AU2013212537A1 - A variable output generator and water turbine - Google Patents

Abstract

A water turbine for electric power generation, said water turbine comprising (a) a body having an internal cavity for housing a variable output generator, said body being rotatable about a central shaft; and (b) one or more turbine blades being adapted to engage an axial flow of water, said one or more turbine blades extending from a leading end of said body in one or more of (i) a substantially helical configuration; and (ii) a downstream direction relative to said leading end, wherein in use, said one or more turbine blades channel said flow of liquid about said body such that said body is caused to rotate about said central shaft.

Description

WO 2013/110140 PCT/AU2013/000068 1 A VARIABLE OUTPUT GENERATOR AND WATER TURBINE Field of the invention [0001] The invention relates generally to a water turbine and, in particular, to a water turbine for electric power generation. The invention is particularly useful in relation to water turbines positioned in naturally occurring current flows such as, for example, in rivers and oceans, however, it should be understood that the invention is intended for broader application and use. Background of the invention [0002] In an ever-changing world dependant on fossil fuels, there is a huge demand for alternative, cheaper, plentiful and sustainable energy supplies to be obtained from the world around us. Water currents are found all over the globe, being mainly surface ocean currents, deep ocean currents, tidal currents and river currents. Ocean currents are essentially large area stationary currents that are continuous and sustainable in their nature, caused by winds, salinity or temperature differences in adjacent parts of an ocean. Water at the ocean surface is moved primarily by winds that blow in certain patterns due to the rotation of the earth, otherwise known as the Coriolis Effect. Winds are able to move the top 400m of an ocean, creating surface currents. These winds form large surface patterns known as 'gyres' that rotate clockwise in the Northern Hemisphere and counter clockwise in the Southern Hemisphere. [0003] There are many and varied surface currents, as well as equatorial and global sub currents, that range in velocities up to about 2.5m/s, and at depths ranging from the surface to 400m and deeper. The Northern Atlantic Gyre or Gulf Steam, for example, is a surface current in the North Atlantic Ocean that carries around ninety million cubic meters of water per second. [0004] Tidal ocean currents are determined by the rise and fall of the sea level due to the combined forces of the moon and the sun, and the rotation of the earth. Most places in the ocean usually experience two high tides and two low tides per day (semi diurnal tide), although certain places experience only one high tide and one low tide per day (diurnal tide). The times and amplitudes of these tides vary depending on location, alignment of the moon and the sun, patterns of tides in the ocean, bathymetry, time of year and coastal typography. They can rise well over 11 meters, with peak current flow velocities that can exceed 7m/s.

WO 2013/110140 PCT/AU2013/000068 2 [0005] Tidal currents have a major drawback in that for a large part of the tidal cycle the tide is ebbing or turning. At one point in the cycle of the tide the current flows in one direction, whereas at another point of the cycle it flows in the opposite direction, and in between it flows at its slowest. This presents a variety of problems in efficiently extracting energy. [0006] Tidal current energy can be extracted by two means; by building dams that release water through a turbine, or by placing a water turbine within an existing current. The potentially available energy is determined entirely by the magnitude of the current. However, often the strongest and best tidal currents are often limited or unavailable due to shipping or coastal restrictions, or for other environmental reasons. Since the energy available from a current flow is proportional to the cube of the flow speed, the times during which satisfactory power generation is possible are limited. Whilst some power generation may be possible for the majority of the tidal cycle, in practice, most turbines lose their efficiency at lower operating speeds. [0007] On land, river currents are typically uni-directional, with flows and water levels being seasonally variable. Larger rivers are relatively deep and contain substantial flows ranging in speeds of up to (and above) 3.5m/s, and can easily be accessed. Current energy extraction and generation is often facilitated via the construction of dams and the placement of low-head turbines within them. The drawback of this technology is that large dam walls must be built, with water falling from a height and in vast quantities, often with environmental consequences. Using river currents for energy generation, for example, to power pumps for irrigation purposes in more remote areas, has however been less practical and is relatively unknown. The agriculture and farming industries have mainly relied on expensive, manually transported diesel powered equipment or by the cabling of remote electrical grids. [0008] Water turbines have been used for centuries to pump water, or to power a wide range of devices. Over the past century they have become an increasingly important means of energy generation. Water turbines are generally considered a clean energy producer, as the turbine essentially causes no change to the water. Marine currents in particular have been identified as a key contributor to sustainable energy because the energy harvest and the time of occurrence can be predicted in advance. Marine currents are also reliable, sustainable and predictable. [0009] In recent years there has been considerable effort expended to improve the efficiency of water turbines, with a view to lower dependence on fossil fuels and raise the level of consumption of sustainable energy sources. The expansion of existent power-generating WO 2013/110140 PCT/AU2013/000068 3 technology is dependent on significant advances in the contemporary models presently deployed in our rivers and oceans. There are many unexplored prime sites, having high mean energy flows but which have previously been out of reach of existing technology. [0010] Research and advancement of water turbine technology have been actively encouraged by governments around the world including Europe and the United States. Typically these strategies involve the development of large turbines with larger rotors designed to capture more energy by interacting with a broader area of the current flow. They also employ complicated gearing and bulky generators that are often not suited to the extreme conditions of complex marine environments. [0011] Modem technological development of current-driven turbines is now beginning to reach the upper limits in terms of sizing and cost scaling. Incremental increases in energy generation have been occurring from year to year since the evolution of this technology began. However, larger structures having bigger impellers (predominantly in the style of wind turbines) are not necessarily a more economical way of producing electricity. As the scale of these turbines becomes bigger and more complex, the increased production of electricity and other by products, such as hydrogen, result in less cost effective energy production, owing to increased manufacturing, transport and installation costs. Not only do they become more expensive, but they are harder to maintain and require differing methods of access and possibly extraction, also adding to the cost. [0012] Recent research and development in underwater turbines suggest that more cost effective and efficient methods must be developed in order to effectively produce renewable energy from these environments. The enormous pressures of depth, combined with the relentless flows of currents and the corrosive nature of salt water, are a challenging environment from which to obtain energy. Whilst being sustainable, marine currents place enormous forces on the infrastructure of any underwater energy producing plant. What is now required is a quantum approach to the physics of design together with a fundamental increase in the generation of energy production requiring the integration of two essentially separate technologies, specifically the turbine and generator. [0013] Conically shaped turbines are well known in the art with the first such shape appearing in approximately 1877. U.S. Pat. No. 188,020 issued to Emmons Manley of New York, describes a conically shaped turbine with blades attached to the outside, and extending radially outward from the centre toward the rim. The intended use of this turbine was to power WO 2013/110140 PCT/AU2013/000068 4 mills. This was followed by several more water turbines such as, for example, U.S. Pat. No. 587814 issued to Fredrick Harford 1897, which incorporated a conical nose cone and contra rotating front and rear blades to transfer power to a pulley wheel that would transfer energy to shore using a belt system. [0014] U.S. Pat. No. 868798 issued to Robert McLaughlin 1907 of Baltimore USA, described the first completely conical ellipse shaped turbine, and incorporated two cones joined to a cylindrical waist section. This was followed, albeit several decades later, by U.S. Pat. No. 4,722,665, issued to Warren Tyson 1988 New South Wales Australia, which described a water turbine having a single conical shape with blades extending along its axis, and an internal generator and pump. U.S. Pat. No. 7,011,501, issued to Bjorn Lindberg 2006, similarly describes a water turbine having a conical shape with blades around its centre and positioned within a shroud, and having a rotating central shaft connected to an external generator. [0015] US patent 4,722,665, issued to Tyson, describes a water turbine having a single conical hull and specific blade profile. However, this design has several limitations that are described as follows. Firstly, it only has one conical forward section which limits its use to water bodies having unidirectional current flows. Secondly, the shape of this turbine, which comes to an abrupt halt at the base of the cone and blades, would tend to create significant backflow and low pressure areas at the rear of the device, which would not only create cavitation but would tend to destabilize the turbine. Finally, the turbine incorporates 3 small alternators that are housed within the hull of the turbine, and which use a system of a sun wheel and planet gears to produce a relatively small amount of electrical energy. [0016] US patent 7,011,501, issued to Lindberg, describes a water turbine having a design that allows adequate current flow over the body of the turbine. However, any advantage gained by the hull and blade profile is lost by the proposed use of a rotating shaft, which is attached to an external generator using a system of gears. There are significant energy losses inherent in this type of geared design which is used to power an external generator. [0017] In view of the above mentioned limitations in the prior art, there is a need for improvement in both turbine design and energy generation. More specifically, there is a need for a water turbine having improved efficiency and reliability without substantial increases to cost of production.

