Rigid kite expandable nets

Published November 7, 2018

Concept sketch of an expandable ring of rigid kite planes

Rigid wing array kite turbines have huge advantages in energy generation.

Power to weight scaling has always been the core problem in Airborne Wind Energy. Kite turbine designs are the key to scaling airborne power systems whilst keeping them lightweight.

These designs exploit classic kite and AWES rules of thumb.

Rigid Blades systems are more efficient than soft blade
Multi-blade systems are even more efficient
Small Rigid Blades tolerate extreme loading with little mass penalty
Small wings are much cheaper per output
Flying as fast as possible through as much air as possible in the power zone is where the power comes from
Net arrays use less line / kite area = less line drag
Maximise Lift / Drag ratio for best results
Smaller wings can operate in a wider wind range
There is no single point failure so nets are safer
Modular elements are easily swapped out to lower O&M cost
Modular elements allow net deployments suited to current weather
Networked kites are passively stable. This lowers control needs
Wide tethering makes for dynamically stable kite positions
Torque is the only way to obtain continuous power
Hundreds of kites use a line more efficiently the one kite
Avoid running lines to avoid worn lines
Specialist lifting kites can support other specialist kites

We’re not just using rules of thumb, were proving new ground too.

Kites can output torque. This was previously thought impossible.
An AWES can operate without a control. Also thought impossible.
Deformations in the ring structure observed in testing proved the theory that kite networks will expand dynamically in rotary flight. This simple fact will enable the testing of huge rotor diameters using minimal material.
Whole net turbine systems can be powered to rotate from the ground station to maintain tension and lift.
Whole net turbine systems can be stalled in mid air with braking on the ground station.
Whole AWES systems can easily be packed, carried and even taken on passenger aircraft as baggage.

Over the summer, Ollie and I got a lot of testing done. Ollie’s PhD now has more test data available than any other academic analysis of an AWES.