In order to scale up the Kitewinder system we must use out-of -the-box thinking, since the lifter kite must be enlarged to the point that it cannot be safely handled. A large lifter kite is required to both lift the turbine system and also provide tension in the cable drive so that it can operate properly. My estimates for a 10 Kw system would require a 100 M2 kite which will have a lifting force of 270 Kg at a wind speed of 10 M/sec. Handling a kite of this size would require a crew of people and be extremely dangerous to manually launch, especially in high winds.
My idea is to launch the kite with auxiliary tethers at the four corners so that it is restrained to maintain its shape. Controlled unwinding of the main tether (cable drive) and the 4 auxiliary tethers will keep the kite in an open position and maintain maximum lift. Landing the kite will reverse this operation. This system can be made fully automatic if the unwind speeds of the auxiliary tethers is coordinated with the unwinding of the primary tether (cable drive). A restrained kite of its nature will require no controls, will operate at a fixed tether angle and be intrinsically safe because there are 4 auxiliary tethers available if any of the tethers break.
The problem is to find a method to raise the extended kite to an elevation of 10 ā 30 meters, where the wind is strong enough to continue the launch. Considering a 100 M2 SS (single skin) kite with bridling will only weigh about 30 Kg, this should not be too difficult. I have thought of two methods to achieve this but I am sure there many others. The first method is to use a lever arm which is temporally attached to the primary tether so that when the tether is retracted a short distance, the arm will lift the kite to the launching altitude. The second method is to lift the kite with an array of LTA balloons which can be retracted when the launching height (10-30 meters) is achieved. We could use helium, hydrogen or hot air for the lifting gas and the balloons can be emptied between launches. For example we only need about 25 M3 of helium to lift the 30 Kg weight.
I have ideas for multiple coaxial turbines, crosswind operation and reorienting turbines to face the wind. These items will enhance performance but are secondary to a system of safely automatically launching and landing a Kitewinder system. Without this or other automatic launching systems, Kitewinder will be limited to generating small amounts of power.
In order to scale up the Kitewinder system we must use out-of -the-box thinking, since the lifter kite must be enlarged to the point that it cannot be safely handled. A large lifter kite is required to both lift the turbine system and also provide tension in the cable drive so that it can operate properly. My estimates for a 10 Kw system would require a 100 M2 kite which will have a lifting force of 270 Kg at a wind speed of 10 M/sec. Handling a kite of this size would require a crew of people and be extremely dangerous to manually launch, especially in high winds.
My idea is to launch the kite with auxiliary tethers at the four corners so that it is restrained to maintain its shape. Controlled unwinding of the main tether (cable drive) and the 4 auxiliary tethers will keep the kite in an open position and maintain maximum lift. Landing the kite will reverse this operation. This system can be made fully automatic if the unwind speeds of the auxiliary tethers is coordinated with the unwinding of the primary tether (cable drive). A restrained kite of its nature will require no controls, will operate at a fixed tether angle and be intrinsically safe because there are 4 auxiliary tethers available if any of the tethers break.
The problem is to find a method to raise the extended kite to an elevation of 10 ā 30 meters, where the wind is strong enough to continue the launch. Considering a 100 M2 SS (single skin) kite with bridling will only weigh about 30 Kg, this should not be too difficult. I have thought of two methods to achieve this but I am sure there many others. The first method is to use a lever arm which is temporally attached to the primary tether so that when the tether is retracted a short distance, the arm will lift the kite to the launching altitude. The second method is to lift the kite with an array of LTA balloons which can be retracted when the launching height (10-30 meters) is achieved. We could use helium, hydrogen or hot air for the lifting gas and the balloons can be emptied between launches. For example we only need about 25 M3 of helium to lift the 30 Kg weight.
I have ideas for multiple coaxial turbines, crosswind operation and reorienting turbines to face the wind. These items will enhance performance but are secondary to a system of safely automatically launching and landing a Kitewinder system. Without this or other automatic launching systems, Kitewinder will be limited to generating small amounts of power.
I have previusly mentioned the russian doll Ā«Matryoshka dollĀ» launch. For this case, start with a 0.5 sqm kite which in turn lifts a 2 sqm kite ending up with a ladder kite setup with increasing size.
The smaller kites are easy to handle alone. The four/five tether approach could be used for the largest size?
Another Ā«out of the boxĀ» option is to use a bungee to lift the heaviest payload into flight altitude. If the lifter kite is moving with the load you lose apparent wind and the lifter will fall downwind. A bungee lets you store energy such that the lifter kite need not move for the load to be lifted. Just an idea, probably a poor oneā¦
Welcome @gordon_sp.
Please could you provide a sketch step by step for the launching method you describe? Thanks.
