Process Tab. 1: Measurements Field testing Output power (W) 5.974 22.26 55.29 109.6 192.8 313.9 Wind power coefficient (Cp) 0.250 0.278 0.292 0.297 0.302 0.310 Wind speed (m/s) 4 6 8 10 12 14 Rotor speed (rpm) 163 253 320 412 499 554 Field tests were carried out at the Global Energy Tochigi laboratory in the following conditions: test wind turbine radius, 1.0 m; blade length, 2.5 m; number of blade elements, two; swept area 5m2. The wave pattern of the wind velocity and the rotor speed is almost the same, as seen in figure 6, confirming that the blade is able to cope instantly with the strength and direction of wind. While in the wind tunnel test it reached maximum power output at a tip speed ratio as low as 1.7 for a wind power coefficient of about 0.3, the field test results confirmed that a wind power coefficient of more than 0.4 could be obtained at a tip speed ratio of 2.0. Wind power coefficients of more 0.4 are difficult to obtain, even with large high-efficiency wind generators of the propeller type. Tab. 2: Bellshion performance measurements (field test) Average for minute Time Wind speed Tip speed Tip speed Retor speed Voltage [m/s] [m/s] ratio [rpm] [V] 4.1 4.7 2.9 4.0 6.5 5.9 4.6 4.6 5.5 6.1 5.2 5.7 5.3 4.2 3.2 8.1 10.2 4.8 7.5 12.6 14.0 9.7 10.0 11.6 12.8 11.0 12.2 11.6 8.8 5.9 1.98 2.19 1.63 1.88 1.94 2.36 2.11 2.18 2.12 2.10 2.11 2.15 2.19 2.10 1.86 77 98 46 72 121 133 92 96 111 122 105 117 111 84 57 52.7 53.5 52.1 52.4 55.6 56.3 53.4 53.4 54.5 55.4 54.1 54.8 54.5 53.4 52.3 Electric current [A] 1.60 2.61 0.58 1.43 5.12 4.24 2.28 2.46 3.87 4.73 3.23 4.08 3.62 2.04 0.83 Output Wind speed power [m/s] [W] 82.3 136.7 26.5 71.7 292.5 243.6 122.1 130.8 212.9 264.4 175.6 226.9 198.1 107.4 41.2 5.8 5.7 3.9 5.5 8.1 8.8 6.0 5.8 7.2 7.3 7.0 7.1 6.4 6.1 4.3 Maximum for minute Rotor speed [rpm] 108 118 80 89 149 208 113 114 138 133 124 134 128 119 64 Voltage [V] 53.3 54.4 53.0 52.8 58.2 59.4 54.2 54.0 56.8 56.4 55.1 56.5 56.0 54.7 52.4 Electric current [A] 2.97 4.28 1.60 2.10 8.38 6.89 3.62 3.73 6.74 6.19 5.09 6.42 5.51 4.32 1.02 Output power [W] 158.3 232.8 84.8 110.9 535.1 406.5 196.2 201.4 382.8 349.1 280.5 362.7 307.4 236.3 53.4 14:30 14:31 14:32 14:33 14:34 14:35 14:36 14:37 14:38 14:39 14:40 14:41 14:42 14:43 14:44 No40 May 2008 / JEC Composites Magazine