The present invention relates generally to wind turbines, in particular, to Savonius rotors, modules involving such rotors, installations thereof and applications thereof.

Savonius wind rotors, and associated wind turbine systems, have been known ever since S.J. Savonius first described and patented his system in the 1920's. Exemplary patents issued to Savonius include US1766765 and US1679574, which relate to two oppositely arranged hollow-shaped vanes of generally rectilinear generatrix formed by cylindrical, parabolic, helical or other suitable surfaces and arranged so that the inner edge of the vane extends to the segmental space bordered by the other vane, both said vanes overlapping each other at their inner edges and forming a gap or air passage adapted to force the air current from the hollow side of one vane to the hollow side of the other vane in an S-like path of substantially constant area.

Since that original design, various modifications and improvements have been attempted, but none so far have successfully managed to improve the efficiency of the Savonius rotor, which is limited by a number of factors, not least of which the drag that operates on the return blade or vane as it comes around the axis of rotation to face into the oncoming flow of fluid, which in the majority of cases, is air, as Savonius turbines have mainly been used in the past to produce energy from a flow of air that impinges, or is incident on the vanes or blades of the rotor.

A publication by M.H. Mohamed et al, in Energy Conversion and Management, vol. 52, 2011, pages 236-242, mentions the background of Savonius wind turbines, and the well-known poor efficiency of the system as a whole. This lists some of the known solutions for improving efficiency in Table 1, and goes on to deal with the theoretical optimisation of a Savonius rotor system using computer processing and an obligatory obstruction plate placed between the oncoming incident wind flow and the return blade. Although mention is made of an optimized shape for the blade, this shape is not actually described, and also is necessarily made by factoring in the presence of the obstruction plate.

Additionally, the calculations are made assuming a blade thickness of 2 mm. The authors of the paper use their own algorithms, including evolutionary algorithms, and computational setup to effect the calculations, but these are not revealed or disclosed. A schematic drawing of the profile of the computer optimized blade in the presence of an obstructor plate is given on page 241.

Despite the account of theoretical details given in the above article, the absence of widespread usage of the Savonius principle in energy generation is a strong indication that the known limitations of reduced efficiency of these systems has not yet been overcome. This has therefore also become a long-felt, unsatisfied need within the market place.

The present invention is geared to overcoming the known limitations of reduced efficiency present in existing systems and satisfying that long-felt need. Consequently, it is an object of the present invention to provide a modified Savonius rotor which is capable of meeting this need and overcoming existing prejudices in regard to the Savonius technology. This rotor can then be formed into modules, assemblies of modules, and installations incorporating said modified Savonius rotors, and has further applications as will be defined hereinafter.

Accordingly, one object of the invention is a Savonius rotor, comprising an axis of rotation positioned orthogonally to the direction of a fluid flowing towards and around it, and at least a first blade and at least a second blade, the blades being symmetrically located around said axis of rotation without being directly attached to said axis, thereby providing a central fluid passage for passage of fluid between said at least first and said at least second blade and around the axis of rotation, wherein:

- each said blade comprises a longitudinal axis which is parallel to said axis of rotation, a leading edge located at a point furthest away from said axis of rotation of said blade and a trailing edge located at a point closest to said axis of rotation;

- each said leading edge and said trailing edge define a peripheral surface located around said longitudinal axes of said blades;

- each said peripheral blade surface comprises a front face, and a rear face, the front face extending from said leading edge towards said trailing edge and being defined by a first spline curve having a first plurality of contiguous radii of curvature, the rear face extending from said trailing edge towards said leading edge and being defined by a second spline curve having a second plurality of contiguous radii of curvature, said second spline curve being different to said first spline curve;

- each blade comprising a respective height of said front face and a respective height of said rear face; - wherein each said front face height, rear face height, first spline curve and second spline curve define a blade volume that is configured to optimize transfer of energy from the fluid flowing onto and around each said blade.

It should be noted that most of the known prior art solutions only relate to a thin blade profile shape, and not blade volume, or the peripheral surface defined by that volume. The applicant of the present invention has determined that it is advantageous to provide three-dimensional volume to the blades of the Savonius rotor, beyond the usual 2 or 3 mm thick profiles that are used in the prior art because a full-bodied blade, i.e. a blade having an aerodynamic volumetric profile and associated volume greater than that provided for by the 2 to 3 mm thickness of the known prior art blades, displays a generally curved, or rounded surface which avoids a sudden drop in air circulation around the blade, and in particular reduces air flow drop as air flows around the body of the blade. Known Savonius blade shapes cause air flow to be disrupted around their edges because of their minimal thickness, which also results in less efficient extraction and consequent transmission of energy to the blade from said air flow. Furthermore, the rounded volumetric surfaces of the Savonius blades of the present invention, with their increased volume when compared to those known in the prior art, have unexpectedly been found to not only slow air flow onto the blade, but also at the same time increase guidance of air flows around the blade and into the central passageway between a pair of blades. Another unforeseen advantage of the shape and volumetric profile of the Savonius blades of the present invention is that such blades are also resistant to much stronger wind speeds than Savonius blades that are only approximately 2 mm thick. Indeed, the blades of the present invention are able to function in windspeeds up to, or less than 30 m/s.

According to another object of the present invention, the peripheral surface of the blade is continuous. In an alternative embodiment of the invention, the peripheral surface of the blade is discontinuous.

