Windswept has been working on developing an automated launch system for 10kW kite turbines.
The basic concept was, a device with a winch and a mast would replace the work I used to do in launching and recovery - downwind of the ground station, at the head of the turbine.
A bold plan for a tiny company.
In planning this automation we carefully pruned the test requirements to make a minimum viable test rig.
This meant - staying with our initially very successful - static lifter and kite turbine combo.
10kW is a big step up from 1.5kW and we wanted to keep the cut in low for valuable yield.
Automating launch of KAP kites has been going OK
We also got some basic steering types tested (more on that)
However, turns out that static KAP lift kite line tension and angle in low wind is less impressive than we’d believed. Too much of our prior data was from PLK SSSL 1.8m kites or KAP kites in higher winds.
This means the largest size of Kite Turbine we’ll be able to fly from this configuration (in this form) is ~6kW. Given the extra expense and land use of the Backline handling robot / launcher approach … doesn’t look like the system would be mass market viable. We were aiming for a 20kW product after the 10kW tests…
Is that the end of exploration into static lift kite supported kite turbine combos? - No
Calculations were based on single rotor systems with huge TRPT safety margins.
Calculations were based on scant test data of lifter performance so far.
Many small systems concepts (up to 6kW) may well have value in some markets.
What else is there?
Active lift - Looks really promising. Given what we know of other AWES line tensions
Those kites could support some impressively large kite turbines.
Several other concepts
I’m not going into a lot of detail here - we still have a lot of detail to report to funders first.
Just don’t want @dougselsam to think we’re going quietly away into the night.
Kite Turbines are still the big thing
I’m a fan of the simplest workable solution
If you’re looking to scale & weighing up active lifter control vs active rotor control on a kite turbine
…
Lifter control has already been proven … That’s effectively what yo-yo kites do already
Props to W&I for sharing concept problems. This an example for the rest of the industry. And also just a serback, not a showstopper this time.
I’ll brainstorm some options
Better lifter kite with lots of depower, maybe two line power control
Movable lifter increasing apparent airspeed on the kite. This causes the lift to be more downwind and unstable though
Kite trains
Active stering like «The Pyramid» on the blades themselves. Steered either from ground, on the kites with powered electronics or maybe even passively using weights
How much would you need to decrease the capacity factor to be able to get to 10-20kW with static lifters? Or how long would the lifter kite line need to be to get the capacity factor up?
Looking into the potential - Still doubt it’s very scalable though
Yep, bigger better robo-lifters, being more active will get more tension and are very cool looking. With plenty of lift line length the movement would have less effect on the turbine head position… but the pay off is more drag and more handling on the ground, more complexity and harder low wind launching for a given lifting kite area.
Do-able, A lot of mechatronics to develop for connecting multiple devices to the line
In giant radius systems this seems more sensible, but at small scale rotation speeds, that’s a whole lot of actuation to keep reliable
I haven’t seen your back bot, but I assume it includes a winch. If you then also have a way to periodically stop the winch, or also if you don’t, you can clamp the kites to the lifting line. Then in lower winds perhaps you’d space out the kites so they all see clean winds at altitude, and in higher winds you’d do the opposite, or whatever is best. One idea would be to also clamp the vase to the line and also lift it with some of the kites still inside in higher winds. If the wind speed changes you’d land and load a new profile.
I don’t know if this is simpler and cheaper though, if ArduPilot for example now or in the future would be able to keep a smart rotor in the air.
Since there was only one turbine and one lift kite…the Backbot used a simpler “connection” method
The main lifting line runs through large fairleads on the mast. There’s a peg on the lift line locates into a smaller fairlead at the head of the turbine.
The head of the turbine is normally held in a cleat at the head of the mast until enough lift line is released. Reverse for landing