DESCRIPTION

Field of the Art

The present invention refers to a wind generator with vertical axis.

More particularly, the present invention refers to a wind generator with vertical axis which can be effectively used to make generators with limited size (the so-called "micro-wind" generators) .

Prior Art

In recent decades, the search for alternative solutions to the production of energy from fossil fuels has become increasingly intense, fed by concerns related to the diminishing of raw materials as well as to the pollution generated by the use of said fuels.

In particular, attention has been directed towards the production of energy from renewable sources, which would involve a lesser environmental impact.

The main renewable resources taken under consideration are solar energy and wind energy.

With specific regard to wind energy, large-size wind generators with horizontal axis are known, which are theoretically capable of producing a high amount of electrical energy by exploiting the force of the wind.

Unfortunately, the diffusion of wind generators with horizontal axis has slowed due to the fact that the installation and the correct functioning of such generators require particular geographic and atmospheric conditions, in particular in terms of constancy and intensity of the wind, which are not always easy to find.

In order to better exploit wind energy, even in situations where the use of large-size wind generators with horizontal axis would not be possible, wind generators with vertical axis and small size have been developed. The latter are capable of effectively operating, even in the presence of rather weak winds, for example with speed on the order of 5 - 10 m/s.

In particular, the so-called wind generators of "Savonius" type - from the name of the inventor, the Finnish engineer Sigurd J. Savonius - are wind generators with vertical axis comprising a plurality of curved shaped blades mounted along a vertical shaft.

The functioning of the wind generators of "Savonius" type is based on the aerodynamic resistance ("drag") : due to their curvature, the blades of a generator of "Savonius" type offer a lower aerodynamic resistance when they are moved in the direction of the wind than when they are moved in the opposite direction; the aerodynamic resistance differential can be exploited in order to rotate the vertical shaft, which can in turn be connected to known means for the transformation of the mechanical energy into electrical energy .

Even with the advantages deriving from the simplicity of their structure, the wind generators of "Savonius" have a rather limited energy yield, which represents a considerable drawback and an obstacle for their use.

One of the main grounds for the poor yield of the wind generators of "Savonius" type consists of the fact that their functioning is based on the thrust pressure that the wind exerts on the rotor, and that the entire surface of the blades is exposed to the effect of the wind.

As a consequence of the curved form, with respect to the wind origin direction, each blade will have a concave portion or active portion on which the wind thrust pressure will operate in order to rotate the shaft of the generator; but each blade will also have a convex portion or passive portion which will slow said rotation movement, causing a diminution of the energy yield. The main object of the present invention is to overcome the abovementioned drawbacks of the prior art, by providing a wind generator with vertical axis with an improved energy yield .

These and other objects are achieved by means of a wind generator with vertical axis as claimed in the claim set. Description of the Invention

The wind generator according to the invention is a wind generator with vertical axis which includes a rotor that comprises a central rotation shaft with vertical axis and a plurality of curved radial blades, preferably mounted equidistant between a pair of support plates and connected to said central shaft; said blades have a continuous guide surface for the wind from said shaft up to the periphery of said rotor, thus to prevent the wind from radially crossing the rotor.

Advantageously, according to the invention, corresponding first deflectors or internal deflectors are mounted between said support plates, alternating with said blades. Said first deflectors are shaped in a manner so as to form a narrow passage along the path that the wind follows, by following the guide surface offered by the respective blade; due to the presence of such narrow passage, it is possible to obtain an increase in the speed of the wind which acts on the concave portion of the blade, via Venturi effect.

It is observed on such matter that whereas the functioning of the wind generators of "Savonius" type according to the prior art is exclusively based on the aerodynamic resistance ("drag") and hence on the pressure of the wind that hits the blades of the generator, the functioning of the wind generator according to the invention involves the centrifugal force due to the action of the wind flow, acting on the blades of the generator.

Therefore, the invention provides for the presence of the first deflectors and the consequent narrow passage along the path of the wind; on one hand, according to the Venturi effect, such narrow passage leads to a reduction of the pressure, and on the other hand it leads to an increase of the speed.

Since the centrifugal force is proportional to the square of the wind speed, the narrow passage produced by the use of the first deflectors will lead to a considerable increase of the centrifugal force acting on the blades of the generator, also consequently increasing the rotation speed and finally the energy yield of the wind generator.

