High Altitude Wind Kinetic Optimization Embodied within the Turbofoil®

   For wind turbine engineering, an exponential variation in wind speed with height can be defined relative to wind measured at a reference height of 10 meters as:


Turbofoil® High Altitude Wind Kinetic Optimization

   The Hellman exponent depends upon the coastal location and the shape of the terrain on the ground, and the stability of the air. Examples of values of the Hellman exponent are given in the table below:


Location α
Unstable air above open water surface: 0.06
Neutral air above open water surface: 0.10
Unstable air above flat open coast: 0.11
Neutral air above flat open coast: 0.16
Stable air above open water surface: 0.27
Unstable air above human inhabited areas: 0.27
Neutral air above human inhabited areas: 0.34
Stable air above flat open coast: 0.40
Stable air above human inhabited areas: 0.60


   Source: "Renewable energy: technology, economics, and environment" by Martin Kaltschmitt, Wolfgang Streicher, Andreas Wiese, (Springer, 2007, ISBN 3-540-70947-9, ISBN 978-3-540-70947-3), page 55


   Although the above table estimates a Hellman Exponent at α=0.27 for stable air above an open water surface, The Integrated Power Technology Corporation™ prefers to conservatively estimate a Hellman Exponent of α=0.12 to indicate a wind speed at a height of 300m to be 1.32 times greater than at 30m. In latitudes furthest from the equator, colder temperatures form greater air stability, and thus α=0.12 will conservatively estimate practically all wind gradients.


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