Method for landing a kite system and kite system

Abstract

A method for landing a kite system (23), the kite system (23) comprising a kite (14) and a control pod (25). The kite (14) is held on the control pod (25) via a line system (24). The control pod (25) is held on a ground attachment point (16, 44) via a tether (15) during normal operation of the kite system (23). The sail surface of the kite (14) spreads over a first kite section (40) and a second kite section (41). A connection (36) present in the sail surface between the first kite section (40) and the second kite section (41) is separated so that the kite (14) adopts a different aerodynamic state and falls to the ground together with the control pod (25). The invention also relates to a kite system.

Description

background

[0001] The present invention relates to a method for landing a kite system, the kite system comprising a kite and a control pod, the kite being held on the control pod via a line system, in normal operation of the kite system the control pod being held on a ground attachment point via a tether, the present invention also relates to a kite system.

[0002] The kite can be moved by appropriate adaptation of its aerodynamic characteristics along the flight path, which are oriented essentially perpendicular to the tether, thus exerting a pulling force on the tether.

[0003] For the operation of such kites, a safety mechanism is desirable, which still allows control of the kite even if it is not possible to maintain normal operation. For example, a control system may fail, resulting in an operating state in which the kite can no longer be actively controlled. If in this state the kite exerts high tension on the tether, in some circumstances it is not possible to reel the tether in. Also, due to a failure of the tether winch, a situation may arise in which it is not possible to reel the kite in. In case of a tether tear, it is known from EP 3 456 630 A1 to connect the break point with a catch device. Since the catch device needs a certain distance to be able to absorb the high forces, part of the flight height that can be used in normal operation is lost.

[0004] The object of the present invention is to propose a method and a kite system, which allows a reliable and safe landing of the kite system even outside of normal operation. In view of the above-mentioned prior art, this object is achieved by the features of the independent claims. Preferred embodiments are provided in the dependent claims.

[0005] In the method according to the invention, the sail of the kite is spread over a first kite section and a second kite section, and a connection present in the sail between the first kite section and the second kite section is separated such that the kite assumes a different aerodynamic state and falls to the ground together with the control pod.

[0006] The present invention recognises that separating the connection present in the sail between the first and second kite sections provides a quick and reliable way to modify the aerodynamic state of the kite such that the drag is reduced. After the connection is separated, an aerodynamic state is assumed in which the lift exerted by the kite is no longer sufficient to keep the kite system in the air. The kite and the control pod connected to it fall to the ground and the kite acts as an umbrella.

[0007] In particular, the kite can function as a decelerating parachute in this state so that when the rope load is high, the tension energy in the rope is reduced without the rope experiencing a sudden reduction in load, which is undesirable since a sudden reduction in load may cause the tether to bounce off the pulley at the ground station. If the tether is prevented from bouncing, the tether can be pulled further despite the emergency landing system being triggered. The method is preferably carried out such that after triggering the kite assumes a state in which it rotates about the axis of the tether so that it falls to the ground under low load but with the tether pulled.

[0008] The sail surface refers to the area of ​​the kite through which air flows as the kite moves along its flight path. The sail surface may include an inner surface facing the control pod and an outer surface facing away from the control pod. The inner and outer surfaces may be spaced apart from each other and may span an airfoil shape. The link may extend in the direction of the airfoil shape such that both the first kite section and the second kite section form a complete airfoil shape before separation. The airfoil direction is designated as the longitudinal direction of the kite. When viewed laterally, the first kite section may be positioned next to the second kite section.

[0009] An attachment point is ground if it is not lifted off the ground surface by the pulling force of the kite. A ground attachment point can be fixedly connected to the ground. For example, it could be a ground attachment point on a ship, a floating barge, or a land-based mobile system.

[0010] During normal operation of the system, a joint between the first and second kite sections is formed in the sail surface. The joint may form a continuous transition between the first and second kite sections. The joint may be designed such that the sail surface and / or airfoil are not interrupted in the area of ​​the joint.

[0011] The method may be performed such that the first and second kite parts are completely separated from each other such that after separation there is no longer any connection in the sail surface between the first and second kite parts.In another embodiment, the first and second kite parts are partially separated from each other such that after separation there is still a connection in the sail surface between the first and second kite parts.

