GB2491853A

GB2491853A - Modular wind turbine system with repositionable turbines

Info

Publication number: GB2491853A
Application number: GB1109956.1A
Authority: GB
Inventors: Giles Henry Rodway
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-06-13
Filing date: 2011-06-13
Publication date: 2012-12-19
Anticipated expiration: 2031-06-13
Also published as: GB2491853B; GB201109956D0

Abstract

A modular wind turbine system comprises at least one elongate structural members 1 supporting wind turbines, wherein the wind turbines may readily be attached to 13, removed from, and repositioned 14 along said elongate structural members in order to optimise the numbers and spacings of wind turbines in an array, according to requirements at the site where the turbines are installed. The turbines may be axial or transverse flow machines and may have a variety of rotor forms with attached individual generators. The attachment may be via a friction clamping to provide infinite adjustment or via a positive attachment e.g. a pin or bolt to provide discrete attachment points. The elongate members may be arranged to from wind fences which may be linear, curved or branching.

Description

Modular Wind Turbine System

FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a modular wind turbine system suitable for the construction of wind farms.

The desirability of converting wind energy into electrical energy is well known, namely that the electricity is generated without the burning of fossil fuels, and thus without the associated carbon dioxide emissions.

Conventional wind farms, which consist of large scale horizontal axis turbine installations, suffer from a number of significant financial and environmental drawbacks: Each turbine requires its own very tall and heavy steel tower, with massive tower foundations. New access roads capable of carrying heavy lifting equipment, and additional land drainage are also often required when a conventional wind farm is installed.

Apart from the financial, energy and environmental costs of this additional infrastructure, the turbines themselves are often objected to by local communities due to their visual dominance of the landscape and production of visual fflickeC and low frequency noise, which can be perceived as a nuisance even at considerable distances from the installation, due to the height of the turbines above ground level.

Environmental objections and physical access for turbine equipment and cranes constitute severn constraints on the range of locations where large onshore wind turbines may be deployed. Offshore wind turbines overcome the visual and noise objections, but suffer even larger installation and cabling/connection costs.

As an alternative to individual large turbines a number of systems have been proposed to mount arrays of smaller turbines on tall towers or large scaffolding-type frames on rotating platforms, in various patents and patent applications, for example U56749399 and W02009130691. These designs, however, would suffer from many or all of the objections described above, including noise, and visual obtrusiveness. Additionally, rotating platform devices could require a relatively large footprint on the land they occupy.

A different approach has been to mount smaller turbines on buildings either singly or in arrays as, for example, described in US4220870 and WO2005052362. However, a number of studies have shown that the wind speed is so reduced, and turbulence so increased in the vicinity of most buildings, that the energy output of such arrays is likely to be minimal in most cases, Smaller wind turbines on individual poles placed away from nearby buildings, tall trees or other obstacles produce a much better power output than equivalent building mounted ones. A variety of such machines is now commercially available, including both horizontal axis types, which need to have their rotation axis aligned with the wind direction for optimum efficiency and also vertical axis' machines which are sometimes described as omnidirectional in that they are able to extract energy with moderate efficiency from wind arriving from any direction in a plane perpendicular to the axis of the turbine. Thus for certain wind directions a vertical axis' machine will extract energy even if its axis is other than vertical. Conventional installations of individual horizontal or vertical axis machines still require the considerable additional energy, installation and financial costs of the individual supporting poles or towers, which must be of sufficiently strong construction to withstand gale force winds from any direction Some proposals have been made for linear "wind fence" type constructions either at ground level or raised on poles as, for example, described in U$5642984, US4265086, US221 8887, and USI 876595.

Such systems have, however, comprised turbines at fixed spacings relative to one another within the framework, with no simple means proposed to after the turbine spacings in the assembled structures, and with no simple or rapid means to remove or replace individual turbines in case of damage, required maintenance, or upgrades.

