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AWE Map by Mind Map: AWE Map
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Welcome to the AWE-Map! The AWE-Map aims to be a complete overview of Airborne Wind Energy (AWE). An AWE system is a machine that transforms the kinetic energy of the wind into electrical energy - with some components of the system being airborne. A broader definition of the term can include other forms of energy output such us mechanical energy for propulsion. The AWE-Map uses a functional model that splits any AWE system into four functional components: 1. LIFT …to stay airborne 2. ENERGY TRANSFER …to bring the energy to the ground 3. BLADE …the kinetic energy in the wind to mechanical energy converter 4. GENERATOR …the mechanical to electrical energy converter The components can be varied in order (GENERATOR before or after the ENERGY TRANSFER) and combined (e.g. a BLADE that produces lift and mechanical energy). On the left the map you find 4 sections: Secondary challenges: Jetpacks and flying cars do exist - but you can not buy them because "secondary challenges" keep them from widespread adoption. If we do not solve these "secondary" challenges for AWE there will be no large scale use of AWE either. Projects: The AWE space gets bigger every year. With players in the scientific, industrial and private space - I try to keep up with "who is doing what" - let me know if your project is missing! Other design decisions How high? How many tethers? Softwing/Hardwing? Many design parameters to chose from... Control: A short time ago flight without a human pilot was unthinkable. Now there are drones everywhere. Controlling a soft kite that is only powered by the wind is still a challenge that many work on. I hope you find the information useful. I am more than happy to receive questions, additions or protests. Plesae post your feedback to the forum! Enjoy!/cb PD: This map originally was created for me personally to get “the big picture” – I therefore copy&pasted some content that I found relevant. If you are the author of any lines quoted here let me know: I am more than happy to provide credit and I am actively working on adding sources where that part of the information is still missing. PPD: My special thanks to Joe Faust whose incredible collection of anything related to AWE at has provided me with hours of reading and a lot of input for this map. PPPD: This is work in progress – if you find any incomplete sentences, thoughts or ramblings feel free to send me an improved version of that text J  


Control system attributes:–Autonomous with ground override–Redundant and fault tolerant–Must automate launch and recovery–Will need to sense operational environment and adapt–Development of control systems for aircraft has become long expensive process–Need for autonomy complicates control system development for airborne wind systems–Having a system that appears to work correctly is only half the battle –must then document, validate, and demonstrate to 3rdparty




Worldwide there are around 50 professional activities -professional meaning either academic or commercial. Depending on where you put the bar there are 10th or hundreds of hobby projects.   Professor Doktor Robert Gasch of TU-Berlin. His advice, proven wise time and time again, is “don’t pay any attention to it until they have Built it, Tested it, and Published the results. [IMG SRC]  (Roland Schmehl) "Airborne Wind Energy", published by Springer in October 2013


Open Source / Free Hardware



Building a completely new type of machine takes a lot of time and money. Many AWE projects will run out of one of the two before building an actual system. If a project does not publish ANY update for more than a year it will be parked on the Graveyard. It will leave the graveyard should we see ANY vital signs. Purpose of this area is not to shame the dead but to make sure knowledge does not get lost.


Some AWE projects never leave the state of CGI (Computer-generated imagery). This category has been created to collect projects that have (not yet) published any pictures/videos of actually build AWE systems. Some of them are worth to keep an eye on - others might go straight to the graveyard category.

