Wind Power 2.0: High-Tech 'Dragons' Breathe Electricity

Conventional wind power systems involve hundreds of tons of steel and concrete and are extremely costly and complex to build. An approach based on efficiency is not like this. And so companies all over the world are experimenting with new types of airborne wind power systems. The highlight among these are automated flying objects that generate green electricity economically at heights of several hundred meters.
One of the new players in this market is start-up company EnerKite, based near Berlin. The central element of their airborne wind power system is a wing with a span of ten meters, resembling a stunt kite. The kite, joined by a retaining cable to a generator winch, moves in figure-of-eight spirals at heights of up to 300 meters. As it moves it pulls on the cable, thereby driving the generator. The software system, sensors and two control lines control the wing. Once it reaches the maximum height, it descends automatically to 120 m and the dance begins again.

Cutting production costs in half

EnerKite harvests electricity at far greater heights than the tips of the blades of wind turbines. The benefit in this is that at heights of 300 m, the wind is stronger and more constant, enabling a higher energy yield: Airborne wind power systems can generate power for roughly 90% of the time. Company director, Alexander Bormann, reckons on 6000 hours at full load even in landlocked areas with a poor wind regime. This would enable the autonomous system to generate green electricity for four cents per kilowatt-hour – half the cost of that generated by wind turbines. Those operate for a maximum of 4000 hours per year at full load even in the best conditions.
The EnerKite demonstration unit is mounted on a former fire engine. The system functions in two phases: in phase 1 the kite rises, pulls on the cable and drives the generator winch. In phase 2 the wing is pulled down with minimal energy expenditure, and the process begins again.
The kite-builders aim to go to market in 2020, with a 100-kilowatt system capable of supplying 200 households with electricity. The entire system fits on a truck and is easy to transport. It is therefore ideal for remote regions and for humanitarian assistance in disaster areas. “Three per cent of electricity worldwide is produced using diesel generators. Our systems are just as flexible and mobile, and can easily replace them,” says Bormann. Since they do not form a structural obstacle to the takeoff or landing of aircraft, these airborne power stations can also be used to supply small airports. Enquiries have already been received from Kenya and Tanzania.

Industry giants investing in the new technology

Dutch company, Ampyx Power, is also tapping the wind resources at high altitudes. The company employs a sailplane that flies at up to 450 meters, and that takes off and lands from a platform on autopilot. As with EnerKite, electricity is produced via a generator winch. Unlike its competitor, however, Ampyx intends its system to be used in onshore and offshore windfarms by major energy corporations and by industrial operations with high energy requirements. Energy giant E.ON is already cooperating with Ampyx and investing generously in the new technology.

“We are replacing concrete and steel with the latest technology,” says the Ampyx website. Certainly, the expenditure for materials, installation and logistics is far less than for wind turbines. EnerKite claims 95% less material use and a 75% smaller CO2 footprint. Maintenance and operation are simpler and the impact on the landscape is minimal.

Google muscles in on high-altitude wind technology

Further players in this new market are X-Wind Powerplants from Berlin and the US company Makani Power. Like Ampyx, their target is large-scale customers. In the X-Wind system the kite pulls a fully automated railcar along a rail, thus generating electricity. Makani Power, which has been owned by Internet giant Google since 2013, carries the generators on board the airborne structures. These aircraft have a wingspan of 26 meters, fly at altitudes of 300 meters and generate power from eight propellers driven by the wind. A 500-metre carbon fiber cable links the aircraft to the ground and conducts the electricity downward. For takeoff and landing, the generators are converted to operation as motors.
Text by Gesine Oltmanns
Photos: Ampyx, EnerKite
Animation: EnerKite