WO 2013/110140 PCT/AU2013/000068 5 [0018] In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of the common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned. Summary of the invention [0019] According to one aspect of the present invention, there is provided a water turbine for electric power generation, said water turbine comprising: (a) a body having an internal cavity for housing a variable output generator, said body being rotatable about a central shaft; and (b) one or more turbine blades being adapted to engage an axial flow of water, said one or more turbine blades extending from a leading end of said body in one or more of: (i) a substantially helical configuration; and (ii) a downstream direction relative to said leading end, wherein in use, said one or more turbine blades channel said flow of liquid about said body such that said body is caused to rotate about said central shaft. [0020] The body preferably comprises a leading portion adjacent the leading end, this leading portion having an increasing cross-sectional diameter as it extends from the leading end. The body may also comprise a central portion adjacent said leading portion. The body may also comprise a trailing portion adjacent the central portion, this trailing portion having a decreasing cross-sectional diameter as it extends away from the central portion. In an alternative embodiment of the present invention, the outer surface of the water turbine (including the body and/or the turbine blades) may have a dimpled finish, which may be achieved either during manufacture of the turbine components, or applied as an external coating/layer after assembly of the turbine. Advantageously, the dimpled finish of the outer surface of the water turbine reduces the drag of the turbine as it rotates in the water, and improves the efficiency of the turbine in relation to power generation.

WO 2013/110140 PCT/AU2013/000068 6 [0021] The leading portion and/or the trailing portion may have a substantially conical shape. Advantageously, the body consists of a streamlined three dimensional conical bi-pyramid, ellipsoid or similar geometrically shaped central body. This conical style of body design is preferred due to the volume of water it displaces and directs at the blades, and the subsequent torque which is imparted by the impeller. Large amounts of torque are required to produce significant amounts of energy. The body design also affords enough available space within the hull, to house or contain an internal generator. It is also advantageous that the body be formed from a single moulded piece of material. In an alternative embodiment, the conical bi-pyramid central body may be formed by joining a three dimensional cone and its mirror image base to base. Fixed between said bases may be an additional waist section, referred to above as the central portion. [0022] The turbine blades preferably extend along the leading portion and the central portion of the body. In a particularly preferred embodiment of the invention, the turbine blades also extend along the trailing portion of the body. [0023] The radial dimension of the turbine blades may be greatest in an area about the central portion. In addition, the turbine blades may project axially outward from an outer surface of the body. The positioning of said turbine blades about the body is preferably hydro-dynamically symmetrical to allow rotation of the body about the central shaft in either a clockwise or anti clockwise direction. [0024] Advantageously, each said blade shall uniformly extend from the leading end and gradually increase in radial dimension (chord) and pitch, traversing in a circumferential direction around the body of the turbine and continuing over the central portion, whereupon the blades will reach their apex. Said blades then extend toward the trailing portion of the body, continuing in a circumferential direction, and gradually decrease in radial dimension and pitch. The number of complete rotations around the axis of the body by the blade is advantageously at least one, but generally not greater than three to six. [0025] Each of the turbine blades preferably comprises a distal edge having a bulb or tear shaped cross-section. Advantageously, each blade will have located at its distal edge, a bulb or formed hump that shall transcend toward the root of the blade in a teardrop type formation. This bulb may extend away from the distal edge and toward the flow of liquid at an angle of between about 70 to 80 degrees. The distal edge of the bulb may also gradually taper along its length as it extends toward the leading and trailing ends. The purpose of the bulb is to act as a type of WO 2013/110140 PCT/AU2013/000068 7 leading edge aileron in order to not only strengthen the form of the blade but also to better engage, accommodate and streamline the flow of liquid over the impeller. The distal edge of the blade may also incorporate serrations or ridges that extend along at least a portion of the distal edge. [0026] In addition, it is also advantageous that each of the blades overlap their adjacent blades, which helps to ensure that maximum available thrust is available for a given application. Each blade ideally has a uniformly swept curve along its chord tending to concave toward its root, and extending around the body so as to form channels between adjacent blades, creating resultant flow passages therein. The blade root may extend onto or below the periphery of the body, deepening the flow passages ahead of the central portion, thus causing the flow to diverge further and increase the force of the liquid flow (e.g. current flow) onto the blades. Traversing around the device and diverging in the downstream direction of the current flow, these flow passages are such that, as current occasions to flow through them, the blades of the turbine are caused to rotate. [0027] The water turbine may also comprise a plurality of secondary turbine blades positioned between the primary turbine blades. These secondary turbine blades may project radially outward from one or more of the leading portion, the central portion, or the trailing portion. In addition, the secondary turbine blades may be substantially rectangular in shape. [0028] Oriented about the central portion, and around the periphery of the body at the base of the flow passages, the turbine advantageously includes a secondary smaller set of in-line blades, referred to above as secondary turbine blades. The number of secondary turbine blades within the flow passages may vary, although their function is primarily to interact with the laminar flow continuing along the flow passages, and increase the thrust of the turbine, which is measured as a corresponding rise in horsepower. [0029] In a further embodiment of the invention, the body of the turbine is configured so that while the leading portion is similar to that of the primary embodiment, the trailing portion has a longer and more elongated conical shape. This allows a current of uni-directional flow to engage the leading portion of the turbine, quickly traverse upward and into the flow channels formed between the blades, and then gradually return to the current flow over the trailing portion. The configuration of the blades passing beyond the central portion and toward the trailing portion taper to and end about a third of the way along the trailing portion of the body. Consequently, the flow passages continuing over and beyond the central portion become WO 2013/110140 PCT/AU2013/000068 8 immediately shallower downstream as they extend toward the trailing end of the turbine, thus reducing drag, low pressure zones or any possible occurrence of cavitation that may occur. This embodiment of the invention is primarily suited to a uni-directional current flow. [0030] In an alternate embodiment of the present invention, the trailing portion may be separated from the central portion of the body such that the trailing portion does not define the internal cavity. In addition, the trailing portion may be adapted to rotate about the central shaft in an opposing direction to the leading portion and the central portion. Advantageously, the trailing portion includes opposing turbine blades that extend axially outward from the trailing portion. In use, the opposing turbine blades may channel the flow of liquid about the trailing portion such that the trailing portion body is caused to rotate about the central shaft in an opposing direction to the leading portion and the central portion. [0031] The use of contra-rotational turbine impellers has a number of advantages over conventional impeller devices, including near zero reactive torque on the support structure, zero (or close to zero) backflow turbulence in the wake of the impeller, and high relative inter-rotor rotational speeds. These advantages facilitate increases in blade tip speeds and further streamline the laminar flow around and beyond the device, resulting not only in increased efficiency but also leaving a negligible environmental footprint. This embodiment of the invention would be mainly suitable for uni-directional current flows as in open ocean or river currents. [0032] The trailing portion, according to this alternate embodiment of the invention, may comprise a further internal cavity. Desirably, the internal cavity and/or the further internal cavity may contain buoyant material which in use allows the water turbine to attain neutral buoyancy, positive buoyancy; or negative buoyancy. [0033] It is desirable that the central shaft extends through the body of the turbine, and along its longitudinal axis. This central shaft is preferably manufactured from a metal or a composite material. The central shaft acts to counter balance the body of the turbine, and preferably supports the rotation of the body by engaging with at least two electromagnetic bearings (or similar mechanical equivalent) that are fixed to the leading and trailing ends of the body of the turbine. Advantageously, these bearings, whilst having internal magnetic fields, will have no external magnetic fields and therefore can be fixed directly to the body of the turbine. The central shaft, being longitudinally aligned with the body, is journaled between the two magnetic bearings, allowing the body of the turbine to rotate around the stationary central shaft.

