Energy Harvesting from Vibration with Alternate Scavenging Circuitry and Tapered Cantilever Beam

Piezoelectric transducers are increasingly being used to harvest energy from environmental vibrations in order to either power remote sensors or charge batteries that power the sensors. In this paper, a new voltage compensation scheme for high-voltage-based (\u3e 100 V ) energy harvesting is introduced, and its fundamental concepts, as well as the operation details, are elaborated. This scheme, when applied to the voltage inversion method [synchronized switch harvesting on inductor (SSHI)], provides an increase of over 14% in harvested power when compared to the parallel inversion method (parallel SSHI) alone and more than 50% in the case of series inversion method (series SSHI). Second, tapered cantilever beams were shown to be more effective in generating a uniform strain profile over rectangular and trapezoidal beams if they are precisely shaped, resulting in a significant increase in harvested power over available methods in the literature from laboratory experimental tests. In addition, a simplified method to design such a beam is introduced. Finally, a field test of the proposed tapered beam is conducted by using a dozer for earth-moving applications, and experimental results are discussed

Design Optimization of Piezoelectric Energy Harvesting Cantilever for Medical Devices

Energy harvesting from the human body is considered as an effective solution for powering biomedical systems. In particular, the piezoelectric energy recovery from mechanical vibrations of the human body represents the most promising solution. The harvested power depends on several factors such as the geometry, the size and materials used for the piezoelectric cantilever. In addition, the reduction and the change of the design of the piezoelectric system constitute a process for increasing the output power. In the present paper, the conventional rectangular shape of the piezoelectric energy harvester is studied and different shapes of cantilever are investigated. We introduced thus a triangular and a new shaped cantilever which permits the enhancement of the scavenged power for low frequencies. In addition, simulations result of various structures are compared and performed by employing finite element method (FEM). Simulations results show that the proposed form generates an electric power of 145 µW at resonant frequency of 8.5 Hz. This novel shape provides more efficient performance compared to other designs

Performance Enhancement of Cantilever Beam Piezoelectric Energy Harvesters

During the last decade, driven by the need, energy harvesting has drawn considerable attention due to the cost-effectiveness and simplicity of the structure. The most important feature or advantage of energy harvesters is their energy sources which are coming from the energy that would be wasted otherwise to the ambient surroundings. Among the three types of energy conversion methodologies, piezoelectric energy harvesters (PEHs) have been highlighted as a self-power source of energy for small wireless sensors with low required power input due to their simple converting structure. While conventional piezoelectric materials possess ideal sensing properties, the microfabrication of these structures typically requires access to the sophisticated equipment and cleanroom facilities. Moreover, the fabrication process is time-consuming and expensive, researchers found it interesting to resort to micro-electromechanical system (MEMS) designs with inexpensive, simple and green-based materials and simple fabrication techniques such as paper. Generally, the paper-based devices have offered significant benefits but their recorded performance is significantly below that of the ones of the commercial smart structures. Their development is still in the early stage of growth and they need to be properly designed to satisfy the general requirements of the commercial products. Geometry optimization, sizing and functionalizing are among the strategies which can be adopted to boost the performance of all types of piezoelectric energy harvesters including the paper-based piezoelectric energy harvesters (PPEH). Therefore, the major contributions of this work are improvement of the performance of piezoelectric energy harvesters using the geometry modification, sizing analysis and functionalizing. In this work, the governing equations of piezoelectric cantilevers based on both Euler-Bernoulli and Timoshenko beam theories are developed and solved using one type of element with a great rate of convergence called superconvergent element (SCE). The theoretical analysis was validated against results published in the open literature and the results indicate that the proposed method yields higher accurate results. Further, the effect of non-uniformity on the electrical output and efficiency of Piezoelectric Energy Harvesters (PEH) are studied. Then, the influence of sizing and application of a series of piezoelectric cantilever energy harvesters on the performance of structure are studied. The effect of the shape of the piezoelectric elements is also investigated below. Eventually, development of functionally graded piezoelectric materials (FGPMs) for non-uniform beams are presented to evaluate the effect of functionalizing

