This paper describes the results of an experimental campaign conducted on a U-Oscillating Water Column (U-OWC) wave energy converter equipped with Dielectric Elastomer Generator (DEG) Power Take-Off (PTO) system. The considered PTO technology has the potential for overcoming some of the limitations associated with the use of traditional self-rectifying turbines. Experiments have been performed in the benign sea test site of the Natural Ocean Engineering Laboratory (NOEL), where the DEG/U-OWC was exposed to sea states with a significant wave height in the range of 0.15 m – 0.45 m and peak spectral periods in the range of 1.8 s – 3.3 s. The aim of this work is to analyze the dynamic response of the coupled DEG-PTO and U-OWC system. The analysis of the experimental data shows that the presence of the DEG determines a slight decrease in the natural period of the water column oscillations. Through the tests, we also demonstrate that a relief valve can be successfully used to actively tune the dynamic response of the system to ensure the safety of the DEG in severe sea-states.

Dielectric Elastomers (DEs) are incompressible rubber-like solids whose electrical and structural responses are highly nonlinear and strongly coupled. Thanks to their coupled electro-mechanical response, intrinsic lightness, easy-manufacturability and low-cost, DEs are perfectly suited for the development of novel solid-state polymeric energy conversion units with capacitive nature and high-voltage operation, which are more resilient, lightweight, integrated, economic and disposable than traditional generators based on conventional electromagnetic technology. Inflated Circular Diaphragm DE Generators (ICD-DEGs) are a special embodiment of polymeric transducer which can be used to convert pneumatic energy into usable electricity. Potential application of ICD-DEGs is as Power Take-Off (PTO) system for wave energy converters based on the Oscillating Water Column (OWC) principle. This paper presents a reduced, yet accurate, dynamic model for ICD-DEGs which features one degree of freedom and which accounts for DE visco-elasticity. The model is computationally simple and can be easily integrated into existing wave-to-wire models of OWCs to be used for fast analysis and real-time applications. For demonstration purposes, integration of the considered ICD-DEG model with a lumped-parameter hydrodynamic model of a realistic OWC is also presented along with a simulation case study.