Networks/Industry groups and Forums


Secondary challenges

Overspeed protection

Intermittency of wind / Stay airborne

reverse-pumping and KiteLab Illwaco had informally shown that tri-tether-based reverse pumping works at two indoor kite festivals (Long Beach, WA, 2012-13), but the Grenoble work adds a third-party academic case to reverse-pumping, with formal analysis, simulation, and experimental validation. R. Lozano Jr., M. Alamir, A. Hably, J. Dumon: Reverse Pumping: Theory and Experimental Validation on a Multi-kites System Classic kite wind power systems have a great drawback that wind turbines do not have: they cannot stay in the air if there is no sufficient wind. Most of the kite systems need to land when there is no wind, and to take-off once there is enough wind. As these maneuvers happen close to the ground, where the wind is most turbulent, there is a great probability of crashing the kite. Also, ”classic” landings and takeoffs need a landing zone, ground handling or infrastructures such as pylons, thus reduce the advantages of kite systems. A first solution to overcome these drawbacks is to use helium balloons to make kites fly in still air, but balloons have leaks and need refilling solutions. Another solution is to add engines to our kites so that we transform them into vertical takeoff and landing tethered airplanes. There are two ways of supplying energy to the engines, the first is to use electric cables that transmit energy to the kite, and the other solution is to use an embedded battery. For the first solution, the electric cable is heavier than the classic cable and limits the maximum reachable altitude, therefore limiting the maximum harvested energy. The problem of the battery solution is that the vertical flight duration depends on the mass of the battery. In order to minimize the number of landings and takeoffs, we need to have enough energy to remain in flight during the period where there is no sufficient air, or to have enough energy to reach altitudes where the wind can lift the system’s weight. Reverse pumping brings a partial solution to these problems.The proposed reverse pumping method can be decomposed in two phases, the kinetic charge and the potential transfer phases (Fig 2). During the kinetic charge phase, the amount of energy ΔEt will be consumed on the ground by pulling the kite with the rope. As a consequence, the kite will increase its kinetic energy by ΔEc. The gained energy will be transformed into potential energy ΔEp by taking height during the potential transfer phase. At the end of the cycle, the total energy of the kite should remain greater than or equal to its initial value, even in the presence of energy losses ΔElost. The kite’s energy variations obey the following equation,ΔEt =ΔEc +ΔEp +ΔElostUsing this method, the kite can stay in flight even in the absence of wind. The reported study is composed of a theoretical investigation of the reverse pumping, the numerical simulations applied to a twin kites system and finally, the validation of our simulations on our experimental setup

Lightning protection

Nasa's Atmospheric Environmental Safety Technologies Project Atmospheric Hazard Safety Mitigation Lightning & EM Effects Mitigation is developing mitigation strategies to improve aircraft lightning protection designs through passive or active methods. These might be applicable to AWE.


"Icing of flying devices is a serious maintenance and safety concern, and approaches to solving icing for airplanes are significant maintenance and operations expenses by themselves. Further, high altitude devices will often or even usually be flying in below zero temperatures so icing and frost build up will need to be addressed" [Barnard ] "soft kites, naturally shed ice as it forms suspend operation when icing conditions exist at design altitude (an infrequent event in most locations). icing conditions only occur at the thin interface of freezing-thawing" [kPower]

Airspace restrictions

Obstruction Lighting and Marking:On July 31st, Jim Patterson traveled to Griffiss International Airport in Rome, NY to meet with personnel from the New York State Energy Research and Development Authority (NYSERDA), the Griffiss International Airport, and the Northeast UAS Airspace Integration Research Alliance (NUAIR) to discuss the potential testing of airborne wind energy systems (AWES). AWES are wind turbines that float or fly in the air and are connected to the ground via a long tether. The FAA is in the process of developing lighting and marking standards for these unique systems to ensure that they are visible to pilots flying near them, and is interested in working with this team to test prototype marking and lighting configurations that are being considered.


"The scalability of airborne wind energy systems with crosswind wing motion is analyzed. Themain dimensions of AWES are found to be linearly scalable in the first approximation. Thepower grows as a square of the linear dimensions of AWES. Scaling up may provide additionalbenefits, such as lower acceleration of a wing and a tether in a closed loop, decreased tetherdrag when the tether Reynolds number becomes critical, and well known statistical increase ofwind energy density with altitude. Further, the paper shows that at a reasonably high ratio ofthe wing area to the distance between the wing and its ground attachment, the tether dragbecomes significantly lower than the wing drag" Square-cube law is a trap. As a body grows in size, its volume grows faster (cube) than its surface area (square). The mass of a body scales with its volume. The lift scales with its surface area.

Visual Impact

Abstract: In the last decade, conflicts over the installation of classic wind-farm technology have created challenges for visual impact assessment in landscape architecture. Concerns regarding landscape aesthetics have been raised in advanced societies. Among these concerns, high-altitude wind power technology aims to not only sweep much higher zones and benefit from greater wind speeds but also to solve the negative visual impacts on landscape. Several research groups and industrial institutions around the world have been developing a new class of airborne wind energy technologies, including the usage of flexible power kites and balloons.

