The present invention relates to an improved Aeolian apparatus. More specifically, the invention relates to an Aeolian silos permitting optimally exploiting power available within the eolic place.

As it is well known, at present, the most diffused system in the eolic generation field is the one comprised of a wind turbine (or blade rotor), rotating about a horizontal axis supported by a pole having suitable diameter and height.

Air flow acting on turbine is that of the specific eolic field wherein the eolic collector is provided.

Energy collected by rotor blades is a direct function of the quadrate of wind speed within the flow of air hitting blades, of air density and of Betz coefficient, which theorically is, for a rotor freely rotating within the eolic field, of β=0,592. In other words, even for very efficient blades it is never passed the value of 0.38 - 0.40 (with a peripheral speed at the end of the blade corresponding to 6-7 times the speed of the wind).

Summarizing, elements important for collection of energy are area of intercepted air and wind speed.

Consequently, tendency is to realize always bigger Wind Energy Collectors (W. E. C) ₁ with higher poles (even 120 m), turbines having a bigger diameter (even 150 m) and thus with always higher costs. Increase of rotor diameter is necessary to obtain an interception area larger than the eolic field current. Height of the pole is necessary to permit realizing a rotor with a bigger diameter, but at the same time this higher height of rotor from the ground involves a higher wind speed, the intensity of which increases with the increasing of the height over ground.

In other words, a bigger area and a higher speed involve a higher rate or volume per second of air passing through the turbine.

In this frame it is included the invention according to the present invention permitting obtaining a bigger air flow rate, and thus, with respect to the known solutions, collecting the same power from the same eolic field with a rotor having a smaller diameter, and a smaller height over the ground, i.e. with the same diameter and height collecting a much higher power. Another advantage of the solution according to the present invention is that of permitting collecting the same power by a lower field speed.

It must be however taken into consideration that, e.g. in Italy, where places with eolic fields characterized by a wind of at least 10 - 12 m/sec, this kind of fields is almost exhausted, while many places with wind speed of 6 - m/sec still are available, with stability wind conditions at least double than those of fields with wind speed of 12 m/sec.

All the above considerations must take into consideration that essential feature required to an Aeolian collector is energy (KWh) collected within a set time period (e.g. one year) and cost of the system.

By the solution suggested according to the present invention it is possible taking a number "n" of air currents from the existing eolic field, said currents having the same physical features of the "original" eolic field, but separated each other, so as not to hinder each other, and thus bringing them to act at the same time on the rotor blades of the eolic energy collector.

These and other results are obtained according to the present invention realizing a rotor, preferably a vertical axis rotor, ducted within a structure collecting the "n" air currents, separated each other so as not to hinder each other, rather obtaining a synergistic effect of physical properties of the transported air volume, and thus of the speed, exploiting at best the natural physical laws.

It is therefore specific object of the present invention an eolic silos characterized in that it comprises, from the bottom toward the upper portion, or vice versa, a base, a body and a turbine, said silos providing n conducts for inlet of air, with n > 2, a first outer conduct, with intake of air laterally from said silos body, and a second conduct inner with respect to said first conduct, with inlet of air from the bottom. Particularly, said silos provide a diffuser downward said turbine.

Preferably, according to the invention, said silos provide 3 conducts.

In the preferred embodiment of the silos according to the invention, it provides a first outer conduct, with intake of air laterally from said silos body, a second conduct and a third conduct, inner with respect to said first conduct, with inlet of air from the bottom, the end of said third conduct ending at a higher level with respect to the end of said second conduct.

Preferably, according to the invention, a diffuser is provided downward said turbine. Particularly, according to the invention, said diffuser can be comprised of a series of conical elements, having an opening angle of about 7°, preferably a succession of five elements.

Still according to the invention, said silos can provide a number of conduct higher than 3, preferably a number multiple of 3. According to the invention, said second and third conducts have the air intake realized in said base.

