Patent Description:
Known wingsails include wingsails comprised of a single aerofoil. Wingsails comprising multiple aerofoils are also known. Wingsails can be used for marine vessels to reduce energy requirements during operation, for example during transport of goods. This reduction in energy requirements can reduce carbon emissions.

<CIT>describes a rigid sail device designed to prevent an air flow along a wing surface of a rigid sail from burbling by arranging a foldable flap adjacent to each wing part of a main wing of the rigid sail.

<CIT> discloses a wingsail comprising a first aerofoil having a leading edge at a front of the wingsail and a trailing edge behind the leading edge; and a second aerofoil having a leading edge and a trailing edge, the leading edge of the second aerofoil being closer than the trailing edge of the second aerofoil to a point of maximum cross-sectional width of the second aerofoil; wherein the wingsail is configured such that the leading edge of the second aerofoil can be positioned behind the trailing edge of the first aerofoil.

According to the invention as claimed, there is provided a wingsail comprising: a first aerofoil having a leading edge at a front of the wingsail and a trailing edge behind the leading edge; and a second aerofoil having a leading edge and a trailing edge, the leading edge of the second aerofoil being closer than the trailing edge of the second aerofoil to a point of maximum cross-sectional width of the second aerofoil; wherein the wingsail is configured such that the leading edge of the second aerofoil can be positioned behind the trailing edge of the first aerofoil; wherein the first aerofoil comprises: an air inlet comprising a port air inlet positioned on a port side of the first aerofoil and a starboard air inlet positioned on a starboard side of the first aerofoil; an air outlet; a channel inside the first aerofoil connecting the air inlet and the air outlet; wherein air flow from the air inlet is directed by the channel to the air outlet and the air flow from the air outlet is directed out of the air outlet towards the leading edge of the second aerofoil.

According to some examples, the second aerofoil has a first portion comprising the leading edge of the second aerofoil, wherein the first portion is rounded.

According to some examples, the second aerofoil is symmetrical along a chord line of the second aerofoil.

According to some examples, the chord line comprises a longitudinal axis from the leading edge to the trailing edge.

According to some examples, the air outlet is positioned at the trailing edge of the first aerofoil.

According to some examples, wherein when the wingsail is being used on a starboard tack the first aerofoil is configured so that air flow is directed through the port air inlet and is not directed through the starboard air inlet, and wherein when the wingsail is being used on a port tack the first aerofoil is configured so that air flow is directed through the starboard air inlet and is not directed through the port air inlet.

According to some examples, the wingsail is configured to: rotate the second aerofoil to starboard relative to the first aerofoil when the wingsail is used on a starboard tack such that the air outlet of the first aerofoil directs air flow towards the port leading edge of the second aerofoil; and rotate the second aerofoil to port relative to the first aerofoil when the wingsail is being used on a port tack such that the air outlet of the first aerofoil directs air flow towards the starboard leading edge of the second aerofoil.

According to some examples, the wingsail is configured to: when the wingsail is being used on a starboard tack, draw air in the port air inlet and not draw air in the starboard air inlet, and when the wingsail is being used on a port tack, draw air in the starboard air inlet and not draw air in the port air inlet.

According to some examples, the wingsail comprises: a pressure differential generator in the first aerofoil, the pressure differential generator configured to create negative internal pressure in the first aerofoil, wherein the negative internal pressure draws air into the main body of the device through the air inlet.

According to some examples, the pressure differential generator comprises: one or more fans driven by a motor; or a series of fans connected by one fan shaft and driven by a motor.

According to some examples, the channel comprises the pressure differential generator and an air vent.

According to some examples, the second aerofoil rotates to a maximum rotation position relative to the first aerofoil to minimise a total span of the wingsail, and wherein the wingsail folds at a base of the wingsail to form a stowed configuration.

According to some examples, the base of the wingsail is formed from at least one welded or seamless metal pipe.

According to some examples, the wingsail comprises a protective casing for covering the first aerofoil and the second aerofoil in the stowed configuration, wherein the protective casing allows the wingsail to be raised and/or lowered and allows the wingsail to be covered when the wingsail is lowered and in the stowed configuration by performing at least one of the following: folding; rotating; rolling along a track.

According to some examples, the wingsail comprises control software for opening and closing the inlet or directing the flow from one air inlet to the next; a mechanical control system for opening and closing the inlet.

According to some examples, the wingsail comprises a mechanical system which is triggered to open or close the inlet based on the movement of the second aerofoil.

According to some examples, the wingsail is configured to form a stowed configuration by: rotating the second aerofoil relative to the first aerofoil such that the chord lines of each aerofoil are substantially perpendicular to one another; and then rotating both aerofoils from the base of the wingsail to a horizontal position to form a stowed configuration.

According to some examples, the wingsail comprises a base structure, the base structure comprising: three or more pillars supporting a platform, each of the three or more pillars having a height between two metres and four metres, wherein the first aerofoil and second aerofoil are positioned above the platform.

According to some examples, the wingsail comprises a linear actuator for raising and lowering the wingsail, the linear actuator being positioned above the platform.

According to some examples, a wingsail and a method for operating a wingsail is described. The wingsail may be used for a watercraft. A watercraft may comprise, for example, at least one of: a marine vessel, a boat, a ship. In some examples, the watercraft may comprise a powered watercraft. In some examples, the watercraft may comprise a commercial vessel such a bulk carrier or a product tanker.

According to some examples, a wingsail may be positioned on a surface of a watercraft, for example on the deck of a watercraft.

An exemplary wingsail may be rigid. The wingsail may be fitted to a marine vessel (e.g., a powered watercraft, a ship, etc.). A wingsail may be considered to be a variable-camber aerodynamic structure that is fitted to a vessel, e.g., a marine vessel.

A typical marine vessel length to be fitted with these units may be between <NUM> and <NUM> but may also be fitted to a smaller or larger vessel. In some examples, the wingsail is used to produce thrust which is transferred to the vessel to propel it forwards and reduce the thrust required from the ship's engine. In some examples, this can reduce the power required from the main engine and reduces fuel consumption and carbon emissions by around <NUM>-<NUM>%, dependent on vessel type, route, number of wingsail units and other considerations.

Some example wingsails described herein may comprise at least two wingsail elements. Each wingsail element may comprise a leading edge and a trailing edge. Each wingsail element may have an aerodynamic shape (for example, a shape similar to the shape of aerofoil element <NUM> or aerofoil element <NUM> in <FIG>). The aerodynamic shape of each wingsail element may generate a lift force when air flow passes over the surface of the respective wingsail element. Each wingsail element may comprise an aerofoil.

According to some examples, the leading edge of each aerofoil is closer to the broadest part of the aerofoil, while the trailing edge of each aerofoil is further from the broadest part of the aerofoil. Other example shapes may be used for the aerofoils, however.

The wingsail may incorporate boundary layer flow control. A boundary layer of a wingsail may be considered to comprise a thin layer of air flowing over the surface. According to some examples, the flow of air in the boundary layer is controlled to prevent separation of air flow over the wingsail and thus reduce the wingsails propensity to stall. This enables a greater achievable lift of the wingsail.

<FIG> shows a perspective view of an example wingsail <NUM>. Wingsail <NUM> is a double element wingsail having a first aerofoil <NUM> and a second aerofoil <NUM>. One of the double elements of wingsail <NUM> is first aerofoil <NUM> and one of the double elements of wingsail <NUM> is second aerofoil <NUM>. First aerofoil <NUM> comprises a leading edge 103a, a trailing edge 103b and a section 103c of maximum cross-sectional width. As can be seen in the example of <FIG>, leading edge 103a is closer to section 103c of maximum cross-sectional width than trailing edge 103b. A portion of aerofoil <NUM> comprising leading edge 103a is rounded, and a portion of aerofoil <NUM> comprising trailing edge 103b is pointed (or may be a rounded shape which has a radius smaller than that of the leading-edge curvature). In some examples, the portion of aerofoil <NUM> comprising leading edge 103a has a wider cross-sectional width than the portion of aerofoil <NUM> comprising trailing edge 103b. It is envisaged that other shapes may be used for first aerofoil <NUM>, however.

