enclosure -a cord 28 (also referred to within the industry as an umbilical) allowing flow of electricity to a surface based elcctncal energy processing or store arrangement, which can also transport air to and from the enc]osure. Compressors within the dome can store the air within the dome as the external pressure falls and releases it again as the pressure rises, for example during the rise of a tide. The umbilical will also enable control cables to be provided. Given that the height of water above the structure can var)' to a large extent in some tidal flows, therefore the pressure of the gas will also vary. This will have the effect that expansion of the gas will lead to a loss of such gas, which will therefore need to be replaced. Gas cou]d be stored in bottles or pumped from the atmosphere, via an umbilical. Gas could he produced b' clectrolyc decomposition of the water, but this is not favoured since hydrogen would be evolved, which is explosive under certain conditions.

In certain circumstance, where the current flow direction is uni-or bi-directional, it may be appropriate to have a barrage system, whereby water is urged toward the waterwhcel.

For certain applications, the structure may have other structures or features built or placed upon them. In shallow waters, islands may be created by placing rocks and soil and other features. These may he able to withstand currents and ma)' actively assist in the directing of currents towards the waterwhecl. The circumferential brim 1 9 may be provided to an overall dome or dome-like structure to assist in the retention of such features.

HEIBO 107 28 12 2007 Referring now to Figure 5, there is depicted a watcnhee1 20 rotatable about an axis A comprising three watcrwhcels 22, 23 & 24, each having eight paddles. In essence, the paddles, as viewed from an incoming water current perspective comprise ncstcd paddies, and as depicted in Figure 6; an outermost paddle 30 depending from the axis A to a lower channel wall of the waterwhcel housing is connected to a hub 26 about the axis 21; a middle paddle 31, again depending from a hub 27 about the axis 21 to the uppermost part of paddle 30; an innermost paddle 32, depending from hub portion 28 about the axis A to the uppermost part of the middle paddle. B having the three paddles connected to a common axis, through suitable gearing, the different waterwbeels can rotate at different speeds relative to each other yet all contribute to rotation of a single output shaft. Whilst the flow of water current through the waicrwhecl should be similar in cross-section, it will be realised, that the entry of paddles into the water will affect water flow SO that the extra turbulence will reduce current flow to an extent. I Jowever, suitable reduction in gearing will enable the innermost paddlewhccl to operate at a faster speed of rotation. It will be realised that the paddles must be shaped and dimensioned so as to allow passage of the moving paddles, one with respect to the other and to the channel defined by the structure so that foreign bodies such as fish, seaweed, small stones and the like do not prevent movement. It should also be mentioned that the tolerances and the more gentle movement of waterwheels means that fish and other sea life arc less likely to he shredded or get stuck in a paddle wheel than is the case of a precision turbine with small clearances. It wi]l he appreciated that the arms 33, 34, 35 which support the paddles 30, 31, 32 and depend from the hubs 26, 27, 28 are preferably shaped and have re]cvant clearances to reduce turbulence generally and also with respect to the other arms, which will he rotating at different speeds. The shape of the paddles need not necessarily be generally rectiplanar plates and may be generally cupped, to maximise efficiency. Each paddle 30, 31, 32 may be fitted with a pivotal paddle or paddle section as described in relation to Figure 8 below, as denoted by reference numerals 14.

Details of the specific electrical generators are not given but, in recent years, there has been a significant development of static inverters to match outputs to enable energy to he supplied to the national grid electricity network generators for wind di-iven impellors, which can be simply adapted for use with water current driven generators.

In order to maximise transfer of kinetic energy from the water flow, the paddles will travel at a speed less than the speed of the water current, since water flow energy is HLIBOIO7 28 12 2007 converted into rotational energy of the waterwheel, the smaller paddles will operate at a greater rotational speed relative to the outermost paddle. With reference to Figure 7 there is shown a section through a hub, along the rotational axis thereof, where the hub sleeve. 39 is particularly referenced and is arranged for rotation via gearing with respect to the axis A. With particular reference to paddle 38, arm 39 located with sleeve 39, which in turn drives via gear teeth 411 a further cog 41 fixcdl keyed with respect to an Output shaft 42. 1'he other paddles arc similaris' coupled to the output shaft via their respective sleeve, and gear-cogs. The gear assembly is arranged so as to output the rotational kinetic energy, together with a corresponding output shaft from the second watcrwheel arrangement and via a crown wheel or similar transfer the direction of rotation from a hori.',ontal axis to a vertical axis.

