NL2023519B1 - An airborne wind energy system, and ground station - Google Patents

Abstract

An airborne wind energy system comprising a wind-engaging member connected to a tether, and a ground station (1), the ground station (1) at least including: -a tether storage device for winding and unwinding the tether, -a tether guiding unit for guiding the tether to the tether storage device, and -an energy converting device connected to the tether storage device; wherein the system includes a steering device to generate a steered movement of the wind engaging member and/or to steer the relative angle of the wind engaging member with respect to tether, one or more control units for steering the wind- engaging member and/or winding and unwinding the tether, wherein the ground station (1) includes a container shaped housing (1A), wherein the tether guiding unit is movable in parallel with respect to a rotation axis of the tether storage device.

Description

P124047NL00 Title: An airborne wind energy system, and ground station The invention concerns an airborne wind energy system comprising a wind-engaging member connected to a tether, a tether storage device for winding and unwinding the tether, an energy converting device connected to the tether storage device, a steering device to generate a steered movement of the wind engaging member and/or to steer the relative angle of the wind engaging member with respect to tether, one or more control units for steering the wind- engaging member and/or winding and unwinding the tether. The invention also concerns a method for operating such wind energy system.

Such a system is known from NL2009528. Summarizing the prior art, airborne wind energy systems are designed to operate at higher altitudes than conventional tower-based wind energy systems. The wind- engaging members are typically rigid wings, flexible wings or aerostats. The wind-engaging member is tethered to a ground station. The ground station comprises a tether storage device, typically a winch, to wind and unwind the tether, and is connected to an energy converting device, typically a generator. During unwinding of the tether, the wind-engaging member is steered along a certain flight trajectory that can depend on the wind direction. Respective cross wind flight manoeuvers generate a high traction force which is transferred by the winch to the generator where it is converted to electricity. When reaching e.g. the maximum tether length the wind engaging member is de-powered. This means that the relative angle of the wind-engaging member with respect to the apparent wind is reduced such that the traction force in the tether is minimized. Using the generator as a motor, the tether will then be wound onto the drum. Since the traction force during winding is substantially lower than during unwinding, the energy consumed is only a fraction of the energy generated during unwinding.

The present invention aims to provide an improved airborne wind energy system. In particular, the invention aims to provide an airborne wind energy system that can be efficiently operated, that can provide good or optimum energy generation as well as ease of use, improved portability and flexibility.

According to a first aspect of the invention there is provided a system that is characterized by the features of claim 1.

Advantageously there is provided an airborne wind energy system comprising a wind-engaging member connected to a tether, and a ground station, the ground station at least including: -a tether storage device for winding and unwinding the tether, -a tether guiding unit for guiding the tether to the tether storage device, and -an energy converting device connected to the tether storage device; wherein the system includes a steering device to generate a steered movement of the wind engaging member and/or to steer the relative angle of the wind engaging member with respect to tether, one or more control units for steering the wind- engaging member and/or winding and unwinding the tether, wherein the ground station includes a container shaped housing.

In a preferred embodiment, the tether guiding unit is movable in parallel with respect to a rotation axis of the tether storage device.

In this way, shipment of the ground station can be carried out in a relatively straight-forward manner, e.g. using common container carriers, trucks, shipping, cranes and the-like. In a particular advantageous embodiment the container is a standardized shipping container, e.g. an intermodal container. Also, in this way a relatively compact ground station of the system, can be achieved, in particular during transport and/or storage of the system.

Further, advantageously, the tether guiding unit is movable in parallel with respect to a rotation axis of the tether storage device. The tether guiding unit can be movable connected to or held by the container in various ways as will be clear to the skilled person, for example via a respective guiding track. Due to the parallel movement with respect to the rotation axis of the tether storage device, efficient and reliable winding and unwinding of the tether can be achieved, as well as optimal use of a storage capacity of the tether storage device.

According to a preferred embodiment, a top side of the housing includes an elongated tether receiving passage, in particular a passage extending in parallel with respect to the rotation axis of the tether storage device.