Second aerofoil <NUM> comprises a leading edge 105a, a trailing edge 105b and a section 105c of maximum cross-sectional width. Leading edge 105a is closer to section 105c of maximum cross-sectional width than trailing edge 105b. A portion of aerofoil <NUM> comprising leading edge 105a is rounded, and a portion of aerofoil <NUM> comprising trailing edge 105b is pointed. It is envisaged that other shapes may be used for first aerofoil <NUM>, however.

Second aerofoil <NUM> may be symmetrical along a chord line of second aerofoil <NUM>, as shown in <FIG> and <FIG> for example.

First aerofoil <NUM> may be symmetrical along a chord line of second aerofoil <NUM>, as shown in <FIG> and <FIG> for example.

A chord line of an aerofoil may be considered to be a longitudinal axis from the leading edge to the trailing edge of the aerofoil.

Leading edge 103a may be considered to be at a nominal "front" of wingsail <NUM>. Trailing edge 103b is behind leading edge 103a. In the feathered configuration of <FIG>, the second aerofoil <NUM> is behind the first aerofoil <NUM>, and the leading edge 105a of the second aerofoil <NUM> is in front of the trailing edge 105b of the second aerofoil <NUM>.

Aerofoils <NUM> and <NUM> have "teardrop" shapes but other aerodynamic shapes may be used. In general, an aerofoil such as aerofoils <NUM> or <NUM> can have any shape that produces an aerodynamic reaction (lift) perpendicular to the direction of air flow over it, for a small resistance (drag) force in the direction of air flow.

The wingsail device <NUM> may rotate around its base to vary an angle of attack to the apparent wind direction. In this way, wingsail device <NUM> can optimise lift produced. The lift is generated by the creation of a pressure differential between either side of wingsail <NUM>, leading to a high pressure and a low-pressure side due to a difference in air velocity over each side of the wingsail device <NUM>. Apparent wind is the wind that a moving watercraft experiences. Apparent wind is a combination of the wind experienced because of forward motion of the ship combined with the prevailing wind. The two vectors combine to produce 'apparent wind' which may have a different angle and wind speed than the wind experienced because of the forward motion of the ship and the prevailing wind.

The second aerofoil <NUM> is rotatable relative to the first aerofoil <NUM>, allowing the camber of the device <NUM> to be adjusted and inverted.

When the wingsail device <NUM> is on a port tack (when the apparent wind is hitting the port side of the device <NUM>) the second aerofoil <NUM> can be rotated to the port side relative to the first aerofoil <NUM>.

When the wingsail device <NUM> is on a starboard tack (when the apparent wind is hitting the starboard side of the device) the second aerofoil <NUM> is rotated to the starboard side relative to the first aerofoil <NUM>.

When second aerofoil <NUM> is rotated relative to first aerofoil <NUM>, as seen for example in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, the chord lines of the first aerofoil <NUM> and second aerofoil <NUM> are not parallel. This provides a cambered configuration for the wingsail device <NUM>. This can be achieved by rotating the second aerofoil <NUM> relative to first aerofoil <NUM>.

In a cambered configuration of device <NUM>, a slot is formed between the first aerofoil <NUM> and the second aerofoil <NUM>. This slot allows a high-pressure stream of air to flow from the high-pressure side to the surface of the low-pressure side. This re-energises the flow travelling over the second aerofoil and allows the flow to stay attached at more extreme angles of attack and avoid stall of the wingsail, allowing greater lift coefficients to be achieved.

In some examples, wingsail <NUM> can be fitted with a pressure differential generator <NUM> (as shown in <FIG>, for example). Pressure differential generator <NUM> can be used to provide control of the flow of air around the device <NUM>. This controlled flow allows the device to be used at a greater angle of attack and greater camber angle without stalling, thus greatly increasing the achievable lift coefficients for wingsail <NUM>. In some examples pressure differential generator may comprise one or more rotary blades (e.g., fan blades) which may be connected by a shaft.

To provide control of airflow around wingsail <NUM>, air inlet <NUM> draws air into an interior of wingsail <NUM>. Wingsail <NUM> also comprise an outlet <NUM>. In some examples, for example as shown in <FIG> and <FIG>, outlet <NUM> may be positioned at a trailing edge 103b of first aerofoil <NUM>. However, it will be appreciated that in other examples outlet <NUM> may be positioned at other positions in first aerofoil <NUM>.

Air drawn in at inlet <NUM> can be directed through an interior channel <NUM> inside of aerofoil <NUM>. The interior channel <NUM> connects air inlet <NUM> and air outlet <NUM>. Air outlet <NUM> emits air flow, which may comprise a focused jet of air, out of aerofoil <NUM>. This air flow may be directed towards the surface of the second aerofoil element <NUM>. In the example of <FIG> and <FIG>, the air flow can be emitted out of outlet <NUM> at trailing edge 103b of first aerofoil <NUM> towards and onto a leading edge 105a of aerofoil <NUM>.

Pressure differential generator <NUM> may be powered by one or more motors. These motors may comprise hydraulic or electric motors, for example. When operated, pressure differential generator <NUM> may create an area of low pressure at inlet <NUM> of channel <NUM> such that air is sucked in, and an area of high pressure at outlet <NUM> of channel <NUM> such that air is pushed out of outlet <NUM>.

Pressure differential generator 111figu may be configured to create negative internal pressure in the first aerofoil, wherein the negative internal pressure draws air into the main body of the first aerofoil through air inlet <NUM>.

Pressure differential generator <NUM> may comprise, for example, a fan driven by a motor; or a series of fans connected by one fan shaft and driven by a motor.

According to some examples, flow hits the leading edge of the first aerofoil element <NUM> and flows around the surface (on both sides). As air flow travels over the low pressure surface the laminar boundary layer starts to transition into turbulent flow, if the angle of attack of the device <NUM> is increased at this point the flow will separate and the device <NUM> will stall.

So that the device <NUM> can operate at higher angles of attack (and therefore generate more lift), in some examples the air traveling over the surface of the front aerofoil <NUM> is sucked internally at a location near the back end of the front aerofoil <NUM>. This removes part of the turbulent boundary layer and keeps the flow attached at higher angles of attack, thus achieving greater producible thrust of device <NUM>.

A second aerofoil <NUM> is located behind the first aerofoil <NUM> and when aerofoil <NUM> is cambered it produces a slot between the first aerofoil <NUM> and second aerofoil <NUM>. This slot allows a high-pressure jet of air from the high-pressure side (<NUM> in <FIG>, <NUM> in <FIG>) to the low-pressure side (<NUM> in <FIG>, <NUM> in <FIG>) allowing the flow again to stay attached at higher angles of attack and camber angles - which in a similar way means that the device can produce greater thrust to the vessel.

An air outlet <NUM> may be positioned at the trailing edge of the first aerofoil element <NUM> to further enhance the high-pressure jet of air traveling through the slot and thus allow the wingsail <NUM> to maximise the achievable angle of attack before stall and maximise the thrust produced whilst also reducing drag.

As such, by using at least one inlet <NUM> and at least one outlet <NUM> on the first aerofoil <NUM> higher angles of attack of device <NUM> can be achieved without stalling. Additionally, or alternatively, higher angles of attack of device <NUM> can be achieved without stalling by cambering second aerofoil <NUM> relative to first aerofoil <NUM>.

<FIG> shows a cross sectional plan view of wingsail <NUM>. As shown in <FIG>, air inlet <NUM> comprises two air inlets <NUM> and 107p provided on both sides <NUM> and <NUM> (the port side <NUM> and the starboard side <NUM>, respectively) of first aerofoil <NUM>. In the example of <FIG>, air inlet <NUM> is situated towards trailing edge 103b of first aerofoil <NUM>. Each air inlet <NUM> may comprise a vertical strip (or vertical strips) allowing air to flow into aerofoil <NUM>. The vertical strip(s) may comprise a gap in the device allowing air to flow in. In other examples, the air inlet may comprise a surface with cut openings (such as circular holes or other shapes) or other porous material allowing air to flow into the first aerofoil <NUM>. This surface with cut shapes or porous material controls the speed and volume of air flow into the wingsail to optimize the aerodynamics of the device. It also brings the added benefit that it can prevent debris being sucked into the interior of aerofoil <NUM>.

