The invention relates to a sound damping arrangement for a vertical axis wind turbine, as well as to a sound damping device, a vertical axis wind turbine assembly, and a building. BACKGROUND

Vertical axis wind turbines are known in diverse variants, for instance for use in built-up surroundings, as on a building. Such wind turbines can contribute in a relatively compact way to an environmentally friendly energy supply, for instance for the building itself. In built-up surroundings, it is of particular importance that in use of wind turbines nuisance and inconvenience for people inside and outside buildings be avoided. Wind turbines, however, are generally known for the noise nuisance they can cause. Further forms of possible nuisance or inconvenience concern for instance shadow movement and flashes of light associated with rotor movement, and disfigurement of the building and the built-up surroundings.

Proposals are known for reducing such nuisance and inconvenience. WO2012/076839A2, for instance, discloses a turbine arrangement with an independent fixed structure which surrounds a freestanding turbine, with sound absorbing panels provided to reduce the noise output of the turbine.

While sound absorbing panels in themselves can contribute to some reduction of noise nuisance, there is a need for further improvement in this field. For when nuisance and inconvenience can be progressively counteracted further, the advantages of wind turbines can be utilized in built-up surroundings on a progressively more extensive scale. SUMMARY

An object of the current invention is to counteract nuisance and inconvenience caused by vertical axis wind turbines in built-up surroundings. An object is to reduce noise output from a vertical axis wind turbine. An object is to enable more extensive application of wind turbines in built-up surroundings. An object is to remedy at least partly at least one of the above-mentioned disadvantages or an associated disadvantage.

According to a first aspect, to that end, a sound damping arrangement for a vertical axis wind turbine is provided. The sound damping arrangement comprises a plurality of first stator elements disposed at a distance from each other, together defining between them a rotor space for a rotor of the vertical axis wind turbine. In at least one, preferably each, of the first stator elements a sound damping chamber is formed having at least one opening which faces the rotor space and through which air pressure waves can enter the sound damping chamber from the rotor space. In the rotor space a vertical axis wind turbine may be included, or a horizontal axis wind turbine.

Sound that is produced by the vertical axis wind turbine can thus in the form of air pressure waves reach the sound damping chamber from the rotor space via the at least one opening, thereby allowing the sound to be damped particularly effectively.

The first stator elements may for instance be vertically oriented and extend in a height. Thus the first stator elements can define corners of the rotor space. The at least one opening of the first stator elements may then be substantially vertically oriented and/or extend practically throughout the height of the first stator element. The at least one opening is advantageously of substantially elongate configuration, preferably practically throughout the height of the first stator element. Thus, sound can be captured practically throughout the height of the rotor space. The sound damping chamber and/or the opening may then be operative as a so-called Helmholtz resonator, which can particularly strongly damp sound at or in one or more defined frequencies or frequency bands. Thus, the chamber and/or the opening can be dimensioned as desired so as to provide for a particularly strong sound damping at or in one or more frequencies or frequency bands which are particularly associated with possible nuisance or inconvenience. This may then involve, for instance, relatively low sound frequencies, which can generally carry relatively far and so, in case of insufficient damping, could cause nuisance in a fairly wide range of the surroundings. Relatively low sound frequencies involve, for instance, frequencies of up to about 500 Hz. Thus, a Helmholtz resonator as referred to above is preferably configured to damp frequencies up to about 500 Hz more strongly than frequencies higher than 500 Hz, and/or to have a maximum absorption at a frequency lower than 500 Hz. To this end, the sound damping chamber and or the opening is preferably dimensioned accordingly to be of relatively large size. The Helmholtz resonators are configured with a relatively large chamber, in order to absorb sound in a widest possible frequency range up to about 500 Hz. This in contrast to known resonators which usually have a narrow chamber directed to only a limited or narrow frequency range, typically around a frequency. Damping in a wide frequency range up to about 500 Hz is desirable since depending on the wind speed a frequency of the sound generated by the wind turbine can vary. The Helmholtz resonator might be regarded as a mass-spring system. The volume of the opening of the chamber can then be regarded as the mass, and the volume of the chamber can be regarded as the spring. By, for instance, providing a relatively wide opening, a relatively wide frequency range can be damped. Also, for instance, the volume of the chamber may be about twice to ten times greater than the volume of the opening.