In this way, the tether can be led the tether storage device from respective positions viewed along the axis of rotation of the tether storage device, without being obstructed by the upper side of the container. Also, in this way, optimal tether guidance towards the tether storage device can be achieved (e.g. such that the tether engages the tether storage device substantially tangentially at any time, during operation).

Further, it is preferred that the top side of the housing includes a recess (e.g. an elongated recess) for receiving at least part of the tether guiding unit, the recess also providing the elongated tether receiving passage.

As a result, the tether guiding unit can at least partly be located within the housing, to be shielded thereby during operation, whereas the recess can be configured for allowing the movement of the tether guiding unit (i.e. the movement in parallel with respect to the axis of rotation of the tether storage device).

Also, in a preferred embodiment, at least part of the tether guiding unit, e.g. a main guiding pulley, protrudes through an outer side of the housing.

As a result, for example, a first external engaging point between the tether section extending towards the wind-engaging member (at least, during operation) and the tether guiding unit can be located externally of the outer side of the housing (e.g. above the housing), which provides safety and operator observability of proper functioning.

It is preferred that at least part of the tether guiding unit is rotatably coupled to the housing, a respective axis of rotation in particular being a vertical axis, allowing for improved tether traction transmission at various flight positions of the wind engaging member Also, the present invention provides a ground station for an airborne wind energy system, the ground station at least including: -a tether storage device for winding and unwinding a tether, -a tether guiding unit for, during operation, guiding the tether to the tether storage device, and -an energy converting device connected to the tether storage device, wherein the ground station includes a container shaped housing (14), wherein the ground station includes a container shaped housing, wherein the tether guiding unit is movable in parallel with respect to a rotation axis of the tether storage device.

In this way, above-mentioned advantages can be achieved.

Further advantageous embodiments follow from the dependent claims.

The invention will now be elucidated referring to the drawings of a non-limiting embodiment.

Therein shows: Figure 1 an embodiment of an airborne wind energy system according in perspective view;

Figure 2 the airborne wind energy system of Fig. 1 in unwinding respectively winding modes; Figure 3 a perspective side view of a ground station of a system according to a non-limiting embodiment of the invention; 5 Figure 4 a perspective view of a lateral side of the ground station of Fig. 3; Figure 5 a side view of the ground station of Fig. 3; Figure 6 a top view of the ground station of Fig. 3; Figure 7 an opened perspective view of the ground station of Fig. 3; Figure 8 a detail VIII of Fig. 7; Figure 9 a longitudinal cross-section, over line IX-IX of Figure 6; and Figure 10 a transversal cross-section, over line X-X of Figure 6. Corresponding or similar features are denoted by corresponding or similar reference signs in this patent application.

As follows from Figures 1, 2, an airborne wind energy system generally includes a ground station 1, a tether 2, a bridle system 3 and a wind engaging member 4. The ground station 1 comprises a tether storage device 5, an energy converting device 6, a battery/power electronics module 7 and a control center 8 (the battery/power electronics module 7 can e.g, be a separate component). In place of using a rechargeable battery for storing electrical energy, a mechanical energy storage device may be employed.

The tether storage device is typically a drum 5 (see Figures 3-7, 8), rotating around a respective rotation axis during operation.

The energy converting device 6 may for instance be a generator connected to the drum.

The battery/power electronics module is configured to store energy, and may e.g. supply energy to an energy distribution network or power grid.

As the electric power is intermittently produced the battery or other storage device (for instance one or more appropriate capacitors) is applied to balance the electric energy over the pumping cycle of the system. It stores the energy generated during unwinding of the tether and will release a small fraction of this energy for winding the tether, as hereinafter will be explained in more detail. Moreover, the battery will ensure a nominal electricity output also during periods in which the system is not generating energy. It is re- marked that the storage capacity of the battery (or other storage device) can remain limited when simultaneously several airborne wind energy systems m accordance with the invention are applied that connect to such battery/storage device. The control center 8 may comprise several interconnected computers hosting different software components required for operating the airborne wind energy system 1. In addition, the control center 8 may comprise wireless modems to connect remote sensors, remote actuators and a steering device 19. The function of the steering device 19 is further explained hereinafter with particular reference to figure 3.

