293 results found
Qin Y, Boyle D, Yeatman E, 2019, Efficient and reliable aerial communication with wireless sensors, IEEE Internet of Things Journal, Vol: 6, Pages: 9000-9011, ISSN: 2327-4662
This paper describes the design, implementation andevaluation of a first of its kind cross-layer protocol for wirelesscommunication between flying agents and terrestrial wireless sensors. The protocol is composed of three layers: a new applicationlayer built upon a modified implementation of ContikiMAC overthe IEEE 802.15.4 2.4 GHz physical layer. The experimental evaluation shows the protocol to have excellent energy efficiency,low latency and high reliability—approaching 100% for certainparameter settings and operational conditions. The effects ofspeed, altitude, and direction of approach are also experimentallyevaluated, demonstrating that it is of critical importance to takethese into account when planning mobile aerial data collectioncampaigns.
Fu H, Yeatman E, 2019, Rotational energy harvesting using bi-stability and frequency up-conversion for low-power sensing applications: Theoretical modelling and experimental validation., Mechanical Systems and Signal Processing, Vol: 125, Pages: 229-244, ISSN: 0888-3270
Abstract Kinetic energy harvesting has drawn great attention in the past decade, but low-frequency and broadband operation is still a big issue which impedes this technology to be widely deployed in low-power Internet of Things applications. In this paper, theoretical modelling and experimental validation of a rotational harvester with bi-stability and frequency up-conversion is presented for harnessing low-frequency kinetic energy with a wide bandwidth. Piezoelectric transduction was adopted to convert the rotational kinetic energy into electricity. Distributed-parameter modelling was employed for analyzing the electromechanical dynamics of the bistable piezoelectric beam. Bistable and frequency up-converting behaviours were considered in the theoretical model by introducing two external input magnetic forces. Different oscillating modes were analyzed, showing the variation of power generation capability under different modes, and the advantage of operating in the periodic double-well mode. From the potential well study, we got a conclusion that for the same input magnetic force, periodic double-well mode is capable of achieving a larger vibration amplitude compared to a harvester without bi-stability. Asymmetric potential well shapes were investigated. This asymmetric shape provides a way to stabilize the initiation position of the beam for each plucking cycle, and eventually to stabilized the output. Key design factors to control the oscillating modes were studied, providing a guideline for future design. An experimental study was conducted to verify the theoretical results. A close match was achieved. This bistable harvester demonstrated a significant improvement (up to 2 × ) compared to a harvester without bi-stability over a wide bandwidth (from 1 to 11 Hz) at low frequencies, when operating in the periodic double-well mode. This paper presents a detailed theoretical model and in-depth analysis of a bistable frequency up-converting harvester, providing a
Wright S, Kiziroglou M, Spasic S, et al., 2019, Inductive energy harvesting from current-carrying structures, IEEE Sensors Letters, Vol: 3, ISSN: 2475-1472
This article introduces an inductive method for harvesting energy from current-carrying structures. Numerical simulation of a structural beam shows that the skin effect can lead to significant current concentration at edges, providing a five-fold power benefit at such locations, even at frequencies below 1 kHz. The use of a rectangular ferrite core can provide a ×4 power density improvement. The adoption of funnel-like core shapes allows the reduction of core mass and coil frame size, leading to significant further power density enhancement. Magnetic field simulation and coil analysis demonstrate a power density increase of ×49 by ferrite funnels, in comparison to a coreless coil. Experimental results demonstrate rectified power over 1 mW delivered to a storage capacitor, from a 40 × 20 × 2 mm core-and-coil, in the vicinity of a spatially distributed 20 A current at 800 Hz. Rectification and impedance matching are studied experimentally using a voltage doubler circuit with input capacitor tuning to counteract the coil reactance. Experimental results from a spatially distributed 30 A current at 300 Hz and a 1:7 funnel core demonstrate power density of 36 μ W/g (103 μ W/cm 3 ), opening up the way to noninvasive inductive powering of systems in the vicinity of current-carrying structures.
