No description available.

No description available.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 247-258). Also available via the Internet.

As micro-electromechanical systems (MEMS) and smart technologies have been more matured, applications for wider fields are more available. Piezoelectric materials have the property of electromechanical energy conversion, which can convert vibration energy into electrical energy. In this paper, a general concept of the piezoelectric energy conversion is first given. Then, a simple modeling design and analysis for a special transverse mode of the piezoelectric generator called mode 31 is presented. With regard to analytical method, the piezoelectric equivalent circuit model is able to illustrate the important parameters that influence the process how the piezoelectric element generates electrical energy. We may adjust unimorph voltage by controlling the deflection of cantilever beam. And the output power is taken as the indicated parameters for the generator. The energy conversion efficiency of the generator depends on the operation frequency. By using this way, the piezoelectric power generator may be widely applied to environment with both low-frequency and high-frequency vibration range.

Mechanical energy exists all over the place in our living, and vibration is the most common way of mechanical performance. Micro-electromechanical systems, the application which integrate techniques and combine different field of research, make it possible to convert vibration into electrical energy by using piezoelectric materials; moreover, it become a small piezoelectric power generator. The thesis set up an equivalent circuit model based on the principle of piezoelectric and cantilever mechanics for experimenting the model¡¦s exactness; consequently, model shows that resonant frequency has no effect on generate electricity when amplitude was fixed. The thesis attempts to change the shape of unimorph for enhancing its power generation. By using different sharp of unimorph, the experiment demonstrate that power generation have direct ratio with frequency at amplitude of 5mm. Moreover, different shapes of the unimorph at frequency of 16Hz have different power output; the disparity among power output might up to 1.78 times.

Environmental challenges, such as global warming, growing demand on energy, and diminishing oil sources have accelerated research on alternative energy conversion methods. Thermoelectric power generation is a promising method to convert wasted heat energy into useful electrical energy form. A temperature gradient imposed on a thermoelectric device produces a Seebeck potential. However, this temperature gradient causes thermal stresses due to differential thermal expansions and mismatching of the bonded components of the device. Thermal stresses are critical for thermoelectric devices since they can generate failures, including dislocations, cracks, fatigue fractures, and even breakdown of the entire device. Decreases in power-generation performance and operation lifetime are major consequences of these failures. In order to minimize thermal stresses in the legs without affecting power-generation capabilities, this study concentrates on structural solutions. Thermoelectric devices with non-segmented and segmented legs were modeled. Specifically, the possible effect of various leg geometries, configurations, and dimensions were evaluated using finite-element and statistical methods. Significant changes in the magnitudes and distributions of thermal stresses occurred. Specifically, the maximum equivalent stresses in the rectangular-prism and cylindrical legs were 49.9 MPa and 43.3 MPa, respectively for the temperature gradient of 100ºC. By using cylindrical legs with modified dimensions, decreases in the maximum stresses in legs reached 21.2% without affecting power-generation performance. Moreover, the effect of leg dimensions and coaxial-leg configurations on power generation was significant; in contrast, various leg geometries and rotated-leg configurations had very limited affect. In particular, it was possible to increase power output from 20 mW to 65 mW by simply modifying leg widths and heights within the defined range. It should be noted, however, this modification also increased stress levels. It is concluded that leg geometries, configurations, and dimensions can be redesigned for improved durability and overall performance of thermoelectric devices.

