WO2008009920A2

WO2008009920A2 - Wind turbines

Info

Publication number: WO2008009920A2
Application number: PCT/GB2007/002697
Authority: WO
Inventors: Stephen Foster
Original assignee: Stephen Foster
Priority date: 2006-07-17
Filing date: 2007-07-17
Publication date: 2008-01-24
Also published as: GB2440264A; GB0713903D0; WO2008009920A3; GB2440264B

Abstract

A rotor is mounted in a channel formed across the apex of a pitched roof. The rotor is movable about a vertical axis so as to face a prevailing wind direction. The rotor is arranged so as to face down the pitch of the roof, and a portion of the rotor extends below the apex of the roof, as this has been found to improve power generation. In another embodiment (Figure 1), the rotor is mounted between tapered wind channels for directing air towards the rotor.

Description

Wind Turbines

The present invention relates to wind turbines, and more particularly, but not exclusively, to a wind power assembly for mounting on a pitched structure.

Wind power is a known source of renewable energy. Indeed, large scale wind farms are becoming an increasingly common feature throughout the developed world. More recently, there has been a move towards the use of smaller wind turbines, sometimes referred to as micro-wind turbines, in the domestic or urban environment.

The majority of micro-wind turbines available on the market are 'propellor' type turbines intended to be mounted on a pole or post at an elevated position on a building. However, they are known to suffer from a number of disadvantages, such as instability in high wind conditions, low power output and noise pollution.

It is an object of the invention to provide an alternative assembly that will address or significantly mitigate one or more of the disadvantages of conventional micro-wind turbines.

According to one aspect of the invention, there is provided a wind power assembly for mounting on a pitched structure, the assembly having a rotor for generating wind power, the rotor being rotatable about an axis of rotation which defines a horizontal datum, the assembly further having at least one guide passage for directing wind towards the rotor, wherein the flow path along the passage is inclined relative to said horizontal datum, so as to extend in the general pitch of the structure.

The inclined flow path referred to above can be positioned so as to take advantage of the magnified wind velocity produced by the shape of the pitched structure, e.g. so as to capture wind as it travels up and over the pitch of the roof. It is preferred if at least one additional guide passage is also provided for exhausting air away from the rotor.

In a particularly preferred embodiment, the rotor is arranged centrally between opposing guide passages, such that air entry and exit may occur through the passages on opposite sides of the assembly device to take advantage of pressure differences on opposite sides of the roof apex, since this may be useful in increasing the power output of the assembly. However, in alternative embodiments the air stream may be discharged to atmosphere through a centrally positioned venturi duct, for example.

Preferably the inlets of said guide passages define a generally circular array about said rotor. Such an embodiment is therefore able to maximise the capture of wind from any generally radial direction relative to said rotor.

In a preferred embodiment, the or each guide passage consists of a conduit of reducing area towards the rotor, which acts to increase the wind velocity progressively towards the rotor. This is particularly preferred for those embodiments having exhaust guide passages, wherein after passing through the rotor air is exhausted through one or more guide passages on the opposite side of the assembly, each exhaust passage being divergent away from the rotor. The overall pathway through the assembly approximates to a venturi wherein the airstream is convergent towards the rotor, at which point the air speed and power output are at a maximum, assisted by the or each divergent exhaust passageway.

Each guide passage preferably includes a closure or upper surface which is moveable to regulate the velocity of wind travelling through the rotor.

The plane of the rotor blades may be arranged at an angle to said horizontal datum, e.g. so as to face down towards the pitch of the roof.

According to another aspect of the invention, there is provided a roof construction having an inclined roof surface, and a wind power assembly including a rotor and a wind channel for directing air towards said rotor, wherein the wind channel extends down said inclined roof surface.

In a preferred embodiment, the roof construction is generally A-shaped, having a pitch preferably above 15°. It is preferred if the rotor is arranged at the apex of said roof construction. The wind power assembly may include wind channels extending down either side of the roof construction, more preferably in a radial array, for the capture of wind travelling along the surfaces of the roof from any direction.

By providing a wind power assembly for mounting on the apex (ridge) of a pitched roof with wind channels extending down each side of the roof from a central rotor, maximum advantage can be taken of the increase in wind velocity resulting from deflection of incident wind by the lower building and roof structure. It can also take advantage of pressure differences on either side of the roof structure or the assembly, for example a positive pressure occurring on the windward side and a negative pressure (suction) on the leeward side.

Further increases in air stream velocity may occur 'within' the wind power assembly, in particular if the wind channels are generally tapered so as to converge towards the rotor, and this is a particularly advantageous feature of preferred embodiments of the invention.

The rotor may be of a generally windmill or propeller type construction having radial blades of plane or aerodynamic shape, as opposed to a vane of water wheel type construction. However, in other embodiments it may be preferred to utilise a water wheel type vane (preferably, but not exclusively, of relatively short longitudinal length), arranged so as to rotate in response to a flow of air hitting one or more of the paddles/blades of the vane.

The plane of the rotor blades may be arranged so as to face down the pitch of the roof. A moveable closure member may be incorporated, for example as part of the upper wall of the guide passage, to allow the inlet area of the channel to be adjusted, for regulating the airflow to the rotor.

Preferably, the rotor is substantially enclosed in the assembly, thereby reducing noise pollution from the assembly. Moreover, the rotor can be thereby shielded from the direct effects of rain and snow, for example.

Vibration and resonance effects produced by the assembly can be reduced or eliminated by supporting the assembly on damping material, arranged to impede transmission to the supporting roof structure.

In those embodiments having upper closure members for said wind channels, the assembly can be closed to provide a streamlined upper surface which minimises lateral and lifting forces on the assembly and the supporting roof structure in high winds. Moreover, the closure members can be used to support solar cells, for generating additional power from sunlight. In low wind conditions, the closure members may be orientated to receive maximum incident sunlight and maximise power production.

Grills can be provided within the channels to prevent birds and other wildlife from entering the assembly.

In summary, the above aspects of the invention provide a wind turbine associated with inclined channels for guiding air stream up towards the turbine. Most preferably, the assembly is intended to be mounted at the apex of a sloping roof or on another inclined structure defining an inclined plane, whereby the pathway of air towards the turbine is preferably up the inclined plane.

According to another aspect of the invention, there is provided a pitched structure incorporating a wind power generator, the pitched structure having a channel across which an airflow is intended to pass, and wherein the wind power generator comprises a bladed rotor mounted in said channel for generating power in response to a flow of air passing across said channel.