Fu H, Zhou S, Yeatman E, 2019, Exploring coupled electromechanical non-linearities for broadband energy harvesting from low-frequency rotational sources, Smart Materials and Structures, Vol: 28, ISSN: 0964-1726
This paper presents a methodology to effectively harness low-frequency broadband rotational energy using coupled electromechanical non-linearities. This design integrates bi-stability and a synchronized switch harvesting on inductor (SSHI) circuit into a frequency up-converting harvester. The bistable behaviour enables improved output power due to the increased vibration amplitude under the same input plucking force. The SSHI circuit exhibits enhanced conversion capability, contributing higher electrical damping which is ideal for frequency up-converting harvesters to alleviate output fluctuation at high frequencies. To study the coupled non-linear dynamics from both the mechanical (bi-stability) and electrical (SSHI) sides, a system-level theoretical model is, for the first time, established and numerically solved using Matlab/Simulink. System behaviours, which would not be able to obtain using circuit simulation methods, are studied for different operating frequencies and load resistances. To validate the theoretical analysis, this harvester was implemented and tested experimentally. A close match was obtained. From the experimental results, an enhanced output power (up to 525%), over a broad frequency range, was realized, compared to that of a harvester with neither bi-stability nor SSHI circuits.
Gramling HM, Towle CM, Desai SB, et al., 2019, Spatially Precise Transfer of Patterned Monolayer WS2 and MoS2 with Features Larger than 10(4) mu m(2) Directly from Multilayer Sources, ACS APPLIED ELECTRONIC MATERIALS, Vol: 1, Pages: 407-416, ISSN: 2637-6113
Qin Y, Boyle D, Yeatman E, 2019, Radio Diversity for Heterogeneous Communication with Wireless Sensors, 5th IEEE World Forum on Internet of Things (IEEE WF-IoT), Publisher: IEEE, Pages: 955-960
Fu H, Yeatman E, 2018, Comparison and scaling effects of rotational micro‐generators using electromagnetic and piezoelectric transduction, Energy Technology, Vol: 6, ISSN: 2194-4296
Rotational energy is widely distributed or easily acquirable from other energy sources (fluid flow, machine operation or human motion) in many industrial and domestic scenarios. At small scales, power generation from such rotational ambient sources can enable many autonomous and self‐reliant sensing applications. In this paper, three typical types of micro‐generators (energy harvesters), namely electromagnetic (EMREHs), piezoelectric resonant (PRREHs) and piezoelectric non‐resonant rotational energy harvesters (PNRREHs) are discussed and compared in terms of device dimensions and operation frequencies. Theoretical models are established for each type to calculate maximum achievable output power as a function of device dimension and operating frequency. Using these theoretical models, scaling laws are established for each type to estimate the achievable output. The EMREHs have a strong scaling effect both on device dimension (as L5) and on operating frequency (as ω2), whereas the PNRREHs are less so (L2.5ω0.5). PRREHs have a narrow band‐width as resonant harvesters, and are ideal for cases where the excitation frequency is constant. This study provides a guideline for selection and design of rotational energy harvesters (REHs) when the device dimension and operating frequency are defined. The proposed scaling laws offer a convenient method to estimate the harvester performance for different dimensions and operating frequencies.
Kiziroglou M, Wright S, Shi M, et al., Milliwatt power supply by dynamic thermoelectric harvesting, PowerMEMS 2018, Publisher: Institute of Physics (IoP), ISSN: 1742-6588
In this work we demonstrate a power supply that collects thermal energy from temperature fluctuations in time, to provide regulated power in the milliwatt range. It is based on the dynamic thermoelectric energy harvesting concept, in which a phase change material is used to store heat and create spatial heat flow from temperature transients. A simple, cost-effective and reproducible fabrication method is employed, based on 3D printing and off-the-shelf components. The harvester is integrated with a commercial power management module and supercapacitor storage. Output energy up to 2 J is demonstrated from temperature cycles corresponding to avionic applications. The demonstration includes harvesting while powering a 10 kΩ analogue voltmeter directly from the supercapacitor, including during cold-starting.
Fu H, Yeatman EM, Fu H, et al., 2018, Effective piezoelectric energy harvesting using beam plucking and a synchronized switch harvesting circuit, Smart Materials and Structures, Vol: 27, ISSN: 0964-1726
Piezoelectric energy harvesting, as a way to convert kinetic energy into electricity for low-power electronics, has drawn great attention for the last decade. However, issues still remain, including narrow operating bandwidth and low harvesting capability. In this paper, beam plucking (frequency up-conversion) and a parallel synchronized switch harvesting on inductor (P-SSHI) circuit are integrated in a piezoelectric energy harvester to improve the energy harvesting capability over a wide operating bandwidth. A theoretical model for the plucked beam is established using a distributed-parameter method. In order to study the system dynamics, an equivalent circuit for the plucked beam is built to integrate with the P-SSHI circuit. System dynamics, including the input power, beam tip displacement and output power, are investigated for different driving frequencies and load resistance. The plucked beam provides a uniform and single-frequency vibration for the P-SSHI to generate reliable switching events for any low-frequency wideband vibration; the P-SSHI circuit exhibits an improved electrical damping ratio which is beneficial to alleviating the power fluctuation issue for plucked beams at high frequencies. An experimental validation was conducted, and a close match was obtained. Enhanced output power with low power fluctuation was obtained in the Plucked Beam and P-SSHI circuit (PBPS) configuration over a wide frequency bandwidth with constant load resistance.
