Airborne Wind Energy

Introduction

Roland Schmehl

5 September 2025

CC BY 4.0

Outline

Kitepower

Learning objectives

  • Learn what kites are.
  • Understand how kites can be used for wind energy harvesting.
  • Understand the motivation behind airborne wind energy.
  • Investigate what makes kites for airborne wind energy harvesting special?

Kite basics

Photo: Joep Breuer

Definitions

  • A kite is a tethered, heavier-than-air device with aerodynamic components that generate lift and drag forces from the relative flow.

  • A tethered balloon is a lighter-than-air device not using aerodynamic lift, and not considered to be a kite.

  • A kytoon or kite balloon is a tethered device using a mix of aerodynamic and aerostatic lift.

Definitions

Kite

Tethered balloon

Kytoon

Why does a kite fly?

  • A kite does not have a propulsion system, so, why does it actually fly?

  • By anchoring the kite to the ground, the wind creates a relative flow.

  • The relative flow around the lifting body generates the aerodynamic force components lift and drag.

  • Compare this with an aircraft in leveled flight, where the lift component balances the weight force, and the drag component balances the propulsion system’s thrust.

  • Compare this with a glider in steady descent, where the weight force alone balances the lift and drag components.

Why does a kite fly?

Static kite in wind field

Comparison with glider

Static kite in wind field

Steady glider in still atmosphere

Restart glide animation with F5

Difference between kite and aircraft

  • Gravitational force is a lot smaller than the tether force.

Kite flight modes

  • Static flight
  • Towing
  • Reeling
  • Crosswind flight

Crosswind flight

Breukels (2011)

Static vs crosswind flight

Swami Jonard & Jelle Poland

Ubiquitous use of kites

Hobby & arts

Photo couresy Kitepower

2025 Mayo kite festival (Ireland)

Sports (e.g. kitesurfing)

Kite records

Largest kite

“Flag of Kuwait” with 1019 m²

Highest kite

Altitude world record with a train of kites (1919)


Fastest kite

Speed sailing record SP80 of over 108 km/h

Generating energy with kites

Photo: Joep Breuer

Horizontal-axis wind turbine

Airborne wind turbine

Pumping airborne wind energy system

Pumping airborne wind energy system

What is it?

Airborne wind energy (AWE) is the conversion of wind energy into electricity using tethered flying devices. Some concepts combine onboard wind turbines with a conducting tether, while others convert the pulling power of the flying devices on the ground. Replacing the tower of conventional wind turbines by a lightweight tether substantially reduces the material consumption and allows for continuous adjustment of the harvesting altitude to the available wind resource. The decrease in installation cost and increase in capacity factor can potentially lead to a substantial reduction of the cost of wind energy. Wind at higher altitudes is also considered to be an energy resource that has not been exploited so far.

awesco.eu/awe-explained/

What are kites?

Cherubini et al. (2015)

Kites for airborne wind energy

Photo: Helena Schmidt

Kite aero-structural design







Kite control

Cherubini et al. (2015)

Terminology

  • Airborne Wind Energy (AWE)
  • Airborne Wind Power
  • Kite Power
  • High Altitude Wind Energy (HAWE)
  • High Altitude Wind Power (HAWP)

Often used interchangeably
Sometimes used to differentiate technologies.

Most common now is Airborne Wind Energy (AWE)

Analogies between HAWT and AWE system

Rishikesh Joshi

Potential & challenges

Opportunities

  • Consume significantly less material
  • Highly adjustable to wind resource
  • Access to high altitude wind
  • Increased mobility

Challenges

  • More complex than turbines
  • Requires reliable & robust control
  • Depends on high-performance materials
  • Need to revise current regulatory framework

Skysails

References

Breukels, J.: An engineering methodology for kite design, http://resolver.tudelft.nl/uuid:cdece38a-1f13-47cc-b277-ed64fdda7cdf, (2011)
Cherubini, A., Papini, A., Vertechy, R., Fontana, M.: Airborne wind energy systems: A review of the technologies. Renewable and Sustainable Energy Reviews. 51, 1461–1476 (2015). https://doi.org/10.1016/j.rser.2015.07.053

Questions?





kitepower.tudelft.nl

// reveal.js plugins