Ram-air Wing Design Considerations for Airborne Wind Energy

Dunker, Storm

doi:10.1007/978-3-642-39965-7_31

Cited by 15 publications

(12 citation statements)

References 12 publications

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“…Durability for fabric wings such as LEI, foil and delta kites, is an issue. Performance is compromised soon and lifetime is usually around several hundred hours [21]. 4.…”

Section: Ground-gen Systems Architectures and Aircraftmentioning

confidence: 99%

“…Once the kite has taken off, the production phase starts: the automatic control drives the kite acting on the two ropes, the kite makes a crosswind flight with 'eight shape' paths; at the same time ropes are unwound causing the winches to rotate; the motor-generators transform mechanical power into electric power. The company aims at retracting the cables with minimum energy consumption thanks to a special maneuver called 'side-slip' or 'flagging' [21]. Side-slip is a different flight mode where the kite aerodynamic lift force is cleared by rewinding at first one rope before the other, which makes the kite lose lift and 'stall' and then, once fully stalled, both ropes are rewound at the same speed and the kite precipitates flying sideways.…”

Section: Kitegen Researchmentioning

confidence: 99%

See 1 more Smart Citation

Airborne Wind Energy Systems: A review of the technologies

Cherubini

Papini

Vertechy

et al. 2015

Renewable and Sustainable Energy Reviews

260

167

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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

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“…Durability for fabric wings such as LEI, foil and delta kites, is an issue. Performance is compromised soon and lifetime is usually around several hundred hours [21]. 4.…”

Section: Ground-gen Systems Architectures and Aircraftmentioning

confidence: 99%

Section: Kitegen Researchmentioning

confidence: 99%

Airborne Wind Energy Systems: A review of the technologies

Cherubini

Papini

Vertechy

et al. 2015

Renewable and Sustainable Energy Reviews

260

167

View full text Add to dashboard Cite

show abstract

“…The present paper focuses on an airborne wind energy system (AWES) with an inflatable membrane wing that is controlled by a suspended cable robot (van der Vlugt et al, , 2019. Compared to rigid-wing aircraft, the aerodynamics of tethered membrane wings are not so well understood and kite development still relies heavily on subjective personal experience and trial and error processes (Breukels, 2011;Dunker, 2013). One reason for this is the aeroelastic two-way coupling of wing deformation and airflow, which can cause complex multi-scale phenomena.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic characterization of a soft kite by in situ flow measurement

Oehler

Schmehl

2019

Wind Energ. Sci.

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Abstract. Wind tunnel testing of large deformable soft kites for wind energy conversion is expensive and in many cases practically not feasible. Computational simulation of the coupled fluid–structure interaction problem is scientifically challenging and of limited practical use for aerodynamic characterization. In this paper we present a novel experimental method for aerodynamic characterization of flexible membrane kites by in situ measurement of the relative flow, while performing complex flight maneuvers. We find that the measured aerodynamic coefficients agree well with the values that are currently used for flight simulation of soft kites. For flight operation in crosswind maneuvers during which the traction force is kept constant, the angle of attack is inversely related to the relative flow velocity. For entire pumping cycles, the measurements show considerable variations in the aerodynamic coefficients, while the angle of attack of the kite varies only in a narrow range. This finding questions the commonly used representation of aerodynamic coefficients as sole functions of the angle of attack and stresses the importance of aeroelastic deformation for this type of wing. Considering the effect of the power setting (identical to the trim) solely as a rigid-body pitch rotation does not adequately describe the aero-structural behavior of the kite. We show that the aerodynamic coefficients vary as functions of the power setting (trim) of the kite, the steering commands and the flight direction.

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“…This holds particularly for leading edge inflatable (LEI) tube kites (see Fig. 1) and other single-skin kite types, since ram air wings have already been investigated systematically for several decades (Dunker, 2013(Dunker, , 2018Johari et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Automatic measurement and characterization of the dynamic properties of tethered membrane wings

2019

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Abstract. We have developed a tow test setup for the reproducible measurement of the dynamic properties of different types of tethered membrane wings. The test procedure is based on repeatable automated maneuvers with the entire kite system under realistic conditions. By measuring line forces and line angles, we determine the aerodynamic coefficients and lift-to-drag ratio as functions of the length ratio between power and steering lines. This nondimensional parameter characterizes the angle of attack of the wing and is varied automatically by the control unit on the towed test bench. During each towing run, several test cycles are executed such that mean values can be determined and errors can be minimized. We can conclude from this study that an objective measurement of specific dynamic properties of highly flexible membrane wings is feasible. The presented tow test method is suitable for quantitatively assessing and comparing different wing designs. The method represents an essential milestone for the development and characterization of tethered membrane wings as well as for the validation and improvement of simulation models. On the basis of this work, more complex maneuvers and a full degree of automation can be implemented in subsequent work. It can also be used for aerodynamic parameter identification.

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Ram-air Wing Design Considerations for Airborne Wind Energy

Cited by 15 publications

References 12 publications

Airborne Wind Energy Systems: A review of the technologies

Airborne Wind Energy Systems: A review of the technologies

Aerodynamic characterization of a soft kite by in situ flow measurement

Automatic measurement and characterization of the dynamic properties of tethered membrane wings

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