Kiziroglou M, Cowell M, Kumaravel BT, et al., 2018, Speed vs efficiency and storage type in portable energy systems, PowerMEMS 2017, Publisher: Institute of Physics (IoP), ISSN: 1742-6588
Portable power management systems must optimise power interfacing, storage androuting, to meet application specific functionality requirements. Two key aspects are reliabilityand efficiency. For reliable operation, it is required that powering on/off the system must occurin a planned manner. For efficient operation, it is desired that the system is powered for anoptimal amount of time. maximizing its useful operational outcome per unit of energy consumed.This can be achieved by optimizing energy usage based on the anticipated energy income andpower demand of duty-cycled power consumers. Both battery and supercapacitor storage can beemployed to meet energy and power density demand, on both sides, and to enable fast transitionfrom cold-starting to active power management. A simplified model is used to calculate thereliability of a simple solar-powered microsystem. The modelling of dynamically configurableinterfacing and storage may enable a new generation of power management, providing reliablepower from irregular and small energy sources.
Mitcheson PD, Kkelis G, Aldhaher S, et al., 2018, Power Electronics for Wireless Power Delivery in Synthetic Sensor Networks, 17th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Shi M, Yeatman E, Holmes AS, et al., 2018, MINIATURE WIND ENERGY HARVESTER BASED ON FLOW-INDUCED VIBRATION
This work demonstrates an experimental study of wideband wind energy harvesting by self-sustained flowinduced vibration. We fabricated a novel folded structure using PET film as a bluffbody, which was directly mountedon a piezoelectric film to generate vibration in wind flow. The lock-in of the flow-induced vibration of the flutter wasobserved in our work. The vibration frequency of this device was locked at 10.8 Hz, which was its natural frequency,across a wide wind speed range from 5.8 m/s to 12.2 m/s. The continuous resonance gives this device stableoutput in this wide range of wind speed. Just using a small piezoelectric PVDF film of 3 cm2, the peak power outputof our device can achieve 3.16 μW and keep at a high level once the self-sustained flow induced vibration occurs.
Yeatman E, 2018, Ellipsometry of sol-gel films, Handbook of Sol-Gel Science and Technology: Processing, Characterization and Applications, Pages: 1595-1605, ISBN: 9783319320991
© Springer International Publishing AG, part of Springer Nature 2018. Ellipsometry is an optical method for determining the properties of thin films, using manipulation and measurement of the polarization state of reflected light. This chapter introduces the method, summarizes the optical principles and analysis involved, and describes the basic experimental arrangements. Applications and limitations of the technique are presented. A specific application, the use of ellipsometry to determine the pore size distribution in thin porous films, is then described in some detail.
Qin Y, Boyle D, Yeatman E, 2018, A Novel Protocol for Data Links between Wireless Sensors and UAV Based Sink Nodes, 4th IEEE World Forum on Internet of Things (WF-IoT), Publisher: IEEE, Pages: 371-376
Mitcheson PD, Boyle D, Kkelis G, et al., 2017, Energy-Autonomous Sensing Systems Using Drones, 16th IEEE SENSORS CONFERENCE, Publisher: IEEE, Pages: 648-650, ISSN: 1930-0395
© 2017 IEEE. This paper describes the system concept and initial results for end-to-end energy-autonomous sensor systems using unmanned aerial vehicles (drones) as agents for power delivery to and data gathering from sensing devices. Such systems may be particularly useful for delay tolerant monitoring scenarios, where sensing devices may be deployed in remote, harsh conditions, often with sparse connectivity, long life and high reliability requirements. This paper discusses the latest advances in wireless power delivery that makes this it possible to fly wireless power delivery systems on drones that have little payload capability.