According to yet another alternative embodiment of the invention, the peripheral surface of the blade is discontinuous, and comprises a plurality of substantially vertical individually orientable or modulable surfaces, arranged along said first and said second spline curves.

According to a further embodiment of the invention, the blade volume is hollow, or substantially hollow. When reference is made to a hollow volume, it is to be understood that although the peripheral surface of the blade can be continuous, the inner volume defined by that peripheral surface can be hollow, or empty, or substantially hollow, e.g. it could include support struts, or a honeycomb structure, as is known in the art for composite three dimensional structures that require resilience and mechanical strength, as well as low densities, such as in the manufacture or aircraft parts, or some automobile components. Alternatively, or additionally, the blades could be made of extruded or moulded material.

Preferably, however, and according to an advantageous embodiment of the invention, the blade volume is solid, or substantially solid. The materials used to make such blades, or fiU the volumes of the blades according to the invention can advantageously be selected from the group consisting of plastic materials such as polyamide, ABS, high density polyethylene, high density polypropylene, polyurethane foam, and metals, such as extruded aluminium, or stainless steel. For example, it is possible to make a substantially hollow, curved volumetric profile blade body according to the present invention out of stainless steel of approximately 0.4mm thickness. Preferably, in the case where the blades according to the invention are hollow, the latter are provided with an additional covering layer of material, identical to, or different from, the material of the blade, in areas where said blade is provided with perforations adapted to receive optional linking members as described hereinafter. Alternatively, instead of an additional covering layer as described above, the blade could be made of areas of material having a greater density around any such perforations than the density of the remainder of the blade material.

According to still yet another embodiment of the invention, the blade has a substantially comma- shaped configuration. The applicant has determined that this general comma shape is particularly adapted to improving the energy efficiency of such Savonius rotors. As will become apparent in the detailed description of the invention, the generally comma-shaped blades are more particularly defined in an optimal way.

According to a further embodiment of the invention, the blade has a substantially comma-shaped configuration with a tail and a head, wherein the head of the comma is located near to the axis of rotation, and the tail of the comma is located at a spaced apart distance therefrom towards a periphery of the rotor. According to still yet another embodiment of the invention, the central fluid passage is substantially "S"-shaped, wherein said "S" is defined by at least two outer spline curves having a plurality of contiguous radii of curvature, wherein each outer spline curve of said "S" is identical to the spline curve of the rear face of the blade.

According to a further embodiment of the invention, the modified Savonius rotor further comprises at least a first plate flange, attached to and freely rotatable around the axis of rotation, wherein said first plate flange covers said at least first and said at least second blades.

In yet another embodiment of the invention, the modified Savonius rotor further comprises a first plate flange and a second plate flange, said first plate flange and said second plate flange covering a respective top and bottom of said said first and second blades, thereby sandwiching said first and second blades between said first and second plate flanges.

According to still yet another embodiment of the invention, the modified Savonius rotor further comprises at least two linking members separate from the axis of rotation which link said first and second plate flanges to each other and a respective each one of said blades.

According to a preferred embodiment of the invention, each blade has a height which is less than a maximum diameter of the rotor and wherein a ratio of blade height to maximum rotor diameter is comprised between about 0.4:1 to 0.6:1.

According to a more preferred embodiment of the invention, the leading edge of the blade has a substantially angular dihedral shape with an angle comprised between 30 degrees and 34 degrees, preferably 32 degrees.

In a further embodiment of the invention, the trailing edge has a substantially rounded shape, and preferably is substantially hemi-cylindrical in shape.

In another embodiment of the invention, the first spline curve defining the front face is substantially convex.

In a further embodiment of the invention, the second spline curve defining the rear face is substantially concave. According to still yet another embodiment of the invention, the spline curve defining the front face extends from the leading edge towards the trailing edge, and comprises:

- a first arc, defining a cylindrical surface of nominal radius Rn, substantially equal to the distance between the axis of rotation and the leading edge, and extending along said cylindrical surface over a distance LI, substantially equal to just over a quarter of the circumference generated by a complete rotation of the leading edge around the axis of rotation where LI = (Rn*2*pi)*(106°/360°).

According to a further embodiment of the invention, the spline curve defining the front face extends from the leading edge towards the trailing edge, and comprises:

- a second quasi-cylindrical arc connected tangentially and continuously to said first arc, said second arc having a radius R2 comprised between about Rn/6 and Rn/5, and extending along said quasi- cylindrical surface over a distance L2, substantially equal to (Rn/5*2*pi)*(A°/360°) where A° is comprised from 44° to 46°, preferably 45°.

According to still yet another embodiment of the invention, the spline curve defining the front face extends from the leading edge towards the trailing edge, and comprises:

- a third arc connected tangentially and continuously to said second arc, said third arc having a radius R3 substantially equal to the nominal radius Rn and extending along said peripheral surface over a distance L3, where L3 = (Rn*2*pi)*(B°/360°), where B° is comprised from 39° to 41°, preferably 39°.

In another embodiment of the invention, the spline curve defining the front face extends from the leading edge towards the trailing edge, and comprises: - a fourth arc, connected tangentially and continuously to said third arc, said fourth arc having a substantially hemi-cylindrical surface, and constituting the trailing edge of radius R4.

