ChapterPDF Available


Safety is a major factor in the permitting process for airborne wind energy systems. To successfully commercialize the technologies, safety and reliability have to be ensured by the design methodology and have to meet accepted standards. Current prototypes operate with special temporary permits, usually issued by local aviation authorities and based on ad-hoc assessments of safety. Neither at national nor at international level there is yet a common view on regulation. In this chapter, we investigate the role of airborne wind energy systems in the airspace and possible aviation-related risks. Within this scope, current operation permit details for several prototypes are presented. Even though these prototypes operate with local permits, the commercial end-products are expected to fully comply with international airspace regulations. We share the insights obtained by Ampyx Power as one of the early movers in this area. Current and expected international airspace regulations are reviewed that can be used to find a starting point to evidence the safety of airborne wind energy systems. In our view, certification is not an unnecessary burden but provides both a prudent and a necessary approach to large-scale commercial deployment near populated areas.
Chapter 29
Current and Expected Airspace Regulations for
Airborne Wind Energy Systems
Volkan Salma, Richard Ruiterkamp, Michiel Kruijff, M. M. (René) van Paassen
and Roland Schmehl
Abstract Safety is a major factor in the permitting process for airborne wind en-
ergy systems. To successfully commercialize the technologies, safety and reliability
have to be ensured by the design methodology and have to meet accepted standards.
Current prototypes operate with special temporary permits, usually issued by local
aviation authorities and based on ad-hoc assessments of safety. Neither at national
nor at international level there is yet a common view on regulation. In this chapter,
we investigate the role of airborne wind energy systems in the airspace and pos-
sible aviation-related risks. Within this scope, current operation permit details for
several prototypes are presented. Even though these prototypes operate with local
permits, the commercial end-products are expected to fully comply with interna-
tional airspace regulations. We share the insights obtained by Ampyx Power as one
of the early movers in this area. Current and expected international airspace regula-
tions are reviewed that can be used to find a starting point to evidence the safety of
airborne wind energy systems. In our view, certification is not an unnecessary bur-
den but provides both a prudent and a necessary approach to large-scale commercial
deployment near populated areas.
29.1 Introduction
Due to the emerging interest in airborne wind energy (AWE), a considerable number
of prototype installations is approaching the stage of commercial development. As
Volkan Salma ·Richard Ruiterkamp ·Michiel Kruijff
Ampyx Power B.V., Lulofsstraat 55 Unit 13, 2521 AL The Hague, The Netherlands
Volkan Salma (B)·M. M.(René) van Paassen ·Roland Schmehl
Delft University of Technology, Faculty of Aerospace Engineering, Kluyverweg 1, 2629 HS Delft,
The Netherlands
704 Volkan Salma et al.
consequence, operational safety and system reliability are becoming crucially im-
portant aspects and it is evident that a certification framework addressing safety and
reliability of airborne wind energy systems will be required for a successful market
introduction and broad public acceptance.
Compared to conventional wind turbines, AWE systems operate at higher alti-
tudes and for most concepts this operation is not stationary. Because of their sub-
stantially larger operational envelope the interaction with the aviation system is po-
tentially stronger. For these reasons, AWE systems introduce risks to third parties
in the air and objects on the ground. Thus, besides addressing the safety issues for
wind turbines, such as the risk of lightning or fire within the equipment, additional
considerations are required for managing the aviation-related risks.
The main system components are one or more flying devices, one or more tethers
and the energy conversion system, which can be part of the flying device or part of
a ground station. The flight control system can be either part of the flying device, a
separate airborne device or part of the ground station. A thorough classification of
implemented prototypes is provided in [2]. Although existing standards can be par-
tially applied to some of the components, such as the low voltage directive (LVD)
2006/95/EC for electrical installation, and machine directives 2006/42/EC or IEC
61400 for wind turbines, there are no standards for the tether and the flying devices.
This study investigates the applicability of existing rules and standards whose objec-
tive is to manage the aviation-related risks. In essence these standards define the ac-
ceptable risks to other airspace users or to people and property on the ground, often
denominated as third-party risk. The aim of this chapter is to provide an overview
of the current situation of AWE applications from the aviation perspective and to
outline a permitting and certification approach for different types of AWE systems.
Ampyx Power is one of the early movers in this area and is currently pursuing
with the European Aviation Safety Agency (EASA) the certification of an utility-
scale, grid-connected rigid glider [33–35, 44]. It is the aim of this chapter to po-
sition the experience of Ampyx Power in the broader context of commercial-scale
AWE systems of any design. We limit ourselves though to systems whose opera-
tion requires permitting by aviation authorities and takes place near populated areas
and/or critical infrastructure. In other words, we consider only deployment scenar-
ios which create an actual safety risk. We assume that the commercial operations for
which a permit is sought take place initially over land restricted to qualified person-
nel. Our focus is on the European regulatory framework and on those AWE systems
for which the current unmanned aerial vehicle (UAV) regulations seem most appro-
priate as a starting point. We merely provide the basic context for other cases.
At the Airborne Wind Energy Conference 2015, Glass mentioned the unique
challenge of airborne wind turbine (AWT) certification because of the combined el-
ements of wind turbine together with aircraft and the additional tether considerations
[20]. In addition, he suggested a unified framework for the certification of AWTs.
This framework starts with reviewing the existing standards in related sectors, in-
cluding wind turbine standards and aviation standards. Then, identification of the
AWT operation regime is required to see what must be addressed in the standards.
Afterwards, a conservative gap analysis has to be performed for identifying the ar-
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 705
eas that are not adequately covered by the standards. Lastly, new requirements have
to be developed to fill the gaps. Glass recommends collaboration with the standards
developing organizations through the entire standard making process.
At the same conference, Ruiterkamp provided an overview of existing and ex-
pected rules and the standards for ensuring safe operation of AWE applications [44].
He further described possible risks introduced by AWE systems and supplemented
his study with the expected legislation for a rigid wing concept.
Langley investigated AWE systems from a legal perspective [36]. In this study,
he introduces the environmental impacts of AWE systems and the current legal land-
scape. An early mover in the US, Makani Power, which was acquired in 2013 by
Google and is currently one of the “moonshot” projects of the Alphabet subsidiary
X, has published a detailed document about the operation of an AWE system [21],
responding to a “Notification for Airborne Wind Energy Systems (AWES)” issued
by the Federal Aviation Authority (FAA) [17].
The chapter is structured as follows. Section 29.2 describes the commonly used
terms in the study such as “regulation”, “certification” and “flying permit”. Sec-
tion 29.3 provides an overview of the flying permit status of current prototypes to
grasp the variety of architectures currently considered. The information has been
collected by means of a survey and reveals that each architecture faces its own spe-
cific safety challenges requiring a tailoring of the mitigation measures. In Sect. 29.4,
we start to explore the perspective for a large-scale deployment of such prototypes,
and for this, the place of the AWE applications in the airspace is studied. Possible
interference between AWE systems and current aviation activities is described. In
Sect. 29.5 we introduce the civil aviation authorities which would most likely be
important in the regulation making process. We then highlight in Sect. 29.6 three
possible starting points to obtain operation permits for AWE prototypes. The first
one is unmanned aerial vehicle (UAV) registration, the second one is air navigation
obstacle registration, the third one is tethered gas balloon registration. Concerning
UAV regulations, the current certification framework and future expectations are de-
scribed, highlighting also different views of aviation authorities on tethered aircraft.
Concerning air traffic obstacle regulation, ICAO rules for air traffic obstacles which
might be applicable to AWE applications are referenced. Lastly, yet importantly, we
assess in Sect. 29.7 different permitting and certification paths for AWE systems in
the light of current regulations and future projections.
29.2 Concepts of Regulation, Certification and Flying Permit
As a starting point we describe how regulation, certification, permitting and stan-
dard relate to each other for the European context. The relevant overarching Eu-
ropean laws are the Regulation (EC) No. 216/2008 [12], which distributes the re-
sponsibilities between EASA and the national aviation authorities (NAA), defines
the mechanism of certification and lists the high-level airworthiness requirements,
as well as Commission Regulation (EU) No. 748/2012 [10], which implements Part
706 Volkan Salma et al.
21, the globally agreed requirements for certification in aviation. The Certification
Specification (CS) and Special Conditions (SC) are type-specific soft regulations for
airworthiness (incl. safety through the respective articles 1309), and suitable starting
points for tailoring. Certification is done with respect to a certification basis agreed
between applicant and aviation authority: a selection and tailoring of the appropri-
ate CS/SC and definition of an acceptable means of compliance, using e.g. ARP/ED
standards 1. A Permit to Fly is given by the NAA for small, experimental or develop-
mental systems. The necessary airworthiness and safety evidence shall be approved
by a certification body or a qualified entity (this may be as part of a certification
trajectory, but does not have to be). Key question addressed here is: can the system
be flown safely? The NAA in addition considers local constraints and operational
29.3 Current Operation Permit Status of AWE Systems
Airborne wind energy is currently in the development and testing phase. In this
phase, companies and research groups conduct their tests with special permissions.
Most of these permissions are issued by local civil aviation authorities. AWE ap-
plication examples from different high-level architectures are shown in Table 29.1.
Comprehensive information for each architecture and up-to-date implementation
details for practically demonstrated AWE systems can be found in [2].
