Posters

Abstract

Method The innovated method compares with an ordinary square grid of standardised horizontal axis wind turbines spaced 10 sweep area diameters (D) apart, each turbine being permanently located in the node intersection of rows and columns and adapted to yaw towards the omnidirectional wind eye. Wind tower diameter is ≤0,05D. An innovative condensed square grid is arranged by permanently installing at least one intermediate standard turbine equidistantly and in line between any two adjacent node turbines. Thus, all tubines will be spaced ≤5D apart. Should instead two intermediate turbines be installed, turbines would be spaced 3,3D apart while three intermediates would stand 2,5D apart. The innovative method is to activate and inactivate all turbines in a strict scheme depending on the change of wind direction between two adjacent 90 degrees quadrants of the omnidirectional windrose. This activation / inactivation scheme is realised by switching the turbine rotation on/off by twisting turbine blades lift/stall. So will all row-turbines be active in wind directions from two opposite quadrants, while the remaining colum-turbines are inactive. In wind directions from the other two opposite quadrants, all the column-turbines will be active and the remaining row-turbines inactive. By this, about one half of the installed turbines will always be in active mode, depending on the number of intermediate turbines. While in operating mode, they will generate electricity plus wind wakes within 10D downwind of a turbine. The other half is always inactive and produces no electricity but wind vortices downwind of the tower, machine house, hub and blade chords. These von Karman vortices would effectively dissipate at ≤50 times the characteristic diameter of ≤0,05D, i.e. at ≤2,5D downwind. As these vortices come short of 2,5D they will not reach any intermediate turbines nor any node turbines downwind. Thus the influence from upstream turbines can be neglected, except for the blockage caused by the condensed rows or columns upstream. The blockage effect reduces the yearly grid output but extends the park lifetime, since the fatigue life of rotating equipment is increased by the square root of blockage change. While the ordinary grid has no such blockage effect, one intermediate turbine results in some blockage and two/three intermediates associate with more. This blockage effect should be verified. Results An ordinary square 10D grid occupied by one 1MW node turbine in each corner will assumingly generate 4MW during operation. With three intermediates, there will be 16 turbines spaced 2,5D apart, totally producing ≈9,5 MW at ≤10 percent blockage, i.e. conservatively. Park lifetime productivity increases by ≈2,49 times compared to the ordinary grid . Capital costs of inactive turbines are balanced by the increased park productivity and cost benefits of occupying only one wind park area instead of two, which is the alternative. Conclusion This innovative condensed square grid by ≈four times the number of installed turbines will generate ≈2,5 times electrical effect during ≈double expected park lifetime as compared to an ordinary wind park located in the same area and operated under the same omnidirectional wind conditions.