The other sleeves will be arranged with different gearing -to take into account the differences in rotational peed and current flow within a conduit defined by the structure whereby the rotational speed of an output shaft is optimal for the arrangement. As will be appreciated, all cogs will be mounted on suitable bearings, not shown; the hubs also will have waterproof seals, also not shown, with pressure compensation as appropriate, to prevent entry of water into the bearing assemblies. As will he appreciated, this aspect of the invention ma\ be arranged such that there can be two or more nested paddles in a system, the number of thc sets of paddles that may be utilised being dependent upon 2() application.

Figures 8 a -8c show a preferred type of paddle to he used with the preferred multi-watcrwheel arrangement, the paddle is pivotally connected to Support arm at either side and has a range of movement suitable to enable a minimal amount of turbulence as the paddle enters the water and is removed therefrom. in particular, the paddle 14 is pivotally connected with the support arms 16 to provide limited angular movement of the paddle 14 with respect to the arm, about an axis which is generally parallel to the axis A of the watcnvhecl arrangement. The range of angular movement is limited by stop 21 and variable stop 18 (conveniently shown as a screw threaded stop or bolt), the stop elements being mounted on stop section 17 of the arm. With reference to Figure 8h it can be seen that as the paddle 14 approaches due to the paddles being rotated in a rotational direction R the surface of the water as indicated by reference w/l, the waterline, the paddle is raised slightly b' forces due t() the water current 8 acting upon paddle face 14a, until the paddle abuts against stop 18 -this reduces turbulence; as the HEIBO 107 28 12 2007 paddle unit 14 is lowered still further, there comes a point where the forces acting on paddle face 14b are greater than the forces acting upon face 14a, whereby the paddle SeCtiOn 14 pivots about stop clement 17 whereby maximum usc of the forces by the current can he utilised to advantage, as depicted in Figure 8c, with abutment portion 14c of paddle 14 abutting against stop 21 of stop element 17. Whilst in the mid-position, the paddle entering the water is preferably shaped SO as to direct water towards the adjacent downwardh directed paddle, already fulls' immersed. l)arnping means ma be fitted to the stops to provide progressively resistive load bearing stops, to cushion abutment forces, as the paddle flips from one position to another. The paddle may comprise a first section fixed to the arm with a distal section pivotallv connected to the arm, the pivotally arrange paddle section being moveabic as described above, where there is no paddle section fixed to the arm.

It is known in the undersea industry, for example, in the securing of oil platforms that templates are employed whereby cliilling into rock on the seabed is performed with control and power svsl-ems being situated at the sea surface. As will be appreciated these techniques are expensive and employ large vessels with sophisticated positioning systems.

The installation of devices to harness the energy in river and tidal currents, poses considerable difficulties; the expensive systems used offshore arc not necessarily possible in areas where the expense and possibly the draft of support vessels is too great for the inshore situations favoured. The installation of a structure in accordance with the present invention also reduces the environmental impact caused by any construction traffic with consequential damage to the sea floor, fish, molluscs, crustaceans etc. In accordance with another aspect of the invention, there is provided a remotely controlled attachment and levelling device for the positioning of structures to harness tidal power etc., the structure comprising a ring (commonly referred to as a template in the industry) or other structure of preferably uniform in cross section and upon which an underwater device, hereinafter referred to as a remotely controlled attachment and levelling device, is to be mounted and to be operated during installation of the template.

The remotely controlled attachment and levelling device is attached during slack water.

This is time consuming hut can be performed in high current conditions at low cost, by, for example, a few engineers based on the shore in a temporary shelter such as a container based workshop facility. This is in contrast to the use of support ships and the like which operate freely piloted mini-subs to enable placement of known templates.

HEIBOIO7 28 12 2007 The mass of the structure must he sufficient whereby, in conjunction with anchors if appropriate, it can withstand currents and sea swell whilst the structure is being attached to the seafloor/bed of the watercourse. Whilst remotely controlled vehicles can be employed certain circumstances may dictate that such remotely controlled vehicles cannot operate in such conditions or it may he simpler / preferable that this is so. Note also that divers rna' operate in groups to enable anchoring procedures to he accomplished and generally assist, but again may not he capable of assisting in certain conditions. For example, in areas of high current, it will be appreciated that the deployment of divers can he quite dangerous and/or not possible. It is preferred that that the levelling and securing process is remotely controlled and the vehicle powered and supplied with necessary fluids from a remote location, either being a boat or land using a control line (umbilical). once a template has been constructed, especially where there is significant current a preferred method of attaching a device to the template would be through the use an anchor -positioned upstream relative to the template; a cable would be passed from the surface to the anchor and then to the body to be positioned. The cable would pass through the anchor, conveniently by means of a pulley; and the structure would be urged against the current flow; as the buoyancy of the structure is reduced as gas is released from flotation dcviccs or otherwise, the structure would lower itself', remotely operated vehicles can he controlled to do this with or, preferably, without diver support.

