Patent Description:
A conventional horizontal-axis wind turbine known in the art typically comprises three blades. The wind turbine converts the kinetic energy of the wind into mechanical motion according to the principle of aerodynamic lift. In operation, the blades rotate and drive a generator which converts the mechanical motion into electricity.

Whilst wind turbines are widely used in the energy industry to offer a source of renewable energy, there are numerous disadvantages. Wind turbines can only operate within a narrow wind speed window. For example, if the wind speed is too high there is a risk of damaging the wind turbines. Conversely if the wind speed is too low, then there may not be enough aerodynamic lift to rotate the blades.

Commercial wind farms typically comprise large wind turbines which can be over <NUM> tall. Whilst large wind turbines are more efficient than smaller scale micro wind turbines, the large wind turbines typically dominate the surrounding landscape and have a negative aesthetic impact on the environment. There are further negative environmental consequences as wind turbines can affect the surrounding wildlife. For example, the blades of the wind turbines can kill birds.

In addition, such large wind turbines are not suitable to be located in urban landscapes, by motorways and especially not near airports as they tend to produce a significant turbulent flow in the wake of the blades.

Examples of energy harvesting devices known in the art are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

It is an object of an aspect of the present invention to provide an energy harvesting device that obviates or at least mitigates one or more of the aforesaid disadvantages of the energy harvesting devices known in the art.

According to a first aspect of the present invention there is provided an energy harvesting device as provided by claim <NUM>. Optional features are provided by dependent claims <NUM> to <NUM>.

According to a second aspect of the present invention there is provided an energy harvesting system as provided by claim <NUM>.

Embodiments of the second aspect of the invention may comprise features to implement the preferred or optional features of the first aspect of the invention or vice versa.

According to a third aspect of the present invention there is provided a method of manufacturing an energy harvesting device as provided by claim <NUM>. Optional features are provided by claim <NUM>.

Embodiments of the third aspect of the invention may comprise features to implement the preferred or optional features of the first and or second aspects of the invention or vice versa.

In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of embodiments of the invention.

An explanation of the present invention will now be described with reference to <FIG>.

<FIG> and <FIG> depict an energy harvesting device 1a. More specifically, the energy harvesting device 1a is suitable for harvesting energy from a fluid flow such as wind, tidal flows or even a river flow. The energy harvesting device 1a comprises a first surface 2a and an opposing second surface 3a. The first and second surfaces 2a, 3a are both perpendicular to and centred about a central axis <NUM>.

The energy harvesting device 1a further comprises a generator housing 5a centred about the central axis <NUM>. The generator housing 5a comprises an internal portion <NUM> and a cone-like portion <NUM>, as can clearly be seen in <FIG>. The internal portion <NUM> of the generator housing <NUM> extends between the first and second surfaces 2a, 3a and has a substantially circular cross-sectional shape. It will be appreciated the internal portion <NUM> of the generator housing <NUM> may have any suitable cross-sectional shape which can vary between the first and second surfaces 2a, 3a. The cone-like portion <NUM> of the generator housing 5a is a continuation of the internal portion <NUM> that protrudes from the first surface 2a and tapers towards the central axis <NUM>.

The energy harvesting device 1a further comprises ducts 8a located circumferentially about the generator housing 5a, as clearly shown by <FIG> and <FIG>. The ducts 8a take the form of passageways between the first and second surfaces 2a, 3a suitable for channelling a fluid flow <NUM> through the energy harvesting device 1a. It will be appreciated the fluid flow <NUM> could take the form of a gas flow or a liquid flow.

The cone-like portion <NUM> of the generator housing 5a diverts the fluid flow <NUM> towards the ducts 8a. It has been found preferable for efficient operation for the energy harvesting device 1a as depicted in <FIG> and <FIG> to comprise no more than eighteen ducts 8a located about the generator housing 5a.

Each duct 8a comprises an inlet opening <NUM> on the first surface 2a and a corresponding outlet opening <NUM> on the second surface 3a. As can be seen in <FIG> and <FIG>, the ducts <NUM> comprise a substantially elliptical cross-sectional shape. The ducts 8a are orientated such that the semi-major axis of the elliptical cross-sectional shape extends radially from the central axis <NUM>. It will be appreciated the ducts 8a may have any suitable cross-sectional shape.

As shown in <FIG> and <FIG>, each duct 8a has a different relative size according to the location of the duct 8a on the first surface 2a. As an alternative, it will be appreciated each duct 8a may all be uniform in size.

<FIG> and <FIG> show that the cross-sectional shape of the ducts 8a changes in the direction of the central axis <NUM>. In other words, the cross-sectional shape changes between the first and second surfaces 2a, 3a. This variation of the cross-sectional shape of the ducts 8a can be configured to modify the velocity of the fluid flow <NUM> through the energy harvesting device 1a. As an alternative, the ducts 8a may comprise a uniform cross-sectional shape.

<FIG> and <FIG> show that the ducts 8a comprise optional external portions <NUM> protruding from the second surface <NUM>. The external portions <NUM> are configured to divert the fluid flow <NUM> exiting the energy harvesting device 1a from the outlet openings <NUM>.

The energy harvesting device 1a further comprises one or more foils <NUM>, located within each duct 8a, as shown in <FIG> and <FIG>. More specifically, the one or more foils <NUM> take the form of one or more aerofoils or one or more hydrofoils depending if the fluid flow <NUM> is a gas flow or a liquid flow.

<FIG> depicts a foil <NUM> and defines several terms used to describe the shape of the foil <NUM>. The foil <NUM> comprises a leading edge <NUM> and a trailing edge <NUM>. The leading edge <NUM>, or foremost edge, is the first foil surface to meet an incident fluid flow <NUM>. As such, the leading edge <NUM> separates the incident fluid flow <NUM>. The trailing edge <NUM>, or rearmost edge, is where the fluid flow <NUM> separated by the leading edge <NUM> meets.

