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

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

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

Carbon pricing and inflation expectations: evidence from France

This paper studies the impact of carbon pricing on firms’ inflation expectations and discusses the potential implications for what constitutes the core of most central banks’ mandate: price stability. Carbon policy shocks are identified from high-frequency changes in carbon futures price around regulatory events. The shock series is combined with French firm-level survey data. We document that a change in the price of carbon increases firms’ inflation expectations. We then investigate how firms’ business conditions are affected by carbon policy shocks and we find that firms’ own expected and realized price growth respond similarly to inflation expectations. The effect on price expectations is more persistent than on actual price growth leading to positive forecast errors in the medium-/long-run. We also show that a sizable share of the increase in inflation expectations is due to indirect effects. Firms rely on their own business conditions to form expectations about the aggregate price dynamics. Therefore, the expected positive growth in their own prices significantly contributes to the observed increase in inflation expectations. Finally, we study how firms’ responses are heterogeneously influenced by the shocks based on the share of input costs devoted to energy expenditures. We find that high energy-intensive firms tend to overreact relatively more in terms of their own price expectations compared to the actual price change the shocks induce

Il rinforzo muscolare eccentrico in prevenzione agli infortuni ai muscoli ischio-crurali: revisione basata sull'evidenze

Introduzione: Le lesioni muscolari agli ischiocrurali sono fra i più frequenti infortuni in cui incorre uno sportivo che compie gesti atletici come corsa, scatti e decelerazioni, cambi di direzione e salti. L’eziologia lesiva di questi muscoli dimostra come la stragrande maggioranza degli infortuni avvenga durante una contrazione eccentrica, dove i muscoli esercitano la loro principale funzione. Si è deciso di indagare l’efficacia del rinforzo muscolare eccentrico in prevenzione agli infortuni a tale gruppo muscolare. Obiettivo: Ricercare le evidenze in letteratura sull’efficacia del rinforzo muscolare eccentrico in prevenzione agli infortuni al gruppo muscolare degli ischiocrurali. Metodi: La ricerca è stata svolta presso le principali banche dati biomediche, includendo le Revisioni Sistematiche pubblicate negli ultimi 10 anni in lingua inglese, che indagassero l’efficacia di un intervento comprendente il rinforzo muscolare eccentrico ai muscoli ischiocrurali su una popolazione di sportivi, e i cui outcome misurassero l’incidenza degli infortuni. Risultati: Sono stati selezionati 3 studi, valutati tramite AMSTAR Checklist. I risultati raccolti dagli autori valutano positivamente, con più o meno evidenza scientifica, l’efficacia del rinforzo muscolare in prevenzione agli infortuni ai muscoli ischiocrurali, nel contesto in cui sono stati somministrati. Una revisione dimostra come la compliance all’intervento mostrata dai partecipanti influenzi significativamente i risultati ottenuti. Conclusioni: I risultati ottenuti dalle revisioni suggeriscono il proseguimento delle ricerche riguardanti l’efficacia di tale intervento in prevenzione agli infortuni ai muscoli ischiocrurali, tramite nuovi studi condotti con un rigore metodologico maggiore. I limiti mostrati dagli studi inclusi devono essere usati come orientamento per le future ricerche, nel tentativo di giungere a risultati il più significativi possibili

Study on a Dielectric Elastomer Power Take-Off for Wave Surge Energy Converters

The work presents a conceptual analysis and characterization of a dielectric-elastomer-based generator for wave energy conversion. A general overview on Wave Energy Converters (WECs) is presented: a state of the art of the technologies is traced, and some analytical models are proposed for the most significant categories of devices. Successively, attention is focused on Dielectric Elastomer Generators (DEGs) and on their application to WECs. A lozenge-shaped DEG is analyzed: experimental results from mechanical characterization of the polymeric material are reported, and a mathematical model of the device is presented, with the aim of assessing the maximum convertible energy. Successively, a coupled model of an Oscillating Surge WEC exploiting the above mentioned DEG as power take-off is presented

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

Localization of AKAP4 and tubulin proteins in sperm with reduced motility

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

Dielectric elastomers are a promising technology for wave energy harvesting. An optimal system operation can allow maximizing the extracted energy and, simultaneously, reducing wear that would lead to a reduction in the wave harvester lifetime. We pursue a model-based optimization approach to identify optimal controls for wave energy harvesters based on dielectric elastomers. First, a direct method is used for time-discretization of the dielectric elastomer wave energy harvester in the optimal control problem. The two conflicting objectives are considered in a multiobjective optimization framework. Considering a periodic, sinusoidal wave excitation, the optimal solution shows turnpike properties for the optimal periodic mode of operation. However, since real wave motion is neither monochromatic nor predictable on longer time horizons, further extensions are pursued. First, we introduce a stochastic wave excitation. Second, an iterative model-predictive control scheme is designed. Due to multiple objectives, the control scheme has to include an automated adaption of the corresponding priorities. Here, we propose and evaluate a heuristic rule-based adaption in order to maintain the damage below target levels. The approach presented here might be used in the future to guarantee for autonomous operation of farms of wave energy harvesters

High-energy behavior of hadronic total cross sections from lattice QCD

By means of a nonperturbative approach to soft high-energy hadron-hadron scattering, based on the analytic continuation of Wilson-loop correlation functions from Euclidean to Minkowskian theory, we shall investigate the asymptotic energy dependence of hadron-hadron total cross sections in lattice QCD: we will show, using best fits of the lattice data with proper functional forms satisfying unitarity and other physical constraints, how indications emerge in favor of a universal asymptotic high-energy behavior of the kind $B \log^2 s$ for hadronic total cross sections.Comment: Talk given (by E. Meggiolaro) at the "16th High-Energy Physics International Conference in Quantum ChromoDynamics" (QCD 12), Montpellier (France), 2-6 July 2012; 4 pages, 1 figure, 2 table