Sound damping panels, such as are proposed in the prior art, by contrast, are known to damp mainly higher sound frequencies, which generally carry less far anyhow and so will often be less relevant for ambient nuisance. Nonetheless, for that matter, as an addition, sound damping panels, or more generally sound damping material, can be used in a sound damping arrangement according to the current invention, especially for damping high-frequency tones, or in the lower frequency tones, after all, albeit in a much narrower range. Thus, for instance, an inner side of the sound damping chamber may be lined with sound damping material. Such a combination of damping by Helmholtz resonance on the one hand and damping by absorbing material on the other hand can advantageously provide for effective sound damping across a particularly wide frequency spectrum.

To what specific frequency/frequencies or frequency band(s) damping is to be substantially directed in the design of the sound damping arrangement, depends on the specific properties of the vertical axis wind turbine and the surroundings in which it is to be placed. In particular, it is expected that with the sound damping arrangement according to the invention especially low-frequency and deep-frequency tones can be damped over a relatively wide frequency range of up to about 500 Hz.

Optionally, the first stator elements are mutually substantially rotation-symmetrically disposed relative to a central axis of the rotor space. The central axis corresponds during use, for instance, to an axis of a substantially vertical rotor shaft of the vertical axis wind turbine. Optionally, the first stator elements are disposed with regular interspaces around the rotor space. Due to such a substantially rotation-symmetrical arrangement, the operation of the sound damping arrangement and/or a wind turbine associated therewith can be substantially insensitive to wind direction.

Optionally, the number of first stator elements of the plurality of first stator elements is in the range of three through eight, preferably in the range of three through six. More preferably, the number of first stator elements is four. Thus, the first stator elements can define angles of a polygonal rotor space.

With such a number of first stator elements, a relatively simple but yet effective sound damping arrangement can be realized, which, moreover, can be used relatively easily at various locations.

Optionally, the first stator elements, on a respective side thereof facing the rotor space, are widened with respect to an opposite side facing away from the rotor space.

Thus, an effective opening can be formed which faces the rotor space, while wind coming in from outside is relatively little hindered by the first stator element.

Optionally, on the side facing away from the rotor space a pointed end is formed which, with respect to the rotor space, points outwards.

Incoming wind can thus be guided around the first stator element with relatively little energy loss.

Optionally, the first stator element is substantially formed as a fin and/or wing element, which as such extends substantially vertically, that is, substantially parallel to the central axis of the rotor space. Optionally, the at least one opening extends substantially in the same vertical or parallel direction, for instance as an elongate slot.

Optionally, on the side facing the rotor space, a wall section of the first stator element is formed, the wall section having an outer surface that faces a central part of the rotor space.

Optionally, the at least one opening is formed in, at least coplanar with, the wall section of the first stator element.

Such a wall section with opening can effectively contribute to the Helmholtz resonance mentioned, whereby air volumes on both sides of the wall section, hence on the side of the rotor space and on the side of the sound damping chamber, are in mutual communication via the opening. Optionally, between adjacent first stator elements of the plurality of first stator elements a passage is formed through which wind can blow into and/or out of the rotor space.

Thus, the vertical axis wind turbine concerned can be properly accessible to wind flows, so that the turbine can effectively convert wind energy from such flows.

Optionally, the passage becomes gradually narrower in the direction of the rotor space, in particular because of a shape and/or arrangement of the adjacent first stator elements. With such a shape, for instance a funnel shape, of the passage, wind can be accelerated in the direction of the rotor space, which can promote the efficiency of the respective wind turbine. Moreover, such a shape of the passage can be well combined with a herein described advantageous shape of the first stator element. Advantageously, the first stator elements may be configured as profile elements which guide the air flow towards the wind turbine disposed in the rotor space. Such profile elements may for instance be configured as a wing-shaped profile or a drop -shaped profile, with the at least one opening of the first stator element facing the rotor space. Optionally, the passage is substantially bridged by a plurality of second stator elements disposed with mutual interspaces. The second stator elements are preferably configured in the form of slats. The second stator elements can in particular bridge the passage on a side of the passage facing away from the rotor space. The second stator elements may for instance be of horizontally oriented design.

