Session: 03-05: Advanced Materials and Transduction Applications

Paper Number: 90988

90988 - Numerical Investigation of Bistable Energy Harvesting Based on Silicone Dielectric Elastomer Generators 

Dielectric elastomer generators (DEGs) are a class of electrostatic polymeric transducers able to convert pulsating mechanical energy into electrical energy, by exploiting a variable capacitance principle. Thanks to their large energy density and low cost, DEGs are often regarded as potentially enabling technology in a variety of energy scavenging scenarios, from human motion harvesting for portable electronics recharging, to large-scale electricity generation from ocean waves.

To achieve optimal performance, DEG-based energy harvesters generally feature a resonant design, in which the natural frequency of the harvester (namely, the DEG plus the masses/elastic elements to which it is coupled) is close to the frequency of the mechanical excitation force. In the past, this principle has been applied to the design of large-scale DEG-based wave energy converters, in which the combination of hydrodynamic inertial forces and DEG elastic forces allows setting the natural frequency within the range of typical sea wave frequencies. Major drawbacks of resonant energy harvesting are a sharp fall in performance in off-resonance conditions, and the difficulty of matching the natural frequency of technically relevant natural sources (waves, human motion etc) via small-scale devices, whose natural frequency typically falls within the high frequency range. 

In this study, we present a model and numerical simulation of a bistable DEG made of a silicone dielectric elastomer, with dimensions on the order of centimetres and target power of a few hundreds of milliwatts. Although silicone is one of the most reliable and promising dielectric elastomer materials, its application in DEG is still limited to a few studies, because of its relatively large mechanical stiffness, which makes it hard to adapt to resonant designs. Here, a bistable response is achieved by coupling two antagonist DEGs with a negative-stiffness buckled-beam spring.

By leveraging on bistability, the DEG is able to undergo large jumps between a couple of fixed configurations (and hence, convert a fixed amount of electrical energy per cycle) within a broad range of operating frequencies (on the order of 1 Hz), in spite of its reduced scale and the relatively small amplitude of the excitation load.

In the paper, we present a design for the system, a systematic numerical comparison of the DEG performance in the bistable case and in a monostable configuration (when no negative spring is applied), and a discussion of the influence of the design parameters on the system response and performance.

Presenting Author: Giacomo Moretti Saarland University