In a preferred embodiment, the wind generator according to the invention also includes a stator arranged around said rotor and comprising a plurality of second deflectors or external deflectors, suitably shaped for conveying the wind towards the blades of the rotor.

Preferably, said stator also comprises a pair of covers of frustoconical shape arranged at the respective ends of said second deflectors, which further contribute to effectively conveying the wind towards the blades of the rotor.

According to a preferred embodiment, each blade is made in the shape of a flat panel bent on itself around a vertical axis, in a manner such that its cross section assumes the form of an arc of circumference. Preferably, said cross section has the shape of an arc of circumference of about 270° .

Still according to a preferred embodiment, each first interior is made in the shape of a flat panel bent on itself around a vertical axis, in a manner such that its cross section assumes the shape of an arc of circumference; the size and curvature of the first deflectors are preferably selected in a manner such that the minimum distance between an internal deflector and the corresponding blade is equal to 1/6 of the distance between said deflector and said blade at the periphery of the rotor.

Still according to a preferred embodiment, each second deflector is made in the shape of a flat panel bent on itself around a vertical axis, in a manner such that its cross section assumes a shape comprising a first arc of circumference and a second arc of circumference with opposite concavities, connected by an inflection point. Preferably, said cross section comprises a first arc of circumference of about 90° and a second arc of circumference of about 90° with opposite concavities, connected by an inflection point.

The wind generator according to the invention has shown to be particularly effective for making small-size generators, particularly suitable for use by private individuals, e.g. for domestic applications ("micro-wind" generators) . Nevertheless, it is possible to employ the teachings of the invention also for making larger wind generators, up to generators on the order of 50 - 100 kWp (the so-called "mini- wind" generators) .

Summary Description of the Figures

Further characteristics and advantages of the present invention will be clearer from the following detailed description of several preferred embodiments of the same, given as a non-limiting example with reference to the enclosed drawings, in which,

- Figure 1 is a front schematic view of a wind generator with vertical axis according to a first preferred embodiment of the invention;

Figures 2 and 3 are schematic views in section along the line A-A of the wind generator of Figure 1 ;

- Figure 4 is a schematic view in section along a longitudinal plane of a wind generator with vertical axis according to a second preferred embodiment of the invention ;

Figure 5 is a schematic view in section along the line B-B of the wind generator of Figure 4.

Description of Preferred Embodiments of the Invention

With reference to Figures 1 and 2, a first preferred embodiment of a wind generator with vertical axis according to the invention is shown, generically indicated with the reference 1.

Said wind generator 1 includes at least one rotor 3 which comprises a rotation shaft 5 in central position, mounted at the upper and lower ends on bearings (not shown) . Around said rotation shaft 5 and integral therewith, respectively close to its upper end and its lower end, two support plates 7a, 7b are provided for with substantially discoid form. Between such plates, a plurality of radial blades 9a - 9d are mounted, which are extended from the central rotation shaft 5 up to the periphery of the support plates 7a, 7b.

Said radial blades 9a - 9d - four in the preferred embodiment of Figures 1 and 2 - are preferably arranged equidistant around said central rotation shaft and are shaped as flat panels, suitably bent around a vertical axis in order to have a curved cross section, which substantially follows an arc of circumference; in particular, as will be illustrated in detail below, said blades 9a - 9d are shaped in a manner so as to offer a concave surface to the wind which hits the rotor 3 of the wind generator 1, as is visible in Figure 2. Still with particular reference to Figure 2, the blades 9a - 9d are extended from the central rotation shaft 5 up to the periphery of the support plates 7a, 7b and have a continuous guide surface for the wind from said shaft up to the periphery of said plates, defining corresponding separate and non-communicating sectors and preventing the wind from radially crossing the rotor.

As is visible in Figure 1, in order to improve the structural strength of the radial blades 9a - 9d, transverse reinforcement dividers 12 can be provided for. According to the invention, between the support plates 7a, 7b, a plurality of first deflectors or internal deflectors 11a - lid are also provided for, mounted alternating with said blades 9a - 9d.

