This could perhaps be a classification criterion. Or simply an attempt to see what could be productive and conversely what could lead to a dead end, knowing that the estimates can be contradicted.
I cited some examples of @dougselsam 's analyzes. In my opinion crosswind reeling and fly-gen AWES produce (or not) by themselves. These methods are far (in spite of the explains by Peter Jamieson of the secondary rotor concept in his book page 128, but secondary rotors (fly-gen style) are not used on current HAWT) from the techniques used and proven in the world of wind energy and in particular the iconic three-bladed wind turbine (HAWT).
The same would apply to AWES integrating VAWTs, as less efficient wind turbines.
If we limit ourselves to AWES having integrated a conventional wind turbine, I only see Altaeros, or maybe Kiwee. But:
It will be noted that the criticism does not relate to the turbine itself, which is therefore a classic HAWT, but to the aerostat part. Maybe it’s finally less serious.
This brings us to the question of the topic: are we more right in wanting to integrate or suspend a conventional HAWT, a proven technology, rather than choosing more specific techniques like crosswind flight in reeling or fly-gen mode?
In the first case we will seek maximum aerodynamic and aerostatic lift to lift a considerable mass with the least possible risks, and for continuous production with wind turbines that we already know.
In the second case we seek to limit the equipment in flight in relation to the power produced by using crosswind flight the most often, with in return obstacles such as reliability, duration and continuous operation, etc.
In the first case we come from existing HAWT to make them fly. In the second case it is quite something else: we enter into some specific AWE vocabulary, ignoring HAWT.
Here is a fairly long video in French, which presents a guided tour of a 750 kW wind turbine.
It’s quite informative to start understanding how it works all the time. All the kinetic energy conversion elements are located in the nacelle, but the electrical equipment for grid adaptation is found at the foot of the tower.
Now you want to send this turbine to higher altitudes to harvest more powerful and consistent winds.
If you use Altaeros, you will need to have approximately the same ratio of balloon diameter to turbine diameter, thus several times. Our 750 kW rotor is approximately 50 m in diameter. The balloon should be around 200 m in diameter, also knowing that a large mass must be lifted safely. As it is a fly-gen, certainly static but fly-gen nonetheless, the tether must be electrified. Altaeros blimp shape has a great advantage of protection of the turbine aloft, but take a lot of material in relation to the volume.
Another aerostat, but not tested for my knowledge, is planned to carry two conventional wind turbines.
In both architectures the wind turbine is not suspended, which would be detrimental because of the pendulum effect on such an imposing mass (and which is not good for the efficiency among other issues), and also because upon landing the wind turbine would be the first element to touch the ground, which would not be good for its safety.
We therefore have particularly complex solutions to implement, knowing to what extent a heavily loaded aerostat can be vulnerable during takeoff and landing. But these are, to my knowledge, the only solutions implementing already well-known HAWTs, although certainly under different conditions.
Thanks Pierre for explaining that AWE is still exactly where it was 15 years ago: Nowhere. (“Flygen? Skygen? Groundgen? Ballons? Kites? Airships? Hard wings? Soft wings? Drag-based? Lift-based? Not even knowing what drag-based or lift-based means?” And now, “spinning sausage? Helium? hydrogen? Hot air? Nitrogen? Seriously??? Nitrogen??? Pivot to Wifi? Pivot to flying taxis?”)
Land of the Lost. None of the endless promises have come true. Still like a blind guy trying to figure out where he is, in a dark room. Or a few thousand blind guys… and girls… with an H.R Department… Renting office space… Taking group-selfies for Mom to look at… With another new test facility finally approved in Ireland… Flailing, flailing, and endlessly failing… Still trying to understand even the most basic factors it would face if ever actually developed to a commercial level.
This is something positive. Indeed, AWE is a remarkably stable sector.
And perhaps this topic can help to provide an explanation for this stability. On the one hand, conventional HAWT have the right conversion systems, but they are far too heavy to be aloft. On the other hand what is lighter and good for AWE, are the less good conversion systems which are intermittent, then there are all the intermediaries.
When we see the video above we measure the gulf between AWE and HAWT.
HAWT have the best possible efficiency, are reliable, are fixed (without the insane risks of rapid permanent trips to who knows where at the end of a 1 km tether). Certainly HAWT can be a little short for very high altitude winds, but are experiencing exponential development all over the world, while the development of AWE still has the virtue of stability, failing that of their flying devices.
Researchers underestimated the obstacles to AWE and were perhaps wrong to strongly and unanimously praise a system that ultimately failed, taking the entire sector with it.
But let’s not forget that the Phoenix is ​​reborn from its ashes. Who knows if one day a brilliant individual _ not a team, not human resources, just an individual _ will not find the keys to the sky for AWE.