The tether 2 transfers the traction force generated by the wind- engaging member 4 to the tether storage device 5. The tether 2 is typically made of a strong and lightweight plastic fiber, cord or rod, and is connected to the bridle system 3 of the wind- engaging member 4. The connection of the tether 2 with the bridle system 3 preferably includes additional safety features such as a metal-based weak link, which ruptures at a predefined maximum traction load, and a cable release system, e.g. a (pyrotechnic) cable cutter. Further a two-stage fabric-based shock absorber is provided as part of the safety mechanism that connects the tether (before any of the controlled rupture points) with the kite itself, thus bypassing the bridle system. The connection may also include a (not shown) sensor to measure tether force.

The wind-engaging member 4 as shown in figure 1 can e.g. be a kite or kite-like structure, of the wing type. For example, the wing type kite can include an inflatable membrane. Such inflatable membrane wing kite is robust and still sufficiently flexible to be optimal steerable. In another embodiment a fixed wing type wind engagement member can be installed. For example, instead of the kite there can be provided a wind-engaging member in the form of is of a fixed (rigid) wing airfoil type, having e.g. a rigid main wing section that extends substantially normally with respect to the tether during operation.

In figure 2 the principle of power generation by the airborne wind energy system is shown. The system 1s operated in periodic pumping cycles, alternating between unwinding and winding of the tether 2. In a non- limiting example, during unwinding, the wind-engaging member 4 is steered along a certain flight trajectory 10 transverse to the wind in order to optimize the traction force in the tether 2. In an embodiment, the flight trajectory will be a figure-eight manoeuver. When reaching e.g. a maximum tether length, the wind-engaging member 4 is de-powered. In an embodiment, the wind- engaging member is de-powered by rotating the wind-engaging member 4 relative to the tether 2 by means of actuators in the steering device. The wind-engaging member 4 is then aligned with the apparent wind direction 11, i.e. the wind direction that the wing experiences during flight. The tether storage device 5 will start to retract the tether 2 and accordingly will bring the wind-engaging member 4 to its initial position. From there a new pumping cycle may start. A de-powering by rotating the wind-engaging member (or alternatively, stopping following the figure-eight manoeuver trajectory) reduces the traction force during winding considerably and therefore the energy consumption during winding is only a fraction of the energy generated during unwinding. Optimization of the power output requires an optimal synchronization of winding/unwinding and flight dynamics of the wind-engaging member, as will be appreciated by the skilled person.

For transmission of kite (i.e. wind) force to the tether 2, the bridle 3 of the system includes a number of separate power- lines 11 that are connected to respective connection points located at or near a leading edge

LE of the wind-engaging member 4. Optionally, the bridle 3 can include one or more steering lines 16 that are connected to the wind engaging member at respective one or more steering points remote from the connections points. The bridle 3 can be configured such that its power-lines 11 take up and transmit most of the wind traction force, during unwinding, to the tether 2, wherein the steering lines 16 transmit only a small G.e. significantly smaller than the force transmitted by the power lines) amount of wind force from the wind-engaging member 4 to the tether 2 (during unwinding). In such an embodiment, Thus, a clear distinction can be made between the function of the powerlines and the steering lines.

In an alternative embodiment (not shown), power-lines can also serve as steering lines and vice-versa, wherein all those bridle lines can be controlled for steering the kite.

Generally, the system includes one or more steering device 19, e.g.

incorporated in the bridle, to generate the steered movement of the wind engaging member 4. The steering device 19 can include e.g. one or more actuators (more particularly one or more drums) for winding and unwinding one or more of the steering lines 16, to adjust the orientation of the wind engaging member 4 in order to follow a predetermined or desired flight path (as mentioned above).

