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This paper proposes a T-shaped piezoelectric cantilever for generating electric power from fluid flow. The working principle of the device is based on aeroelastic flutter and utilizes a bimorph cantilever with T-shape which hastens occurrence of flutter at a low fluid speed. A prototype device (100×60×30 mm3) was tested in a wind tunnel. The device was found to provide power from a wind speed of 4 m/s and a continuous peak electrical power output of 4.0 mW. The simplicity of the present device consisting of only a bimorph cantilever is considered to be cost effective.

This paper investigates the applicability of an electromagnetic generator with repulsively stacked magnets for harvesting energy from traffic induced bridge vibrations.First, the governing equation for electromechanical coupling is presented. The magnetic field for repulsive pole arrangements is discussed and the model is validated from magnet falling test. The detailed design, fabrication, and test results of a prototype device are presented in the paper. Experimental vibration shaker test is conducted to assess the performance of the energy harvester. Field test and numerical simulation at the 3 rd Nongro Bridge in South Korea shows that the device can generate an average power of 0.12mW from input rms acceleration of 0.25m/s 2 at 4.10Hz. With further frequency tuning and design improvement, an average power of 0.98mW could be potentially harvested from the ambient vibration of the bridge.

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The objective of this study is to improve the cost-effectiveness and production efficiency of wind farms using cooperative control. The key factors in determining the power production and the loading for a wind turbine are the nacelle yaw and blade pitch angles. However, the nacelle and blade angles may adjust the wake direction and intensity in a way that may adversely affect the performance of other wind turbines in the wind farm. Conventional wind-turbine control methods maximize the power production of a single turbine, but can lower the overall wind-farm power efficiency due to wake interference. This paper introduces a cooperative game concept to derive the power production of individual wind turbine so that the total wind-farm power efficiency is optimized. Based on a wake interaction model relating the yaw offset angles and the induction factors of wind turbines to the wind speeds experienced by the wind turbines, an optimization problem is formulated with the objective of maximizing the sum of the power production of a wind farm. A steepest descent algorithm is applied to find the optimal combination of yaw offset angles and the induction factors that increases the total wind farm power production. Numerical simulations show that the cooperative control strategy can increase the power productions in a wind farm.

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