WO 2013/110140 PCT/AU2013/000068 9 [0034] According to a further aspect of the present invention, there is provided a variable output generator for use with a water turbine according to the preceding aspect of the invention, said variable output generator comprising: (a) a plurality of magnetic members positioned around an inner surface of said internal cavity in a circular configuration, said magnetic members being rotatable about said central shaft in response to rotation of said body; (b) a shaft sleeve positioned about said central shaft, said shaft sleeve being movable along said central shaft in a longitudinal direction; and (c) at least one stator arm connected to said shaft sleeve, said stator arm having a distal end and a plurality of field windings positioned thereon, wherein said shaft sleeve is movable along said central shaft to align said field windings on said stator arm with said plurality of magnetic members, and to control the generation of electric power from said variable output generator. [0035] The plurality of magnetic members may be arranged to form one or more rings of magnetic members, wherein the magnetic members in each of these rings are evenly spaced around the inner surface of the internal cavity. Advantageously, these magnetic members are neodymium rare earth magnets or any similar magnetic (or magnetisable) material. [0036] The distal end of the stator arm may comprise one or more prongs and upon each of these prongs are mounted a plurality of field windings to form a stator head. In use, these prongs may be aligned with one of the rings of magnetic members by controlling movement of the shaft sleeve along the central shaft. When the prongs are aligned with the rings of magnetic members, it is preferable that the rings of magnetic members are sufficiently spaced apart from the stator heads (e.g. the equivalent of an air-gap in conventional generators) to allow for generation of electric power by the variable output generator by inducing either an AC (e.g. three-phase) or DC voltage in the plurality of field windings. It should be understood that the configuration of the generator could be modified to produce either AC or DC power depending on the specific requirements of a given application. [0037] The turbine, upon engaging the flow of liquid and commencing rotation, shall also cause rotation of the rings of magnetic members fixed within the internal cavity of the body of the turbine. As the magnetic members pass the field windings on each of the stator arms, a WO 2013/110140 PCT/AU2013/000068 10 voltage will be induced, this voltage being equal to the number of turns in the field windings on each stator arm multiplied by the rate of change in the flux, according to Faraday's law of electromagnetic induction. The shaft sleeve, with the stator arms fixed upon it, is capable of motion along the central shaft and preferably mechanically actuated via a servo motor fixed to the end of the shaft sleeve, which will allow the prongs of the stator arms to become partially or fully engaged with the rings of magnetic members. The positioning of the shaft sleeve and stator arms, relative to the magnetic members, is preferably determined by a calculation of the strength and velocity of the flow of water acting on the turbine, and thus allows for a generator with a variable output. The speed at which the turbine actually rotates is determined by the amount of load applied by the generator. Therefore if the torque required by the generator is greater than the flow of water engaging the turbine, rather than stalling, the prongs of the stator arms may be re-positioned relative to the rings of magnetic members in order to maximize the production of energy, without compromising the function of the device. [0038] Such a generator may operate equally efficiently in a clockwise or anti-clockwise direction and would therefore be suitable for use in either a uni-directional and bi-directional current flow. In either case, the electrical current could then be extracted from the turbine via insulated electrical cable to a shore based electrical grid. [0039] The turbine according to the previous embodiments of the invention can be mounted within a flow enhancer or venturi duct which, having an open funnel at its leading end, will occasion the laminar flow of the current (or water flow) to constrict and accelerate (in accordance with Bernoulli's law) as it passes through. As the water flow accelerates over and around the body of the turbine, it has the consequential effect of lessening blade tip losses (by improving efficiency according to the shape of the venturi duct), and returning the water flow to its natural flow speed as it exits the opening through the trailing end of the venturi duct. The venturi duct should be shaped and positioned in relation to the turbine in such a fashion that whilst allowing the water to pass through it and over the blades of the turbine, it must also allow sufficient room for the water flow to interact with the blades and tips and escape past them in an efficient manner. It should also be appreciated that where a bi-directional turbine is used, the shape of the venturi duct may differ to allow for a bi-directional current flow. In this case, the diameter of the venturi duct may be narrower around its central region, and greater at its distal ends (i.e. the diameter of the venturi duct at each of its distal ends is substantially uniform). However, such configurations will be clearly understood by a person skilled in the art.

WO 2013/110140 PCT/AU2013/000068 11 [0040] According to a further still further aspect of the present invention, there is provided a venturi duct for housing a water turbine according to any one of the preceding aspects of the invention, said venturi duct comprising: (a) an inlet for receiving said flow of water, said inlet including a circular inlet opening; (b) an outlet for discharging said flow of water received by said inlet, said outlet including a circular outlet opening having a greater diameter than said circular inlet opening; and (c) a support means attached to said central shaft of said water turbine, said support means being adapted to maintain said central shaft in a substantially stationary position, wherein in use, said venturi duct channels and accelerates said flow of water across said water turbine. [0041] One advantage of a flow enhancer is that the open funnel can more effectively capture the flow of water (e.g. current flow), helping to lessen any efficiency drop that may occur when the turbine is not precisely aligned within the flow (e.g. where the current has slightly changed in direction, or in the case of a bi-directional flow, when the current does not exactly reverse by 180 degrees). Further advantages of venturi ducts are that they can shade the turbine from direct sunlight, thus any growth of algae or weeds can be significantly reduced. Also the venturi duct can decrease the risk of marine life and debris interacting with the turbine if a suitable screen is positioned over the leading, current facing, end of the duct. [0042] According to a still further aspect of the present invention, there is provided a generator cooling system for use with a variable output generator according to the second aspect of the invention, said system comprising: (a) a water inlet located in a leading portion of said central shaft to allow water to enter said internal cavity; (b) a water outlet located in a trailing portion of said central shaft to allow water to exit said internal cavity; (c) one or more control valves located at each of said water inlet and said water outlet; WO 2013/110140 PCT/AU2013/000068 12 (d) one or more temperature and/or pressure sensors located within said internal cavity, wherein in use, said sensors monitor operating conditions within said internal cavity and control the flow of water into and out of said internal cavity via said water inlet and said water outlet by opening and/or closing said control valves. [0043] Rotating magnets have a tendency to heat up the field windings on the stator arms, and a method is required to enable cooling of these field windings to ensure safe operation of the turbine. In accordance with this aspect of the invention, the field windings are preferably encased in blocks of polymer resin to protect them from corrosive salt water. In addition, a system of holes or ducted conduits may be fashioned into the resin allowing the ambient water inside the inner cavity of the body, entering through the water inlets in the main shaft, to engage with the heated field windings on the stator arms, thus effecting their immediate and continual cooling. Upon engaging with the field windings on the stator arms and dissipating their latent heat, the water shall continue to flow through the inner cavity of the body and exit through the water outlets in a trailing portion of the central shaft. [0044] In a further alternative embodiment of the present invention, the turbine includes a single continuous turbine blade that may be attached to a region at or in front of the leading end of the body of the turbine, and extending along the body of the turbine in a spherical spiral formation. The breadth of the turbine blade, from tip to root across the chord preferably increases outward in dimension as it traverses the body of the turbine, whilst maintaining a predetermined distance from the periphery of the body. On approaching the central portion of the body, the spiral blade may extend to its apex as it passes over this region and then gradually decrease in radial dimension as it extends toward the trailing end of the body. Although the turbine blade may be attached to and form part of the body in much the same way as the said turbine blades of the preceding embodiments, it may be preferable to have the spiral blade extending above and around the periphery of the body, thus permitting the flow of water (e.g. current flow) to continue around it. In use, the spiral turbine blade may tend to stretch, lengthen and contour in response to the laminar flow of the water, thus yielding an exceptionally efficient profile. Once this profile is attained, the spiral turbine blade may advantageously engender extremely high-level revolutions within the parameters of the current flow. This turbine design would be suitable for use in both a bi-directional and uni-directional flows.

WO 2013/110140 PCT/AU2013/000068 13 [0045] As in previous embodiments, said spiral turbine blade may have located at its distal or leading edge, a bulb or formed hump that transcends and tapers diagonally downstream toward the root of the spiral turbine blade, in a teardrop-type formation. This bulb may also provide a counterweight to help maintain balance and increase torque, not only adding a measure of strength and power to the turbine blade but also rendering it harmless to marine life and affording additional protection from debris. Brief description of the Drawings [0046] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. These embodiments are given by way of illustration only and other embodiments of the invention are possible. Consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description. In the drawings: [0047] Figure 1 is a cross-sectional side view line drawing of a water turbine and variable output generator according to a representative embodiment of the present invention; [0048] Figure 2 is an end view line drawing of the water turbine of Figure 1; Figure 2A is a side view line drawing of a secondary blade that is attached to the body of the water turbine of Figure 1; [0049] Figure 3 is a cross-sectional perspective view of a primary turbine blade that is attached to the body of the water turbine of Figure 1; [0050] Figure 4 is a cross-sectional line drawing of a distal portion of the turbine blade of Figure 3; Figure 4A is a further cross-sectional line drawing of the distal portion of the turbine blade of Figure 4, inclined at an angle of between about 70 to 80 degrees; [0051] Figure 5 is a perspective view line drawing of rings of magnetic members positioned within the internal cavity of the body of the water turbine of Figure 1; [0052] Figure 6 is a perspective view line drawing of the central shaft of the water turbine shown in Figure 1, together with a shaft sleeve and a plurality of stator arms that form part of a variable output generator; Figure 6A is cross-sectional line drawing of field windings attached to prongs of a stator arm, as well as the corresponding magnetic members attached to the internal cavity of the water turbine of Figure 1; WO 2013/110140 PCT/AU2013/000068 14 [0053] Figure 7 is a perspective view line drawing of the central shaft of the water turbine shown in Figure 1, with internal conduits shown in phantom; [0054] Figure 8 is a block diagram of a generator cooling system for use with the variable output generator and water turbine of Figure 1; [0055] Figure 9 is a cross-sectional side view line drawing of a water turbine and variable output generator according to a further embodiment of the present invention; [0056] Figure 10 is a cross-sectional side view line drawing of the water turbine of Figure 9 positioned within a venturi duct; Figure 10A is an end view line drawing of the water turbine and venturi duct of Figure 10; Figure lOB is a partial cross-sectional view line drawing showing the attachment of a forward portion of the central shaft to a support means of the venturi duct of Figure 10; Figure 10C is a partial cross-sectional view line drawing showing the attachment of a rear portion of the central shaft to a support means of the venturi duct of Figure 10; [0057] Figure 11 is a cross-sectional side view line drawing of a contra-rotational water turbine and variable output generator according to a further embodiment of the present invention; [0058] Figure 12 is a perspective side view line drawing of a water turbine, having a spherical spiral turbine blade, according to a further embodiment of the present invention; Figure 12A is a partial cut-away side view line drawing of an extended shaft attached to the water turbine of Figure 12; Figure 12B is a cross-sectional profile view line drawing of a spiral turbine blade suitable for use in a bi-directional flow; [0059] Figure 13 is a side view line drawing showing a plurality of the venturi ducts of Figure 10 attached to a construction in an oceanic current flow; Figure 13A is a side view line drawing showing a venturi duct of Figure 10 deployed in a river current flow. Description of Preferred Embodiments [0060] Embodiments of the variable output generator and water turbine will now be described with reference to the accompanying drawings. The invention is particularly useful in relation to water turbines positioned in naturally occurring current flows such as, for example, in rivers and oceans, and it will therefore be convenient to describe the invention in that environment. However, it should be understood that the invention is intended for broader application and use.