Figure 3 shows a further embodiment of the ground station 1 of the system. As follows from the drawings, in a preferred embodiment, the ground station 1 includes a container shaped housing 1A. In the present example, the housing 1A includes a top side 1T, bottom side 1B, opposite end sides (transversal sides) 1E and opposite longitudinal sides 1L. In a further embodiment, outer edges of the housing may include a reinforcement structure 1R, for example a metal or steel frame or the like. Furthermore, each of the sides of the housing may include a respective side wall that can be substantially closed for shielding an interior of the housing against rain and wind. Also, one or more sides or side walls of the housing may include or be provided by a removable cover or door. In the present example, a or each lateral side 1E includes a removable cover or door, providing access to the interior of the housing (see in particular Fig. 4 wherein the cover has been removed c.q. the door has been opened allowing access to interior via the visible transversal side 1E). Also, as will be mentioned below, in a preferred embodiment a top side (or top wall) IT of the housing 1A can be provided with a structure allowing passage of the tether into the housing 1A, the structure preferably being configured for holding at least part of a tether guiding unit 50 externally of the housing 1A.

The housing 1A may be or substantially be made of a shipping container, e.g. having metal or steel side walls, but that is not required. Also, the container can have standardized external shipping container dimensions. For example, the ground station (i.e. its container) can have a rectangular cuboid shape. Also, for example, a length of the ground station (measured in parallel with respect to the longitudinal walls 1L) can be about feet (about 6 m) or about 40 feet (about 12 m). Besides, for example, a width of the ground station (i.e. measured normally with respect to the longitudinal walls 1L) can be about 2.4 m, wherein a height of the ground 20 station is preferably about 2.4 m. In this way, said standard shipping container dimensions can be provided, however, the invention is not limited to such dimensions.

The tether guiding unit 50 can be configured in various ways. It can include one or more pulleys 51 for leading the incoming tether 2 (extending towards and coupled to a flying wind engaging member during operation, as is indicated by a dashed line 2 in Fig. 5) into the container 1A. In the drawing a main pulley 51 of the guiding unit 50 is visible. The pulley 51 has a horizontal axis of rotation (i.e. its axis of rotation is substantially in parallel with respect to a bottom side of the container 1A), and can be held or supported by a pulley support 54 (see Fig. 8). A distal tether receiving structure, e.g. a guide member, 51 is present for leading/centering the tether 2 onto the pulley 51. Optionally, the distal tether receiving structure 52 can be movably/swivably arranged with respect to the pulley (as is indicated by arrows w in Figure 8), via a respective swivel arm 53 (that can be pivotally connected to a pulley support 54), allowing tether guidance towards different circumferential positions of the pulley 51. Also, to that aim the distal tether receiving structure 52 itself may be pivotally connected to a distal end of the swivel arm 53. Further, in the present example, the tether guiding unit (in particular the initial pulley 51) is movable in parallel with respect to a rotation axis of the tether storage device (i.e. the drum) 5, as is indicated by arrow N in Figures 5, 7, the drum’s axis of rotation being in parallel with respect to a longitudinal center line of the present container housing 1A.

In this way, the tether guiding unit 50 can e.g. be moved back and forth,

preferably multiple times, between two end opposite end positions for delivering the tether to substantially an entire tether storage space of the drum (viewed along a drum’s axial direction), and filling that space neatly (i.e. allowing large or maximum winding capacity) during winding.

The ground station can include e.g. a guide structure 56 (for example a track) for movably guiding the tether guiding unit 50 between its opposite end positions, and for example a drive (which may include a motor 57) and respective drive transmission means that drive such displacement of the tether guiding unit 50. For example, the motor 57 can be a electric spindle motor connected a worm gear for moving the unit 50 from one side to the other with respect to the tether storage device 5 (in said direction N). Such a transmission can also serve as a breaking device, (i.e. it can keep the unit in position in case the drum does not wind or unwind the tether). Another option for said transmission can e.g. be a chain transmission system, or differently, e.g. including a frame guiding the unit 50 on wheels.

