Terminology, Acronyms


  • flygen
    aka.: makani-style, turbine on a kite
  • groundgen
    Any system where the generator isn’t airborne
  • yo-yo
    aka.: pumping mode, reel-out/in, kite reeling
  • torsion-transfer
    transferring the torsion to a generator on the ground
  • ropedrive
    Using a circular rope in the way of a belt to transfer power to the ground.


  • awes - airborne wind energy system
  • aoa - angle of attack

A word for the yoyo, jojo, yo-yo, jo-jo, winch, systems like KPS, Enerkite, Kitepower B.V., Ampyx Power etc.

  • Yoyo
  • Jojo
  • Winch System

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Rod swears it’s yo-yo

A word for rotary, torque transfer systems like @Rodread s Daisy, Doug Selsam’s Sky serpent etc.
General term for anything that transmits torque via shaft torsion.

  • Torsion-transfer
  • Whirlwind of the gods (poll needed more options but I can only think of one)
  • Glorious superior system (one more option to activate multiple choice)

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[Edit: Damn, poll options cannot be added, rendering this poll useless.]

Generator in the air like Makani has.

  • Airgen
  • Flygen
  • Makani

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I would say the most important distinctions are:

Crosswind vs downwind (this is not really an issue as all modern AWE is crosswind)

Lift vs Drag based

I thinks @PierreB mentions this in the Betz’ limit thread. Some AWE utilize the lift force to generate tension that is harnessed as rotation on a ground based winch. Others utilize a force acting mostly in the drag force direction. The power may be harvested by either torque transfer or on-wing generation.

To further classify the systems we have already seen:

Lift based:

  • Ground based winch generator (Yoyo)
  • Ground based torque wheel (?)
  • Ground based vessel/car pull

Drag based:

  • On-wing generator (Flygen)
  • Torsion transfer ground generator

Further classification could be in the number of generating wings

  • Single
  • Double
  • Multiple, single layer
  • Multiple multi layer

Another classification to be made is

  • Self erected
  • Supported (eg canopy mesh or single lifters)

I believe Yoyo is the correct spelling https://en.wikipedia.org/wiki/Yo-yo

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I reject the term drag/ drag power being used in this way.

I don’t have access to the paper to see how exactly how they use it.

The second type is also utilizing lift. Else it could not fly crosswind. It is just that the power is harvested by generating drag by flygen. The distinction Lift-based and Drag-based cannot be made, as all the systems you mention are crosswind-systems utilizing lift. As I am using the term the only Drag system would be not a crosswind system but something that works like a parachute or sky-anchor.

The distinction can be made by the way in which power is taken from the system to generate work or electricity.

  • Slowing downwind movement (yoyo)
  • slowing crosswind movement (flygen, torsion-transfer)

The expressions “drag power and lift power” used in “The Betz limit applied to Airborne Wind Energy” paper come from “Crosswind Kite Power” (Miles L.Loyd) seminal paper (http://homes.esat.kuleuven.be/~highwind/wp-content/uploads/2011/07/Loyd1980.pdf), page 108:
“When a cross wind kite pulls a load downwind, as described
above, it is essentially the lift of the kite that acts on the tether
to produce power. That mode of operation may be called lift
power production. Power can also be produced by loading the
kite with additional drag. Air turbines on the kite result in
drag power.”.

  • Lift (tension, non-stationary) power systems use tension to unroll the winch during reel-out power phase. Lift power systems (yoyo) generate a discontinuous power in two phases: reel-out (power phase), and reel-in (recovery phase).

  • Drag (torque, stationary) power systems (flygen and also HAWT and other rotating systems) generate a continuous power.

But these “lift” and “drag” terms (that are used in scientific literature) can lead to some confusion.


Drag-loading is much clearer.
But using lift-loading doesn’t make sense as the direction would be wrong. Would have to be counterlift-loading or something.^^
I think having two proper terms that aren’t just “lift” or “drag”, but “drag-loaded” and “X” will be very useful.

[Edit: The daisy-system is loaded in drag-direction but isn’t directly loaded by drag. That complicates finding good terms. Also with flygen seeing the turbine not as part of the awes it is clearly drag-loading, but when zooming in on the turbine, it isn’t drag loaded either but loaded in direction of the drag by the electrical generator ]

A HAWT becomes a drag device just by it being off the ground? Aren’t all HAWTs off the ground?

Yeah that’s why we should use “drag-loaded” instead of just “drag”.

That’s also a term we should talk about. I would not regard alll awes as turbines. The definition: " A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work." could fit all awes. But with yoyo it isn’t the rotation from which the energy is extracted. The kite could just as well fly linear. I would suggest to use the ter turbine only with drag-loaded systems.

Another suggestion: Distinction between:

  • Crosswind-loaded (CWL)
  • Downwind-loaded (DWL)

That would make daisy and makani clearly cwl and yoyo clearly dwl.
However the directions are wrong, at least for downwind. The load is applied upwind…

In this paper we revisit the modeling framework used to derive the Betz limit of power extraction from the wind based on linear momentum theory. One of our contributions is to suggest that the Betz limit of 16/27≈59% should in fact hold true for any device that harvests power through drag or torque in a horizontal-axis rotational motion perpendicular to the wind field, which is not only the case of conventional wind turbines but also of Loyd’s drag power Airborne Wind Energy (AWE) systems. Another contribution is to show that Loyd’s lift power AWE devices during the reel-out phase can harvest up to 4/27≈15% of usable power available in the wind, i.e. exactly 1/4 of the theoretical limit of the horizontal-axis turbines and AWE drag power systems with ideal airfoils. Moreover, in order to operate at such limit, AWE lift power systems must also extract from the wind an amount of drag power that is equal to the reel-out power. These claims are supported by physical principles and mathematical formulations.”

HAWT, rotating AWES, AWE drag power systems (Makani-like): all use torque (even Makani of which turbines onboard are secondary turbines) and are stationary systems as their respective swept area is stationary.
Lift power systems are tension (or force or traction) systems: they use tension (or force or traction) and are unstationary systems.
So there are some possibilities: torque vs tension, or stationary vs unstationary…
But these scientific papers are already written, so changing terms would add confusion.

Well a tension or force or traction system also generates torque on the winch.^^

Is there a good consensus on terms?


Not sure. Perhaps the simplest would be: yoyo vs the others.

Seeing that the Loyd paper was very early, we should stick to whatever naming is in there.

To mangle everyone’s noodle…
A Daisy needs lift tension to transfer drag load.

The torsional shape (amount of twist / length) of a torque transfer network “shaft” …
Which a Daisy kite relies on for torque transfer … That torsional shape, relies on having lift force to keep the lines from being overly twisted by pure drag force.

I drew the difference in its own thread:

I find the Acronym AWES annoyingly cocksure.
… Like we’re awesome.
We have a hell of a long road before we can declare awesomeness.

I quite like AEIOU for my
Airborne Energy Investigations Outdoors Unit
oh my
Or Kite Network Airborne Wind Energy KNAW sounds much more gnarly and power-winning

Haha. AWES for awesome is the reason why this is so useless as a tag on twitter. That’s originally how I came up with #awesystems. Wanted to make that the go to hashtag for awes. Often times people use #wind #energy #systems or #wind #drones or something. That’s not something one can easily search for and get just results on awes. Now that I’ve named my twitter handle and the website the same it has become a bit of a brand and is thus useless as a neutral hastag.

I like how AEIOU is all the vocals.^^ Just make up an acronym and come up with the name later.