Method for landing a kite system, and kite system

Abstract

The invention relates to a method for landing a kite system (23). The kite system (23) comprises a kite (14) and a gondola (25), and the kite (14) is held on the gondola (25) via a line tree (24). The gondola (25) is held on an attachment point (16, 44) which is installed in the ground via a towing rope (15) during a normal operation of the kite system (23). A sail surface of the kite (14) is stretched by a first sub-kite (40) and a second sub-kite (41). A connection (36) lying within the sail surface between the first sub-kite (40) and the second sub-kite (41) is separated such that the kite (41) transitions into another aerodynamic state and descends to the ground together with the gondola (25). The invention also relates to a kite system.

Description

[0001] Procedure for landing a kite system and kite system

[0002] The invention relates to a method for landing a kite system. The kite system comprises a kite and a gondola, the kite being attached to the gondola by a line boom. During normal operation of the kite system, the gondola is attached to a ground-based anchor point by a tow rope. The invention also relates to a kite system.

[0003] By appropriately adjusting the aerodynamic properties, the kite can be moved along flight paths that are substantially perpendicular to the towing rope, thus exerting a pulling force on the towing rope.

[0004] When operating a kite of this type, safety mechanisms are desirable which allow control of the kite even when normal operation is not possible. For example, an operating condition could arise in which the controls fail and the kite can no longer be controlled precisely. If the kite exerts a high tensile force on the towing cable in this condition, it may not be possible to reel in the towing cable. A failure of the towing cable winch can also make it impossible to reel in the kite. If the towing cable breaks, it is known from EP 3 456 630 A1 to bridge the break point with a safety device. As the safety device needs a certain distance to absorb the high forces, part of the flying height that can be used during normal operation is lost.

[0005] The invention is based on the object of presenting a method and a kite system such that the kite system can be landed reliably and safely even after leaving normal operation. Based on the cited prior art, the object is achieved by the features of the independent claims. Advantageous embodiments are specified in the subclaims.

[0006] In the method according to the invention, a sail surface of the kite is spanned by a first sub-kite and a second sub-kite. A connection between the first sub-kite and the second sub-kite in the sail surface is severed, so that the kite transitions to a different aerodynamic state and descends to the ground with the gondola.

[0007] The invention recognizes that severing a connection in the sail surface between the first and second kite parts opens up a way to quickly and reliably change the aerodynamic state of the kite so that the pulling force decreases. After severing the connection, an aerodynamic state arises in which the lift force exerted by the kite is no longer sufficient to keep the kite system in the air. The kite and the connected gondola sink to the ground, with the kite acting as a parachute.

[0008] In particular, the kite can act as a brake parachute in this state, so that when the rope is heavily loaded the tension in the rope is released without the rope experiencing a shock-like release. Shock-like releases are undesirable because they can cause the pulleys to jump off the pulleys at the ground station. If the pulley is prevented from jumping off, the pulley can continue to be retrieved despite the emergency landing system being triggered. The procedure is preferably carried out in such a way that after activation the kite goes into a state rotating around the pulley axis, so that the kite sinks to the ground with little load but with the pulley taut.

[0009] The sail surface is the area of ​​the kite along which the air flows when the kite is moved along flight paths. The sail surface can comprise an inner surface facing the nacelle and an outer surface facing away from the nacelle. The inner surface and the outer surface can be spaced apart from each other and form an airfoil. The connection can extend in the direction of the airfoil so that before separation both the first part of the kite and the second part of the kite form a complete airfoil. The direction of the airfoil is referred to as the fore and aft direction of the kite. Viewed in the transverse direction, the first part of the kite can be arranged next to the second part of the kite.

[0010] A pivot point is ground-based if it is not lifted from the earth's surface by the kite's pulling force. A ground-based pivot point can be permanently attached to the ground. Other possible locations include, for example, a ship, a floating pontoon, or a mobile system on land.

[0011] During normal operation of the system, a connection is formed in the sail area between the first partial kite and the second partial kite. The connection can form a continuous transition between the first partial kite and the second partial kite. The connection can be designed such that the sail area and / or the airfoil profile have no interruption in the area of ​​the connection. The method can be carried out in such a way that the first partial kite and the second partial kite are completely separated from one another, so that after the separation there is no longer any connection between the first and the second partial kite within the sail area. In another embodiment, the first partial kite and the second partial kite are partially separated from one another, so that even after the separation there is still a connection between the first partial kite and the second partial kite in the sail area.