Always according to the invention, said first conduct provides fins, positively oriented with respect to the dominant winds within the eolic field, within the air inlet. According to the invention, outlet of said conduct is provided at the height of the "vorticous filament" caused by the flow within said first conduct.

Furthermore, according to the invention, fins on the inlet of said first conduct can be oriented. Still according to the invention, a converging element is provided at the outlet of each conduct, increasing the flow speed.

Always according to the invention, a converging element is provided downward said turbine, at the outlet of said conducts.

Furthermore, according to the invention, a movable inlet of air arriving from the eolic field is provided, that can be oriented on the basis of the wind direction.

Silos according to the invention can exploit, as an alternative or in addition to the wind flows, thermal energy taken from accessories supplies. The present invention will be now described, for illustrative but not limitative purposes, according to its preferred embodiments, with particular reference to the figure of the enclosed drawings, wherein: figure 1 schematically shows an embodiment of an Aeolian silos according to the invention; figure 2 is a second schematic view of the silos according to figure

1 ; figure 3 is a plan view of the Aeolian silos according to the invention; figure 4 is a top view of the Aeolian silos according to the invention; figure 5 is a section view taken along line b-b' of figure 3; figure 6 is a view taken according to direction A of figure 3; figure 7 is a section view taken along line c-c' of figure 3; figure 8 is a perspective view of an inner particular of the Aeolian silos according to the invention; and figure 9 is a wind distribution scheme through a standard eolic field. Illustrative and not limitative example described in the following is one of the many possibilities of interpreting the basic idea, and it exploits three different air currents, arriving from a sole outer "Aeolian" field, with the following physical parameters: speed, field V∞=V∞=6 m/sec absolute temperature, T=298°K pressure, P∞=103.100 Pa standard absolute humidity

Aeolian silos shown in the figures is comprised of a body 1 , made up of sheet having a circular section, with a diameter D and a height H, supported by a pair of pillars 2, comprising base 2, which are opposed each other, and suitably designed.

Silos 1 rests on a suitable base 2, the function of which will be described in the following.

A vertical section of half of silos 1 according to the invention is shown in figure 1 (from the half line to the periphery), indicated by letter T, and it shows a cross section where a wall 3 that can be open is shown, with full height fins, and a mirror-like fin system on the opposed wall.

Orientation of silos 1 is such that walls that can be open are frontally provided with respect to the prevailing winds within the eolic field. A "wind rose" is shown in figure 9, showing how it usually is present in a standard eolic field.

In the figures, swinging fins are indicated by letter A that can be open by a suitable program, so as to receive wind from a direction tangential with respect to the perimetral wall of the silos 1. Inlet area of the tangential current within silos, indicated by V1 in figure 1 , causes a rotary circulation, and thus a vorticous motion generating a centrifugal force on molecules of vorticous air which is equal to Fc = a _c x m = vol x p x Vc ₂ /R, wherein Vc = V∞ = eolic field speed, Fc 0 ma, wherein a=v _c ² /R, and corresponding specific pressure on volume unit is Pa = p x V∞ ² /R, wherein R is the ray of trajectory taken into consideration, p is air density, i.e. weight for volume unit, V∞ is air current speed at inlet of the silos, that can also be defined by V∞ = 2τmR, wherein R is the rotation ray of elementary volume taken into consideration, n is the number of revolution that the air elementary volume (e.g. a group of molecules) makes during its vorticous motion. Specific pressure on the surface unit is a quadratic function inverse to the distance, measured in meters, of the surface taken into consideration from the rotation centre.

From the above it is noted that within the Aeolian silos 1 according to the invention a "vorticous filament" having ray R is realised, with a depression that can vary in function of the quadrate of the distance from the vorticous centre. Making a duct 4 within the vorticous centre communicating with the outer eolic field, an air current intake occurs toward the inside of silos 1 , thus a flow rate which is added to the air flow arriving from the outside field. Speed and flow rate of the field will be increased due to the vortex suction. In figure 1 , it is indicated the communication duct 4, which is suitably connected with the outer eolic field through an independent port, on base 2.