To understand the current status and extent of these exemptions, a survey was
conducted in the context of the International Airborne Wind Energy Conference
2015 [45, p. 9]. Companies and research groups around the globe were invited to
provide the technical specifications of their prototypes and information on the flight
permit. The analysis of this data shows that current prototypes have a small airborne
Ground generator, Ground generator, Onboard generator,
single tether multiple tether single tether
Flexible Wing TU Delft [47] Kitenergy [38]
Politecnico di Torino [13]
SkySails Power [19]
Kite Power Systems [30]
Rigid Wing Ampyx Power [46] TwingTec [37] Makani Power [52]
Kitemill [31] EnerKite [1] Windlift [54]
eWind Solutions [32]
Other Omnidea [43] Altaeros Energies [53]
Table 29.1 Selection of current AWE applications and architectures. System concepts with on-
board generator (as a primary means for electricity generation) and multiple tethers are not known
to the authors
1The acronym ARP stands for Aerospace Recommended Practices and the acronym ED stands for
EUROCAE (European Organisation for Civil Aviation Equipment) Document.
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 707
Organization Prototype category SizeaTether# Weight (kg)
TU Delft Flexible wing / generator on ground 25 m21 20
Kontra Engineering Flexible wing / generator on ground 2.5 m22 0.5
Kitemill Rigid wing / generator on ground 3.7 m 1 4.5
Windswept and e2 m2driving
Interesting Ltd Flexible wing / generator on ground e3 m2lifting Many 1.6
FlygenKite Flexible wing / generator on ground 2 m Many 0.2
Flexible wing / airborne generation
Kite Power Systems Flexible wing / generator on ground 7 m 1 45
Kite Power Systems Flexible wing / generator on ground up to 40 m 450
EnerKite Semi-rigid wing / generator on ground 11 m 3 20
Ampyx Power Rigid wing / generator on ground 5.5 m 1 35
Federal University Flexible wing / no electricity gen. 3 m21 2
of Santa Catarina (flight control purposes only)
kPower Rigid wing / generator on ground 1–300 m2Manyb0.5–100
Flexible wing / generator on ground
Rigid wing / airborne generation
Flexible wing / airborne generation
Altaeros Energies Lighter than air / airborne generation N/A 3 N/A
TwingTec Rigid wing / generator on ground 3 m22 15
am2for projected wing area, m for wing span
b3D lattices form for topological stability
Table 29.2 Reported AWE prototypes in the certification survey
mass, occupy only a small volume of the airspace and generally have human pilots
in the loop or supervising the system. They are operating in a selected safe area to
mitigate the risks to third parties. It is expected that the final commercial products
will be significantly larger with higher airborne mass, will occupy larger volumes
of the airspace and will ultimately have to comply with international airspace regu-
lations. Conference participants were asked to fill out a web-based survey. Among
the responses from 26 different organizations, 15 different AWE prototypes are re-
ported. Table 29.2 shows the main properties of the reported prototypes. According
to the responses, 10 out of 15 prototypes are formally registered with a civil cer-
tification authority. Three systems are registered as an air navigation obstacle, 6
systems are registered as unmanned glider or tethered kite. The remaining system
holds an environmental permit (Dutch: “omgevingsvergunning”) from the respon-
sible local municipality. A selection of collected flying permit data is provided in
Table 29.3. Results show that there is currently no consensus among the certification
authorities. For technically similar concepts, some aviation authorities require per-
sonnel training, while others do not impose this requirement. Some prototypes need
licensed personnel to operate. While most of the prototypes are allowed to operate
at night, some can operate only during daylight hours.
708 Volkan Salma et al.
Organization Operation Issuing Validity Validity Permitted (P)ilot/op. Required Other
permit type authority country (Location) altitude (m) (T)raining required notes
code (N)ight flight permitted
Full (A)utonomy
TU Delft Kite power ILT NL Valkenburg 500 N
system Airfield
Kitemill Air traffic CAA NO Lista 520 P – T – A – N
Ampyx Power Unmanned NAA NL Kraggenburg 300 P – T – A *a
kPower *bFAA US *c609 P – T – N
FAA US *d5486 NOTAMfreq.
FAA US *e>10000 NOTAMfreq.
QConcepts *g*hNL Doetinchem 300 P – A
Altaeros Air traffic FAA US Confidential 240 Confidential
Energies obstacle
TwingTec Tethered BAZL CH Chasseral, 150, 300iA *j
kite Diegenstal,
a5000 meters of visibility required, off-cable flight below 450 m, not above people, 150 m horizontal distance from
people, traffic and buildings, visual line-of-sight (VLOS)
bLegacy kite rules (FARs, part 101)
cAny place where legacy kites can be operated
dWarm Springs FAA UAS Test Range
eThe Tillamook FAA UAS Test Range
fNotice to Airman
gEnvironmental permit (Dutch: “omgevingsvergunning”)
hLocal municipal
iDepending on location
jmax 20 m2, max 25kg
Table 29.3 Selection of flight permit data
29.4 AWE Systems in the Airspace
Aviation authorities divide the airspace into segments. These segments are called
classes and labeled with the letters A through G. Each class has its own rules. For
example, in Class A, all operations must be conducted under instrument flight rules
(IFR) and air traffic control (ATC) clearance is required for flights. Even though
most countries adhere to ICAOs standard rules for classes, individual nations can
adapt the rules for their own needs. Current AWE system prototypes operates in
Class G airspace, which is normally near to the ground. Figure 29.1 shows the
airspace separation and Class G airspace. Class G is typically up to 1200 feet above
ground level (AGL). However, Class G can be limited to 700 feet AGL if there
is an airport close by, which requires Class B airspace in its vicinity as shown in
Fig. 29.1. Class G is known as uncontrolled air space. There is no specific aircraft
equipment or pilot specifications to enter Class G. Moreover, no ATC communica-
tion is required to fly in Class G. Although Class G is uncontrolled, civil aviation
rules are still valid. There are visibility and cloud clearance requirements for flights
in Class G, and most flights operate under visual flight rules, meaning that separa-
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 709
14,500 MSL
1,200 AGL
700 AGL
18,000 MSL
FL 600
Fig. 29.1 Airspace separation and Class G airspace by FAA [14]
tion is based on the “see and avoid” principle. Since class G airspace is open to all
users, interference between AWE systems and aircraft is possible.
In addition to interference risk, there are other aviation related risks posed by
AWE systems. For example, uncontrolled crash (while the tether is attached or not)
or uncontrolled departure from the designated flight area (with the tether partly at-
tached or also detached) are the aviation risks which have to be managed.
29.5 Relevant Aviation Certification Bodies
This section discusses the regulatory bodies that provide rules for safe aviation and
civil airspace. There are national aviation organizations as well as international avi-
ation organizations that strive to harmonize aviation rules, in order to facilitate in-
ternational air travel. These organizations all could have a role in the AWE relevant
rule making process.
29.5.1 International Civil Aviation Organization (ICAO)
The ICAO was founded in 1944 upon the signing of the Convention on International
Civil Aviation, commonly known as Chicago Convention. Since 1947, the organi-
zation works with the Convention’s 191 Member States and with global aviation
organizations as a specialized agency of the United Nations (UN). ICAO develops
International Standards and Recommended Practices (SARPs) which are used by
member states as a framework for their aviation law making processes.
710 Volkan Salma et al.
29.5.2 Federal Aviation Authority (FAA)
The FAA is the civil aviation agency of United States Department of Transportation.
The agency makes Federal Aviation Regulations (FARs) and puts them into practice
to ensure the safety of civil aviation within the United States. The FAA is authorized
to certify a civil aircraft for international use.
29.5.3 European Aviation Safety Agency (EASA)
The EASA was established in 2002 by the European Commission (EC) to ensure the
safety of civil aviation operations. The agency advises the EC and member states of
the European Union (EU) regarding new legislation. EASA is a second agency, next
to the FAA, authorized to certify civil aircraft for international use.
29.5.4 National Aviation Authority (NAA)
The national regulatory body which is responsible for aviation is denoted as NAA
or civil aviation authority (CAA). These authorities make national legislation in
compliance with ICAO SARPs.
29.5.5 Joint Authorities for Rulemaking on Unmanned Systems
The JARUS is a group that consists of experts from national aviation authorities
or regional aviation safety organizations which aims to define the certification re-
quirements for UAVs to safely integrate them to the current aviation system. JARUS
defines its objective for UAVs as follows [29]: provide guidance material aiming to facilitate each authority to write their own require-
ments and to avoid duplicate efforts.
Working groups in JARUS publish recommended certification specifications for in-
terested parties such as ICAO, EASA and NAAs.
29.6 Regulations for Airborne Wind Energy Systems
At the time of this study, there is no directly applicable regulation for AWE tech-
nologies. However, regulations for UAVs, air traffic obstacles or unmanned balloons
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 711
are available as a starting point for tailoring to the specifics of a selected AWE ar-
chitecture. In this section, current regulations for unmanned aerial vehicles from
different regulatory bodies, air traffic obstacle regulations and tethered gas balloon
regulations are summarized. Similar-looking AWE systems can be categorized dif-
ferently depending on the modes of operation and the inherent safety measures and
the proper starting point should be selected accordingly, together with the responsi-
ble aviation authority. Note that our focus is mostly on the developing UAV regula-
tion since we expect that most tethered aircraft that will have the ability to (aerody-
namically) leave their restricted safe area as a result of a single tether failure will be
considered unmanned aircraft. Hence, for those systems, the UAV regulation seems
the most appropriate starting point.
29.6.1 Regulations for the Unmanned Aerial Vehicle Category
Unmanned aerial vehicles were first used in the military sector. The technology
then evolved also for civil applications and nowadays there are already many com-
mercial products on the market, such as UAVs for high-quality aerial photography
or 3D mapping. However, the increasing interest in UAVs has also led to a rise
in safety concerns. As a consequence, national aviation agencies and international
aviation organizations have directed their attention to developing certification pro-
cesses, regulations and standards for UAVs including those related to airworthiness.