The foil <NUM> also comprises a chord <NUM> and span <NUM>. The chord <NUM> is the distance between the leading and trailing edges <NUM>, <NUM>. Whereas the span <NUM> is the distance between a first side <NUM> and a second side <NUM> of the foil <NUM>. In addition, a chord line <NUM> is defined as an imaginary straight line connecting the leading and trailing edge <NUM>, <NUM>.

The foil <NUM> further comprises an upper surface <NUM> and a lower surface <NUM>. The relative curvature of the upper and lower surfaces <NUM>, <NUM> is parameterised by a camber line <NUM> which is a line equidistant between the upper and lower surfaces <NUM>, <NUM> extending across the chord direction of the foil <NUM>. The foil <NUM> comprises a uniform cross section across the span <NUM>.

<FIG> depicts the foil <NUM> mounted within a duct 8a. The foil <NUM> is orientated such that the leading edge <NUM> is located towards the inlet opening <NUM> and the trailing edge <NUM> is located towards the outlet opening <NUM>. In other words, the chord direction of the foil <NUM> is substantially parallel to the central axis <NUM>.

In operation, a fluid flow enters the duct <NUM> through the inlet opening <NUM>, flows past the foil <NUM> inducing aerodynamic or hydrodynamic forces and then exits the duct <NUM> through the outlet opening <NUM>. The foil <NUM> exhibits movement, vibrations and or specifically flutter vibrations, and it is the kinetic energy from these vibrations that the energy harvesting device 1a captures, focuses, transmits, converges and or converts into electrical energy.

When aerodynamic or hydrodynamic forces deflect a foil <NUM> a restoring force acts to return the foil <NUM> to its original shape due to the elasticity of the foil <NUM> structure. Flutter is a dynamic instability caused by positive feedback between the fluid dynamic forces and the restoring force of the foil <NUM>. Whilst foils <NUM> known in the art are typically designed to avoid flutter, these vibrations are desirable in the energy harvesting device 1a as it is mechanical vibrational energy the present invention converts into useful electrical energy.

Whilst the foil <NUM> of <FIG> can exhibit flutter vibrations, it is possible and preferable to enhance these flutter vibrations by:.

<FIG> depicts a modified foil 25a comprising a thickness variation in the span direction. The modified foil 25a comprises both positive and negative cambered cross sections <NUM>, <NUM>. A positive cambered cross section <NUM> results in a lift force <NUM> and is defined by the camber line <NUM> being located between the upper surface <NUM> and chord line <NUM>, as depicted in <FIG>. A negative cambered cross section <NUM> results in a drag force <NUM> and is defined by the camber line <NUM> being located between the lower surface <NUM> and the chord line <NUM>, as can be seen by <FIG>. The modified foil 25a exhibits counter interacting lift and drag forces <NUM>, <NUM> inducing vibrations and or specifically flutter vibrations. The modified foil 25a of <FIG> exhibits vibrations about an axis parallel to the chord direction.

As an additional or alternative feature, the modified foil 25a may further comprise weights <NUM> to induce and or amplify the vibrations. The modified foil 25a is hollow and comprises an internal structure <NUM>. The weights <NUM> depicted in <FIG> are non-uniformly distributed within the internal structure <NUM> of the foil 25a across the chord and span directions.

<FIG> depicts an alternative modified foil 25b comprising a thickness variation in the chord direction. This results in lift and drag forces <NUM>, <NUM> across the chord direction of the foil 25b inducing vibrations about an axis parallel to the span direction.

<FIG> depicts a further alternative modified foil 25c comprising thickness variations in both the span and chord direction resulting in a combination of vibrations about axes parallel to the chord and span directions.

As an additional or alternative feature, the energy harvesting device <NUM> comprises fins <NUM> as depicted in <FIG> protruding from the cone-like portion <NUM> of the generator housing 5a. The fins <NUM> comprise discontinuous vertices <NUM> disrupting the smooth laminar flow of the incident fluid flow <NUM> and creating turbulent fluid flow <NUM>.

As a further additional or alternative feature, the energy harvesting device 1a comprises flaps <NUM>. As depicted in <FIG>, the flaps <NUM> are located at the inlet opening <NUM> of the duct 8a and or, as depicted in <FIG>, the flaps <NUM> are located at the trailing edge of the foil <NUM>. The flaps <NUM> pivot to divert and disrupt the fluid flow <NUM> creating turbulent fluid flow <NUM>.

As another additional or alternative feature, the energy harvesting device 1a comprises a mesh <NUM> across the inlet opening <NUM> of the duct 8a as depicted in <FIG>. The mesh <NUM> is uniform yet it will be appreciated the mesh <NUM> could instead be non-uniform. The fluid flow <NUM> entering the inlet opening <NUM> of the duct 8a passes through the mesh <NUM>. The mesh <NUM> disrupts the fluid flow <NUM> to create turbulent fluid flow <NUM>. The mesh <NUM> has dual functionality in that it also acts as a barrier protecting the internal components of the energy harvesting device 1a. As such, it will be appreciated the energy harvesting device 1a may also comprises a mesh across the outlet opening <NUM> the duct 8a.

As an additional or alternative feature, the energy harvesting device 1a comprises flow restrictors <NUM> located within the duct 8a to narrow (or widen) the cross-sectional shape of the passageway, as depicted in <FIG>. The flow restrictors <NUM> act as a bottle neck increasing the velocity of the fluid flow <NUM>. The flow restrictors <NUM> disrupts the fluid flow <NUM> to create turbulent fluid flow <NUM>.

