Matching Load Resistance Research Articles

Investigation of a double-PCM-based thermoelectric energy-harvesting device using temperature fluctuations in an ambient environment

Energy-harvesting devices, consisting of thermoelectric modules and phase change materials (PCMs), can extract energy from the ambient environment for the self-power supply of many small electronic devices such as wireless sensors. However, due to the distinct temperature ranges of various seasons in different places, these devices’ power generation performance may be seriously impaired. In this paper, a new double-PCM-based thermoelectric energy-harvesting device based on temperature fluctuations in the ambient environment is proposed to improve device performance. A double-PCM-based device has been built and tested in an environment with a large temperature range (0–40°C) for three days. Experimental results show that the average output power of the double-PCM-based thermoelectric energy-harvesting device under matched load resistance outperforms that of the single-PCM device by 35.8%. A one-dimensional unsteady heat transfer model is established to describe the temperature variation of PCMs. The influence of phase change is considered through variations in PCMs’ specific heat capacity. This work demonstrates that the proposed double-PCM-based thermoelectric energy-harvesting device performs better over a large temperature range and is more suitable for small electronic devices operating at different times and in different places.

Analysis of the Key Factors Affecting the Capability and Optimization for Magnetostrictive Iron-Gallium Alloy Ambient Vibration Harvesters.

The basic phenomena of a cantilever energy harvesting device based on iron-gallium alloy magnetostrictive material for low frequency were systematically studied. The results highlighted how the physical parameters, geometric structure and bias conditions affected the vibration harvesting capacity through a thorough experimental aimed at enhancing the vibration energy harvesting capacity through an optimal design. How the performance is affected by the configuration of the multi-layers composite beam, material and dimensions of the elastic layer, arrangement position and number of bias magnets, the matching load resistance and other important design parameters was studied in depth. For the first time, it was clearly confirmed that the magnetic field of bias magnets and electromagnetic vibration shaker have almost no effect on the measurement of the voltage induced from the harvester. A harvesting power RMS up to 13.3 mW and power density RMS up to 3.7 mW/cm3/g was observed from the optimized prototype. Correspondingly, the DC output power and power density after the two-stage signal processing circuit were up to 5.2 mW and 1.45 mW/cm3/g, respectively. The prototype successfully powered multiple red light emitting diode lamps connected in a sinusoidal shape and multiple red digital display tubes, which verified the vibration harvesting capability or electricity-generating capability of the harvester prototype and the effectiveness of the signal converter.

Design and Research on a Nonlinear 2DOF Electromagnetic Energy Harvester With Velocity Amplification

In order to power the microelectronic devices of the Internet of Things in the low-frequency broadband vibration environment, a novel nonlinear 2DOF electromagnetic energy harvester was proposed based on the magnetic levitation structure and velocity amplification mechanism. The electromechanical coupling model was established and numerically simulated to analyze the generating characteristics. A prototype was fabricated and tested to verify the theoretical model. The influences of the key parameters, including the gap between the suspended magnet and the lower spring, excitation acceleration, spring stiffness, mass of copper cylinder, on the generating characteristics were studied. When it was subjected to a harmonic excitation with acceleration amplitude of 0.8g, the measured open-circuit voltage reached peaks of 3.13 V at 8 Hz and 2.93 V at 13.5 Hz, respectively. The optimal output power at 8 Hz was 10.18 mW with the matched load resistance of 250~Ω. Both the experimental and theoretical results demonstrated that this novel electromagnetic energy harvester had obvious advantages in increasing the output power and widening the bandwidth.

Linear freestanding electret generator for harvesting swinging motion energy: Optimization and experiment

Nowadays, harvesting mechanical energy from body motion for powering wearable electronics has gained great attention. Swinging motion is a common motion in the human body. Herein, we demonstrate a linear grating-structured freestanding electret generator with the electrodes as the slider for harvesting arm swinging energy. The analytical solutions of the outputs of the generator under uniformly accelerated motion are obtained from its theoretical model. It is verified that the formula of average power under uniform motion can be used to estimate the matched load resistance and optimize the parameters of the generator under uniformly accelerated motion, and the optimized results are independent of the motion mode. The generator gets the maximum power when the effective length of the slider is half that of the stator and can double the output power compared with conventional generators with electrodes as the stator. We optimized the generator by taking the fringe effect of the electric field and the parasitic capacitance into consideration, and the optimized generator generates tens of microwatts of power from arm swinging.