One of the main challenging factors for UAV regulation is the wide variety of sys-
tems in the UAV domain. For instance, the UAV concept includes devices from
micro UAVs which are extremely lightweight (e.g. 16 grams [3]) to High Altitude
Long Endurance (HALE) class UAVs up to 14 tons [42]. Consequently, there is no
consensus on a classification method which is able to cover this broad range yet.
Several different classification approaches have been proposed for UAVs, such as
classification according to aircraft weight, avionics complexity level, aircraft con-
figuration (number and type of engines, etc.), aircraft speed, operation purpose (e.g.,
aerial work), operation airspace (segregated, non-segregated), overflown area, ki-
netic energy, operational failure consequence, and operation altitude.
The first publicly accepted standardization agreement, the STANAG 4671 [41]
compiled by the North Atlantic Treaty Organization (NATO), was an important step
forward in UAV registration, even though it is limited to military UAVs. The stan-
dard is based on EASA’s CS-23 [6] civil airworthiness code. In addition to CS-23,
STANAG 4671 includes subparts which are specific to UAVs such as ground control
station and datalink. The standard provides a broad range of requirements for flight,
aircraft structure, design, construction, power plant, equipment, command and con-
trol and the control station. However, the standard only addresses fixed-wing UAVs
with a weight between 150 and 20,000 kg. As a result a considerable number of UAV
types are not covered by the standard, among which the designs that are not struc-
turally similar to conventional aircraft. With the following STANAG 4703 [40], the
712 Volkan Salma et al.
NATO Standardization Agency (NSA) defined the airworthiness requirements also
for lighter military UAVs whose take-off weight does not exceed 150 kg.
At the time of writing this chapter, required rules for integrating UAVs to civil
airspace are still subject to change and different certification proposals from differ-
ent certification authorities exist. In addition, it is known that a limited number of
UAV applications are certified for civil operations by FAA and EASA with a case-
by-case risk evaluation and only for specific operations. Depending on the definition
of UAV in the upcoming regulations by different aviation authorities, some of the
AWE applications may fall into the UAV category. In the following we will explore
the possibilities in the light of current regulations, known regulatory views and the
published regulatory proposals.
For AWE applications falling in the UAV category an airworthiness certificate
would be sought for commercial operation. Currently, two types of airworthiness
certificates are common for manned aviation. In contrast to the standard airworthi-
ness certificate, the restricted airworthiness certificate has operational limitations
such as restrictions on maneuvers, speed, activities undertaken or where the flights
may be conducted. According to first drafts of UAV certification method propos-
als, a similar type scheme (standard and restricted airworthiness) will be used for
UAVs. Considering that current AWE applications have very specific characteris-
tics, such as being tethered to a ground station or operating in a specific area, it can
be expected that the restricted type certificate will apply. ICAO Regulations for Unmanned Aerial Vehicles
On 7 March 2012, ICAO adopted Amendment 6 to the International Standards
and Recommended Practices, Aircraft Nationality and Registration Marks, which is
identical to Annex 7 to the Convention on International Civil Aviation (also known
as Chicago Convention). This revision included UAVs as remotely piloted aircraft
(RPA), defining an RPA as “an unmanned aircraft which is piloted from a remote pi-
lot station” [23]. At the same time Amendment 43 to Annex 2 “Rules of the Air” to
the Chicago Convention was adopted. This amendment stipulates that an RPA shall
be operated in such a manner as to minimize hazards to persons, property or other
aircraft. Amendment 43 is the first regulation by ICAO that introduces the operation
of remotely piloted aircraft systems (RPAS) in the Chicago Convention.
The current regulation [24] requires a certification of all types of aircraft that
intend to fly in controlled and uncontrolled airspace, even though the certifica-
tion framework for UAVs is not clear in Chicago Convention yet. In March 2011,
ICAO published Circular 328 specifically addressing “Unmanned Aircraft Systems
(UAS)” [28]. The aim of this circular is to establish a basis by properly defining the
new technology, clarifying the differences between unmanned and manned aircraft.
In March 2015, Circular 328 was superseded by the “Manual on Remotely Piloted
Aircraft Systems (Doc 10019)” [27]. The following excerpts from this document are
deemed representative of ICAO’s current perspective on UAVs [27, Chap. 1, Sect. 6]
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 713
1.6.3 These hazards relate to all RPAS operations irrespective of the purpose of the op-
eration. Therefore, the recommendations in this manual, unless specified otherwise, apply
equally to commercial air transport and general aviation, including aerial work, operations
conducted by RPAS.
1.6.4 In order for RPAS to be widely accepted, they will have to be integrated into the ex-
isting aviation system without negatively affecting manned aviation (e.g. safety or capacity
reduction). If this cannot be achieved (e.g. due to intrinsic limitations of RPAS design), the
RPA may be accommodated by being restricted to specific conditions or areas (e.g. visual
line-of-sight (VLOS), segregated airspace or away from heavily populated areas).
and further [27, Chap. 2, Sect. 2]
2.2.7 Categorization of RPA may be useful for the purpose of a proportionate application of
safety risk management, certification, operational and licensing requirements. RPA may be
categorized according to criteria such as: maximum take-off mass (MTOM), kinetic energy,
various performance criteria, type/area of operations, capabilities. Work is underway in
many forums to develop a categorization scheme.
Autonomous unmanned aircraft and their operations, including unmanned free
balloons or other types of aircraft which cannot be managed on a real-time basis
during flight, is not in the scope of the Doc 10019. At the time of writing, there are
no rules for AWE applications or tethered aircraft in the ICAO regulations. EASA Regulations for Unmanned Aerial Vehicles
EC-2008 is the European Union’s law that converts the ICAO SARPs to the EU
structure, describing the responsibilities of EASA and NAAs [12]. Annex II of EC-
2008 defines the exceptional cases which are outside EASA’s area of responsibility.
For example, the following cases do not lie within the responsibility of EASA2:
(b) aircraft, specifically designed or modified for research, experimental or scientific pur-
poses, and likely to be produced in very limited numbers...
...(I) unmanned aircraft with an operational mass of no more than 150 kg
NAAs of member states are responsible for the regulation of these cases. Apart
from the above mentioned exception cases, EASA makes the common European
rules for UAV certification.
One of the important steps in civil UAV airworthiness certification is the interim
Policy Statement EASA E.Y013-01 [4], which is still in use and aims at protecting
people and property on the ground but not the UAV itself. The policy provides a
kinetic energy-based classification method and a systematic certification guideline
which suggests tailoring of fixed manned aircraft certification regulations. Accord-
ing to the tailoring principle, class determination has to be done as a first step using
the kinetic energy evaluation method, which is defined in the regulation. Then, a
tailoring process is required, adjusting an already existing certification specification
for a conventional aircraft, which is in the same kinetic energy class with the new
2In this and the following quotations the emphasis is added by the authors
714 Volkan Salma et al.
type that is intended to be certified. During this process, each requirement of the ex-
isting certification specification has to be reviewed and its applicability for new type
has to be evaluated. Depending on the new type, special conditions may be added.
This conditions may provide a starting point for the future applicants. It is further
stated in the policy [4, Paragraph 21A.17]
At an applicant’s request, the Agency may accept USAR version 3, STANAG 4671, or later
updates, as the reference airworthiness code used in setting the type certification basis
It should be noted that Ampyx Power and EASA have come to the conclusion that
the tethered aircraft of Ampyx Power resembles more an unmanned glider than the
typical tactical UAV that STANAG 4671 is templating. Therefore, the company has
chosen to tailor CS-22 for its airworthiness baseline. These examples show EASA’s
willingness to accept the most suitable pre-existing airworthiness certification stan-
dard as a starting point for the tailoring process. The EASA E.Y013-01 has been
amended regarding system safety to cover the class of very light aircraft (VLA) by
Special Condition SC-RPAS.1309 [8], leaning on CS23.1309 [6]. This amendment
was also adopted by Ampyx Power as a starting point for system safety.
The EASA E.Y013-01 provides guidance for restricted type certificates, as well
as for standard type certificates for UAVs. However, it is not aimed at regulating
public operations such as UAVs that are used by the military, police or firefighting
department. Regarding mass criteria, EASA advises the NAAs of the member states
to develop their own regulations for the UAVs which are lighter than 150 kg. As a
consequence of this rule, current laws for light UAVs in the European countries are
not harmonized and some of the countries do not yet have regulations.
EASA publishes the drafts of amendments on ICAO regulations as Notice of
Proposed Amendment (NPA) in order to collect the comments of member states. In
September 2014, the agency published the NPA-2014-09 with the first mention of
operations of tethered aircraft [9]. In this notice, EASA identifies the tethering of
the aircraft as a recognized mode of operation for remotely piloted aircraft
RPA typical flight pattern may comprise a wide range of scenarios, which could be
categorized in the following types of operations:
(a) Very low level (VLL) operations below the minimum heights prescribed for normal
IFR or VFR operations: for instance below 500 ft (150 m) above ground level (AGL);
they comprise:
(1) operations of tethered aircraft;
(2) Visual line of sight (VLOS) within a range from the remote pilot, in which the remote
pilot maintains direct unaided visual contract with the RPA and which is not greater than
500 meters;
(3) Extended visual line of sight (E-VLOS) where the remote pilot is supported by one
or more observers and in which the remote crew maintains direct unaided visual contract
with the RPA;
(4) Beyond VLOS (B-VLOS) where neither the remote pilot nor the observer maintain
direct unaided visual contract with the RPA.
