Intelligent wind power unit with tandem wind rotors - Wind Power Generation and Wind Turbine Design - page 336

The tandem wind rotors drive the armature of the traditional generator through the
gearbox as shown in Fig. 4. The fl ows and the performances were predicted
numerically, by the quasi-steady strip theory with the experimental wake model
obtained in the wind tunnel, and were compared with the experiments in the full
scale. The paper showed the optimum arrangement of the tandem wind rotors and
the maximum output coeffi cient reaches as high as 0.5 in the full-scale test.
Furthermore, Shen et al. compared the energy production of the counter-rotating
type with that of the shingle rotating type, in the numerical simulation at the actual
velocity fi eld in the island of Sprogo, Denmark [7]. The tandem wind rotors, whose
diameters are 20.5 m, consist of three blades in the commercial Nordtank 500 kW
rotor. The outputs were predicted by the commercial Navier-Stokes code Ellip-
Sys3D, and Fig. 5 shows the predicted annual energy productions (AEP).
Figure 3: The 6 kW prototype wind turbine [ 5 ].
Tandem wind rotors
Gearbox
Generator
Figure 4 : The 30 kW CRWT system [ 6 ].