WO 2013/110140 PCT/AU2013/000068 15 [0061] Referring to the drawings, Figure 1 illustrates a water turbine 100 and variable output generator 200 in accordance with a representative embodiment of the present invention. The turbine 100 is intended for use in a bi-directional current flow such as, for example, in naturally occurring oceanic or river currents. The turbine 100 comprises a body 70 or primary hull, which acts as the external shell or exoskeleton of the turbine 100. The body 70 of the turbine 100 is rotatable about a central shaft 76 that extends through an internal cavity 50 of the body 70. This internal cavity 50 is preferably shaped for housing the variable output generator 200. [0062] The body 70 of the turbine 100 is essentially a conical bi-pyramid that is formed by joining together the two cone structures along their bases. In this representative embodiment, shown in Figure 1 of the drawings, the body 70 includes a central portion 86 or waist section that is fixed between a leading portion 84 (i.e. the forward cone) and a trailing portion 85 (i.e. the trailing cone). It should be appreciated that whilst any suitable material could be used in the construction of the body 70, it would be preferable to use a rigid composite of material, such as Kevlar or thermo-plastic and carbon epoxy laminate. Owing to the three dimensional complex geometric shape of the body 70, a high level of structural optimisation can be attained using such composite materials, which can be formed into complex shapes and welded together using quick and inexpensive techniques. As well as strength, form and rigidity, these composite materials have the additional benefits of being relatively impervious to the corrosive effects of salt water and the destructive forces of currents, and are able to withstand long term immersion in water. [0063] The internal cavity 50 of the body 70 is formed by an inner hull 75, which includes surfaces that correspond to the external structure of the body 70. In other words, the internal cavity 50 comprises an inner central portion 186 that is fixed between an inner leading portion 184 and an inner trailing portion 185. It is preferable that the inner hull 75, as well as the central shaft 76, be constructed from a marine grade stainless steel. Within the internal cavity 50, and forming part of the generator 200, are a plurality of rings 150 of magnetic members 78 that are held in place around the inner central portion 186 using magnetic housings 178. Preferably, the magnetic members 78 are rare earth magnets although it should be understood that alternative magnetic or magnetisable materials could also be used. [0064] As previously indicated, the central shaft 76 passes through the internal cavity 50 and includes electromagnetic bearings 80 at its distal ends which facilitate rotation of the body 70 about the central shaft 76. Attached to the central shaft 76, and also forming part of the generator 200, is a shaft sleeve 77 which is moveable, in a limited range, along the central WO 2013/110140 PCT/AU2013/000068 16 shaft 76 using a servo motor 88. At least the outer shell of the servo motor 88 and the casing for the electromagnetic bearings 80 preferably also include protective marine coatings to render them free from corrosion. Fixed to the shaft sleeve 77 are a plurality of stator arms 82 that extend outwardly toward the inner hull 75, and terminate a short distance from the inner central portion 186 of the inner hull 75. At a distal end of each stator arm 82, and proximate the inner central portion 186 of the inner hull 75, are a plurality of stator prongs 81 that each support field windings 79. [0065] The central shaft 76 also includes one or more water passage inlets 90 and inner water passage inlets 190, proximate the leading portion 84 of the body 70, that allow water (e.g. sea water) to enter the internal cavity 50 of the body 70. The inner water passage inlets 191 are positioned on a portion of the central shaft 76 within the internal cavity 50. The central shaft 76 also includes corresponding water passage outlets 91 and inner water passage outlets 191 that allow this water to be discharged from the internal cavity 50 of the body. The inner water passage outlets are positioned on a portion of the central shaft 76 within the internal cavity 50. The water passage outlets 91 are preferably located at the opposite end of the central shaft 76, proximate the trailing portion 85 of the body 70. However, given that the turbine 100 and generator 200 illustrated in Figure 1 are intended for use in a bi-directional current flow, it should be appreciated that the water passage inlets 90 and water passage outlets 91 will reverse their function as the current begins to flow in the opposing direction. [0066] It is also preferable that the central shaft 76 is hollow in structure (or incorporates at least an internal passage along its length) to allow for the insertion and housing of high voltage output cables 97, one or more input voltage cables 98, and preferably a command centre output/input cable 96. [0067] It is clear from Figures 1 and 2 that the turbine 100 includes one or more turbine blades 71 that extend from a leading end of the body 70 in a downstream direction, and in a substantially helical configuration. More specifically, and as shown in Figures 1 and 2, the turbine blades 71 extend along the body 70 of the turbine 100, from the leading portion 84 through to the trailing portion 85. The turbine blades 71 are adapted to engage an axial flow of water (i.e. a flow of water that aligns with the longitudinal axis of the turbine 100). The turbine blades 71 channel the flow of water, through flow passages 74 formed between adjacent turbine blades 71, causing the body 70 to rotate about the central shaft 76. As seen in Figure 1, the depth of the flow passages 74 formed between the turbine blades 71 is relatively uniform about the leading portion 84 and trailing portion 85 of the body 70. However, toward the central WO 2013/110140 PCT/AU2013/000068 17 portion 86 of the body 70, the turbine blades 71 gently curve upward to direct the laminar flow of the flow of water or current (shown by the arrows 109 depending on the direction of the current flow) to the main thrust producing sections of the primary turbine blades 71. In Figure 1, the generator 200 is shown located in a neutral position with the prongs 81 of the stator arms 82 being positioned between the rings 150 of magnetic members 78, a position in which it would not generate energy. The arrows shown adjacent to the prongs 81 indicate the directions in which stator arms 82 can be moved in order to electromagnetically engage the prongs with the rings 150 of magnetic members 78. [0068] In Figure 2 of the drawings, an end view of the turbine 100 is shown from the leading end 62 of the body 70. As previously described, each of the turbine blades 71 extends from the leading end 62 of the body 70, circumferentially traversing around the body 70 (in a helical or spiral pattern), and increasing in its chord 164 (i.e. the depth of the turbine blade 71, measured between the outer edge of the blade 71 and the body 70 of the turbine 100) until reaching the centre plane 66 of the body 70. In other words, each of the turbine blades 71 gradually increases in radial dimension, reaching an apex over the central portion 86 of the body 70. Upon passing the centre plane 66 (moving in a forward direction) of the body 70, each of said turbine blades 71 continues around the central potion 86 and trailing portion 85 of the body 70 in a circumferential direction, decreasing in chord 164 and radial dimension, and extending toward the trailing end 64 of the body 70. Each of the turbine blades 71 preferably finishes at a point proximate the trailing end 64 of the body 70 such that the turbine blades 71 are hydrodynamically symmetrical. [0069] Also illustrated in Figure 2, is an end view of the electromagnetic bearing 80 at the leading end 62 of the body 70, which is fixed to an internal portion of the leading portion 84 of the body 70 and accommodates the leading end of the central shaft 76. This leading end of the central shaft 76 is supported within the magnetic field of the magnetic bearing 80 and forms part of the stationary drive train around which the body 70 of the turbine 100 rotates. An identical configuration exists at the trailing end 64 of the body 70, wherein the trailing end of the central shaft 76 is supported with the magnetic field of the magnetic bearing 80 fixed within the trailing portion 85 of the body 70. This drawing also shows the water passage inlet 90 at the leading end 62 of the body 70. It is also preferable that the primary turbine blades 71 include bulbs 72 at their distal edges (as further illustrated in Figure 3 of the drawings). Each of these bulbs 72 extends along the length of the distal edge, gradually tapering as it nears the leading end 62 and trailing end 64 of the body 70. The distal edge bulbs 72 form a type of leading edge aileron to WO 2013/110140 PCT/AU2013/000068 18 further interact with the current flow 109 and streamline it over the primary turbine blades 71. In this manner, the bulbs 72 gently blend in with the curve of the turbine blade 71, with the chord 164 intercepting the current flow 109. The flow passages 74 formed between adjacent pairs of blades 71 extend along the length of the body 70 in a downstream direction, thus permitting a smooth laminar flow of the current 109 and allowing it to efficiently engage with and cause rotation of, the turbine 100. [0070] Figure 2A of the drawings illustrates a secondary turbine blade 171 that is preferably positioned within each of the flow passages 74 formed between adjacent pairs of turbine blades 71, about the central portion 86 of the body 70. This secondary turbine blade 171 includes bulbs 172 or moulded formed humps located along a distal edge 176, which taper downwards toward the root 173 of said blade 171 in a teardrop type formation. The secondary turbine blade 171 also incorporates a chord 174 that preferably intercepts the current flow 109. [0071] The secondary turbine blades 171 are preferably rectangular in shape (as shown in Figure 2A) and may number greater than one per flow passage 74. Desirably, the secondary turbine blades 171 have a maximum height that is about 20% of the height of the primary turbine blades 71, and may be angled at around 40 degrees to the longitudinal axis of the body 70, and therefore to the current flow 109. They may also be mechanically fastened to the body 70 using locknuts and connection bolts 103, although other suitable attachment means are also envisioned. The primary purpose of the secondary turbine blades 171 is to further interact with the laminar flow of the current 109, as it passes through the base of the flow passages 74, resulting in increased thrust in the turbine 100 and a corresponding increase in horsepower at the generator. [0072] Figure 3 is a cross-sectional perspective view of a turbine blade 71 shown in Figures 1 and 2 of the drawings. The turbine blade 71 is preferably moulded as a complete component of the turbine 100 and is solid through its interior. It has a concave curve through its chord 164 on both sides of the blade 71, extending to its root 163, to form a hydro-dynamically symmetrical turbine blade 71. Also shown in this drawing is the distal edge of the blade 71 which includes a bulb 72 (as previously discussed in relation to Figure 2 of the drawings). This bulb 72 is more pronounced nearest the central plane 66 of the body 70, and gradually tapers toward the leading end 62 and trailing end 64 of the body 70. Furthermore, as the blade 71 extends toward the leading end 62 and trailing 64 (from the central plane 66), the bulb 72 blends into the swept curve of the chord 164, creating increased strength and stability whilst enabling the blade 71 to capture more energy from the current flow 109.

