Effect of the Electrical Energy Conversion on Optimal Cycles for Pumping Airborne Wind Energy

Schnez

2017

Renewable Energy

The problem of launching a tethered rigid aircraft for airborne wind energy generation is investigated. Exploiting well-assessed physical principles, an analysis of four different take-off approaches is carried out. The approaches are then compared on the basis of quantitative and qualitative criteria introduced to assess their technical and economic viability. In particular, the additional power required by the take-off functionality is computed and related to the peak mechanical power generated by the system. Moreover, the additionally required on-board mass is estimated, which impacts the cut-in wind speed of the generator. Finally, the approximate ground area required for take-off is also determined. After the theoretical comparison, a deeper study of the concept that is deemed the most viable one, i.e. a linear take-off maneuver combined with on-board propellers, is performed by means of numerical simulations. The simulation results are used to refine the initial analysis and further confirm the viability of the approach

“…In this way, if a steady state is attained during the ascend, the corresponding angle of attack will match the parameter ϑ 0 , see Eq. (35). Note that the pitch angle ϑ g (i.e.…”

Section: M2mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the take-off of airborne wind energy systems based on rigid wings

Schnez

2017

Renewable Energy

“…In the scientific literature, systems with ground-based generation and soft kites are by far the ones that received the largest attention, with several contributions concerned with aerodynamics [7,5,20,28,6] and controls [8,19,13,33,9,10]. On the other hand, fewer results have been published pertaining to systems with ground-based electricity generation and rigid aircrafts [26,27], and even fewer for system with onboard generators [31]. One cause of such a disparity is the fact that concepts with rigid aircrafts are inherently more complex than those based on soft kites, hence more difficult to study within academia, especially when it comes to experiments.…”

Section: Introductionmentioning

confidence: 99%

A Small-Scale Prototype to Study the Takeoff of Tethered Rigid Aircrafts for Airborne Wind Energy

IEEE/ASME Trans. Mechatron.

Nguyen-Van

Rager

et al. 2017

The design of a prototype to carry out take-off and flight tests with tethered aircrafts is presented. The system features a ground station equipped with a winch and a linear motion system. The motion of these two components is regulated by an automatic control system, whose goal is to accelerate a tethered aircraft to take-off speed using the linear motion system, while reeling-out the tether from the winch with low pulling force and avoiding entanglement. The mechanical, electrical, measurement and control aspects of the prototype are described in detail. Experimental results with a manually-piloted aircraft are presented, showing a good matching with previous theoretical findings. * This is the pre-print of a paper submitted for publication. The authors are with

“…Small-scale prototypes (10-50 kW of rated power) of the mentioned concepts have been realized and successfully tested to demonstrate their power generation functionalities. Moreover, scientific contributions concerned with technical aspects like aerodynamics [10,11,9,16,25], controls [24,12,6,14,21,17,22,34,13,35], resource assessment [5,4], economics [20,36], prototype design [18], and power conversion [30], have recently appeared, gradually improving and expanding our understanding of such systems.…”

Section: Introductionmentioning

confidence: 99%

On the autonomous take-off and landing of tethered wings for airborne wind energy

Van

2016 American Control Conference (ACC)

Schnez

2016

The problem of autonomous launch and landing of a tethered rigid aircraft for airborne wind energy generation is addressed. The system operates with ground-based power conversion and pumping cycles, where the tether is repeatedly reeled in and out of a winch installed on the ground and linked to an electric motor/generator. In order to accelerate the aircraft to take-off speed, the ground station is augmented with a linear motion system composed by a slide translating on rails and controlled by a second motor. An onboard propeller is used to sustain the forward velocity during the ascend of the aircraft. During landing, a slight tension on the line is kept, while the onboard control surfaces are used to align the aircraft with the rails and to land again on them. A model-based, decentralized control approach is proposed, capable to carry out a full cycle of launch, low-tension flight, and landing again on the rails. The derived controller is tested via numerical simulations with a realistic dynamical model of the system, in presence of different wind speeds and turbulence, and its performance in terms of landing accuracy is assessed. This study is part of a project aimed to experimentally verify the launch and landing approach on a small-scale prototype.