Aptitude of Dielectric Elastomer Transducers for Energy Harvesting Generators
Sprache des Vortragstitels:
2010 MRS Spring Meeting, San Francisco, USA
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Dielectric elastomer actuators promise to combine high energy density at low cost and weight when used as transducer for energy harvesting generators. Only sparse research has been done on the aptitude of dielectric elastomer transducers for such energy harvesting applications. Here we present an experimental realization of an energy harvesting cycle operating between two charge reservoirs at different electrical potentials, and analyze its performance in a thermodynamic description with finite element modeling tools. Dielectric elastomer transducers consist of an elastomer membrane sandwiched between a pair of compliant electrodes. From an electrical point of view, such an arrangement is a parallel plate capacitor with variable capacitance. When the elastomer membrane is stretched mechanical energy is stored to be then transformed into electrical energy. Therefore, the system is charged with a small input voltage at the stretched state. Reducing the membrane stretch under open-circuit conditions lifts the fixed amount of charge to a higher electrical potential due to the decrease in capacitance resulting from the deformation. Thus, the fixed amount of charge times the increase in electrical potential is harvested per operation cycle of the device. In our experimental set-up of such a dielectric energy harvester, the mechanical energy is supplied via inflation of an elastomer membrane with compressed air to a balloon shape. The harvesting results are compared with a thermodynamic model of the system. To estimate the maximal harvestable energy per cycle the device is operated close to the material limits of the used elastomer. These limits include the dielectric breakdown strength limiting the maximum useable electrical field, the stretch of rupture limiting the deformation and the borderline of the electromechanical pull-in instability.