[0012] The first kite section and the second kite section can be the same size so that separation occurs at the center of the kite. It is also possible for the two kite sections to be of different sizes so that the kite separates off-center.

[0013] The kite may comprise three or more kite sections. In each case, two of the kites involved span a sail surface within the meaning of the invention. The kite sections may be arranged adjacent to one another in the transverse direction of the kite, such that in each case the central kite section is included between two laterally adjacent kite sections. The connection which is separated when carrying out the method according to the invention may in each case be formed between two adjacent kite sections. Even relatively large kites can be landed reliably by separating them into three or more kite sections.

[0014] The separation of the kite parts may be triggered by a trigger element. The kite system may thus be configured such that the trigger element is automatically triggered when it is not possible to maintain normal operation of the kite system. The trigger element may be triggered after an exceptional event. An exceptional event resulting in it being not possible to maintain normal operation may consist, for example, in a break in a line or tether of the line system or in an excessive load acting on a line or tether of the line system. An exceptional event may also consist in a situation in which one or more operating parameters of the kite system are outside of normal ranges, as determined in the control unit.

[0015] In addition to or as an alternative to an independent trigger, the possibility may be provided for the trigger element to be triggered by external intervention. Intervention may occur, for example, when an operator notices that the kite system has assumed an abnormal state. Intervention may consist, for example, of the operator making an input or activating a switch.

[0016] The trigger signal may be mechanically transmitted to the trigger element. For example, the trigger element may be mechanically coupled to the rope such that the trigger element is triggered when the rope breaks or is overloaded. The trigger signal may also be a control signal that is electronically communicated to the trigger element. In particular, the control signal may be communicated to the trigger element by a cable or via a wireless connection.

[0017] The kite may have a predetermined separation point at which the connection between the first and second kite sections is separated. A locking device may be provided at the predetermined separation point such that the connection between the first and second kite sections is maintained as long as the locking device is active. The predetermined separation point may be designed such that the connection between the first and second kite sections is separated by application of an aerodynamic force acting on the sail surface when the locking device is no longer active.

[0018] The predetermined separation point may include a zipper, which connects the first kite section and the second kite section to one another. The zipper may be held closed by a fastening device. A portion of the zipper may be loosened by removing the fastening device, allowing the zipper to open vertically. The zipper may continue to open in one or both directions from the loosened portion. In one embodiment, the zipper is designed such that some teeth are missing or disengaged in the area where the fastening device is located.

[0019] In another variation, the kite portion may be joined at the predefined separation point with a material that is less tear resistant than the adjacent material of the sail surface, such that the material at the predefined separation point tears after the fastening device is released. A seam that loosens longitudinally after the fastening device is released is also possible. In another embodiment, a fuse extends along the predefined separation point, which is ignited by a trigger element. The material of the kite may be weakened by the fuse at the predefined separation point, such that the kite tears.

[0020] The predetermined separation point may be designed to occur after the fastening device is released under the influence of aerodynamic forces occurring during normal operation of the kite system.

[0021] Also, to separate the linkage, the kite can be subjected to higher aerodynamic forces at a predetermined separation point than during normal operation of the kite system. The method can be performed such that the higher aerodynamic forces directly cause the separation at the predetermined separation point. Alternatively, the separation at the predetermined separation point can be achieved by a combination of the release of the fastening device and the higher aerodynamic forces.

[0022] The line system between the control pod and the kite may comprise a number of lines by which pulling forces are transmitted from the kite to the control pod. The line system may comprise lines designed as active steering lines, the free length of which between the control pod and the kite may be adjusted. The kite may be steered by activating the active steering lines to move along a desired flight path. The line system may comprise lines designed as fixed lines, by which the parts of the kite are held a fixed distance apart. The line system may comprise lines designed as passive steering lines, which extend between a first attachment point on the kite and a second attachment point on the kite and are redirected between the attachment points on a pulley connected to the control pod. The distance between the control pod and the first attachment point and the distance between the control pod and the second attachment point may be changed using such passive steering lines, the sum of the two distances remaining constant. The fixed lines may be located in the part of the kite that is central to the lateral direction. The steering lines may be arranged in the peripheral portion of the kite, and the passive steering lines may be arranged laterally in the part of the kite located between the central portion and the peripheral portion.