WO 2013/110140 PCT/AU2013/000068 19 [0073] Figure 4 is a cross-sectional view of the bulb 72 of the turbine blade 71 shown in Figures 1 and 2. This drawing illustrates, as an example, how the profile of the bulb 72 could be aligned at approximately 180 degrees to the lower profile (i.e. the profile of the blade 71 below the bulb 72) of the blade 71 as it extends to the blade chord 164. This configuration allows for a bi-directional current flow 109. By contrast, the configuration shown in Figure 4A includes bulbs 72 that are angled toward the current flow 109 at an angle of between about 70 to 80 degrees (as shown by the symbol Q in the drawing) to the chord 164, and are therefore suited to a uni-directional current flow. [0074] A sectional view of the generator 200 is shown in Figure 5 of the drawings. This drawing illustrates a plurality of magnetic members 78 (preferably rare earth neodymium boron (NdFeB) or similar magnets or magnetisable materials) positioned in housings 178 to form rings 150 of magnetic members 78 that extend around the inner central portion 186 of the inner hull 75. The magnetic members 78 within each of the rings 150 of magnetic members 78 align and form precise tolerances with the field windings 79 on the prongs 81 of the stator arms 82. As previously indicated, the stator arm 82 can be repositioned to allow the field windings 79 to align with the rings 150 of magnetic members 78 to produce energy. Preferably, the inner hull 75 is constructed from marine grade stainless steel so as to protect it from the corrosive forces of likely underwater environments, and can bonded directly to the body 70 or outer hull of the turbine 100. The rings 150 of magnetic members 78 (when inserted into the housings 178), as well as a number of reinforcing ribs 175 positioned longitudinally within the inner hull 75, add lateral strength to the body 70 of the turbine 100, ensuring that any possible distortion of the body 70 is kept to a minimum. [0075] A further sectional view of the generator 200 is shown in Figure 6. As previously described with reference to Figure 1 of the drawings, each of the stator arms 82 is mounted directly to the shaft sleeve 77, so that the plurality of stator arms 82 are evenly spaced around the circumference of the shaft sleeve 77. The shaft sleeve 77 is movable, in a longitudinal direction, along the central shaft 76 upon being actuated by a servo motor 88 (or similar actuating device). Controlling the position of the shaft sleeve 77, and therefore the field windings 79 on the prongs 81 of the stator arms 82, allows for the partial or full alignment of the field windings 79 with the rings 150 of magnetic members 78 depending on the strength of the current flow 109. Preferably, the shaft sleeve 77 is moveable along machined splines 196 that are pressed into the outer surface of the central shaft 76, thus ensuring smooth travel and location of the stator arms 82 without any lateral (i.e. rotational) movement. The servo motor 88 WO 2013/110140 PCT/AU2013/000068 20 is preferably an AC electric motor powered by a cable 98, which carries AC electric current from a remote control centre (not shown) 92. Upon being actuated by a signal from the remote control centre 92 preferably sent via a command centre output/input cable 96, the servo motor 88 winds an internal rod (not shown) in or out connected to the base of said shaft sleeve 77 which will occasion travel of the shaft sleeve 77 to a predefined position. However, it should be appreciated that alternate electro-mechanical means could be used to bring about movement of the shaft sleeve 77 along the central shaft 76. [0076] Figure 6 also illustrates the positioning of the various cables within central shaft 76. For example, the central shaft 76 preferably houses the insulated high voltage cable 97 that receives the power output from the generator 200 (via the transmission cables 198 which extend from the field windings 79 on the stator arms 82) and carries said power from the turbine 100 to an external land-based electrical grid. [0077] Figure 6A provides a sectional view of the generator 200, and specifically the alignment of the field windings 79 with the rings 150 of magnetic members 78. Preferably, the field windings 79 and stator heads 179 are encased in a polymer resin 89 that protects these from corrosion and also aids in their cooling during operation of the generator 200. Desirably the polymer resin 89 completely encases the windings 79 and provides a thin film over the metallic stator heads 179 so that electromagnetic induction between the field windings 79 and the magnetic members 78 can still occur. In a representative embodiment of the present invention, the polymer resin 89 may have tiny holes or conduit ducts 189 machined through its structure to permit the ambient water contained within the inner hull 75 to continue and be momentarily retained around the field windings 79 and stator heads 179 to affect their immediate and continual cooling. As the magnetic members 78 are fixed in their housings 178, and have a ceramic composition, they generally do not require a protective coating. [0078] Figure 7 is a sectional view of the turbine 100 and generator 200, which further illustrates how the central shaft 76 is located and retained within the annular electro electromagnetic bearing 80. The circular opening of the bearing 80 is precisely sized to journal the central shaft 76, allowing it to be contained within the magnetic field produced by the bearing 80. The bearing 80 shown in Figure 7, as previously described, is mounted and mechanically fastened to an internal portion of the leading portion 84. An identical bearing 80 is mounted and mechanically fastened to an internal portion of the trailing portion 85 to ensure that the central shaft 76 is supported at both ends. As a result, the central shaft 76 remains balanced within the magnetic fields produced by the bearings 80, and consequently remains WO 2013/110140 PCT/AU2013/000068 21 stationary whilst the body 70 of the turbine 100 rotates around the central shaft 76. Preferably, the central shaft 76 is constructed from a marine grade stainless steel of high strength and rigidity so as to limit any flexed or lateral movement during operation of the turbine 100. [0079] Figure 8 illustrates a block diagram of a control system 92 for controlling and monitoring all aspects of the operation of the turbine 100 and generator 200. The control system 92 operates various functions of the turbine 100 and generator 200 including, particularly, actuation of the servo motor 88 to control the position of the shaft sleeve 77 on the central shaft 76. Additional functions of the control system 92 that are operated either manually or automatically include recording the position and temperature of the stator arms 82, monitoring and activating the ballast and buoyancy systems 87, monitoring the electrical energy being produced and flowing through the high voltage cable 97, interpreting data such as current speed, pressures, and temperatures both internally and external to the turbine 100. In order to control such functions, the control system 92 receives data from a plurality of sensors 93 located in various locations throughout and around the turbine 100. These sensors 93 enable the control system 92 to maintain operation of the turbine 100 effectively, by providing the control system 92 with data concerning the operating conditions of the generator 200 and any required adjustment of the shaft sleeve 77. During normal operation, the position of the stator arms 82 (relative to the rings 150 of magnetic members 78) can change with changes in current 109 velocities, changes in lift surfaces (e.g. fouling), or due to debris interfering with the current flow 109 to the turbine 100. The control system 92 can interpret, calculate and determine any necessary adjustments that need to be made to ensure continued operation of the turbine 100 and generator 200. Shutdown of the turbine 100 may be necessary in certain conditions, such as in the event of failed generator 200 components including the stator arms 82, magnetic members 78, or the shaft sleeve 77, due to excessive wave and turbulence effects, excessive debris or on shore grid failure. Finally, the control centre 92 may be operated from a remote location on the surface, on-shore, via satellite or other remote location. [0080] A further embodiment of the present invention is shown in Figure 9 of the drawings, which illustrates an alternative design for a turbine 300 that is intended for use in a uni directional current flow 109. The body 70 of the turbine 300 is a conical bi-pyramid that has a shortened leading portion 84 and a lengthened trailing portion 85. As a result, the turbine blades 71 are not hydro-dynamically symmetrical. The blades 71 around the leading portion 84 are essentially the same as in the first embodiment of the invention (described above), circumferentially traversing around the longitudinal axis of the body 70 and gradually increasing WO 2013/110140 PCT/AU2013/000068 22 in radial dimension until reaching their apex over the central portion 86 of the body 70. The flow passages 74 between adjacent blades 71 deepen as they extended toward the central portion 86, and further direct the current 109 upon the blades 71. Upon passing the central portion 86 of the body 70, the blades 71 continue to traverse the trailing portion 85 of the body 70 and rapidly taper to an end. The flow passages 74 about the trailing portion 85 also become rapidly shallower as they extend past the central portion 86 and blend substantially into the periphery of the body 70 as they to approach the trailing portion 85. [0081] As with the previous embodiment of the invention, the distal edges of the blades 71 of the turbine 300 are preferably moulded into a bulb shape 72. The bulb 72 traverses the length of the blade 71, or part thereof, and tapers along the distal edge as it extends toward the leading portion 84 and trailing portion 85. The bulb 72 may be configured to angle inward at between about 70 to 80 degrees to its chord 164 (as previously described with respect to Figure 4A) to ensure an optimum angle of attack to the current flow 109. In a particularly preferred embodiment of the present invention, the apex of the bulb 72 may incorporate a plurality of curved serrations 73 that are spaced along the length of the distal edge, or part thereof. Desirably, the serrations 73 become less pronounced at the portions of the blade 71 about the leading 62 and trailing ends 64 of the body 70 although, as with the blade 71 itself, the serrations 73 are more pronounced over the central portion 86 of the body 70. The bulb 72 and serrations 73 preferably provide a smooth laminar flow of the current 109 to continue over the turbine 300 and ensure added strength and rigidity. In addition, the bulb 72 and serrations 73 create blunt edges on the blades 71 that will prevent harm to marine life. [0082] In relation to this embodiment of the invention, the generator 200 is predominantly the same as in the first embodiment, the only difference being the location of the servo motor 88 (and shaft sleeve 77) relative to the stator arms 82. As shown in Figure 9, the servo motor 88 and shaft sleeve 77 are positioned toward the trailing end 64 of the body 70 (as opposed to the leading end 62) so as to counter-balance the rings 150 of magnetic members 78 within the body 70. The cross-sectional view of the turbine 300 and generator 200 shown in Figure 9 illustrates stator arms 82, each having three prongs 81 that are capable of being aligned with three rings 150 of magnetic members 78. However, it should be appreciated that the number of prongs 81 on each stator arm 82 and the number of rings 150 of magnetic members 78 may vary. The stator arms 82 in Figure 9 are shown in a first active position with only one of the prongs 81 being aligned with one of the rings 150 of magnetic members 78. This alignment is achieved by movement of the shaft sleeve 77 (by control of the servo motor 88) along the central shaft 76.