LEVER-ARM LAUNCH
In order to scale up HAWE systems we require an automatic launch and landing system which is reproducible and safe. With my concept of continuously restraining the lifter kite with diagonal stays, it is possible to launch and land the kite from the same location. With this system a single skin (SS) kite is spread over a frame and restrained in place by the diagonal stays. The frame is attached to a lever arm system which can be hoisted by reeling in the main tether(s). When the lifted frame reaches an adequate height, the wind will catch the kite and continue with the launch. Landing the system reverses this process except that the frame is located on the ground and the kite is spread out on top of it, ready for the next launch. If the winds are inadequate then the lever-arm can be lowered to the ground by extending the tether. The weight of a SS kite is minimal so the frame and arm can be of light weight construction. It may be possible to launch very large kites with this system.
I am a new user so I am not allowed to upload pictures.
- List item
LEVER-ARMPIC.pdf (100.6 KB)
A controlled system of launching and landing which can be fully automated.
Hi @gordon_sp
I really like your ideas of tying a spread soft kite wide for launch and retrieval. Having occasional positive experiences flying a spread network of 4+ windsurfing sails, I was surprised how steady they can be.
Maintaining spread anchoring aspects allows much faster span-wise responses as forces connect over shared span lines.
A rig such as this
Initially retracted by the lines to its rings, on the ground, in between an anchoring ringā¦
Could when launched, have not only power take off as suggested at the feet but could also provide anchor for further networking and tensioning of many other types of kite network components, turbines or lattices, inside or outside of the rings. Further extension could be made vertically and or along concentric networks.
There is definitely potential to use raising posts like you drew on the ground underneath kite network launch nodes. Your drawing suggested a method which looks very affordable.
Long reply. Hope it helps.
Good to see you here.
Edit
If you are looking just to launch a single line
Chuck a kite from Slingshot or cannon or drone. Just by dropping or if you really wantā¦ Neatly unfurlingā¦ a good single skin kite, even though it is left loosely in the air it will often pop quickly into shape with normal inflation. Peeling apart the bag by 2 drones in the air is probably the best though.
Rod,
A very clever idea but how do you automate it? Automatic landing will be even more difficult. We need a system like a HAWE where you throw a switch and walk away. With a fully restrained kite with a controlled program we might be able to achieve this, even if the wind dies completely. I suggest the following landing sequence.
ā¢ A device senses low tension in the return side of the cable drive.
ā¢ Turbine rotation is stopped. (Brake on generator)
ā¢ Main tether is retracted in coordination with auxiliary tethers so the kite is spread out at all times.
ā¢ Spread kite settles on launching mesh ready for next launch.
ā¢ Wind speed indicator establishes that winds are adequate and starts the launch sequence.
Looking at the lever arm, I am thinking that the kite should not have to be thrown all the way to Ā«12 oāclockĀ». A kite will start flying once the force sum for Lift+Drag+Gravity is pointing upwards. This could happen at zero meters altitude, but to be safe some altitude is expected to be required.
Anyhow, the kite probably should not exit the ramp with a horizontal orientation.
Networks kinda lend themselves to coordination. Without coordinated tether tensions on a network, you are effectively flying from fewer lines than designed for. Networks can work in diminished performance states where tethers go wrong. And line failures have to be acceptable. The working state of a network is set by the collected tension pattern of the group of tethers. If our ability to coordinate or control that set of tensions is compromised, our designs should make sure we donāt end up creating big safety problems.
With my current rig, once anchored and set together, itās ready, I launch the lift kite, I switch on the launch brake, I ease out a rope at the top back end to raise the turbine, I set the generation going. Walk away. That sounds good but it could be sooo much better.
Tallak,
It doesnāt matter if the kite lifts off the frame during the initial stages of launch. The kite will be restrained in the proper position by the four corner tethers.
My reference to āhorizontalā applies to the angle of the leading/trailing edge to the horizon. My idea is to prevent rotation of the kite when it is moved from side to side for crosswind action. In addition the angle of attack should be kept fairly constant at all times since this will result in maximum lift. (tether tension). This is shown in my picture of the lifting frame.
AUTOLAUNCH.pdf (122.9 KB)
Here are some further details of my proposed auto-launching and landing system. The turbines or other rotating elements should not be raised in the initial part of the launch. They are however, part of the tether and will therefore have to move during the initial launch. The turbines and upper cable drive components will rest on a rolling wagon which will move from a āparkā position to a ālaunchā position when the lever arm is raised. The āparkā position is further away from the main tether (cable drive) windup reel. In this way, only the kite and the bridling have to be lifted by the lever arm during the initial part of the launch. During landing the kite is steered by the main tether and the four auxiliary tethers so that the turbines settle on the rolling wagon in the āparkā position. As mentioned before, the position of the kite is automatically controlled by the position of the winder for the main tether which controls the position of the winders on the four auxiliary tethers. The whole launch-land procedure can be fully automatic without human intervention. The launch program will be initiated if the winds are strong enough but not too strong and the wind direction is correct. The land program will be initiated if the winds drop below a certain level or as indicated by low tension in the return side of the cable drive. Since the kite is restrained in a fixed position at all times, the only possible movement in low wind or turbulent conditions is to start descending. In this case retraction of the main tether in conjunction with the auxiliary tethers will keep the kite stable.