(b) Operations of tethered aircraft, above the minimum height in (a); ...
This statement can bring rigid wing AWE systems under Amendment 43 to An-
nex II of the Chicago Convention. Annex II covers other aspects related to RPAS
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 715
besides their integration in airspace, namely the principles that RPAS shall be air-
worthy, the remote pilots licensed and the RPAS operator certified. However, spe-
cific ICAO standards and recommended practices—the SARPs—for the airworthi-
ness and operation of RPAS as well as for licensing of the remote pilot have not
been developed yet.
In addition to the EASA E.Y013-01 and NPA 2014-09, EASA has recently pub-
lished a “Concept of Operations for Drones” [7]. This new proposal starts from the
application rather than the aircraft used, applying a risk-based classification and reg-
ulation scheme for UAV operation. With this new scheme, EASA aims to cover a
broad range of types and operations of UAVs, applying the three categories “Open”,
“Specific” and “Certified”. Operations in the “Open” category would not require any
certification as long as they operate in a defined boundary, for example not close to
aerodromes, not in populated areas, being very small. The boundary conditions are
not defined in the proposal but it is mentioned that conditions for the “Open” cate-
gory are expected to be clarified in a collaboration with member states and industry.
The “Specific” category is for UAVs whose conditions will not fit the “Open” cate-
gory. These will require a risk assessment process specific to the planned operations.
Depending on the output of the risk assessment process they might be certified case
by case with specific limitations adapted to the operations. Permitting for the “Spe-
cific” category would be delegated to the NAAs. If the risk assessment shows that
the UAV introduces a very high risk then the “Certified” category would be appli-
cable. This requires multiple certificates similar to those for the manned aviation
system, such as pilot licenses, approvals for design and manufacturer organizations.
In addition to the certificates which are currently in use for manned aviation indus-
try, the “Specific” category may also require new additional certifications that are
specific to UAV operations, such as command and control link certification.
The operation-specific, case-by-case safety assessment method for the “Specific”
category provides a mechanism to cover unconventional machines flying in civil
airspace. If these machines have sufficient risk mitigation factors, such as being
connected to the ground or being operated away from populated areas, an operation
specific certificate could be sought. Current AWE applications would fall most likely
into the “Specific” category, whereas utility-scale commercial systems would fall
into the “Certified” category. FAA Regulations for Unmanned Aerial Vehicles
The Title 14 of the Code of Federal Regulation [49] regulates the aeronautics and
space operations conducted within the boundaries of USA. According to the current
version [49, Part 91, Sect. 2031]
...every civil aircraft that operates in the US must have a valid airworthiness certificate.
Currently, unmanned aircraft systems can be certified by the FAA to operate
in the national airspace (NAS) with a special airworthiness certificate in the experi-
mental category [49, Part 21, Sect. 191]. However, FAA is regarding the aircraft as a
716 Volkan Salma et al.
part of a system, which includes command and control link, ground control systems
and ground crew and accordingly, the entire system has to be certified. Nevertheless,
the subsystems which do not exist in conventional aircraft, such as command and
control links, ground control systems or sense and avoid systems, do not have any
regulations yet. As a result, general use of commercial UAVs for civil use is highly
restricted in US airspace at present.
The Title 14 of the Code of Federal Regulation (14 CFR) classifies the operation
purpose of UAVs at a very high level [22]. In this classification, the first category
is “Civil use”, which refers to operation by a company or individual. The second
category is “Public use”, which includes the operations for scientific research and
governmental purposes such as military operations. The last category is recreational
use of model aircraft which is covered by FAA Advisory Circular 91-57 [16]. Cur-
rently, UAVs which are used for public operations require a Certificate of Waiver or
Authorization (COA) from the FAA that permits public agencies and organizations
to operate in a particular airspace. There are many COAs in use today by the several
organizations, such as the Departments of Agriculture (USDA), Commerce (DOC),
Defense (DOD), Energy (DOE), Homeland Security (DHS), Interior (DOI), Justice
(DOJ) as well as NASA, State Universities and lastly State/Local Law Enforcement
[51]. UAVs in the “Civil use” category can only operate with a special airworthiness
certificate in the experimental category with limits on the operation to not create any
risk for other airspace users or for people on the ground [49].
In February 2012, the United States Congress enacted the Federal Aviation Ad-
ministration Reauthorization Legislation, which seeks to provide a framework for
integrating UAVs safely into American airspace [48]. Following this action, the Next
Generation Air Transportation System (NextGen) partner agencies, which are the
Department of Transportation (DOT), DOD, DOC and DHS as well as NASA and
FAA, started to work together to develop the Unmanned Aircraft Systems (UAS)
Comprehensive Plan [50]. This report defines the interagency goals, objectives and
approach to integrating UAS into the national airspace. Following the release of
this report, FAA published a UAS roadmap [15] which includes a timeline for tasks
required for integration of UAVs into the current aviation system. In accordance
with this roadmap, FAA together with NexGen agencies established test sites for
UAV research and development and studied new UAV-specific technologies such as
detect-and-avoid systems.
While the FAA works on new regulations, the interim policy “Special Rules for
Certain Unmanned Aircraft Systems” [48] has been enacted in 2012. Briefly, the
Sect. 333 law authorizes the Secretary of Transportation to give a permit to civil
operations of UAVs after an evaluation.
Regarding AWE applications, there is a discrepancy between EASA and FAA.
On the one hand EASA recognizes the tethered aircraft as unmanned aircraft, on
the other hand FAA clearly excludes the tethered aircraft from unmanned aircraft
category [18, Appendix A];
41. Unmanned Aircraft (UA). A device used or intended to be used for flight in the air
that has no onboard pilot. This device excludes missiles, weapons, or exploding warheads,
but includes all classes of aircraft, helicopters, airships, and powered-lift aircraft without
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 717
an onboard pilot. UA do not include traditional balloons (see 14 CFR part 101), rockets,
tethered aircraft and un-powered gliders
In December 2011, the FAA had issued a “Notification for Airborne Wind En-
ergy Systems” [17], according to which each deployment of an AWE system needs
to be assessed on a case-by-case basis, accounting for the surrounding aviation en-
vironment to ensure aviation safety. Makani Power submitted a detailed response to
this notification in February 2012 [21].
29.6.2 Regulations for Air Traffic Obstacle Category
Air navigation obstacles can be an impediment to civil air traffic. Some of the AWE
companies registered their current AWE prototypes as air navigation obstacle (see
Table 29.2). The aim of such a registration is to inform the aviation system to pre-
vent incidents. For example, masts and wind turbines have to be registered as air
traffic obstacles. This information is visualized in aviation charts and it is taken into
account during flight route planning or emergency situations. If we consider the
typical operation altitudes of AWE systems, obstacle registration might be sought
in the future. ICAO defines “obstacle” in the Chicago Convention, Annex 4 [25] as
All fixed (whether temporary or permanent) and mobile objects, or parts thereof, that:
a) are located on an area intended for the surface movement of aircraft; or
b) extend above a defined surface intended to protect aircraft in flight; or
c) stand outside those defined surfaces and that have been assessed as being a hazard to
air navigation.
According to this definition, air traffic obstacles can be mobile as many AWE sys-
tems are.
The Chicago Convention, Annex 14 [26] is about aerodromes and it includes the
definition of the surrounding zones. Obstacle limitation surfaces are zones which
have to be free of obstacles to permit regular civil use of the airspace. However,
many AWE applications will potentially operate outside of these zones, about which
the ICAO recommends to the civil aviation authorities the following in Annex 14
4.3 Objects outside the obstacle limitation surfaces
4.3.1 Recommendation.— Arrangements should be made to enable the appropriate au-
thority to be consulted concerning proposed construction beyond the limits of the obstacle
limitation surfaces that extend above a height established by that authority, in order to per-
mit an aeronautical study of the effect of such construction on the operation of aeroplanes.
4.3.2 Recommendation.— In areas beyond the limits of the obstacle limitation surfaces,
at least those objects which extend to a height of 150 m or more above ground elevation
should be regarded as obstacles, unless a special aeronautical study indicates that they do
not constitute a hazard to aeroplanes.
According to Annex 14, obstacles have to be conspicuous to air vehicles. Its
Chap. 6 on “Visual aids for denoting obstacles” describes the required marking and
718 Volkan Salma et al.
lighting scheme for different types of obstacles. Regarding marking methods for
increasing the visibility the following is recommended Recommendation –Other objects outside the obstacle limitation surfaces should be
marked and/or lighted if an aeronautical study indicates that the object could constitute a
hazard to aircraft (this includes objects adjacent to visual routes e.g. waterway, highway).
Similarly, Article 6.2.2 defines marking requirements for mobile objects and Ar-
ticle 6.2.3 defines lighting requirements for objects with a height exceeding 150 m
above ground. Article 6.2.4 addresses wind turbines separately, which is important
because it defines the required marking for a wind farm setup. A similar or hybrid
approach might be sought for future AWE farms.
29.6.3 Regulations for Tethered Gas Balloons Category
For static AWE systems that resemble the system developed by Altaeros Energies
[53] a more applicable basis is the EASA certification specification for tethered gas
balloons, CS-31TGB [5]. The lack of a complex control system which is required
for the crosswind AWE systems, in conjunction with the self-stabilizing nature of a
tethered lighter-than-air gas balloon will probably be sufficient to make CS-31TGB
We note here that the certification specification provides two more important
inputs for the generic safety requirements and certification basis of AWE systems:
1. CS 31TGB.25 where the required tether safety factor of 3.5 is given.
2. AMC 31TGB.53(a) where it is stated that acceptable means of compliance to
CS 31TGB.25(a) can be shown by a certificate of compliance to the Machinery
Directive 2006/42/EC [11]. This means that a winch system can be certified
to the Machinery Directive 2006/42/EC and thereby show compliance with an
airspace certification specification. For AWE systems that use a winch as part
of the ground station this can be important to limit the certification efforts for
non-flying parts.