With such second stator elements, various advantages can be realized. Thus, they can provide additional sound damping, for instance by their mutual intervals and/or by sound damping material arranged thereon. Further, they can counteract the rotor of the turbine being able to cause in its surroundings a moving shadow, they can help the turbine being concealed from view or camouflaged, and they can help protect the turbine, in particular the rotor, for instance from precipitation, birds, or wind-borne material. For that matter, for alternative or additional protection or security, for instance from bats, smaller birds, or human hands, the rotor space may be provided with a fencing, for instance arranged on a side of the passage facing the rotor space.

According to a further aspect, a sound damping device for a vertical axis wind turbine is provided. The sound damping device comprises the sound damping arrangement described herein. The first stator elements are then preferably fixed in their mutual arrangement, for instance by one or more frame elements, the optional second stator elements, a roof element and/or a bottom element.

With the sound damping device, the above-mentioned advantages can be provided, while the sound damping arrangement is particularly easy to place, for instance upon placement of the vertical axis wind turbine.

Optionally, the sound damping device is configured as a housing for the vertical axis wind turbine. Thus, the sound damping device can for instance form an encasing for the vertical axis wind turbine.

Thus, the sound damping arrangement can be combined with a vertical axis wind turbine in a particularly compact and protective manner.

Optionally, the sound damping device comprises a generator housing part for housing a generator of the vertical axis wind turbine. The rotor space may then be formed in particular above and/or under the generator housing part. Thus, the generator can be properly protected in a housing, which at the same time can contribute to favorable wind guidance and/or sound damping. A distance between generator and rotor can thus be relatively short, so that the whole is compact and thus, for instance, projects relatively little from a roof and/or facade of a building. Optionally, the sound damping device is provided with a ballast for stabilizing the sound damping device and/or a vertical axis wind turbine associated therewith.

Such a ballast, for instance in the form of a concrete roof slab and/or bottom slab, can contribute to the damping of vibrations in the sound damping device itself, and can make a fixed connection between the sound damping device and a supporting surface therefor, such as a roof of a building, superfluous. In this connection, it is noted that stronger damping of vibrations, for instance by correspondingly weighting the ballast, can be desirable in correlation with a higher moment of inertia of the rotor. The moment of inertia can depend, for instance, on a mass and/or mass density of the rotor, in particular on an outer side thereof.

Optionally, the sound damping device and/or a vertical axis wind turbine associated therewith is provided with a damping means to counteract transfer of vibrations via contact surfaces to the surroundings, for instance a building. Such a damping means is for instance provided between a roof of a building and an underside of the sound damping device, and preferably comprises a damping material and/or a damper.

Optionally, the sound damping device is of modular design, such that sound damping devices can be mutually hnked, for instance stacked.

A modular device may for instance be formed by mutually cooperating coupling parts which are provided on both sides of the sound damping device, for instance at a top and a bottom, and/or elsewhere. It will be clear that for such a modular device and linking thereof, it is generally desirable that sound damping devices can join each other in a substantially fitting manner, in particular in a regular grid arrangement, for instance by way of a corresponding polygonal shape such as a rectangular shape or hexagonal shape.

When sound damping devices have thus been linked together, a tunnel effect can be realized with relatively even wind streams, thereby allowing the total efficiency of the turbines to be further augmented. To this end, additionally, if desired, also elsewhere on the building, further wind guiding elements may be provided, for instance comprising slats. Moreover, by means of and/or in conjunction with such elements, if desired, additional sound damping may be provided, for instance utilizing resonators and/or sound damping material there. If desired, along with such devices or links of devices, for instance on a roof, also additional sound damping devices may be provided, which, however, are then of stand-alone configuration, merely as sound damping chamber, for instance at the corners of such a linked arrangement of sound damping devices.

