Electroactive poly(vinylidene fluoride) based materials: recent progress, challenges and opportunities

A poly(vinylidene fluoride) (PVDF) and its copolymers are polymers that, in specific crystalline phases, show high dielectric and piezoelectric values, excellent mechanical behavior and good thermal and chemical stability, suitable for many applications from the biomedical area to energy devices. This chapter introduces the main properties, processability and polymorphism of PVDF. Further, the recent advances in the applications based on those materials are presented and discussed. Thus, it shown the key role of PVDF and its copolymers as smart and multifunctional material, expanding the limits of polymer-based technologies.FCT (Fundação para a Ciência e Tecnologia) for financial support under the framework of Strategic Funding grants UID/FIS/04650/2019, and UID/QUI/0686/2019 and project PTDC/FIS-MAC/28157/2017, PTDC/BTMMAT/28237/2017, PTDC/EMD-EMD/28159/2017. The author also thanks the FCT for financial support under grant SFRH/BPD/112547/2015 (C.M.C.), SFRH/BPD/98109/2013 (V.F.C.), SFRH/BD/140698/2018 (R.B.P.), SFRH/BPD/96227/2013 (P.M.), SFRH/BPD/121526/2016 (D.M.C.), SFRH/BPD/97739/2013 (V. C.), SFRH/BPD/90870/2012 (C.R.). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including FEDER financial support) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06)

Functional modelling and prototyping of electronic integrated kinetic energy harvesters

The aim of developing infinite-life autonomous wireless electronics, powered by the energy of the surrounding environment, drives the research efforts in the field of Energy Harvesting. Electromagnetic and piezoelectric techniques are deemed to be the most attractive technologies for vibrational devices. In the thesis, both these technologies are investigated taking into account the entire energy conversion chain. In the context of the collaboration with the STMicroelectronics, the project of a self-powered Bluetooth step counter embedded in a training shoe has been carried out. A cylindrical device 27 × 16mm including the transducer, the interface circuit, the step-counter electronics and the protective shell, has been developed. Environmental energy extraction occurs exploiting the vibration of a permanent magnet in response to the impact of the shoe on the ground. A self-powered electrical interface performs maximum power transfer through optimal resistive load emulation and load decoupling. The device provides 360 μJ to the load, the 90% of the maximum recoverable energy. The energy requirement is four time less than the provided and the effectiveness of the proposed device is demonstrated also considering the foot-steps variability and the performance spread due to prototypes manufacturing. In the context of the collaboration with the G2Elab of Grenoble and STMicroelectronics, the project of a piezoelectric energy arvester has been carried out. With the aim of exploiting environmental vibrations, an uni-morph piezoelectric cantilever beam 60×25×0.5mm with a proof mass at the free-end has been designed. Numerical results show that electrical interfaces based on SECE and sSSHI techniques allows increasing performance up to the 125% and the 115% of that in case of STD interface. Due to the better performance in terms of harvested power and in terms of electric load decoupling, a self-powered SECE interface has been prototyped. In response to 2 m/s2 56,2 Hz sinusoidal input, experimental power recovery of 0.56mW is achieved demonstrating that the device is compliant with standard low-power electronics requirements

The design of low-frequency, low-g piezoelectric micro energy harvesters

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 107-112).A low-frequency, low-g piezoelectric MEMS energy harvester has been designed. Theoretically, this new generation energy harvester will generate electric power from ambient vibrations in the frequency range of 200~30OHz at excitation amplitude of 0.5g. Our previous energy harvester successfully resolved the gain-bandwidth dilemma and increased the bandwidth two orders of magnitude. By utilizing a doubly clamed beam resonator, the stretching strain triggered at large deflection stiffens the beam and transforms the dynamics to nonlinear regime, and increases the bandwidth. However, the high resonance frequency (1.3kHz) and the high-g acceleration requirement (4-5g) shown in the testing experiments limited the applications of this technology. To improve the performance of the current energy harvesters by lowering the operating frequency and excitation level, different designs have been generated and investigated. Moreover, a design framework has been formulated to improve the design in a systematic way with higher accuracy. Based on this design framework, parameter optimization has been carried out, and a quantitative design with enhanced performance has been proposed. Preliminary work on fabrication and testing setup has been done to prepare for the future experimental verification of the new design.by Ruize Xu.S.M