The process of attaching the template or ring requires pins 60 to hc inserted through the ring; the pins act against the ring and arc moved downwardly and adjusted such that they can level the ring. The pins conveniently comprise a screw threaded bolt; typically three will be used, but more or less may be used or indeed another method of levelling. Once the base is level, the base is fastened to the sea bed by bolts 62 or other fastening means such as rock bolts and / or dowels. Chemicals may be cmplovcd, such as epoxy adhesive; cement or grout may also he used. Injection drilled anchors such as those sold under the Titan brand may be employed. Such types of bolts comprise steel tube using ferritic-austenitic steels and other micro-alloy structural steels having deep threads. As these types of bolts arc drilled into the rock, grout is pumped through the centre of the drill steel and flushes debris out of the hole, Once at its required length, the drill string is Cut and becomes the anchor bolt. Further bolts are secured thereafter, moving progressively around the circumference of the structure; the total number of bolts that arc required depends on the nature of the bed, the types of anchoring devices, the HEIBOIO7 28 12 2007 expected forces anticipated and the like. Initial bolts placed to secure and level the structure would be approximately 24mm in diameter; other screws, which are placed into rock would he of a greater diamcter, typically 75mm diameter, or more. Those skilled in the art would be able to calculate the number and size of screws to be placed to support the structure, with regard to type of materials employed, the type of rock and the nature of the sea bed.

Referring now to Figure 9, a remoi-el controlled attachment and levelling device 130 is shown attached to a section of the template or attachment structure or ring 110. The remotely controlled attachment and levelling device 130 is capable of travelling around the periphery of the circular attachment structure although its means of propulsion are not shown. The remotely controlled attachment and levelling device is attached temporarily or otherwise to the template to perform levelling and attachment functions.

Conveniently articulated arms would he employed, from a base whereby accurate positioning of tools etc is possible. The remotely controlled attachment and levelling device also comprises a manipulator 132, a drilling/torque head 136 and a tool/component storage arrangement 134. The template could comprise a linear piece, or be of a square/rectangular frame contiguration, hut special wheel and rollers would need to be provided to enable the remotely controlled attachment and levelling device to traverse around right-angle 3unctions and the like, but details such as propulsion means are not shown for simplicity. The vehicle also comprises a manipulator, a drilling and torque head and a tool/component storage rack. The use of a remotely controlled attachment and levelling device enables the template and subsequent functional structure to minimize deployment of personnel, often in inhospitable conditions. ll1e remotel controlled attachment and levelling device may be controlled using acoustic signals.

l'he manipulator 132 can move and rotate as indicated by the arrows and is capable of extracting tools fr in the rack 134, which tools are placed beneath the tool head 134 to rotate and manipulate the tool. Here, the term too] is used broadly to refer to any item required by the tool head whereby to level and secure the template 110 to the bed of any watercourse. An anchorage device 136 is shown passing through the template 110. With reference to Figures 9 & 10, the template has been levelled and attached to the watercourse using levelling pins 60 and securing devices 62, respectively -note, however that only one of each is shown.

HEIBOIO7 28 12 2007 Once the underwater attachment structure is installed, the functional structural device can be installed upon the template or ring relatively quickly, using appropriate means, when conditions permit. As referred to above, when the device to be installed is a power generation unit, the lightness and simplicity of construction of the proposed waterwheel generator will enable the device to be installed quickly an(l safely. The template may compnse a simple linear base whereby a different type of functional structure may be placed securely upon the bed of a water course -for example, the functional structure may comprise a base for a wind powered generator or a barrage system for an underwater current generator system, or the footings for a causeway or bridge etc..

