Wind energy harvesting based on flow-induced-vibration and impact

To apply MEMS energy harvesting elements in low wind speed environments, it is significant to decrease the critical wind speeds. Impact is used to decrease the applicable wind speeds of flow-induced-vibration wind energy harvesting systems with MEMS harvesting elements in this paper. An impact-based wind energy harvesting system composed of a thin metal sheet, a MEMS piezoelectric energy harvesting element, a rigid stop, a fixture and a bluff body was designed. When wind speed increased to the critical speed, the cantilever composed of the MEMS harvesting element and the metal sheet vibrated and impacted with the rigid stop repeatedly. The impact impulses caused the MEMS harvesting element to vibrate, and the piezoelectric layer of the harvesting element converted the vibration energy into electrical energy. Experimental results show that each impact between the cantilever and the stop caused the MEMS harvesting element to produce large deformation which attenuated freely like a damping system then. The critical wind speed of the prototype is between 3.2 m/s and 3.4 m/s. When wind speed reached 15.9 m/s, the measured RMS voltage and output power of the MEMS harvesting element on a resistor of 100 k Omega were about 406 mV and 1.6 mu W, respectively. (C) 2013 Elsevier B.V. All rights reserved.