Yeatman EM, Gramling HM, Wang EN, 2017, Introduction to the special topic on nanomanufacturing, Microsystems and Nanoengineering, Vol: 3, ISSN: 2055-7434
Kiziroglou M, Becker T, Wright SW, et al., 2017, Three-Dimensional Printed Insulation For Dynamic Thermoelectric Harvesters With Encapsulated Phase Change Materials, IEEE Sensors Letters, Vol: 1, ISSN: 2475-1472
Energy harvesting devices have demonstrated their ability to provide power autonomy to wireless sensor networks. However, the adoption of such powering solutions by the industry is challenging due to their reliance on very specific environmental conditions such as vibration at a specific frequency, direct sunlight, or a local temperature difference. Dynamic thermoelectric harvesting has been shown to expand the applicability of thermoelectric generators by creating a local spatial temperature gradient from a temporal temperature fluctuation. Here, a simple method for prototyping or short-run production of such devices is introduced. It is based on the design and 3-D printing of an insulating container, insertion of a phase change material in encapsulated form, and use of commercial thermoelectric generators. The simplicity of this dry assembly method is demonstrated. Two prototype devices with double-wall insulation structures are fabricated, using a stainless-steel and a plastic phase change material encapsulation and a commercial TEG. Performance tests under a temperature cycle between ±25 °C show energy output of 43.6 and 32.1 J from total device masses of 69 and 50 g, respectively. Tests under multiple temperature cycles demonstrate the reliability and performance repeatability of such devices. The proposed method addresses the complication of requiring a wet stage during the final assembly of dynamic thermoelectric harvesters. It allows design and customization to particular size, energy, and insulation geometry requirements. This is important because it makes dynamic harvesting prototyping widely available and easy to reproduce, test, and integrate into systems with various energy requirements and size restrictions.
Gramling HM, Yeatman EM, Taylor HK, 2017, Interlayer cleavage behavior in van der Waals materials, 14th International Conference on Fracture, Pages: 402-403
© 2017 Chinese Society of Theoretical and Applied Mechanics. All Rights Reserved. A computational model is presented of interlayer deformation in van der Waals structures, in order to investigate the fracture mechanisms of these materials. A parameterization scheme equipped to handle large numbers of layers is used. Despite the low energetic cost of slip, a form of plasticity, results show a tendency towards brittle fracture. Allowing bending in layers, to form and propagate a crack, is shown to be an energetically favorable path for relieving strain.
Kiziroglou ME, Becker T, Yeatman EM, et al., 2017, Comparison of methods for static charge energy harvesting on aircraft, SPIE Microtechnologies, Publisher: Society of Photo-optical Instrumentation Engineers (SPIE), ISSN: 1996-756X
In this paper, the possibility of using the static charge that accumulates on aircraft during flight as a source to power monitoring sensors is examined. The assessed methods include using a pair of materials with different air-flow charging rates, contact discharging of the fuselage to neutral metallic bodies, charge motion induction by the fuselage field and inductive harvesting of fuselage-to-air corona discharges at static discharge wicks. The installation and potential advantages of each method are discussed. The feasibility of directly charging a storage capacitor from accumulated static charge is studied experimentally, demonstrating a voltage of 25V on a 25nF capacitor.
Gramling HM, Kiziroglou ME, Yeatman EM, 2017, Nanotechnology for Consumer Electronics, Nanoelectronics: Materials, Devices, Applications, Publisher: Wiley, Pages: 501-526, ISBN: 9783527800728
© 2017 Wiley-VCH Verlag GmbH & Co.KGaA. All rights reserved. Nanotechnology is already inherent in communication modules through the ubiquitous use of low cost, highly functional silicon integrated circuits. Motion processing units, portable biomedical sensors, and imaging sensors are discussed along with relevant nanotechnologies, both current and imminent. Nanotechnology-enhanced glucose sensors are expected in commercial glucose monitoring systems in the next few years. Nevertheless, advances in nanotechnology could soon play a significant role in the evolution of optical sensors for consumer electronics. Nanotechnology is expected to play a significant role in the technology evolution of organic light-emitting diode (OLED) devices. Nanotechnologies are of critical importance to the progress of liquid crystal displays (LCDs), electrophoretic, and electrochromic displays, all of whose operating principles fundamentally rely on nanoscaled structures. Nanotechnology is essential to the continuing advances in integrated electronics: increasing computational power, reducing device scale, and limiting energy consumption.