In an alternative embodiment, the tether guiding unit 50, in particular the initial pulley 51, has a substantially fixed position with respect to the tether storage device, 1.e. the initial (main) pulley 51 is not movable in parallel with respect to the rotation axis of the tether storage device 5. For example, the tether storage device 5 may be displaceably in axial direction (i.e. parallel to the direction of arrow N), or other tether guiding means can be located between the initial pulley 51 and the tether storage device 5 for allowing proper efficient tether winding (providing large or maximum winding capacity) onto the drum.

In a further embodiment, the top side IT of the housing 1A includes an elongated tether receiving passage 1P, in particular a passage P extending in parallel with respect to the rotation axis of the tether storage device.

More particularly, as follows from the drawings, the top side 1T of the housing can include a recess for receiving at least part of the tether guiding unit, the recess (in particular its open upper side) also providing the elongated tether receiving passage 1P. In this case, the recess of the top side 1T is defined between two opposite longitudinal recess sides 71, two opposite transversal recess sides 72, and a recess bottom side 73 that extends substantially in parallel with the top side 1T of the housing (at a level vertically below a level of that top side 1T). The bottom side 73 of the recess section can include an aforementioned a guide structure 56 for movably guiding the tether guiding unit 50 through the recessed section of the housing. In this example, the side walls of the recessed section are mutually tapered (see Fig. 9, 10), e.g. providing the recess a truncated rectangular pyramid shape.

Preferably, the bottom 73 the of recessed section 71, 72, 73 of the housing is substantially water-tight. The recess section can include water draining means, for example having one or more draining passages 81 in a recess wall and a respective drain pipe structure 82 for receiving water from such passages 81 and lead such water through and out of the container 1A via an outlet 83 (e.g. via a container bottom, as in Figure 10).

As follows from the drawings (see e.g. Fig. 5) at least part of the tether guiding unit, e.g. a main guiding pulley 51, protrudes through an outer side of the housing, in this case trough the top side 1T of the housing (i.e. through the respective tether passage provided by the open top side of the recessed section 71, 72, 73).

In a preferred embodiment, the tether guiding unit 50 is movable between an idle position wherein the unit is located substantially entirely within the container housing (e.g. within the recess section), and an operational position (as show)wherein the tether guiding unit protrudes at least partly through the tether receiving passage P. For example, at least part of the tether guiding unit can be swivable between the idle position and the operational position. In the present example, the main guiding pulley 51 and preferably also the distal tether receiving structure 52 can be movable between the depicted operational position and a lower position, wherein they are located below the level of the upper side of the housing in said lower position (i.e. within the recess section). For example, to that aim, the a pulley support 54 may be swivable downwardly (indicated by arrow k in Fig.

8), for storing the pulley 51 within the container shaped housing 1A. When the pulley 51 is to be used during operation of a tethered wind engaging member the pulley support 54 can be rotated back upwardly (in a direction reverse to arrow k), towards the depicted operating position. Similarly, the distal tether receiving structure 52 can be pivoted to a respective storage position and operational position, utilizing the respective pivotal connection (as indicated by arrows w in Fig. 8).

In a further preferred embodiment, at least part of the tether guiding unit U can be rotatably coupled to the housing, a respective axis of rotation s (see Fig. 9) in particular being a vertical axis. For example, the tether guiding unit can include a bearing 58 for rotatably supporting the rotatable part of the tether guiding unit U (the bearing 58 for example being located in or on a carrier that is movable along said track 56). It is preferred that rotatable part of the tether guiding unit U is rotatable over a relatively large angle, for example an angle of at least 90 degrees, preferably at least 180 degrees, more preferably at least 270 degrees and most preferably 360 degrees. In the present example, at least the main guiding pulley 51 (and respective distal tether receiving structure 52) is rotatably coupled to the housing in this manner, e.g. by the bearing 58 via the pulley support 54.