Within duct 4, the embodiment shown has a third air duct 5, conveying air from "outer" eolic field port up to the inner part of silos. Duct 5 ends with an outlet port which is higher than the outlet port of duct 4, and it is in the central part of rotor.

Eolic field duct 5 air port is within silos 1 base 2, as the other port 4, but it is separated from the latter so as to be an independent flow rate source. Thus, three different sources are realised, for generalised index "n", having an independent flow rate, and without any negative influence each other. On the contrary, vorticous current increases its depression with inflow 4 (and 5), even remaining practically separated from boundary layer of "vorticous filament". For every dynamic current arriving from outside (particularly from eolic field), a "source current" is induced, creating the above mentioned effect. Separated application for each duct 3, 4 and 5 of Bernoulli law (p + Vi pV ² = cost, wherein p is pressure and V fluid speed in any section which is transversal with respect to the duct), will permit, suitably dimensioning ducts, obtaining, along with the continuity condition applied to the flow, the wished increase between "Eolic field" speed and outflow speed within turbine area, taking into consideration the three flows and thus the resulting isothermal flow, which is possible in view of the low speed and low pressure variations.

As to duct 5, it is evident separation of flow with respect to other flows, being said duct obtained by a tube. As to duct 4, the same applies from the eolic field port to the throat, where its flow exits within the "vorticous filament" caused by current 3, remaining confined within the low pressure zone realised by vortex. In fact, it is the same "vorticous filament" developed by vortex to make boundary layer between flow 4 and flow 3. Flow 3 has a helicoidal motion within silos volume (from the base of the silos to the rotor plane, indicated by reference S).

To have the flow current lines with a prevailingly vertical direction, it can positively be provided in this area a fin assembly, having a vertical extension. Net fins, driving the above volume into vertical channels, permit straightening flow thread, that will act on the leading edge of the wing contour of rotor blades, with the same vertical direction of currents arriving from ducts 4, 5.

Transverse section of silos 1 passes from an outer diameter (in the present embodiment of 34 m) to the lower diameter D ₂ of 26 m, corresponding to the outer diameter of rotor. This is obtained by a converging tapering on which Bernoulli law is applied again, thus obtaining physical parameters valid for calculation of eolic power collected by rotor. It must be noted that, being the rotor ducted, Betz flow losses are not present, as it occurs in free rotors within the eolic field. Thus, formula of the power that can be collected is: p=V ³ _t x At x p x Vz, wherein V _t is current speed at rotor, A _t area covered by rotor, and p is air density.

Other component of the solution according to the invention which is fundamental in order to obtain a remarkable increase of power that can be extracted from the eolic field is the diffuser 6. Air flow, arriving from inside silos 1, crosses area covered by rotor, yielding to blades, according to the aerodynamic theory of wing contours, main part of energy as kinetic energy (1/2mV ² ) and pressure energy, leaving then rotor to go to the atmosphere. Now, residual current speed is under the eolic field value, as well as its pressure, that will be under the atmospheric pressure of an amount indicated in Pascal depending on different factors. Being surrounding atmosphere part of the eolic field, from which energy has been extracted, with higher speed and atmospheric pressure, immediately current will take again, after having left the rotor, values of eolic field, as soon as it will mix with outer atmosphere.

If instead letting air current exiting from rotor, it is put into communication with the eolic field, current is expanded within a diverging discharge tube with suitable length and diameter, an expansion is obtained that, by suitable dimensions of discharge, causes a strong depression, and thus sucking of outer air from base, and thus from eolic field, through the rotor and the three ducts 3, 4, 5, practically increasing air flow through the rotor.

Discharge ration between outlet and inlet (corresponding to the rotor area) areas must be very high to cause a strong sucking effect, and, since maximum inclination of the conical wall of discharge must be equal or under 7°, it is obtained a sucking effect of "only" 1.9 times the regular flow by a tube long 130-150 m (which is obviously not possible).