29.7 Discussion
Since no unified legal framework for AWE systems exists to the present day, the
categories mentioned above are just starting points for a discussion with the author-
ities. They are a reference from which deviations can be defined systematically on
a case-by-case basis. Nevertheless, we can derive some generally valid considera-
AWE systems introduce potential hazards for other airspace users and people or
critical infrastructure on the ground. These inherent risks have to be mitigated to
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 719
successfully commercialize AWE technologies. It should be noted that this risk mit-
igation is not only sensible for saving lives, but also, from a commercial perspective,
to reduce the costs resulting from accidents and crashes. It may well be a property
of AWE that the commercial requirement for reliability is even more stringent than
that coming from aviation regulations.3
If we define “normal operation” of the AWE system as the expected continuous
operation within a limited airspace, with limited altitude and horizontal boundaries,
we have to account for potential situations in which the AWE system interacts with
the current civil aviation system. To prevent such undesirable interaction, regardless
of the type of AWE system, some form of airspace segregation has to be arranged.
Furthermore, independent of the selected regulatory starting point, as UAV, ob-
stacle or otherwise, and independent of the degree of permitting or certification
sought, it will be fundamental that any risk of one or multiple fatalities as a result of
a single functional failure is mitigated. The aviation approach to safe systems design
is based on the presumptions that
any single function can fail, so it must be assumed the tether can rupture, and
any single failure with potential catastrophic consequence shall be demonstrably
3Consider, as an example, a fully autonomous utility-scale system that has a design lifetime of 20
years and is in operation 5000 hours per year. Suppose that the airborne element replacement cost
represents 10% of the levelized cost of energy (LCOE). As a complex system, the airborne element
may have 100 failure conditions that would lead to loss of the aircraft (“hazardous”). If any of those
failure conditions occurs during the design lifetime, the energy cost would be driven up by 10%,
say 0.5 eurocent per kWh, which is more than significant and will negatively affect the commercial
viability. It is commonly argued that the probability of a failure condition that might lead to death
of someone from the general public (“catastrophic failure”) must be at least 10 times less than
a hazardous failure, leading to a required probability level per catastrophic failure condition of
108per flight hour (pfh), which is once every 5000×20×100×10 flight hours. This number is
two orders of magnitude more stringent than the 106pfh requirement of Special Condition SC-
RPAS.1309 [8] regarding UAVs or Certification Specification CS-23.1309 [6, Paragraph 23.1309]
regarding general aviation.
To make the argument more vivid, one can also turn it around. For general aviation, a catas-
trophic incident is accepted every 10,000 flight hours. Yet, this number of flight hours is reached
every other year by a single utility-scale AWE system and every week for a park of 100 systems.
This is clearly something the general public would not accept. Note that utility-scale AWE cannot
be installed too far away from the population, since they are supposed to provide the population
with electricity, and long-distance cabling cost is forbiddingly expensive, so part of the solution
has to come from additional design for safety. Still, even with the 108pfh reliability level calcu-
lated above, in a park of 100 systems, nearly every 2 months an aircraft would be expected to crash
within the park, which hardly seems economically viable. So, a further reduction of the number of
hazardous failure conditions and/or a further improvement in reliability, and accordingly in design
rigor, may be recommendable for this example.
What sets utility-scale AWE systems apart from general aviation aircraft and typical RPAS is
the number of flight hours and the complexity, which determines the number of failure conditions.
The challenge is that AWE systems are in this regard more in the direction of commercial airliners,
albeit not quite as critical or complex, and an intermediate reliability approach and design rigor is
to be pursued.
4The certification requirement for catastrophic failure probability applies to accidental death of
someone from the general public during commercial operation. This is not to be confused with
720 Volkan Salma et al.
Thus, assuming that the commercial AWE system is operated near a populated
area—the consumer of the generated electricity—the risk of uncontrolled flight out-
side of the designated safe zone shall be mitigated in case of tether rupture or in-
tentional release of the aircraft. Having a controlled flight following a mechanical
disconnection is one possible option to mitigate such an event. Having a second,
structurally independent tether is another option. Or one could otherwise demon-
strate that the detached kite is not able to reach people or critical infrastructure on
the ground.
It should be noted that if one aims to operate a kite with significant kinetic energy
directly above people, the tether solution alone cannot act as sufficient mitigation,
for example in case of a faulty flight controller that would lead to a crash onto the
populated area. It shall then be shown that there are independent means of overcom-
ing a single failure of any flight control function.
Factors that will affect the authorities’ assessment of the overall risk posedby the
system furthermore include the kinetic energy, the availability of onboard propul-
sion, which determines the flight range, and the complexity, including autonomy,
with which AWE aims to enter new territory.
Ampyx Power interprets the above review in such a way, that single-tether AWE
systems that can still (aerodynamically) reach populated areas after tether failure or
release are likely to be considered to be UAVs. Therefore, the certification approach
for UAVs seems to be a suitable starting point and the level of certification will
depend on the risk factor which the system presents [7]. A different approach, such
as obstacle registration, may arguably be followed, for example for kites that are
steered from the ground above a restricted area using two structurally independent
In any case, certification of design and operation to some defined standard will,
in our view, be a necessity for commercial deployment. Apart from the expected
positive impact that the introduction of rigorous processes will have on system re-
liability and maintenance, design certification enables the concept of similarity as
evidence for quality and safety. This is a proven way to cost-effectively deploy the
large numbers of complex systems that the AWE industry aspires to. This means
that also production and maintenance aspects shall be standardized. These further
certifications are outside the scope of this study. It should be noted, that we only
examples that may come to mind, such as the unfortunate recent SpaceshipTwo incident [39] that
illustrate the higher level of acceptance for accidents during development affecting flight crew
only. Secondly, the Certification Specification CS-23.1309 [6, Paragraph 23.1309] for mitigation
of catastrophic failures applies to the functions of aviation systems, such as avionics, complex
mechanisms, not to structures. For structures, it is recognized that redundancy could make the
aircraft too heavy. The accepted approach there is to include the proper design safety factor and
design for damage tolerance, for example, due to fatigue following barely visible tooling damage,
hail, bird strike.
We argue that the tether is more than a structural element, but a functional part of a complex
mechanism. It is used to control and restrict the dynamics of the airborne element, it is subject to
wear during reeling, its integrity is affected by weather, subject to salt spray, dirt and lightning, it
is subject to complex loading dynamics, such as jerks, shocks etc. At the same time, the tether is
designed for minimal drag so the design safety factor may be limited. Hence we have to assume its
incidental failure as part of a safety analysis.
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 721
considered so far the aviation-related risks and the regulation aspects of the AWE
systems from an aviation perspective.
AWE systems are complex systems which consist of many components. There
are additional regulations requirements, such as electric machinery regulations, grid
connection regulations, noise emission regulations, environmental regulations and
lighting regulations for the subcomponents which should be taken into consider-
ation. It is noted here that those system elements and operations certified by an
aviation authority are generally not required to comply also to machine standards,
but these standards may be supporting guidance for the design or verification.
29.8 Conclusions
AWE systems have to be regulated for a successful commercial introduction and
broad public acceptance. Ultimately, AWE systems are expected to be larger and
heavier than current prototypes. They are expected to operate in Class G airspace
where interaction with other airspace users is possible. In addition, AWE systems
introduce risks to the people on ground. Therefore, it is expected that commercial
AWE systems will have to comply with international airspace regulations.
The regulation framework for AWE systems is not yet mature. Current prototypes
operate with special permits. These operation permits are issued by local aviation
authorities and there is little commonality among the permits. Registration of the
prototype as an air traffic obstacle or unmanned aerial vehicle (UAV) is the main
approach followed by AWE companies and academic research groups. Classifying
the AWE systems as UAV is a controversially discussed topic: on the one hand,
current EASA view recognizes the tethered unmanned aircraft as UAV, on the other
hand FAA excludes the tethered aircraft from the UAV category.
Each AWE system category has its own operation characteristics. The path for
flight permitting and/or product certification goes through hazard analysis and miti-
gation independently from the category into which the system falls.
A regulation set which is specific to AWE systems will be built up over time,
based on the specifically negotiated cases of first movers. As long as such a regu-
lation is not in place, the most appropriate existing certification specifications and
standards will have to be selected with authorities and tailored as necessary.
Lastly, yet importantly, AWE developers should accept the shared responsibility
to avoid any incidents involving other airspace users, people on the ground or critical
infrastructure. Such an incident, if no proper prevention or mitigation approach was
in place, could well put the entire AWE industry under the most stringent aviation
rules, which would jeopardize its commercial viability and eventual success.