According to another embodiment of the invention, the fourth arc of the spline curve defining the trailing edge is adjustably defined to enable connection between the first spline curve and the second spline curve at the trailing edge. In a further embodiment of the invention, the spline curve defining the rear face extends from the trailing edge towards the leading edge, and comprises:

- a sixth substantially cylindrical arc of radius R6, substantially equal to Rn*(24/25), and extending along said peripheral surface over distance L6 approximately equal to (Rn*(24/25)*2*pi)*(C°/360°), where C° is comprised from about 58° to 60°, preferably 58°. According to still yet another embodiment of the invention, the spline curve defining the rear face extends from the trailing edge towards the leading edge, and comprises:

- a fifth substantially cylindrical arc of radius R5, connected tangentially and continuously to said sixth arc, where R5 is approximately equal to Rn*(ll/25), and extending along said peripheral surface over a distance L5 approximately equal to (Rn*(ll/25)*2*pi)*(D°/360°), where D° is comprised from about 59° to about 61°, preferably 60°.

In yet another embodiment of the invention, the rotor is mounted non-movably onto a transmission axle, said axle having an axis of rotation coincident with the axis of rotation of the rotor.

A further embodiment of the invention is a Savonius rotor module, comprising at least a first and at least a second Savonius rotor according to any one of the preceding claims, each rotor being positioned along said transmission axle, wherein the leading edge and trailing edge of the blades of the second rotor are positioned in angular displacement around the transmission axle with respect to the leading edge and trailing edge of the blades of the first rotor.

According to still yet another embodiment of the invention, the leading edge and trailing edge of the blades of the second rotor are displaced by 90° around the transmission axle with respect to the leading edge and trailing edge of the blades of the first rotor. In yet another embodiment of the invention, said module comprises more than two rotors, and preferably is selected from the group consisting of two, four, six, and eight rotors.

According to a further embodiment of the invention, the rotor module further comprises at least one linking member separate from the transmission axle, which links the plate flanges of said first rotor to the plate flanges of said second rotor.

In yet another embodiment of the present invention, a Savonius rotor module assembly is provided, comprising a plurality of rotor modules, mounted on a single transmission axle.

According to a further embodiment of the invention, said module assembly further comprises a discoid generator connected to the transmission axle. In yet another embodiment according to the present invention, a Savonius wind turbine installation is provided, comprising at least a first and a second Savonius rotor module, each module being assembled in a parallel configuration assembly, located within a mounting frame.

According to a further embodiment according to the present invention, each rotor module is kinetically connected to another rotor module via at least one transmission belt connected respectively between each transmission axle.

In yet another embodiment according to the present invention, the at least one transmission belt is a toothed belt.

In still another embodiment according to the present invention, the at least one transmission belt is a chain belt. In a further embodiment according to the present invention, the installation further comprises at least one fixed fluid deflector located in the fluid flow path parallel to the axis of rotation of the rotors between a respective pair of rotor modules.

In another embodiment according to the present invention, the fluid flow deflector has an "S"-shaped profile. In still yet another embodiment according to the present invention, the substantially "S"-shaped profile of the fluid flow deflector is configured to create a zone of higher fluid pressure on the front face side of the blade, and an area of lower fluid pressure on the rear face side of the blade.

In another embodiment according to the present invention, the Savonius wind turbine installation is assembled to form a windbreak. Accordingly, a further embodiment of the present invention is a windbreak comprising a mounting frame and at least a first and at least a second wind rotor module, assembled in parallel within the mounting frame.

In yet another embodiment according to the present invention, the windbreak further comprises at least a first fluid flow deflector, extending from a lower part of said mounting frame in an oblique plane groundwards, and configured to deflect an oncoming incident fluid flow upwards from the ground towards the wind turbine modules.

According to another embodiment according to the present invention, the windbreak further comprises at least one attachment means for attaching said frame to the ground. In yet another embodiment according to the present invention, the windbreak further comprises at least a second fluid flow deflector, extending from an upper part of said mounting frame in an oblique plane skywards, and configured to deflect an oncoming incident fluid flow downwards towards the wind turbine modules.

In yet a further embodiment according to the present invention, the windbreak further comprises at least one lateral fluid flow deflector, mounted on a vertical upright of said mounting frame, extending from said upright in an oblique plane outwards, and configured to deflect an oncoming incident fluid flow inwards towards the wind turbine modules.

The present invention and various embodiments will now be described in further detail according to non-limitative examples, and in reference to the accompany figures, in which: Figure 1 is a schematic f lse perspective representation of a pair of Savonius blades used in a Savonius rotor according to the present invention, wherein the blades have a volume and a generally curved volumetric profile as will be described hereinafter;

Figure 2 is a schematic false perspective representation of an alternative Savonius blade suitable for use in a Savonius rotor according to the present invention and illustrating a modified blade volume and volumetric profile;

Figure 3 is a schematic top down representation of the detail of the curved profile of a Savonius blade used in a Savonius rotor according to the present invention;

Figure 4 is a schematic top down representation of two pairs of Savonius blades superposed one on top of the other, as can be found in a Savonius rotor module according to the present invention, wherein a second Savonius rotor has a pair of blades that are anglularly displaced with respect to a first Savonius rotor;

Figure 5 is a schematic exploded false perspective representation of a series of flange plates and linking members used to form a Savonius rotor module according to the present invention, minus any Savonius blades; Figure 6 is a schematic exploded false perspective representation of another series of flange plates and linking members used to form a Savonius rotor module according to the present invention, the Savonius rotor blades being sandwiched between corresponding flange plates, and the module being linked together by linking members;

Figure 7 is a schematic false perspective representation of the modified Savonius rotor blade of Figure 2, encased by correspondingly modified flange plates;

Figure 8 is a schematic false perspective representation of the modified Savonius rotor blade of Figure 2 and Figure 7, in an assembly to form a turbine unit made up of four pairs of blades.

