High altitude wind power systems: A survey on flexible power kites

Abstract

High altitude wind energy (HAWE) is a new field of renewable energy that has received an increasing attention during the last decade. Many solutions were proposed to harness this energy including the usage of kites, which were for a long time considered as child-toys. An overview on HAWE and its exploitation technologies is presented, followed by focusing on the the kite-based systems. Proposed structures and scenarios are presented, discussed and compared.

A feasibility study on the ocean higher altitude strong wind energy utilization system

“…However, ocean space is three-dimensional (3D), so it is appropriate to pay significant attention to higher altitude strong winds [2].…”

Turning angle control of power kites for wind energy

“…Considering turbulence W t in any direction, the resulting wind is W l := W n + W t . The kite velocity is W a := θ a r aφa r a sin θ aṙa T l , (2) and the effective wind, W e := W l − W a . The ratio between the difference in line length, ∆l, and the airfoil wingspan, d, defines the kite roll angle, ψ, and the system input as u := sin ψ = ∆l/d.…”

“…The advantages of this new approach can be better exploited by optimally determining some parameters as tether length, (un)winding speed, and orbit characteristics. Several configurations of such systems based on tethered airfoils have been proposed [2], and a mix of off and online optimization has been used for power maximization, combined with either open or closed orbits 1 .…”

Kite generator system periodic motion planning via virtual constraints

“…These new concepts and are currently heavily investigated by many research groups and start-up companies. Fig.1 shows the main projects mounted in Western Europe (for more details, see the recent survey written by the authors [2]). Kite-based systems are expected to produce huge amounts of power using a simple and safe structure, but they are challenged by a complexity of their modeling and control, since they are nonlinear, constrained, and highly unstable in the open-loop.…”

“…This traction-recovery functioning yields a generating-consumption cycle that needs to be optimized. This is achieved by controlling the kite to follow a certain trajectory via control of the kite's attack and/or roll angle, and the tether's traction that is controlled via the ground generator torque [2]. The trajectory choice is done through a maximization of the produced power, and the kite is controlled to track this trajectory through an orientation mechanism.…”