Up where the kites fly - the beam

An interview with @rschmehl

Good questioning.
Not the sales friendly discourse of mass media.


Detailed and useful indications from @rschmehl, of which I quote some extracts:

There have been attempts to develop a kite that flies circular or figure-eight-shaped patterns all by itself without any control. This is theoretically possible, but difficult to implement in practice because the wind always fluctuates in magnitude and direction and varies in altitude. Therefore, all current prototypes have an automatic flight control. We developed and demonstrated automatic flight in Delft back in 2012.

The ground station is the most expensive component of the kite power system, the generator is also located there, but in terms of new technological developments, the ground station is not the highlight. The aircraft, i.e. the kite, and the control of the kite are more the focus of innovation. I would say that the automatic flight control of the kite is the key enabling innovation for airborne wind energy.

Rain and snow, for example, are easy to handle. In theory, even strong winds can hardly harm the kite because the flight maneuvers can be stopped which decreases the aerodynamic load on the kite. One problem, however, are thunderstorms. Lightning strikes are a problem for the system, especially if the tether is wet and conducts electricity. Therefore it is better to haul in the kite during thunderstorms.

We are currently researching how to place several systems next to one another. The tethers shouldn’t tangle with each other and the kites should not collide. Plans for entire kite parks have yet to be worked out, except for theoretical studies.

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Differentiating Wind Energy from AirborneWind Energy, I will add this from the same publication:

Conventional blade tips of towered wind turbines reach heights of up to about 200 meters, with the largest turbines reaching even 260 meters. Although these turbines are getting bigger and bigger there is a physical limit for towered systems. Airborne wind energy systems are much more variable, i.e. can be operated with tether lengths of up to currently 600 meters. Technically it would be possible to harvest energy even higher, however, this gets much more complex because the kite is further away, the visual contact is gone, the tether dynamics become more complex, and there is also a higher aerodynamic drag on the tether; all of this has a negative effect on performance.

In addition, the airspace for normal air traffic at our first test site near to Leiden, the Netherlands, begins at a height of 500 meters; To operate the kite in this airspace, there are not only technical but also increased legal hurdles requiring different permits.

Sounds like a flashback from 14 years ago.