In preferred embodiments, the rotor is a horizontal axis rotor, e.g. of a general 'windmill' or propeller type construction having radial blades of plane or aerodynamic shape, as opposed to a vane of water wheel type construction. Again, other embodiments may utilise a water wheel type vane (preferably, but not exclusively, of relatively short longitudinal length), arranged so as to rotate in response to a flow of air hitting one or more of the paddles/blades of the vane.

Preferably, the blades of the rotor define a rotor plane, wherein the rotor plane can be arranged to face down the pitch of the structure. The angle of inclination may be in the region of 5 degrees to 30 degrees from vertical, although an angle of between 5 degrees and 20 degrees may be typical, e.g. 10 degrees or 15 degrees. The angle of inclination is optimised when the rotor plane is orthogonal with the pitch of the structure.

In preferred embodiments, the pitched structure is a roof having an apex, wherein the channel is preferably formed at said apex.

Where the rotor is a horizontal axis rotor, at least a lower portion of the rotor preferably extends below said apex. At the same time, it may be preferred if an upper portion of the rotor extends above said apex.

The channel is substantially U-shaped, V-shaped or L-shaped, and is preferably formed as a recess extending across the apex of the roof. The channel preferably has side walls having a curved profile in plan view for directing wind through the recess. Moreover, the base of the channel preferably has an outwardly convex surface.

In another embodiment, the channel may take the form of an L-shaped recess formed into the surface of the roof, below the apex of the roof. The rotor is preferably movable about a generally vertical axis to face a prevailing wind direction. The angle of inclination of the rotor plane may vary during movement of the rotor about said vertical axis.

The channel is preferably a retro-fit assembly for said pitched structure.

According to another aspect of the invention, there is provided a wind power assembly comprising a channel across which an airflow is intended to pass, and a rotor mounted in said channel for generating power in response to a flow of air passing across said channel.

The rotor is preferably a horizontal axis rotor, the rotor having blades which define a rotor plane, wherein the rotor plane is arranged at a minimum angle of 5 degrees to the vertical.

The channel preferably defines an upper limit and at least a portion of the rotor extends below said limit. Additionally, it may be preferred if at least a portion of the rotor extends above said limit.

Again, the rotor is preferably movable about a generally vertical axis to face a prevailing wind direction.

There is also provided a method of modifying a roof structure to incorporate a wind power assembly, comprising the steps of removing a section of roof structure so as to form a recess in the roof structure and mounting a wind power assembly according to any of the above aspects of the invention.

Other preferred features and aspects of the invention will be readily apparent from the dependent claims and the following description of several preferred embodiments, which is made, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic perspective view of a preferred wind power assembly mounted on the ridge of an 'A' shaped pitched roof;

Figure 2 is a partially exploded view of the assembly shown in Figure 1, illustrating the modular construction of the assembly;

Figure 3 is an exploded view of the bridge unit and rotor of the assembly shown in Figure 1;

Figure 4 is a plan view of the assembly shown in Figure 1;

Figure 5 is a schematic view of the central body of the assembly;

Figure 6 is a partial-sectional view along the dotted line in Figure 4;

Figures 7 is a simplified schematic view of wind channels with hinged closures for use in the assembly of Figures 1, 2 and 4;

Figures 8 to 11 are schematic views of alternative wind channels for use in the assembly of Figures 1 , 2 and 4.

Figure 12 is a schematic perspective view of a further embodiment of a wind power assembly, including a fixed vertical axis rotor;

Figure 13 is an exploded view of the wind power assembly in Figure 12;

Figure 14 is a simplified schematic view of a wind channelling body for use in the assembly of Figures 12 and 13, showing an arrangement of hinged blinds within the channels; Figure 15 is a schematic partial cross-sectional view through a further embodiment of a wind power assembly, wherein the rotor is mounted in a rotatable outlet of the assembly;

Figure 16 is a schematic perspective view from above the assembly in Figure 15, with a transparent view through the rotor housing.

Figure 17 is a schematic part-transparent view of a roof structure, wherein the apex of the roof structure has been modified for receiving a wind assembly;

Figure 18 is a schematic perspective view of a further embodiment of a wind power assembly, wherein the rotor is mounted in a venturi-shaped passageway between simplified wind channelling bodies;

Figure 19 is a perspective view of a further embodiment of a wind power assembly, indicating that the wind direction is from the front of the house;

Figure 20 is a side sectional view of the assembly in Figure 19;

Figure 21 is a perspective view of a modified substructure for a roof construction;

Figure 22 shows the assembly of Figure 19 mounted on the substructure of Figure 21 ;

Figure 23 is a perspective view of an alternative wind power assembly;

Figure 24 is similar to Figure 23, but including a profiled surround for the rotor; and

Figure 25 is a perspective view of the wind power assembly from Figure 19 mounted at the gable end of a roof structure.

Referring firstly to Figures 1 to 4, a wind power assembly for use on a sloping surface is indicated generally at 100. As can be seen, the assembly 100 is mounted over the apex of a pitched roof structure 200 and is shaped specifically to be supported by the inclined surfaces 202, 204 on either side of the apex ridge 206 of the roof structure 200. As such, the base geometry of the assembly 100 closely follows the profile of the roof upon which it is mounted.

As can be seen from Figure 4, the overall shape of the assembly 100 is generally circular in plan view, having a preferred diameter of between 1.0 and 3.0 metres for domestic buildings. However, larger diameter assemblies could be applied to larger buildings of suitable structure.

In this embodiment, the assembly 100 is of modular construction and comprises a pair of wind channelling bodies 110 mountable either side of a central rotor body or bridge body 120, one on either side of the ridge 206. A rotor assembly 130 is supported in the bridge body 120.

As can be seen from Figure 2, the wind channelling bodies 110 are generally semicircular in plan view, although they may be of any suitable shape, for example semi-elliptical or semi-polygonal. Each body 110 defines a plurality of wind channelling passages 112 having a base 114, side walls 116 and an upper wall 118. The passages 112 themselves define ducts which taper from an inlet end to an outlet end, wherein the cross sectional area of the inlet end is greater than the cross-sectional area of the outlet end. The result is pairs of generally opposing conduits which are divergent from one another away from the centre of the assembly, so as to define passageways through the assembly which approximate to a venturi, with a narrow throat section arranged between the wider inlet ends.

In the illustrated embodiment of Figures 1 to 4, the base walls 114 of the wind passages 112 are provided by a common base structure of the respective wind channelling body 110, which could constitute a generally planar frame, the underside of which may be configured to match the external profile of the inclined roof surfaces 202, 204. Typically, cushioning pads or a sheet or strips of cushioning material (not shown) can be provided between the underside of each wind channelling body 110 and the adjacent roof surface 202, 204, for spreading the load of the assembly 100 and reducing the transmission of noise and vibration from the assembly 100 to the roof structure 200, in use.