Air inlet <NUM> draws in unstable flow close to the surface of the device <NUM> into the main body of the first aerofoil <NUM> which allows the flow to stay attached at greater angles of attack, thus leading to greater lift coefficients being produced.

In the example of <FIG>, a partition <NUM> is provided between the main body of aerofoil <NUM> and pressure differential generator <NUM>. In this way, air flow generated affects internal air flow in a portion at the trailing edge 103b of the device, but air flow generated from pressure differential generator <NUM> is prevented from affecting internal air flow within the main body (i.e., in the body positioned at the leading edge 103a) of aerofoil <NUM>.

<FIG> show examples of a wingsail <NUM> under the influence of wind <NUM>. Although wingsail <NUM> is shown in this figure, the same principles may be applied to wingsail <NUM>, <NUM> or any other wingsail described herein.

When wind direction <NUM> is directed directly at the leading edge of a front aerofoil <NUM> of wingsail <NUM> (i.e., the wind direction is directed between the port side <NUM> and the starboard side <NUM> of the wingsail), wingsail <NUM> may be arranged in a feathered configuration. In this configuration, the chord line of aerofoil <NUM> and aerofoil <NUM> are aligned and in parallel with one another.

<FIG> shows an example of a wingsail <NUM> on a port tack. When wingsail <NUM> is working on a port tack, i.e., when the apparent wind <NUM> is crossing the port side of the vessel on which wingsail <NUM> is fitted, the angle of attack of wingsail <NUM> can be configured so that the apparent wind <NUM> is directed to the port leading edge of wingsail <NUM>. Wingsail <NUM> can be cambered in a port configuration where the second aerofoil <NUM> is rotated to the port side <NUM> relative to the first aerofoil <NUM>. In the port configuration, the starboard air inlet <NUM> is open and the port air inlet 107p is closed. The air outlet <NUM> of the first aerofoil <NUM> directs air flow onto the starboard leading edge of the second aerofoil <NUM>, thus re-energising the air flow at this critical point and increasing the stall angle of the device <NUM>.

<FIG> shows an example of a wingsail <NUM> on a starboard tack. When wingsail <NUM> is working on a starboard tack, i.e., when the apparent wind <NUM> is crossing the starboard side of the vessel on which wingsail <NUM> is placed, the angle of attack of wingsail <NUM> can be configured so that the apparent wind <NUM> is directed to the starboard leading edge of wingsail <NUM>. Wingsail <NUM> can be cambered in a port configuration where the second aerofoil <NUM> is rotated to the starboard side <NUM> relative to the first aerofoil <NUM>. In the starboard configuration, the starboard air inlet <NUM> is closed and the port air inlet 107p is open. The air outlet <NUM> of the first aerofoil <NUM> directs air flow onto the port leading edge of the second aerofoil <NUM>, thus re-energising the air flow at this critical point and increasing the stall angle of the device <NUM>.

<FIG> shows an example of how a starboard air inlet <NUM> can be closed during a starboard tack while a port air inlet 107p is open. An interior wall <NUM> is positioned to close a starboard air inlet <NUM> while a port air inlet 107p is left open. Interior wall <NUM> can be rotated around a rotation point <NUM>. This rotation can be performed using a motor, for example an electric or hydraulic motor. Rotation may be performed automatically based on detection by a computer system of wingsail <NUM> of whether wingsail <NUM> is on a port or starboard tack. In some examples, the rotation may be performed based on a user input into a computer system. In other examples, the rotation is performed based on a manual operation of a user of wingsail <NUM>. When wingsail <NUM> is being used on a starboard tack, wingsail <NUM> may draw air in the port air inlet 107p and not draw air in the starboard air inlet <NUM>.

<FIG> shows an example of how a starboard air inlet <NUM> can be open during a port tack while a port air inlet 107p is closed. Wingsail <NUM> may be operated to move between the configuration of <FIG>. An interior wall <NUM> is positioned to close a port air inlet <NUM> while a port air inlet 107p is left closed. Interior wall <NUM> can be rotated around a rotation point <NUM>. This rotation can be performed using a motor, for example an electric or hydraulic motor. Rotation may be performed automatically based on detection by a computer system of wingsail <NUM> of whether wingsail <NUM> is on a port or starboard tack. In some examples, the rotation may be performed based on a user input into a computer system. In other examples, the rotation is performed based on a manual operation of a user of wingsail <NUM>. When wingsail <NUM> is being used on a port tack, wingsail <NUM> may not draw air in the port air inlet 107p and draw air in the starboard air inlet <NUM>.

A computer system as described herein may comprise at least one processor and an associated memory. The computer system may be used to run control software for opening and closing at least one inlet of wingsail <NUM>.

<FIG> shows a cross section through the centre of wingsail <NUM>, in a configuration where the chord lines of aerofoil <NUM> and aerofoil <NUM> are aligned and parallel. <FIG> also shows a side view of a cross section of wingsail <NUM>. As can be seen in <FIG> and <FIG>, an internal air vent <NUM> (a channel) connects air inlet <NUM> to air outlet <NUM>. In the example of <FIG>, the air outlet is positioned at the trailing edge of aerofoil <NUM>. The channel <NUM> may be configured to direct flow from the inlet <NUM> at a first position along a span of the wingsail <NUM> and directs this flow to the air outlet <NUM>, wherein the span of the wingsail <NUM> is a distance from a base of the wingsail <NUM> to a tip of the wingsail <NUM>.

The volume of the air vent is lower at the air outlet <NUM> than at the air inlet <NUM>. The air from pressure differential generator <NUM> is focused as it travels to air outlet <NUM> by a reduction in volume of internal air vent <NUM> from the pressure differential generator <NUM> to air outlet <NUM>, this giving a higher concentration of energized flow which is directed towards the second aerofoil. Air is emitted out of air outlet <NUM> as a focused stream of air where it flows towards the surface of second aerofoil element <NUM>. In some examples, second aerofoil <NUM> may be in a cambered configuration. The focused airflow from air outlet <NUM> re-energises the boundary layer thus allowing the flow to stay attached at greater camber angles and angles of attack, thus increasing the stall angle, and increasing the maximum achievable lift coefficient of wingsail <NUM>.

In the examples of <FIG>, <FIG> and <FIG> channel <NUM> is sloped so that the channel is longer along a vertical axis <NUM> of wingsail <NUM> at air outlet <NUM> than at air inlet <NUM>. Vertical axis <NUM> is shown in <FIG>. This sloped channel shape is useful when wingsail modules such as wingsail <NUM> are stacked on top of each other, as discussed further below with reference to <FIG> and <FIG>. In this example, wingsail modules having the channel shape (the shape of <NUM>) can be stacked upon each other to create a larger wingsail comprising multiple modules. In this case will direct air flow from the air inlet of a higher modular section through a pressure differential generator to the air outlet of a lower modular section. Other channel shapes can be used to provide alternative outcomes, however. For example, if the channel is sloped so that the channel is longer along a vertical axis <NUM> of wingsail <NUM> at air inlet <NUM> than at air outlet <NUM>, air flow will be directed from the air inlet of a lower modular section through a pressure differential generator to the air outlet of a higher modular section. Further, non-sloped (substantially straight, or straight, along a vertical axis <NUM>) channels may be used to direct air flow to an air inlet of a modular section through a pressure differential generator to the air outlet of a same modular section.

In situations where the wingsail is comprised of a single unit (e.g., wingsail <NUM> of <FIG>), any of the above-described three channel shapes may be used. In some examples, a non-sloped channel may be used for a single unit such that the internal air flow would travel from an air inlet at one level through a pressure differential generator and exit at an air outlet at the same level.