Optionally, the sound damping device is provided with a local sealing, in particular a roof sealing. With it, the wind turbine and or the sound damping device can be additionally protected, in particular from precipitation and/or other environmental influences. Optionally, the sound damping device is provided with a solar energy device, for instance a photovoltaic panel and or a solar collector, for instance at a top of the sound damping device and/or on one or more of the optional second stator elements. Thus, at the location of the conversion of wind energy with the vertical axis wind turbine, also solar energy can be converted.

According to a further aspect, a vertical axis wind turbine assembly is provided. The vertical axis wind turbine assembly comprises a vertical axis wind turbine which is provided with the sound damping arrangement herein described, for instance in the sound damping device herein described. With the vertical axis wind turbine assembly, above-mentioned advantages can be achieved. The vertical axis wind turbine itself may be realized in various manners, including manners known per se. A vertical axis wind turbine normally has a rotor with one or more rotor blades which can be driven by wind around a substantially vertical rotation axis, to which a generator is coupled which can convert the rotor movement into a usable form of energy, in particular electric power. The current invention is not limited to any specific type of vertical axis wind turbine, and is thus particularly widely applicable. It is noted that thus, for instance at coastal locations, other types of vertical axis wind turbines can be used than at more inland locations, which may be desirable in connection with differences in wind conditions between such locations.

According to a further aspect, a building is made available which is provided with at least one vertical axis wind turbine assembly herein described.

The at least one vertical axis wind turbine assembly is for instance provided on or to a roof of the building, but may for instance also be provided to a facade of the building and/or elsewhere.

A generator of the vertical axis wind turbine may be electrically connected with an electric installation of the building. Thus, electric energy generated by the turbine may be consumed in the building and/or be supplied via the building to an associated electricity grid. Advantageously, a building can thus be made available that is self-supporting in its own energy supply.

Optionally, the vertical axis wind turbine assembly includes a measuring device and/or a control device, with for instance a wired or wireless connection to a central measuring and/or control system, which is for instance usable from the building.

The number of and/or the dimensioning of sound damping arrangements, sound damping devices and/or vertical axis wind turbine assemblies can be chosen depending on the space available on or at the building, as well as other possible preconditions such as maximum roof load, requirements connected with permits, etc. Thus, for instance other and/or additional sound damping devices may be used at corners of a building, in particular to provide stronger damping there. At the location of a stairway core or lift core of the building, for instance a higher roof load may be possible, so that this can be a preferred location for placement of one or more vertical axis wind turbine assemblies.

When the dimensioning mentioned is performed on the basis of relevant standards, for instance ISO standard 668, in that way efficient production, transport and installation can be promoted. Thus, an outside dimension, in particular a width, of a sound damping device may for instance be tuned to an inside dimension, for instance a width or length, of a standard freight container. With that, a predetermined number of sound damping devices or vertical axis wind turbine assemblies can then be efficiently transported in a standard freight container, for instance a single series of five devices or assemblies side by side in a standard 40 -foot freight container. In the case of particularly compact vertical axis wind turbines, for instance with a generator at the height of the rotor, vertical axis wind turbine assemblies could, if desired, be stacked in a standard freight container, so that for instance ten (5 x 2) assemblies fit into a standard 40-foot freight container. Alternatively or additionally, the dimensioning can be performed on the basis of dimensions of vertical axis wind turbines already available on the market. A vertical axis wind turbine assembly is preferably placed close to a building, in particular substantially directly on, in or to a roof or a facade of the building. This in contrast to traditional wind turbines which are placed on a tower or pole or the like. If desired, sound damping devices and/or vertical axis wind turbine assemblies can be linked, for instance laterally linked and/or stacked, which allows a modular arrangement to be realized, as discussed elsewhere herein. In that case, between a vertical axis wind turbine assembly and the building, nonetheless an intermediate vertical axis wind turbine assembly may be provided.

The sound damping device is preferably to a great extent stably placed, in particular such that the sound damping device is substantially unable to move under the influence of wind. Thus, the stator elements can, after placement, remain stably positioned, substantially independently of wind direction or wind force.

Nonetheless, elements such as stator elements may be configured to be adjustable as desired, whereby a fixation of their position may be temporarily reduced to allow manual or other adjustment.