The bridge body 120 is supported generally over and along the ridge 206 of the roof structure 200 by the wind channelling bodies 110, so as to provide an air gap between the assembly 120 and the ridge 206.

As can be seen clearly from Figure 5, the bridge body 120 includes a thin base wall 122 separating a pair of end compartments 124, which can be used to contain electrical control equipment for the assembly 100. The rotor assembly 130 is mounted in the cavity between the end compartments 124.

The bridge body 120 has outer walls 128 which are intended to nest against and be fixed to the end faces of the wind channelling bodies 110, in use.

It will be appreciated that different roof structures may have different angles at their apex and that the angles of inclination of the two sides of the roof may differ from one another. It is therefore desirable to construct the assembly from modular elements of the kind described above, whereby the wind channelling bodies 110 may remain of constant dimensions for a particular design and size of assembly 100, and wherein any differences in roof angles from a standard pitch roof design can be accommodated by changing the shape of the bridge body 120. Typically, this will involve changing the angle of inclination of the outer side walls 128 of the bridge body 120 (see Figure 5).

The height of the compartments 124 may be uniform along the length of the bridge body 120 or may preferably increase towards the cavity, so as to have upwardly inclined outer surfaces which may assist in reducing forces on the assembly 100 in high wind conditions.

The bridge body 120 is preferably built from lightweight sheet materials, for example aluminium, plastics, wood, composite materials etc. secured over a more rigid framework. Connections between the bridge body 120 and the wind channelling bodies 110 would therefore be via the rigid framework.

It should be noted that each wind channelling body 110 defines a common outlet 140 for the wind passing through the respective wind passages 112 to said rotor assembly 130. The position of the common outlet 140 is configured to correspond to the position of the cavity between the end compartments 124 of the bridge body 120.

In use, the wind passages 112 direct incident wind upwardly along the direction of incline of the building roof towards wind deflecting baffles 186 provided adjacent the rotor assembly 130. The air is thereby diverted and guided into the rotor assembly 130.

Any number of wind passages 112 may be used in each channelling body 110. However, four passages on either side of the roof structure are most preferred, in order that, regardless of the wind direction, at least two passages 112 are always positioned to capture the effect of the wind.

Conceivably, the wind channelling bodies 110 may include different numbers of wind passages 112 on either side of the roof structure 200, to maximise power output on a pitched structure of complex geometry. Equally, the wind passages 112 in one body 110 may differ in dimension from the wind passages in another body 110, and even the dimensions of wind passages 112 in a single body may differ in configuration from one another.

The distal end of the side walls 116 of the passages 112 may extend beyond the base wall 114 to increase the capture area of the inlet openings, and may be rounded to produce an aerodynamic shape to further reduce the forces on the assembly 100.

The upper wall 1 18 of each passage 112 is preferably a single moveable member, referred to hereafter as a 'moveable top door'. In this embodiment, the moveable top door is hinged at its inner (narrow) end, so that the inlet area of each passage 112 can be varied according to the strength of the prevailing winds. For example, in low wind conditions the moveable top door could be adjusted to be fully open, as shown on the right hand side of Figure 7, to capture the maximum incident air flow. However, in high wind conditions the moveable top doors could be closed, as shown on the left hand side of Figure 7, in order to reduce the flow of air into the assembly 100, thereby protecting the rotor assembly 130 from damage.

The moveable top doors can be programmed to change their positions automatically, at fixed time intervals, and/or can be controlled electronically according to measurements of wind direction and/or power output from the assembly. A wind vane mounted on top of the assembly can be provided for determining wind direction, for example.

The mechanism for operating the moveable top doors could be electro-mechanical, pneumatic or hydraulic, and the moveable top doors may be operated in unison or independently, as required.

In the illustrated embodiment of Figures 1 to 4, the moveable top doors are shaped to have a curved outer edge, gradually becoming more flattened towards the hinged end, as can be seen in Figure 7. This shape of door ensures that some air may enter the assembly 100 when the door is in the fully closed position, and the assembly 100 is thus able to generate electricity in all wind conditions. It also provides a large inlet area without the need for high side walls, which would increase the forces on the assembly 100 in high wind conditions. The curved design also imparts strength to the door, reducing the likelihood of damage in high winds.

As the moveable doors open and close the curved inlet end of each door moves through an arc with respect to the adjacent side walls, as shown by the broken lines in Figure 7. The horizontal distance between corresponding points along these broken lines must remain constant, and slightly greater in magnitude than the width of the door at these points i.e. X = Y in Figure 7 so that gaps between the door and side walls 116 are minimised in all door positions. This necessitates that the width of any passage 112, at the inlet end, must be greater at the bottom than at the top. In order to achieve this the included angle formed by each side wall 116 with the base wall 114 must be less than 90° producing outer end walls of increasing thickness from bottom to top. This effect may be reduced by changing the design of the hinged end of the moveable doors, maintaining the basic door design but lowering the position of the hinge.

The inner end of the side walls 116 may remain of uniform thickness.

It should be noted that sub-walls or baffles may be included in the wind passages 112, in order to maximise the capture of incident wind, and to improve the flow of the captured air stream, encouraging laminar flow and reducing turbulence.

Figure 8 shows two examples of subwall design. Figure 8a shows a sub-wall 150 provided along the centre line of the wind inlet passage, creating two separate sub-passages within the wind passage 112. This also provides support for the door in high wind conditions when the door is fully closed. Note that this design does not provide completely separate sub-passages when the moveable door is in its open position.

An alternative example is shown in Figure 8b, wherein a baffle member 152 depends from the door and is received in a slot provided in the sub-wall 150 as the door opens and closes. An advantage of this construction is that the baffle member 152 provides significant strengthening of the door panel. *-

Further alternative designs incorporating extendable or telescopic side walls are shown in Figures 9 to 11.

In Figures 9 and 10, baffles 154 are arranged to slide radially in and out of slots in the side-walls 116, and may be connected via a linkage mechanism 156 to the inlet end of the moveable doors. This design greatly increases the capture area of the device in low wind conditions and reduces the level of exposure of the device and the visual impact in high wind conditions. In Figure 1 1, a baffle 158 is moveable in a vertical plane, via a linkage mechanism 160, with the doors, and hinged at the inner ends. The advantage of this arrangement is that the inlet end of the side-walls 116 may be reduced in height, significantly reducing the vertical profile of the assembly 100 in high wind conditions.