Vibrational energy harvesting for sensors in vehicles

The miniaturization of semiconductor technology and reduction in power requirements have begun to enable wireless self-sufficient devices, powered by ambient energy. To date the primary application lies in generating and transmitting sensory data. The number of sensors and their applications in automotive vehicles has grown drastically in the last decade, a trend that seems to continue still. Wireless self-powered sensors can facilitate current sensor systems by removing the need for cabling and may enable additional applications. These systems have the potential to provide new avenues of optimization in safety and performance.This thesis delves into the topic of vibrations as ambient energy source, primarily for sensors in automotive vehicles. The transduction of small amounts of vibrational, or kinetic, energy to electrical power, also known as vibrational energy harvesting, is an extensive field of research with a plethora of inventions. A short review is given for energy harvesters, in an automotive context, utilizing transduction through either the piezoelectric effect or magnetic induction. Two practical examples, for ambient vibration harvesting in vehicles, are described in more detail. The first is a piezoelectric beam for powering a strain sensor on the engines rotating flexplate. It makes combined use of centrifugal force, gravitational pull and random vibrations to enhance performance and reduce required system size. The simulated power output is 370 \ub5W at a rotation frequency of 10.5 Hz, with a bandwidth of 2.44 Hz. The second example is an energy harvesting unit placed on a belt buckle. It implements magnetic induction by the novel concept of a spring balance air gap of a magnetic circuit, to efficiently harvest minute vibrations. Simulations show the potential to achieve 52 \ub5W under normal road conditions driving at 70 km/h. Theoretical modeling of these systems is also addressed. Fundamental descriptions of the lumped and distributed models are given. Based on the lumped models of the piezoelectric energy harvester (PEH) and the electromagnetic energy harvester (EMEH), a unified model is described and analyzed. New insights are gained regarding the pros and cons of the two types of energy harvester run at either resonance or anti-resonance. A numerical solution is given for the exact boundary of dimensionless quality factor and dimensionless intrinsic resistance, at which the system begins to exhibit anti-resonance. Regarding the maximum achievable power, the typical PEH is favored when running the system in anti-resonance and the typical EMEH is favored at resonance. The described modeling considers all parameters of the lumped model and thus provides a useful tool for developing vibrational energy harvester prototypes

Passive Full-Wave MOSFET Rectifiers for Electromagnetic Harvesting

A new generation of electronic devices has emerged requiring micro-watt-level power supply to operate. Thanks to micro-power processors and sensors, micro-power sources have become an attractive option for industry and research. This work is interested in micro-power sources that harvest vibrational energy by deploying electrostatic, electromagnetic, and piezoelectric transduction techniques. The output power of vibrational energy harvesters is in AC form, whereas electronic loads require known DC power supply to operate. Thus, there is a need for AC-DC conversion between harvesters and electronic loads to get DC power out of AC. Traditional full-wave bridge rectifiers and center-tapped transformer rectifiers are not feasible in micro-watt-level harvesters. Low output power undermines the power efficiency of those traditional rectifiers. Thus, novel, low power, high efficiency conversion circuits are required instead of traditional rectifiers. This goal is particularly challenging when it comes to electromagnetic energy harvesters since their output voltage is much lower than that of electrostatic and piezoelectric harvesters. In this work, we studied four different full-wave rectifiers; a silicon diode bridge rectifier, a Schottky diode bridge rectifier, a passive MOSFET rectifier, an an active MOSFET rectifier. Out of simulation results, we found the voltage and power efficiency of each rectifier. We found that MOSFET-type rectifiers are better than diode type rectifiers in terms of voltage and power efficiency. Both full-wave MOSFET rectifiers have about 99% voltage and power efficiency. There is only a small difference in power and voltage efficiency between the two MOSFET rectifier types below 600mV input voltage amplitude. Since active MOSFET rectifier has extra components and need of external DC supply to power its active devices, we concluded it was not good option for small scale harvester systems. We implemented the passive MOSFET rectifier, tested its performance in rectifying the output of an electromagnetic harvester, and analyzed its effects on the harvester performance. When we connected the MOSFET rectifier to the harvester it doubled the optimum load resistance from 24 Ohm to 48 Ohm. We also studied the rectifier effect on harvester's natural frequency, and it does not change much the natural frequency which means our rectifier acts like resistance, and we also calculated the power efficiency based on harvester test and we have maximum 74% power efficiency

