193 research outputs found

    Functional modelling and prototyping of electronic integrated kinetic energy harvesters

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    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

    Piezoelectric Energy Harvesting Suspension System for a Half Car Model: Analytical and Experimental Study

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    One of the essential techniques for energy harvesting is the clean energy collection from ambient vibration. Recently, piezoelectric energy harvesting systems became a hot topic and attracted many researchers. This is due to their simple structure, relatively high output power among the other mechanisms (electromagnetic and electrostatic), compatibility with MEMS, and operation in a wide frequency range. The main objective of the current work is to develop a mathematical model to evaluate the potential of harvesting power from the car suspension system. Quarter and half car models with a built-in piezoelectric stack were modeled mathematically using Laplace transformation and simulated using MATLAB/Simulink. The piezoelectric stack was installed in series with the suspension spring to maintain the performance of the original suspension system in ride quality and comfortability. The harvested voltage and power were tested in both time and frequency domain approaches. The results from a quarter car model showed that, the maximum generated voltage and power under harmonic excitation with an acceleration amplitude of 0.5 g and frequency of 1.46 Hz were 19.11 V and 36.74 mW, respectively. By comparing the quarter car model with a half car model, the results illustrated that the output voltage and power of the half car models were increased to 33.56 V and 56.35 mW (75.6% and 53.4%), respectively. Furthermore, the quarter and half car models were subjected to random excitation and tested under three different road classes (A, C, and H). The findings confirmed that the harvested voltage and power were increased with the road roughness levels and car velocity. From very smooth to very rough road levels, the harvested power was increased by 434 mW for quarter car model and 537 mW for half car model. The influence of the different parameters of the piezoelectric stack (number of stack layers and area to thickness) and car suspension (sprung and unsprung stiffness, damping coefficients, and masses) were examined for half car model subjected to harmonic excitation. Also, the effect of road amplitude unevenness was considered. The analytical results of the quarter car model were verified with the experimental test under harmonic excitation. The results exhibited good agreement with the analytical results at different excitation frequencies (0 – 25 Hz). A significant contribution of this work is developing a half car model with a built-in piezoelectric stack. The findings of this work illustrated that there is a significant potential for harvesting energy from the car suspension system. This energy could be utilized in different ways. The study will encourage automobile manufacturers to develop and produce cars that are equipped with multiple energy harvesters to make the dissipated energy available for utilization. Such utilization of regenerated energy improves the fuel efficiency and the economy significantly

    Robust energy harvesting from walking vibrations by means of nonlinear cantilever beams

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    In the present work we examine how mechanical nonlinearity can be appropriately utilized to achieve strong robustness of performance in an energy harvesting setting. More specifically, for energy harvesting applications, a great challenge is the uncertain character of the excitation. The combination of this uncertainty with the narrow range of good performance for linear oscillators creates the need for more robust designs that adapt to a wider range of excitation signals. A typical application of this kind is energy harvesting from walking vibrations. Depending on the particular characteristics of the person that walks as well as on the pace of walking, the excitation signal obtains completely different forms. In the present work we study a nonlinear spring mechanism that is composed of a cantilever wrapping around a curved surface as it deflects. While for the free cantilever, the force acting on the free tip depends linearly on the tip displacement, the utilization of a contact surface with the appropriate distribution of curvature leads to essentially nonlinear dependence between the tip displacement and the acting force. The studied nonlinear mechanism has favorable mechanical properties such as low frictional losses, minimal moving parts, and a rugged design that can withstand excessive loads. Through numerical simulations we illustrate that by utilizing this essentially nonlinear element in a 2 degrees-of-freedom (DOF) system, we obtain strongly nonlinear energy transfers between the modes of the system. We illustrate that this nonlinear behavior is associated with strong robustness over three radically different excitation signals that correspond to different walking paces. To validate the strong robustness properties of the 2DOF nonlinear system, we perform a direct parameter optimization for 1DOF and 2DOF linear systems as well as for a class of 1DOF and 2DOF systems with nonlinear springs similar to that of the cubic spring that are physically realized by the cantilever–surface mechanism. The optimization results show that the 2DOF nonlinear system presents the best average performance when the excitation signals have three possible forms. Moreover, we observe that while for the linear systems the optimal performance is obtained for small values of the electromagnetic damping, for the 2DOF nonlinear system optimal performance is achieved for large values of damping. This feature is of particular importance for the system׳s robustness to parasitic damping.Massachusetts Institute of Technology. Naval Engineering Education Center. (Grant 3002883706)National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374)MIT Energy Initiativ

    Available Technologies and Commercial Devices to Harvest Energy by Human Trampling in Smart Flooring Systems: a Review

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    Technological innovation has increased the global demand for electrical power and energy. Accordingly, energy harvesting has become a research area of primary interest for the scientific community and companies because it constitutes a sustainable way to collect energy from various sources. In particular, kinetic energy generated from human walking or vehicle movements on smart energy floors represents a promising research topic. This paper aims to analyze the state-of-art of smart energy harvesting floors to determine the best solution to feed a lighting system and charging columns. In particular, the fundamentals of the main harvesting mechanisms applicable in this field (i.e., piezoelectric, electromagnetic, triboelectric, and relative hybrids) are discussed. Moreover, an overview of scientific works related to energy harvesting floors is presented, focusing on the architectures of the developed tiles, the transduction mechanism, and the output performances. Finally, a survey of the commercial energy harvesting floors proposed by companies and startups is reported. From the carried-out analysis, we concluded that the piezoelectric transduction mechanism represents the optimal solution for designing smart energy floors, given their compactness, high efficiency, and absence of moving parts