One method of positioning the structure would be to use flotation bags: the device to be installed would he floated by the use of a support vessels; and tethered to a ground anchor against the prevailing current and the device would he lowered, with a remote controlled vehicle or similar whereby, upon de-hallasting of the buoyancy or flotation bags will allow the structure to be sunk in a controlled fashion, using the template as an anchor, the umbiheal ma)' be simply deployed using a winch and be connected. Minimal, diver intervention may be required to assist the process. Where the device attached to the structure is a hydro-electric generator system, it is anticipated that it will generally be placed close to the shore, within a few kilometres of land, in areas where there are likeh to be strong, where tidal / river flow's; accordingly it would be convenient to use remotely piloted vehicles for such installations. It is especially convenient if such servicing can be performed from the shore. Referring again to Figure 9, the waterwheel enclosure 102 comprises a functional structure. The water level within the dome is lowered by introducing air into the dome (or other gas, but air is generally' cheaper to transport, especially' by' way of an umbilical which would be used to enable the electrical power generated to he utilised onshore. I'he current also imposes high forces on such a structure; the energy of a current of the wheel is proportional to the cube of the velocity of the water flow current. It would be very difficult -if not impossible -to install and secure such a structure in areas of high current to the seabed in the time it takes for the tide to turn without the use of a remotely controlled attachment and levelling device as desenbed above -this is different to an RCV -industry parlance for a remote controlled vehicle, being a free-swimming vehicle -which cannot be used in conditions of high current.

1-IEIBO1O7 28 12 2007 The present invenu()n comprising a sea-borne current watenvheel may also provide a base fbr a wind-driven electncit) generator. Advantages of unitary supply lines and simplified/combined maintenance schemes would assist in the deployment and management of such generation schemes.

In an arrangement of waterwheel generators, the generators may he arranged in a row; alternatively, tile)' may he arranged in two rows, the second row being offset/displaced relative to the first row, hereby to maxiniise the use of the current, the second row generators being positioned to take advantage of currents flowing in-between the first row of generators. Other arrangements are possible. With reference to Figures 11, 12 & 13, there is shown, firstly, with reference to Figure II a simple paddlewheel arrangement operable to drive a generator 201 via a gearbox 204, about an axis of rotation A. An umbilical 208 is provided to enable gases to he provided to a waterwheel enclosure whereby to provide a waterwheel enclosure with a water level below the axis of rotation, as seen in Figure 12, where an enclosure 210 is shown, having an inlet 212 operable to allow a current 8 into the waterwheel arrangement.. Figure 13 shows a still further arrangement wherein arrangements corresponding to Figure 12 are mounted upon attachment means 214 of a structure 218 which is mounted for rotation about an upstanding pole of several metres in height and from which one or more buoyant or semi-buoyant watenvheel enclosures are supported: the waterwheel operates such that it has an axis of rotation above a water line within enclosures (although a donle shape, whilst ideal, is not the only configuration possible). An umbilical can be attached via the pole, although since the waterwheel enclosures are free to swing, then each umbilical needs to be formed such that it is resistant to twisting or is adapted to enable operation despite the rotational swinging of the arrangement.

HLIBOIO7 28 12 2007

Claims (17)

1. A hvdro electric generator arrangement for underwater placement, for deriving electrical current from underwater current flow, the assembly comprising a housing, a waterwheel and an electrical generator, wherein the electrical generator converts kinetic energy into electrical energy and wherein the housing is dome-shaped to contain a volume of gas whereby, in use, water within the housing is displaced to a level below an axis of the waterwbeel.

2. An arrangement according to claim I wherein the housing is mounted on the bed of a watercourse.

3. An arrangement according to claim 1 or 2 wherein the arrangement is rotatable, whereby optimum current flo\v through the device can he achieved.

4. An arrangement according to any one of claims 1 -3, wherein there is supplied a conduit operable to receive gas from a separate supply.

5. An arrangement according to any one of claims 1 -3, wherein there is provide a device operable to produce oxygen from the electrical decomposin of water.

6. An arrangement according to claim 3, wherein the conduit operable to provide gas to the housing comprises an electrical cable whereby power output from the generator can be stored or utilised or exported.

7. An arrangement according to any OflC of claims 1 -6 wherein the enclosure is comprised of a material selected from steel, aluminium, plastics, and glass reinforced plastics.

8. An arrangement according to any one of claims 1 -7 wherein the enclosure is of a geodesic construction.

9. An arrangement according to any one of one of claims 1 -8 wherein the watcrwheel is directly connected to the electrical generator.