According to some examples, a modular wingsail (e.g., wingsail <NUM>) may be made of two or more internal modules covered by an outer shell.

According to some examples, wingsail <NUM> may have a similar dimension to <NUM>, having a greater height than length.

<FIG> shows a cross section through a centre of an example portion of wingsail <NUM>, in a configuration where the chord lines of a front aerofoil and a rear aerofoil of wingsail <NUM> are aligned and in parallel. Wingsail <NUM> may comprise a similar structure as wingsail <NUM>. Wingsail <NUM> additionally includes at least one air flow straightener <NUM> positioned at an air outlet <NUM> of the front aerofoil of wingsail <NUM> to allow the flow to exit the air outlet in a controlled fashion, to maximise an aerodynamic benefit of the controlled airflow. Additionally, or alternatively, at least one air flow straightener may be positioned at an air inlet of the front aerofoil. Further, instead, or additional to at least one air flow straightener being positioned at an air inlet or an air outlet of the front aerofoil of wingsail <NUM>, at least one air flow straightener may be positioned between the air inlet and air outlet of wingsail <NUM>. An air flow straightener may comprise one or more walls placed along an air inlet, air outlet or channel connecting an air outlet and air inlet.

As shown in <FIG>, in some examples, wingsail modules such as wingsail module 601a and 601x may be stacked on top of one another to form a wingsail <NUM>. Each wingsail module 601a, 601x etc. may comprise a similar structure to wingsail <NUM>, wingsail <NUM> or any other wingsail described above.

Each wingsail module <NUM> may comprise an air inlet <NUM>, an air outlet and a pressure differential generator. Each wingsail module <NUM> may be configured to be stacked on top of one another.

<FIG> shows an external view of a wingsail <NUM> comprising wingsail modules 601a and 601x. Further modules may also be included as shown in <FIG>, in some examples. <FIG> shows an internal cross section of wingsail <NUM> comprising wingsail modules 601a and 601x.

Wingsail <NUM> comprises at least two wingsail modules 601a and 601x each having an inlet 607a and 607x which are aligned with each other. Wingsail module 601a comprises an air vent 619a. Wingsail module 601x comprises an air vent 619x. In wingsail <NUM>, an air vent for each wingsail module 601a and 601x (such as air vent 619a and 619x) guides internal air flow from a pressure flow generator to an air outlet for each wingsail module 601a and 601x. Each wingsail module (e.g., wingsail module 601a and 601x) may have its own pressure differential generator. An air vent for each wingsail module may guide internal air flow from an internal pressure differential generator to an air outlet.

Wingsail <NUM> may comprise at least one fan at the trailing edge of the front aerofoil (similar to aerofoil <NUM> in wingsail <NUM>) of each wingsail module 601a, 601x, etc. Each fan may be driven by one or more hydraulic or electric motors. Each fan may be connected by a central shaft made by shaft modules for each wingsail module. In the example of <FIG>, shaft module 617a of wingsail module 601a is connected to shaft module 617x of wingsail module 601x.

Wingsail module 601x is positioned at the top of wingsail <NUM>. Wingsail module 601a is a wingsail module other than top wingsail module 601x. The channel of each module (e.g., channels 617x and 617a) are sloped so that each channel is longer along a vertical axis of each wingsail module 617a and 617x (where both axes are similar to axis <NUM> of wingsail <NUM>) at an air outlet of each wingsail module than at an air inlet of each wingsail module 607a and 607x. As each wingsail module has this channel shape, air flow from the air inlet of a higher modular section through a pressure differential generator to the air outlet of a lower modular section. For example, air flow from air inlet 607x will be directed to an air outlet of a wingsail module directly below wingsail module 601x. Air flow from an air inlet of a wingsail module directly above wingsail module 601a will be directed towards an air outlet of wingsail module 601a. Air flow from air inlet 607a will be directed to an air outlet of a wingsail module directly below wingsail module 601a. As wingsail module 601x is at the top of wingsail <NUM>, air flow is drawn in from above wingsail module 601x and directed towards an air outlet of wingsail module 601x.

As discussed above with relation to <FIG>, <FIG> and <FIG>, other channel shapes may be used to provide different air flow between modules of a modular wingsail. For example, if the channel is sloped so that the channel is longer along a vertical axis of a wingsail module at an air inlet than at an air outlet, air flow will be directed from the air inlet of a lower modular section through a pressure differential generator to the air outlet of a higher modular section. In this case, the bottom wingsail module will draw in air from below the modular wingsail. Further, non-sloped (substantially straight, or straight, along a vertical axis of the wingsail module) channels may be used to direct air flow to an air inlet of a modular section through a pressure differential generator to the air outlet of a same modular section.

In another embodiment of the invention the wingsail may comprise an air inlet as shown in previous examples and an air outlet at the base or the tip of the wingsail. Wherein air is sucked into the air inlet by a fan positioned at the air outlet at the base or the tip of the wingsail and internal flow is directed either up or down the span of the wingsail.

The wingsail devices described herein may comprise one or more internal structure members. For example, a wingsail or wingsail module may comprise, for example, at least one: of a structural steel main spar; an aluminium main spar; a composite main spar. The wingsail may also comprise transverse and/or longitudinal stiffeners made of similar material. In such examples, an outer skin may produce the external aerodynamic shape of the device of the device and may comprise, for example, at least one of: steel; aluminum; composite. The internal air vents (channels) may comprise, for example, at least one of: steel; aluminum; composite.

In some examples, the device may have a monocoque structure having a thicker external skin comprised of, for example, at least one of: steel; aluminium; composite. This monocoque structure may take much of the structural loads of the device.

The device may rotate its angle of attack to the apparent wind using either a slew gear bearing or a bearing with rack and pinion system, wherein this bearing may be connected to the bottom section of the wingsail and connect the wingsail to its base (which is connected to the vessel). This bearing may be located beneath the first aerofoil <NUM> at a position where the wingsail <NUM> is able to naturally weather cock if all systems fail. In a natural weather cocked configuration the wingsail <NUM> will feather to the wind in a similar configuration as shown in <FIG>.

In the above-described examples, only one air inlet (comprised of a starboard air inlet and corresponding port air inlet) in the front aerofoil is described. In further examples, devices may have multiple air inlets each comprising a starboard air inlet and a port air inlet in the front aerofoil.

In the above-described examples, only one air outlet in the front aerofoil is described. In further examples, devices may have multiple air outlets in the front aerofoil.

In further examples, a wingsail may comprise at least one air inlet in the second aerofoil. In further examples, a wingsail may comprise at least one air outlet in the second aerofoil.

According to some examples, wingsail <NUM> may be stowed and protected by a protective covering <NUM>. This process is shown in <FIG>. In <FIG>, wingsail <NUM> is in a stowed configuration and protected by protective covering <NUM>. In <FIG>, protective covering <NUM> is opened, allowing wingsail <NUM> to adjust to different orientations. Protective covering <NUM> may be comprised of steel or other material and this covering may be folded or rotated over the device to protect the device from crane grabs, falling material such as iron ore or other impact causing scenarios which may damage the wing.

According to some examples, a wingsail as described herein may comprise a base plate and an end plate. These plates may improve the aerodynamic performance of the device by reducing vortex shedding as a result of the generation of lift.

According to some examples, a wingsail as described herein may comprise a base plate and an end plate may comprise fences along the span of the device to help direct the flow across the surface of the device and reduce vortex shedding and associated losses.

A double element wingsail comprised of two aerofoils below is described further below with respect to <FIG>. A method for moving the two aerofoils relative to each other is described. It should be noted that aerofoils described with respect to <FIG> below may have air inlets and air outlets to control air flow as described above. Any of the features described with respect to <FIG> below may be incorporated into any of the above-described wingsails, such as wingsail <NUM>, <NUM> and <NUM>, for example.