The energy harvesting device 1a further comprises a generator <NUM> employed to convert movement of the one or more foils <NUM>, <NUM>, in other words the vibrations, into electricity.

The generator <NUM> comprises a one or more vibrational apparatus in the form of one or more vibrational lenses <NUM> and an energy conversion means <NUM>. Each vibrational lens <NUM> captures, transmits, converges and or focuses vibrations from one or more foils <NUM>, 25a, 25b, 25c towards the energy conversion means <NUM> located within the generator housing <NUM>. The vibrational lens <NUM> has a dual purpose as is also a means for mounting each foil <NUM>, 25a, 25b, 25c within the plurality of ducts <NUM>.

The vibrational lens <NUM> may be of a type as described in the applicant's co-pending UK patent publication number <CIT> and UK patent application number <CIT>. As depicted in <FIG> and <FIG>, the vibrational lens <NUM> comprises at least two focusing members <NUM>. Each of the at least two focusing members <NUM> having a first end <NUM> for attachment to a vibrational source, in this case the foil <NUM>, 25a, 25b, 25c, and a second end <NUM>. The at least two focusing members <NUM> are arranged such that the separation between the focusing members <NUM> decreases from the first ends <NUM> towards the second ends <NUM>.

As can be seen in <FIG> and <FIG>, the first end <NUM> of each focusing member <NUM> extends within the foil <NUM>, 25a, 25b, 25c and is attached to the internal structure <NUM>. In addition or alternatively, the first end <NUM> of each focusing member <NUM> can be attached to the a surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the foil <NUM>, 25a, 25b, 25c such as the first side <NUM>.

The focusing members <NUM> depicted in <FIG> and <FIG> extend from the first side <NUM> of the foil <NUM>, 25a, 25b, 25c towards the central axis. As such, the foil 25a with a thickness variation in the span direction, would induce an oscillatory displacement, i.e. linear vibrations in focusing members <NUM>. Conversely, the foil 25a with a thickness variation in the chord direction, would induce an oscillatory twisting motion in the focusing members <NUM>. Furthermore, the foil 25c with both a thickness variation in the chord and span directions, would induce both a combined oscillatory displacement and twisting motion. The movement exhibited by the focusing members <NUM> is dependent on where the focusing members <NUM> are attached and the shape and structure of the foil <NUM>, 25a, 25b, 25c.

<FIG> and <FIG> show the focusing members <NUM> merge towards the second end <NUM>, pass through the generator housing 5a and extend within the generator housing 5a towards the central axis <NUM>. As an alternative, the focusing members <NUM> may pass through the generator housing 5a and then merge. The focusing members <NUM> pass through the generator housing 5a by means of a bearing <NUM> which facilitates the focusing members <NUM> transmitting the movement of the foil <NUM>, 25a, 25b, 25c within the generator housing <NUM>. The type of bearing <NUM> will depend on the type of movement, for example oscillatory displacement and or twisting, exhibited by the focusing members <NUM>.

The foils <NUM>, 25a, 25b, 25c are designed to oscillate and vibrate at a relatively low frequency between <NUM> to <NUM> and a relatively high amplitude equating to a displacement of the second end of the focusing members between <NUM> and <NUM>. Alternatively, the foils may vibrate at a medium frequency over <NUM> with a similar relatively high amplitude (<NUM> to <NUM>).

The energy conversion means <NUM> is located at the second end <NUM> of the vibrational lens <NUM>, within the generator housing 5a. As depicted in <FIG> and <FIG> the energy conversion means <NUM> takes the form of a magnet <NUM> attached to the second end <NUM> of the focusing members <NUM> and a coil <NUM> is located about the magnet <NUM>. The energy conversion means <NUM> operates on the principle of magnetic induction in that the movement of the magnet <NUM> relative to the coil <NUM> creates a changing magnetic flux inducing a current in the coil <NUM>. As can clearly by seen in <FIG> there are multiple sets of the magnet <NUM> and coil <NUM> located about the central axis <NUM>, where each set is independently generating electricity.

As an additional or alternative feature, the energy conversion means <NUM> may take the form of piezoelectric crystals.

<FIG> shows an energy harvesting system <NUM> comprising an array of the energy harvesting devices <NUM> stacked side-by-side and upon each other. As such, the energy harvesting system <NUM> may take the form of a wall, a fence, panels for a structure or building or even a component within a structure. The energy harvesting system <NUM> may be located in regions of high fluid flow <NUM>, and particularly high turbulent fluid flow <NUM>.

As an example, for a wind energy harvesting device <NUM> where the fluid of the fluid flow <NUM> is air, high turbulent air flow could be found near a motorway, an airport or even on a high-rise building.

As another example, for a liquid flow energy harvesting device <NUM> where the fluid of the fluid flow <NUM> is, for example water, high turbulent water flow could be found at a tidal barrier, a tidal estuary, a dam, river flood defences, bridge supports or even within water transport pipes. It will be appreciated that a liquid flow energy harvesting device <NUM> would be submerged under water.

<FIG> depicts an alternative energy harvesting device 1b which may comprise the same preferable and optional features as the energy harvesting device 1a depicted in <FIG>.

The energy harvesting device 1b of <FIG> comprising a duct 8b connecting the first surface 2b with a tangential third surface 47b of the energy harvesting device 1b. The third surface 47b is substantially parallel to the central axis <NUM> and connects the first and second surfaces 2b, 3b. The duct 8b comprises a bend <NUM> which diverts the fluid flow <NUM> originally parallel to the central axis <NUM> in a tangential direction to the central axis <NUM>. It will be appreciated that the energy harvesting device 1b may comprise both: ducts 8a connecting the first and second surfaces 2a, 3a as depicted in <FIG> and <FIG>; and ducts 8b connecting the first and third surfaces 2b, 47b as depicted in <FIG>. As an example, when the energy harvesting device 1b takes the form of panels on the side of a building, the ducts 8b divert away wind incident upon the building whilst also harvesting energy. As another example, when the energy harvesting device 1b takes the form of panels on a sea wall, the ducts 8b divert sea water incident upon the sea wall whilst also harvesting energy.