Thus, for instance, the at least one opening might be configured to be adjustable, to thereby allow damping properties such as damping frequencies of the sound damping device to be adapted as desired. While the invention is explained on the basis of vertical axis wind turbines, it may equally well be applied to horizontal axis wind turbines. Horizontal axis wind turbines for on, for instance, a roof of a building in an urban environment are well known. The first stator elements of the sound damping device can then for instance be vertically or horizontally oriented. In the case of a vertical axis wind turbine, the first stator elements can be substantially vertically oriented.

BRIEF DESCRIPTION OF THE FIGURES

Hereinafter, the invention will be further explained with reference to drawings, on the basis of examples of embodiments. The drawings are schematic and show only examples. In the drawings, corresponding elements are indicated with corresponding reference signs. In the drawings:

Fig. 1 shows a cutaway top plan view of an example of a vertical axis wind turbine assembly; Fig. 1A shows a top plan view corresponding to Fig. 1, in which, additionally, perforations in a perforated plate are shown;

Fig. 2 shows a cutaway and partly transparent side view of the vertical axis wind turbine assembly of Fig. 1;

Fig. 3 shows a side view of a further example of a vertical axis wind turbine assembly; Fig. 4 shows an isometric view of an example of a building with vertical axis wind turbine assemblies; and

Fig. 5 shows a side view in cross section of an upper portion of an example of a building.

DETAILED DESCRIPTION

The drawings show an example of a sound damping arrangement 1 for a vertical axis wind turbine 2, comprising a plurality of first stator elements 3 disposed at a distance from each other, together defining between them a rotor space 4 for a rotor 5 of the vertical axis wind turbine 2.

As can be seen best in Fig. 1, in at least one, here each, of the first stator elements 3 a sound damping chamber 6 is formed with at least one opening 7 which faces the rotor space 4 and through which air pressure waves, from the rotor space 4, can enter the sound damping chamber 6. The chambers 6 with openings 7 are here each operative as a

Helmholtz resonator, so that in particular low-frequency sound can be properly damped. Within the chambers 6 and, for that matter, optionally elsewhere in and/or on the arrangement 1, sound damping material 20 may be provided, in particular for damping of more high-frequency sound. Sound damping material 20 may for instance be wool such as glass wool or rock wool, or foam, or material which is known per se for use in sound damping panels. The sound damping material 20 may be used in the form of panels, but this is not requisite.

The openings 7 in this example are formed as an elongate slot which extends substantially parallel to a central axis C of the rotor space, that is, substantially vertically. Alternatively, for instance, in each chamber a series of openings may be provided, which have mutually, for instance, different vertical positions. In this example, the sound damping arrangement 1 is comprised in a sound damping device 13 for the vertical axis wind turbine 2. The first stator elements 3 are here fixed in their mutual arrangement.

Together with the vertical axis wind turbine 2, the sound damping device 13, at least the sound damping arrangement 1, here forms a vertical axis wind turbine assembly 17.

In Figs. 4 and 5, examples can be seen of how a building 18 may be provided with one or more vertical axis wind turbine assemblies 17 in various ways. Thus, vertical axis wind turbine assemblies 17 may be placed on or to a roof 19 of the building 18, and/or to a facade 24 of the building 18. Vertical axis wind turbine assemblies 17 may then be linked, for instance laterally and/or in a stack. To that end, the sound damping device 13 is preferably of modular design, for instance with standardized dimensioning and/or with coupling parts which may be provided on one or more outer sides of the device 13, for instance in conjunction with one or more frame elements 22. In Fig. 4, by way of example, with a dashed line a vertical axis wind turbine assembly 17 is indicated which can thus in a modular way be linked as desired with adjacent assembhes 17 which are drawn there with full lines. A vertical axis wind turbine assembly 17 can slightly project relative to the roof 19 or the facade 24, but this is not requisite. Thus,

Fig. 4 shows, inter alia, an example of a vertical axis wind turbine assembly, denoted with 17*, of which one or more outer surfaces are substantially aligned with an outer surface of the roof 19 and/or the facade 24.