WO 2013/110140 PCT/AU2013/000068 23 [0083] This first active position is the first energy generating position after start-up of the turbine 300 (also applicable to turbine 100) and generator 200. With the stator arms 82 in this configuration, the generator 200 will begin producing electrical energy which can be removed from the generator 200 via the insulated cabling 97. If the current flow 109 is of sufficient strength, the servo motor 88 will, upon receiving a signal from current sensors (not shown) via the command control centre 92 (not shown), reposition the prongs 81 of the stator arms 82 into a second active position, so that two of the prongs 81 align with two of the rings 150 of magnetic members 78. Similarly, if the current flow 109 is even greater, the servo motor 88 can reposition the prongs 81 of the stator arms 82 to a third active position such that three of the prongs 81 align with two of the rings 150 of magnetic members 78, thus producing a greater quantity of electrical energy than was the case in either the first active position or the second active position. The rings 150 of magnetic members 78 are fixed in position within the housings 178, and are aligned with sufficient space therebetween so that as the prongs 81 of the stator arms 82 disengage their alignment with the rings 150, they are momentary in a neutral position before re-engaging (i.e. aligning) with the adjacent ring 150 of magnetic members 78. Depending on the power of the servo motor 88, this disengagement will only be for a very short period of time, but sufficiently long to prevent a single prong 81 of the stator arms 82 from being engaged by two rings 150 of magnetic members 78 simultaneously. [0084] Figure 10 of the drawings illustrates a venturi duct 99 which can be used to house the turbine 300 and increase the current flow 109 over the turbine 300. The venturi ducts 99 works by creating a pressure difference in the volumetric flow, through the duct 99, between the duct inlet 100 and duct outlet 120. These factors, and the efficiency of the duct 99 are largely dependent upon the shape of the diffuser 199 and the ratio between the area of the duct 99 and the area of the turbine 300. Advantageously, the diffuser 199 is shaped so as to create the most practical and attainable pressure drop between the inlet 100 and the outlet 120. This typically means that the diffuser 199 is larger (in cross-sectional diameter) than the duct inlet 100 and increases in cross-sectional diameter as it extends past the apex of the primary turbine blades 71, so as to draw more fluid from the current flow 109 through the inlet 100 of the venturi duct 99. This, in turn, results in increased energy output from the generator 200 and can reduce the minimum size of turbine 100 that is required for a given application. [0085] The turbine 300 is mounted within the venturi duct 99 using cross members 101, and duct hubs 111 and 112 that allow the turbine 300 to be affixed to the diffuser 199, and secured using locknuts and frame connection bolts 103. The cross members 101 are located across both WO 2013/110140 PCT/AU2013/000068 24 the inlet 100 and outlet 120 of the duct 99, and are streamlined so not to interfere with the current flow 109. The cross-members 101 may also contain any necessary sensors 93 and house cabling such as the high voltage output cables 97, one or more input voltage cables 98, and preferably a command centre output/input cable 96, which extend through the central shaft 76. These cables may enter and exit the duct 99 from its trailing or leading end depending on configuration requirements such as, for example, when the duct 99 is tethered to a support structure (as shown in Figure 13A) and the cables may be run in tandem or be contained within tethers 105 (such as shown in Figures 13 and 13A). Preferably, the support structure 107 is anchored to the riverbed 210 to prevent loss of the duct 99. [0086] The venturi duct 99 may also contain a ballast system comprising air tight chambers or nacelles 87 and counterweights 187, which allow the turbine 300 and duct 99 to attain neutral or slightly negative buoyancy within the current flow 109. The ballast system operates by selectively evacuating the nacelles 87 contained within the diffuser 199 of the venturi duct 99 using compressed air. Preferably, the nacelles 87 are located at the top and sides of the diffuser 199, with the counterweights 187 being positioned in the lower portion of the diffuser 199. Advantageously, the counterweights 187 can be detached from the body of the venturi duct 99 to assist in its deployment within the current 109. A simple release mechanism could easily be enacted via the command control centre 92 to detach the counterweights 187 from the duct 99, which would also enable it to immediately rise to the surface of the water. It is also desirable that the venturi duct 99 include a duct screen 102 at its leading end which may be conical in shape to assist in deflecting debris that could otherwise impede current flow 109, or impact (or damage) the operation of the turbine 300. In addition, the screen 102 acts to protect marine life by preventing it from coming into contact with the turbine 100. [0087] Figure 1OA is a front end view of the venturi duct 99 and turbine 300 shown in Figure 10. The venturi duct 99 may also include streamlined stabilizer wings or fins 104 fixed to, and extending outward from, the outer hull of the diffuser 199 in order to trim the pitch and yaw of the turbine 100 and duct 99 within the current flow 109. The stabiliser fins 104 may also contain winglets 114 at their tips to reduce drag and increase lift in the current flow 109. It should be appreciated that the venturi duct 99 may include additional stabilizer wings or fins in order to improve its stability within the current flow 109. [0088] As shown in Figure 10B of the drawings, the turbine 300 is preferably retained within the duct 99 at the leading end 84 via an extended main shaft 166 that connects between the forward magnetic bearing 80 and a forward duct hub 111, which is fixed to cross member 101 WO 2013/110140 PCT/AU2013/000068 25 with locknuts and frame connection bolts 103. In this configuration, a filtered water passage inlet 90 is provided in the nose of the forward duct hub 111 to allow water to enter the internal cavity 50 of the body 70 for cooling purposes as previously described. The main current sensor 93 can also be located at the forward duct hub 111, and will eventually connect to the remote control centre 92 via the central command cable 96. [0089] The trailing end of the venturi duct 99 has a similar configuration, as shown in Figure 10C, which includes a rear extended main shaft 167 that extends between the rear magnetic bearing 80 and the trailing end hub 112, and is fixed to the duct cross member 101 with locknuts and frame connection bolts 103. In this configuration, the rear duct hub 112 preferably contains the water passage outlet 91 to allow water to exit the internal cavity 50 of the body 70. A sensor 93 may also be located at the rear duct hub 112 to monitor and calibrate the current flow 109 across the duct 99. [0090] Figure 11 of the drawings illustrates a further embodiment of the present invention in which the turbine 400 includes contra-rotational portions. In this embodiment, the body 70 of the turbine 400 is separated into a forward section 402 and a rear section 404 sections that rotate in opposite directions about the central shaft 76. In order to achieve independent rotation of the forward section 402 and rear section 404, and in addition to existing magnetic bearings 80, the turbine 400 incorporates inner magnetic bearings 480 which support the internal ends of forward section 402 and rear section 404 about the central shaft 76. It is also preferable that the opposing inner surfaces of the forward section 402 and the rear section 404 include a set of meridional magnets 83. It is desirable that the poles of these magnets 83 be suitably aligned so as to create magnetic repulsion between the opposing inner surfaces of the forward section 402 and rear section 404. Advantageously, this will produce the necessary forces to lessen the rotational friction between the forward section 402 and the rear section 404 of the turbine 400. [0091] The advantage of the contra-rotational rear section 404 is that it reduces backflow turbulence and thus increase rotation of the forward section 402, which results in increased horsepower at the generator 200. The generator 200 shown in Figure 11 is identical to that shown in Figure 1, and its operation is as previously described with respect to the above embodiments of the invention. [0092] In accordance with this embodiment of the invention, the turbine 400 preferably includes a first set of turbine blades 471 positioned on the forward section 402, and a second set of turbine blades 473 positioned on the rear section 404. The first set of turbine