10. An arrangement according to any one of claims 1 -9, wherein the waterwheel comprises a first plurality of paddles arranged about a first circumference with respect to an axis of rotation and a second plurality of paddles arranged about a second HEIBO 107 28 12 2007 circumference with respect to the same axis of rotation, the first circumference being greater than the second circumference; wherein the first plurality of paddles each depend from a hub which is operable to rotate about the axis of rotation via OflC or more legs: the one or more legs defining an aperwre between the paddle and the axis of rotation; wherein the second plurality of paddles each depend from a huh which is operable to rotate about the axis of rotation via OflC or more legs and each paddle is operably arranged to rotate within the aperture defined by the first plurality of paddles; wherein a gear arrangement is provided to enable the paddles to rotate at optimal wherein the first and second plurality of paddles arc attached to a common shaft via gearing whereby the first and second sets of paddles can travel at a speed approaching the speed of the water current in the flow volume associated with each set of paddles; each set of paddles rotaflng at different speeds, the gearing enabling less turbulence and an increased efficiency of operation.

11. A waterwheel according to claim 1() wherein the first and second plurality of paddles arc attached to a common shaft via gearing whereby the first and second sets of paddles can travel at a speed approaching the speed of the water current in the flow volume associated with each set of paddles; each set of paddles rotating at different speeds, the gearing enabling less turbulence and an increased efficiency of operation.

12. A waierwheel according to claim 10 wherein there is provided a further plurality of paddles arranged to rotate about a third cii-cumfcrcnce with respect to the same axis of rotauon, the second circumference being greater than the third circumference; wherein the second plurality of paddles also define an aperture between the legs from which the paddles depend, the paddle and the axis of rotation; wherein the second plurality of paddles each depend from a hub which is operable to rotate about the axis of rotation via one or more legs and each paddle is operably arranged to rotate within the aperture defined by the first plurality of paddles; wherein the first, second and third plurality of paddles are attached to a common shaft via gearing whereby the first, second and third sets of paddles can travel at a speed approaching the speed of the water current in the flow volume associated with each set HEIBOIO7 28 12 2007 of paddles; each set of paddles rotaung at different speeds, the gearing enabling less turbulence and an increased efficienc) of operation.

13. A watcrwheel according to claim 11) wherein there are one or more further sets of paddles arranged about the inner first to third sets of paddles; wherein further gears are provided to enable all sets of paddles to provide an output via a common shaft.

14. An arrangement according to an one of claims I -9, wherein the waterwheel is arranged so as to be operable to rotate about an axis of rotation about a hub and has a plurality of paddles, wherein each paddle has a proximal end and a distal end with respect to the hub, the paddle comprising two parts connected via a pivot; the pivot having a pivot axis parallel with the axis of rotation of the waterwheel, wherein the pivot has a stop operable to limit the extent of movement at a first limit position when subject to forces arising fn)m water flow, the paddle being operable to pivot to a second limit position as it is removed from the water flow, to reduce turbulence; the arrangement further assisting the efficiency of the waterwheel as the paddle approaches the surface of the water the distal paddle section is raised slightly by forces due to the water current acting upon a first paddle face until the paddle abuts against a stop to limit further pivot movement until, as the paddle unit is lowered still further, there comes a point where the forces acting on the second paddle face are greater than the forces acting upon the first paddle face whereby the distal paddle section pivots about the pivot element until the first stop is abutted against and the whereby maximum use of the fi)rces by the current can be utilised to advantage.

15. A method of use of the waterwheel, comprising the step of locating the watcrwheel within a sub surface tidal, river or sea cuntnt, providing the enclosure with gaseous atmosphere whereby to enable the waterwheel to operate as an undercurrent waterwheel and generating elecrricity therefrom.

16. An apparatus substantially as described herein, with reference to any one or more of the accompanying Figures.

17. The use of any one or more of the above con urations to generate elccwicity, with reference to any one or more of the accompanying Figures.

17. The use of any one or more of the above configurations to generate electricity, with reference to any one or more of the accompanying Figures.

HETBOIO7 28 12 2007 Amendments to the Claims have been filed as follows

1. A hydro electric generator arrangement for underwater placement, for deriving electrical current from underwater current flow, the assembly comprising a housing, a waterwheel and an electrical generator, wherein the electrical generator converts kinetic energy into electrical energy and wherein the housing is dome-shaped to contain a volume of gas whereby, in use, water within the housing is displaced to a level below an axis of the waterwheel.

2. An arrangement according to claim 1 wherein the housing is mounted on the bed of a watercourse.

3. An arrangement according to claim I or 2 wherein the arrangement is rotatable, whereby optimum current flow through the device can be achieved.

4. An arrangement according to any one of claims I -3, wherein there is supplied a conduit operable to receive gas from a separate supply.