<FIG> and <FIG> show a wingsail <NUM>. <FIG> shows a port view and <FIG> shows a starboard view. Wingsail <NUM> is comprised of a first aerofoil element <NUM> and a second aerofoil element <NUM>, the first aerofoil element <NUM> is the leading element and the second aerofoil element <NUM> is the trailing element. The second aerofoil element <NUM> is rotatable relative to the first aerofoil element <NUM> to form a cambered shape (as shown in <FIG>) which is beneficial for producing a lift force. Between the first aerofoil element <NUM> and second aerofoil element <NUM>, a 'slot' <NUM> is formed when the second aerofoil element <NUM> is rotated in relation to the first aerofoil element <NUM>, and this slot <NUM> allows high energy flow from the pressure side to flow to the suction side and allows the flow to stay attached at a higher angle of attack - which is beneficial for producing lift. The second aerofoil element <NUM> may be of the same chord length as the first aerofoil element <NUM> but in some cases may be shorter or longer. The thickness of the first aerofoil element <NUM> may be thicker than the second aerofoil element <NUM> to increase the second moment of area of the internal structure and to optimise the aerodynamic performance of the device. The shape of the aerofoil section comprising the first aerofoil element <NUM> and second aerofoil element <NUM> has a maximum thickness within the leading half of the section. The curvature of each aerofoil section comprising aerofoil elements <NUM> and <NUM> is convex along the total length of each section, the curvature remains positive along the total length and does not include any inflections.

The first aerofoil element <NUM> is connected directly to base <NUM> of wingsail <NUM>. Base <NUM> connects wingsail <NUM> to an associated marine vessel. Second aerofoil element <NUM> is connected to base <NUM> of wingsail <NUM> via a connection to first aerofoil element <NUM>.

<FIG> shows some example different configurations of wingsail <NUM>. Wingsail <NUM> as shown in <FIG> is capable of transitioning between a feathered configuration <NUM> in which the cross-sectional centreline <NUM> of both aerofoil elements <NUM> and <NUM> are aligned, to a cambered configuration <NUM> in which the second aerofoil element <NUM> rotates in relation to the first aerofoil element <NUM>. The wingsail <NUM> is also capable of articulating to a configuration where the first aerofoil element <NUM> and second aerofoil element <NUM> form a tightly packed configuration <NUM>.

Wingsail <NUM> can invert its camber in both directions to allow the wingsail to produce lift <NUM> with the wind angle <NUM> coming from both its right and left side, as shown in <FIG>. Wingsail <NUM> is also able to rotate <NUM> degrees around its base <NUM> about an angle of attack axis <NUM> to allow an angle of attack of wingsail <NUM> to be adjusted and optimised to the direction of the wind in relation to the marine vessel. By adjusting both the angle of attack of wingsail <NUM> and a camber of wingsail <NUM>, the aerodynamic flow around wingsail <NUM> can be optimised to produce a desired amount of thrust force.

To allow wingsail <NUM> to be stowed while producing minimal interference during port operations, wingsail <NUM> can minimise its stowed height above a deck of the marine vessel and ensure the first aerofoil element <NUM> and second aerofoil element <NUM> are not protruding in any way. To do this wingsail <NUM> forms a tightly packed configuration as presented in configuration <NUM> of <FIG> and folds from a vertical position to a horizontal position to minimise an overall height of wingsail <NUM>. This process is described in the following paragraphs.

To allow wingsail <NUM> to both adjust its camber and fold into the tightly packed configuration as shown in configuration <NUM> of <FIG>, the second aerofoil element <NUM> can be rotatable relative to the first aerofoil element <NUM> about at least one vertical axis. According to some examples, the at least one vertical axis comprises two vertical axes. At least one linear actuator (preferably a hydraulic ram) may connect to the first and second aerofoil element.

According to some examples, the primary axis <NUM> for rotation of the second aerofoil element <NUM> relative to the first aerofoil element <NUM> may be located within the first aerofoil element <NUM> and the secondary axis <NUM> for rotation of the second aeorofoil element <NUM> relative to the first aerofoil element <NUM> may be located within the second aerofoil element <NUM>. An axis <NUM> may be provided for the rotation of the first aerofoil element <NUM> relative to the base of the wingsail. To connect the first aerofoil element <NUM> and the second aerofoil element <NUM> and create two rotational axis the two aerofoil elements may be connected by a middle linking member <NUM>. Middle linking member <NUM> may house spherical or roller bearings, or other forms of mechanical bearings or rotating joints to freely connect the linking member to first aerofoil element <NUM> and second aerofoil element <NUM>. Linking member <NUM> may comprise a top bar <NUM> and a bottom bar <NUM>, and the top bar <NUM> and bottom bar <NUM> may be connected by a torsional structural member <NUM> to align the top and bottom bar and resist any torsional moments between the tip and the base of the wing. The torsional structural member <NUM> may comprise a torsional spar and may be spherical and comprised of steel, aluminium, or composite. A bottom linear actuator <NUM> at the base of the wing (preferably a hydraulic ram) connects to both the linking member <NUM> (preferably to the bottom bar <NUM>) and to the structure of the first aerofoil element <NUM>, preferably to a first element base structure <NUM> and controls the relative movement of both parts. In a similar manner the wingsail <NUM> may comprise a top linear actuator <NUM> (preferably hydraulic ram) connecting the top bar <NUM> of linking member <NUM> with the structure of the first aerofoil element <NUM> and may connect to the first element end structure <NUM>. The connection of linear actuators <NUM> and <NUM> to wingsail <NUM> may attach to pins fixed between two brackets fixed to each part of the wingsail <NUM> and allow the attachments to freely rotate with the changing angles. Top linear actuator <NUM> and a bottom linear actuator <NUM> are preferably used to drive the rotation of the linking member <NUM> in relation to the first aerofoil element <NUM>. The connection points between the rams <NUM> and <NUM> and the linking member <NUM> may be on both the top bar and bottom bar, and its connection preferably is able to rotate relative to the linking member <NUM>. The linking member may comprise, in addition to top bar <NUM> and bottom bar <NUM>, other connecting bars spaced in between these two bars which may also be fixed to the torsional structure. These connecting bars may also comprise rotational bearings which connect first aerofoil element <NUM> to the second aerofoil element <NUM> and allow rotation between one another by way of two vertical axis. The primary axis <NUM> is a vertical axis preferably within the first aerofoil element <NUM> and runs through the centre of each of the bearings connecting the first aerofoil element <NUM> to the linking member <NUM>. The secondary axis <NUM> is a vertical axis preferably within the second aerofoil element <NUM> and runs through the centre of each of the bearings connecting the second aerofoil element <NUM> to the linking member <NUM>.

The full range of motion of wingsail <NUM> according to some examples is presented in <FIG>. To adjust and invert the camber of wingsail <NUM> the second aerofoil element is rotated about the primary axis <NUM> to complete the range of motion required to actively trim the wing to optimise the aerodynamic flow. This movement may be controlled by one or more linear actuators, preferably one top linear actuator <NUM> at a top <NUM> of wingsail <NUM> and one bottom linear actuator <NUM> at the bottom <NUM> of wingsail <NUM> as shown in <FIG> and <FIG>. As depicted in <FIG>, configuration <NUM> shows the neutral 'feathered' configuration, configuration <NUM> shows maximum working camber to starboard (typically in the range of <NUM>-<NUM> degrees from centre) and configuration <NUM> shows maximum working camber to port (typically in the same range as maximum working camber to starboard <NUM>).

To fold the wingsail <NUM> into its stowed configuration the second aerofoil element <NUM> is rotated around its primary axis <NUM> to a maximum rotational position. The maximum rotational position may in some examples be where the minimum stroke of a ram (or another linear actuator) is reached. This is shown as configuration <NUM>. The second aerofoil element <NUM> then rotates in relation to the first aerofoil element <NUM><NUM> about its secondary axis <NUM> by way of approximately <NUM> degrees to create a tightly packed configuration <NUM>. This tightly packed configuration <NUM> preferably minimises the combined length <NUM> and thickness <NUM> of both the first aerofoil element <NUM> and second aerofoil element <NUM> and results in an orientation of the second aerofoil element <NUM> in relation to the first aerofoil element <NUM> which is reversed from its feathered configuration <NUM>. The centreline of the first aerofoil element <NUM> and second aerofoil element <NUM> may sit in parallel in this configuration or up to approximately <NUM>° and the second aerofoil element <NUM> preferably sits within the length of the first aerofoil element <NUM>. This rotation around the secondary axis <NUM> may be controlled either by rotary actuator or secondary ram arrangement connected between the linking member <NUM> and the second aerofoil element <NUM> and preferably be a hydraulic linear ram or hydraulic rotary actuator. In the case of a hydraulic linear ram being used this forms a double ram arrangement in series which allows the second aerofoil element <NUM> to rotate in relation to first aerofoil element <NUM> by an angle greater than <NUM> degrees. The same angle is achieved if a rotary actuator is used.

