Large Improvements in Wind Resource Utilization Using Quad Array Turbines
Greenward Technologies, Inc., US
Keywords: wind resource, wind turbine arrays, wake convergence, swirl cancellation
Abstract:This presentation involves a recent discovery that is associated with counter-rotating quad arrays of wind turbines that promises a significant increase in energy production per acre of wind resource. We were first alerted to the possible existence of an exceedingly interesting wake flow phenomenon by the results of a computational fluid dynamics study of a quad array that was done for us in February, 2008. The study only considered irrotational flow, since analyzing effects of rotor blade-generated swirl would be well beyond the capabilities of currently-available CFD codes. The study showed the wakes of the four individual rotors apparently converging into a single flow channel at approx. 2.75 rotor diameters (2.75D) downstream and fully restored to free stream velocity at approx. 5D. We have developed a hypothesis for this phenomenon entitled “Wake Convergence plus Swirl Cancellation”.