Shouldn’t we design AWESs capable of withstanding all kinds of winds, even the strongest? Indeed recovering an AWES can be long and difficult.
Current wind turbines stop at 25 m/s. Doubling this value while harnessing full power can be an interesting challenge. Is it really possible?
Hi Doug, I plead guilty. The moderators have nothing to do with this new topic for now.
I think you often mention the overspeed problem, so a topic dedicated to this problem might be helpful.
Several AWES could be examined as the overspeed issue can be different according to their features: ground-based generator or fly-gen, soft or rigid wing, pull or rotation, single unity or network of kites…
That said I can agree that an excess of division of subjects is not necessarily desirable.
I agree that we should develop a system which can safely operate at higher wind speeds. Is it true that smaller turbines can operate at higher wind speeds without damage? Operating small turbines at high speed is advantageous because cable drives operate better at higher speeds and gear reducers may not be required.
I do not think that launch and land will take a long time. This is particularly true if we use an accelerated windup system like the caged cable windup I proposed. If the winding speed is 10 met/sec then we can retrieve a kite from 1000 meters in less than 2 minutes.
Most kite systems rely on adapting to flying high or to the side of the wind window when the wind becomes too strong to allow the regular pattern flight.
With Daisy kite turbine types there are a few options to reduce kite speed and forces.
The main overpower smoothing feature is in the rotor blades. The simple blades just flex and spill wind at the tips.
Additional ring depower actions …
There’s scope to trial mechanisms which pitch and or bank the blades under pressure. There’s also a potential for active ring diameter adjustment.
Another tested option is…
There’s a balance with the lift kite tension and the backline holding the rotor down to set elevation angle. Usually releasing the backline raises and depowers the rotor. The backline can also be brought around to yaw stall the rotor. This has to be done gradually and using a wide arc, as when you travel the backline around, lift tension is transferred from routing more through the transmission to running more down the backline.
Slowing and stalling the rotor by torque loading is possible. There is a balance point near 0 rpm where the torque of the rotors can be less than line and system drag … but again this slowing down via torque loading has to be done carefully.
Looking ahead at weather patterns and landing. Probably the better option for now.
Hi Doug, I don’t think overspeed protection is the same issue for the fixed elements of a ground-based wind turbine and for AWES where we can directly act on kites being able to be depowered.
Adjusting the blades to depower them is already the main method of overspeed protection. On-paper would-be designers tend to only operate in “Goldilocks” perfect winds, not too strong, not too light, just right…
VERY STRONG WINDS HERE TODAY
Symptoms:
Sand in your teeth
Your face being sandblasted by sand and small rocks
concrete tiles blowing off roofs
difficulty walking upwind - lift your leg and it is blown back
We went outside to water some trees. Had to come back inside after having our faces sandblasted. Cold too - thick air. Dogs also insisted on coming back inside. I would feel sorry for any kite trying to fly in this. It would end up miles away, destroyed. Since we’re at 3600 feet elevation (1000 meters+) it is like living in the sky. Woke up to see low clouds flying by at freeway speeds at dawn. Good luck flying anything in this shit! 
I wonder how long time a rigid AWES could fly crosswind before it crashes. Would it have time to land in the event of an alert?
Various articulation methods have been trialled to prevent overspeed on “normal” wind turbines
However articulating in the plane of rotation about their root isn’t really an option as that’s how they deliver power.
To understand this have a look at a flying car wing
(I know)
Not going to work on a “normal” wind turbine
But where a blade doesn’t fix to it’s plane of rotation at the axis… Like on a ring rotor… Daisy Kite turbine
This sort of swing wing geometry blade fold away is legitimate.
The pivot can also be in the middle of the blade to bring both inner and outer tips to the ring.
How light can it be made?
Let’s say we were operating offshore and worried about a predicted extreme wind event causing overspeed… And staying up wasn’t an option this time…
Would it be better to retract to a base station 5m above the surface (maybe under a cowling/sheild)
Or would it be better to submerge your AWES in tidal water (maybe by having a rigid porus wing) but going deep enough to not be bothered much by waves?