[0012] The first and second kites can be the same size, so the split occurs in the middle of the kite. It's also possible to have two different sized kites, so the kite splits off-center.

[0013] The kite can comprise more than two sub-kites. According to the invention, two of the kites involved span a sail area of ​​the kite. The sub-kites can be arranged next to one another in the transverse direction of the kite, so that a middle sub-kite is enclosed between two sub-kites adjacent in the transverse direction. A connection can be formed between any two adjacent sub-kites, which connection is severed when the method according to the invention is carried out. By splitting the kite into more than two sub-kites, even larger kites can be reliably landed.

[0014] The separation of the sub-kites can be triggered by a trigger element. The kite system can be set up so that the trigger element is triggered automatically if normal operation of the kite system cannot be maintained. The trigger element can be triggered as a result of an exceptional event. The exceptional event, as a result of which normal operation cannot be maintained, can be, for example, a line on the line boom or the towing rope breaking or an overload acting on a line on the line boom or the towing rope. The exceptional event can also consist of a control unit detecting a condition in which one or more operating parameters of the kite system are outside the normal range.

[0015] In addition to or as an alternative to automatic activation, the triggering element can be triggered by external intervention. The intervention can occur, for example, if an operator observes that the kite system is entering an irregular state. The intervention can consist, for example, of the operator making an input or activating a switch.

[0016] The trigger signal can be transmitted to the trigger element mechanically. For example, the trigger element can be mechanically coupled to a rope, so that the trigger element triggers if the rope breaks or is overloaded. The trigger signal can also be a control signal transmitted electronically to the trigger element. In particular, the control signal can be transmitted to the trigger element via a cable or a radio link.

[0017] The kite can have a predetermined separation point at which the connection between the first part of the kite and the second part of the kite is severed. The predetermined separation point can be provided with a safety device so that the connection between the first part of the kite and the second part of the kite is maintained as long as the safety device is active. The predetermined separation point can be designed such that the connection between the first part of the kite and the second part of the kite is severed under the influence of the aerodynamic forces acting on the sail surface when the safety device is no longer active. The predetermined separation point can comprise a zipper by means of which the first part of the kite and the second part of the kite are connected to one another. The zipper can be held in the closed state by the safety device.By releasing the locking device, a section of the zipper can be released, allowing the zipper to open lengthwise. Opening of the zipper can continue in one direction or in both directions starting from the released section. In one embodiment, the zipper is designed such that a number of teeth are missing or not engaged in the area where the locking device is located.

[0018] In other variants, the partial kites can be connected at the intended separation point with a material that is less tear-resistant than the adjacent material of the sail surface, so that the material at the intended separation point tears after the safety device is released. A seam that separates lengthwise after the safety device is released is also possible. In another embodiment, a fuse extends along the intended separation point and is ignited by the release element. The fuse can weaken the kite material at the intended separation point to such an extent that it tears.

[0019] The intended separation point can be designed in such a way that it is separated after the safety device has been released under the influence of the aerodynamic forces occurring during normal operation of the kite system.

[0020] It is also possible to break the connection by placing the kite in a position where higher aerodynamic forces act at the intended separation point than during normal operation of the kite system. The procedure can be carried out in such a way that the higher aerodynamic forces directly lead to a separation at the intended separation point. Alternatively, the separation of the intended separation point can be achieved by the release of a safety device and the combination of the higher aerodynamic forces.

[0021] The line boom between the gondola and the kite can comprise a plurality of lines via which the pulling forces are transferred from the kite to the gondola. The line boom can comprise lines designed as active control lines whose free length between the gondola and the kite can be adjusted. By operating the active control lines, the kite can be controlled so that it moves along the desired flight paths. The line boom can comprise lines designed as fixed lines with which sections of the kite are kept at a fixed distance from the gondola. The line boom can comprise lines designed as passive control lines which extend between a first pivot point on the kite and a second pivot point on the kite and which are deflected between the pivot points on a pulley connected to the gondola.With such passive control lines, the distance between the nacelle and the first pivot point, as well as the distance between the nacelle and the second pivot point, can change, with the sum of the two distances remaining constant. The fixed lines can be arranged in a central section of the kite with respect to the transverse direction. The control lines can be arranged in a peripheral section of the kite. The passive control lines can be arranged in a section of the kite with respect to the transverse direction that lies between the central section and the peripheral section.

