Dielectric Elastomer Transducers (DETs) are solid-state electrostatic devices with variable capacitance that can convert electrical energy into mechanical energy and vice-versa. Recent theoretical and experimental studies demonstrated that DETs made of materials like silicone elastomer and natural rubber can operate at very high energy densities. Practical applicability of DETs is strongly affected by their reliability and lifetime, which depend on the maximum strain and electrical loads that are cyclically applied on such devices. To date, very little knowledge and experimental results are available on the subject. In this context, this paper reports on an extensive lifetime assessment campaign conducted on frame-stretched circular DET specimens made of a commercial styrenic rubber membrane subjected to cyclic electrical loading.

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.

In this paper, we present a concept of near/off-shore Oscillating Water Column (OWC) Wave Energy Converter (WEC) that is equipped with a Power Take Off (PTO) unit based on Dielectric Elastomer Generators (DEGs). DEGs are soft/deformable generators with variable capacitance able to directly convert the mechanical energy that is employed for their deformation into electrostatic energy. The proposed WEC is based on an existing tubular collector chamber of an OWC system designed by the company Sendekia, that is combined with an Inflatable Circular Diaphragm (ICD) DEG. This simplified design presents a very reduced number of moving parts showing potentially high efficiency, reliability and noise-free operation. A multi-physics dynamic model of the system is built using time domain linear hydrodynamics coupled with an analytical non-linear electro-hyperelastic model for the DEG-based PTO. The power matrix of the system is calculated for both regular and irregular waves. Some design issues are introduced showing that the electro-elastic response of the DEG provides the system with an additional stiffness that adds up to the hydrostatic stiffness and affects the resonance of the WEC. As a consequence, the geometric shape/dimensions of the OWC chamber and the layout of the DEG diaphragm should be chosen using an integrated procedure aimed at tuning the overall response of the WEC to the spectra a reference wave climate.

This paper introduces a novel architecture of Wave Energy Converter (WEC) provided with a Dielectric Elastomer (DE) Power Take–Off (PTO) system. The device, named Poly–Buoy, includes a heaving buoy as primary interface, that captures the mechanical energy from waves, and a DE Generator (DEG), made by stacked layers of silicone elastomer, that converts mechanical energy into electricity. A mathematical model of the Poly–Buoy is proposed, which includes analytical electro–hyperlastic equations for the DEG and a linear model for wave-buoy hydrodynamics. Procedures for the design and optimization of different layouts and control strategies for the DE–PTO are introduced that specifically consider single–DEG and dual–DEG architectures. A numerical case study is also reported for specific geometrical dimensions of the buoy and specific wave climate data.

Inflated Circular Diaphragm Dielectric Elastomer Generators (CD-DEGs) are a special embodiment of polymeric transducer that can be used to convert pneumatic energy into high-voltage direct-current electricity. Potential application of CD-DEGs is as power take-off system for wave energy converters that are based on the oscillating water column principle. Optimal usage of CD-DEGs requires the adequate knowledge of their dynamic electro-mechanical response. This paper presents a test-rig for the experimental study of the dynamic response of CD-DEGs under different programmable electro-mechanical loading conditions. Experimental results acquired on the test-rig are also presented, which highlight the dynamic performances of CD-DEGs that are based on acrylic elastomer membranes and carbon conductive grease electrodes.

Dielectric Elastomers (DEs) are deformable dielectrics, which are currently used as active materials in mechatronic transducers, such as actuators, sensors and generators. Nonetheless, at the present state of the art, the industrial exploitation of DE-based devices is still hampered by the irregular electro-mechanical behavior of the employed materials, also due to the unpredictable effects of environmental changes in real world applications. In many cases, DE transducers are still developed via trial-and-error procedures rather than through a well-structured design practice, one reason being the lack of experimental data along with reliable constitutive parameters of many potential DE materials. Therefore, in order to provide the practicing engineer with some essential information, an open-access database for DE materials has been recently created and presented in [1]. Following the same direction, this paper addresses the temperature effect on the visco-hyperelastic behavior of two DE candidates, namely a natural rubber (ZRUNEK A1040) and a well-known acrylic elastomer (3M VHB 4905). Measurements are performed on pure shear specimens placed in a climactic chamber. Experimental stress-strain curves are then provided, which makes it possible to predict hyperelasticity, plasticity, viscosity, and Mullins effect as function of the environmental temperature. Properties of these commercial elastomeric membranes are finally entered in the database and made available to the research community.

