1. Design and Development of Effective Nonlinear Energy Harvesters Yuan Li; Supervisor: Yeping Xiong Faculty of Engineering and the Environment, University of Southampton, UK. yl16e10@soton.ac.uk; y.xiong@soton.ac.uk Fluid Structure Interactions Research Group FSI Away Day 2012 Background Ambient energy harvesting is also known as energy scavenging or power harvesting, and it is the process where energy is obtained from the environment. The fundamental idea is to convert ambient energy sources or waste energy into usable electricity. Objectives Investigate nonlinear energy flow equation of an oscillator with linear damping to analyze the effect of its smoothness parameter on power transfer of the nonlinear system. Investigate the coupling effect of nonlinear damping and nonlinear stiffness on energy harvesting. Analyze nonlinear energy transmission mechanisms of the nonlinear oscillator and the effects of super-harmonic resonance or combination resonances. Design a model of the oscillator to do corresponding dynamic experiments to evaluate the effect of the nonlinear parameters on the power harvested. This project aims to investigate a new nonlinear energy harvesting system to explore novel energy harvesting mechanism and develop an effective nonlinear energy harvester for applications in maritime engineering. Currently, almost all the commercial applications so far is the time-invariant nature of the environment in which the harvester operates, i.e., the frequency spectrum of the excitation is stationary with respect to time. This limitation is primarily due to the use of linear mechanical resonators. Figure 1. A 1.0×2.25-inch piezoelectric generator for vibration energy harvesting. [2] References: [1] http://www.oceanpowertechnologies.com/res.htm [1] R. Murray, J. Rastegar, Energy-harvesting power sources for a wide range of applications, SPIE Newsroom, 2007. [2] http://www.enocean.com/en/enocean_modules/eco-200/ Figure 2. A Energy converter for motion energy harvesting [3] This study is motivated by a growing recent interest in new energy source in terms of vibration energy harvesting. Nonlinear oscillator has great potential to enhance power transfer as nonlinear interactions may give rise to a broad- band frequency response or multiple resonance peaks and thus increasing the range of effective functions. Aim Nonlinear Oscillator Methodology Power flow analysis provides an effective technique to describe the dynamic performance, accounting for both force and motion characteristics, of any types of systems. This method is based on the universal principle of energy balance and conservation to investigate dynamic systems. It has been proved that power flow approaches can be successfully developed to model complex structures and applied to vibration control in both linear and nonlinear systems. This approach will be used to evaluate the vibration energy harvesting efficiency. An nonlinear oscillator system provides adjustable nonlinearity will be investigated first. This system consists of a mass m linked by two inclined elastic springs. Each spring of stiffness k is pinned to a rigid support. The nonlinearity of this oscillator can be smooth or discontinuous depending on the value of the smoothness parameter. Various of energy generation units, e.g. piezoelectric unit and electromagnetic unit, can be attached on the oscillator to harvest energy from vertical motion. Figure 1. A floating wave energy harvester. [1] Figure 2. The total energy containing in waves equals to twice of the world’s electricity production. (World Energy Council) [1]