Airborne wind energy pages 11-15.

Page 11:

2.1. Airborne wind energy (TRL 3-8)

What is airborne wind energy, and where and how is it useful?

Airborne wind energy aims to harness the potential of high-altitude winds that are hundreds or even
thousands of metres above the surface of the Earth, using flying aircraft that are tethered to the ground. Conventional wind turbine designs that are mounted on towers are not tall enough to take advantage of high-altitude wind energy, as even the tallest are only around 200m in height. Wind movements at high altitudes (e.g. 500m+) are much faster than those close to the surface of the Earth (Archer, 2013; Archer and Caldeira, 2009; Bechtle et al., 2019) and thus contain much more kinetic energy. It has been estimated that the total energy contained in high-altitude winds is around 4x the level available to tower-mounted turbines, and 100x the primary energy demand of the entire world (Marvel et al., 2013). An additional advantage for airborne designs over fixed towers is that an airborne system could, in principle, dynamically adjust its height and orientation to maximize its generation output over time, leading to higher capacity factors and better returns on investment (Archer et al., 2014).