blades 471 are WO 2013/110140 PCT/AU2013/000068 26 similar in structure to the turbine blades 71 described in relation to the previous embodiments, extending from the forward leading end 62 and continuing over the central portion 86. However, since the forward section 402 has a truncated trailing portion 485, as the blades 471 extend past the central portion 86 they taper to an abrupt end at or near the junction between the central portion 86 and the trailing portion 485. These blades 471 may also contain bulbs 72 and/or serrations 73 at their distal edges, as described in relation to the previous embodiments of the invention. [0093] Mounted to the rear section 404 are a second set of turbine blades 473 that have a more conventional blade profile and a height that is slightly higher than that of the first set of blades 471. These blades 473 extend, inline, around the circumference of the rear section 404 and are offset at angle of about 40 degrees to the longitudinal axis of the turbine 400, which opposes the angle of the first set of turbine blades 471 so as to bring about the contra-rotation effect. The blades 473 are preferably spaced closer together and are greater in number than the first set of blades 471. As the laminar flow of the current 109 continues over the central portion 86 of the turbine 400 it is immediately intercepted by the contra-rotation of the second set of blades 473. Advantageously, the second set of blades 473 are slightly higher than the first set of blades 471 so as to catch or intercept the wake created by the first set of blades 471. [0094] As with previous embodiments of the invention, the leading end of the central shaft 76 can allow water to enter the internal cavity 50 (now wholly contained within the forward section 402) via water passage inlets 90 and 190. Due to the modified configuration of the turbine 400, water passage outlets 491 are positioned on a rearward facing surface of the forward section 402. Whilst the rear section 404 defines a second internal cavity, it is not necessary for this cavity 450 to contain water. As the generator 200 is wholly contained within the internal cavity 50 of the first section 402, there is no requirement for cooling in the second internal cavity 450. As an alternative, the second internal cavity 450 may contain a buoyant material 95, such as or foam or a similar element, to assist with the buoyancy of the turbine 400. As with the previous embodiment of the invention, the turbine 400 is intended for use in a uni directional current flow 109. [0095] In an alternative configuration of the invention shown in Figure 11 of the drawings, the rear section 404 of the turbine 400 is adapted to cause rotation of the central shaft 76. Advantageously, rotation of the central shaft 76 also causes the shaft sleeve 77 and stator arms 82 (including the stator heads 179 mounted thereon) to rotate within the forward section 402 in an opposite direction to the rotation of the rings 150 of magnetic members 78. This contra- WO 2013/110140 PCT/AU2013/000068 27 rotation of the stator heads 179 and the magnetic members 78 is intended to significantly increase the rate of magnetic flux, thus resulting in increased output at the generator 200. Such a configuration may also allow for the construction of smaller turbines 400 with correspondingly smaller generators 200, due to improvements in efficiency. [0096] Figure 12 of the drawings illustrates a further alternative embodiment of the invention in which the turbine 500 includes a single loxodromic or spherical spiral turbine blade 571. The turbine blade 571 preferably follows a spherical or elliptical type contour around, and above, the body 570 of the turbine 500, thus enabling the current flow 109 to continue completely around the blade 571. As the blade 571 extends from the leading end 62 of the turbine 500, the blade chord gradually increases in diameter as it approaches the central portion 586, over which it shall extend to its apex. As the blade 571 continues toward the trailing end 64 of the turbine 500, the blade chord gradually decreases in diameter. The blade 571 is preferably constructed from a "soft" material, such as Kevlar or a similar composite that will afford some flexibility in the body of the blade 571 and allow it to extend when it comes into contact with the current flow 109. This stretching or lengthening motion allows the blade 571 it to configure itself in its most efficient and sinuous shape, with minimum drag, within the current flow 109. This configuration advantageously results in maximum revolutions and torque to transfer upon the turbine 500. [0097] The blade 571 is coupled to shaft extensions 576 that project outwardly from the distal ends of the shaft 76. In this configuration, the bearings 580 are preferably configured so that they rotate together with the shaft extensions 576 and cause the body 570 of the turbine 500 to rotate. The bearing 580 at the leading end 62 of the turbine 500 is preferably a standard mechanical bearing. It is also desirable that one or more of the shaft extensions 576 is capable of expanding and retracting. The blade 571 preferably connects to the shaft extensions 576 a short distance from the leading end 62 and trailing end 64 of the body 570, and extends around the body at a predetermined distance above the external surface of the body 570. [0098] Figure 12A of the drawings shows the attachment of the forward shaft extension 576 to the mechanical bearing 580. Desirably, one or more of the shaft extensions 576 contains a single acting hydraulic cylinder mechanism 578 which can retract into a fixed position or extend to a variable position depending on the direction and strength of current flow 109 applied to the turbine 500. The extension and/or retraction of the shaft extensions 576 is preferably an automated process that is determined by changes in the strength and/or direction of the current flow 109. For example, if the current 109 is flowing in a given direction, the shaft extension WO 2013/110140 PCT/AU2013/000068 28 576 at the leading end 62 will retract, whereas the shaft extension 576 at the trailing end 64 will be extended. If the current flow 109 subsequently changes to flow in the opposite direction then the shaft extension 576 at the leading end 62 will switch to an extended position, whereas the shaft extension 576 at the trailing end 64 will retract. [0099] Figure 12B is a cross-sectional view of the spiral blade 571 shown in Figure 12, wherein the leading face has a gradual convex curve toward the current flow (along its chord 591) and, therefore, a rear face that is concave along the chord 591. Preferably, the blade 571 has, at its distal or leading edge, a bulb 572 or a formed hump that transcends and tapers downwards toward the root of the blade 571 in a teardrop type formation. It is also desirable that the bulb 572 be angled toward the current 109 at an angle of between about 70 to 80 degrees. Conversely, at the root of the spiral blade 571 a further distal edge bulb 593 shall angle away from the current 109 at an angle of between about 70 to 80 degrees. This configuration of the bulbs 572 allows the spiral blade 571 to become hydro-dynamically symmetrical and thus suitable for use in either uni-directional or bi-direction current flow 109. The bulbs 572 not only add considerable strength and power to the spiral blade 571 but also provide safety protection to marine life and protect the blade 571 from debris. [00100] Figure 13 of the drawings shows, by way of example, a venturi duct 99 (and internally housed turbine) deployed in an oceanic environment by attachment to a construction 108 (such as, for example, a sea platform) on the ocean surface that extends to the sea floor 110. A plurality of venturi ducts 99 and turbines can be configured, such as shown in Figure 13, in a linked configuration. Upon the surface of such a construction 108 may be a remote control centre 92 from which the command cables 96 and the AC current cables 98 originate. A further example, shown in Figure 13A of the drawings, shows a venturi duct 99 (and internally housed turbine) deployed in a river and retained within a current flow 109 via cables 105 that attach to an anchored structure 107 on the riverbed 210. In this configuration, the position of the venturi duct 99 is preferably indicated by a surface buoy 106. Stabilizing fins 104 help to trim the venturi duct 99 as it is positioned within the current flow 109. As can also be seen from Figure 13A, the insulated high voltage cables 97 can be run in tandem with the tethering cables 105 to the anchored structure 107, and then travel to a land based application such as an irrigation pump or electricity grid. There are a variety of different mooring options and configurations known in the art for securing and retaining venturi ducts within a current flow 109, and these will vary depending on the requirements of a given application.