Submitted by Joana Azevedo (joanad@id.uff.br) on 2017-07-03T12:52:37Z No. of bitstreams: 1 Dissert CEZAR AUGUSTO CECHIN.pdf: 2893279 bytes, checksum: 6041ec6c989e858605c656ff1fe6baab (MD5) / Approved for entry into archive by Biblioteca da Escola de Engenharia (bee@ndc.uff.br) on 2017-07-06T16:47:06Z (GMT) No. of bitstreams: 1 Dissert CEZAR AUGUSTO CECHIN.pdf: 2893279 bytes, checksum: 6041ec6c989e858605c656ff1fe6baab (MD5) / Made available in DSpace on 2017-07-06T16:47:06Z (GMT). No. of bitstreams: 1 Dissert CEZAR AUGUSTO CECHIN.pdf: 2893279 bytes, checksum: 6041ec6c989e858605c656ff1fe6baab (MD5) Previous issue date: 2016-06-20 / Esta pesquisa apresenta como objetivo geral analisar o controle de ruído nos geradores de energia em uma balsa guindaste, através da utilização de materiais de atenuação, intervenção na vibração dos equipamentos e na introdução de acessórios e componentes de máquinas, ventiladores e exaustores. Para o desenvolvimento da pesquisa foi escolhida um dos ambientes de trabalho mais ruidosos da balsa guindaste, construída na década de 70, pertencente a uma das Empresas que presta apoio na exploração e produção de petróleo na área de Engenharia Submarina e que seu escopo principal é realizar atividades de movimentação de grandes cargas e lançamentos de dutos. Numa avaliação detalhada nas frentes de serviço e dos equipamentos existentes, medições e estudos realizados no período 2013 até 2016, histórico de monitoramento dos ruídos e análise critica dos últimos cinco anos, bem como entrevista verbal com a força de trabalho envolvida, foram selecionados a praça de geradores de energia para estudo de caso e melhorias na atenuação do ruído. Conjuntamente com a implantação das medidas propostas de redução de ruído, foi aplicado o questionário para verificação da eficácia do tratamento realizado e dos fatores de qualidade de vida dos colaboradores. Como resultado final foi sugerido às medidas corretivas e preventivas para tornar o ambiente saudável do ponto de vista da higiene ocupacional, como por exemplo, a instalação de atenuadores de ruído nos ventiladores e exaustores dos geradores de energia, instalação de painéis de lã de rocha com chapas perfuradas em determinados ambientes, bem como inserir forro acústico no teto da sala e paredes da sala de manutenção (SMM), visando diminuir a influencia das fontes geradoras. / The present research intends to analyze the noise control in power generators on a ferry crane, through the use of mitigation materials, intervention in the equipment’s vibration and the introduction of accessories and machine components, ventilation fans and exhaust fans. In order to develop this research it was chosen one of the noisiest barge crane, which was built in the 1970s, owned by one of the companies that provide support in oil exploration and production in the field of Subsea Engineering and its main goal is to perform activities that handle with large loads and pipelines launching. In a detailed evaluation of the service and equipment, measurements and studies of the noise monitoring historical and critical analysis of the past five years were realized during 2013 to 2016, as well as verbal interviews with the workforce involved, selecting some square power generators for case study and improvements in noise attenuation. In conjunction with the implementation of noise reduction measures proposed, it was applied a questionnaire to verify the effectiveness of the treatment and the quality of life of employees factors. As a final result it was suggested to the corrective and preventive measures to turn it into a healthy area from the point of view of occupational hygiene, such as the installation of noise attenuators in ventilation fans and exhaust fans of power generators, installation of rock wool panels with perforated sheets in certain areas, as well as insert acoustic ceiling in the living room and walls of the engine room monitoring, in order to reduce the influence of the generating sources.

Piston telemetry research involves monitoring the temperatures at specific internal location points within a combustion engine piston. The temperatures are detected with type K thermocouples as voltages and processed to convert them into temperatures using cold junction compensation methods. The present system uses a specific sensor designed to operate in the high temperature environment within the piston, reading multiple thermocouples. Because of the reciprocating motion of the piston, power generation is intermittent and available only when the piston reaches near bottom dead centre, using inductive coupling to power the sensors and transmit data to an evaluation unit for data processing. The planned system involves designing and building a prototype telemetry unit using ¿off the shelf¿ components that integrate the reading of thermocouple outputs, signal processing and cold junction compensation. Wireless telemetry is adopted for data transmission with an integrated Bluetooth and microcontroller module. The data acquisition module can be adapted for other sensors by adapting the firmware uploaded to the microcontroller. The hardware electronics are envisaged to be encased in thermal insulation to enable operation in high temperature environments. The considered system requires a power supply for the integrated components in the form of a power generator and that it should meet two criteria: to be located within confined spaces and to be permanently available, without having to dismantle systems to change batteries. The selected method is an induction generator constructed from a coil stator connected to the piston connection rod big end and a permanent magnet rotor connected to the crankshaft. The suggested mechatronic system is validated against the present system by comparing both systems to determine whether wireless telemetry can perform within acceptable tolerances and limits for the specified task. Then, for acceptable performances, reduce costs and include flexibility to operate in multiple environments. Bench testing shows that the power generator is capable of driving the sensors and the Bluetooth integrated DAQ system. / EPSRC and University of Bradford