In practice, both before and after installation of a system in which wind turbines are mounted in frames, it may prove desirable to alter the spacing between individual turbines (for example once operating experience indicates which parts of the site experience the strongest winds, or where, for other reasons, there are local variations, within a site, in the prevailing wind direction due to local topography of the site or changes in the degree of shielding of parts of the site by trees or buildings, or where it is not possible to arrange the frames, which house the turbines, in the ideal orientations relative to the prevailing wind). Furthermore, in order to optimise the economics of an individual site, the spacing between individual turbines needs to be adjusted to achieve the optimum compromise between highest overall energy production from the site (normally indicating closer spacing of the turbines) taking account of the cost and scarcity of available land, and the productivity of each individual turbine (if turbines are too dose together, the productivity of each individual turbine is typically reduced, especially where turbines are arranged in lines at relatively small angles to the prevailing wind direction) taking account of the capital cost of each turbine. The desirability of optimising the balance between these factors for different sites, and even within an individual site where, for instance, different wind strengths on different parts of the site will affect the optimum spacing locally, implies that frames containing turbines of fixed spacings will not be an ideal solution.

Furthermore, if maintenance of individual turbines is required, or if upgrades to turbine design (such as more efficient turbine blade shape) become available, it may be desirable readily to be able to "swap out" individual turbine units for new, refurbished or upgraded ones. Furthermore it would be desirable for this to be achievable quickly and with the minimum of expensive ancillary equipment such as cranes or other heavy lifting equipment.

Thus there exists a need for a lightweight and reconfigurable wind farm system which can readily be modified as required to achieve the optimum spacing between turbines on different parts of the site without requiring re-siting of individual poles and associated foundations for each turbine, and in which individual turbines can be removed for maintenance and upgraded or re-sited as required with the minimum of time and cost.

SUMMARY OF THE INVENTION

The present invention addresses the above need by the use of a system comprising at least one elongate structural member, which may take the form of a rail, tube, beam, bar, girder or other known structural form, to which a plurality of wind turbine modules (each module° comprising at least a wind turbine, and optionally also an electrical generator, mounting system, and other ancillary equipment) are attached, using attachment and detachment mechanisms which allow the spacing between individual modules to be altered, either in discrete steps or continuously. In advantageous and preferred embodiments of the present invention two main elongate structural members are joined together to form a frame, by means of fixed attachments to at least two shorter elongate structural members perpendicular to, and disposed between, said two main elongate structural members. Individual vertical axis wind turbine modules are disposed between the two main elongate structural members, and attached to the frame in such a way that they can readily be removed and replaced or repositioned on the frame or on another similar frame. Furthermore, preferred embodiments of the present invention comprise a plurality of individual wind turbine modules each of which is light enough and easy enough to handle that it can be installed by a single individual or a small team of individuals without the use of cranes or other heavy lifting equipment.

In some preferred embodiments of the invention, the said elongate structural members are arranged to be, in use, substantially horizontal, or substantially parallel to the ground or other surface on which the array of modules is located. It may however be possible that said elongate structural members are arranged to be, in use, upright, or substantially vertical, or substantially perpendicular to the ground or other surface on which the array of modules is located. Arrays may thus be contemplated that extend upwards, rather than along the ground or other surface on which they are mounted. The where vertical axis wind turbines are employed, they may be arranged to rotate about axes that are non-vertical or even substantially horizontal, although substantially vertical turbine axes are generally preferred for their substantial independence of the wind direction.

Preferred embodiments of the invention are configured to be raised on poles of less than I 5m height, and therefore to be visually unobtrusive compared to conventional wind farms, whose turbines may reach considerably more than 10Dm in height. The arrays of modules according to preferred embodiments of the present invention are generally able to be erected from ground level by small teams of workers, preferably without the use of cranes, and able to be carried to, and within, sites where there are small access roads or even no access roads at all. The modular nature of the system also enables the relocation of individual modules and the addition, removal, or replacement of modules with relative ease.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 is a perspective view of a horizontal axis wind turbine module mounted on an elongate structural member Fig. 2 is a perspective view of a vertical axis wind turbine module comprising a turbine blade and an electrical generator, rotatably mounted on an elongate structural member Fig. 3 is is a perspective view of a vertical axis wind turbine module comprising two coaxial vertical blades and a generator, rotatably mounted on an elongate structural member Fig. 4 is a perspective view of a vertical axis wind turbine module, similar to that illustrated in Fig 2, but with the shaft extended through mountings on two separate elongate structural members below the turbine blade Fig. 5 is a perspective view of a vertical axis wind turbine module, mounted according to an advantageous embodiment of the present invention, whereby the module is rotatably mounted on two separate elongate structural members, one above and the other below the turbine blade, using mountings which can be repositioned at discrete points along the length of the elongate structural members.