When the second aerofoil element <NUM> folding articulation routine is complete (as described above and in <FIG>), wingsail <NUM> is ready to be folded down to deck to prepare for port operations. <FIG> shows this process. The base <NUM> of wingsail <NUM> is connected to a pivotable plate <NUM> which is connected to the base structure <NUM>, preferably a steel fabricated structure of welded plates and flanges, by way of a hinged arrangement. This arrangement allows wingsail <NUM> to rotate about a horizontal axis <NUM> to transition between an upright condensed configuration <NUM> (upright) and a stowed configuration <NUM> (horizontal). Hydraulic cabling and other low voltage electronic cabling may be passed from inside the base <NUM> through an opening in pivotable plate <NUM> and up into wingsail <NUM>.

Wingsail <NUM> in its upright condensed configuration <NUM> is lowered to its stowed configuration <NUM> by two linear actuators, preferably hydraulic rams <NUM>, which take the load of the weight of the wingsail <NUM> as tension. One single ram is capable of raising and lowering the wingsail <NUM> and the second of these two rams reduces the load in one single ram and provides redundancy in the system in case of failure of one of the rams or its systems. The same process is repeated in reverse to transfer wingsail <NUM> from its stowed configuration to its upright and working configuration.

In its stowed configuration wingsail <NUM> sits horizontally and ideally sits parallel to the deck of the vessel. The tip of wingsail <NUM> is supported by a deck support and a locking pin fixes this in place. On a bulk carrier vessel, the wing base will preferably be fitted on the side deck between hatch cover slides and will be lowered to a stowed configuration above hatch covers. The hatch covers will be able to slide underneath the stowed wingsail <NUM> to allow port operations to be uninterrupted. Wingsail <NUM> will preferably sit at least two metres above the deck to allow for passageway underneath. For bulk carrier installations and other installations where deck space is restricted the rams may be fitted to the underside of the pivotable plate <NUM> and sit in a cavity within the deck. Where deck space is not restricted the rams will be positioned above the deck as shown in <FIG>.

The construction of wingsail <NUM> according to some examples is simple and robust and its simplicity minimises the total cost of the wingsail <NUM> allowing the fuel saved as a result of the wing to 'pay back' the wing in a shorter time period. <FIG> shows the bare structure <NUM> of the wingsail <NUM> and the first aerofoil element fairing <NUM> and second aerofoil element fairing <NUM> removed for clarity. The main structure may comprise a main spar <NUM> which may be connected to a first element base structure <NUM> and first element end structure <NUM> and may also be connected to a number of structural ribs <NUM> to provide support to the first aerofoil aerodynamic fairing <NUM>. In another embodiment of the invention the structure may not include structural ribs <NUM>. The main spar <NUM> protrudes beneath the first aerofoil element <NUM> and first element base structure <NUM> and attaches to the top of a bearing arrangement <NUM>, preferably a hydraulic driven slew gear bearing, which allows wingsail <NUM> to rotate about <NUM> degrees relative to the base and the vessel. The loads are transferred and spread out evenly to the bearing to minimise localised stress concentrations which may impinge the rotation of the device. These loads may be spread out and transferred though triangular flanges preferably welded to the main spar <NUM> and a plate which is subsequently bolted to the top of the bearing arrangement. These triangular flanges may be comprised of steel plate. Other methods for transferring loads from the main spar <NUM> and the bearing may be used.

According to some examples, the underside of the bearing arrangement <NUM> is bolted to the pivotable plate <NUM> which is preferably a steel plate with structural reinforcement flanges. Pivotable plate <NUM> is connected to the wingsail base <NUM> by way of a hinged arrangement with a horizontal axis <NUM> along one edge of the pivotable plate <NUM>, and by a locking pin arrangement on the other edge of the pivotable plate <NUM>. The base <NUM> is preferably comprised of a steel fabricated structure of welded steel plate and welded steel flange sections to transmit the forces and moments from wingsail <NUM> to the deck and ships existing and modified structure. The base <NUM> is preferably bolted or welded to the deck and loads transferred to the underlying structure.

According to some examples, the first element base structure <NUM>, first element end structure <NUM> and structural ribs <NUM> may be comprised preferably of fabricated steel plate sections welded together to form a support for the first element fairing <NUM>. These may also be comprised of aluminium or composite. The first element fairing is connected to the base support structure <NUM> and end support structure <NUM>. This fairing may be joined by mechanical fastenings or chemically bonded. The first aerofoil aerodynamic fairing <NUM> and second aerofoil element aerodynamic fairing <NUM> may preferably be comprised of composite but may be comprised of steel or aluminium curved plate.

The main spar <NUM> may be comprised of steel fabricated box section or I-beam section or other construction methods to provide a structurally efficient shape in bending and torsion. The main spar <NUM> must transfer the total accumulation of loads generated by wingsail <NUM> to the base of the wing.

The first aerofoil element <NUM> may be connected to a linking member <NUM> which is rotatable relative to the first aerofoil element <NUM> about the primary axis <NUM>. The first aerofoil element <NUM> may comprise a minimum of two bearings to connect it to the linking member <NUM> which is able to rotate. Preferably the first aerofoil element may comprise a double shear plane arrangement <NUM>, <NUM> as depicted in <FIG>.

<FIG> presents a structural view of wingsail <NUM> with linking member <NUM> highlighted to indicate how linking member <NUM> fits within the remainder of the wingsail structure. <FIG> also presents a scaled-up view of the first element base structure <NUM>, second element base structure <NUM> and linking member <NUM> to depict how these parts link and rotate together and form the double shear pin arrangement. Although the following detail is described for the base of the wing the mechanism is assumed to be similar for the end of the wing and may be found in any other location along the primary axis <NUM>.

According to some examples, the first element structure (which may be comprised of first element base structure <NUM>, first element end structure <NUM> and structural ribs <NUM>) may house a minimum of two bearings but preferably comprise more than two bearings. <FIG> provides an example of a double bearing assembly embedded into the first element base structure although this assembly may be found at any point within the structure of the first aerofoil element <NUM> along the primary axis <NUM>, and in this example is repeated within the first element end structure <NUM> but not shown in detail.

The bearing assembly depicted in <FIG> may comprise top bearing 796a and bottom bearing 766b and these bearings may be spaced apart with an opening between each to house the bottom bar <NUM>. The top bearing 766a and bottom bearing 766b can be mechanically connected or bonded to the linking members torsional structural member <NUM> to allow rotation of the linking member <NUM> in relation to the first element base structure <NUM>. The use of two bearings 796a and 796b creates a double shear plane arrangement which provides the joint with greater stability and restricts the linking member <NUM> from rotating transversely in relation to the first element base structure <NUM>. A bearing 796c may also be provided for rotation of the second aerofoil element relative to linking member <NUM>. In another embodiment of the invention a single bearing is used to connect the linking member <NUM> to the first element base structure <NUM>. If a single bearing is used the bearing may be a self-aligning bearing and be able to rotate with an off axis shaft, i.e. when the top of the wingsail <NUM> deflects and rotates at a greater angle than the bottom of the wingsail <NUM> due to the deflection under load of the wingsails structure, the bearing is able to self-align to maintain movement between the linking member <NUM> and the first element base structure <NUM> about the primary axis <NUM>.