[0023] The kite system may be configured such that the lines of the line system are cut by triggering of the triggering element. To enable the cutting triggered by the triggering element, the lines or the holding elements connected to the lines may be provided with, for example, a pyrocutter or a compressed air shackle. When no more pulling force acts on the relevant part of the kite, the part moves away from the control pod. The movement of the relevant kite may be used to release the fixing device. For example, a fixing line may run from the control pod to the fixing device via the relevant part of the kite, such that a pulling force is applied to the fixing device by a movement in the kite. The line cut by the triggering element may be a fixing line.

[0024] The kite may be designed such that a cavity surrounded by the skin is enclosed between the outer and inner surfaces of the kite. During normal operation of the kite system, an elevated pressure may be present, for example between 50 mbar and 1000 mbar, preferably between 100 mbar and 500 mbar, higher than the ambient pressure. The elevated pressure may be provided by an air current flowing along the sail surface as the kite moves along its flight path. The kite may have an inlet opening arranged between the outer and inner surfaces of the kite. In particular, the inlet opening may be arranged at an end surface of the kite facing the direction of movement.

[0025] By separating the connection between the first and second kite sections, an opening can be created in the kite's skin through which the elevated pressure present inside the kite can escape. By releasing the elevated pressure, the aerodynamic state of the kite can be modified so that the pulling force acting in the direction of the control pod is reduced.

[0026] The invention further relates to a kite system comprising a kite and a control pod. The kite is held on the control pod via a line system. A sail of the kite spans a first kite section and a second kite section. A connection between the first kite section and the second kite section is formed in the sail. The kite system comprises a trigger element for separating the connection so that the kite assumes a different aerodynamic state after the connection is separated and falls to the ground together with the control pod.

[0027] The kite system may comprise a tether extending between the control pod and a ground attachment point. The attachment point may be a constituent part of a kite system component fixedly connected to the ground. The kite system may be an element of an apparatus for generating electrical energy. The apparatus may comprise a generator driven via a tether winch. It is also possible for the kite system to be connected to an attachment point of a vessel so that power for the vessel can be generated by the kite system. The attachment point of the vessel is a ground attachment point within the meaning of the present invention.

[0028] The kite system may further be developed with the further features described in connection with the method according to the invention.The method may further be developed with the further features described in connection with the kite system according to the invention.

[0029] The invention is described below by way of example using preferred embodiments with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0030] [Figure 1] 1 is a schematic diagram of an apparatus according to the present invention; [Diagram 2] FIG. 2 is a schematic diagram of the device of FIG. 1 in operation; [Diagram 3] FIG. 1 shows a kite system according to the present invention. [Figure 4] FIG. 4 is an enlarged view of a detail of the kite system of FIG. [Diagram 5] FIG. 4 is another enlarged view of the details of the kite system of FIG. [Figure 6] FIG. 4 is yet another enlarged view of details of the kite system of FIG. [Figure 7] 1A-1D show different states of the kite system according to the invention; [Figure 8] FIG. 2 shows another state of the kite system according to the invention. [Figure 9] FIG. 2 shows yet another state of the kite system according to the invention. [Figure 10] FIG. 2 shows yet another state of the kite system according to the invention. [Figure 11] FIG. 4 shows an alternative embodiment of the device according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The device according to the invention for generating electrical energy comprises, according to Fig. 1, a kite system 23 according to the invention connected via a tether 15 to a tether winch 16. The kite system 23 comprises a kite 14 connected via a line system 24 to a control pod 25.

[0032] A power drive device 17 is coupled to the tether winch 16, which in a first operating state acts as a generator and in a second operating state acts as a motor. The power drive device is coupled to the public electricity grid 19 via a power train 18 comprising an inverter and a transformer, so that the electrical energy generated by the power drive device 17 can be fed to the electricity grid 19 or the power drive device 17 can be operated as a motor by electrical energy taken from the electricity grid 19. The apparatus comprises a control unit 20 designed to control the interaction of the components of the apparatus.