Fig. 6 is a perspective view of a system similar to that of Fig. 5, but where the mountings can be repositioned at any point along the elongate structural members.

Fig. 7 is a perspective view of a mounting bracket and elongate structural member similar to that of Fig.5 Fig. 8 is a perspective view of a mounting bracket and elongate structural member similar to that of Fig. 6 Figs. 9 and 10 are schematic side views of mounting brackets similar to those of Figs. 7 and 8, showing details of how they may be attached to elongate structural members Figs. 11 and 12 are schematic side views of mounting brackets similar to those of Figs. 9 and 10, but comprising examples of a quick attachment and release mechanism.

Fig. 13 is a schematic side view of a frame and a set of vertical axis wind turbine modules according to a preferred embodiment of the present invention, illustrating how individual modules may be attached and positioned on the frame as required Figs. 14 to 16 are schematic side views of a series of frames comprising various arrangements of vertical axis wind turbine modules, at varying spacings.

Figs. 17 and 18 are schematic side views of identical frames comprising different numbers of identical vertical axis wind turbines.

Fig. 19 is a schematic side view of a frame comprising vertical axis wind turbine modules of different designs and spacings from one another.

Fig. 20 is a schematic side view of a series of frames, joined to form a fence, and raised on support poles, and comprising vertical axis turbine modules with a range of spacings.

Fig. 21 is a plan view of a wind fence comprising turbine modules attached to straight elongate structural members wherein different sections of the fence are at different angles to the prevailing wind and have different spacings between neighbouring turbine modules Fig. 22 is a plan view of a wind fence comprising turbine modules attached to curved elongate structural members, wherein different parts of the fence are at different angles to the prevailing wind and have different spacings between neighbouring turbine modules Fig. 23 is a plan view of a branched structure comprising multiple elongate structural members with attached wind turbine modules at various spacings according to orientation with respect to the prevailing wind, and to sheltering from the prevailing wind by obstades such as buildings or trees

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system for capturing energy from the wind, comprising at least one elongate structural member supporting a plurality of wind turbine modules, wherein each of said wind turbine modules comprises at least one wind turbine, and is provided with a means of attachment to, and detachment from, said at least one elongate structural member at a plurality of positions along the length of said at least one elongate structural member, such that the numbers and spacing of said wind turbine modules supported by said at least one elongate structural member may be varied.

Preferably the elongate structural members are fabricated from aluminium, or an alloy containing a high proportion of aluminium. Aluminium and many of its alloys possess the desirable characteristics of having high strength to weight ratio and low cost, making them idea) for structures such as those of the present invention, which should preferably be strong, light in weight, and low in cost. Aluminium and its alloys are also readily available as extruded lengths with many cross-sectional forms suitable for the application described in the present invention, such as box sections, beams and tubes. Additionally, they generally possess very good corrosion resistance, therefore not requiring painting or maintenance in outdoor applications such as the ones envisaged in the present invention. Other materials may, however, also be suitable including, but not limited to, steel, wood, reinforced concrete, or composite materials (for example comprising glass or carbon fibres embedded in a polymeric resin matrix).

Fig.1 illustrates an elongate structural member 1 to which is attached a mounting bracket 2, on which is mounted a horizontal axis wind turbine module comprising a casing 3 and a horizontal axis wind turbine 4.

Embodiments of the present invention employ mounting brackets which can readily be attached and detached from the elongate structural member, and which can be slid or otherwise relocated to different positions along said elongate structural member. Optionally, said horizontal axis wind turbine module housing is rotatably coupled to said mounting bracket, enabling said horizontal axis wind turbine module to rotate to face the oncoming wind.