[0022] The kite system can be set up so that when the release element is triggered, a line on the line boom is severed. To enable cutting triggered by the release element, the line or a holding element connected to the line can be provided with a pyrocutter or a compressed air shackle, for example. When there is no longer any pulling force on the relevant section of the kite, the section moves away from the gondola. The relevant movement of the kite can be used to release the safety device. For example, a safety line can extend from the gondola over the relevant section of the kite to the safety device, so that the movement in the kite exerts a pulling force on the safety device. The line that is severed by the release element can be a fixed line.

[0023] The kite can be designed in such a way that a cavity surrounded by an outer skin is enclosed between the outer surface and the inner surface of the kite. During normal operation of the kite system, an overpressure can be present in the cavity which is, for example, 50 mbar to 1000 mbar, preferably 100 mbar to 500 mbar higher than the ambient pressure. The overpressure can be fed by the air flow that flows along the sail surface when the kite moves along flight paths. The kite can have an inlet opening arranged between the outer surface and the inner surface of the kite. In particular, the inlet opening can be arranged in an end face of the kite that points in the direction of movement.

[0024] By separating the connection between the first and second kites, an opening can be created in the kite's outer skin, allowing excess pressure inside the kite to escape. The release of excess pressure can change the kite's aerodynamic state, reducing the pulling force acting toward the gondola.

[0025] The invention also relates to a kite system with a kite and a gondola. The kite is held to the gondola by a line tree. A sail area of ​​the kite is stretched by a first partial kite and a second partial kite. A connection between the first partial kite and the second partial kite is formed in the sail area. The kite system comprises a release element for separating the connection so that, after the connection is separated, the kite changes into a different aerodynamic state and sinks to the ground with the gondola.

[0026] The kite system can comprise a towing rope that extends between the gondola and a ground-based pivot point. The pivot point can be a part of a component of the kite system that is firmly connected to the ground. The kite system can be an element of a device for generating electrical energy. The device can comprise a generator that is driven by a towing rope winch. It is also possible for the kite system to be connected to a pivot point of a ship so that the kite system can be used to generate propulsion for the ship. A pivot point of a ship is a ground-based pivot point within the meaning of the invention.

[0027] The kite system can be developed with further features that are described in connection with the method according to the invention. The method can be developed with further features that are described in connection with the kite system according to the invention.

[0028] The invention is described below by way of example with reference to the accompanying drawings using advantageous embodiments. They show:

[0029] Fig. 1: a schematic representation of a device according to the invention;

[0030] Fig. 2: a schematic representation of an operating state of the device from Fig. 1;

[0031] Fig. 3: a kite system according to the invention; Fig. 4-6: details of the kite system from Fig. 3 in an enlarged view;

[0032] Fig. 7-10: different states of an inventive

[0033] Kite systems ;

[0034] Fig. 11: an alternative embodiment of a device according to the invention.

[0035] A device according to the invention for generating electrical energy comprises, as shown in Fig. 1, a kite system 23 according to the invention, which is connected to a traction cable winch 16 via a traction cable 15. The kite system 23 comprises a kite 14, which is connected to a gondola 25 via a line boom 24.

[0036] Coupled to the traction cable winch 16 is an electric power machine 17 which operates as a generator in a first operating state and as a motor in a second operating state. The power machine is connected to a public transmission network 19 via an electrical power train 18 which comprises a converter and a transformer, so that either electrical energy generated by the power machine 17 can be fed into the transmission network 19 or the power machine 17 can be operated as a motor with electrical energy taken from the transmission network 19. The device comprises a control unit 20 which is designed to control the interaction of the components of the device.

[0037] The control unit 20 includes an antenna 21, allowing control signals to be exchanged with the gondola 25 via a radio link 22. In particular, the control unit 20 sends control signals to the gondola 25 to control the flight path of the kite 14. Using the control signals, the length of the control lines of the line boom 24 is changed, thereby influencing the flight direction of the kite 14.