Fu H, Yeatman EM, 2017, BROADBAND ROTATIONAL ENERGY HARVESTING USING BISTABLE MECHANISM AND FREQUENCY UP-CONVERSION, 30th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), Publisher: IEEE, Pages: 853-856, ISSN: 1084-6999
This paper presents the electromechanical dynamics of a broadband rotational piezoelectric energy harvester using bi-stability and frequency up-conversion. Bi-stability is achieved by the repulsive force between the tip magnet on a piezoelectric cantilever and a fixed magnet above the tip magnet. Frequency up-conversion is realized by the plucking force generated between the tip magnet and a rotating driving magnet below the tip magnet. A numerical model based on the distributed-parameter model was built in Matlab/Simulink. The power extraction capability of different modes of oscillation was analyzed theoretically. The keys to maintain harvester operation in high energy orbit (inter-well vibration) were investigated. The rotational piezoelectric energy harvester was implemented experimentally, showing a significant improvement in output power over a wide bandwidth compared to a harvester without bi-stability.
Fu H, Yeatman EM, 2017, A methodology for low-speed broadband rotational energy harvesting using piezoelectric transduction and frequency up-conversion, Energy, Vol: 125, Pages: 152-161, ISSN: 0360-5442
Energy harvesting from vibration for low-power electronics has been investigated intensively in recent years, but rotational energy harvesting is less investigated and still has some challenges. In this paper, a methodology for low-speed rotational energy harvesting using piezoelectric transduction and frequency up-conversion is analysed. The system consists of a piezoelectric cantilever beam with a tip magnet and a rotating magnet on a revolving host. The angular kinetic energy of the host is transferred to the vibration energy of the piezoelectric beam via magnetic coupling between the magnets. Frequency up-conversion is achieved by magnetic plucking, converting low frequency rotation into high frequency vibration of the piezoelectric beam. A distributed-parameter theoretical model is presented to analyse the electromechanical behaviour of the rotational energy harvester. Different configurations and design parameters were investigated to improve the output power of the device. Experimental studies were conducted to validate the theoretical estimation. The results illustrate that the proposed method is a feasible solution to collecting low-speed rotational energy from ambient hosts, such as vehicle tires, micro-turbines and wristwatches.
Pillatsch P, Xiao BL, Shashoua N, et al., 2017, Degradation of bimorph piezoelectric bending beams in energy harvesting applications, Smart Materials and Structures, Vol: 26, ISSN: 0964-1726
Piezoelectric energy harvesting is an attractive alternative to battery powering for wireless sensor networks. However, in order for it to be a viable long term solution the fatigue life needs to be assessed. Many vibration harvesting devices employ bimorph piezoelectric bending beams as transduction elements to convert mechanical to electrical energy. This paper introduces two degradation studies performed under symmetrical and asymmetrical sinusoidal loading. It is shown that besides a loss in output power, the most dramatic effect of degradation is a shift in resonance frequency which is highly detrimental to resonant harvester designs. In addition, micro-cracking was shown to occur predominantly in piezoelectric layers under tensile stress. This opens the opportunity for increased life time through compressive operation or pre-loading of piezoceramic layers.
Kiziroglou M, Boyle D, Wright S, et al., 2017, Acoustic power delivery to pipeline monitoring wireless sensors, Ultrasonics, Vol: 77, Pages: 54-60, ISSN: 1874-9968
The use of energy harvesting for powering wireless sensors is made more challenging in most applications by the requirement for customization to each specific application environment because of specificities of the available energy form, such as precise location, direction and motion frequency, as well as the temporal variation and unpredictability of the energy source. Wireless power transfer from dedicated sources can overcome these difficulties, and in this work, the use of targeted ultrasonic power transfer as a possible method for remote powering of sensor nodes is investigated. A powering system for pipeline monitoring sensors is described and studied experimentally, with a pair of identical, non6inertial piezoelectric transducers used at the transmitter and receiver. Power transmission of 18 mW (Root6Mean6Square) through 1 m of a 118 mm diameter cast iron pipe, with 8 mm wall thickness is demonstrated. By analysis of the delay between transmission and reception, including reflections from the pipeline edges, a transmission speed of 1000 m/s is observed, corresponding to the phase velocity of the L(0,1) axial and F(1,1) radial modes of the pipe structure. A reduction of power delivery with water6filling is observed, yet over 4 mW of delivered power through a fully6filled pipe is demonstrated. The transmitted power and voltage levels exceed the requirements for efficient power management, including rectification at cold6starting conditions, and for the operation of low6power sensor nodes. The proposed powering technique may allow the implementation of energy autonomous wireless sensor systems for monitoring industrial and network pipeline infrastructure.