Fig. 2 Illustrates an altemative arrangement, similar to that of Fig.1, except that the wind turbine module comprises a vertical axis wind turbine blade 5, rotatably mounted via a shaft 6, to the mounting bracket 2, which may optionally comprise a bearing housing for said shaft. Also illustrated in Fig. 2 is an electrical generator 7 coaxial with, and coupled to, said vertical axis wind turbine blade. The arrangement of Fig. 2 can result in a high bending moment on the shaft 6 in a strong wind, however altemative arrangements may mitigate this effect: In Fig. 3, a second vertical axis turbine blade below the mounting bracket larpely balances the bending moment from the blade above it, and in Fig. 4 a pair of elongate structural members 1, arranged one below the other, and each with an attached mounting bracket 2, better supports the shaft 5, helping to counteract the bending moment during strong winds.

In Figs. 2 and 3, and subsequent illustrations, the profile of the wind turbines 5 as illustrated is not necessarily representative of the actual turbine profile to be used in practice. The detailed design and actual blade profiles of the individual turbines may, for example, be selected from a variety of known designs. The turbines may be of known single bladed or multiple bladed types, but preferably are of a aself starting design in that each turbine possesses the capability to reach its optimum operating rate of rotation from the wind flow only, without an initial requirement for a driving motor to spin it up to speed. An example of a suitable profile for the blades of said vertical axis turbines is that described in the patent US5494407, said profile being relatively efficient, strong, and straightforward to construct from lightweight sheet materials, the preferred material for construction of the blades in the present invention being aluminium or an aluminium alloy. The bearings may be of any known type, but standard sealed ball bearing assemblies of suitable dimensions are preferred.

Electrical generators employed in embodiments of the present invention may also be of any known type, including those which produce alternating or direct current, though in advantageous embodiments, single phase or three phase air-cored axial or radial flux permanent magnet alternators, optionally comprising full-wave rectifier circuitry so as to produce direct current (DC) output, are preferred.

Advantageous and preferred embodiments of the present invention employ an arrangement similar to that illustrated in Fig. 5 and Fig. 6, wherein vertical axis wind turbine modules are employed, and shafts 6 at both ends of each blade are rotatably coupled to a pair of elongate structural members (I a in Fig.5 or lb in Fig.6), one above and one below the wind turbine blade, via corresponding pairs of mounting brackets (2a in Fig.5 or 2b in Fig.6) In Fig. 5, the pair of elongate structural members I a thus employed contain holes 8 at intervals along their lengths, into which bolts, locating pins or other locking devices 9a may be inserted, through corresponding holes in mounting brackets 2a, thus fixing said vertical axis wind turbine modules in a discrete or finite range of positions. The holes 8 are arranged to be in corresponding positions on the upper and lower elongate structural members to allow each vertical axis wind turbine module to be positioned with its rotation axis accurately perpendicular to the elongate structural members. Similar arrangements to that illustrated may be employed whereby the holes in the elongate structural member may replaced by slots, tabs, grooves or other locating features, and wherein the mounting brackets comprise corresponding locating devices capable of engaging with said locating features The arrangement illustrated in Fig. 6 is similar to that of Fig. 5, except that the elongate structural members lb do not contain holes, and the mounting brackets 2b are of a slightly different design, wherein damping bolts or other fixings 9b are used to lock the mounting brackets 2b in position. This may be achieved, for example, by slightly compressing the mounting bracket sides, causing them to grip the elongate structural members I b, or by an alternative means such as cams being rotated and pressed against said elongate structural members, or by other means. Such arrangements enable the wind turbine modules to be fixed at an infinite range of positions along the lengths of said elongate structural members, without the constraint of discrete locating points. Said arrangements thus allow greater flexibility in positioning the wind turbine modules, and may be more suitable for wind turbine module designs which do not require the shafts 6 to be accurately perpendicular to the elongate structural members. If accurate positioning is required, however, this may still be achieved by the use of, for example, ruled guide marks on the elongate structural members, or by the use of wind turbine module designs which are constructed to be self-aligning. It should be noted that the turbine modules in preferred embodiments of the present invention, as illustrated in Fig. 5 and Fig. 6 also comprise an electrical generator 7, coaxial with the wind turbine blade and directly driven by it.