5. An arrangement according to any one of cfaims 1 -3, wherein there is provide a device operable to produce oxygen from the electrical decomposition of water.

6. An arrangement according to claim 3, wherein the conduit operable to provide gas to the housing comprises an electrical cable whereby power output from the generator can be stored or utilised or exported.

7. An arrangement according to any one of claims I -6 wherein the enclosure is comprised of a material selected from steel, aluminium, plastics, and glass reinforced plastics.

8. An arrangement according to any one of claims I -7 wherein the enclosure is of a geodesic construction.

9. An arrangement according to any one of one of claims I -8 wherein the watersvheel is directly connected to the electrical generator.

10. An arrangement according to any one of claims 1 -9, wherein the waterwheel comprises a first plurality of paddles arranged about a first circumference with respect to an axis of rotation and a second plurality of paddles arranged about a second / circumference with respect to the same axis of rotation, the first circumference being greater n the second circumference; whetein the first plurality of paddles each depend (roan a hub which is operable to maze about the axis of rotation via one or more legs; the one or more legs defining an aperture between the paddle and the axis of rotation; wherein the second plurality of paddles each depend from a hub which is operable to rotate about the aids of rotation via one or more legs and each paddle is operably arranged to rotate within the aperture defined by the first plurality of paddles; wherein a gear a.ngement Is provided to enable the paddles to rotate at optimal wherein the first and second plurality of paddles are attachcd to a common shaft via gearing whereby the first and second sets of paddles can travel at a speed approaching the speed of the water current in the flow volume associated with each set of paddlea each set of paddles rotating at different speeds, the gearing nibling Lees turbulence and an increed efficiency of operation.

ii. An arrangement according to claIm 10 wherein the first and second plurality of paddles of the waterwhcel are attached to a common shaft via gearing whereby the first and second sets of paddles can travel at a speed approaching the speed of the wirer airrent in the flow volume associated with each set of paddles; each set of paddles wasting at different speeds, the gearing enabling less turbulence and an increased efficiency of operation.

An arrangement according to claim 10 wherein the waterwhcel the is provided with a further plurality of paddles arranged to rotate about a third circumference with respect to the same axis of rotation, the second circumference being greater than the third &cumfcrence; wherein the second plurality of paddles also define an aperture between the legs from which the paddles depend, the peddle and the axis of rotation; wherein the second plurality of paddles each depend from a hub which is operable to rotateaboutdmaxiaofronviaoneormorelrgsandeacbpaddlcisoptxably arranged to rotate within the aperture defined by the first plurality of paddles; wherein the first, second and third plurality of paddles are attached to a common shaft via gearing whereby the firs; second and third sets of paddles can travel at a speed approaching the speed of the waist current in the flow volume associated with each set of paddles; each set of paddles rotating at different speeds, the g.-i.4rg enabling lcs tuzbulet and an increased efficiency of operation.

13. An arrangement according to claim 10 wherein the waterwheel is provided with one or more further sete of paddles arranged about the inner ant to third sete of parkiles; wherein further gears are provided to enable all vets of paddles to provide an output via a common shaft 14. An arrangement according to any one of cWmi 1 -9, wherein the waterwheel is arranged so as to be operable tio rotate about an axis of rotation about a hub and has a plurality of paddles, wherein each paddle has a proximal end and a disl end with respect to the btth, the paddle comprising two parts connected via a pivot; the pivot having a pivot axs parallel with the axis of rotation of the waterwheel wherein the pivot has a stop operable to limit tha extent of movement at a first limit position when subject to forces arising from water flow, the paddle being operable to pivot to a second limit position salt removed from the warer flaw, to rcducc wrbulencç the wangeroent further assisting the eEciency of the watexwhcel as the paddle approaches the surace of the water the distal paddle section is raised slightly by forces due to the water current acthig upon a first paddle face until the paddle abuts against a stop to limit further pivot movement until, as the paddle unit is lowered still further, there comes a point where the forces acting an the second paddle face are greater than the forces acting upon the first piddle face whereby the distal paddle section pivois about the pivot element until the first stop is abutted against and the whereby maximum use of the fortes by the current can be utilised to advantage.

15. A method of use of the arrangement according to anyone of thinis I -14, comprising the steps of locating the arrangement within a sub surface tidal, river or sea current, providing the enclosure with gaseous atmosphere whereby to enable the waterwheel to operate as an undercurrent wtterwheel arid generating electricity thereftow 16. An appsraD.ss substantially as described herein, with reference to any one ox more of the accompanying F*gures.