In each of the designs shown in Figures 9 to 11 a drive mechanism may be applied to either the baffles or moveable doors.

Now, with particular reference to Figure 6, it can be seen that the rotor assembly 130 contains a plurality of blades 132, which extend from a hub 134 rotatably supported between a pair of fixed truncated cones 136, about a shaft 138. An electrical generator 170 for the assembly 100 is housed in one of said cones 136, to the left as viewed in Figure 6, and acts as a means of rotatably supporting one end of the shaft 138. The other end of the shaft 138 is supported in a bearing 172 in the other of said cones 136. The external surface of the cones 136 is intended to direct air towards the rotor blades 132.

In use, as the shaft rotates (due to wind driven rotation of the blades 132), the generator converts the rotation of the shaft to electrical energy in a generally conventional manner.

The configuration of rotor shown in Figures 1 to 4 and 6 would be expected to produce a relatively low rotation speed with high torque. However, a two-bladed high speed rotor with complex blades of aerodynamic shape or any other rotor may be substituted.

The rotor assembly 130 is supported in a rigid cage 180, via the ends of the cones 136, whereby the rotor blades are rotatable in the cage about a horizontal axis defined by the shaft 138. Furthermore, the cage 180 is supported on the base wall 122 of the bridge body 120 via a bearing assembly 192 and is itself arranged for rotation through at least 90° about a central vertical axis. Rotation of the cage 180 may be controlled, for example by a motor driven gear wheel 182 arranged in mesh with gear teeth 184 on the cage 180. This gear wheel may be mounted within a compartment 124 of the bridge body 120, with three equi-spaced undriven wheels 190 also provided to support and stabilise the cage and rotor assembly, preventing lateral movement whilst allowing rotation.

Guide baffles 186 are provided about said cage 180 for directing incoming air towards the rotor assembly 130. Other baffles may be provided around the rotor assembly 130 for diverting air into the rotor blades with minimal turbulence.

A cover 188 is provided over the rotor assembly 130, which may be manufactured from a transparent material e.g. a plastic, so that operation of the assembly can be viewed externally.

A typical operation of the assembly will now be described, in general terms.

During normal conditions, a wind vane on the assembly 100 detects the wind direction. Via an automatic control system, the cage 180 and rotor assembly can be caused to rotate about its vertical axis, to one of two operational positions.

For the majority of wind directions the air stream will approach from one or other side of the roof structure 200, and enter only one of the wind channelling bodies 110, before passing through the rotor assembly and exiting the assembly 100 through the opposite wind channelling body 110. For these wind directions the cage 180 and rotor is turned to the position shown in Figure 1, that is to say with the plane of the rotor aligned with the longitudinal axis of the ridge 206, referred to hereafter as the 'forward position'.

For wind directions aligned generally along the ridge 206, and within the range ± 20° from these directions, the air stream will enter both wind channelling bodies 110 simultaneously. For these wind directions the rotor must be turned through 90° about its vertical axis, so that the rotor faces the incoming air stream, to a position at least generally perpendicular to the ridge 206. This rotor position will be referred to hereafter as the 'side position'. If the rotor has been set to its 'side position' to take into account the prevailing wind direction (i.e. generally along the ridge 206), for example left to right as viewed in Figure 4, ambient air stream enters wind channelling passages 112A and 112B and receives little or no deflection from the roof surfaces 202, 204, and therefore experiences no significant increase in velocity. The air stream is however accelerated as it travels along the wind passages 112A, 112B, due to the convergence of the passages, before being deflected into the rotor assembly 130. The air stream passes through the rotor and exits the assembly via the wind passages 112D to 112G on the opposite side of the assembly 100.

The overall pathway for the air stream approximates to a Venturi passage and the speed of the air stream is thereby increased by a Venturi effect, produced by lateral compression of the incoming air. However, for the wind direction in this example there would be no pressure difference on each side of the roof structure, and therefore no additional benefit to power production.

If the wind blows at an angle of approximately 45° to the ridge 206, for example as indicated by line Wl in Figure 4, the automatic control system can be configured to tum the cage 180 and rotor to its 'forward position' (as shown in Figure 4). The ambient wind is deflected by the building and roof structure and is increased in velocity before entering wind passages 112B and 112C. The air stream is further accelerated by the wind passages 1 12, before being deflected into the rotor assembly 130, causing the rotor to turn and generate electricity via the generator 170 in a conventional manner. The air stream then exits through the passages 112 in the wind channelling body 110 on the opposite side of the roof structure.

The velocity of the air stream through the assembly 100 may be further improved due to the pressure differences that occur on each side of the roof structure. A positive pressure occurs on the windward side and suction on the leeward side, as a result of the air stream being deflected by the roof structure. If the wind blows directly against one side of the roof structure, at 90° to the line of the ridge 206, e.g. in direction W2 in Figure 4, the rotor remains in the forward position. The ambient air stream strikes the front of the building and the roof structure, and is deflected and receives maximum acceleration in velocity as it travels along the inclined roof surface 204. It enters wind passages 112H and 112G and is accelerated therein due to the internal taper of the passages and is directed to the rotor assembly 130 (with less deflection by baffles 186 than if the wind direction was at 45°). Furthermore, the pressure differences occurring across each side of the roof structure are at a maximum for this wind direction, providing maximum assistance to air flow through the assembly 100 and maximum effect on the blades 132 and thereby optimum power generation.

It should be understood that, amongst other possible modifications, the assembly 100 can be fabricated from discrete elements rather than modular units. The rotor may be rotatable a full 360° about the vertical axis or may be fixed in the forward position. A simplified mechanism utilising a tailfin (not shown) could be employed for turning the rotor automatically to face the wind direction. The tailfin may be mounted above the cover 188 and fixedly attached to the cage 180 via a shaft passing through the cover. For example, the cage could be modified to fully surround or otherwise extend above the rotor, and the shaft could be attached to an upper portion of the cage. This mechanism could replace the motor driven gear mechanism, the gear wheel 182 being replaced by an undriven wheel 190.

Inlet passages may be provided in the bridge body 120, so that the inlets to the assembly define a complete circumferential array.

Another embodiment of a wind power assembly is indicated generally at 300 in Figures 12 and 13. The general construction of the wind bodies and passages etc is similar to the assembly 100, and therefore corresponding reference numerals will be used accordingly, albeit prefixed with the numeral 3.