This erratum corrects errors that appeared in the paper “Modeling of an Oscillating Wave Surge Converter With Dielectric Elastomer Power Take-Off” which was published in Proceedings of the ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering, Volume 9A: Ocean Renewable Energy, V09AT09A034, June 2014, OMAE2014-23559, doi: 10.1115/OMAE2014-23559.

This paper introduces a novel concept of Oscillating Wave Surge Converter, named Poly-Surge, provided with a Dielectric Elastomer Generator (DEG) as Power Take-Off (PTO) system. DEGs are transducers that employ rubber-like polymers to conceive deformable membrane capacitors capable of directly converting mechanical energy into electricity. In particular, a Parallelogram Shaped DEG is considered. In the paper, a description of the Poly-Surge is outlined and engineering considerations about the operation and control of the device are presented. In addition, a mathematical model of the system is provided. Linear time-domain hydrodynamics is assumed for the primary interface, while a non linear electro-hyperelastic model is employed for the DEG PTO. A design approach for the Poly-Surge DEG PTO is introduced which aims at maximizing the energy produced in a year by the device in a reference wave climate, defined by a set of equivalent monochromatic wave conditions. A comparison is done with two other WEC models that employ the same primary interface but are equipped with mathematically linear PTO systems under optimal and suboptimal control. The results show promising performance of annual energy productivity, with slightly reduced values for the Poly-Surge, even if a very basic architecture and control strategy are assumed.

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.

Dielectric Elastomers (DEs) are a very promising technology for the development of energy harvesting devices based on the variable-capacitance electrostatic generator principle. As compared to other technologies, DE Generators (DEGs) are solid-state energy conversion systems which potentially feature: 1) large energy densities, 2) good energy conversion efficiency that is rather independent of cycle frequency, 3) easiness of manufacturing and assembling, 4) high shock resistance, 5) silent operation, 6) low cost. Envisioned applications for DEGs are in devices that convert ocean wave energy into usable electricity. This paper introduces the Lozenge-Shaped DEG (LS-DEG) that is a specific type of planar DE transducer with one degree of freedom. A LS-DEG consists of a planar DE membrane that is connected along its perimeter to the links of a parallelogram four-bar mechanism. As the mechanism is put into reciprocal motion, the DE membrane varies its capacitance that is then employed as a charge pump to convert external mechanical work into usable electricity. Specifically, this paper describes the functioning principle of LS-DEGs, and provides a comparison between different hyper-elastic models that can be used to predict the energy harvesting performances of realistic prototypes. Case studies are presented which address the constrained optimization of LS-DEGs subjected to failure criteria and practical design constraints.

In the next future Virtual Reality technologies will allow the dramatic reduction of the development time of “soft products”, like textiles, household papers and car interiors, making possible the subjective assessment of their fine mechanical properties, through the realistic rendering of the visual and haptic sensations arising during the physical interaction of these objects with the human hand. This paper deals with the development issues of a complete haptic interface, able to allow the simultaneous generation on the human hand of both kinesthetic and tactile stimulations. The device has been conceived for the haptic rendering of textiles and is composed by a multipoint force feedback device, in charge of generating arbitrary resultant forces on the index and thumb fingertips, and by two independent tactile arrays, in charge of generating time and spatially distributed tactile stimulations on the palmar surface of the two fingertips. After a brief discussion of the reference configuration selected for the whole haptic interface, it has been reported the functionalities, architecture and performances of the realized force feedback device, hosting the tactile arrays. Then the papers focuses on the development issues of a suitable tactile array, discussing its general requirements and the selected architecture. Finally the technical solutions selected for the implementation of its main components and their experimental evaluations are reported.