[0038] In the embodiment according to Fig. 2, the kite 14 is guided along a horizontal figure eight oriented substantially transversely to the wind direction W. As the kite 14 follows the flight path, a tensile force is exerted on the towing cable 15, which is used to drive the power machine 17 via the towing cable winch 16. With the power machine 17 operated as a generator in this operating state, the mechanical energy is converted into electrical energy and fed into the public transmission grid 19 via the power train 18. It is also possible to store some of the generated energy in electrical form in an energy storage device in the power train 18. In this way, electrical energy can be generated until the length of the towing cable 15 is exhausted and the towing cable 15 is completely paid out by the towing cable winch 16.The traction cable 15 is then retrieved using the power machine 17 operated as a motor before electrical energy can be generated again.

[0039] The line boom 24 of the kite system 23 according to the invention comprises, according to Fig. 3, active control lines 26, passive control lines 27 and fixed lines 28, which are each attached to the gondola 25 and which branch out from nodes 29 into a plurality of ends attached to the kite 14. The fixed lines 28 extend from an end which is firmly connected to the gondola 25 to a central section of the kite 14. The active control lines 26, whose length is adjustable, extend from the gondola 25 to two peripheral sections of the kite 14. The passive control lines 27, which are deflected on the gondola 25 via rollers 30, are attached to the kite 14 between the fixed lines 28 and the active control lines 26. By adjusting the length of the active control lines 26, the direction of movement of the kite 14 can be controlled.When adjusting the active control lines 26, the passive control lines 27 are guided over the rollers 30, whereby the length of the passive control lines 27 from the kite 14 over the rollers 30 back to the kite 14 remains unchanged.

[0040] The kite 14 forms an airfoil profile which extends longitudinally from an end face 31 (visible in Fig. 3) over an outer surface 32 and an inner surface 33 to a rear end not visible in Fig. 3. A cavity is formed inside the kite 14 which is under excess pressure during normal operation of the kite system. The kite 14 comprises openings 34 formed in the end face 31 through which air can enter the interior and through which the excess pressure is built up when the kite 14 is in motion.

[0041] A zipper 36 is formed in the outer skin 35 of the kite 14, which extends from the end face 31 over both the outer surface 32 and the inner surface 33 over the length of the wing profile to the rear end of the kite 14. During normal operation of the kite system, the zipper 36 is closed. By opening the zipper 36, the kite 14 can be separated into a first partial kite 40 and a second partial kite 41. According to the invention, the zipper 36 connects the first partial kite 40 and the second partial kite 41 and forms a desired separation point between the first partial kite 40 and the second partial kite 41.

[0042] According to Fig. 5, the zipper 36 comprises a section in which a plurality of teeth have been removed and which is secured with a securing device 37. The securing device 37 extends over the zipper 36 and keeps it closed despite the missing teeth. By pulling on a release line 38, the securing device 37 can be removed, with the result that the zipper 36 can be released lengthwise by forces acting transversely to the zipper 36. Fig. 6 shows a state of the zipper 36 shortly after the removal of the securing device 37, in which the zipper 36 begins to open. By pulling further in the transverse direction, the zipper 36 can be opened over its entire length, whereby the first partial kite 41 and the second partial kite 41 are separated from one another.

[0043] The release line 38 extends according to Fig. 3 from the gondola 25 via a pivot point 39 formed on the kite 14 up to the safety device 37. If the fixed line 28 is released, the central section of the kite 14 moves away from the gondola 25 so that the release line 38 is put under tension, whereby the safety device 37 is released. This has the result that the zipper 36 opens lengthwise so that the kite 14 separates into the first part kite 40 and the second part kite 41. When the zipper 36 opens, an opening is created in the outer skin 35 of the kite 14, through which the excess pressure escapes. In this state, the first partial kite 40 and the second partial kite 41 each act as a parachute on which the gondola 25 sinks to the ground.