When a building 18 is thus provided with one or more vertical axis wind turbine assemblies 17, a generator 15 of the respective vertical axis wind turbine 2 can be connected with an electric installation of the building 18. Alternatively, the generator 15 may for instance be connected more directly with an electricity grid. In Fig. 5 it can be seen that the building 18 may be provided with one or more further wind guiding elements 26, for instance comprising slats and/or a supplemental roof slab, with which the total efficiency of the turbines can be augmented in that a tunnel effect through the linked assemblies 17 is promoted.

Reverting to Fig. 1, it can be seen there that in this example the first stator elements 3 are mutually substantially rotation-symmetrically disposed relative to a central axis C of the rotor space 4, in particular with regular interspaces all around the rotor space 4. The number of first stator elements 3 of the plurality of first stator elements 3 is four here, although other numbers are possible.

The first stator elements 3 are here, on a respective side thereof facing the rotor space 4, widened relative to an opposite side facing away from the rotor space 4, on which here a pointed end 8 has been formed which points outwards relative to the rotor space 4.

On the side facing the rotor space 4 there is a wall section 9 of the first stator element 3, the wall section 9 having an outer surface 10 which faces a central part of the rotor space 4.

The at least one opening 7 is here formed in the wall section 9. In the example shown, the opening 7 is formed off-center in the wall section 9, in particular near a more obtuse one of two angles of the first stator element 3, but this is not requisite.

The first stator elements 3 in this example are substantially irregularly shaped, in particular having a shape which is substantially asymmetrical relative to a plane in which the central axis C extends. Such an irregular shape can advantageously contribute to effective sound damping, for instance in that unfavorable sound reflections can be counteracted. Between adjacent first stator elements 3 of the plurality of first stator elements 3, here in each case a passage 11 has been formed through which wind can blow into and/or out of the rotor space 4.

In this example, the passage 11 becomes gradually narrower in the direction of the rotor space 4, in particular due to a shape and/or arrangement of the adjacent first stator elements 3. In the side view of Fig. 2 it can be seen that the passage 11 thus has a funnel-like shape which, besides being defined by the first stator elements 3, is defined by an inclined outer surface of a generator housing part 14. For that matter, it is noted for clarification that because of the symmetry, visible in Fig. 1, of the vertical axis wind turbine assembly 17, the side view for each of the four sides is here substantially as represented in Fig. 2. The rotor 5 in the view of Fig. 2 is partly behind the first stator elements 3 represented there, which are in effect represented in part as transparent.

In Figs. 1 and 2 it can be seen that here a fencing 21 has been arranged on the side of the passages 11 proximal to the rotor space 4. While each fencing 21 here extends substantially in a straight plane, such a fencing may for instance also be formed with a curvature following an outer circumference of the rotor 5, so that the rotor space 4 can be particularly compact relative to the rotor 5.

The passage 11 can be substantially bridged by a plurality of second stator elements 12 disposed with mutual interspaces, preferably in the form of slats, in particular on a side of the passage 11 remote from the rotor space 4. The second stator elements 12 are not shown in Fig. 2, to allow the structures behind them to be shown. The side view of Fig. 3 does show the second stator elements 12. In this example, the second stator elements 12, here implemented as slats, are clad with a sound damping material 20. Due to the interspaces between the second stator elements 12, the passage 11 remains properly passable for wind. In Figs. 2 and 3 it can also be seen that the sound damping device 13 is configured as a housing, for instance an encasing, for the vertical axis wind turbine 2. The sound damping device 13 can thus surround the vertical axis wind turbine 2 in a protective manner and conceal it substantially from view.

In Figs. 1 and 2, with numeral 14 a generator housing part 14 is indicated for housing of a generator 15 of the vertical axis wind turbine 2. In this example the generator housing part 14 extends under the rotor space 4 and further outwards under earlier-mentioned inclined outer surfaces bounding the passages 11 at a bottom thereof. Thus, the generator 15 may for instance be provided at a short distance straight under the rotor 5, while the generator 15 is properly screened from weather influences. In the generator housing part 14, if desired, sound damping material may be arranged so as to damp noise that during use is produced by the generator 15 itself. In the generator housing part 14, for instance in one or more of the inclined bottom surfaces of the passages 11, an access hatch or the like may be provided for maintenance on the generator 15.