WO 2013/110140 PCT/AU2013/000068 29 [00101] The word 'comprising', and forms of the word 'comprising', when used in this specification and in the claims is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. [00102] As the present invention may be embodied in several forms without departing from the essential characteristics of the invention, it should be understood that the above described embodiments should not be considered to limit the present invention but rather should be construed broadly. Various modifications, improvements and equivalent arrangements will be readily apparent to those skilled in the art, and are intended to be included within the spirit and scope of the invention.

Claims (1)

1. The claims defining the invention are as follows:

   1 A water turbine for electric power generation, said water turbine comprising:

   (a) a body having an internal cavity for housing a variable output generator, said body being rotatable about a central shaft; and

   (b) one or more turbine blades being adapted to engage an axial flow of water, said one or more turbine blades extending from a leading end of said body in one or more of:

   (i) a substantially helical configuration; and

   (ii) a downstream direction relative to said leading end, wherein in use, said one or more turbine blades channel said flow of liquid about said body such that said body is caused to rotate about said central shaft.

   2 The water turbine according to claim 1 , wherein said body comprises a leading portion adjacent said leading end, said leading portion having an increasing cross-sectional diameter as it extends from said leading end.

   3 The water turbine according to claim 2, wherein said body further comprises a central portion adjacent said leading portion.

   4 The water turbine according to claim 3, wherein said body further comprises a trailing portion adjacent said central portion, said trailing portion having a decreasing cross-sectional diameter as it extends away from said central portion.

   5 The water turbine according to claim 4, wherein each of said leading portion and/or said trailing portion has a substantially conical shape.

   6 The water turbine according to either claim 4 or claim 5, wherein said turbine blades extend along said leading portion and said central portion of said body.

   7 The water turbine according to claim 6, wherein said turbine blades also extend along said trailing portion of said body.

   8 The water turbine according to either claim 6 or claim 7, wherein the radial dimension of said turbine blades is greatest in an area about said central portion. 9 The water turbine according to any one of claims 6 to 8, wherein said turbine blades project axially outward from an outer surface of said body.

   10 The water turbine according to any one of claims 6 to 9, wherein the positioning of said turbine blades about said body is hydro-dynamically symmetrical to allow rotation of said body about said central shaft in either a clockwise or anti-clockwise direction.

   11 The water turbine according to any one of claims 6 to 10, wherein each of said turbine blades comprises a distal edge, said distal edge having a bulb or tear shaped cross-section.

   12 The water turbine according to claim 11, wherein said distal edge incorporates serrations or ridges that extend along at least a portion of said distal edge.

   13 The water turbine according to any one of claims 6 to 12, further comprising a plurality of secondary turbine blades positioned between said turbine blades.

   14 The water turbine according to claim 13, wherein said secondary turbine blades project radially outward from one or more of said leading portion, said central portion, or said trailing portion.

   15 The water turbine according to either claim 13 or claim 14, wherein said secondary turbine blades are substantially rectangular in shape.

   16 The water turbine according to any one of claims 4 to 15, wherein said trailing portion is separated from said central portion of said body such that said trailing portion does not define said internal cavity.

   17 The water turbine according to any one of claims 4 to 16, wherein said trailing portion is adapted to rotate about said central shaft in an opposing direction to said leading portion and said central portion.

   18 The water turbine according to either claim 16 or claim 17, wherein said trailing portion comprises opposing turbine blades that extend axially outward from said trailing portion.

   19 The water turbine according to claim 18, wherein in use said opposing turbine blades channel said flow of liquid about said trailing portion such that said trailing portion body is caused to rotate about said central shaft in an opposing direction to said leading portion and said central portion. 20 The water turbine according to any one of claims 16 to 19, wherein said trailing portion comprises a further internal cavity.

   21 The water turbine according to claim 20, wherein said internal cavity and/or said further internal cavity contain buoyant material which in use allows said water turbine to attain:

   (a) neutral buoyancy;

   (b) positive buoyancy; or

   (c) negative buoyancy.

   22 A variable output generator for use with a water turbine according to any one of claims 1 to 21, said variable output generator comprising:

   (a) a plurality of magnetic members positioned around an inner surface of said internal cavity in a circular configuration, said magnetic members being rotatable about said central shaft in response to rotation of said body;

   (b) a shaft sleeve positioned about said central shaft, said shaft sleeve being movable along said central shaft in a longitudinal direction; and

   (c) at least one stator arm connected to said shaft sleeve, said stator arm having a distal end and a plurality of field windings positioned thereon, wherein said shaft sleeve is movable along said central shaft to align said field windings on said stator arm with said plurality of magnetic members, and to control the generation of electric power from said variable output generator.

   23 The variable output generator according to claim 22, wherein said plurality of magnetic members are arranged to form one or more rings of magnetic members, wherein said magnetic members in each of said rings are evenly spaced around said inner surface of said internal cavity.

   24 The variable output generator according to claim 23, wherein said plurality of magnetic members are arranged to form three rings of magnetic members, wherein said magnetic members in each of said rings are evenly spaced around said inner surface of said internal cavity. 25 The variable output generator according to either claim 23 or claim 24, wherein said distal end of said stator arm comprises one or more prongs upon which said plurality of field windings are mounted.

   26 The variable output generator according to claim 24, wherein said distal end of said stator arm comprises three prongs upon which said plurality of field windings are mounted.

   27 The variable output generator according to claim 26, wherein in use each of said three prongs can be aligned with one of said rings of magnetic members by controlling movement of said shaft sleeve along said central shaft.

   28 The variable output generator according to any one of claims 25 to 27, wherein when said prongs are aligned with said rings of magnetic members, said rings of magnetic members are sufficiently spaced apart from said prongs to allow for generation of electric power by said variable output generator by inducing an AC voltage in said plurality of field windings.

   29 The variable output generator according to any one of claims 22 to 28, wherein said shaft sleeve is movable along said central shaft by one or more of a servo motor, and an actuated circuit.

   30 The variable output generator according to any one of claims 22 to 29, further comprising:

   (a) a water inlet located in a leading portion of said central shaft to allow water to enter said internal cavity; and

   (b) a water outlet located in a trailing portion of said central shaft to allow water to exit said internal cavity, wherein in use, said water inlet allows said internal cavity to become partially or completely filled with water so as to cool said plurality of magnetic members and/or said field windings.

   31 A venturi duct for housing a water turbine according to any one of claims 1 to 21, said venturi duct comprising:

   (a) an inlet for receiving said flow of water, said inlet including a circular inlet opening; (b) an outlet for discharging said flow of water received by said inlet, said outlet including a circular outlet opening having a greater diameter than said circular inlet opening; and

   (c) a support means attached to said central shaft of said water turbine, said support means being adapted to maintain said central shaft in a substantially stationary position, wherein in use, said venturi duct channels and accelerates said flow of water across said water turbine.

   32 The venturi duct according to claim 31, wherein said support means comprises:

   (a) a first support strut positioned across said inlet opening, said first support strut being attached to a leading end of said central shaft; and

   (b) a second support strut positioned across said outlet opening, said second support strut being attached to a trailing end of said central shaft.

   33 The venturi duct according to either claim 31 or claim 32, further comprising chambers and/or nacelles containing buoyant material which in use allow said venturi duct to attain:

   (a) neutral buoyancy;

   (b) positive buoyancy; or

   (c) negative buoyancy.

   34 The venturi duct according to claim 33, wherein said chambers and/or nacelles allow said venturi duct to be aligned within said flow of water.

   35 The venturi duct according to any one of claims 31 to 34, further comprising detachable counterweights which in use allow said venturi duct to attain:

   (a) neutral buoyancy;

   (b) positive buoyancy; or

   (c) negative buoyancy. 36 The venturi duct according to any one of claims 31 to 35, further comprising one or more stabilising fins attached to an external surface of said venturi duct, said stabilising fins being adapted to align and stabilize said venturi duct within said flow of water.

   37 The venturi duct according to any one of claims 31 to 36, further comprising a filtering screen positioned across said inlet opening to prevent debris and/or marine life from entering said venturi duct.

   38 The venturi duct according to claim 37, wherein said filtering screen projects outwardly from said inlet opening and has either a cone or semi- spherical shape.

   39 A generator cooling system for use with a variable output generator according to any one of claims 22 to 29, said system comprising:

   (a) a water inlet located in a leading portion of said central shaft to allow water to enter said internal cavity;

   (b) a water outlet located in a trailing portion of said central shaft to allow water to exit said internal cavity;

   (c) one or more control valves located at each of said water inlet and said water outlet;

   (d) one or more temperature and/or pressure sensors located within said internal cavity, wherein in use, said sensors monitor operating conditions within said internal cavity and control the flow of water into and out of said internal cavity via said water inlet and said water outlet by opening and/or closing said control valves.

   40 The generator cooling system according to claim 39, further comprising a

   microprocessor connected to said sensors and said control valves, wherein said microprocessor transmits signals to said control valves based upon data received from said sensors.

   41 The generator cooling system according to claim 40, wherein said signals cause said control valves to either open or close.

   42 The generator cooling system according to either claim 40 or claim 41, wherein said microprocessor is part of a remotely located control system. 43 The water turbine according to any one of claims 1 to 21, wherein in use said water turbine is tethered to a support structure using securing means to retain and stabilize said water turbine within said flow of water.

   44 The water turbine according to claim 43. wherein said support structure is located on one or more of:

   (a) an ocean floor;

   (b) a river bed;

   (c) a sea vessel; or

   (d) a buoy.

   45 The water turbine according to either claim 43 or claim 44, wherein said securing means is a cable.