[0033] The control unit 20 comprises an antenna 22 so as to be able to exchange control signals with the control pod 25 via a wireless connection 22. In particular, the control signals are sent from the control unit 20 to the control pod 25 in order to control the flight path of the kite 14. The lengths of the steering lines of the line system 24 are modified using the control signals, so that the flight direction of the kite 14 is influenced.

[0034] In the exemplary embodiment according to Fig. 2, the kite 14 is guided in a figure of eight oriented essentially transversely to the wind direction W. While the kite 14 follows its flight path, a pulling force is applied to the tether 15, which drives the power drive device 17 via the tether winch 16. The mechanical energy is converted into electrical energy and is supplied to the public grid 19 via the power train 18 by the power drive device 17, which in this operating state operates as a generator. It is also possible to store part of the generated energy in the form of electricity in the energy storage of the power train 18. In this way, electrical energy can be generated until the length of the tether 15 is exhausted and all of the tether 15 is taken out of the tether winch 16. The tether 15 is then pulled by the power drive device 17, which operates as a motor, before it is possible to generate electrical energy again.

[0035] The line system 24 of the kite system 23 according to the invention comprises, according to Fig. 3, an active steering line 26, a passive steering line 27 and a fixed line 28, each of which is tied to the control pod 25 and branches from a knot point 29 into several ends which are tied to the kite 14. The fixed line 28 extends from the end fixedly connected to the control pod 25 to the central part of the kite 14. The active steering line 26, the length of which can be adjusted, extends from the control pod 25 to the two peripheral parts of the kite 24. The passive steering line 27, which is deflected by a pulley 30 at the control pod 25, is tied to the kite 14 between the fixed line 28 and the active steering line 26.

[0036] The direction of movement of the kite 14 can be controlled by adjusting the length of the active steering line 26. As the active steering line 26 is adjusted, the passive steering line 27 moves simultaneously over the pulley 30, and the length of the passive steering line 27 from the kite 14, over the pulley 30 and back to the kite 14 remains unchanged.

[0037] The kite 14 forms an airfoil shape extending longitudinally over an outer surface 32 and an inner surface 33 from an end surface 31 visible in Figure 3 to an aft end not visible in Figure 3. During normal operation of the kite system, a cavity at elevated pressure is formed inside the kite 14. The kite 14 includes an opening 34 formed in the end surface 31 through which air can enter the interior, whereby elevated pressure is built up when the kite 14 is moving.

[0038] A zipper 36 is formed in the skin 35 of the kite 14, which extends over both the outer surface 32 and the inner surface 33 over the length of the airfoil, from the end surface 31 to the rear end of the kite 14. The zipper 36 is closed during normal operation of the kite system. By opening the zipper 36, the kite 14 can be separated into a first kite part 40 and a second kite part 41. In the sense of the present invention, the zipper 36 connects the first kite part 40 and the second kite part 41 and forms a predetermined separation point between the first kite part 40 and the second kite part 41.

[0039] The zipper 36 includes a portion from which a number of teeth have been removed and which is secured by a securing device 37 according to FIG. 5. The securing device 37 extends over the zipper 36 and holds it closed despite the lack of teeth. The securing device 37 can be removed by pulling a trigger line 38, which then allows the zipper 36 to be loosened longitudinally by a force acting transversely on the zipper 36. The state of the zipper 36 immediately after the securing device 37 has been removed is shown in FIG. 6, in which the zipper 36 begins to open. Continued pulling laterally allows the zipper 36 to open over its entire length, which results in the first kite portion 40 and the second kite portion 41 being separated from each other.

[0040] The trigger wire 38 runs from the control pod 25, according to Fig. 3, through an attachment point 39 formed on the kite 14 to the fixing device 37. When the fixing wire 28 is released, the trigger wire 38 is pulled, so that the central part of the kite 14 moves away from the control pod 25, so that the fixing device 37 is released. This results in the zipper 36 opening longitudinally, so that the kite 14 is separated into a first kite part 40 and a second kite part 41. The opening of the zipper 36 creates an opening in the skin 35 of the kite 14 through which the increased pressure can escape. In this state, the first kite part 40 and the second kite part 41 each act as an umbrella through which the control pod 25 falls to the ground.