[0044] According to Fig. 4, a pyrocutter 42 is arranged in a section of the fixed line 28 adjacent to the gondola 25. The pyrocutter 42 can be triggered by an electrical signal, whereby the fixed line 28 is severed. The pyrocutter 42 forms a triggering element according to the invention. The electrical signal for triggering the pyrocutter 42 can be given by the control unit 20 and generated when an exceptional event occurs as a result of which the kite system can no longer be operated in normal mode. After the fixed line 28 has been severed, the central section of the kite 14 rises and thus moves away from the gondola 25, whereby the triggering line 38 is put under tension. The safety device 37 is removed and the zipper 36 is opened so that the gondola with the two partial kites 40, 41 acting as a parachute sinks to the ground.

[0045] The relevant process is illustrated in Figs. 7-10. Fig. 7 shows the kite system 23 in normal operation. Fig.

[0046] In Fig. 8, the fixed line 28 was severed, so that the central section of the kite 14 rises and the safety device 37 is released from the zipper 36. In Fig. 9, the zipper 36 is partially released. After the zipper 36 is completely released, the two partial kites 40, 41 are separated from each other. As the excess pressure escapes from the interior, the partial kites 40, 41 lose their aerodynamic

[0047] profile and only act as a parachute.

[0048] In Fig. 11, an alternative embodiment of the invention is shown in which the kite system 23 according to the invention is used to generate a propulsion force for a ship 43.

Claims

Patent claims 1. Method for landing a kite system (23) , wherein the kite system (23) comprises a kite (14) and a gondola (25), wherein the kite (14) is held on the gondola (25) via a line boom (24), and wherein the gondola (25) is held on an earth-bound pivot point (16, 44) ) in normal operation of the kite system (23) via a pull rope (15), wherein a sail area of ​​the kite (14) is stretched by a first partial kite (40) and a second partial kite (41) and wherein a connection (36) located in the sail area between the first partial kite (40) and the second partial kite (41) is separated, so that the kite (41) transitions into a different aerodynamic state and descends to the ground with the gondola (25).

2. Method according to claim 1, characterized in that the sail area comprises an inner surface (33) facing the gondola and an outer surface (32) facing away from the gondola, wherein the inner surface (33) and the outer surface (32) are spaced apart from each other and span an airfoil profile.

3. Method according to claim 1 or 2, characterized in that the first partial kite (40) and the second partial kite (41) are completely separated from each other, so that after the separation there is no longer any connection between the first partial kite (40) and the second partial kite (41) within the sail area.

4. Method according to one of claims 1 to 3 characterized in that the separation of the connection (36) is triggered by a release element (42). A method according to claim 4, characterized in that the triggering element (42) is triggered by a control signal from a control unit (20). A method according to any one of claims 1 to 5, characterized in that the kite (14) has a predetermined separation point (36) that forms the connection between the first kite section (40) and the second kite section (41). A method according to claim 6, characterized in that the predetermined separation point comprises a zipper (36) by which the first kite section (40) and the second kite section (41) are connected to each other during normal operation of the kite system (23). A method according to claim 6 or 7, characterized in that the predetermined separation point (36) is secured by a locking device (37) during normal operation of the kite system (23).A method according to any one of claims 6 to 8, characterized in that the zipper (36) is designed such that a number of teeth are missing or not engaged in the area where the locking device (37) is arranged. A method according to any one of claims 4 to 9, characterized in that, after the release element (42) is triggered, the kite (14) transitions into an aerodynamic state in which the forces acting across the connection (36) are higher than during normal operation of the kite system (23). A method according to any one of claims 4 to 10, characterized in that, upon triggering the release element (42), a line (26, 27, 28) of the line boom (24) is cut. Method according to one of claims 1 to 11, characterized in that by separating the connection (36) between the first part kite (40) and the second part kite (41) an opening is created in an outer skin (35) of the kite (14) through which an overpressure located in the interior of the kite (14) escapes. Kite system (23) comprising a kite (14) and a gondola (25) wherein the kite (14) is held on the gondola (25) via a line boom (24), wherein a sail area of ​​the kite (14) is stretched by a first partial kite (40) and a second partial kite (41), and wherein a connection (36) is formed in the sail area between the first partial kite (40) and the second partial kite (41), further comprising a release element (42) for separating the connection (36) so that the kite (41) transitions to a different aerodynamic state after the connection (36) is separated and sinks to the ground with the gondola (25).Kite system according to claim 12, characterized in that the gondola (25) is held in normal operation of the kite system (23) via a pull rope (15) at an earth-bound pivot point (16, 44).

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