This thesis study presents the design, simulation, micro fabrication, and testing steps of microelectromechanical systems (MEMS) based electromagnetic micro power generators. These generators are capable of generating power using already available environmental vibrations, by implementing the electromagnetic induction technique. There are mainly two objectives of the study: (i) to increase the bandwidth of the traditional micro generators and (ii) to improve their efficiency at low frequency environmental vibrations of 1-100 Hz where most vibrations exist. Four main types of generators have been proposed within the scope of this thesis study. The first type of generator is mainly composed of 20 parylene cantilevers on which coils are fabricated, where the cantilevers are capable of resonating with external vibrations with respect to a stationary magnet. This generator has dimensions of 9.5&times / 8&times / 6 mm3, and it has been shown that 0.67 mV of voltage and 56 pW of power output can be obtained from a single cantilever of this design at a vibration frequency of 3.45 kHz. The second type generator aims to increase the bandwidth of the traditional designs by implementing cantilevers with varying length. This generator is sized 14&times / 12.5&times / 8 mm3, and the mechanical design and energy generation concept is similar to the first design. The test results show that by using 40 cantilevers with a length increment of 3 &amp / #956 / m, the overall bandwidth of the generator can be increased to 1000 Hz. It has also been shown that 9 mV of constant voltage and 1.7 nW of constant power output can be obtained from the overall device in a vibration frequency range of 3.5 to 4.5 kHz. The third type is a standard large mass coil type generator that has been widely used in the literature. In this case, the generator is composed of a stationary base with a coil and a magnet-diaphragm assembly capable of resonating with vibrations. The fabricated device has dimensions of 8.5&times / 7&times / 2.5 mm3, and it has been considered in this study for benchmarking purposes only. The test results show that 0.3 mV of voltage and 40 pW of power output can be obtained from the fabricated design at a vibration frequency of 113 Hz. The final design aims to mechanically up-convert low frequency environmental vibrations of 1-100 Hz to a much higher frequency range of 2-3 kHz. This type of generator has been implemented for the first time in the literature. The generator is composed of two parts / a diaphragm-magnet assembly on the top, and 20 cantilevers that have coils connected in series at the base. The diaphragm oscillates by low frequency environmental vibrations, and catches and releases the cantilevers from the tip points where magnetic nickel (Ni) areas are deposited. The released cantilevers then start decaying out oscillations that is at their damped natural frequency of 2-3 kHz. It has been shown with tests that frequency up-conversion is realized in micro scale. The fabricated device has dimensions of 8.5&times / 7&times / 2.5 mm3, and a maximum voltage and power output of 0.57 mV and 0.25 nW can be obtained, respectively, from a single cantilever of the fabricated prototype at a vibration frequency of 113 Hz.

This thesis study presents the design, simulation, and fabrication of a low frequency electromagnetic micro power generator. This power generator can effectively harvest energy from low frequency external vibrations (1-100 Hz). The main objective of the study is to increase the efficiency of the previously proposed structure in METU-MEMS Center, which uses the frequency up-conversion technique to harvest energy from low frequency vibration. The proposed structure has been demonstrated by constructing several macro scale prototypes. In one of the constucted prototypes, the diaphragms are connected to a fixed frame via metal springs. The upper diaphragm having lower resonance frequency carries a magnet, and the lower diaphragm carries a hand wound coil and a magnetic piece for converting 6 Hz external vibrations up to 85 Hz, resulting a maximum voltage and power levels of 11.1 mV and 5.1 &micro / W, respectively. In an improved prototype, the metal springs are replaced with rubber ones, providing higher energy conversion efficiency and flexibility to tune the resonance frequency of both diaphragms to desired values. This prototype provides 104 &micro / W maximum power and 37.7 mV maximum voltage in response to vibration levels of 30 Hz. The proposed structure is also suitable to be realized by using microfabrication techniques. Hence, the structure to be microfabricated is studied and optimized for this purpose. When scaled to microelectromechanical dimensions, the expected maximum power and voltage from the 10 x 8.5 x 2.5 mm3 generator is 119 nW and 15.2 mV, respectively. A microfabrication process has also been designed for the proposed generator structure. According to this process, the structure consists of a stack of two pieces, each carrying different diaphragms. The diaphragms are made of parylene, and the coil and the magnetic piece are electroplated copper and nickel, respectively. As a result of this study, a new topology is proposed for harvesting energy at low frequency vibrations by the frequency up-conversion technique, and an efficiency improvement is expected with more than three orders of magnitude (119 nanoWatts output for the same size) compared to the study realized in our laboratory in converting low frequency (70-150 Hz) environmental vibrations to electrical energy.