Acknowledgements The financial support of the European Commission through the projects
AMPYXAP3 (H2020-SMEINST-666793) and AWESCO (H2020-ITN-642682) is gratefully ac-
722 Volkan Salma et al.
1. Bormann, A., Ranneberg, M., Kövesdi, P., Gebhardt, C., Skutnik, S.: Development of a Three-
Line Ground-Actuated Airborne Wind Energy Converter. In: Ahrens, U., Diehl, M., Schmehl,
R. (eds.) Airborne Wind Energy, Green Energy and Technology, Chap. 24, pp. 427–437.
Springer, Berlin Heidelberg (2013). doi: 10.1007/978-3-642-39965-7_24
2. Cherubini, A., Papini, A., Vertechy, R., Fontana, M.: Airborne Wind Energy Systems: A re-
view of the technologies. Renewable and Sustainable Energy Reviews 51, 1461–1476 (2015).
doi: 10.1016/j.rser.2015.07.053
3. Croon, G. C. H. E. de, Groen, M. A., De Wagter, C., Remes, B., Ruijsink, R., Oudheusden,
B. W. van: Design, aerodynamics and autonomy of the DelFly. Bioinspiration & Biomimetics
7(2), 025003 (2012). doi: 10.1088/1748-3182/7/2/025003
4. European Aviation Safety Agency: Airworthiness Certification of Unmanned Aircraft Systems
(UAS), Policy Statement EASA E.Y013-01, 25 Aug 2009. https: / /www. easa.europa. eu /
5. European Aviation Safety Agency: Certification Specifications and Acceptable Means of
Compliance for Tethered Gas Balloons, EASA CS-31TGB, 1 July 2013. https://www.easa.
6. European Aviation Safety Agency: Certification Specifications for Normal, Utility, Aerobatic,
and Commuter Category Aeroplanes, EASA CS-23, 14 Nov 2003. https://www.easa.europa.
7. European Aviation Safety Agency: Concept of Operations for Drones. https : //www.easa.
europa. eu/system/files/dfu/204696_EASA _concept _drone _brochure_web.pdf. Accessed
9 May 2016
8. European Aviation Safety Agency: Equipment, Systems and Installations in Small Remotely
Piloted Unmanned Systems (RPAS), EASA SC-RPAS.1309-01, July 2015. https://www.easa.
9. European Aviation Safety Agency: Transposition of Amendment 43 to Annex 2 to the Chicago
Convention on remotely piloted aircraft systems (RPAS) into common rules of the air, EASA
NPA 2014-09, 3 Apr 2014. https :/ / /system /files/dfu/NPA%202014-
10. European Commission: Commission Regulation (EU) No 748/2012 of 3 Aug 2012 laying
down implementing rules for the airworthiness and environmental certification of aircraft and
related products, parts and appliances, as well as for the certification of design and production
organisations, 3 Aug 2012.
11. European Parliament and Council of the European Union: Directive 2006/42/EC of the Euro-
pean Parliament and of the Council of 17 May 2006 on machinery, and amending Directive
95/16/EC, 17 May 2006.
12. European Parliament and Council of the European Union: Regulation (EC) No 216/2008 of
the European Parliament and of the Council of 20 Feb 2008 on common rules in the field
of civil aviation and establishing a European Aviation Safety Agency, and repealing Council
Directive 91/670/EEC, Regulation (EC) No 1592/2002 and Directive 2004/36/EC, 20 Feb
13. Fagiano, L., Milanese, M., Piga, D.: High-altitude wind power generation. IEEE Transactions
on Energy Conversion 25(1), 168–180 (2010). doi: 10.1109/TEC.2009.2032582
14. Federal Aviation Administration: Aeronautical Information Manual. Official Guide to Basic
Flight Information and ATC Procedures. (2015).
15. Federal Aviation Administration: Integration of Civil Unmanned Aircraft Systems (UAS) in
the National Airspace System (NAS) Roadmap, 1st ed., 7 Nov 2013. https:/ /
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 723
16. Federal Aviation Administration: Model Aircraft Operating Standards, FAA Advisory Circu-
lar 91-57, 1 June 1981.
17. Federal Aviation Administration: Notification for Airborne Wind Energy Systems (AWES),
FAA-2011-1279, Dec 2011. https: // www.gpo . gov/ fdsys/ pkg /FR - 2011- 12 - 07 /pdf /2011 -
18. Federal Aviation Administration: Unmanned Aircraft Systems (UAS) Operational Approval,
FAA N 8900.227, 30 July 2013. https:/ / documentLibrary/ media/ Notice/ N_
19. Fritz, F.: Application of an Automated Kite System for Ship Propulsion and Power Genera-
tion. In: Ahrens, U., Diehl, M., Schmehl, R. (eds.) Airborne Wind Energy, Green Energy and
Technology, Chap. 20, pp. 359–372. Springer, Berlin Heidelberg (2013). doi: 10.1007/978-3-
20. Glass, B.: A Review of Wind Standards as they Apply to Airborne Wind Turbines. In:
Schmehl, R. (ed.). Book of Abstracts of the International Airborne Wind Energy Conference
2015, pp. 80–81, Delft, The Netherlands, 15–16 June 2015. doi: 10.4233 /uuid: 7df59b79-
2c6b - 4e30 - bd58 - 8454f493bb09. Presentation video recording available from: https : / /
21. Hardham, C.: Response to the Federal Aviation Authority. Docket No.: FAA-2011-1279; No-
tice No. 11-07; Notification for Airborne Wind Energy Systems (AWES), Makani Power,
7 Feb 2012.!documentDetail;D=FAA-2011-1279-0014
22. Hayhurst, K. J., Maddalon, J. M., Morris, A. T., Neogi, N., Verstynen, H. A.: A Review of Cur-
rent and Prospective Factors for Classification of Civil Unmanned Aircraft Systems. NASA
TM-2014-218511, NASA Langley Research Center, Aug 2014. https ://shemesh. larc. nasa.
23. International Civil Aviation Organization: Adoption of Amendment 6 to Annex 7, ICAO State
Letter AN 3/1-12/9, 4 Apr 2012.
24. International Civil Aviation Organization: International Standards and Recommended Prac-
tices. Annex 2 – Rules of the Air, 10th ed., July 2005. https : / / www. icao . int / Meetings /
25. International Civil Aviation Organization: International Standards and Recommended Prac-
tices. Annex 4 – Aeronautical Charts, 11th ed., July 2009
26. International Civil Aviation Organization: International Standards and Recommended Prac-
tices. Annex 14, Vol. 1 – Aerodrome Design and Operations, 6th ed., July 2013
27. International Civil Aviation Organization: Manual on Remotely Piloted Aircraft Systems
(RPAS), ICAO 10019, Mar 2015
28. International Civil Aviation Organization: Unmanned Aircraft Systems (UAS), ICAO Circular
328-AN/190, Apr 2012.
29. Joint Authorities for Rulemaking on Unmanned Systems. http://jarus-rpas .org/ (2017). Ac-
cessed 1 Oct 2017
30. Kite Power Systems Ltd. Accessed 4 Oct 2017
31. Kitemill AS. Accessed 16 July 2015
32. Kronborg, B., Schaefer, D.: eWind Solutions Company Overview and Major Design Choices.
In: Schmehl, R. (ed.). Book of Abstracts of the International Airborne Wind Energy Con-
ference 2015, pp. 32–33, Delft, The Netherlands, 15–16 June 2015. doi: 10 . 4233 / uuid :
7df59b79 - 2c6b - 4e30 - bd58 - 8454f493bb09. Presentation video recording available from:
33. Kruijff, M.: The Technology of Airborne Wind Energy – Part I: Launch & Land. https://www. (2017). Accessed 10 Oct 2017
34. Kruijff, M.: The Technology of Airborne Wind Energy – Part II: the Drone. https: //www.
ampyxpower. com/ 2017 /04 / the- technology - of- airborne - wind - energy- part - ii - the- drone
(2017). Accessed 10 Oct 2017
724 Volkan Salma et al.
35. Kruijff, M.: The Technology of Airborne Wind Energy – Part III: Safe Power. https://www. the- technology-of -airborne- wind- energy- part-iii -safe- power
(2017). Accessed 10 Oct 2017
36. Langley, W. R.: Go, Fly a Kite: The Promises (and Perils) of Airborne Wind-Energy Systems.
Texas Law Review 94, 425–450 (2015).
37. Luchsinger, R. H. et al.: Closing the Gap: Pumping Cycle Kite Power with Twings. In:
Schmehl, R. (ed.). Book of Abstracts of the International Airborne Wind Energy Conference
2015, pp. 26–28, Delft, The Netherlands, 15–16 June 2015. doi: 10.4233 /uuid: 7df59b79-
2c6b - 4e30 - bd58 - 8454f493bb09. Presentation video recording available from: https : / /
38. Milanese, M., Taddei, F., Milanese, S.: Design and Testing of a 60 kW Yo-Yo Airborne Wind
Energy Generator. In: Ahrens, U., Diehl, M., Schmehl, R. (eds.) Airborne Wind Energy, Green
Energy and Technology, Chap. 21, pp. 373–386. Springer, Berlin Heidelberg (2013). doi:
39. National Transportation Safety Board: In-Flight Breakup During Test Flight Scaled Compos-
ites SpaceShipTwo, N339SS, Near Koehn Dry Lake, California October 31, 2014. NTSB/AAR-
15/02, Washington, DC, USA, 28 July 2015. https : / / www. ntsb . gov / investigations /
40. North Atlantic Treaty Organization: Light Unmanned Aircraft Systems Airworthiness Re-
quirements, NATO STANAG 4703 draft, 1st ed., Sept 2014
41. North Atlantic Treaty Organization: UAV Systems Airworthiness Requirements (USAR) for
North Atlantic Treaty Organization (NATO) Military UAV Systems, NATO STANAG 4671
draft, 1st ed., Mar 2007
42. Northrop Grumman: RQ-4 Block 40 Global Hawk. http : / / www. northropgrumman . com /
Capabilities/GlobalHawk/Documents/Datasheet_GH_Block_40.pdf. Accessed 16 July 2015
43. Pardal, T., Silva, P.: Analysis of Experimental Data of a Hybrid System Exploiting the Mag-
nus Effect for Energy from High Altitude Wind. In: Schmehl, R. (ed.). Book of Abstracts
of the International Airborne Wind Energy Conference 2015, pp. 30–31, Delft, The Nether-
lands, 15–16 June 2015. doi: 10 . 4233 / uuid : 7df59b79 - 2c6b - 4e30 - bd58 - 8454f493bb09.