Figures 9a and 9b are schematic top down representations of two Savonius rotors in a parallel, side-by- side configuration with a deflector located between each pair of blades; Figure 10 is a schematic false perspective representation of a deflector of the type illustrated in Figures 9a and 9b;

Figure 11 is a schematic false perspective representation of an assembly of Savonius rotors according to the present invention, wherein three rotor modules of two rotors each are mounted vertically, and then in a parallel, or side-by-side configuration, forming a Savonius turbine array or assembly; Figure 12 is a schematic front view representation of a windbreak comprising an assembly of Savonius rotor modules as illustrated in Figure 11, mounted in a chassis attached to a ground or other substantially planar surface;

Figure 13 is a schematic side view representation of the windbreak of Figure 12;

Figure 14 is a schematic false perspective representation of a larger windbreak similar to that represented in Figures 11 and 12.

Turning now to Figure 1, a Savonius rotor according to the invention and generally indicated by the reference numeral 1 is presented in false perspective view. The rotor (1) comprises an axis of rotation (2) positioned orthogonally to the direction of a fluid flowing towards and around it, for example, the wind, or an air flow (5), represented by grouped triple arrows, and at least a first blade (3) and at least a second blade (4), the blades (3, 4) being symmetrically located around said axis of rotation (2) without being directly attached to said axis (2), thereby providing a central fluid passage for passage of fluid between said at least first and said at least second blades (3, 4) and around the axis of rotation (2). Each said blade (3, 4) comprises a longitudinal axis (6, 7) which is parallel to said axis of rotation (2), a leading edge (8, 10) located at a point furthest away from said axis of rotation (2) of said blade (3, 4) and a trailing edge (9, 11) located at a point closest to said axis of rotation (2). Additionally, each said leading edge (8, 10) and said trailing edge (9, 11) define a peripheral surface (12, 13, 14, 15) located around said longitudinal axes (6, 7) of said blades (3, 4). Each peripheral blade surface comprises a front face (12, 13), and a rear face (14, 15), the front face (12, 13) extending from said leading edge (8,

10) towards said trailing edge (9, 11) and being defined by a first spline curve (SI) having a first plurality of contiguous radii of curvature, the rear face (14, 15) extending from said trailing edge (9,

11) towards said leading edge (8, 10) and being defined by a second spline curve (S2) having a second plurality of contiguous radii of curvature, said second spline curve (S2) being different to said first spline curve (SI). Each blade (3, 4) comprises a respective height (Hf) of said front face (12, 13) and a respective height (Hr) of said rear face (14, 15). The relative front face height (Hf), rear face height (Hr), first spline curve (SI) and second spline curve (S2) define a blade volume (Vb) that is configured to optimize transfer of energy from the fluid, for example, the wind, flowing onto and around each said blade (3, 4). Viewed from above, the modified Savonius blade resembles a comma, and has a generally comma-shaped outer profile, with a tail and a head, wherein the head of the comma is located near to the axis of rotation (2), and the tail of the comma is located at a spaced apart distance therefrom towards a periphery of the rotor.

In the modified Savonius blade illustrated in Figure 1, the front (12, 13) and rear faces (14, 15)have continuous surfaces, i.e. they form a single continuous peripheral surface. In an alternative, and non- illustrated embodiment, one can provide a series of discrete surfaces, the orientation or presentation of which can be controlled, either manually, or remotely using a system of coordinated micromotors. For example, one can provide a series of substantially vertical surfaces aligned in parallel, along either or both of the spline curves of the front and rear faces, either vertically or horizontally, similar to shutters. The shutters can be mounted on rotatable axes, coupled to coordinated and independently powered micromotors, enabling the surface profile to be adapted or modified with increased precision in order to take account of particular wind conditions or currents, or in response to a given airflow or to produce a particular airflow, through the Savonius rotor.

The Savonius blade used to form a Savonius rotor according to the present invention has a significantly greater body volume than any of the Savonius blades currently known, and furthermore defines a volumetric profile which will be explained in more detail hereinafter. The volume of the blade can be substantially comprised of solid material, or alternatively, can be partly, substantially or even completely hollow. The materials suitable for the manufacture of such a blade are known per se to the skilled person, and can comprise materials such as metals, and metal alloys, plastic or polymer materials, these materials being suitably shaped or formed to create the blade and blade body. For example, composite materials, such as moulded foamed polymers, or metallic bodies, e.g. made of aluminium and other lightweight metals, formed for instance into honeycomb structures, as used in the aircraft and vehicle manufacturing industries, can be used to provide lightweight, but sufficiently mechanically resistant, modified Savonius blades of appropriate volume according to the present invention.