Said first deflectors 11a - lid are extended from the periphery of the support plates 7a, 7b to an intermediate point between said periphery of said plates and the central rotation shaft 5 and are shaped as flat panels, bent around a vertical axis, in a manner so as to have a curved cross section which substantially follows an arc of circumference. The size, the shape and the position of each first deflector 11a - lid are selected in a manner such to determine a corresponding narrow passage 13 in the space comprised between the radial blades adjacent thereto, along the path that the wind follows, by following the guide surface offered by said blades; due to the presence of such narrow passages 13, it is possible to obtain an increase of the speed of the wind which acts on the blades 9a - 9d, via Venturi effect. Consequently, it is possible to increase the effect of the action of the wind on said blades 9a - 9d, and consequently the rotation speed of the central rotation shaft 5.

As illustrated in Figure 1, the wind generator 1 also preferably includes a stator 14 arranged around the rotor 3. Said stator 14 comprises a framework 15 on which second deflectors or external deflectors 17a - 17d are radially mounted .

Said second deflectors 17a - 17d are preferably provided for in a number equal to the number of blades 9a - 9d of the rotor 3 - four in the embodiment of Figures 1 and 2 - and are preferably arranged equidistant around the rotor 3. Said second deflectors 17a - 17d are in the shape of flat panels, which are subjected to subsequent bending operations in a manner such that their cross section comprises two curved contiguous portions 17', 17''; each of such portions substantially follows an arc of circumference, said portions 17' , 17' ' having opposite concavities and being connected by an inflection point 11'''.

Said second external, static deflectors 17a - 17d, have the function of cooperating with the blades 9a - 9d and with the first, rotatable deflectors 11a - lid, in order to more effectively convey the wind which hits the wind generator 1 towards the path defined by said blades and by said first deflectors .

As illustrated in Figure 1, the stator 14 of the wind generator 1 can also comprise a pedestal 19 which allows placing and maintaining the rotor 3 with the blades 9a - 9d and the first deflectors 11a - lid, as well as the second deflectors 17a - 17d, at a height from the ground that is suitable for optimally exploiting the wind present.

In order to limit the resistance set forth by the rotor 3 against the action of the wind, the rotatable components of the generator 1, and particularly the support places 7a, 7b, the radial blades 9a - 9d and the first deflectors 11a - lid are made of a light material, preferably aluminum or an alloy thereof .

On the other hand, the stationary components of the generator 1, including the second deflectors 17a - 17d, are preferably made of steel or a similar material.

Figure 3 is a reproduction of Figure 2 in which the path of the wind which hits the wind generator 1 according to the invention is schematically reported.

From an examination of Figure 3, the man skilled in the art can immediately infer the functioning the wind generator according to the invention, as well as the advantages connected thereto in terms of energy yield.

The wind flow coming from the direction indicated in Figure 3 by the arrow IN, conveyed by the second deflectors 17a and 17d, hits the rotor 3 of the wind generator. A portion of said flow penetrates into the space defined by the blade 9a and the corresponding deflector 11a. The wind is guided by said blade 9a and by said first deflector 11a through the narrow passage 13 defined thereby, and in such a manner increases its speed. With said increased speed, the wind acts on the concave wall defined by the adjacent blade 9b and induces the rotation of the rotor 3 in the direction indicated by the arrow F. Subsequently, the wind, guided by the surface of said blade 9b, exits from the rotor 3 in the direction indicated by the arrow OUTi .

It is observed that, as illustrated in Figure 3, a portion of the wind flow encounters the concave curved surface of the first deflector 11a, contributing to the rotation of the rotor 3 in the direction of the arrow F.

At the same time, another portion of the wind flow penetrates into the space defined between the blade 9a and the first deflector lib and acts against the concave wall defined by said blade 9a, contributing to the rotation of the rotor 3 in the direction of the arrow F; subsequently, the wind is guided by the surface of the adjacent blade 9d outside the rotor 3, in the direction indicated by the arrow OUT ₂ .

Due to the rotation movement of the blades of the rotor 3, the central rotation shaft 5 will in turn be rotated in the direction F - i.e. in clockwise direction in Figure 3.

The kinetic energy of the rotation shaft 5 will then be transformed into electrical energy by means of suitable means provided for in the wind generator 1 (not illustrated) .

Still with reference to Figure 3, it is clear that the blades 9a - 9d of the rotor 3 of the wind generator 1, as anticipated above, offer a continuous guide surface for the wind flow and prevent the radial crossing of the rotor itself, such that the flow of wind which enters into the space comprised between two contiguous blades 9a and 9b or 9a and 9d will remain confined in said space and will be guided from the surface of said blades up to the output of the rotor .