Advantageous embodiments may comprise modules with the generator above or below both elongate structural elements, as illustrated or, like the turbine blades themselves, between the pair of elongate structural elements. The lower elongate structural members and associated mounting bracket arrangements illustrated in Figs. 5 and 6 are shown in Figs. 7 and 8 respectively, with the turbine blades, electrical generators and upper elongate structural members removed for clarity. Figs. 9 and 10 are schematic side views illustrating the detail of how such mounting brackets and damping arrangements might operate in practice, also indicating how the bearings 10 and shafts 6 for the wind turbine module might be accommodated into the mounting brackets. Figs. 11 and 12 illustrate corresponding arrangements to Figs 9 and 10 respectively, except that the bolts 9 used to secure the mounting brackets 2a and 2b in Figs. 9 and are replaced by spring clips 11 to secure mounting brackets 2c and 2d, as an illustration of a possible rapid attachment and release mechanism. It will be understood that the cases illustrated are example fixing arrangements, and many other designs for mounting brackets, elongate structural members and, where required, ancillary fixings such as bolts, dips, or other devices may be employed to achieve the same ends, within the scope of the present invention.

Fig. 13 illustrates a preferred embodiment of the present invention, wherein a plurality of vertical axis wind turbines is attached to a rectangular frame, said rectangular frame being constructed by joining two main elongate structural members I together with at least two shorter elongate structural members 12 disposed between them. The arrow 13 indicates how individual wind turbine modules may be added at the desired positions along the frame, and the arrows 14 indicate how the modules may be repositioned once attached to the frame. Figs. 14 to 16 illustrate examples of how the frames, once populated with similar numbers of turbine modules, may have the spacing of those modules arranged to suit differing requirements, for example uniform spacing, higher density of modules at one end of the frame, or lower density of modules in the middle of the frame, according, for example, to the requirements of a particular site when in service.

Figs. 17 and 18 illustrate how a higher or lower density of modules may be employed on a similar frame, as required, and Fig. 19 illustrates how a single frame may accommodate wind turbine modules of different designs, shapes and spacings, as might be required, for instance, to control air flow, or due to aesthetic or other considerations.

Fig.20 is a schematic side view of a plurality of frames containing wind turbine modules according to a preferred embodiment of the present invention, joined together to form a wind fence and raised on poles 15, as might advantageously be employed at a wind farm or other commercial site for the generation of electricity. The figure illustrates how the spacing of the individual turbine blade modules may be varied within and between neighbouring frames.

In service, it is envisaged that such a wind fence would ideally be oriented perpendicular to the prevailing wind, in order to maximise the amount of wind energy converted to electricity. In practice, this may not always be possible, due to topographical factors, restricted access to parts of the site, and other considerations. Fig. 21 is a plan view of a wind fence constructed from frames populated with vertical axis wind turbine modules according to a preferred embodiment of the present invention, indicating the orientation of its various sections relative to the prevailing wind direction 16. As can be seen from the figure, in order to optimise the spacing of the wind turbine modules according to the position and orientation of the various sections of the wind fence, the spacing between adjacent wind turbine modules has been arranged to be smaller for sections of the fence in which the elongate structural members are closer to perpendicular to the prevailing wind, whereas the turbines are further apart on sections for which the elongate structural members are closer to parallel to the prevailing wind direction. Also illustrated is the effect of a building 17 sheltering a section of the fence from the prevailing wind. Here the density of turbine modules downwind of the building has been reduced, since turbines placed in these locations would be less productive than those in unsheltered regions.

It is not necessary for the elongate structural members to which the turbine modules are attached to be straight. Fig. 22 illustrates an example of a wind fence constructed from curved members, again employing the same optimisation principles, by spacing the turbine modules closer together in the most productive sections (those most close to perpendicular to the prevailing wind direction) of the fence.