Land&Airspace use

One of the concerns regarding large-scale AWE deployment of wind energy is its potentially significant land and airspace use.   Landspace use for conventional wind turbine hase been researched. "Excluding several outliers, the average value for the total project area was about 34 ± 22 hectares/MW, equal to a capacity density of 3.0 ± 1.7 23 MW/km2" (Land-Use Requirements of Modern Wind Power Plants in the United States Paul Denholm, Maureen Hand, Maddalena Jackson, and Sean Ong)   "...Wind farms sit lightly on the land, taking up at most 1-2% of the area they cover, leaving the rest  available for farming, hunting, snowmobiling, hiking, grazing or any number of other uses..." [BarnardOnWind 2013]   For Airborne Wind Energy in addition to land use the use of the airspace has to be considered - given the higher operational hight. Wether or not this airspace would need to be restricted or could be shared with other aircrafts will depend on the Complexity/failsaveness and the airborne mass  and velocity.  


Many launching methods used for drones might be applicable for AWE. See Stephan Schnez (ABB) talk "The take-off of an airborne wind energy system" on AWEC2015 for evaluation


AWE needs reliability of an aircraft at the price point of a wind turbine. Reliability is expensive. No Verification Standards for AWE exists. Consider establishment of 1-year and 5-year field tests as important milestones.


Partial failure

System behavior at Extreme events Electrical and control system faults

Other Design Decisions

Number of tethers

Single tethers are advantageous from a tether-simplicity perspective and from a tether drag perspective. One tether requires only a single winch on the ground, and eliminates tether tangle for single wings. Two tethers doubles tether drag. Three triples tether drag. As crosswind solutions are constrained by tether drag, this reduces a physical limit on speed and hence energy. Single tether device, however, require in-air control mechanisms and have reduced inherent safety. Control devices, whether bridle-sited line winches or aileron controls, must be near or on wings with single tethers. These devices require power, intelligence and communication with the ground station to operate. Power requires generation and power transformation or batteries in the air, adding weight, complexity and maintenance. Control intelligence requires fast-processing devices in power-efficient configurations doing sophisticated processing in their air. Communications with the ground station requires wireless or wired communication subsystems and power. All of these add complexity, cost and risk to the in-air device. Tether failure is a constant concern of kite generation devices. If the tether fails near the base, it can cause situations where it is dragged downwind for kilometres. Very strong tethers wrapped around vehicle axles would cause catastrophic crashes. Tethers, especially if conductive, that draped across power lines would cause problems of multiple types. Single tether devices have to rely on the strength of the tether and the passive failure modes of the tethered device to prevent these risks. Multiple tether systems typically put all controls on the ground and have higher inherent safety. Dual tether crosswind systems put all of the controls on the ground in twin winches which makes the in-air device dumb as a box of hammers (and that’s a good thing in this case). The overall complexity of the solution is reduced substantially. The device is inherently safer as the likelihood of both very strong tethers failing simultaneously is much lower than just one failing, so the probability of the device flying downwind dragging the tether is lowered substantially. However, multiple tether systems multiply tether drag. For crosswind systems, dual or triple tethers multiply tether drag by two or three times, limiting speed and hence generation to a greater degree. High-altitude systems are typically posited as single tether solutions.from:

Operating altitute

Cristina Archer’s work: "An important conclusion of this work is that there are many known areas, where strong winds, suitable for AWE systems, blow persistently and/or predictably at the altitudes below 3,000 meters, and below 1,500 meters in some cases."   High-altitude solutions – four to nine kilometres – promise very high wind speed and hence energy. Potential energy increase with the cube of wind velocity, and jet stream winds flow at very high speeds consistently. This makes napkin math high-altitude wind upsides very appealing. High-altitude solutions require in-air generation and extremely long, heavy, conductive tethers (or other non-viable alternatives), and require flight exclusion zones up to passenger jet altitudes. And the jet stream varies. There is no projected solution that appears even close to viable that does not require in-air generation and its compromises. In air generation requires that the electricity get to the ground. The only mechanism which isn’t too lossy and dangerous to be viable is a conductive tether. However,calculations suggest that any conductive tether is too heavy to be lifted by any high-altitude device. Other non-viable alternatives involve EMF transmission of energy — frying anything that gets into the beam or anything on the ground if the beam moves, along with incredibly lossy transmission –, or laser transmission of energy – back to frying anything that gets into the beam. Both require heavy duty in-air technology of great weight and complexity. Nine kilometres is the altitude that passenger jet aircraft fly at. No-fly zones that high exist, but they are for dirigible-based radar systems of strategic national priority. It’s unlikely that no-fly zones would be approved merely for power generation when much simpler alternatives exist. Solutions commonly reference the jet stream as a high-altitude, very energetic and consistent source of wind generation. However, the jet stream varies north, south, east and west by enormous margins over the course of the year and from year to year. No tethered device can guarantee access to the jet stream. Low-altitude solutions have shorter and lighter tethers, even if they are conductive. Makani’s conductive tethers are merely thousands of kilograms in weight for 400 or 1000 meter tethers. This is supportable given the energy involved, although crosswind tether compromises apply. However, low-altitude solutions forego the power potential of high altitude winds and are not substantially advantageous compared to modern wind turbines. Virtually all airborne systems are now targeting under 2000 feet or 650 meters in altitude, in large part due to aviation regulations, but also due to massively multiplying engineering challenges with increasing altitudes. Wind velocity increases as altitude increases. However, the current 150 meter height of mast-based wind turbines capture winds at 80-90% of most low-altitude airborne systems. This means that low-altitude airborne systems provide marginal energy increases over much simpler ground-based devices. This marginal energy increase is trumped by the other compromises. This analysis compares airborne wind energy systems mostly to one another. However, there are two additional major compromises with airborne wind energy systems which are important to draw out to provide a complete picture.   from:

Soft/Hard wing

"Soft kites have advantages of relative cheapness, ease of prototyping, higher crash survival rates and lower crash potential liabilities. Fabric is cheaper to transport and build with than solid materials. It’s fast to stitch together another kite, use kitesurfing kites or have a kitesurfing company build specific kites for you as UDelft does. When fabric hits the ground it crumples into fabric as opposed to stray shards of shattered wing.  Combined with the slower speeds, this increases the likelihood that a fabric wing that crashes can be used again without problem. That said, inflated spars pop, wings rip and battens break or bend. When fabric hits something it crumples. Combined with lower speeds, the likelihood of causing significant damage is reduced substantially. However, soft kites don’t fly as fast, don’t fly in as wide a range of conditions, don’t last as long before replacement and are hard — perhaps impossible — to reliably auto-launch. Lower speed reduces the potential power output for crosswind generation. Reduced viable flight conditions due to less structurally robust wings reduces the capacity factors annually because of weather-related grounding. Reduced life span reduces capacity factors annually due to maintenance-related grounding and increases costs due to regular replacement (balanced by lower cost of the fabric kites). As a data point, the highest quality paraglider wings must be replaced within 400 hours of flight time due to fabric degradation. The last one, auto-launch, is a real problem for soft kites. To launch, a soft kite has to be furled correctly and there has to be sufficient wind to loft it. Given turbulence near the ground and lower wind speeds near the ground, this is a non-trivial (by which I mean very hard) problem. No one has really solved this problem as far as I can tell. The three most complete systems — Skysails, Wind Lift and Kitegen — all require manual intervention and stronger winds near the ground for launches. Kitegen has two or three ideas for auto-launching in lower ground winds, none of which appear to be viable. Hard wings have the advantage of higher speed in the air and with that higher speed comes greater energy potential. Higher air speed comes with airfoil rigidity and reduced drag. Energy potential increases with the cube of velocity of air, so rigid wings have significant potential advantages. However, hard wings require onboard aileron controls, are more likely to break if they hit something and more likely to break the things that they hit. While soft wings can be controlled by dual tethers — although several are not –, hard wings require onboard power and intelligence to fly. This increases complexity and weight in the air. Complexity increases the chances of failure. Weight reduces efficiency. Hard wings, if they hit something such as the ground or tethers of other hard wings, are much more likely to suffer catastrophic failure. Failures which soft wings shrug off turn hard wings into splinters. This requires hard wings to have much more built-in crash avoidance, which increase initial engineering and costs. Hard wings, if they hit something such as people or buildings, are much more likely to cause damage. This increases liability risks, and hence insurance." from Rigid vs. flexible/textile a continuum, not either-or choices... As one example TwingTec uses an inflatable rigid beam to give structure to a rigid wing comprised of very soft materials. As another, many of the pure soft wings have inflatable spars adapted from kitesurfing, or directly use kitesurfing kites. Corwin Hardham | Makani Power Endurance of materials is only one of the reasons why we moved away from fabric structures.  While there is good anecdotal evidence that fabric structures can last, the peer-reviewed, published data on rigid structures provides a much more reliable framework to make estimates of life. Nonetheless, the main reasons why we moved away from fabric structures are: controllability (repeatability), safety and performance.  A few qualitative remarks on controllability and safety: 1) We found curvature control on textile wings was highly sensitive to windspeed and generally completely uncorrelated to control input, and 2) textile wings operating in crosswind flight demonstrate survivability on impact similar to rigid structures.  These observations stem from many hours of flying in a large range of wind speeds from 2-25 m/s.  Making power requires speed and repeatability in control which are two things that rigid structures provide to great extent. In terms of performance, the estimate of wing size required for the MW system that I listed earlier was highly optimistic in favor of textile wings.  The estimate was based on doubling the measured drag of Wing 7 which is a highly evolved and clean airframe.  In 2008, we tested every textile wing that we could find (kitesurfing kites from nearly every manufacturer; custom kites from Pete Lynn, Don Montague and myself; and  bridled ram air kites).  We never measured a wing performance within a factor of 3 of the performance I describe here.  Hence, the 533 m2 is likely a gross underestimate of the scale needed. I recognize that other groups have claimed to have reached better performance with textile wings.  To this, I would welcome a chance to see the power over the full winch out/in stroke.  We were able to easily show very favorable power peaks on the reel-out stroke, but the time and power required reeling back to the same point did not make favorable average power.  Our results were with fully active angle of attack control, fully autonomous (adaptive power tracking) flight control and a brushless winch drive with a high quality gear box.  ---------------------4. Wing Type: Rigid (glider) vs Flexible (kite)This question is open.  Both types can be used, and neither of them has a clear advantage.Parameter \ Wing TypeRigid WingFlexible WingCostHigherLowerLongevityHighUnknownGlide ratio estimate12 (better)6 (worse)Safety on crashUnsafeSafeWing restoration on crashUnlikelyLikelyAerodynamic stabilityStableVariesFlyback maneuverEasyDifficultControl actuatorsPlane-like (more available)KSU + lines (less available)Launch & landingVariesVariesGlide ratio incorporates both wing and tether drag.  The tether drag eliminates most of the rigid wing’s advantage in lift/drag ratio.  An aerodynamically streamlined tether can eliminate most of the tether drag, but such tethers exist only on the drawing boards.  While the rigid wing is less safe for objects on the ground than a flexible wing, it is still much safer than a wing of any kind with onboard generators.It should be noted that there are multiple kinds of the kite wing, and some companies (like TwingTec, Switzerland) propose specialized AWES wings that do not fall into either of these categories. Advantages of flexible structures are: Can crash without having damage to the system More safe to operate for the people on the ground Lightweight Small in volume for transportation Cheap materialsCheap in production Disadvantages of flexible structures are: Shorter lifespan Modeling the aerodynamic behavior is challengingA lower Lift-to-Drag ratio compared to a rigid wing in general  Systems have been developed to increase the rigidity of soft wings eg. by (auto) inflating them:e.g. Kiteboat's kite Inflator:   [IMG Source]


