Modelling and Control of Lozenge-Shaped Dielectric Elastomer Generators

none3noDielectric 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.nonenoneMoretti, G; Fontana, M; Vertechy, RMoretti, G; Fontana, M; Vertechy,

Model-based design and optimization of a dielectric elastomer power take-off for oscillating wave surge energy converters

This paper investigates a new kind of device for producing electricity from the mechanical energy carried by ocean waves. The proposed machine, named poly-surge, is based on an existing sea-bottom hinged surging-flap concept that is equipped with a new power take-off (PTO) system based on a novel soft dielectric elastomer (DE) transducer. DEs are highly deformable polymeric materials that can be used to conceive electrostatic generators relying on capacitance variation. This kind of generators shows a number of features that well match the requirements of a wave energy converter since they are light-weight, low-cost, tolerant to salty/aggressive marine environment, noise-free during operation, and easy to manufacture and install. The considered poly-surge converter employs a parallelogram-shaped DE generator (PS-DEG) arranged in a dual agonist–antagonist configuration, which makes it possible to provide the flap with controllable bidirectional torques. In this paper, first a complete wave-to-wire multiphysics model of the overall system is described that assumes a simplified hydrodynamic response for the hinged-flap and an electro-hyperelastic behaviour of the PS-DEG. Second, a procedure is presented for the dimensioning and optimization of the PS-DEG for given sets of poly-surge flap dimensions, wave-climate information and constraints on both design and operational variables. Finally, simulation results are provided to demonstrate that the poly-surge can achieve quasi-optimal power production with a properly designed agonist–antagonist DEG PTO system

Modeling of a heaving buoy wave energy converter with stacked dielectric elastomer generator

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

Parallelogram-shaped dielectric elastomer generators: Analytical model and experimental validation

Dielectric elastomers are smart materials that can be used to conceive solid-state electromechanical transducers such as actuators, sensors, and generators. Dielectric elastomer generators, in particular, are very promising for energy harvesting applications because they potentially feature large energy densities, good conversion efficiencies, good shock and corrosion resistance, and low cost. In this article, a novel concept of parallelogram-shaped dielectric elastomer generator is presented and analyzed. Parallelogram-shaped dielectric elastomer generators are rotary variable capacitance transducers, which are made by planar dielectric elastomer membranes that are covered with compliant electrodes and clamped along their perimeter to the links of a parallelogram four-bar mechanism. First, an analytical model for the electro-hyperelastic response of the parallelogram-shaped dielectric elastomer generator is described and used to assess the maximum theoretical performances of the device. Then, an experimental case study with a parallelogram-shaped dielectric elastomer generator prototype featuring a natural rubber dielectric elastomer membrane and carbon conductive grease electrodes is presented. Simulation and experimental results demonstrate the practical feasibility of the parallelogram-shaped dielectric elastomer generator concept

Temporal Interpolation Methods for Transient CHT

International audienceThe main objective of this paper is to present a methodology to carry out transient Conjugate Heat Transfer (CHT). Transient thermal interactions between a fluid and a solid are difficult to perform because of their computational cost. Indeed, fluid and solid characteristic times differ by several orders of magnitude. The present method has the aim to speed up the thermal analysis process by coupling an unsteady conduction computation with a sequence of steady CFD computations. This procedure assumes that the influence of fluid unsteadiness is negligible. Moreover, this paper proposes different approaches to interpolate fluid information between two steady CFD computations necessary to the solid solver for moving forward in time. The results obtained with these different approaches are compared with a reference result

Experimental characterization of a new class of polymeric-wire coiled transducers

The recent discovery of a new kind of thermo-Active coiled polymeric wires has opened new perspectives for the implementation of a novel class of actuators that can be easily and effectively manufactured using low-cost materials such as sewing threads or finishing lines. These new devices feature large displacements in response to temperature variations and show very promising performance in terms of energy and power densities. With the aim of providing information and data useful for the future engineering applications of polymeric coiled actuators, a custom experimental test-bench and procedure have been developed and employed to characterise their thermo-mechanical response. Such a test-bench has been designed to run isothermal and isometric tensile tests on a set of sample actuators that are fabricated with a repeatable process. This paper provides technical details on the manufacturing process of such sample actuators and on the design and operation of the test-bench. Preliminary experimental results are finally reported

Temperature-sensitive protein–DNA dimerizers

Programmable DNA-binding polyamides coupled to short peptides have led to the creation of synthetic artificial transcription factors. A hairpin polyamide-YPWM tetrapeptide conjugate facilitates the binding of a natural transcription factor Exd to an adjacent DNA site. Such small molecules function as protein-DNA dimerizers that stabilize complexes at composite DNA binding sites. Here we investigate the role of the linker that connects the polyamide to the peptide. We find that a substantial degree of variability in the linker length is tolerated at lower temperatures. At physiological temperatures, the longest linker tested confers a "switch"-like property on the protein-DNA dimerizer, in that it abolishes the ability of the YPWM moiety to recruit the natural transcription factor to DNA. These observations provide design principles for future artificial transcription factors that can be externally regulated and can function in concert with the cellular regulatory circuitry

analysis of standard and innovative methods for allocating upstream and refinery ghg emissions to oil products

Alternative fuel policies need accurate and transparent methods to find the embedded carbon intensity of individual refinery products. This study investigates different ways of allocating greenhouse gases emissions deriving from refining and upstream crude oil supply. Allocation methods based on mass, energy content, economic value and, innovatively, added-value, are compared with the marginal refining emissions calculated by CONCAWE's linear-programming model to the average EU refinery, which has been adopted as reference in EU legislation. Beside the most important transportation fuels (gasoline, diesel, kerosene/jet fuel and heavy fuel oil), the analysis extends to petroleum coke and refinery hydrogen. Moreover, novel criteria, based on the implications due to hydrogen usage by each fuel pathway, have been introduced to test the consistency of the analyzed approaches

XMatch: A Language for Satisfaction-Based Selection of Grid Services

Grid systems enable the sharing of a large number of geographically-dispersed resources among different communities of users. They require a mapping functionality for the association of users requests expressed in terms of requirements and preferences to actual resources. This functionality should deal with a potentially high number of similar resources and with the diversity of the perceived satisfactions of users. We propose XMatch, a query language enabling the expression of the user request in terms of the expected satisfaction over XML-based representation of available resources. This language offers a compact way for users to express their preferences for Grid resources and enable the maximization of the global preference

Analysis and design of an oscillating water column wave energy converter with dielectric elastomer power take-off

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