As an additional or alternative feature, the energy harvesting device 1b as depicted in <FIG> further comprises a layer of noise insulation <NUM> attached to the second surface 3b of the energy harvesting device 1b. When the energy harvesting device 1b takes the form of a panel suitable for use on a high-rise building, as well as the panel generating electricity, the noise insulation <NUM> would provide sound proofing for the building. The noise insulation <NUM> is particularly suited to the energy harvesting device 1b of <FIG> as the duct 8b is diverted away from the second surface 3b. Whereas the duct 8a of energy harvesting device 1a depicted in <FIG> would pass through the additional layer of noise insulation <NUM>.

<FIG> depicts an alternative energy harvesting device 1c which may comprise the same preferable and optional features as the energy harvesting devices 1a, 1b depicted in <FIG>.

The energy harvesting device 1c of <FIG> may comprise a lens <NUM> for focusing solar radiation <NUM>. This feature is particularly suited to a wind energy harvesting device, in other words, a device not submerged under water. The lens <NUM> may take the form of a conventional optical lens. The lens <NUM> is attached to the energy harvesting device 1c by means of a mounting bracket <NUM> and orientated to focus solar radiation <NUM> in the region of the outlet opening <NUM> of the duct 8c. Consequently, the fluid at the outlet opening <NUM> is hotter than the fluid at the inlet opening <NUM>. In other words, the lens <NUM> creates a thermal gradient between the inlet opening <NUM> and outlet opening <NUM> of the duct 8c. This thermal gradient induces a convection fluid flow, increasing the velocity and kinetic energy of the fluid flow through the duct 8c. The foils <NUM> located within the duct 8c may exhibit, for example, higher amplitude vibrations, and this increased vibrational energy can also be captured, transmitted, focused, converged and or converted into electrical energy by the energy harvesting device 1c. The lens <NUM> enhances the output of the energy harvesting device 1c as increases the amount of electricity generated. It will be appreciated that the energy harvesting device 1c may comprise multiple lenses <NUM> all orientated towards the outlet openings <NUM> of the ducts 8c.

<FIG> depicts an alternative energy harvesting device 1d which may comprise the same preferable and optional features as the energy harvesting devices 1a, 1b, 1c depicted in <FIG>.

As a further additional or alternative feature, the energy conversion means <NUM> may comprise a rotor <NUM>, or more specifically a whirligig-type rotor, connected by an elastic coil connector <NUM> between the second ends <NUM> of two focusing members <NUM> of two vibrational lenses <NUM>, see <FIG>. Each vibrational lens <NUM> is attached to a foil <NUM>. The oscillatory movement of the second ends <NUM> of two focusing members <NUM> stretches and compresses the elastic coil connector <NUM> which induces the rotor <NUM> to rotate. This rotatory motion is converted into electricity by a magnet and coil arrangement. The rotor can spin both clockwise and anticlockwise so a pole flipping magnetic generator is required such that electricity can be generated regardless of the rotation direction. In addition, or alternatively, a gear system (not shown) can be attached to the rotor <NUM>, which turns a secondary wheel or shaft. The gear system will rotate the secondary wheel or shaft irrespective to the direction of the rotor <NUM>.

<FIG> depicts an alternative energy harvesting device 1e which may comprise the same preferable and optional features as the energy harvesting devices 1a, 1b, 1c, 1d depicted in <FIG>.

<FIG> depicts a cylindrical energy harvesting device 1e comprising a curved surface <NUM>. In this device a duct 8e connects a first region <NUM> of the curved surface <NUM> to a second region <NUM> of the curved surface <NUM>. As can be seen in <FIG>, the ducts 8e have different orientations such that the ducts 8e each connect different regions of the curved surface <NUM>. As such, the energy harvesting device 1e can advantageously interact with fluid flows <NUM> from different directions.

<FIG> depicts an alternative energy harvesting device 1f which may comprise the same preferable and optional features as the energy harvesting devices 1a, 1b, 1c, 1d, 1e depicted in <FIG>.

The energy harvesting device 1f of <FIG> takes the form of a tree structure as comprises branch members <NUM>. Each branch member comprises a first surface <NUM>, a second surface <NUM> and ducts 8f connecting the first and second surfaces <NUM>, <NUM>. Each branch member <NUM> is connected to the generator housing 5f which takes the form of a central column as depicted in <FIG>. Advantageously, the branch members <NUM> may each have different orientations such that the energy harvesting device 1e can also interact with fluid flows <NUM> from different directions.

<FIG> depict an alternative energy harvesting device <NUM> in accordance with an embodiment of the present invention which may comprise the same preferable and optional features as the energy harvesting devices 1a, 1b, 1c, 1d, 1e, 1f depicted in <FIG>.

As can be seen in <FIG>, the energy harvesting device <NUM> has a substantially uniform hexagonal prism shape. The opposing first and second surfaces <NUM>, <NUM> of the energy harvesting device <NUM> take the form of the two hexagonal base surfaces of the hexagonal prism. As with previous devices, the first and second surfaces <NUM>, <NUM> are perpendicular to and centred about the central axis <NUM>.

The generator housing <NUM> depicted in <FIG> comprises a substantially hexagonal cross-sectional shape as opposed to a substantially circular cross-sectional shape as previously described in the context of <FIG>. Furthermore, the ducts <NUM> depicted in <FIG> comprise a substantially trapezium cross-sectional shape as opposed to an elliptical cross-section shape as previously described in the context of <FIG>.