In a preferred embodiment, the ground station includes a drive M (e.g. a motor) for driving the tether storage device for winding the tether, the drive M being separate from the energy converting device 6. A possible location of the drive M is schematically indicted in Fig. 9 (by a dashed box M). Preferably, the tether storage device is arranged between the drive M and the energy converting device 6. For example, the energy converting device and drive M can have different lengths (measured in longitudinal direction of the ground station). A said drive M can e.g. be powered by energy that has been generated (and stored) by the energy converting device

6. The advantage of such a system is that the generator unit can be used more efficiently for production.

In another embodiment, for example, rive for driving the tether storage device for winding the tether can be located within the drum 5, as will be appreciated by the skilled person.

In a further preferred embodiment, the ground station 1 includes at least two tether storage devices (e.g. respective drums), preferably at least three, for winding and unwinding at least two, preferably at least three, tethers. In this way, the same ground station can be used for operating respective at least two (at least three) wind engaging members.

In that case, for example, a single energy converting device is connectable to each of the at least two, preferably at least three, tether storage devices, utilizing e.g. respective transmission means (e.g. suitable transmission gears and the-like). For example the two or more tether storage devices can be located next to each other, in a row, e.g. having respective rotation axes that are aligned with each other.

Figure 9 indicates with dashed lines how instead of a single drum 5 a respective multiple tether storage device system can be installed, including three drums 5A, 5B, 5C located next to each other.

In that case, preferably, each of the drums 5A, 5C, 5C 1s preferably independently connectable to the energy converting device 6 for driving that device during a respective drum tether unwinding movement.

Also, each of the several drums 5A, 5B, 5C may include a single drive M for driving that drum in order to wind a respective tether onto the drum.

In a preferred embodiment, multiple ground stations 1 are operated at the same time, in a certain area, for harvesting wind energy.

For example, multiple ground stations 1 can be installed locally, but spaced apart at a certain distance (e.g. at least 50 m, preferably at least 100 m, and also preferably less than 1 km), and operate together of communicated for controlling movements of respective wind engaging members that are connected to those ground stations.

For example, several ground 1 stations or subunits of ground stations can be coupled together, utilizing a control strategy for multiple wind engaging members within a respective small flight area.

One possible control strategy can e.g. be to coordinate multiple wind engaging members by keeping the members in mutually different operational zones (e.g. left, right, stacked above one another or any other form of filling the 3D space). Another strategy can be to operate the respective wind engaging members at least partly within the same operational zone, e.g. utilizing communication between control centers 8 of the ground stations in order to prevent crashes.

This can be done e.g. via a centralized supervisor component provided by the control centers 8 or within the individual control centers via integrated swarm technology.

The resulting flight paths of the several wind engaging members might deviate from the most optimal path for energy production.

The wings might fly the same paths with a phase shift or may fly complementary paths.

In a further preferred embodiment, the control center 8 of the ground unit 1 is configured for controlling a respective wind engaging member’s flight based on a predetermined force regime.

For example, the ground station (i.e. control center) can be configured to a Minimum Force to Maximim Force controller for maintaining flight of the wind engaging member (i.e. to keep that member ‘in the air’), to generate electricity and for example prevent damage on system (in particular the wind engaging member and/or tether). The control center 8 can be configured to control the flight utilizing a minimum force threshold that wind engaging member needs to keep flying.

Said force in particularly can be or derived from a tension in the respective tether, or e.g. a pulling force of the wind engaging member (onto the drum). One or more sensors may be available to determine or derive that force, for example, the force may be derived from a drum torque, and/or be directly measured via a load cell in or on the tether guiding structure 50. In a minimum force regime, the control center 8 can be configured to decrease a tether reel-out speed (can also go negative) in order to create more ‘apparent wind speed’ at the wind engaging member, which results in an increase of the afore-mentioned force.

In case the wing is within the operational boundaries of (between set ‘min force’ and ‘max force’), a constant speed controller of the control center can be used to keep a set speed of the drum.

In case the force is exceeding a predetermined maximum force limit, the reel-out speed can be automatically be increased by the control center 8 in order to decrease the ‘apparent wind’ at the wind engaging member, decreasing the force.