Each blade generally has a height which is less than a maximum diameter of the rotor and wherein a ratio of blade height to maximum rotor diameter is comprised between about 0.6 to 1 and 0.4 to 1. In other words, the blade has a height (Hf, Hr) which is less than the maximum rotor diameter according to the ratio indicated above. This has been determined to offer the optimum ratio of height to width of the rotor in order to provide the most efficient conversion of wind or air flow into torque used to drive a drive mechanism and produce mechanical energy which can be stored as electricity, and also represents a difference with the known Savonius blades, which tend to have a height equal to, or greater than, the total diameter of the rotor. Typically, the leading edge of the blade has a substantially angular dihedral shape with an angle comprised between 30 degrees and 34 degrees, and more preferably 32 degrees and the trailing edge has a substantially rounded shape, and more preferably is substantially hemi-cylindrical in shape. As is apparent from the example drawing of Figure 1, the first spline curve (SI) defining the front face is substantially convex, and the second spline curve (S2) defining the rear face is substantially concave, both faces meeting respectively at the leading and trailing edges (8, 9).

As can also be seen from Figure 1, the Savonius rotor has a central fluid passage (18) which is substantially S-shaped. In this case, the S-shaped passage (18) is defined by at least two outer spline curves having a plurality of contiguous radii of curvature, wherein each outer spline curve of said "S" is identical to the spline curve of the rear face (14, 15) of the blade. In other words, the shapes of the spline curves of the rear faces define the shape, curvature and limits of the S-shaped passage (18).

Considering now Figure 2, a false perspective representation of an alternative blade shape is illustrated, where like numerals references like elements of the blade described for Figure 1. The most notable differences between the blades of Figure 1 and that illustrated in Figure 2, is that the outer profile has been modified to produce a smaller volume of blade, hence offering increased performance, wherein the front and rear surfaces are indicated, and it is clear that the front surface has been shaped (17a, 17b) to form a front face that resembles that of a the leading face of an aircraft wing. Dotted lines 16a and 16b illustrate the original edge curve of the front face (12), to indicate more clearly where matter has been removed from the blade. This alternative embodiment according to the invention is advantageous because the corresponding profile significantly reduces, or completely removes, the cause of turbulence as air flows through the rotor, over the surface of the blades and through the central air flow passage of the rotor. By removing turbulence caused by the angular edges of the edge curves (16a, 16b), at the entrance to the central "S"-shaped passageway, overall performance of the rotor is significantly improved. By the same token, removal of the extra material of the blade as illustrated by the shape thereof in Figure 2, leads to an increase in pressure at the entrance to the central passageway, and a corresponding increase in air flow through said passageway, which translates to increased kinetic energy transmission.

Looking at Figure 3, further details of the spline curves (SI, S2) defining the front (12, 13) and rear faces (14, 15) of the modified Savonius blade are illustrated, and which correspond to optimum profiles, as determined by the applicant, in terms of conversion of fluid flow speed into torque, on the one hand, and the creation of an area of higher pressure in front of the the front surface (12, 13), and lower pressure behind the rear surface (14, 15), thereby maximising the speed of rotation of the Savonius rotor. The axis of rotation (2) of the modified Savonius rotor is indicated, as are several dotted lines, illustrating various arcs of the spline curves in accordance with the invention to define a particularly advantageous blade profile.

In Figure 3, the spline curve (SI) defining the front face (12, 13) extends from the leading edge (8) towards the trailing edge (9), and comprises a first arc (19), defining a cylindrical surface of nominal radius Rn, substantially equal to the distance between the axis of rotation (2) and the leading edge (8), and extending along said cylindrical surface over a distance LI (8-20), substantially equal to just over a quarter of the circumference generated by a complete rotation of the leading edge around the axis of rotation where LI = (Rn*2*pi)*(106°/360°), corresponding to an angle A of approximately 106°.

The spline curve (SI) further comprises a second quasi-cylindrical arc (21) connected tangentially and continuously to said first arc (19), said second arc (21) having a radius R2 comprised between about Rn/6 and Rn/5, and extending along said quasi-cylindrical surface over a distance L2 (20-22), substantially equal to (Rn/5*2*pi)*(D°/360°) where D° is comprised from 44° to 46°, and is preferably 45°. The spline curve (SI) further comprises a third arc (23) connected tangentially and continuously to said second arc (21), said third arc (23) having a radius R3 substantially equal to the nominal radius Rn and extending along said peripheral surface over a distance L3 (22-24), where L3 =

(Rn*2*pi)*(E ^< 7360°), where E° is comprised from 39° to 41°, preferably 39°. The spline curve (SI) further comprises a fourth arc (25), connected tangentially and continuously to said third arc (23), said fourth arc (25) having a substantially hemi-cylindrical surface, and constituting the trailing edge (9) of radius R4, extending along said peripheral surface over a distance L4 (24-26). This fourth arc (25) of the spline curve (SI) defining the front face (12, 13) can be adjusted so as connect the first spline curve (SI) to the second spline curve (S2) at the trailing edge (9). The spline curve (S2) defining the rear face (14, 15) extends from the leading edge (8) towards the trailing edge, and comprises a fifth substantially cylindrical arc (27) of radius R5, connected tangentially and continuously to said first arc (19), where R5 is approximately equal to Rn*(ll/25), and extends along said peripheral surface over a distance L5 (8-28) approximately equal to

(Rn*(ll/25)*2*pi)*(B ^o /360°), where B° is comprised from about 59° to about 61°, and is preferably 60°.

Additionally, the spline curve defining the rear face (14, 15) comprises a sixth substantially cylindrical arc of radius R6, substantially equal to Rn*(24/25), and extending along said peripheral surface over distance L6 (26-28) approximately equal to (Rn*(24/25)*2*pi)*(C°/360°), where C° is comprised from about 58° to 60°, and is preferably 58°. As can be understood from the preceding description of Figure 3, the front face (12, 13) has four arcs (19, 21, 23, 25) that define the spline curve (SI) of the front face, and two arcs (27, 29) that define the spline curve (S2) of the rear face.

