5 Comparison of fluid-mechanical key indicators : DualWingGenerator laboratory set-up measurements Comparative values of small system 1* Comparative values of small system 2* * For the comparative objects, an electromechanical effectiveness level of 80 % was assumed. On file: prevailing wind speeds in continental central Europe Wind speed R [m/s] 0 50 100 150 200 250 0 2 4 6 8 10 12 Specific output γ [W/m2] 300 DualWingGenerator Small system 2 Small system 1 Wind speed R [m/s] 0.0 0.1 0.2 0.3 0.4 0.5 0 2 4 6 8 10 12 Effectiveness level η [-] DualWingGenerator Small system 2 Small system 1 Specific output (fluid-mechanical) Effectiveness level (fluid-mechanical) Amazing result: ultimate effectiveness level at low wind speeds, as prevail in central Europe Scientific proof of energy efficiency In numerous measurements on a laboratory set-up, the system’s aerodynamic and mechanical effectiveness levels were determined and then compared with the outputs of two conventional wind power stations of the same size. The test system was set up so that the influences on all the key parameters could be adjusted and recorded in a wind tunnel. So-called PIV (particle image velocimetry) measurements were used here to accurately determine the speed distribution on and between the aerofoils over the course of time. Ultimate effectiveness levels at low wind strengths Particularly in the range of the most common wind speeds between 4 and 8 m/s, the DualWingGenerator revealed remarkable outputs compared to small wind power stations. On the laboratory set-up, it achieved a fluid-mechanical effectiveness level of 45 %, whereby up to 59 % is possible in theory. Efficiency levels can therefore be increased considerably in comparison with conventional small systems – especially with low wind strengths, as prevail in continental central Europe. Various fields of use and applications The knowledge acquired leads to completely new ways of using wind generators. Whilst large wind parks have a high land use and, as a consequence, only pay for themselves out at sea, a system like the DualWingGenerator could be installed almost anywhere – even easily on buildings. The local solution works like a sun collector but rather as a wind collector and also reduces the costs for connecting to the mains network. Besides the electric generator for producing electricity, other appliances for tapping the mechanical energy are also conceivable – for example, a compressor for generating compressed air or a water pump for use in process automation. Further development with adaptive wings To increase the efficiency of the system even further, instead of the rigid aerofoils, Festo is also testing adaptive wings with Fin Ray Effect®. The wing profile changes depending on the angle of incidence and the efficiency of the whole system is increased. Continuous testing: whether in a scientific laboratory set-up … … or through the development of the material
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