[0041] According to Fig. 4, a pyrocutter 42 is arranged in the part of the fixed line 28 adjacent to the control pod 25. The pyrocutter 42 can be triggered by an electric signal, which results in the cutting of the fixed line 28. The pyrocutter 42 forms a trigger element within the meaning of the present invention. The electric signal for triggering the pyrocutter 42 can be provided and generated by the control unit 20 when an exceptional event occurs, whereby the kite system can no longer operate in normal operation.

[0042] After the fixing line 28 is cut, the central part of the kite 14 rises and thus separates from the control pod 25, so that a tensile stress is applied to the trigger line 38. The fixing device 37 is removed and the zipper 36 is opened so that the control pod falls to the ground together with the two kite parts 40, 41 acting as an umbrella.

[0043] The relevant sequences are shown in figures 7 to 10. The kite system 23 is shown in figure 7 in normal operation. In figure 8 the fixing lines 28 are cut so that the central part of the kite 14 rises and the fixing device 37 is moved away from the zipper 36. In figure 9 the zipper 36 is partially loosened. After the zipper 36 is fully loosened the two kite parts 40, 41 are separated from each other. As the increased pressure escapes from the inside the kite parts 40, 41 lose their aerodynamic profile and continue to function only as umbrellas.

[0044] An alternative embodiment of the invention is shown in FIG. 11 in which a kite system 23 according to the invention is used to generate power for a watercraft 43 .

Claims

1. 1. A method for landing a kite system (23), comprising a kite (14) and a control pod (25), the kite (14) being held on the control pod (25) via a line system (24) and the control pod (25) being held on a ground attachment point (16, 44) via a tether (15) during normal operation of the kite system (23), the sail of the kite (14) being spread over a first kite part (40) and a second kite part (41), a connection (36) present in the sail between the first kite part (40) and the second kite part (41) being separated so that the kite (14) adopts a different aerodynamic state and falls to the ground together with the control pod (25).

2. 2. The method of claim 1, wherein the sail surface includes an inner surface (33) facing the control pod and an outer surface (32) facing an opposite side of the control pod, the inner surface (33) and the outer surface (32) being spaced apart from each other and extending in an airfoil shape.

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

4. Method according to any one of claims 1 to 3, characterized in that the separation of the connection (36) is triggered by a trigger element (42).

5. 5. The method of claim 4, characterized in that the trigger element (42) is triggered by a control signal from a control unit (20).

6. Method according to any one of claims 1 to 5, characterized in that the kite (14) has a predetermined separation point (36) forming the connection between the first kite part (40) and the second kite part (41).

7. 7. The method according to claim 6, characterized in that the predetermined separation point comprises a zipper (36) by which the first kite portion (40) and the second kite portion (41) are connected to each other during normal operation of the kite system (23).

8. A method according to claim 6 or 7, characterized in that the predetermined separation point (36) is fixed by a fixing device (37) during normal operation of the kite system (23).

9. Method according to any one of claims 6 to 8, characterized in that the zipper (36) is designed so that some teeth are missing or not engaged in the area where the fastening device (37) is placed.

10. Method according to any one of claims 4 to 9, characterized in that after the triggering of the trigger element (42), the kite (14) assumes an aerodynamic state in which the forces acting on the linkage (36) are higher than during normal operation of the kite system (23).

11. Method according to any one of claims 4 to 10, characterised in that the lines (26, 27, 28) of the line system (24) are cut by the triggering of the trigger element (42).

12. Method according to any one of the preceding claims, characterized in that by separating the connection (36) between the first kite part (40) and the second kite part (41), an opening can be created in the skin (35) of the kite (14) through which the elevated pressure present inside the kite (14) can escape.

13. A kite system (23) comprising a kite (14) and a control pod (25), the kite (14) being held on the control pod (25) via a line system (24), a sail surface of the kite (14) spanning a first kite section (40) and a second kite section (41), a connection (36) between the first kite section (40) and the second kite section (41) being formed in the sail surface, the kite system (23) further comprising a trigger element (42) for separating the connection (36) so that after separating the connection (36), the kite (14) assumes a different aerodynamic state and falls to the ground together with the control pod (25).

14. 13. A kite system according to claim 12, characterized in that the control pod (25) is held on a ground attachment point (16, 44) during normal operation of the kite system (23) via a tether (15).

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