Passing now to Figures 4 and 5, a second preferred embodiment is illustrated of a wind generator with vertical axis according to the invention.

The structure of the wind generator according to said second embodiment is substantially similar to that of the first embodiment described above and therefore the same numeric references used for said first embodiment will be used here for indicating identical or equivalent components.

Also in the second embodiment, the wind generator 1 includes at least one rotor 3 which comprises a central rotation shaft 5, mounted at the upper and lower ends on bearings 6a, 6b, and a pair of support plates 7a, 7b integral with said rotation shaft 5, of substantially discoid shape, which are respectively provided close to the upper end and the lower end of said rotation shaft; between such plates, a plurality of radial blades 9a - 9d are mounted, which are extended from the central rotation shaft 5 up to the periphery of the support plates 7a, 7b.

Said radial blades 9a - 9d - four in the preferred embodiment of Figures 1 and 2 - are preferably arranged equidistant around said central rotation shaft and are shaped as flat panels, suitably bent around a vertical axis in a manner so as to have a curved cross section, which substantially follows an arc of circumference.

In particular, according to this second embodiment of the invention, said blades 9a - 9d are bent in a manner such that their cross section follows an arc of circumference of about 270°.

Advantageously, in this manner, the blades 9a - 9d offer a concave surface that is optimized for the wind flow that hits the rotor 3 of the wind generator.

Also in this second embodiment, the blades 9a - 9d are extended from the central rotation shaft 5 up to the periphery of the support plates 7a, 7b and have a continuous guide surface for the wind from said shaft up to the periphery of said plates.

Between the support plates 7a, 7b, a plurality of first deflectors or internal deflectors 11a - lid are also provided for, mounted alternating with said blades 9a - 9d.

Said first deflectors 11a - lid are extended from the periphery of the support plates 7a, 7b to an intermediate point between said periphery of said plates and the central rotation shaft 5, and have the shape of flat panels, bent around a vertical axis in a manner so as to have a curved cross section, which substantially follows an arc of circumference .

The size, the shape and the position of the first deflectors 11a - lid are selected in a manner such to determine corresponding narrow passages along the path that the wind follows, by following the guide surface offered by the respective blade; in particular, in order to optimize the Venturi effect, they are advantageously selected in a manner such that the minimum distance d between one internal deflector and the corresponding blade is equal to about 1/6 of the distance D between said deflector and said blade at the periphery of the rotor.

As is clearly visible in Figure 4, the wind generator 1 also preferably includes a stator 14 arranged around the rotor 3. Said stator 14 comprises an upper cover 21a and a lower cover 21b, between which second deflectors or external deflectors 17a - 17d are radially mounted.

Said covers 21a, 21b preferably have frustoconical shape, possibly flared, which narrows in the direction towards the rotor 3 of the wind generator 1, and their smaller base substantially has the same diameter as the respective support plate 7a, 7b of the rotor 3. Such shape advantageously contributes to conveying the wind towards said rotor 3.

The second deflectors 17a - 17d are preferably provided for in a number equal to the number of the blades 9a - 9d of the rotor 3 and are preferably arranged equidistant around the rotor 3. Said second deflectors 17a - 17d are shaped as flat panels, which are subjected to subsequent bending operations in a manner such that their cross section comprises two curved contiguous portions; each of such portions substantially follows an arc of circumference, said portions having opposite concavities and being connected by an inflection point.

In particular, each portion of said second deflectors 17a - 17d preferably follows an arc of circumference with angle equal to about 90°.

In Figure 4, the pedestal 19 of the stator 14 is also illustrated; such pedestal allows placing and maintaining the rotor 3 with the blades 9a - 9d and the first deflectors 11a - lid, as well as the second deflectors 17a - 17d, at a height from the ground suitable for optimally exploiting the wind present.

From that described above, it is clear that the present invention attains the pre-established objects, since it allows obtaining a wind generator with vertical axis with an improved energy yield.

It is also clear that the embodiments described above have been provided for merely exemplifying purposes and that numerous variants and modifications are possible, without departing from the protective scope of the invention, as defined by the set of claims.

For example, even if the wind generator was described with four blades and four first deflectors, a different number thereof could be provided for, e.g. six.

In addition, the number of first deflectors could be different from the number of blades and more than one first deflector could be provided for between each pair of contiguous blades.

Analogously, also the number of second deflectors could be different from the number of the blades and suitably selected on the basis of user requirements.