However, in this embodiment, the rotor assembly is replaced by a vertical axis rotor 400, consisting of a plurality of blades 410 from a circular hub 412 and having a nose cone 416. The rotor 400 is mounted in an upwardly directed rotor housing 420, which forms an exit passage for the assembly, in the manner of a chimney. The rotor housing 420 narrows to provide a constricted Venturi throat section of minimum diameter, which coincides in height with the rotor 400, and then extends upwardly and outwardly to form an exit of greater diameter than the throat.

The rotor 400 rotates on a vertical shaft 414 that drives and is supported by an electrical generator 418. A baffle arrangement 422 supports the electrical generator and rotor and is provided beneath the rotor 400 for diverting air from the wind channelling bodies 310 up into the rotor 400. The baffle arrangement 422 is configured to avoid air escaping directly through the assembly without passing through the rotor 400 and instead deflects an incoming air steam travelling at an inclined angle, upwardly into the housing 420 and around the outside of the electrical generator 418.

Stationary blades 402 are supported on the generator 418 immediately beneath the rotor 400, and are orientated oppositely in direction to the rotor blades 410 in order to direct the maximum air flow tangentially against the moving blades 410. The rotor housing 420 is mounted and supported on a cover plate 430 that fully encloses the cavity defined by the bridge body 320 between the wind channelling bodies 310.

Incident air stream is captured and accelerated by at least two of the converging passages 312 in the wind channelling bodies 310, and enters the central cavity at increased velocity. Hinged blinds 440 may be installed in the exit end of each wind passage 312, as shown in Figure 14, to ensure that all air entering the assembly 300 passes through the rotor 400 and does not escape through opposing passages. The blinds 440 are manufactured preferably from a lightweight material to minimise the resistance to airflow.

Air stream entering the central cavity is deflected upwardly by the baffle arrangement 422 and enters the rotor housing 420. An increase in velocity is then experienced due to the constricted Venturi passage of the rotor housing 420, reaching maximum velocity as it passes through the rotor 400. The air stream exits then through the upper end of the rotor housing 420, which is flared upwardly and outwardly to give an increased exit area, and reduced air velocity.

Ambient wind passing over the upper end of the rotor housing 420, either horizontally or at an upwardly inclined angle, may provide a 'chimney effect' in which the air stream exiting the assembly 300 is accelerated in velocity. This may produce an increase in airflow through the assembly 300 and therefore increased power output.

A still further embodiment is illustrated in Figures 15 and 16, indicated generally at 500. The general construction of the wind bodies and passages etc is similar to the assemblies 100 and 300, and therefore corresponding reference numerals will be used accordingly, albeit prefixed with the numeral 5.

In this embodiment, a rotor 600 is provided in a rotor housing 620 rotatably supported over the cavity defined by the bridge body 520 between wind channelling bodies 510. Again, an array of baffles 630 is provided for directing air stream up into the rotor 600, so that the air stream may only exit the assembly 500 via the rotor housing 620.

The rotor housing 620 defines a passage 622 which curves smoothly through 90°. The passage 622 converges from a semicircular inlet 624 to a constricted Venturi throat section 626, approximately halfway along its length, before diverging to a larger diameter outlet 628.

The rotor 600 is positioned at the narrowest point of the throat section 626 and is mounted at an inclined angle. The rotor 600 is fixedly supported on a rotatable shaft 614 which drives an electrical generator 618. The electrical generator is supported in the rotor housing 620 by three equi-spaced air foil shaped struts 632.

The rotor housing 620 is supported on a circular bearing assembly which allows the rotor housing 620 to rotate about a central vertical axis through 360°. Depending on wind direction the rotor housing 620 can be turned to one of four positions, 90° apart, by means of a mechanical drive system (not shown) that detects the wind direction and turns the rotor housing, such that the air stream exits the outlet 628 in the general direction of the prevailing wind. The flow of wind past the rotor housing and over the apex of the assembly and roof structure provides a reduced pressure on the leeward side, which assists the flow of air through the assembly, thereby increasing the power generated.

It will be readily apparent that one or more of the features of the wind channelling bodies or wind passages described in relation to Figures 1 to 11 can be incorporated into any of the embodiments shown in Figures 12 to 16. Whilst the later described embodiments are preferably modular in construction, they may be assembled on site from individual components, for example using individually fabricated wind passages.

It should also be understood that any of the wind assemblies described above can be built into a pitched structure, rather than supported directly on an existing pitched surface. An example is shown in Figure 17, wherein the bridge body 120 has been built into a roof structure 200, in this embodiment to sit over the apex of the roof. Installation of the assembly can be as part of the initial construction process of the pitched structure or as a retrofit whereby one or more portions of an existing structure can be removed to accommodate the assembly. It is envisaged that, at least for roof structures, the wind channelling bodies can be supported on the supporting framework of the roof or some other substructure (e.g. a base board 194 attached to the framework of the roof), rather than directly onto the outer roof surface (tiles), although additional reinforcement may be required. This mode of mounting necessitates the use of a wider bridge body, to straddle the roof apex.

The bridge body may be supported as before on either side by the wind channelling bodies 110, 310, 510 to provide a clearance gap between the bridge body and the roof structure. Alternatively, the base wall 122, 322, 522 of the bridge body may be supported by the underlying roof structure.

In either case a damping material may be placed between the base wall and the roof structure to reduce the transmission of noise and vibration. By effectively lowering the assembly into the pitched structure, it is possible to accommodate larger rotor diameters without a proportional increase in the projection of the assembly from the pitched structure, thereby minimising visual impact whilst increasing the power generation capacity of the assembly.

An additional benefit is that the rotor is lowered into the accelerated layer of deflected wind travelling along the roof surface, as discussed in more detail later. Scale model tests have shown that lowering the assembly into a recess or cut out in the pitched structure may provide significant increases in the electrical power generated.

Another embodiment of a wind power assembly is indicated generally at 700 in Figure 18.

In this embodiment, the assembly 700 includes a rotor assembly 730 mounted within a recess or cut-out prepared in the roof structure. The recess may be prepared in the manner described above, for example.

The rotor assembly 730 consists of a propellor type rotor having five blades 732 fixedly mounted on a central nose cone or hub 734. Any number of blades of any suitable design could be used. The rotor 736 is connected to and drives an electrical generator 770 via a common shaft 738. The rotor assembly 730 is supported by a vertical stanchion 780, which is rotatably supported about a vertical axis by a bearing assembly 792 at the base of the stanchion 780. The stanchion 780 is configured to be rotatable through at least 180° so that the rotor assembly 730 may be turned to face the oncoming air stream from either direction. The bearing 792 may be driven by any means known to the art. For example the bearing may have an externally geared ring (not shown) that could be driven by one or more simple DC gear motors.

