Technology

What is Airborne Wind Energy?

Conventional wind turbines have been growing in size over the years. Increased diameter and reaching higher-altitude wind means a significant gain in power output. However, the need of massive towers and fondations inhibts further and further scale-up. Already for the plants of today, planning, transport, and construction take 7 years on average, and go along with a substantial economic risk.

Airborne Wind Energy (AWE) aims to reach high-altitude winds with a fraction of material use. The key idea is to use kites (tethered wings) to extract the wind power and transmit the energy to the ground. Strapping down wind energy generation to the bare minimum required components (wing, tether, generator) is supposed to bring major cost benefits. In addition, wind at higher altitude is generally stronger and more steady.

Several companies have been working on bringing an Airborne Wind Energy systems to market. Common approaches employ a soft or rigid-body kite to either transmit the wind power mechanically to the ground by pulling on the tether or carry generators onboard and transmit electrical energy down to the ground.

Despite many different attempts, we do not see any established AWE system on the market so far. While AWE companies traditionally question that the prototypes of their competitors can also work at larger size, overall, no single one could provide an effective economic advantage over conventional producers.

How do we make the difference?

We believe Airborne Wind Energy needs to be rethought. To succeed on the energy market and obtain the necessary support throughout the product development, the technology needs to convince with an unseen cost benefit.

While our competitors still stick to a single kite, we go the next step. Our patent-pending centrifugally-stiffened three-wing design unlocks an entirely new mode of operation for Airborne Wind Energy. As we add a second and third wing, our system can take-off and land like a helicopter, kept in shape by the centrifugal forces of their own weights. This has multiple important benefits:

Nominal operation
During power generation, our system can remain rotating at the same place in the sky. Unlike our competitors, we do not require to control a single kite on a complex and highly nonlinear periodic path. Instead, the wings behave together like one big rotor, held by tethers in between. The rotor can be controlled based on well-understood algorithms for helicopters.

Take-off and landing
While most competitor systems need to be separately designed for the take-off/landing case and need to transition to/from nominal (power-generating) flight, our rotor simply keeps spinning throughout the complete flight. While competitor wings carry additional weight (motors that can lift the whole wing, but are unused during the majority of the flight), ours use their own lift from take-off to landing and, therefore, remain lightweight and simple.

Scalability
As the kites stabilize each other through the tethers, they can be designed in a simpler way and built at any size, up to megawatt scale. Likewise, our take-off and landing strategy surpasses the scalability limits that our competitors fight with, consuming less energy to takeoff and allowing for more control against wind gusts.

Efficiency
Patent-pending innovations in structure-supporting tether systems allow for longer, high-aspect-ratio wings, which maximizing power generation while minimizing losses.

All these benefits enable our system to produce incredibly cheap power:

14 CHF/MWh LCOE
(target average power production cost over product lifespan for a Megawatt-scale system)

With such high cost efficiency, our technology outperforms conventional (solar/wind/fossil) power plants as well as all other Airborne Wind Energy systems.

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