Reliability of dielectric elastomer generators for wave energy converters

Abstract

Dielectric elastomer generators (DEGs) show promise for large-scale energy harvesting, particularly in wave energy conversion. This research investigates DEG reliability and performance, exploring electrical, mechanical, and environmental ageing processes. The study investigated the effects of mechanical cycling on the dielectric breakdown strength of silicone elastomers, with a focus on two key phenomena: the Mullins damage and mechanical fatigue. An electro-mechanical reliability model was developed and its outcome used in a novel metric termed levelised energy density. This metric serves to balance energy output and long-term reliability such as defining the optimal operating parameters and providing representative energy densities in the endurance domain.
Two distinct electrical breakdown mechanisms were identified in multilayer DEGs, leading to enhanced size effects and reduced reliability in larger samples. Meanwhile, electrical ageing tests showed dielectric breakdown strength was marginally affected by time under stress. A Weibull competing failure model successfully modelled electrical reliability across various electrode areas, and time exposed to electric field. In the context of wave energy applications, the research investigated the effects of seawater diffusion on silicone dielectric elastomer. While water saturation increased conduction current, its impact on DEG conversion efficiency was minor except at very low stretch amplitudes. However, water saturation significantly reduced the dielectric breakdown strength, which has important implications for wave energy converters and their maximum achievable energy density.
Finally, the findings were analysed in the context of energy harvesting tests conducted on a representative wave energy converter prototype. This analysis allowed for the verification of reliability models and the identification and ranking of key degradation parameters.

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Identifiers

ORCID for Thomas Andritsch: orcid.org/0000-0002-3462-022X

ORCID for Istebreq Saeedi: orcid.org/0000-0002-1254-748X

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