A great deal of research has repeatedly demonstrated that piezoelectric energy harvestershold the promise of providing an alternative power source that can enhance or replaceconventional batteries and power wireless devices. Also, ambient vibrations have been the focus as a source due to the amount of energy available in them. By using energy harvesting devices to extract energy from their environments, the sensors that they power can be self-reliant and maintenance time and cost can be reduced. In order to harvest the most energy with the device, the beam's fundamental mode must be excited. However, this is not always possible due to manufacturing of the device or fluctuations in the vibration source. By being able to change thefrequencies of the beam, the device can be more effective in harvesting energy. This workutilizes a shunt capacitor-tuning concept on a piezoelectric bimorph energy harvester. Designparameters are investigated and discussed to achieve the most tuning from the device. Static and dynamic beam and plate models are derived to predict natural frequencies and power and arelater used to compare to experimental results. Results are presented for the tunability of a square cantilever bimorph. In addition, the amount of power able to be harvested from each layer of the bimorph is tested. Finally, several other tuning methods are discussed.
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