The drawing improved. Have you made anything physical like it yet?
Hi. Thanks for sharing and the figure is quite understandable this time for me.
I will need more time to think about this, but these are my initial thoughts:
- the auxilliary tethers, will they not be difficult to reel out? In low winds you might have a tether force in total of 100 N, and you divide this on five tethers. Now the back lines I gather will not be very taught, lets assume 15 N. And the winch must be dinensioned for high wind, maybe 4000 N for the scale Iām thinking about. The line will not exit the reel/drum by itselfā¦
- Why the platform? Isnāt a single boom sufficient to lift the kite to a certain height where it will inflate itself without a need for a platform
- Why is this approach better than applying the russian doll principle using a lifter drone, then a smaller kite, then the kite in your drawing. As the top kite is rather stationary, there will not be any severe negative consequences if having this thereā¦
- the minimum required number of tether to do what you want seems to be two (for a fixed wind direction or rotating platform) or three (otherwise). My feeling is that a solution using only two or three tethers rather than five will work better (fewer failure states)
In my concept, the purpose of the auxiliary tethers is to prevent the kite from moving laterally, rotate or changing the tether angle. The tension in these tethers should be very low and only increase if the kite tries to move out of position. Almost all of the tension is in the primary tether where it is used for supporting the turbines and aiding in operation of the cable drive.
You propose an interesting alternative concept. I would prefer two booms under the leading edge of the lifter kite so that it will angle to catch the wind when the booms are lifted. This method does require extra drive systems. When the turbines are lifted they may drag across the ground a short distance and this might be problematic, especially if they are of the 3 bladed type.
In order to launch a pilot kite you need an unwind reel. This reel must be separate from the primary unwind stand. The bottom of the pilot kites tether must have bridling to connect to the top of the main lifter kite. I have trouble visualizing transferring the bottom of the pilot kite tether to the bridling without some complicated hooking system. How do you automate this procedure and how do you automatically land the whole system? Does the pilot kite have any controls to avoid looping?
The only way to ensure that the lifter kite stays in a fixed position and is fully spread out, is to have it restrained at all 4 corners. This condition is critical during the automatic landing operation otherwise relaunch will not be possible.
@gordon_sp What you describe is far too much complex to have a chance to work. Just make sure a drum reel in and reel out works fine is a challenge regarding mechanical stress, automation, software reliability ā¦
Have a look at our reel in process, the last video I uploaded. Just a servo and a brushless. It is a nightmare to makes it reliable in term of mechanics electronics, software.
Ask @tallakt about software. I am sure he has short night sometimes with only a kite and a drum to handle.
Hi Olivier,
In order to fully automate the Kitewinder cable drive system I propose a system where the launch and land operation is separate from the cable drive operation. The tether/cables are wound around a cage and unwinds to be fully extended. At this point the cable drive pulley can rotate independent of the cage. With this system, the tether tension can be measured by a load cell located in the center anchor of the windup stand.
WINDUP CAGE.pdf (64.7 KB)
When you hand launch a kite you instinctively try to maintain tension in the tether as the kite rises. You release the tension when the kite starts to rotate from the vertical. With my concept of a restrained kite, the rotation cannot occur and we are only concerned with tension caused by lifting forces. If the tension drops below a certain level then there is inadequate wind for launch and the kite should be landed. Launching rate is determined by maintaining a minimum tension in the tether.
If we use stepper motors for the wind/unwind cage and the auxiliary tethers then we can ratio in the position of all the stepper motors so that the kite position is controlled at all times. For example step # 3567 on the cage drive corresponds to step # 4382 on the front diagonal tethers and step #4396 on the rear tethers. Steps can be calculated by geometry or by trial and error with an operating system.
Here are some further thoughts on the automatic lever-arm launch system. The kite is spread out over the launching frame and secured by tethers at the four corners in the āparkā position. In moderate to high winds the kite will flap in the wind and may cause damage to the fabric and the bridling over time. We need some method to automatically anchor the kite to the ground to prevent this flapping. If we could have rolling weights on the four auxiliary tethers which could roll towards the kite and weigh it down, then this might prevent the flapping. We could use devices like the LeDuc Line Shuttle to achieve this. https://www.youtube.com/watch?v=jqtRe1DeY60
To ensure that the leading edge of the kite remains anchored to the lifting frame in the āparkā position and doesnāt flutter, we might require a flap which clamps down on the leading edge of the kite and prevents it from moving.
SHUTTLES.pdf (64.6 KB)