Abstract
Dielectric elastomer generators (DEGs) are a promising option for the implementation of affordable and reliable sea wave energy converters (WECs), as they show considerable promise in replacing expensive and inefficient power take-off systems with cheap direct-drive generators. This paper introduces a concept of a pressure differential wave energy converter, equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induced pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG’s elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies, potentially achieving large power capture in a wide range of sea states. We propose a modelling approach for the system that relies on potential-flow theory and electroelasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave tank with the aim of investigating the fluid–structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model. The experimental results proved that the device exhibits large deformations of the DEG power take-off over a broad range of monochromatic and panchromatic sea states. The proposed model demonstrates good agreement with the experimental data, hence proving its suitability and effectiveness as a design and prediction tool.
Highlights
Dielectric elastomers are multifunctional polymeric materials that are employed to develop lightweight and low-cost electromechanical transducers, such as actuators or generators [1]
Compared to traditional power takeoff technologies, dielectric elastomers may allow the development of advanced wave energy converters (WECs) architectures capable of converting wave energy into direct current electricity within a wide range of operating sea conditions
We present the results of an experimental campaign in a wave tank facility, aimed at investigating the hydroelastic response of a pressure-differential WEC (PD-WEC) with a styrenic rubber dielectric elastomer generator [10]
Summary
Dielectric elastomers are multifunctional polymeric materials that are employed to develop lightweight and low-cost electromechanical transducers, such as actuators or generators [1]. Compared to traditional power takeoff technologies, dielectric elastomers may allow the development of advanced WEC architectures capable of converting wave energy into direct current electricity within a wide range of operating sea conditions. Experimental proof of concept of DEG oscillating water columns has been recently presented, with test campaigns run both in wave tank facilities [7] and in a real sea basin [8]. These tests proved that DEGbased oscillating water columns are potentially capable of efficiently converting wave power, achieving fullscale equivalent power outputs of several hundreds of kilowatts
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