Field Investigation of a Wake Structure Downwind of a VAWT in a Wind Farm Array

The effects of upwind turbine wakes on the performance of a FloWind 17?m vertical-axis wind turbine (VAWT) were investigated through a series of field experiments conducted at the FloWind wind farm on Cameron Ridge, Tehachapi, California. The field experiment was conducted within a VAWT array consisting of more than nine VAWTs with separations of 3 rotor diameters (3D) crosswind by 8D downwind ina staggered configuration. The array is the upwind three rows of VAWTs in a total of six rows atop the Cameron Ridge plateau. The terrain features in the vicinity are reasonably regular, with an upslope of 7 deg on the average; however, several local irregularities are present. The annual hourly averaged wind speed exceeds 8 m/s at the site. The primary wind season is from March to August,during which the wind is thermally driven because cooler air masses rush through the San Joaquin Valley to replenish the rising hot air masses in the Mojave Desert. As a result, the wind pattern in terms of wind speed and direction is reasonably persistent during this time. In general, medium to high winds exceeding 9 m/s are confined in a narrow wind direction window between 295 and 310 deg.Therefore, turbines were selected to form an array with a major axis of 308 deg.