A key difference between the energy harvesting system of <FIG> and the devices of <FIG>, is the configuration of the foils <NUM>, <NUM> and the generator <NUM>. More specifically, the vibrational apparatus of the generator <NUM> takes the form of a vibrational member <NUM> as opposed to a vibrational lens <NUM>. The vibrational member <NUM> comprises a first end <NUM> and a second end <NUM>. The first end <NUM> of the vibrational member <NUM> is attached to a first side <NUM> of a foil <NUM>, <NUM>. An energy conversion means <NUM> is located at the second end <NUM> of the vibrational member <NUM>. The vibrational member <NUM> extends from the foil <NUM>, passes through the generator housing 5a and extends within the generator housing 5a to the energy conversion means <NUM>. The vibrational member <NUM> passes through the generator housing 5a by means of a bearing <NUM>, located between the first and second ends <NUM>, <NUM> of the vibrational member <NUM>.

<FIG> depicts the motion, specifically four positions, exhibited by the vibrational member <NUM> and foil <NUM>, <NUM> of the energy harvesting device <NUM>. <FIG> defines an x, y and z axis to aid the description of this motion.

<FIG> depicts a first position <NUM>, where the vibrational member <NUM> is angled at -α relative to a central pivot position <NUM> of the vibrational member <NUM>. In the context of <FIG>, the central pivot position <NUM> of the vibrational member <NUM> is defined as when the vibrational member <NUM> is parallel to the z axis. Furthermore, in the first position <NUM>, the foil <NUM>, <NUM> is orientated such that the chord <NUM> of the foil <NUM>, <NUM> is angled at -β relative to a central rotation position <NUM> of the foil <NUM>, <NUM>. The central rotation position <NUM> of the foil <NUM>, <NUM> is defined as when the chord <NUM> of the foil <NUM>, <NUM> is parallel to the direction of the fluid flow <NUM>, along the y direction. In operation, a fluid flow <NUM> along the y direction is incident upon the leading edge <NUM> of the foil <NUM>, <NUM>. The angle of attack of the foil <NUM>, <NUM> generates lift (FL) in the positive x direction, inducing a pivoting motion of the vibrational member <NUM> about the bearing <NUM>. This pivoting motion is limited by a first pivot stop <NUM> such that the vibrational member <NUM> stops in a second position <NUM> where the vibrational member <NUM> is angled at +α relative to the z axis as depicted by <FIG>.

When in the second position <NUM>, the weight and or inertia of the foil <NUM>, <NUM> results in a rotating force (FR) inducing a rotation motion of the foil <NUM>, <NUM> an axis <NUM> defined by the vibrational member <NUM> itself, the axis <NUM> extending between the first and second ends <NUM>, <NUM>. This rotation is limited by a first rotation stop <NUM>. The rotation of the foil <NUM>, <NUM> reverses the angle of attack of the foil <NUM>, <NUM> such that the chord <NUM> of the foil <NUM>, <NUM> is angled of +β relative to the central rotation position <NUM> as can be by <FIG> which depicts a third position <NUM>. It will be appreciated that the position of the axis <NUM> relative to the foil <NUM>, <NUM>, in particular, the position of the axis <NUM> along the chord <NUM> of the foil <NUM>, <NUM>, determines the relative ease at which the foil <NUM>, <NUM> will rotate. For example, the axis <NUM> may be offset closer to the leading edge <NUM> of the foil <NUM>, <NUM> as opposed to the trailing edge <NUM>. As such, the position of the axis <NUM> may be optimised such to achieve the desired rotation characteristic of the foil <NUM>, <NUM>.

In the third position, the fluid flow <NUM> about the foil <NUM>, <NUM> generates lift (FL) in the negative x direction, inducing a relative reverse pivoting motion of the vibrational member <NUM> about the bearing <NUM>. This reverse pivoting motion is limited by a second pivot stop <NUM> such that the vibrational member <NUM> stops in a fourth position <NUM> where the vibrational member <NUM> angled at -α relative to the central pivot position <NUM> as depicted by <FIG>.

When in the fourth position <NUM>, the weight and or inertia of the foil <NUM>, <NUM> again results in a rotating force (FR) inducing in a reverse rotation motion of the foil <NUM>, <NUM> about the axis defined by the vibrational member <NUM>. This rotation is limited by a second rotation stop <NUM>. After which, the chord <NUM> of the foil <NUM>, <NUM> is angled of -β relative to the central rotation position <NUM>, thereby returning the arrangement to the first position <NUM> as depicted by <FIG>. The pivot and rotation cycle repeats.

The first and second pivot stops <NUM>, <NUM>, which can clearly be seen in <FIG>, limit the pivoting range of the vibrational member <NUM>. The position of the first and second pivot stops <NUM>, <NUM> can be adjusted according to the desired pivot range. The vibrational member <NUM> may pivot between <NUM> and <NUM>° either side of the central pivot position <NUM>. Preferably, the vibrational member <NUM> pivots between <NUM>° to <NUM>° either side of the central pivot position <NUM>. Preferably, the vibrational member <NUM> pivots between <NUM>° to <NUM>° either side of the central pivot position <NUM>.

Similarly, the first and second rotation stops <NUM>, <NUM>, as depicted in <FIG>, limit the rotation of the vibrational member <NUM> and as such the foil <NUM>, <NUM>. The position of the first and second rotation stops <NUM>, <NUM> can be adjusted according to the desired rotation range, in other words, the desired angle of attack of the foil <NUM>, <NUM>. The vibrational member <NUM> and foil <NUM>, <NUM> may rotate between <NUM> and <NUM>° either side of the central rotation position <NUM>. Preferably, the combination of the vibrational member <NUM> and foil <NUM>, <NUM> rotates between <NUM>° to <NUM>° either side of the central rotation position <NUM>.