Allmen L, Bailleul G, Becker T, et al., 2017, Aircraft strain WSN powered by heat storage harvesting, IEEE Transactions on Industrial Electronics, Vol: 64, Pages: 7284-7292, ISSN: 0278-0046
The combination of ultra-low power wireless communications and energy harvesting enables the realization of autonomous Wireless Sensor Networks.Such networks can be usefully applied in commercialaircraft where wireless sensing solutions contribute to weight reduction and increased ease of installation and maintenance. This paper presents, for the first time, a complete energy autonomous wireless strain monitoring system for aircraft. The system is based on a multi-mode wireless TDMA MAC protocol that supports automatic configuration and a time-stamping accuracy better than 1 ms. The energy supply depends solely on an innovative thermoelectric energy harvester which takes advantage of the changes in environmental temperature during take-off and landing. The system was successfully integrated and passed the functional and flight-clearance tests that qualify it for use in a flight-test installation.
Pervasive sensing - the capability to deploy large numbers of sensors, to link them to communication networks, and to analyze their collective data - is transforming many industries. In mining, networked sensors are already used for remote operation, automation including driverless vehicles, health and safety, and exploration. In this paper, the state-of-the-art sensing and monitoring technologies are assessed as solutions against the main challenges and opportunities in the mining industry. Localization, mapping, remote operation, maintenance and health and safety are identified as the main beneficiaries, from rapidly developing technologies such as 3D visualization, augmented reality, energy autonomous sensor nodes, distributed sensing, smart network protocols and big data analytics. It is shown that the identification and management of ore grade in particular, which transcends each stage of the mining process, may critically benefit from certain arising sensing technologies, where major efficiency improvements are possible in exploration, extraction, haulage and processing activities.
Fu H, Yeatman EM, 2016, Broadband Rotational Energy Harvesting with Non-linear Oscillator and Piezoelectric Transduction, 16th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2016), Publisher: IOP Publishing, ISSN: 1742-6588
Rotational energy is widely distributed in many industrial and domestic applications, such as ventilation systems, moving vehicles and miniature turbines. This paper reports the design and implementation of a bi-stable rotational energy harvester with wide bandwidth and low operating frequency. The rotational energy is converted into electricity by magnetic plucking of a piezoelectric cantilever using a driving magnet mounted on a rotating host. The bistable condition is achieved by introducing a fixed magnet above the tip magnet at the cantilever's free end. The repulsive magnetic force between the magnets creates two equilibrium positions for the piezoelectric beam. The harvester is designed to operate in the high energy orbit (interwell vibration mode) to extract more energy from the rotational energy source. Harvesters with and without bistability are compared experimentally, showing the difference of power extraction on both the output power and bandwidth. The method proposed in this paper provides a simple and efficient way to extract rotational energy from the ambient environment.
Kiziroglou M, Becker T, Wright S, et al., Thermoelectric generator design in dynamic thermoelectricenergy harvesting, PowerMEMS 2016, Publisher: IOP Publishing: Conference Series, ISSN: 1757-899X
This paper reports an analysis of thermoelectric generator design for dynamic thermoelectric harvesting. In such devices, the available energy for a given temperature cycle is finite and determined by the heat storage unit capacity. It is shown by simulation and experimentally that specific thermoelectric generator designs can increase the energy output, by optimizing the balance between heat leakage and dynamic response delay. A 3D printed, double,wall heat storage unit is developed for the experiments. Output energy of 30 J from 7.5 gr of phase change material, from a temperature cycle between ± 22 oC is demonstrated, enough to supply typical duty,cycled wireless sensor platforms. These results may serve as guidelines for the design and fabrication of dynamic thermoelectric harvesters for applications involving environments with moderate temperature fluctuations.
Kang M, Yeatman EM, 2016, Thermal Energy Harvesting Using Pyroelectric and Piezoelectric Effect, 16th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2016), ISSN: 1742-6588
© Published under licence by IOP Publishing Ltd. This paper presents a prototype of a thermal energy harvesting mechanism using both pyroelectric and piezoelectric effect. Thermal energy is one of abundant energy sources from various processes. Waste heat from a chip on a circuit board of the electronic device involves temperature differences from a few degrees C to over 100 °C. Therefore, 95 °C of a heat reservoir was used in this study. A repetitive time-dependant temperature variation is applied by a linear sliding table. The influence of heat conditions was investigated, by changing velocity and frequency of this linear sliding table. This energy harvesting mechanism employs Lead Zirconate Titanate (PZT-5H), a bimetal beam and two neodymium magnets. The pyroelectric effect is caused by a time-dependent temperature variation, and the piezoelectric effect is caused by stress from deformation of the bimetal. A maximum power output 0.54 μW is obtained at an optimal condition when the load resistance is 610 kω.
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