Fig. 23 illustrates a branched wind fence, comprising a number of frames in different orientations and containing different densities of wind turbine modules according the degree of sheltering of, or from, different parts of the fence, or the degree of sheltering from buildings 17 or trees 18.

A preferred embodiment of the present invention is a system for capturing energy from the wind, comprising two parallel elongate structural members, one of said elongate structural members being substantially above the other, with a plurality of wind turbine modules comprising vertical axis wind turbines being disposed between said elongate structural members, each of said turbines being rotatably coupled both to the elongate structural member above it and to the elongate structural member below it, by means of mounting brackets capable of attachment to, and detachment from, said elongate structural members at a plurality of positions, such that the numbers and spacing of said wind turbine modules member may be varied, and each of said turbines directly driving an individual electrical generator, coaxial with said turbine. Preferably the two main elongate structural members are joined together to form a frame, by means of fixed attachments to at least two shorter elongate structural members perpendicular to, and disposed at intervals between, said two main elongate structural members, and preferably said frames are raised on support poles above the ground or other surface to which the system is attached. In such preferred embodiments the total weight of each individual wind turbine module is between 0.5kg and 50kg, preferably between 1kg and 25kg, very preferably between 2kg and 15kg. In preferred embodiments the height of individual turbine modules is between 0.1 and lOm, preferably between 0.2 and 5m, very preferably between 0.5 and 2.5m. Further, in preferred embodiments the diameter of individual turbine blades is between 0.05 and 2.Om, preferably between 0.1 and I.Om, very preferably between 0.2 and O.5m.

Other turbine module configurations, weights and dimensions can also be envisaged, however, which nevertheless fall within the scope of the present invention An advantageous aspect of the present invention, as indicated in Figs. 21 to 23 and described above is that frames containing wind turbine modules may be linked together to form wind fences. In such structures, neighbouring frames, preferably raised to a height of at least several metres above ground level on upright supporting poles, are preferably arranged relative to one another such that the shape of the array of connected frames braces the structure effectively against winds arriving from all directions, to an extent where the bracing obviates the need for guy wires or heavy supporting poles.

Further, as indicated in Fig.23, each frame may be connected to more than two other frames such that, for instance, branching lines of frames may be formed and these, in turn, may be connected to other lines of frames. It is envisaged that lines and networks containing any number of frames may be produced in this way, containing arrays of any number of turbines modules A further aspect of the present invention is that each frame may be fixed to a pair of supporting poles, one at each end of the module, each supporting pole itself being hinged at its other end to a ground attachment point. Each frame is preferably of a size and weight which enable it to be raised into position by a small group of workers, either manually or with a winch or by other simple, ground operated means but preferably without the need of a crane or other heavy lifting equipment. Multiple tiers of such frames, or frames comprising a plurality of elongate structural members supporting wind turbine modules may be envisaged such that, for example, multiple rows of wind turbine modules, one row above another, may be supported on a single set of supporting poles.

Although preferred embodiments of the present invention comprise vertical axis wind turbine modules in which each wind turbine directly drives an individual electrical generator, other arrangements whereby the turbines indirectly drive generators via gears or by other means, including arrangements in which multiple turbines are linked to single generators or in which multiple generators are linked to single turbines, are also possible within the scope of the present invention.

Although preferred embodiments of the present invention comprise frames with parallel elongate structural members, arrangements wherein the elongate structural members are not parallel, and other modifications may be considered, due to requirements and circumstances at particular locations. It will be appreciated that, as well as the above described embodiments and examples, further designs and modifications will be possible which nevertheless fall within the scope and spirit of the present invention.