The energy conversion means <NUM> located at the second end <NUM> end of the vibrational member <NUM> exhibits only a pivoting motion and not a rotation motion. The rotation motion is isolated to the vibrational member <NUM> and foil <NUM>, <NUM>. As such, the pivot motion drives the energy conversion means <NUM> whereas the rotation motion perpetuates and or assists the pivot motion.

<FIG> depicts the energy conversion means <NUM> located at the second end <NUM> of the vibrational member <NUM>. The second end <NUM> of the vibrational member <NUM> comprises a curved rack <NUM>, in other words, a toothed track. The rack <NUM> is orientated and positioned engage with a pinion <NUM> also termed a cog or a gear. The pinion <NUM> is connected to an axle <NUM>, which is in term connected to an electric generator <NUM>. In operation, the pivoting motion of the vibrational member <NUM> cyclically displaces the rack <NUM> in the x direction, rotating the pinion <NUM>. The pinion <NUM> rotates the axle <NUM> which drives the electric generator <NUM> thereby generating electricity. It will be appreciated that the axle <NUM> is not essential as the pinion <NUM> may be directly connect to the electric generator. It will also be appreciated that an alternative transmission system could be envisaged to translate the pivoting motion of the vibrational member to the electric generator.

As can be seen in <FIG>, the bearing <NUM>, alternatively termed the bearing assembly, comprises a bearing axle <NUM> mounted in the x-y plane across a cavity <NUM> in the generator housing 5a, and a bearing housing <NUM> attached to the bearing axle <NUM>. The vibrational member <NUM> passes through the generator housing 5a by passing through the bearing housing <NUM> at an orientational substantially perpendicular to the bearing axle <NUM>. The movement of the vibrational member <NUM> is constrained by the bearing <NUM>. The vibrational member <NUM> can pivot about the bearing axle <NUM> and the vibrational member <NUM> can also rotate about the axis <NUM> defined by the vibrational member <NUM> itself.

<FIG> depicts alternative bearings <NUM>, 43i, 43j each comprising a bearing axle <NUM>, mounted by two brackets <NUM>, and a bearing housing <NUM>, attached to the bearing axle <NUM>. These alternative bearings <NUM>, 43i, 43j illustrate alternative transmission systems to translate the pivoting motion of the vibrational member to the electric generator <NUM>.

More specifically, <FIG> depicts an alternative curved rack <NUM>, in other words, a toothed component, at the second end <NUM> of the vibrational member <NUM>. <FIG> depicts a curved rack 75i attached to the bearing axle <NUM>, instead of the second end <NUM> of the vibrational member <NUM>. Similarly, <FIG> depicts a gear <NUM> attached to the bearing axle <NUM>.

As an additional or alternative feature, the bearings <NUM>, 43i, 43j depicted in <FIG> each comprise a pitch control mechanism <NUM> located on the bearing housing <NUM>. The pitch control mechanism <NUM> comprises a servomotor <NUM> and a drivetrain <NUM> connecting the servomotor <NUM> to the vibrational member <NUM>. The drivetrain <NUM> may take the form of gears and a belt or chain. The pitch control mechanism <NUM> can rotate the vibrational member <NUM>, and the foil <NUM>, <NUM> connected to the first end <NUM> of the vibrational member <NUM>, about the axis <NUM> of the vibrational member <NUM>. In other words, the pitch control mechanism <NUM> controls the pitch of the foil <NUM>, <NUM> connected to the first end <NUM> of the vibrational member <NUM>. As an alternative or in addition to the first and second rotation stops <NUM>, <NUM>, the rotation of the vibrational member <NUM> can be limited by the pitch control mechanism <NUM>. As an additional function, the pitch control mechanism <NUM> can optimise the position of the foil <NUM>, <NUM>, for example, by dynamically adjusting the pitch according to the velocity and or direction of the fluid flow <NUM>, <NUM>. It will be appreciated the pitch control mechanism <NUM> may be integral within the bearing housing <NUM>.

As an additional or alternative feature, the rotational position of the vibrational member <NUM> is biased away from the central rotational position <NUM> by a cam and or the pitch control mechanism. Advantageously, this would ensure the chord <NUM> of the foil <NUM>, <NUM> was never parallel to the direction of the fluid flow <NUM>. As such, the foil <NUM>, <NUM> would be biased towards an angle of attack that generates an aerodynamic force.

The servomotor <NUM> may be connected to a sensor and control system. The sensor may therefore be employed to measure the velocity and direction of the fluid flow <NUM> at the inlet opening <NUM> and the control system then acts to adjust the orientation of the foils <NUM>, <NUM> to optimise their pitch angles.

The linear or pivoting motion of a foil <NUM>, <NUM>, as shown in <FIG>, is translated into a rotational motion of a pinion <NUM> which drives an electric generator <NUM>, as shown in <FIG>. This rotational motion exhibited by the pinion <NUM> is oscillatory in that it alternates between a clockwise and anticlockwise rotation. As a further additional or alternative feature, the energy harvesting device <NUM>, and specifically the energy conversion means <NUM>, further comprises a clutch mechanism <NUM>, as depicted in <FIG>, which converts the oscillatory rotational motion into unidirectional rotational motion.