Presentation video recording available from:
44. Ruiterkamp, R., Salma, V., Kruijff, M.: Update on Certification and Regulations of Airborne
Wind Energy Systems – The European Case for Rigid Wings. In: Schmehl, R. (ed.). Book of
Abstracts of the International Airborne Wind Energy Conference 2015, pp. 78–79, Delft, The
Netherlands, 15–16 June 2015. doi: 10.4233/uuid:7df59b79-2c6b-4e30-bd58-8454f493bb09.
Presentation video recording available from:
45. Schmehl, R. (ed.): Book of Abstracts of the International Airborne Wind Energy Conference
2015. Delft University of Technology, Delft, The Netherlands (2015). doi: 10 .4233/uuid :
46. Sieberling, S., Ruiterkamp, R.: The PowerPlane an Airborne Wind Energy System. AIAA
Paper 2011-6909. In: Proceedings of the 11th AIAA Aviation Technology, Integration, and
Operations (ATIO) Conference, Virginia Beach, VA, USA, 20–22 Sept 2011. doi: 10.2514/6.
47. Terink, E. J., Breukels, J., Schmehl, R., Ockels, W. J.: Flight Dynamics and Stability of a
Tethered Inflatable Kiteplane. AIAA Journal of Aircraft 48(2), 503–513 (2011). doi: 10.2514/
48. United States Congress: FAA Modernization and Reform Act of 2012. 112th Congress (2011–
2012), House Resolution 658, Became Public Law No 112-95, Feb 2012. http://www.gpo.
49. United States Government: Title 14 Code of Federal Regulations – Aeronautics and Space, bin/text-idx?tpl=/ecfrbrowse/Title14/14tab%5C_02.tpl Accessed
29 May 2016
29 Current and Expected Airspace Regulations for Airborne Wind Energy Systems 725
50. United States Next Generation Air Transportation System Joint Planning & Development Of-
fice: Unmanned Aircraft Systems (UAS) Comprehensive Plan, Washington, DC, USA, Sept
51. University of Washington Technology Law and Public Policy Clinic: Domestic Drones – Tech-
nical and Policy Issues. Clinic Policy Report, University of Washington, School of Law, 2013,
pp. 1–20.
52. Vander Lind, D.: Developing a 600 kW Airborne Wind Turbine. In: Schmehl, R. (ed.). Book of
abstracts of the International Airborne Wind Energy Conference 2015, pp. 14–17, Delft, The
Netherlands, 15–16 June 2015. doi: 10.4233/uuid:7df59b79-2c6b-4e30-bd58-8454f493bb09.
Presentation video recording available from:
53. Vermillion, C., Glass, B., Rein, A.: Lighter-Than-Air Wind Energy Systems. In: Ahrens,
U., Diehl, M., Schmehl, R. (eds.) Airborne Wind Energy, Green Energy and Technology,
Chap. 30, pp. 501–514. Springer, Berlin Heidelberg (2013). doi: 10.1007/978-3-642- 39965-
54. Windlift, Inc. Accessed 16 July 2015
... The proof of safe operation of AWE systems is a critical factor for social acceptance, thus regulations must be enforced in order to certify these systems (Petrick et al., 2018;Salma et al., 2018). For the purpose of the present study, the relative safety of these systems can be assessed by considering the risks involved for human life and property in case of a failure and crash of the wing. ...
Full-text available
Over the last decade, the Airborne Wind Energy (AWE) innovation has been evolving with the development of several prototypes by various companies/research institutions. AWE crosswind systems may differ in the electricity generation mode, the wing type, the take-off/landing approaches and the control mechanisms, to name a few. Each system has characteristics which enhance their performance regarding key factors of AWE exploration at the expense of penalizing others. Hence, deciding for the most appropriate system in a possible AWE implementation, targeting a certain location, is a difficult and uncertain scenario. This paper presents a Multi-Criteria Decision Analysis (MCDA) approach, using the Fuzzy Analytic Network Process (FANP), aiming to determine, from nine alternatives, the most suitable AWE crosswind system for two distinct exploration sites: onshore rural and offshore. The importance of key selection criteria for AWE is presented and discussed, alternatives in each criterion are evaluated and compared and, finally, a prioritization of both alternatives and criteria is obtained. The FANP methodology indicates rigid wing pumping-cycle systems with horizontal takeoff as the most suitable solution for both investigated sites, revealing Aerodynamic Performance, Mass-to-Area Ratio and Controlability as the most relevant factors in the decision.
... Regulations must be implemented in order to certify AWE systems since they must demonstrate their ability to operate safely in order for society to accept them [170,171]. For the purposes of this work, the relative safety of these technologies can be evaluated by taking into account the dangers to property and human life in the event of a flying wing failure and crash. ...
Full-text available
Airborne wind energy (AWE) has received increasing attention during the last decade, with the goal of achieving electricity generation solutions that may be used as a complement or even an alternative to conventional wind turbines. Despite that several concepts have already been proposed and investigated by several companies and research institutions, no mature technology exists as yet. The mode of energy generation, the type of wing, the takeoff and landing approaches, and the control mechanisms, to name a few, may vary among AWE crosswind systems. Given the diversity of possibilities, it is necessary to determine the most relevant factors that drive AWE exploration. This paper presents a review on the characteristics of currently existing AWE technological solutions, focusing on the hardware architecture of crosswind systems, with the purpose of providing the information required to identify and assess key factors to be considered in the choice of such systems. The identified factors are categorized into four distinct classes: technical design factors (aerodynamic performance, mass-to-area ratio, durability, survivability); operational factors (continuity of power production, controllability, takeoff and landing feasibility); fabrication and logistical factors (manufacturability, logistics); and social acceptability factors (visual impact, noise impact, ecological impact, safety).
... Regulations on the use of land are of paramount importance on determining the feasibility of a wind project. The Federal Aviation Administration, for instance, has set up limits on the maximum height of structures that may interfere with aerial navigation, potentially impacting the installation of advanced wind turbines attempting to tap into stronger high-altitude winds [177]. Natural protected areas or aquifer recharge zones may impact new wind farms or the expansion of current installations. ...
Full-text available
Significantly growing wind energy is being contemplated as one of the main avenues to reduce carbon footprints and decrease global risks associated with climate change. However, obtaining a comprehensive perspective on wind energy considering the many diverse factors that impact its development and growth is challenging. A significant factor in the evolution of wind energy is technological advancement and most previous reviews have focused on this topic. However, wind energy is influenced by a host of other factors, such as financial viability, environmental concerns, government incentives, and the impact of wind on the ecosystem. This review aims to fill a gap, providing a comprehensive review on the diverse factors impacting wind energy development and providing readers with a holistic panoramic, furnishing a clearer perspective on its future growth. Data for wind energy was evaluated by applying pivot data analytics and geographic information systems. The factors impacting wind energy growth and development are reviewed, providing an overview of how these factors have impacted wind maturity. The future of wind energy development is assessed considering its social acceptance, financial viability, government incentives, and the minimization of the unintended potential negative impacts of this technology. The review is able to conclude that wind energy may continue growing all over the world as long as all the factors critical to its development are addressed. Wind power growth will be supported by stakeholders’ holistic considerations of all factors impacting this industry, as evaluated in this review.
... Histogram of the fuzzy engine output values for the conducted nominal flight is shown in Figure 7. Energy Envelope: Maximum allowed kinetic energy is set to 100 kJ considering the potential damage impact of a AWES for the worst case scenario [16] [15] and the energy based airworthiness categorization for civil unmanned aircraft systems proposed in [3]. Table 3. Maximum observed kinetic energy levels for nominal flight case Table 3 shows the observed maximum levels of translational and rotational kinetic energy. ...
Full-text available
Airborne wind energy (AWE) systems use tethered flying devices to harvest wind energy beyond the height range accessible to tower-based turbines. AWE systems can produce the electric energy with a lower cost by operating in high altitudes where the wind regime is more stable and stronger. For the commercialization of AWE, system reliability and safety have become crucially important. To reach required availability and safety levels, we adapted an fault detection, isolation and recovery (FDIR) architecture from space industry. This work focuses on, "flight anomaly detection" layer of the FDIR. Tests verifies that proposed architecture is capable of detecting flight anomalies without generating false alarms.
... This power loss is device-specific and depends on the control strategy and is therefore not considered here. The first commercial AWE initiatives envisage a maximum operational height of 500 m because operation at higher altitudes requires more complex system designs (Watson et al., 2019, p. 4) and legislative procedures (Salma et al., 2018). For the wind resource representation for AWE, it is thus desirable to have wind data at least up to this height. ...