As can be seen, the stanchion 780 and rotor assembly 730 are arranged approximately midway along, and enclosed within, a venturi shaped passageway 796 formed by the inner walls of a ridge body 720 and the cover 788 for the bridge body 720. A small wind direction sensor (not shown) is mounted in the venturi passageway 796 to monitor the airstream direction, whereby the assembly 790 can be rotated as required, e.g. using the gear motors, to face the oncoming air-stream. In extreme wind conditions the plane of the rotor can be aligned with the wind stream direction i.e. the rotor turned through 90° as viewed in Figure 18, to protect the turbine from damage. Alternatively a tailfin (not shown), incorporating a furling mechanism, well known to the art, may be provided to the rear of the rotor assembly 730, to automatically turn the rotor to face the airstream in normal wind conditions, and to align the rotor with the air stream in extreme wind conditions. In such an arrangement, the bearing assembly 792 does not need to be driven, and the bearing could be incorporated at any position along the stanchion, for example at the top of the stanchion.

This embodiment 700 uses wind channelling bodies 710 of greatly simplified form, essentially open channels defined by simple baffles 716 rigidly supported by the base wall 714, and at the rear of the upper edge by a supporting strut 742.

Maximum power output is achieved for wind directions from the front or back of the pitched roof structure at 90° to the ridge line 206. Incident wind and wind deflected by the roof structure 200 and the baffles 716 enters the venturi passage 796 and accelerates in velocity as it passes along the converging passage, reaching a maximum velocity at the rotor position, corresponding to the position of minimum cross sectional area. Pressure differences on either side of the assembly 700, e.g. created by airflow over the pitched roof, may further increase the velocity of air through the venturi channel 796, resulting in increased power output. For wind directions at an angle of approximately 45° to the roof ridge 206 (Wl in Fig 4) the effective capture area of the venturi passage 796 is reduced, but some wind is deflected into the venturi by the baffles 716.

It will be understood that little or no power is generated by wind directions aligned with the ridge line of the roof. Nevertheless, the assembly 700 has the advantage of simplified construction and a relatively large wind capture area for other wind directions. Further simplification may be achieved by using a fixed stanchion and rotor with non-aerodynamic blades that may be effected by wind flow from either side of the rotor.

As in previous embodiments, the ridge body 720 may be supported on either side by the base walls 714, to provide clearance between the underneath of the ridge body 720 and the roof structure. Alternatively the underneath of the ridge body 720 may be supported by the roof structure.

Another embodiment of a wind power assembly is indicated generally at 800 in Figures 19 to 22. The rotor assembly in Figures 19-22 is similar in many respects to the rotor assembly of Figure 18, and so will not be described in detail. Corresponding reference numerals will be used accordingly, albeit prefixed with the numeral 8.

The plane of the rotor blades 832 in the assembly 800 is arranged in an inclined manner, e.g. as shown in Figure 20, so as to generally face the direction of wind travelling up the pitch of the roof. Such an arrangement has been shown to increase the overall power output from the assembly 800, since the wind will tend to travel up along the pitch of the roof and wind capture or power output tends to be optimised when the wind approaches the rotor at an angle generally perpendicular to the plane of the rotor.

In this embodiment, the stanchion 880 in Figures 19 and 20 is arranged at an incline of approximately 10°. In alternative embodiments, the plane of the rotor can be arranged from 0° to generally perpendicular to the pitch, or more preferably the upper surface, of the roof. A minimum angle of 5° may be preferred.

The inclination of the rotor plane can be achieved with the stanchion 880 in a substantially vertical orientation but with the electrical generator and rotor assembly 830 supported at an angle of inclination towards the pitch of the roof surface 202, or via a combination of inclined stanchion 880 and inclined rotor (relative to the stanchion 880), for example. In this embodiment, the stanchion 880 is fixedly mounted to a bearing assembly 892, which allows 360° rotation about a generally vertical axis. The bearing assembly 892 is then fixedly mounted onto a support plate 896 and a support frame assembly 840.

A mechanism may be included to automatically change the angle of inclination of the stanchion or the plane of the rotor as the assembly rotates. The plane of the rotor could be vertical for wind directions along the roof ridge and inclined from the vertical for other wind directions, e.g. for wind directions of between 30° and 90° to the roof ridge.

As can be seen, the stanchion 880 and rotor assembly 830 are arranged in a recessed portion of the roof structure, more particularly a cut-out across the ridge 206 of the roof structure 200.

Figures 21 and 22 show an example method of mounting the wind turbine assembly 890 and bearing assembly 892 in a roof cut-out 860.

Figure 21 shows a typical timber roof structure after modification to form the cut-out 860. A section of the ridge board 862 is removed and a number of the rafters 864 are cut horizontally at the required height. Horizontal cross members 866 are added, as shown, and additional cross members 868 may be fixed to the outlying rafters at each end of the cut-out. Longitudinal timbers 858 may be added to provide further strengthening. Other reinforcement may be required, depending on local building regulations, for example.

A base board 842 and two end boards 844 are fixedly attached to create a cut-out enclosure, providing additional strength and rigidity to the structure, and providing a degree of sound insulation between the cut-out 860 and the roof space. The cut-out ends may be inclined from vertical, if required (inwardly or outwardly). A layer of sound insulating material 848 and 846 respectively, is preferably applied to the upper surface of the base board 842 and inner surfaces of the end boards 844, as shown in Figures 20 and 22, and further insulation, in the form of fibreglass or foam or any other suitable material, may be incorporated as required, e.g. between the horizontal cross members.

A support frame assembly 840 is mounted in the cut-out 860 and supported on a number of anti-vibration pads 850 which pass through the insulating board 848 and are supported on the baseboard 842. This provides a clearance gap between the majority of the framework and the insulating material 848.

Figure 22a shows that the frame may have some means of adjustment 852, to accommodate variations in cut-out size.

The framework is preferably bolted or fixed by other means through the anti-vibration pads 850 to the supporting base board 842 or more preferably the cross members 866, and may also be fixed to the outlying rafters, as shown in Figure 22a. The purpose of the support frame assembly 840 and support plate 896 (see Figure 22) is to spread the weight and forces exerted by the turbine assembly 890 and bearing assembly 892 evenly over the supporting roof structure.

The insulating material 848, anti-vibration pads 850 and presence of an air gap between the majority of the support frame assembly 840 and the insulating material 848, are intended to eliminate or greatly reduce the transmission of noise and vibration to the roof structure 200.

Figures 20 and 22 show the support frame assembly 840 fabricated using square section tube, but rod or tubing of any cross sectional shape and any material, fabricated by any method, could be used. The important requirements of the framework are a high strength to weight ratio, good fatigue resistance and good corrosion resistance.