The clutch mechanism <NUM> comprises an oscillating input shaft <NUM> and a unidirectional output shaft <NUM>. The oscillating input shaft <NUM> is driven by the oscillating pinion <NUM> and further comprises a first sprag clutch bearing <NUM> with a clockwise drive direction and a second sprag clutch bearing <NUM> with an anticlockwise drive direction. The clockwise rotating, first sprag clutch bearing <NUM> meshes directly with an anticlockwise rotating, first spur gear <NUM> located on the unidirectional output shaft <NUM>. The anticlockwise rotating, second sprag clutch bearing <NUM> meshes with an anticlockwise rotating, second spur gear <NUM> located on the unidirectional output shaft <NUM>, through a clockwise rotating, intermediate gear <NUM>.

In operation, a clockwise rotation of the oscillating input shaft <NUM> is translated to an anticlockwise rotation of the unidirectional output shaft <NUM> by the combination of the first sprag clutch bearing <NUM> and the first spur gear <NUM>. An anticlockwise rotation of the oscillating input shaft <NUM> is translated to an anticlockwise rotation of the unidirectional output shaft <NUM> by the combination of the second sprag clutch bearing <NUM>, the intermediate gear <NUM> and the first spur gear <NUM>. In summary both clockwise and anticlockwise rotation of the oscillating input shaft <NUM> in converted into anticlockwise rotation of the unidirectional output shaft <NUM>. The first and second sprag clutch bearings <NUM>, <NUM> freewheel when not rotating in the respective drive directions.

Advantageously, the clutch mechanism <NUM> results in a unidirectional rotational motion which broadens the type of electric generators <NUM> that could be utilised within the energy harvesting device <NUM>.

The rotational speed of the unidirectional output shaft <NUM> may not be uniform due to the nature of the pivoting motion. More specifically, the rotational speed is faster when the vibrational member <NUM> passes through the central pivot position <NUM> and slower when it reaches the first and second pivot stops <NUM>, <NUM>. As an additional or alternative feature, the pivoting motion may be modified to reduce the variability in rotational speed of the unidirectional output shaft <NUM>, by using magnets to repel the vibration member <NUM> and or springs exerting a force upon the vibrational member <NUM>. Additional or alternative feature, the variability in the rotational speed may also be reduced by mechanically storing the rotational motion in a fly wheel or spring mechanism and then releasing this stored energy at a constant rotational speed. In an alternative embodiment, multiple foils <NUM>, <NUM> may be connected to the clutch mechanism <NUM> or spring mechanism without affecting its independent oscillatory motion.

As a further additional or alternative feature, the pivoting motion may be limited by magnetic end stops, springs and or the servomotor <NUM> as opposed to the mechanical first and second pivot stops <NUM>, <NUM>. Advantageously, minimising the percussive action, by replacing the mechanical pivot stops with magnetic pivot stops, would reduce the energy loss within the transmission system and thereby increasing the lifetime of the components.

It will be appreciated that the above described oscillatory to rotation conversion mechanisms of the foils <NUM>, <NUM> presented in <FIG> may be replaced with an oscillatory to linear conversion mechanism which can then be connected to a linear generator. Although rotary electric generators are easier to work with, they generally exhibit higher mechanical losses when compared with linear electric generators. As such, embodiments based on an oscillatory to linear conversion mechanisms are found to exhibit improved mechanical efficiencies.

As can be seen in <FIG>, the energy harvesting device <NUM> comprises a plurality of foils <NUM>, <NUM>. More specifically, <FIG> depicts two foils <NUM>, <NUM> in each of the six ducts <NUM> of the energy harvesting device <NUM>. It will be appreciated that each duct <NUM> may comprise more or less foils <NUM>, <NUM> and the energy harvesting device <NUM> may comprise more or less ducts <NUM>. The generator <NUM> comprises multiple vibrational members <NUM> and energy conversion means <NUM>. A single foil <NUM>, <NUM> is attached to a single vibrational member <NUM> which is in turn connected to the energy conversion means <NUM>. The energy conversion means <NUM> may comprise a plurality of independent rack <NUM> and pinion <NUM> arrangements attached to a plurality of independent electric generators <NUM>. As such, each foil <NUM>, <NUM> independently moves according to the motion depicted in <FIG> and independently generates electricity. It will also be appreciated, as an additional or alternative configuration, multiple vibrational members <NUM> can drive a central drive shaft connected to a single electric generator <NUM>. In this embodiment the transmission system is configured such that the conversion of motion in one-way. In other words, each aerofoil <NUM>, <NUM> and vibrational member <NUM> can independently drive the central shaft.

The embodiment of <FIG> translates linear movement of a foil <NUM>, <NUM> into rotational movement which drives a conventional electrical generator <NUM>. Advantageously, the energy harvesting device <NUM> of <FIG> is simpler than the devices of <FIG> as comprises a electric generator <NUM> as opposed to a custom magnet <NUM> and coil <NUM> arrangement. As such, the device is simpler and cheaper to manufacture and more reliable.

<FIG> depicts an alternative embodiment of the energy harvesting device <NUM>. As an additional or alternative feature the cross-sectional area of the duct <NUM> may decrease and then increase in the direction of the central axis <NUM>, between the first and second surfaces <NUM>, <NUM>. This constriction of the duct <NUM> increases the velocity of the fluid flow <NUM> in the narrow region of duct <NUM> where the one or more foils <NUM>, <NUM> are located. Advantageously, the increase in velocity of the fluid flow <NUM> enhances the forces induced by the one or more foils <NUM>, <NUM>.

Furthermore, according to the Venturi effect, this constriction results in a reduction of fluid pressure in the narrow region of the duct <NUM>. As another additional or alternative feature, the duct <NUM> may comprise one or more side wall inlets <NUM> in the narrow region of the duct <NUM> such that the lower fluid pressure draws more fluid into the duct <NUM>. This increases the energy captured and further enhances the operation of the energy harvesting device <NUM>,.

