Airborne Wind Energy Conference 2017 Book of Abstracts

Airborne Wind Energy – Challenges and Opportunities Based on Experiences from
the Conventional Wind Industry
Henrik Stiesdal
Department of Wind Energy, Technical University of Denmark
Henrik Stiesdal
Honorary Professor
Technical University of Denmark
Department of Wind Energy
Risø Campus
Frederiksborgvej 399, Building 118
Denmark
hsties@dtu.dk
www.vindenergi.dtu.dk
Airborne Wind Energy Systems (AWES) have significant
potential to expand the field of wind power by capturing
energy at altitudes that can not be reached with groundbased
wind turbines, thereby benefiting from higher and
more persistent winds. However, while the potential advantages
of AWES are clear, the full range of challenges
may not be equally clear. Based on experiences from
the development, expansion and maturing of the conventional
wind industry, the challenges facing the AWES industry
are of such magnitude that it cannot be stated with
certainty that this industry will be commercially viable.
The operational challenges vary considerably as a function
of the airborne wind energy system (AWES) concept.
Still, for all concepts, the requirements for operational
reliability and robustness under conditions of long service
intervals are high, much higher than known from
other, apparently similar industries. The conventional
wind industry has had to learn the hard way that experiences
could not readily be transferred from other industries
due to the much higher equipment demands posed
by wind industry application. The same will apply to the
AWES industry, but aggravated by the requirements for
low weight.
The environmental challenges are considerable for all
types of wind turbines, and in tendency, most will be
more severe for AWES. Wind does not always behave in
accordance with the textbooks’ descriptions of smooth
logarithmic wind shears and well-defined turbulence
spectra. In addition to normal turbulence, large wind
turbines often experience high and uneven shear conditions,
pronounced veer, and gust front passages. Due to
the larger areas swept by AWES and the significant altitude
variations, these phenomena are likely to affect
AWES even more than conventional wind turbines. Furthermore,
wind turbines experience other environmental
conditions having a detrimental effect on performance:
rain, snow, hail and icing, and insect fouling. Finally, all
large wind turbines are at some point hit by lightning and
also AWES must be able to handle lightning.
The regulatory challenges for AWES comprise a combination
of challenges shared by the conventional wind industry
and challenges particular to the AWES industry. Experience
shows that radar interference, noise emission, and
visual impact are limiting factors for onshore wind power
deployment. In addition to these challenges, AWES have
particular challenges regarding aviation and on-ground
safety. The scaling challenges are of particular concern
regarding AWES. Experience shows that the conventional
wind industry needed megawatt-scale turbines to reach
grid parity. However, the square-cube law will severely
limit the size potentials for AWES, and new thinking will
be required to reach competitive infrastructure cost levels.
In the face of all these challenges, it is perhaps difficult
not to lose heart. However, the AWES opportunities
remain unaffected – subject to the above challenges,
the potential to change the game by exploiting hitherto
inaccessible wind resources, using lightweight, low-cost
equipment.
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