Figure 4 shows a top down illustration of two superimposed modified Savonius rotors forming a rotor module, each rotor having a pair of blades (30, 31) and (32, 33), wherein the blades of each rotor are located in angular displacement about the axis of rotation (2), one (30, 31) with regard to the other (32, 33). In the figure, the angular displacement, or rotation, of one rotor with regard to the other, about the axis of rotation (2), is 90°, but other intermediate angles can be chosen dependent on the desired configuration of the rotors, for example, angles of 1°, 2°, 3°, 4°, 5°, 6°, 8°, 9°, 10°, 12°, 15°, 18°, 20°, 24°, 30°, 36°, 40°, 45°, 60°, 72°, 90°, and 120° are all suitable angles of displacement for rotors which have pairs of blades. Alternatively, where the number of blades per rotor is greater than two, say three or four or more blades per rotor, the angles of displacement are calculated accordingly in a manner known per se. Figure 4 also shows a series of perforations or bores (34, 35, 36) made in the upper and lower surfaces of the blades (30, 31, 32, 33). When the blades are not hollow, or partly or substantially hollow, said perforations extend through the volume of material making up the blade. The bores enable insertion of linking members as described hereinafter to permit linking the various rotors with each other to form a more solid structure, and convert the rotors into a rotor module, or rotor assembly. As is apparent from Figure 4, the angular displacement of a lower blade with regard to an upper blade further facilitates reinforcement of the rotor modules, which may preferably comprise one, two, three or four Savonius rotors in vertical alignment, because some of the lower rotor's perforations are aligned so that they coincide with some of the perforations of the upper rotor in accordance with said angular displacement. In Figure 4, one can see that perforation or bore (34) near the leading edge of one upper rotor is aligned with a corresponding bore (34) located in angular displacement such that part of the front of the lower rotor's blades overlaps with the upper rotor's blades, enabling a linker element to be passed therethrough.

This is also illustrated in Figures 5 and 6, in which the modified Savonius rotor further comprises at least a first plate flange (37), attached to and freely rotatable around the axis of rotation (2), said first plate flange (37, 38, 39, 40, 41) covering the first and second blades of the rotor. Figure 5 does not show the blades to facilitate comprehension of the rotor module, and illustrates a module that would contain four Savonius rotors, each rotor having a pair of blades as described above, whereas Figure 6 illustrates a rotor module containing two Savonius rotors sandwiched between respective flange plates (37, 38, 39), of which there are three in total. The plates are preferably made of a deformation resistant material, for example, sheet steel, or sheet aluminium, optionally galvanized or otherwise chemically or physically coated to protect it from the ravages of the environment.

The flange plates (37, 38, 39, 40, 41) are linked together via linking members (42, 43), whereby linking members (42) link a pair of flange plates around a single Savonius rotor containing a pair of blades, and linking members (43) link all of the flange plates in the rotor module together from top to bottom, and further strengthen the whole structure against deformations due to torque and air flow speed. The linking members (42, 43) are held in place by corresponding fixation means, for example, nuts (44), which can be threaded to match a corresponding thread provided on the peripheral surface of the linking members. Alternative means of fixation of the linking members to the flange plates are also naturally within the reach of the skilled person, and equivalents thereto foreseen as valid alternatives. The at least two linking members (42, 43) are physically separate, and distanced apart, from the axis of rotation (2), and also distinct from a transmission axle (45) provided coaxially with the axis of rotation (2). The linking members can be made of any suitably resistant material, for example, stainless steel, or any other material that offers equivalent mechanical resistance at preferably no extra weight per unit length, or even more preferably, a material lighter than steel, and showing the same, or better mechanical resistance. The linking members are subjected to quite extreme stresses, and as they are caused to rotate along with the rotors, about the axis of rotation, and so it is preferable that the material used for the linking members be sufficiently mechanically resistant to resist the strains and stresses put on them, and to avoid early wear, corrosion or degradation. In particular, where the Savonius rotors are intended to be used in marine environments, i.e. near the sea in tropical areas, then the materials making up the blades, rotors, plates, linking members and other constitutional parts should all be resistant at least partly to the effects of such a marine or tropical environment.

In the exploded view of Figure 6, a rotor module containing two Savonius rotors is illustrated, whereby each rotor contains a pair of blades (30, 31) and (32, 33) is sandwiched between a total of three flange plates (37, 38, 39). The top (37), middle (38) and bottom (39) flange plates are held together by linking member (43) which is threaded (47) at its upper and lower extremities. In this Figure, only one such linking member is shown, although it should be understood that the rotor module comprises at least two such linking members, and preferably four or more such linking members. The linking member passes through upper flange plate (37), a bore (34) of a blade (31) of the first rotor, the middle flange plate (38), a corresponding bore (34) of a blade (33) of the second rotor, and the lower flange plate (39), and is all held in place by nuts (44) and corresponding washers (46) that are fitted over the ends of the linking member (43). The nuts (44) are threaded onto the threaded ends (47) of the Unking member (43) in a conventional manner and bear down on the washers (46), which in turn bear down on the upper and lower flange plates (37, 39) to maintain everything firmly in place. In a similar fashion, linking member (42) is passed through the upper plate (37), via a bore in the upper plate and corresponding bore (34) in the blade (30, 31) into a corresponding bore of middle flange plate (38), and secured via washer (46) and nuts (44) threaded onto the end of the linking member (42). Once again, although only one such linking member has been shown in the exploded view of Figure 6, it is to be understood that at least two such linking members are present, and preferably four or more such linking members, bearing in mind that the middle flange plate (38) and lower flange plate (39) are also connected together in a similar manner, with corresponding linking members (42) passing through said middle (38) and lower (39) flange plates and through the blades (32, 33) of the lower rotor, which are located at an angular displacement around the axis of rotation compared to the upper rotor. This leads to a very securely assembled structure, capable of withstanding the extreme environments in which it is destined to operate.