<FIG> shows a flow chart for a method of manufacturing an energy harvesting device <NUM>. The method comprises: providing a duct with an inlet and an outlet opening (S1001); providing one or more foils located within the duct wherein a leading edge of the one or more foils is orientated towards the inlet opening (S1002); and providing a generator to convert movement of the one or more foils into electricity (S1003).

In addition, the method of manufacturing may optionally comprise characterising the fluid flow <NUM>, <NUM>. For example, this may include characterising: the mean fluid flow speed, fluid flow speed distribution, turbulence, fluid flow shear profile, distribution of fluid flow direction and long-term temporal fluid flow variations.

As a further addition, the method of manufacturing may option comprises utilising the characteristics of the fluid flow <NUM>, <NUM> to determine the optimum parameters of the energy harvesting device <NUM>. For example, this optimisation process may include determining: the dimensions of the energy harvesting device <NUM>; the dimension and shape of the ducts <NUM>, the shape and structure of the foils <NUM>, 25a, 25b, 25c; the dimension, shape, material composition, orientation and arrangement of the vibrational apparatus; the relative positioning of two or more foils <NUM>, 25a, 25b, 25c within a duct <NUM>; the arrangement and configuration of features for adjusting the fluid flow <NUM> such as the fins <NUM>, flaps <NUM>, mesh <NUM> and flow restrictors <NUM>; and the arrangement and configuration of the generator <NUM>. Optimising the vibrational apparatus may comprises optimising the vibrational lens <NUM> by matching the average resonant frequency across the operational range of the foil <NUM>, 25a, 25b, 25c.

The energy harvesting device <NUM> has numerous advantages. In an embodiment, the device can operate without aerodynamic or hydrodynamic lift moving a foil. Instead, the energy harvesting devices 1a, 1b, 1c, 1d, 1e, 1f depicted in <FIG> harvests the vibrational energy induced within one or more foils <NUM>, 25a, 25b, 25c and specifically, flutter vibrations induced by counter interacting lift.

Advantageously, the energy harvesting device <NUM> can be optimised to operate over a broad range of fluid flow parameters, such as fluid flow speed, reducing the problematic intermittency associated with devices known in the art.

A further advantage is that the energy harvesting device <NUM> can be compact, is modular and can form part of a larger system <NUM>. The energy harvesting device <NUM> and systems <NUM> can be discretely integrated into the environment in the form walls but are also suitable for locations typically not considered for devices known in the art, such as urban landscapes, motorways, airports and even under water locations. The energy harvesting device <NUM> is not limited to remote areas, often considered areas of natural beauty and so there is no reason for a negative public opinion.

Advantageously, the energy harvesting device <NUM> does not comprise relatively large moving external components which can kill birds or fish depending on where the energy harvesting device <NUM> is located. The moving components of the energy harvesting device <NUM> are all internal and only exhibit small scale movement such as vibrations, pivoting and rotation movements. Furthermore, the energy harvesting device <NUM> comprises features which minimise the risk to wildlife such as the mesh <NUM> which prevents birds or fish from entering the duct <NUM> through the inlet opening <NUM>.

The energy harvesting device <NUM> can be optimised accordingly to the characteristics of the fluid flow <NUM> such that the device <NUM> is suitable for a broad range of applications. The functionality of the energy harvesting devices <NUM> can be maximised by incorporating addition features such as noise insulation <NUM>.

An energy harvesting device is disclosed. The energy harvesting device comprises a duct with an inlet opening and an outlet opening. The energy harvesting device further comprises one or more foils located within the duct wherein a leading edge of the one or more foils are orientated towards the inlet opening. The energy harvesting device also comprises a generator to convert movement of the one or more foils into electricity. The generator comprises one or more vibrational members and an energy conversion means. The one or more vibrational members are configured to exhibit both pivoting motion and the one or more foils are configured to exhibit a rotation motion. The foils may be aerofoils or hydrofoils. The energy harvesting device provides an alternative device for generating renewable energy with numerous advantages. The device harvests vibrational energy, can be optimised to operate over a broad range of fluid flow parameters, has minimal negative environmental impact and is suitable for numerous locations and applications.

Throughout the specification, unless the context demands otherwise, the terms "comprise" or "include", or variations such as "comprises" or "comprising", "includes" or "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, unless the context clearly demands otherwise, the term "or" will be interpreted as being inclusive not exclusive.

Claim 1:
An energy harvesting device (<NUM>) comprising:
two or more ducts (<NUM>) each with an inlet opening (<NUM>) and an outlet opening (<NUM>); and
a generator comprising one or more vibrational members (<NUM>) and an energy conversion means (<NUM>),
wherein the one or more vibrational members (<NUM>) are configured to exhibit a pivoting motion about a pivot axis which drives the energy conversion means (<NUM>);
each of the two or more ducts (<NUM>) comprising one or more foils (<NUM>) located within the duct (<NUM>) between the inlet and outlet openings (<NUM>, <NUM>), wherein a leading edge (<NUM>) of the one or more foils (<NUM>) is orientated towards the inlet opening (<NUM>);
the one or more foils (<NUM>) are attached to a first end (<NUM>) of the one or more vibrational members (<NUM>) and configured to exhibit a rotation motion about a rotation axis extending between the first end (<NUM>) and a second end (<NUM>) of the one or more vibrational members (<NUM>) and parallel to a span direction of the one or more foils (<NUM>), the rotation axis being perpendicular to the pivot axis; and
the rotation motion of the one or more foils (<NUM>) configured to assist the pivoting motion of the one or more vibrational members (<NUM>), wherein the energy conversion means (<NUM>) is located at the second end (<NUM>) of the one or more vibrational members (<NUM>), whereby the generator converts movement of the one or more foils (<NUM>) into electricity.