The bearing assembly 892 or 'yaw bearing', at the base of the stanchion 880, should be of sufficiently large diameter to withstand the forces transferred to it through the stanchion 880 in all wind conditions. This bearing 892 may be freely rotating or driven by any means known to the art. In the preferred embodiment the bearing 892 has an externally geared ring (not shown in the Figures), which could be driven by one or more simple DC gear motors, mounted on the support plate 896. In most cases the low mechanical resistance of the bearing assembly 892 would allow the turbine assembly 890 to 'self direct', keeping the rotor facing the wind, without the use of a tailfin i.e. free-yawing. A small wind direction sensor 898 can be used mounted adjacent the stanchion 880 (see Figures 19) to monitor any misalignment of the rotor. The direction of the rotor can then be corrected at intervals by active yawing.

In extreme wind conditions, as measured by the electrical output of the rotor assembly 830, or alternatively by an anemometer mounted adjacent the rotor assembly 830, the rotor 836 could be turned through 90° to the direction of the wind, preventing damage to the turbine and minimising the forces transmitted to the roof structure. Alternatively the rotor 836 may be turned to an intermediate angle to limit the maximum power output produced, whilst reducing the forces on the rotor and supporting structure. This would give a significant advantage over many existing roof mounted wind turbines that do not generate any electricity at higher wind speeds.

Figure 22 shows the roofing materials i.e. roof felt 882, wooden laths 884, and roof tiles 856, reinstalled up to the edges of the cut-out 860 to prevent rain etc entering the roof space. The entire roof cut-out 860, support frame assembly 840 and bearing assembly 892 are enclosed and protected from the environment by a ridgebody cover, shown generally at 820 in Figures 19 and 20. The broken line 888 shows the relative position of the ridgebody cover 820 with respect to the cut-out 860. A circular cover 894, attached to the bottom of the stanchion 880, above the bearing assembly 892 (Figures 19 and 20), allows the wind turbine assembly 890 to rotate freely in a circular cut-out in the ridgebody cover 820, and may be designed to prevent weather ingress. The base of the ridgebody cover 826, best viewed in Figure 20, has a curved upper surface and is shaped to encourage the airflow to follow the curved contours of the cover towards the rotor 836. In addition this discourages rain and snow from collecting on, and entering, the assembly 800. At each end of the cut-out 860 the ridgebody cover 828 is shaped to cover the roof tiles 856 and ridge tiles 886, again with sufficient overlap to prevent weather ingress. As an alternative, the cover may pass beneath the ridge tiles, roof tiles and supporting lathes 884 at each end of the cut out. The gap between the tiles and the cover may then be filled with a suitable material, e.g. cement, foam etc to exclude weather effects.

The ends of the ridge body cover 828 are preferably rounded to provide a streamlined shape such that for wind directions along the ridge line the wind is able to follow the profile of the ridgebody cover and flow into the bottom part of the rotors swept area. However, the cover may be of any shape within the roof cut out.

Different buildings will have different roof geometry and roof tile configurations and in order to accommodate these differences the ridgebody cover 820 could be manufactured as an assembly of several different overlapping sections.

A front and rear ridgebody section 814, which may be separate from the main ridgebody cover 820, is used to overlap the roof tiles at the lower extremes of the cut-out. Various materials, e.g. foam, could be used to provide a seal between the ridgebody cover and the tiled surface. The ridgebody cover 820 would be fabricated from thin sheet and any suitable material, for example aluminium, plastic or fibre glass etc. can be used.

The outer surface of the ridgebody cover may be used to mount solar cells, for generating additional power from sunlight. The hollow cavity between the support plate 896 and ridgebody cover 820 may also be used to house any electrical equipment associated with the assembly 800. A manual means of driving the bearing 892 via a gear, turned by a handle in the roof space (not shown), would allow the wind turbine to be turned out of the wind manually in extreme wind conditions, in the event of a mechanical or electrical breakdown of the automatic yaw systems.

The above described construction and method of mounting is provided by way of example and other methods of mounting may be applicable. Figures 23 and 24 show an alternative embodiment 900 (with corresponding reference numerals used, albeit prefixed with the numeral 9—), in which the yaw bearing 992 is mounted at the top of a simple post or stanchion 980. In this case the post 980 is fixedly mounted to the support plate 996, and passes through the base of the ridgebody cover 926. This has the advantage that the ridgebody cover is sealed around the base of the post and there are no moving mechanical parts within the ridgebody cover cavity. A tailfin 972 may be provided to turn the rotor to face the wind. This method of mounting could be used to accommodate most currently available designs of propellor type roof mounted wind turbines with little adaptation, incorporating a wide variety of yaw and furling mechanisms to protect the turbine in high wind conditions.

As mentioned previously, it has been found that wind capture or power output from a horizontal axis rotor on a roof is increased if the rotor is lowered into a recess or channel in the roof, e.g. in a recess or channel formed across the apex of the roof, so as to lower an increased proportion of the rotor into the accelerated layer of wind travelling along the roof surface.

This is contrary to conventional thinking, in which such horizontal axis rotors are usually mounted as high as possible above the roof, via a pole or stanchion extending up from the gable end of the roof, for example. However, such arrangements usually fail to benefit from the accelerated layer or are subjected to detrimental wind shear caused by the accelerated layer hitting the lower end of the rotor at an inclined angle and ambient airflow hitting the upper end of the rotor horizontally.

It may be preferred to use a rotor diameter which is within or does not greatly exceed the effective thickness of the accelerated layer of wind referred to above. Rotor diameters of between 0.5 metres and 2.2 metres are envisaged for domestic properties of average size and conventional pitched roof geometry. However, proportionately larger rotors may be useful for larger buildings of suitable structure and roof geometry. An additional advantage of lowering the rotor is a reduced visual impact. Also, by mounting the rotor in a recess, the forces transferred by the rotor may be distributed over a larger area than conventional 'gable end' or brick work mounted arrangements.

In preferred embodiments, the cut out depth 'd', e.g. as shown in Figure 20 (or alternatively measured as the distance from the top of the cut out to the lowest point of the rotor) is between 0.05 and 0.75 times the diameter of the rotor, so that at least a lower portion of the rotor is within the cut out and an upper portion of the rotor extends above the cut out, although it may be preferred to have the entire rotor diameter below the upper level of the cut out.

The channel in which the rotor is mounted is preferably U shaped, i.e. having side walls and an inter linking base portion, and is more preferably formed as a recess across the apex of the roof. The side walls of the channel may taper outwardly (or inwardly) as desired, and may be of different height from one another. Indeed, it may be preferred to omit one side wall, so that the channel is more generally L-shaped, to enable mounting at the gable end of a pitched roof structure, e.g. as shown in Figure 25.