SUSTAINABLE ENERGY HARVESTING TECHNOLOGIES – PAST, PRESENT AND FUTURE

Chapter 8: Energy Harvesting Technologies: Thick-Film Piezoelectric Microgenerato

Semi-Passive Control Strategy using Piezoceramic Patches in Non Linear Commutation Architecture for Structural-Acoustic Smart Systems

The demands for novel smart damping materials can be summarized in: external power source not required for operation; device not needing to be tuned to a specific frequency; device operation not affected by changes in modal frequency; device suppressing vibration over a number of modes, weight and size minimized; self-contained unit device. This thesis focuses on these points and it shows that the dilemma between active and passive vibration control may be solved with a new approach, implementing a semipassive technique without penalties in terms of robustness and performance. Connecting a shunt circuit to a piezoelectric transducer leads to a simple and low cost vibration controller that is able to efficiently suppress unwanted structural vibrations: this is a way to fulfil the abovementioned demands. The objective of this work is to develop and validate by an experimental campaign a computational tool integrated with finite element Nastran software. An original 4-channel switched shunt control system has been realized using a tachometer device. The control system has been tested first of all on a simple cantilevered beam attaining a max vibrations reduction of 16.2 dB for the first bending mode. Further reference test article consisted of a 10 ply fibreglass laminate plate. A multimodal control has applied within a band range of 700Hz including the first seven modes. A maximum reduction of 16 dB has been found. Further numerical and experimental tests have been planned to extend the ability of the SSC to produce structural-borne sound reduction in acoustic rigid cavities for fluid-structure interaction problems. Numerical sound power radiation of an aluminium plate, controlled by synchronized switch system, compared with the experimental acoustic energy detected in acoustic room, has been planned in the ongoing activities

Urubu: energy scavenging in wireless sensor networks

For the past years wireless sensor networks (WSNs) have been coined as one of the most promising technologies for supporting a wide range of applications. However, outside the research community, few are the people who know what they are and what they can offer. Even fewer are the ones that have seen these networks used in real world applications. The main obstacle for the proliferation of these networks is energy, or the lack of it. Even though renewable energy sources are always present in the networks environment, designing devices that can efficiently scavenge that energy in order to sustain the operation of these networks is still an open challenge. Energy scavenging, along with energy efficiency and energy conservation, are the current available means to sustain the operation of these networks, and can all be framed within the broader concept of “Energetic Sustainability”. A comprehensive study of the several issues related to the energetic sustainability of WSNs is presented in this thesis, with a special focus in today’s applicable energy harvesting techniques and devices, and in the energy consumption of commercially available WSN hardware platforms. This work allows the understanding of the different energy concepts involving WSNs and the evaluation of the presented energy harvesting techniques for sustaining wireless sensor nodes. This survey is supported by a novel experimental analysis of the energy consumption of the most widespread commercially available WSN hardware platforms.Há já alguns anos que as redes de sensores sem fios (do Inglês Wireless Sensor Networks - WSNs) têm sido apontadas como uma das mais promissoras tecnologias de suporte a uma vasta gama de aplicações. No entanto, fora da comunidade científica, poucas são as pessoas que sabem o que elas são e o que têm para oferecer. Ainda menos são aquelas que já viram a sua utilização em aplicações do dia-a-dia. O principal obstáculo para a proliferação destas redes é a energia, ou a falta dela. Apesar da existência de fontes de energia renováveis no local de operação destas redes, continua a ser um desafio construir dispositivos capazes de aproveitar eficientemente essa energia para suportar a operação permanente das mesmas. A colheita de energia juntamente com a eficiência energética e a conservação de energia, são os meios disponíveis actualmente que permitem a operação permanente destas redes e podem ser todos englobados no conceito mais amplo de “Sustentabilidade Energética”. Esta tese apresenta um estudo extensivo das várias questões relacionadas com a sustentabilidade energética das redes de sensores sem fios, com especial foco nas tecnologias e dispositivos explorados actualmente na colheita de energia e no consumo energético de algumas plataformas comercias de redes de sensores sem fios. Este trabalho permite compreender os diferentes conceitos energéticos relacionados com as redes de sensores sem fios e avaliar a capacidade das tecnologias apresentadas em suportar a operação permanente das redes sem fios. Este estudo é suportado por uma inovadora análise experimental do consumo energético de algumas das mais difundidas plataformas comerciais de redes de sensores sem fios