Joby Energy is developing airborne wind turbines which will operate in the upper boundary layer and the upper troposphere. While knowledge of the tremendous energy in high-altitude wind is not new, recent advances in power electronics, sensors, and control systems now make the technology practical.
Joby Energy’s multi-wing structure supports an array of turbines. The turbines connect to motor-generators which produce thrust during takeoff and generate power during crosswind flight. Orientation in flight is maintained by an advanced computer system that drives aerodynamic surfaces on the wings and differentially controls rotor speeds. A reinforced composite tether transmits electricity and moors the system to the ground. The high redundancy of the array configuration can handle multiple points of failure and remain airborne.
Higher Altitude Wind
Wind at higher altitudes are faster and more consistent than winds near the Earth’s surface and contain more than three times the power providing a phenomenal untapped resource. A comprehensive understanding of winds ranging from the upper boundary layer through the upper troposphere and its availability is critical to the development of our technology. Joby Energy have extensively modeled tropospheric winds using data spanning 29 years (1979 – 2008) to develop global maps of wind speed and wind power. We are currently analyzing regional upper boundary layer wind data.
Learn more about High Altitude Wind.
How Joby’s High-Altitude Wind Turbines Operates
For launch, the turbines are supplied with power to enable vertical take-off. Upon reaching operating altitude, the system uses the power of the wind to fly cross-wind in a circular path. The high cross-wind speeds result in the turbines spinning the generators at high speeds, eliminating the need for gearboxes and increasing efficiency. The energy is transferred to the ground through the electrical tether. During occasional periods of low wind the turbines are powered to land the system safely.
Swept Area Comparison
The power output of a wind generator is proportional to the area swept by the rotor – i.e. double the swept area = double the energy it can capture (power).
The concept of swept area is the key to extracting energy from the wind. The larger the swept area, the greater the amount of energy that is available to the system. Our system sweeps through a large amount of area – as much as eight times that of a relatively-sized surface-based turbine.
A comparison between the energy output potential of a 2 MW conventional turbine operating at 400 feet and a 2 MW Joby Energy airborne wind turbine operating at 2,000 feet shows a significant improvement in capacity factor. Our airborne wind turbine yields a capacity factor of nearly double the conventional turbine.
The Joby Energy system results in significant cost savings because our 2 MW airborne wind turbine produces the energy equivalent of two 2 MW conventional turbines and requires approximately 1/20th of the materials.