Claims

CLAIMS1. A system for capturing energy from the wind, comprising at least one elongate structural member supporting a plurality of wind turbine modules, wherein each of said wind turbine modules comprises at least one wind turbine, and is provided with a means of attachment to, and detachment from, said at least one elongate structural member at a plurality of positions along the length of said at least one elongate structural member, such that the numbers and spacing of said wind turbine modules supported by said at least one elongate structural member may be varied.
2. A system according to daim I, wherein each of said wind turbine modules is provided with a means of attachment to, and detachment from, said at least one elongate structural member at a discrete range of positions defined by locating holes, notches, tags or other features within or attached to said at least one structural member at intervals along its length, by means of at least one mounting bracket, damp, or other mechanism which engages with said locating holes, notches, tags or other features to lock each of said modules in the desired position.
3. A system according to claim 2, wherein the distance between successive locating holes, notches, tags or other features along the length of said at least one structural member is less than the diameter of the rotor blades in said wind turbine modules or is less than the minimum spacing at which adjacent wind turbine modules touch one another when supported on said at least one elongate structural member.
4. A system according to claim 1, wherein each of said wind turbine modules is provided with means of attachment to, and detachment from, said at least one elongate structural member at any desired position along the length of said at least one elongate structural member by means of at least one mounting bracket, clamp or other mechanism which does not require discrete attachment locations on said at least one elongate structural member
5. A system according to any preceding claim, comprising a mechanism or mechanisms such as at least one damp, cam, bolt, pin, peg, catch, hook, spring actuated device or other known rapid attachment and release mechanism which allows rapid attachment of wind turbine modules to, and rapid detachment of wind turbine modules from, said at least one elongate structural member.
6. A system according to any preceding claim, comprising wind turbines from the class of turbines known as vertical axis wind turbines, said turbines being characterised by an ability to capture energy substantially equally efficiently from wind arriving from any direction substantially perpendicular to the axis of rotation of the turbines.
7. A system according to claim 6, wherein the attachment mechanisms of said vertical axis wind turbines to the at least one elongate structural member comprise rotatable couplings housed in mounting brackets.
8. A system according to any preceding claim wherein said at least one elongate structural member is arranged to be, in use, substantially horizontal or substantially parallel to the ground or other surface on which the system is located.
9. A system according to any preceding daim wherein said at least one elongate structural member is arranged to be, in use, substantially upright or substantially perpendicular to the ground or other surface on which the system is located.
10. A system according to any preceding claim, wherein the at least one elongate structural member, in service, is raised above the level of the ground or away from any other surface on which the system is located, by means of a pair of supporting poles, one end of a first supporting pole being fixedly attached to a proximal end of said at least one elongate structural member, and one end of a second supporting pole being fixedly attached to a distal end of said at least one elongate structural member
11. A system according to any preceding claim, comprising two parallel elongate structural members, one of said elongate structural members being substantially above the other, and with a plurality of wind turbine modules comprising vertical axis wind turbines being disposed between said members, each of said turbines being rotatably coupled both to the member above it and to the member below it, and each of said turbines directly driving an individual electrical generator, coaxial with said turbine.
12. A system according to any preceding claim, in which the total weight of an individual wind turbine module is between 0.5kg and 50kg, preferably between 1kg and 25kg, very preferably between 2kg and 15kg.
13. A system according to any preceding claim, in which the height of individual turbine modules is between 0.1 and lOm, preferably between 0.2 and 5m, very preferably between 0.5 and 2.5m
14. A system according to any preceding claim, in which the diameter of individual turbine blades is between 0.05 and 2.0m, preferably between 0.1 and 1.Om, very preferably between 0.2 and 0.5m
15. A system according to any preceding claim, wherein individual turbine modules within an installation are not all at equal distances from their nearest neighbours.
16. A system according to any preceding claim, in which not all wind turbine modules in the system are of identical design or dimensions.
17. A system according to any preceding claim wherein a plurality of frames supporting wind turbines are joined to form a fence
18. A system according to any preceding claim, wherein a plurality of frames are joined to form a branched network, ring, or other linked structural form.
19. A system according to any preceding claim, comprising a plurality of elongate structural members, arranged substantially one above another, and to which are attached a plurality of wind turbine modules such as to provide a plurality of rows of wind turbine modules at different heights or a planar array of wind turbine modules
20. A system according to claim 19, wherein said elongate structural members are joined to one another by support poles or perpendicular elongate structural members so as to form a frame.