Control of an oscillating water column wave energy converter based on dielectric elastomer generator

Abstract

This paper introduces a model-based control strategy for a wave energy converter (WEC) based on dielectric elastomer generators (DEG), i.e. a device that can convert the energy of ocean waves into electricity by employing deformable elastomeric transducers with variable capacitance. The analysed system combines the concept of oscillating water column (OWC) WEC with an inflated circular diaphragm DEG (ICD-DEG). The device features strongly non-linear dynamics due to the ICD-DEG electro-hyperelastic response and the compressibility of the air volume comprised between the water column and the ICD-DEG, while the hydrodynamic loads can be approximated as linear. The optimal control solution that maximises the power extraction of the device is numerically investigated in the case of monochromatic waves over the typical frequency and amplitude ranges of sea-waves. The more realistic case of panchromatic waves is also analysed through the implementation, in simulation environment, of a real-time controller. This regulator is based on a simple sub-optimal control logic that is deduced from the monochromatic case. Performance of the proposed control strategy is illustrated in comparison with unoptimised algorithms.

Modelling and testing of a wave energy converter based on dielectric elastomer generators

“…The CD-DEG sub-model relies on the assumption of single degree-of-freedom lumped-parameter kinematics of deformation, and it is built upon a general CD-DEG model introduced in previous papers [12,21]. From a mechanical point of view, the DEG is modelled as a hyperelastic continuum body [13,22], while from an electrical point of view the dielectric elastomer is assumed to be a perfect dielectric, i.e.…”

“…In earlier works, the combination of DEG–PTO in OWC architectures has been preliminary investigated through theoretical and experimental analysis [11,12], demonstrating the possibility of obtaining promising performance in terms of estimated energy/power output. However, those implementations were based an a very simplified modelling approach and on design solutions which are well conceived for the purpose of small-scale laboratory experiments but are unsuitable to be scaled-up.…”

“…Currently, a new class of electro-mechanical transducers called dielectric elastomer generators (DEGs) is being investigated as an alternative PTO technology in WECs [6][7][8][9][10][11][12]. DEGs are solid state devices based on soft capacitors which exploit deformation-driven capacitance variations to convert mechanical energy into direct-current electricity [13,14].…”

Optimal operation of dielectric elastomer wave energy converters under harmonic and stochastic excitation

“…In [9], an overview on optimal control and MPC approaches for wave energy systems is given. Also, [26] addresses the control problem of DEG‐WEC systems and suggests dynamic programming techniques.…”

“…To the best of the authors' knowledge, our previous work [16] was the first on multiobjective optimization of DEG‐WEC systems. The energy cost function considers the effect of electrical losses within the dielectric elastomer, unlike in [26], and we include an objective for lifetime optimization. Based on a nonlinear system model, in [16], we computed Pareto‐optimal trade‐offs which allow for a reduction of damage by more than 50% while only losing 1% of energy compared to a control that only aims at maximizing the power.…”