Functional Model

Different models have been proposed for the classification of Airborne Wind Energy Systems. Most of them (e.g. [1]) use the location of the electrical generator ("Ground-Gen" vs. "Fly-Gen") as the main classification criteria. The AWE-Map uses a more generic model by splitting the AWE System into four functional components: LIFT - the part of the system that keeps it airborne. ENERGY TRANSFER - the part of the system that brings the energy to the ground. BLADE - the wind to mechanical energy converter GENERATOR - the mechanical to electrical energy converter In an actual AWE system the components can be varied in order (GENERATOR before or after the ENERGY TRANSFER) and combined (e.g. a BLADE that produces LIFT and mechanical energy). For each of these components many implementations have been suggested. The AWE-Map lists them all - irrespective of their probability of operational success in a practical AWE system or alleged common sense. Since the number of possible combinations and therefore the number of possible AWE systems is too large to test them all a set of evaluation criteria is being suggested to give people interested in the field a more objective way where to invest time and money: Evaluation criteria Efficiency - Every energy conversion leads to losses. The primary energy for an AWE system (kinetic energy in the wind) is free. Why does efficiency matter? A less efficient approach will require a larger system to generate the same amount of electric energy - which leads to higher material cost and land consumption. Reliability - 24/ Complexity Automatability - human labor is expensive in relation to current energy prices. Every step that requires human intervention will increase the cost/kWh and will make the system unsuitable for mainstream adoption and off shore application. Scalability - Square-cube law is a trap. As a body grows in size, its volume grows faster (cube) than its surface area (square). The mass of a body scales with its volume. The lift scales with its surface area. Hence any sytstem that requires to scale up a (solid) body will reach a scaling limit. This limit might be lower than the size of an economically feasable size Mass aloft Durability Ductility - Turbulence matters. The AWE system must be able to accommodate wind variability. Safety - Potential - Scaling limits, low operating altitudes, large land or airspace consumption, limited security lower the maximum power potential of a design Cost - cent/kWh is the ultimate success criteria. This is increased by manufacturing cost, development cost, material cost, maintenance and operating cost, Work in progress: - find quantifiable parameters for each system component and evaluation criteria- rate the proposed components for their suitability for an AWE system [1] Diehl M.Airborne wind energy: basic concepts and physical foundations.In:Ahrens U, Diehl M, SchmehlR, editors. Airborne wind energy Berlin:Springer; 2013.p.3–22 [Chapter1].


The BLADE is the wind to mechanical energy converter. Wind applies a force on a surface, causing motion of that surface. Thereby the kinetic energy of the wind is converted into mechanical energy.  To be efficient a blade must be shaped like an airfoil generating lift while travelling crosswind. The maximum efficiency that can be reached is 59% (Betz limit). See [1][2] or any book on wind power basics for the derivation of these two points. Understanding them is necessary to be able to distinguish between something that moves in the wind and an efficient blade and to be able to identify untenable claims that are sadly too common in the entire space of wind energy. [1] ROTORS for WIND POWER, P.T. Smulders, University of Technology, Eindhoven[2] Fundamental and Advanced Topics in Wind Power", book edited by Rupp Carriveau, ISBN 978-953-307-508-2, Published: July 5, 2011 Wind Turbines Theory - The Betz Equation and Optimal Rotor Tip Speed Ratio Magdi Ragheb1 and Adam M. Ragheb2

Energy transfer

Energy transfer: The transmission of the mechanical power derived from the wind  to the ground.   A big challenge - if not the biggest -  for Airborne Wind Energy is to find an efficient way to get the energy down to the ground. There is a huge number of possible options for such long distance energy transfers - most of them have been proposed in one form or another for application in AWE. I have compiled what I think is a complete list and linked to either the first source I could find or the best example/visualisation of the method. For some methods I could not find a source yet - they have been added for completeness. Next exercise will be to eliminate some of the options and to find the ones with the best potential. To do so I will use two criteria - Weight Efficiency (kg/kW*m) - Transmission Efficiency (power received/power transmitted) Other criteria will be: - Availability (nanotubes and gravitational waves I am looking at you!) - Cost - Airspace streamtube efficiency - Land footprint efficiency - Density of operation Some methods are already being tested for AWE. Others have been used, developed and tested for other technology areas that require long distance energy transfers.


Lift: The force that keeps the Wind Energy Converter airborne. "In principle, any Wind Energy Converter can be lifted into better wind by cheap lift." Dave Santos "Lift is expensive" Your airline    


Generator: Mechanical to electrical energy converter