Rigid kite expandable nets

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.

Rigid blade inflow angle test results

Windswept and Interesting is looking forward to seeing how rigid blade expandable nets progress.

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