Kitemill’s airborne wind energy device sets new record

Airborne wind energy (AWE) uses kite-like devices to harness more powerful and consistent winds than turbines, with a tether transforming the pull force from the kite to a ground-station generator. Kitemill’s KM1 pilot system recently covered more than 500km during five hours of continuous operation, setting what is claimed to be a new record for AWE.

“Our technology performed efficiently and robustly, despite challenging weather conditions,” said Kitemill CEO Thomas Hårklau. “The five hours and 32 minutes of uninterrupted operation included one landing due to low wind. When the wind picked up, the kite relaunched and continued until sunset. The next day, the kite flew for an additional three hours before landing, accumulating a total flight trajectory of over 500km with an average wing load exceeding 3,500N, corresponding to an aircraft with a 350kg payload. This is a strong performance offering an impressive benchmark when compared to general unmanned flying operations around the world.”

Founded in 2008, Kitemill uses a sailplane drone as the ‘kite’ component in its KM1 system, relying on four propellers for taking off and landing. Once airborne, the ground station ensures optimal energy production as it controls the kite and the winch, with sensors on the kite providing data points for the control system to steer and balance the aircraft. The tether is made using braided polyethene fibres which allow for high-end durability while maintaining a low diameter, which is important for maximising energy transfer.

According to Kitemill, AWE is suitable for many more locations than traditional wind energy and requires significantly fewer materials. However, the ground station for the KM1 pilot plant is just 20kW, meaning vast fleets of kites would be required to match the output of the most powerful turbines. Kitemill said AWE can offer an alternative as prime sites for wind farms become scarcer. A recent report from BVG – commissioned by Kitemill - estimated that cumulative global deployment of AWE could reach 5GW by 2035 and 177GW by 2050.

“Operating at heights between 300 and 500 metres we are able unlock vast areas of high-capacity wind power, ensuring a stable energy output,” said Hårklau. “As such, our technology is viable in many more sites compared to established wind technology. This will be an especially important factor in years to come as countries struggle to source suitable wind farm locations.

“In addition, AWE offers increased energy per square km, with around five times the energy density of conventional wind. It also has significantly lower CAPEX – using just 10 per cent of the materials required by wind turbines of the same capacity. Another considerable benefit is the ultra-low environmental impact. Barely visible from the ground, there is minimal environmental interference from construction through to operation. With less investment tied up to any given site, AWE technology can also be easily relocated during its lifespan.”