Figure 7 is a schematic false perspective view of an alternative embodiment of the Savonius rotor according to the invention as illustrated in Figure 2, with an accompanying pair of flange plates. In this embodiment, as with the embodiment in Figure 2, the outer profile has been modified to produce a smaller volume of blade, hence offering increased performance, wherein the front and rear surfaces are indicated, and it is clear that the front surface has been shaped (17a, 17b) to form a front face that resembles that of a the leading face of an aircraft wing. Dotted lines 16a and 16b illustrate the original edge curve of the front face (12), to indicate more clearly where matter has been removed from the blade. In addition, the flange plates (37, 38) have been shaped accordingly to espouse the edge curves (16a, 16b) of the blades.

Figure 8 is a schematic false perspective representation of a unit containing 4 rotors, or 4 pairs of blades, separated by corresponding flange plates (37, 39, 41), mounted on a transmission axle (45), similar to the assembly illustrated in Figure 5, but made up of the alternative embodiment profiled rotors and flange plates of Figure 2 and Figure 7.

Figures 9a and 9b show a top down view of how parallel, horizontally spaced apart rotor modules can be assembled to form a barrier, or increased surface area to catch air flow, and increase energy conversion, and electrical production of said air or wind flow. In these schematic representations, a first rotor with a pair of blades (30a, 31a) is separated horizontally from a second rotor with a pair of blades (30b, 31b), and in between each rotor or rotor module, a deflector (48) is located. The purpose of the deflector is to increase performance of the rotor assembly by maintaining increased air pressure on the windward side of rotor, and decreased air pressure on the leeward side, thereby increasing air flow speed through the central passage between, and over the blades of each rotor, which in turn allows for more energy to be recovered by said blades and converted into a suitable other energy supply, such as an electrical supply via mechanical transmission.

Figure 10 shows a more detailed representation of the deflector (48) illustrated schematically in Figures 9a and 9b. The deflector (48) is in fixed relationship about a supporting strut (49), and is located in the fluid or air flow path, parallel to the axis of rotation of the rotors between a respective pair of rotor modules, as indicated by the arrows in Figures 9a and 9b. The fluid flow deflector has a substantially "S"-shaped profile, wherein the substantially "S"-shaped profile of the fluid flow deflector is configured, when the blades rotate, to extend the duration of a windward zone of higher fluid pressure, as indicated by the plus signs, in front of face (14) of blade 30b. As can be deduced from Figures 9a and 9b, the windward side of blade 30b moves forward as air flows over its surface. Additionally, the deflector also extends the duration of reduced fluid pressure on the leeward side of of the face (12) of blade (30b). In this way, a drop in pressure in the leeward zone behind the deflector favours increased flow speed through the central airflow passageway and thereby reduces drag on face (15) of the forward moving blade (31b). The deflector can be made of a sheet material, or an assembly of component sections (51), shaped to form a general "S" shaped profile, similar to an airfoil or wing (50) with a thicker dimension at an extremity (53) adjacent the strut (49) than at its periphery (54) where the profile tails off to a point. The deflector (48) is mounted on the strut by any suitable means, for example, a bore (52) provided within the body of said deflector (48) through which the strut passes and is visible at the top and bottom of the deflector. The deflector when mounted in an assembly of rotors, organised in parallel, side-by-side spatial relationship, naturally provides clearance for the blades of the rotors to be able to rotate without touching said deflector. Such clearance is configured to optimize wind or airflow efficiency for the assemblies made up of modified Savonius rotors according to the invention. It should be noted that the deflector (48) is an optional advantageous addition to assemblies constructed with the modified Savonius rotors according to the invention, because it increases overall energy efficiency thereof, but it is not a necessary inclusion for such assemblies to function correctly.

Figure 11 is a schematic representation of a rotor module assembly or rotor module array, comprising a plurality of rotor modules, organised in horizontally parallel, spaced apart relationship, each rotor module being separated from its neighbour by a respective deflector (48a, 48b, 48c, 48d). As can be seen from the illustration, each rotor module in this example contains six Savonius rotors, assembled pairwise in vertical alignment such that:

- each lower pair of blades in given rotor is angularly displaced around the axis of rotation with regard to the corresponding upper pair of blades, in this case by 90°; - each rotor module of six rotors, is aligned horizontally with the next rotor module such that when rows of horizontally aligned blades are considered, the blades of the successor rotor are in angular displacement with respect to the predecessor rotor blades. This gives an overall chequer board effect to the assembly or array, which is considered particularly advantageous.