Analysis and practical considerations of linear and nonlinear piezoelectric energy conversion and harvesting techniques

La décroissance de la consommation électrique des dispositifs électroniques leur a permis une croissance sans précédent. Néanmoins, les éléments de stockage d énergie (piles et batteries), bien qu ayant initialement promus ce développement, sont devenus un frein à la prolifération des microsystèmes électroniques, de part leur durée de vie limitée ainsi que des considérations environnementales (recyclage). Pour palier à ce problème, la possibilité d exploiter l énergie de l environnement immédiat du dispositif a été proposée et a fait l objet de nombreuses recherches au cours des dernières années. En particulier, la récupération d énergie mécanique exploitant l effet piézoélectrique est l une des pistes les plus étudiées actuellement pour la conception de microgénérateurs autonomes capables d alimenter les dispositifs électroniques. Par ailleurs, dans ce domaine, il a été démontré qu un traitement non-linéaire de la tension de sortie de l élément actif permet d améliorer les capacités de récupération de l énergie vibratoire. L une de ces approches, nommée Synchronized Switch Harvesting on Inductor (récupération par commutation synchronisée sur inductance) et consistant en une inversion de la tension de manière synchrone avec le déplacement, s est montrée particulièrement efficace, pouvant augmenter la quantité d énergie récupérée par un facteur supérieur à 10. Cette dernière conduit à un processus cumulatif qui augmente artificiellement la tension de sortie de l élément piézoélectrique ainsi qu à une réduction du déphasage entre tension et vitesse de déplacement ; ces deux effets conduisant à l augmentation importante des capacités de conversion. Néanmoins, l étude des microgénérateurs d énergie s est quasiment toujours faite en considérant une excitation sinusoïdale, ce qui correspond rarement à la réalité. Peu de travaux expérimentaux, et encore moins théoriques, ont été menés en considérant une excitation large bande ; ceci étant d autant plus vrai pour les dispositifs incluant un élément non-linéaire. Ainsi l objectif de cette thèse est d étudier le comportement des récupérateurs d énergie piézoélectriques interfacés de manière non-linéaire. Pour ce faire, différentes approches seront envisagées, en considérant le processus de commutation comme un auto-échantillonnage du signal, ou en appliquant des théories d analyse stochastique pour quantifier les performances du dispositif. Ainsi, plusieurs formes d excitation appliquée au système pourront être analysées, permettant d étudier la réponse du système sous des conditions plus réalistes. Toujours dans l optique d une implémentation réaliste, un autre objectif de cette thèse consistera à évaluer l impact de la récupération d énergie par couplage sismique sur la structure hôte, démontrant la nécessité d envisager le système dans sa globalité afin de disposer de systèmes performants capables de convertir efficacement l énergie vibratoire sous forme électrique pour un usage ultérieur.A nonlinear interface consisting in a switching device has been proved to improve the piezoelectric harvester performance. Although existing works are usually done under single frequency excitation. practical cases are more likely broadband and random. In addition, the coupling effect due to the harvesting process is also an interesting issue to discuss. In terms of energy conversion process in seismic piezoelectric harvesters, mechanical interactions between host structure and harvester is an essential issue as well. The purpose of this work is to analysis seismic type piezoelectric harvesters from a practical perspective and to provide an optimal design of the latter. The broadband modeling based on the concepts of self-sampling and self-aliasing is described under broadband excitations for the nonlinear interface called "Periodic Switching Harvesting on Inductor" (PSHI). For this technique, the switching device is considered to be turned on at a fixed switching frequency. Then stochastic modeling is applied to have mathematical expressions that can describe broadband performance of the harvester with power spectral density (PSD) function of signals. As the switch is turned on at a given frequency, the modeling can be derived using cyclostationary theory. The effectiveness of stochastic modeling is validated with experimental measurements and time-domain iterative calculations, and the harvester performance under a band-limited noise excitation is discussed under bell-curved spectra excitations. An optimal switching frequency slightly less than twice the harvester resonant frequency is proved to have the optimal power output under the optimal resistive load. This switching frequency is however dependent on the electromechanical coupling factor of the harvester. Another part of this work discusses the interaction between the host structure and the harvester. The analysis is conducted with a Two-Degree-of-Freedom (TDOF) model. An energy conversion loop is therefore formed between the host structure and the harvester, within the harvester and the resistive load. The TDOF model is verified with Finite Element model and experimental work. An optimal mass ratio is proved to provide the maximal power output. The modeling is further applied to a practical self-powered Structural Health Monitoring system providing the best design of the harvester. A practical consideration of the broadband excitation is also introduced showing the effect of frequency detuning between the host structure and the harvester. Compared to constant force factor case, the harvester performance with a constant electromechanical coupling factor is surprisingly with very little decreases due to the mismatching of harvester and host structure resonant.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF

Resilient and Real-time Control for the Optimum Management of Hybrid Energy Storage Systems with Distributed Dynamic Demands

A continuous increase in demands from the utility grid and traction applications have steered public attention toward the integration of energy storage (ES) and hybrid ES (HESS) solutions. Modern technologies are no longer limited to batteries, but can include supercapacitors (SC) and flywheel electromechanical ES well. However, insufficient control and algorithms to monitor these devices can result in a wide range of operational issues. A modern day control platform must have a deep understanding of the source. In this dissertation, specialized modular Energy Storage Management Controllers (ESMC) were developed to interface with a variety of ES devices. The EMSC provides the capability to individually monitor and control a wide range of different ES, enabling the extraction of an ES module within a series array to charge or conduct maintenance, while remaining storage can still function to serve a demand. Enhancements and testing of the ESMC are explored in not only interfacing of multiple ES and HESS, but also as a platform to improve management algorithms. There is an imperative need to provide a bridge between the depth of the electrochemical physics of the battery and the power engineering sector, a feat which was accomplished over the course of this work. First, the ESMC was tested on a lead acid battery array to verify its capabilities. Next, physics-based models of lead acid and lithium ion batteries lead to the improvement of both online battery management and established multiple metrics to assess their lifetime, or state of health. Three unique HESS were then tested and evaluated for different applications and purposes. First, a hybrid battery and SC HESS was designed and tested for shipboard power systems. Next, a lithium ion battery and SC HESS was utilized for an electric vehicle application, with the goal to reduce cycling on the battery. Finally, a lead acid battery and flywheel ES HESS was analyzed for how the inclusion of a battery can provide a dramatic improvement in the power quality versus flywheel ES alone

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

A gravitational torque energy harvesting system for rotational motion

This thesis describes a novel, single point-of-attachment, gravitational torque energy harvesting system powered from rotational motion. The primary aim of such a system is to scavenge energy from a continuously rotating host in order to power a wireless sensor node. In this thesis, a wireless tachometer was prototyped. Most published work on motion-driven energy harvesters has used ambient vibrations in the environment as the energy source. However, none of the reported devices have been designed to harvest energy directly from continuous ambient rotation. There are important applications such as tire pressure sensing and condition monitoring of machinery where the host structure experiences continuous rotation. In this work, it is shown that in many applications, a rotational energy harvester can offer significant improvements in power density over its vibration-driven counterparts. A prototype single point-of-attachment rotational energy harvester was conceived using a simple direct-current generator. The rotational source was coupled to the stator and an offset mass was anchored on the rotor to create a counteractive gravitational torque. This produces a relative angular speed between rotor and stator which causes power to be generated. Power transfer from the generator to a load was maximised by enforcing an input impedance match between the generator’s armature resistance and the input impedance of a boost converter which in this case, functioned as a resistance emulator. Energy storage and output voltage regulation were implemented using supercapacitors and a wide-input buck regulator respectively. When excess power was generated, it was stored in the supercapacitors and during low source rotation speeds, i.e. insufficient harvested power, the supercapacitors will discharge to maintain operation of the interface electronics. A detailed optimisation procedure of a boost converter was conducted in Matlab in order to minimise the power loss, resulting in a maximum voltage gain of 11.1 and measured circuit efficiency of 96 %. A state-space control model of the harvester electronics was developed in the analogue domain using classical control techniques and this showed the system to be closed-loop stable. A final prototype of the rotational energy harvesting system was built and this comprised an input impedance controller, wireless transmitter and tachometer. The entire system has a measured end-to-end efficiency which peaked at 58 % from a source rotation of 1400 RPM with the generator producing 1.45 W under matched load conditions