The proposed method of mounting may also be applied to other suitable wind turbine designs. For example the propeller type turbine could be replaced by a Darrieus type Vertical-Axis wind turbine (VAWT), sometimes referred to as an "Eggbeater" turbine. In this case the electrical generator would be mounted beneath the ridgebody cover 820.

Any combination of the features from the individual embodiments described above can be readily combined, as required.

Where possible, the configuration of an assembly in accordance with the invention should be optimised for maximum wind capture at minimum acceptable visual impact. This may include reductions in height and effective wind capture area, in particular for the circular type assemblies shown in Figures 1 to 16. The rotors shown in Figures 18 and 19, for example, are commonly referred to as 'up-wind' turbines, wherein the rotor is arranged in front of the generator and stanchion so as to face the wind, and preferably to face down the incline of the pitched structure. However, it may be preferred to use 'down-wind' turbines wherein the rotor is behind the stanchion and faces away from the direction of wind, and preferably angled so as to face up the incline of the roof.

Claims

1. A pitched structure incorporating a wind power generator, the pitched structure having a channel formed as a recess across the apex of the pitched structure and through which an airflow is intended to pass, and wherein the wind power generator comprises a bladed, propellor type horizontal axis rotor mounted in said channel for generating power in response to a flow of air passing into said channel.

2. A pitched structure according to claim 1 wherein at least a portion of the rotor extends below said apex and wherein at least a portion of the rotor extends above said apex.

3. A pitched structure according to claim 1 or claim 2 wherein the rotor blades define a rotor plane, and wherein the rotor plane is arranged at an angle from vertical.

4. A pitched structure according to claim 3 wherein the angle of inclination of the rotor plane is in the region of 5 degrees to 30 degrees from vertical.

5. A pitched structure according to any preceding claim wherein the rotor blades are plane or of aerodynamic profile.

6. A pitched structure according to any preceding claim wherein the channel has one or more side walls having a convex profile in plan view.

7. A pitched structure according to any preceding claim wherein the channel includes a base having a convex upper surface.

8. A pitched structure according to any preceding claim wherein the channel is substantially U-shaped or L-shaped.

9. A pitched structure according to any preceding claim wherein the rotor is movable about a generally vertical axis to face a prevailing wind direction.

10. A pitched structure according to any preceding claim wherein the channel is a retro-fit assembly for said pitched structure.

1 1. A wind power assembly comprising a channel across which an airflow is intended to pass, and a rotor mounted in said channel for generating power in response to a flow of air passing across said channel.

12. A wind power assembly according to claim 11 wherein the rotor is a horizontal axis rotor, the rotor having blades which define a rotor plane, and wherein the rotor plane is arranged at a minimum angle of 5 degrees to the vertical.

13. A wind power assembly according to claim 12 wherein the rotor is mounted on an upright support which is angled away from vertical.

14. A wind power assembly according to any of claims 11 to 13 wherein the channel defines an upper limit and wherein at least a portion of the rotor extends below said limit.

15. A wind power assembly according to claim 14 wherein at least a portion of the rotor extends above said limit.

16. A wind power assembly according to any of claims 11 to 15 wherein the channel is substantially U-shaped, V-shaped or L-shaped.

17. A wind power assembly according to any of claims 11 to 16 wherein the channel has side walls having a curved profile in plan view.

18. A wind power assembly according to any of claims 11 to 17 wherein the channel includes a base having a curved upper surface.

19. A wind power assembly according to any of claims 11 to 18 wherein the rotor is movable about a generally vertical axis to face a prevailing wind direction.

20. A building incorporating a wind power assembly or pitched structure according to any of claims 1 to 19.

21. A wind power assembly for mounting across the apex of a pitched structure, the assembly including a rotor for generating a power output, and guide passages for directing air towards the rotor to cause rotation thereof, wherein the rotor is arranged between said guide passages and defines a generally horizontal datum, and wherein each guide passage defines a flow path inclined to said horizontal datum.

22. A wind power assembly according to claim 21 wherein the rotor is a horizontal axis rotor which defines said horizontal datum.

23. A wind power assembly according to claim 22, wherein the rotor is movable about a vertical axis.

24. A wind power assembly according to any of claims 21 to 23, comprising a modular construction for mounting at the apex of the structure, the modular construction including opposing channel bodies intended to extend down a respective side of the pitched structure, wherein the rotor is intended for mounting between said channel bodies.

25. A wind power assembly according to claim 24, further comprising a central body for mounting across the apex of the structure, a channel body arranged on either side of the central body, and wherein the rotor is enclosed within said central body.

26. A roof construction having an inclined roof surface, said roof construction having a wind power assembly including a rotor and a wind passage for directing air towards said rotor, wherein said wind passage defines an inclined air stream pathway which extends down said inclined roof surface.

27. A roof construction according to claim 26, wherein the roof construction defines opposing inclined surfaces on either side of an apex.

28. A roof construction according to claim 27, wherein the rotor is arranged at the apex of said roof construction.

29 A roof construction according to claim 28, wherein the wind power assembly includes opposing wind passages extending down either inclined surface.

30. A roof construction according to claim 29, wherein the opposing passages consist of conduits which are divergent away from the rotor.

31. A roof construction according to any of claims 26 to 30, wherein damping means is provided on the underside of the assembly for reducing the transmission of vibration, noise and/or sound to a supporting portion of the roof construction.

32. A wind power assembly or roof construction according to any of claims 21 to

31, wherein the wind power assembly includes a radial array of wind passages.

33. A wind power assembly or roof construction according to any of claims 21 to

32, wherein baffles are included for directing an air stream into said rotor from said passages.

34. A wind power assembly or roof construction according to any of claims 21 to

33, wherein the or each passage includes side walls which are extendable so as to increase the effective zone of wind capture of the assembly.

35. A wind power assembly or roof construction according to claim 34, wherein the or each passage also includes a moveable closure member for selectively reducing or preventing the flow of air along said passage to said rotor, and wherein the extendable side walls act to open and close said closure member.

36. A method of modifying a roof structure to incorporate a wind power assembly, comprising the steps of removing a section of roof structure so as to form a recess across the apex of the roof structure and mounting a wind power assembly according to any of claims 1 to 19, 21 to 25 or claims 32 to 35 at said recess.

37. A pitched structure, wind power assembly, roof construction or method of assembling the same, substantially as described herein with reference to the accompany Figures.