    Small-Scale Energy Harvesting from Environment by Triboelectric Nanogenerators

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    The increasing needs to power trillions of sensors and devices for the Internet of Things require effective technology to harvest small-scale energy from renewable natural resources. As a new energy technology, triboelectric nanogenerators (TENGs) can harvest ambient mechanical energy and convert it into electricity for powering small electronic devices continuously. In this chapter, the fundamental working mechanism and fundamental modes of a TENG will be presented. It can harvest all kinds of mechanical energy, especially at low frequencies, such as human motion, walking, vibration, mechanical triggering, rotating tire, wind, moving automobile, flowing water, rain drops, ocean waves, and so on. Such variety of energy harvesting methods promises TENG as a new approach for small-scale energy harvesting

    Energy harvesting from human and machine motion for wireless electronic devices

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    PIEZO BASED ELECTRIC POWER GENERATION USING 3- DIMENSIONAL MECHANICAL VIBRATIONS PRODUCED IN VEHICLES

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    Due to advancement in the field of technology in recent years, wireless data transmission techniques are commonly used in electronic devices. For powering them we rely upon power supply through wires charging, else power may be supplied from batteries. But while travelling for longer distances continuously we may not be able to obtain power supply for these devices to operate or to recharge their batteries. So in order to operate them continuously we need a power source that provides continuous energy to operate these devices. The mechanical vibrations which are produced by the automobiles can be utilized as a source of energy for generating electrical energy that can be utilized by these electronic equipment to operate. These vibrations are produced by different vehicles around us which is going as a waste. This technique utilizes piezoelectric components where deformations produced by vibrations are directly converted to electrical charge via piezoelectric effect and principle of electromagnetic induction between coil and magnetic field which produces Electromotive force in the coil provided displacement to magnet by the vibrations. The piezoelectric materials and permanent magnets are used as energy conversion devices for converting mechanical vibrations to electrical energy. In this context, we introduced two methods and considered its output performance provided input vibrations, by using piezoelectric materials such as PZT for electro mechanical conversion using Mass-spring system as medium of conversion of force from vibrations applied on PZT materials and by using spring-magnet system where relative displacement of magnet with respect to coil, provided input vibrations generates Electromotive force in coil

    Design and Realization of a Nonlinear Vibration Energy Harvester for Cost Effective Additive Manufacturing

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    Environmental energy harvesting has always been an attractive solution to the search for sustainable energy sources. Combined with the miniaturization and power consumption reduction of sensors and portable electronic devices, the possibility of powering using environmental energy, like vibration energy, instead of conventional batteries increases exponentially. Vibrational energy harvesting can be achieved using devices based on different physical phenomena. Electromagnetic based devices seem to be among the most effective when considering the power output levels within low frequency applications. However, these devices have always had inherent challenges including size and manufacturing cost reduction as well as limitations on the range of effective harvesting frequencies. The purpose of this thesis is to improve the design and manufacturing of an existing electromagnetic energy harvester, while maintaining comparable output power and range of effective harvesting frequency of the new harvester. The improved harvester is designed to maintain functionality based on nonlinear dynamics of an impact oscillator, which increases the effective range of harvesting frequency. This harvester is also designed to be manufactured using additive manufacturing techniques, which reduces the manufacturing cost and time significantly. To achieve this purpose, the design of a fully metallic vibration energy harvester made by a partner group in the University of Waterloo was used as the starting point. The new harvester was redesigned for manufacturing using 3D printing technology as the rapid prototyping manufacturing process. This technology was implemented using the most cost effective material and equipment possible. Three consecutive iterations of the new harvester were produced including multiple versions of each iteration. These iterations presented the gradual improvement in design and manufacturing of the new harvester to overcome technical challenges while maintaining comparable performance levels. Iteration 1 was the baseline, process verification iteration, which included replacing the base of the original harvester with a redesigned and 3D printed base. In the second iteration the mechanism used to obtain the linear displacement of the seismic mass with respect to a fixed structure of the harvester was redesigned and 3D printed. The final iteration produced a fully 3D printed electromagnetic energy harvester for the first time. This new harvester was founded on the same displacement and generation nonlinear dynamic principles as the original metallic harvester with improvements in the design and material of the structure, as well as the selected components and mass of the harvester. In spite of all the manufacturing challenges, iteration number 1 achieved a maximum output voltage of 138mV using a 76g metallic seismic mass, which was considered as the baseline for performance measurements. The price of the harvester base was reduced from 111.26consideringametallicbaseto111.26 considering a metallic base to 28.16 with a 3D printed base. Iteration number 2 achieved a 78% output voltage compared to iteration number 1 with a cost reduction of 18.84%. Iteration number 3 achieved almost 50% maximum output voltage compared to iteration number 1 with a cost reduction of around 73% but remarkably with a seismic mass reduction of 65%. The consecutive reductions of mass and cost of the springless vibration energy harvester with less proportional reduction in produced energy brings closer the possibility of further implementation of energy harvesters in daily applications including consumer products and education applications. The reduction in output voltage is linked to the type and quality of material used in 3D printing causing higher friction rates beside the reduction in 6 seismic mass. Understanding these factors opens many possibilities for future work to improve the output of 3D printed magnetic-based energy harvesters even farther
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