In Fig. 2 it can further be seen that, as an option, at a bottom of the rotor space 4 and/or between the rotor space 4 and the generator housing part 14 one or more perforated plates 25 may be provided, which can provide for further additional sound damping. The dimensions of the perforations in the plates 25 may be chosen such that via the earlier cited principle of Helmholtz resonance at the location of the plates 25 sound damping occurs at one or more predetermined sound frequencies. Thus the perforations may also differ mutually in their dimension and/or shape, so that the plate 25 can for instance damp a band of sound frequencies. The plate 25 may thus for instance damp medium sound frequencies, supplementarily to the damping of mainly low frequencies by the openings 7 and the damping of mainly high frequencies by the sound damping material 20. Thus, particularly good sound damping can be achieved across a wide spectrum of sound frequencies. The plate may thus be designed with so-called tiny Helmholtz resonators, as square or circular perforations, and may be provided between the motor and the windmill, or at the top of the windmill. Possibly, in the first stator elements, also such perforated plates may be supplementarily provided.

In Fig. 1, for clarity of the drawing, no perforations are drawn in the plate 25 indicated there. For a schematic example of such perforations in the plate 25, reference is made to Fig. 1A which, for that matter, otherwise corresponds to Fig. 1. Such perforations are thus preferably provided in a manner spread along an entire bottom surface of the rotor space 4. In Fig. 1A it can also be seen that the plate 25 can optionally be built up from several, here substantially triangular or trapezoidal, plate sections, which are for instance disposed around the central axis C next to each other to form a perforated plate 25 together. The density of the perforations in the plate 25 may or may not be equal in different areas of the rotor space 4 and/or the plate 25.

For further supplementation of the sound damping, adjacent to, for instance between, the one or more plates 25, sound damping material 20 such as wool may be arranged, as shown in Fig. 2. In Fig. 2, as an example, at the top and bottom of the sound damping device 13 concrete slabs 16 can be seen which serve as ballast 16 for stabilizing the sound damping device 13 and/or the vertical axis wind turbine 2. It will be clear that at least the upper concrete plate 16 is not shown in the cutaway top plan view of Fig. 1, so that the structures located under it are visible. A bottom of the upper concrete plate 16 may for instance be clad with sound damping material.

An optional sealing 23, shown in Fig. 2 by way of example along a top of concrete plate 16, can further contribute to a proper protection of the vertical axis wind turbine 2 and the sound damping device 13. Thus, improved means are provided to counteract nuisance and inconvenience caused by vertical axis wind turbines in built-up surroundings, in particular to reduce noise output from a vertical axis wind turbine. Thus, more extensive application of wind turbines in built-up surroundings is made possible.

While the invention has been explained herein on the basis of examples of embodiments, these examples do not constitute any limitation of the invention, which is defined in the claims. Many variations, combinations and extensions are possible, as will be clear to the skilled person. Thus, a sound damping arrangement can have a substantially rectangular outer shape, or other shape, such as a shape of a pentagon, hexagon, etc. Further examples are indicated at various places in the description.

For the purpose of clarity and a concise description, features are herein described as part of the same or separate embodiments, however, it will be clear that the scope of the invention can encompass embodiments with combinations of all or some of the features described. It will be understood that the embodiments shown have the same or like components, except where they are described as being different. The mere fact that certain features are mentioned in mutually different claims does not mean that a combination of these features cannot be used to advantage. Many variants will be clear to the skilled person. All variants are understood to be comprised within the scope of the invention which is defined in the following claims. LIST OF REFERENCE SIGNS

1. Sound damping arrangement

2. Vertical axis wind turbine

3. First stator element

4. Rotor space

5. Rotor

6. Sound damping chamber

7. Opening

8. Pointed end

9. Wall section

10. Outer surface of wall section

11. Passage

12. Second stator element

13. Sound damping device

14. Generator housing part

15. Generator

16. Ballast

17. Vertical axis wind turbine assembly

18. Building

19. Roof of building

20. Sound damping material

21. Fencing

22. Frame element

23. Sealing

24. Facade of building

25. Perforated plate

26. Wind guiding element of building

C. Central axis