In order to overcome this problem, two solutions have been suggested, both providing a horizontal rotation axis rotor, but that cannot be used for known pole eolic collectors (WEC), since they are very large and not convenient to be realised.

One of the solutions suggested can be applied to the solution according to the present invention providing a vertical axis rotor, using a particular innovative particular.

A short conical discharge with an inclination of 7° starts from the discharge area. A preferred ratio exists between diameter and length. At the end of the conical tube, a second conical tube with a larger diameter is juxtaposed, having an inclination of 7° starting from diameter where juxtaposition occurs. Substantially, injections of air taken from current close to the rotor, through the slot, is an eolic energy "cushion", resting on the wall of the second tube portion, and, inward, on the air cone flowing toward the exit. This prevents inflow of outside atmosphere, and outlet current of rotor still expands, with a further reduction of pressure with respect to atmosphere. Since new tube portion opens of 7° with respect to the first one, cone will open of 14° with two tube parts. Thus, employing five parts of tube, an opening of 35° is obtained. In the example shown in the figures, with a rotor having an area corresponding to the diameter of 26 m, it would be obtained, with five tube parts, and area having a diameter of 43 m, and a total length of about 5 m.

According to the Boundary Layer theory (Boundary Layer Control), such a diffuser increases flow from 30% to 50%.

The solution according to the invention can be realised with noticeable dimensions, for number "n", even sinergically coupling a plurality of structures exploiting a number "n" = 3 up to the S part, thus realising a new structure as follows. Three silos as described in the above are placed at the vertex of a triangle, realising them up the section S indicated in the enclosed drawing. A structure is put above the three silos, comprised of an envelope connecting them and collecting air flows, that will directed, by suitable direction fins, within the common rotor housing, which is realised within the envelope. It is thus evident that a single rotor will be supplied by nine ducts arriving from the outer eolic field.

Suitably dimensioning each silos, (for example with an outer diameter of 40m), with a rotor having a diameter of 70 m, and an effect to the diffuser of 1.5, a single eolic system of 12 MW is obtained. Height is much reduced: H = about 60 m.

Ground occupancy: 150 m x 150 m, only 50% build up. Eolic field is limited to 6 - 7 m/sec.

Cost of such a system is a fraction of the real cost of silos V ₁ cost presently lower with respect to the traditional pole WEC. Considering cost per KWh of energy produced per year, cost of eolic silos is about 50% of known WEC.

Being known that eolic places with wind speed of about 6 m/sec for about 4000 hours/year have a total cost (not considering the specific costs for build up the structure) much lower than places where wind speed is of about 12 - 13 m/sec (we refer to the costs for location, transportation, preparation of the place, connection with the network, costs for workers and travels, roads, ecc, taking into consideration that places with wind speed of 12 m/sec are on mountains, ecc, or off-shore, with very difficult and expensive conditions) it is well evident that the solution suggested according to the present invention is very interesting.

It has been described in the preceding a solution of inlet area of air current arriving from the outer eolic field, by a number of movable fins opening at the periphery of silos. Making reference to the local wind distribution (see for example figure 9), and considering that dominant and persistent winds arrive from a range of directions of about 70°-75°, fins must be provided tangentially with respect to the current at the silos periphery, maintaining the same inlet direction.

In other words, circle arc of periphery occupied by fins is double with respect to the above mentioned angle, considering dominant winds arriving from the two main directions. Thus, each range will occupy an arc of about 150°. Each vertical fin will have a pin, two or more supports and a motion system.

From figures it is observed that preferably inlet of air within silos is not direct but in a structure outside the perimeter, provided with fixed fins, suitably oriented, faced toward the wind of the two opposed ranges. Thus, two (opposed) tangential walls are obtained on the tower perimeter, each one with an arc which is the half of the one described in the above. Thus, also number of movable fins is the half, with the consequent advantages of constructions savings.

The present invention has been described for illustrative but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be introduced by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.