Furthermore, according to a preferred embodiment, multiple ground station units 1 can be coupled together mechanically (e.g. via container corner fittings), and/or electrically (for example directly via respective Direct Current (DC) -busses, or after respective inverters via Alternating Current (AC)-connections). Ground stations 1 may be also coupled mechanically or electrically to other energy generating systems and/or energy storage systems, such as classic wind turbines, batteries, solar PV, Fuel cells, water purification systems, water pumps and/or the like.

Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, itis to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Reference throughout this specification to "one embodiment” or "an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.

Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described embodiments.

For example, it is preferred that the tether guiding unit is movable in parallel with respect to a rotation axis of the tether storage device, however, other features of the invention can be applied separate thereof, such as: - a top side of the housing includes an elongated tether receiving passage, in particular a passage extending in parallel with respect to the rotation axis of the tether storage device; or the top side of the housing includes a recess for receiving at least part of the tether guiding unit, the recess preferably also providing the elongated tether receiving passage; or

-the tether guiding unit is movable between an idle position wherein the unit is located substantially entirely within the container housing, and an operational, position wherein the tether guiding unit protrudes at least partly through the tether receiving passage.

Claims (15)

Conclusions An air-wind power system, the system comprising a wind-engaging part connected to a tether, and a ground station (1), the ground station (1) comprising at least: -a tether storage device for winding and unwinding the tether, -a rig guiding unit for guiding the tug to the tug storage device, and an energy converting device connected to the tug storage device; wherein the system comprises a control device to generate a controlled movement of the wind-engaging member and / or to control the relative angle of the wind-engaging member with respect to the guy, one or more control units for steering the wind-engaging member and / or the winding and unwinding the tether, the ground station (1) comprising a container-shaped housing (1A), the tether guiding unit being movable parallel to an axis of rotation of the tether storage device. The system of claim 1, wherein a top (1T) of the housing comprises an elongated tether receiving passageway, in particular a passageway extending parallel to the axis of rotation of the tether storage device. The system of claim 1 or 2, wherein the top (1T) of the housing includes a recess for receiving at least a portion of the harness guide unit, the recess preferably also providing the elongated tu receiving passageway. The system of any preceding claim, wherein at least a portion of the harness guiding unit, e.g. a main guide pulley protruding through an outside of the housing. The system of any one of the preceding claims, wherein at least a portion of the rig guiding unit is rotatably coupled to the housing, a respective axis of rotation, in particular a vertical axis, 1s. The system of any preceding claim, wherein the rig guiding unit is movable between an inactive position where the unit is located substantially wholly within the container housing and an operational position where the rig guiding unit extends at least partially through the tu receiving passage. . The system of claim 6, wherein at least a portion of the rig guiding unit is pivotable between the inactive position and the operational position. The system of any preceding claim, wherein the container is a shipping container, for example an intermodal container. The system of any one of the preceding claims, wherein the ground station includes a drive (M) for driving the tether storage device for winding the tether, the drive (M) being separate from the energy converting device. The system of claim 9, wherein the cable storage device is disposed between the drive (M) and the energy converting device. The system of claim 9 or 10, wherein the energy converting device and drive (M) have different lengths. The system of any one of the preceding claims, wherein the ground station (1) comprises at least two guy storage devices, preferably at least three, for winding and unwinding at least two, preferably at least three, guys. The system of claim 12, wherein a single energy converting device is connectable to any of the at least two, preferably at least three, cable storage devices. Ground station adapted to be a ground station of a system according to any one of the preceding claims, the ground station (1) at least comprising: , guiding the tether to the tether storage device, and an energy converting device connected to the tether storage device, the ground station (1) comprising a container-shaped housing (1A), the ground station (1) having a container-shaped housing (1A) ), wherein the harness guiding unit is movable in parallel with an axis of rotation of the harness storage device. A ground station according to claim 14, wherein a top (1T) of the housing comprises an elongated tug receiving passageway, in particular a passageway extending parallel to the axis of rotation of the tug storage device.