Figure 12 is a schematic front facing representation of a Savonius rotor module assembly, which has been formed as windbreak (55) and is also configured to generate electricity. The windbreak (55) in this example comprises three vertically mounted, axially aligned, rotor modules, each rotor module consisting of four rotors (30a, 31a) mounted in angular displacement one with regard to the other pairwise. The rotor modules share a common transmission axle (56), which is coaxial with the axis of rotation of the rotors. The windbreak also comprises two further, horizontally spaced apart, and parallel, rotor modules assemblies, each having a respective transmission axle (57, 58) set up in the same way as the first, all of the assemblies being located within a mounting frame or chassis (59) attached to the ground (60). At the top of the chassis (59), a fluid flow deflector (61) is provided, which extends from an upper part of said mounting frame (59) in an oblique plane skywards, and is configured to deflect an oncoming incident fluid flow downwards towards the Savonius rotor modules. Each rotor module is kinetically connected to a neighbouring rotor module via at least one

transmission belt (62, 63) connected respectively between each transmission axle (56, 57, 58), the transmission axles all being held in the vertical position by a crossbar (64) for extra stability. The transmission belts can be toothed belt or chain belts, but best results in terms of torque transmission have been obtained with a toothed belt. The transmission axles are connected to a generator, to allow for production of electricity. A discoid generator has been found to be particularly advantageous in this regard, although other types of generator could also be envisaged. Figure 13 is a side view illustration of a variant of a windbreak (55) and electrical wind turbine system similar to that of Figure 12, where like numerals refer to like elements. The main difference between the electricity producing windbreak of Figure 12 and that of Figure 13, is that the latter also displays a first fluid flow deflector (65), which extends from a lower part of the mounting frame (59) in an oblique plane groundwards, and is configured to deflect an oncoming incident fluid flow upwards from the ground (60) towards the wind turbine rotor modules. Additionally, the windbreak (55) of Figure 13 is also equipped with at least one attachment means (66, 67) for attaching said frame or chassis (59) to the ground (60). In the illustrated example of Figure 13, such attachment means comprise stays (66a, 66b), for example made of steel, or another suitable material, which extend outward and downward from the frame (59) and attached to the ground (60) by any suitable means, e.g. feet (68) and optionally as shown in the Figure, a strut (67), for example a cable or other wire, that is affixed near the top of the frame (59) and which also extends down towards the ground (60), for example, is attached to the feet (68) of one of the stays (66b).

Figure 14 is a false perspective view of a similar configuration to those of Figures 12 and 13, except for the fact that the windbreak and electricity generation installation is much larger. The frame (59) is shown with just a small array or assembly of rotor modules, with the same 3 rotor module vertically aligned assembly, extended horizontally to form a four by three grid or array of rotor modules, each module containing six rotors, i.e. six pairs of blades per module, or a total of seventy-two pairs of blades in just the small area shown in the illustration. The remainder of the frame indicates how many other modules can be fitted to produce a highly efficient windbreak which also will produce electricity when set up as per Figures 12 and 13.

In addition to the various embodiments of the windbreak and wind turbine installation as illustrated in the previous figures, said windbreak structure can also be fitted with at least one lateral fluid flow deflector, mounted on a vertical upright of said mounting frame (59), extending from said upright in an oblique plane outwards and into the wind, and configured to deflect an oncoming incident fluid flow inwards towards the wind turbine modules. Naturally, such a deflector can also be equipped with positioning means, for example, hinges and a locking system, that allow the deflector to be oriented and fixed, into the direction of an oncoming wind or air flow. The various rotors, rotor modules, assemblies, wind turbines, and windbreaks as described above can be used to produce electricity, whereby wind or air flow causes the rotors to rotate about the axis of rotation. As the axis of rotation is co-axial with a transmission shaft or axle, and the flange plates holding said rotors securely are mounted on the transmission axle or transmission shaft, the latter also rotates and imparts rotational energy to a generator, for a example a generator disc located at a convenient location along the length of said transmission axle, preferably near one or both extremities of said axle. Each axle in the structure can transmit its relative rotational energy to another shaft by an interconnecting belt drive as described above, for example a chain belt or a toothed belt drive. The generators can be provided on each transmission axle, or alternatively on a central transmission axle, which coordinates and synchronizes transmission of rotative energy to the generator located on said central transmission axle. The generator generates electricity in a known manner per se, and such electricity can be stored using appropriate electrical energy storage means, such as, for example, a battery, or capacitor, and released when needed, or alternatively directly fed into an electrical feed supply, as required.

The systems as described herein can be positioned not only vertically, as indicated in the figures, but also horizontally. An example of a vertical wind turbine installation according to the invention different to the windbreak application as illustrated is a set of vertically mounted rotors on a transmission axle, said vertical rotor installation being mounted against an upright wall of a building, for example, a house. Alternatively, said rotor installation can be mounted horizontally, for example, across the summit ridge of the house of a roof, whereby the slope of the roof would also assist in funnelling air flow into the wind turbine installation. Naturally, such installations could also be fitted with deflectors to increase the flow of air onto the wind turbine and rotor assemblies, thereby increasing potential power output.

In other, alternative embodiments, for example, the windbreak can be fitted with coloured, or advertising panels or sheets, which are attached to, or printed directly on, the peripheral surfaces of the rotor blades, thereby being used to display a message or advertising when the blades rotate under the impetus of air flow striking the latter. The messages or advertising can be different for each blade, thereby multiplying in a corresponding manner the number of messages, colours or advertising displayed to the viewer of such an installation.