Abstract

This talk presents how design optimization methodologies can contribute to realization of energy-sustainable and reliable engineering systems, with the special focus on energy harvesting technologies. Energy harvesting (EH) research has been performed to realize self-powered wireless sensors and small electronics that do not require battery replacement or recharging, by utilizing ambient energy sources such as wind, vibration, sunlight, and heat. This presentation focuses on piezoelectric EH technology to convert ambient vibration energy into electrical energy, and how we can realize effective energy harvesting system using design optimization methodologies. The design challenges for piezoelectric EH devices include: random/stochastic nature of ambient vibration; multiple vibration modes; and design compactness. To address the aforementioned issues and increase the harvested power, three harvester design concepts are proposed: (i) a segment-type harvester, (ii) an EH skin, and (iii) a curved-shell energy harvester using a snap-through mechanism. The segment-type harvester generates electrical energy from multiple modes by separating the piezoelectric material. A CAE-based design automation platform is built for the shape optimization of the harvester and the stochastic design optimization problem is solved for maximizing energy harvesting from random-natured ambient vibration energy and maintaining device durability. The optimal design is experimentally verified with the prototype to convert a HVAC system vibration energy and operate a wireless sensor in real time without battery. The EH skin is proposed to embody a self-powering structure, in a simple process of laminating a thin piezoelectric patch onto a vibrating structure. Topology optimization technique is used to determine the optimal distribution of piezoelectric material and poling direction. Case studies on an outdoor unit and power transformer demonstrated the sustainable power output for wireless sensor operation and design compactness. The curved-shell nonlinear vibration EH device with snap-through mechanism is motivated to obtain high power from broadband excitation frequency. The nonlinear harvester is comprised of a cantilever beam with curved shell implemented in the middle of the beam. When vibrating, the curved shell causes snap-through buckling and the nature of vibration becomes nonlinear. For practical purposes, design uncertainty has been considered and reliability based design optimization was performed and a broadband frequency vibration input is used to obtain reliable power generation capability. Pioneering the use of EH will enable intelligent engineering systems to monitor their state and generate necessary power on their own, and promise far broader impact on energy conservation and structural and bio health monitoring technologies.