Green energy techniques, such as harvesting wind energy, is gaining great attention as they can provide environmental-friendly and renewable power sources in this era of energy crisis. Here, we report a triboelectric nanogenerator (TENG) which harvest mechanical energy driven by wind that works as a sustainable power source as well as a self-powered wind speed sensor. By adopting a novel method that employs the rolling motion of polymer beads, which serve as freestanding layers, under the wind speed of 20 m/s, the TENG delivered output voltage up to 17.8 V, output current of 5.3 mu A, and a corresponding output power density of 1.36 mW/cm(2). The correlation between electrical outputs, wind velocity, width of electrode is systematically investigated. Furthermore, the fabricated device is able to generate an electrical energy regardless of the direction of the wind, and it works well even for long term in the surrounding environment. Additionally, the device is small in size and comparatively flat in its structure, further enhancing potential of its application, such as self-powered wind speed sensor, as an effective portable power source that is readily available to be used in our daily life.