Investigation of bistable piezo-composite plates for broadband energy harvesting

The need to power small electronic components, such as wireless sensor networks, has prompted interest in energy harvesting technologies capable of generating electrical energy from ambient vibrations. There has been a particular focus on piezoelectric materials and devices due to the simplicity of the mechanical to electrical energy conversion and their high strain energy densities compared to electrostatic and electromagnetic equivalents. This paper describes research on an arrangement of piezoelectric elements attached to a bistable asymmetric laminate to understand the dynamic response of the structure and power generation characteristics. The inherent bistability of the underlying structure is exploited for energy harvesting since 'snap-through' from one stable configuration to another is used to strain the piezoelectric materials bonded to the laminate and generate piezoelectric energy. Using high speed digital image correlation, a variety of dynamic modes of oscillation are identified in the bistable harvester. The sensitivity of such vibrational modes to changes in frequency and amplitude are investigated. Electrical power outputs are measured for repeatable snap-through events and are correlated with the modes of oscillation. The typical power generated is approximately 25mW and compares well with the needs of typical wireless senor node applications.