Bearings 796a and 796b may be cylindrical or self-aligning and must allow the linking member to freely rotate about the primary axis <NUM> whilst providing support for the load of the second aerofoil element <NUM>. These bearings may transfer all the load from the linking member <NUM> to the first element base structure <NUM> and first element end structure <NUM>, including the self-weight of the linking member <NUM> and second aerofoil element <NUM>. Bearings may also be housed within structural ribs <NUM> or any other structure within the first aerofoil element <NUM>. Adversely the structural ribs may contain space along the primary axis <NUM> to allow the torsional spar <NUM> of the linking member <NUM> to rotate freely without contact with structural ribs <NUM>.

The linking member <NUM> rotates in relation to first aerofoil element <NUM> and may be connected to the second aerofoil element <NUM> via a bearing arrangement housed within the structure of the second aerofoil element <NUM> acting along the secondary axis <NUM>. This bearing arrangement may be connected to a torsional structural member <NUM> which connects the top and base of the second aerofoil element <NUM> to withstand torsional forces and moments acting between the top and the base of the second aerofoil element <NUM> and ensures that the aerofoil element does not twist adversely.

The connection of linking member <NUM> to second aerofoil element <NUM> may be via two or more bearings fixed to torsional structural member <NUM> which may be fixed to a second element base structure <NUM> and second element end structure <NUM>. This bearing arrangement allows the second aerofoil element <NUM> to be rotatable relative to the linking member about the secondary axis <NUM>. This torsional structural member <NUM> withstands torsional forces and moments between the top and bottom of the second aerofoil element <NUM> and minimises deflection of the top portion of this element in relation to the bottom. This provides structural rigidity and avoids damage through excessive bending of the aerofoil element.

In a similar manner to the first aerofoil element aerodynamic fairings <NUM>, the second aerofoil element aerodynamic fairings <NUM> may connect to the structure of the second aerofoil element <NUM>. The second element aerodynamic fairings <NUM> may connect to the structure of the second aerofoil element <NUM> by mechanical fixing or bonding to the second element base structure <NUM>, second element end structure <NUM> and structural ribs <NUM> of the second aerofoil element <NUM>, or connection to any combination of these parts. These connections preferably comprise mechanical fastenings or bonding and the second aerofoil element fairing <NUM> is preferably comprised of composite but may be comprised of steel or aluminium plate.

The first aerofoil element fairing <NUM> and second element faring <NUM> may preferably be constructed in two half sections and bonded or mechanically fastened together or may be comprised of smaller plates bonded or mechanically fastened to the structural ribs <NUM> or made of smaller half sections. The structure of the second aerofoil element <NUM> may be comprised of steel fabricated plates or may be comprised of composite or aluminium.

All metallic structures of wingsail <NUM> may be painted with anti-corrosive paint to reduce corrosion during use within highly corrosive salty environments.

The base and end support structure for the first and second aerofoil elements (<NUM>, <NUM>, <NUM> and <NUM>) may comprise a base and end plate, fitted to improve the aerodynamic performance of the device by reducing vortex shedding as a result of the generation of lift.

<FIG> shows a cross section of an example wingsail <NUM> comprising multiple outlets 809a, 809b, 809c, 809d, 809e, 809f, <NUM>, and <NUM> in the leading (front) aerofoil. Wingsail <NUM> may operate similarly to wingsail <NUM>, although instead of a single outlet (outlet <NUM> in aerofoil <NUM>) wingsail <NUM> has multiple outlets in the front aerofoil. Wingsail <NUM> may comprise a pressurized cavity <NUM>.

The multiple outlets 809a, 809b, 809c, 809d, 809e, 809f, <NUM>, and <NUM> may be provided at a particular height of wingsail <NUM>, for example at the base of wingsail <NUM> or at the top of wingsail <NUM>. In some examples, the outlets are positioned at regular intervals between the base of the wingsail <NUM> and the top of the wingsail <NUM>. Wingsail <NUM> may also comprise one or more inlets in the front aerofoil (not shown in <FIG> for clarity). In some examples, the one or more inlets may be at a different height to the outlets. The multiple air outlets 809a, 809b, 809c, 809d, 809e, 809f, <NUM>, and <NUM> can act in a similar way to the single air outlet <NUM> of wingsail <NUM> in that the multilple outlets provide a high energy stream of air onto the surface of the wing to re-energise the boundary layer thus increasing the angle of attack of the wingsail <NUM> achievable before stall and also increasing achievable lift coefficient of wingsail <NUM>. The multiple air outlets 809a, 809b, 809c, 809d, 809e, 809f, <NUM>, and <NUM> shall be configured so that air flow is directed to the high-pressure side and not the low-pressure side of the aerofoil by closing the low-pressure side air outlets. In some examples, the air outlets on the first aerofoil element shown in <FIG> will be situated towards the back half of the aerofoil element towards the trailing edge. In another example, one or more of these air outlets may be situated in the front half of the leading (front) aerofoil element.

Wingsail <NUM> may in some examples comprise a wingsail "unit" that can be repeated to provide a modular wingsail such as wingsail <NUM>.

Although <NUM> outlets are shown in the leading aerofoil of wingsail <NUM>, it will be understood that in other examples more or fewer outlets may be used.

<FIG> shows a cross section of an example wingsail <NUM> comprising multiple outlets 909a, 909b, 909c, 909d, 809e, 909f, <NUM>, and <NUM>. Wingsail <NUM> may operate similarly to wingsail <NUM>, although wingsail <NUM> has multiple outlets 984a, 984b, 984c, 984d, 984e, 984f, <NUM>, <NUM> in a trailing aerofoil. Wingsail <NUM> may comprise a pressurized cavity <NUM>.

The multiple outlets 984a, 984b, 984c, 984d, 984e, 984f, <NUM>, <NUM> may be provided at a particular height of wingsail <NUM>, for example at the base of wingsail <NUM> or at the top of wingsail <NUM>. In some examples, the outlets are positioned at regular intervals between the base of the wingsail <NUM> and the top of the wingsail <NUM>. Wingsail <NUM> may also comprise one or more inlets in the front aerofoil (not shown in <FIG> for clarity). In some examples, the one or more inlets may be at a different height to the outlets. The multiple air outlets 909a, 909b, 909c, 909d, 909e, 909f, <NUM>, and <NUM> can act in a similar way to the single air outlet <NUM> of wingsail <NUM> in that the multilple outlets provide a high energy stream of air onto the surface of the wing to re-energise the boundary layer thus increasing the angle of attack of the winsgail <NUM> achievable before stall and also increasing achievable lift coefficient of wingsail <NUM>. The multiple air outlets 909a, 909b, 909c, 909d, 909e, 909f, <NUM>, and <NUM> shall be configured so that air flow is directed to the high-pressure side and not the low-pressure side of the aerofoil by closing the low pressure side air outlets. In some examples, the air outlets on the first aerofoil element shown in <FIG> will be situated towards the back half of the aerofoil element towards the trailing edge. In another example, one or more of these air outlets may be situated in the front half of the leading (front) aerofoil element.

Although <NUM> outlets are shown in the leading and trailing aerofoils of wingsail <NUM>, it will be understood that in other examples more or fewer outlets may be used.

<FIG> shows wingsail <NUM> in an upright configuration.

