The world's first 4,000-meter-class airborne wind power system has successfully completed its test flight in Yueyang, Hunan Province, China.

The system uses a helium-filled aerostat to lift lightweight generation modules to altitudes of several thousand meters, where it continuously generates power from stable high-altitude winds and transmits it to the ground via a tether. It can operate at altitudes of up to 4,000 meters, delivers output voltages of 10–35 kV, and has a designed service life of 20 years.

High-altitude wind, an as-yet largely undeveloped frontier of new energy, offers high wind speeds, stable direction and high energy density—and enormous potential. In August, the S4000 system validated at its base its ability to withstand extreme conditions, including high altitude, intense UV radiation and large temperature swings. This urban test flight focused primarily on whether the system can fly safely and reliably near citizens and crowds—the core areas of electricity demand and the primary service areas of new power supply systems.

The successful urban test flight validated the reliability of the entire airborne system, as well as the feasibility and completeness of engineering delivery under real urban operating conditions and the capability for rapid on-site deployment, which laid a solid foundation for airborne wind power equipment to move from technical validation toward industrial commercialization.