Full-text available
Airborne wind energy (AWE) systems harness energy at heights beyond the reach of tower-based wind turbines. To estimate the annual energy production (AEP), measured or modelled wind speed statistics close to the ground are commonly extrapolated to higher altitudes, introducing substantial uncertainties. This study proposes a clustering procedure for obtaining wind statistics for an extended height range from modelled datasets that include the variation in the wind speed and direction with height. K-means clustering is used to identify a set of wind profile shapes that characterise the wind resource. The methodology is demonstrated using the Dutch Offshore Wind Atlas for the locations of the met masts IJmuiden and Cabauw, 85 km off the Dutch coast in the North Sea and in the centre of the Netherlands, respectively. The cluster-mean wind profile shapes and the corresponding temporal cycles, wind properties, and atmospheric stability are in good agreement with the literature. Finally, it is demonstrated how a set of wind profile shapes is used to estimate the AEP of a small-scale pumping AWE system located at Cabauw, which requires the derivation of a separate power curve for each wind profile shape. Studying the relationship between the estimated AEP and the number of site-specific clusters used for the calculation shows that the difference in AEP relative to the converged value is less than 3 % for four or more clusters.
... Kruiff and Ruiterkamp 15 outline the civil aviation standards and design processes that are applied by Ampyx Power B.V. for rigid-wing AWE system development. Salma et al 16 describe the aviation-related risks introduced by AWE systems and give an overview of existing and expected regulations for AWE systems. Stoeckle 17 proposes an FDIR approach for autonomous parafoils that resemble kites with suspended control unit. ...
Full-text available
Airborne wind energy systems use tethered flying devices to harvest wind energy beyond the height range accessible to tower‐based wind turbines. Current commercial prototypes have reached power ratings of up to several hundred kilowatts, and companies are aiming at long‐term operation in relevant environments. As consequence, system reliability, operational robustness, and safety have become crucially important aspects of system development. In this study, we analyze the reliability and safety of a 100‐kW technology development platform with the objective of achieving continuous automatic operation. We first outline the different components of the kite power system and its operational modes. In the next step, we identify failure modes, their causes, and effects by means of failure mode and effects analysis (FMEA) and fault tree analysis (FTA). Potentially hazardous situations and mechanisms which can render the system nonoperational are identified, and mitigation measures are proposed. We find that the majority of these measures can be performed by a failure detection, isolation, and recovery (FDIR) system for which we present a hierarchical architecture adapted from space industry.
... A majority of the currently pursued development projects aims at ground-based conversion employing crosswind operation in a pumping cycle [9e11]. Technological challenges are the reliability and robustness of the flying systems [12,13], reducing the land surface use [14] and the regulatory framework [15,16]. ...
Full-text available
We compare the available wind resources for conventional wind turbines and for airborne wind energy systems. Accessing higher altitudes and continuously adjusting the harvesting operation to the wind resource substantially increases the potential energy yield. The study is based on the ERA5 reanalysis data which covers a period of 7 years with hourly estimates at a surface resolution of 31 31 km and a vertical resolution of 137 barometric altitude levels. We present detailed wind statistics for a location in the English Channel and then expand the analysis to a surface grid of Western and Central Europe with a resolution of 110 x 110 km. Over the land mass and coastal areas of Europe we find that compared to a fixed harvesting height at the approximate hub height of wind turbines, the wind power density which is available for 95% of the time increases by a factor of two.
Conference Paper
Full-text available
Full-text available
Airborne wind energy (AWE) systems use tethered flying devices to harvest higher-altitude winds to produce electricity. For the success of the technology, it is crucial to understand how people perceive and respond to it. If concerns about the technology are not taken seriously, it could delay or prevent implementation, resulting in increased costs for project developers and a lower contribution to renewable energy targets. This literature review assessed the current state of knowledge on the social acceptance of AWE. A systematic literature search led to the identification of 40 relevant publications that were reviewed. The literature expected that the safety, visibility, acoustic emissions, ecological impacts, and the siting of AWE systems impact to which extent the technology will be accepted. The reviewed literature viewed the social acceptance of AWE optimistically but lacked scientific evidence to back up its claims. It seemed to overlook the fact that the impact of AWE’s characteristics (e.g., visibility) on people’s responses will also depend on a range of situational and psychological factors (e.g., the planning process, the community’s trust in project developers). Therefore, empirical social science research is needed to increase the field’s understanding of the acceptance of AWE and thereby facilitate development and deployment.
Technical Report
Full-text available
A Review of Current and Prospective Factors for Classification of Civil UAS
Full-text available
Airborne wind energy is an emerging field in the renewable energy technologies that aims to replace the use of fossil fuels for energy production on an economical basis. A characteristic feature of the various concepts that are currently pursued is the use of tethered flying devices to access wind energy at higher altitudes where the wind is more consistent. This booklet contains 70 abstracts that were presented at the Airborne Wind Energy Conference 2015 (AWEC 2015), which was held from 15-16 June 2915 at Delft University of Technology. Further included are 37 additional full page photos and illustrations, mainly of prototypes characterising the state of airborne wind energy technology in 2015.
Full-text available
Abstract Among novel technologies for producing electricity from renewable resources, a new class of wind energy converters has been conceived under the name of Airborne Wind Energy Systems (AWESs). This new generation of systems employs flying tethered wings or aircraft in order to reach winds blowing at atmosphere layers that are inaccessible by traditional wind turbines. Research on AWESs started in the mid seventies, with a rapid acceleration in the last decade. A number of systems based on radically different concepts have been analyzed and tested. Several prototypes have been developed all over the world and the results from early experiments are becoming available. This paper provides a review of the different technologies that have been conceived to harvest the energy of high-altitude winds, specifically including prototypes developed by universities and companies. A classification of such systems is proposed on the basis of their general layout and architecture. The focus is set on the hardware architecture of systems that have been demonstrated and tested in real scenarios. Promising solutions that are likely to be implemented in the close future are also considered.
Full-text available
The combination of lightweight flexible-membrane design and favorable control characteristics renders tethered inflatable airplanes an attractive option for high-altitude wind power systems. This paper presents an analysis of the flight dynamics and stability of such a kiteplane operated on a single-line tether with a two-line bridle. The equations of motion of the rigid-body model are derived by Lagrange's equation, which implicitly accounts for the kinematic constraints due to the bridle. The tether and bridle are approximated by straight line elements. The aerodynamic force distribution is represented by four discrete force vectors according to the major structural elements of the kiteplane. A case study comprising analytical analysis and numerical simulation reveals that the amount and distribution of lateral aerodynamic surface area is decisive for flight dynamic stability for the specific kite design investigated. Depending on the combination of wing dihedral angle and vertical tail plane size, the pendulum motion shows either diverging oscillation, stable oscillation, converging oscillation, aperiodic convergence, or aperiodic divergence. It is concluded that dynamical stability requires a small vertical tail plane and a large dihedral angle to allow for sufficient sideslip and a strong sideslip response.
Several wind energy concepts utilize airborne systems that contain lighter-than-air gas, which supplements aerodynamic lift and expands these systems' available operating regimes. While lighter-than-air systems can incorporate the traction and crosswind flight motions of their heavier-than-air counterparts, several lighter-than-air concepts have also been designed to deliver large amounts of power under completely stationary operation and remain aloft during periods of intermittent wind. This chapter provides an overview of the history of LTA airborne wind energy concepts, including the design drivers and principal design constraints. The focus then turns to the structural and aerodynamic design principles behind lighter than air systems, along with fundamental flight dynamic principles that must be addressed. A prototype design developed by Altaeros Energies is examined as an example of the application of these principles. The chapter closes with suggestions for future research to enable commercially-viable LTA systems.
The advances in the design and testing of a 60 kW Yo-Yo AWE generator are presented. The generator uses power kites, linked to the ground by two tethers, reeled on two drums that are connected to two electric drives. The flight of the wings is tracked using on-board wireless instrumentation and it is suitably driven by a ground control unit, through differentially pulling of the tethers. Electricity is generated at ground level obtained by continuously performing a two-phase cycle: a traction one, where the kite unreel the tethers, inducing energy generation through rotation of electric drives. When the maximum tether length is reached, the drives act as motors, to reel back the tethers to start another traction phase. The main components (electro-mechanical structure, sensors and data communication, energy management system, hardware and software for real-time control) are described. Results are presented from some of tests until now performed and the experimental energy and power values are compared with the theoretical optimal value based on the simplified analysis in Loyd's seminal paper as well with computer simulations based on the model and control strategy developed by Kitenergy research group.
EnerKite GmbH designed, built and demonstrated a three line AWE system. This article presents history of the enterprise and the decisions involved. The built ground station is described in detail, and flight data obtained during the course of a year in development is presented.KeywordsWind SpeedTurbulence IntensityController DevelopmentUltrasonic AnemometerHorizontal Axis Wind TurbineThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
SkySails develops and markets large automated towing kite systems for the propulsion of ships and for energy generation. Since 2008 pilot customer vessels have been operating propulsion kites in order to reduce fuel costs and emissions. In this contribution the SkySails towing kite technology is introduced and an overview over its core components kite, control pod, towing rope, and launch and retrieval system is provided. Subsequently the principles of force generation and propulsion are summarized. In the following part the system's application to airborne wind energy generation is presented, where the kite forces are used to pull the towing rope off a drum, powering a generator in the process. When the maximum tether length is reached, the kite is reeled back to the starting point using the generator as a motor. A functional model was constructed and successfully tested to prove the positive energy balance of this so-called pumping mode energy generation experimentally. An evaluation of the technology's market potential, particularly for offshore wind farms, concludes the contribution.
Conference Paper
This paper gives an overview of the conceptual operation and control considerations of the PowerPlane, an airborne wind energy concept that generates power using a tethered airplane and a generator on the ground. The concept is discussed by means of basic aerodynamics, neglecting the mass of the airplane, considering launch, power generation and landing, performance criteria and power output to provide a qualitative understanding of the system. For the actual operation of the system special attention, compared to conventionally operated airplanes, is demanded by the control system because of the link between airplane and generator. The differences between free and tethered flight are elaborated.