<FIG> shows wingsail <NUM> in a folded and stowed configuration wherein back (trailing) aerofoil <NUM> is rotated relative to the front (leading) airfoil <NUM> so that the chord lines of each aerofoil are substantially at <NUM> degrees to one another, and both aerofoils <NUM> and <NUM> are rotated from the base of the wingsail to a horizontal position to form a stowed configuration as shown in <FIG> controlled by one or two articulating rams <NUM> at the base of the wingsail. The stowed configuration in <FIG> is such that the in some examples wingsail <NUM> fits in the side channel between ships hatches and the ships side, and that the ships hatches are able to slide to an open position underneath the leading (first) aerofoil <NUM> or fold next to the leading (first) aerofoil <NUM> so that wingsail <NUM> does not restrict the movement of the ships hatches. In the stowed configuration shown in <FIG> the trailing (second) aerofoil <NUM> is rotated relative to the first aerofoil element by substantially <NUM> degrees, and in some examples, this allows the second aerofoil element to stay within the limits of the ships beam. The chord length of the second aerofoil element <NUM> is dimensioned so that it is capable of folding to this stowed configuration and rest above the side deck of the ship, and the height of the first aerofoil element <NUM> above the side deck of the ship is dimensioned to allow the ships hatch cover to slide underneath. Incorporating boundary layer flow control into the design of wingsail <NUM> allows a smaller device to be fitted to the ship whilst still producing similar thrust to a larger device, wherein this smaller device is capable of producing a stowed configuration as described above to minimise impact on port operations and loading and unloading of the vessel, wherein ships hatches need to articulate from closed to open and cargo is removed from the ships holds and may travel over the wingsail <NUM> in its stowed configuration shown in <FIG>. To provide a certain amount of thrust, a smaller of planform area of a wingsail using the boundary layer flow control capabilities is required than if the wingsail did not have boundary layer flow control. In other words, wingsails described herein can produce more thrust with less total planform area (total planform area can be considered to be the combined cross-sectional area of both aerofoils along the chord line of the respective aerofoil from the base to the tip of the respective aerofoil) than previous wingsails, due to the boundary layer flow control of the wingsails described herein. With the smaller planform area, in some examples, the wingsails described herein can achieve a compact stowed configuration that fits in the side channel between ships hatches and the ships side while producing required thrust for a ship.

<FIG> shows wingsail <NUM> in a stowed configuration relative to a marine vessel (ship). As can be seen, wingsail <NUM> in a stowed configuration fits in the side channel between the ships hatches and the ships side allowing the ships hatches to slide underneath.

<FIG> shows a base structure for an energy saving device for a marine vessel. The energy saving device may comprise a wind propulsion system, (such as a wingsail as described herein, a flettner rotor, a turbosail, a kite) or for an energy generation device such as a wind turbine (having a vertical or a horizontal axis). The base is designed to be fixed to the deck of a vessel (e.g., any vessel as described herein, a bulk carrier, a tanker, a container vessel, a ro-ro vessel, a LNG carrier, a ferry, a cruise ship etc.) and comprises three or more vertical pillars <NUM>. Each of vertical pillars <NUM> may have a cylindrical cross section, an I beam cross section, square cross section or other cross section. Each vertical pillar <NUM> may be fixed to the deck of a marine vessel via flange and bolting pattern or any other method. Pillars <NUM> hold a structural platform <NUM> of the device to a height of at least <NUM> above the deck of a to allow full working clearance underneath to allow normal operation of vessel.

A linear actuator <NUM> for raising and lowering wind propulsion device <NUM> may be situated at the deck or may be situated on platform <NUM> above the pillars <NUM>, as shown in <FIG>. Linear actuator <NUM> may comprise one or more raising rams, for example. By situating linear actuator on platform <NUM> above the deck, the probability of accidents involving linear actuator <NUM> and crew members working on the deck is reduced.

By raising wind propulsion device above deck height, wind propulsion device <NUM> has less effect on deck layout (as deck space is saved). According to some examples, pillars <NUM> are at least <NUM> tall, to allow operations to be performed by crew under platform <NUM>. According to some examples, pillar <NUM> are less then <NUM> tall, to reduce moment arm length between the deck and platform <NUM> and therefore reduce stress on the fixings of pillars <NUM> to the deck of the marine vessel when wind force applies a moment to the device above the base and/or dynamic loading from the rolling or pitching moment of the marine vessel.

<FIG> shows a further view of the base structure of <FIG>. <FIG> shows an example base structure having three pillars <NUM> rather than four pillars as shown in <FIG>.

<FIG> compare air flow differences between example wingsails having inlets and wingails not having inlets, and also compare different inlet positioning in an example wingsail.

<FIG> shows a wingsail at a <NUM> degree angle of attack 3210a to air flow <NUM>. In this image no aspiration (air inlet or pressurised outlet) is present. The flow stays attached until it reaches <NUM>% of the chord length of a first aerofoil element 3203a of the wingsail, at which point the flow separates into a turbulent region and the wingsail is described as stalled. The flow does not reach second aerofoil element 3203b. This creates little lift and also causes drag.

<FIG> shows a wingsail again at a <NUM> degree angle of attack 3210b to flow <NUM>. The example wingsail of <FIG> incorporates aspiration by an air inlet 3207b towards the back quarter of the chord length of first aerofoil element 3203b, and a pressurised air outlet at the trailing edge of the first element. The pressurised inlet 3207b is located near the location of flow separation and 'sucks' in the flow at this point, removing the turbulent boundary layer and keeping the flow attached along aerofoil element 3203b and aerofoil element 3205b. This means that at an angle 3210b which would otherwise be stalled, the wingsail is still working well as an aerofoil and able to achieve greater lift due to the greater pressure differential between the high (H) and low (L) pressure regions due to the high angle of attack.

<FIG> shows a wingsail at <NUM> degrees angle of attack 3210c to flow <NUM>. In this example no aspiration (air inlet or pressurised outlet) is present. The flow stays attached only until it reaches the first <NUM>% of the chord length of the first element. In comparison on to <FIG> the separation occurs closer to the leading edge of the first element than its trailing edge due to the greater angle of attack 3210c of the wingsail. Again, this configuration is stalled and provides little lift and significant drag and should be avoided.

<FIG> shows a wingsail again at a <NUM> degree angle of attack 3210d to flow <NUM>. The wingsail of <FIG> incorporates aspiration, having an air inlet towards (within) the front quarter of the chord length of the first aerofoil element 3203d, and a pressurised air outlet at the trailing edge of the first aerofoil element 3203d. The pressurised inlet <NUM> in this case is located near the location of flow separation which in this case occurs much closer to the leading edge than the trailing edge and 'sucks' in the flow at this point, removing the turbulent boundary layer and keeping the flow attached. As the air inlet 3207d is located much closer to the leading edge of the first element 3203d, this means that a greater angle of attack 3210d can be achieved for the whole wingsail in comparison to the winsail of <FIG>, thus increasing the pressure differential between the high (H) and low (L) pressurised regions and creating a greater amount of thrust and reduction in fuel consumption of the vessel.

It will of course be understood that the examples described are by way of example only and are not intended to limit the scope of the invention which is defined by the appended claims. The term "wingsail" does not place any limitations on the size or application of the wingsail. The term "marine vessel" does not place any limitations on the size or application of the marine vessel. The marine vessel and/or wingsail may be provided at different scales.

It will of course be understood that the examples described are by way of example only and are not intended to limit the scope of the invention which is defined by the appended claims. It will be also understood that any of the aforementioned examples may be combined.

Claim 1:
A wingsail (<NUM>) comprising:
a first aerofoil (<NUM>) having a leading edge (103a) at a front of the wingsail (<NUM>) and a trailing edge (103b) behind the leading edge (103a); and
a second aerofoil (<NUM>) having a leading edge (105a) and a trailing edge (105b), the leading edge (105a) of the second aerofoil (<NUM>) being closer than the trailing edge (105b) of the second aerofoil (<NUM>) to a point of maximum cross-sectional width (105c) of the second aerofoil;
wherein the wingsail (<NUM>) is configured such that the leading edge (105a) of the second aerofoil (<NUM>) can be positioned behind the trailing edge (103b) of the first aerofoil (<NUM>);
characterized in that the first aerofoil (<NUM>) comprises:
an air inlet (<NUM>) comprising a port air inlet (107p) positioned on a port side of the first aerofoil (<NUM>) and a starboard air inlet (<NUM>) positioned on a starboard side of the first aerofoil;
an air outlet (<NUM>);
a channel (<NUM>) inside the first aerofoil (<NUM>) connecting the air inlet and the air outlet (<NUM>);
wherein air flow from the air inlet (<NUM>) is directed by the channel (<NUM>) to the air outlet (<NUM>) and the air flow from the air outlet (<NUM>) is directed out of the air outlet (<NUM>) towards the leading edge (105a) of the second aerofoil (<NUM>).