A low-frequency, broadband and tri-hybrid energy harvester with septuple-stable nonlinearity-enhanced mechanical frequency up-conversion mechanism for powering portable electronics

This study involves the design and investigation of a low-frequency, broadband, tri-hybrid energy harvester. The harvester consists of a novel septuple-stable nonlinearity-enhanced mechanical frequency up-conversion mechanism that not only enhances the output performance of the frequency up-conversion via inter-well motions, and also offers a wide and highly efficient operating bandwidth at low acceleration via the combination of resonant inter-well oscillation behavior and non-resonant behavior. The integration of an impact-driven piezoelectric generator, an electromagnetic generator, and a freestanding-mode triboelectric nanogenerator allows more energy to be harvested from a single mechanical motion, which further improves the power density. A prototype is fabricated and demonstrated using an electrodynamic shaker and various human motions. In the electrodynamic shaker test, the prototype exhibits a broad bandwidth of 2–12.5 Hz and generates an output power of 24.17 mW, corresponding to a power density of 700.3 W/m3 across a matching load resistance of 35 kΩ at a frequency of 5 Hz and 1 g acceleration. Under various basic human motions such as handshaking, walking, and slow running, the prototype can generate output powers of 38.5, 24.5, and 27.2 mW, respectively, in horizontal positions and 42.7, 10.2, and 33.1 mW, respectively, in vertical positions. A comparison study is also presented to demonstrate that the tri-hybrid prototype can produce a much higher power density than other devices reported recently. This work makes significant progress toward hybrid-energy harvesting from various human motions and its potential application in powering wearable devices.

Numerical study on nonuniform segmented enhancement method for thermoelectric power generator

Thermoelectric power generators (TEGs) have received considerable attention in the vehicular waste heat recovery. Large temperature difference between hot-side end and cold-side end of TE modules should be maintained to keep large power generation. However, the scaling-up problem of inevitably temperature drop of exhaust gas along the flow direction of vehicles is introduced when multiple TE modules are assembled. In this work, a three-dimensional fluid–thermal–electric multiphysics model with equivalent properties of TE modules is established. The influencing mechanism of longitudinal vortex generator (LVG) pair number and distribution in the hot-side heat exchanger on the local power generation performance of the TEGs is examined. It is found that the extent of the local power generation enhancement gets smaller or even deteriorates at the downstream TE modules by uniformly increasing the LVG pair number along the flow direction. Hence, to make the heat flux efficiently utilized, a nonuniform segmented enhancement method is used for the hot-side heat exchanger. The results show that compared with the TEG with a uniform heat exchanger or a downstream-denser heat exchanger, the total Seebeck voltage generated by the TEG with an upstream-denser heat exchanger is 28% higher, and its output power is 64.4% higher at the matched load resistance. The TEG with the upstream-denser heat exchanger significantly improves the overall power generation performance without additional pumping power.

A human locomotion driven hybrid energy harvester for wrist wearable applications

In this work, a human locomotion driven hybrid energy generator has been proposed and experimentally validated for scavenging significant biomechanical energy from natural motion of arm swinging, to be used for wrist-wearable smart device applications. A proposed hybrid electromagnetic (EM) and triboelectric (TE) generator can deliver much higher output power than that of the individual harvesting device unit due to the combinational operation of EM and TE mechanisms under the same applied mechanical movements. A novel curved structural design based energy harvester is proposed from the comparative analysis of human hand swinging motion with double pendulum motion, which helps to enhance the output performance and design it fit to wear on wrist. The swinging of human arm during walking and running initiates a freely movable magnetic metal ball to oscillate inside the curved structure through both EM and TE part. The EM part consists of two coils wrapped around the curved body, one at each end and micro-structured Polydimethylsiloxane (PDMS) film is attached on the inner wall of curved body along with copper electrode for TE part. A prototype of the hybrid harvester has been fabricated and tested. The EM and TE devices are capable of delivering maximum 84.37mW peak power at 49.2Ω matching load resistance and 1.86μW peak power at 10MΩ load resistance respectively which are considerably higher than the trending state-of-the-art devices.

Miniaturized springless hybrid nanogenerator for powering portable and wearable electronic devices from human-body-induced vibration

In this paper, a springless hybridized NG (nanogenerator) was newly designed to have a non-resonant behavior, in which the output power continuously increases with the input frequency and amplitude. To achieve a considerably higher output power generation at low-frequency vibrations and low amplitude, the proposed springless hybrid electromagnetic and triboelectric nanogenerator (SHEMG-TENG) utilizes a dual-Halbach array, which is fabricated with contact-separation and sliding-mode TENGs. The proposed SHEMG-TENG is fabricated and verified from a vibration exciter and human-body-induced vibration. Under the vibration exciter test (horizontal position), the fabricated SHEMG-TENG generated an output current and power of 2.04 mA and 5.41 mW, respectively, which corresponds to a volume power density of 395.4 W/m3 under a matching load resistance of 1.1 KΩ at an applied frequency and acceleration of 6 Hz and 1 g, respectively. For a number of basic human activities such as handshaking, walking, and slow running, the SHEMG-TENG was able to deliver output powers are 2.9 mW, 1.2 mW, and 1.7 mW (horizontal position), respectively, and 1.6 mW, 0.74 mW, and 2.3 mW (vertical position), respectively. This work presents an important step toward realizing SHEMG-TENG from human-body-induced vibration powered to enable wearable and portable smart electronic applications, and is expected to be widely accepted by the general public in their daily lifestyle.

POWER GENERATION FROM COMBUSTED “SYNGAS” USING HYBRID THERMOELECTRIC GENERATOR AND FORECASTING THE PERFORMANCE WITH ANN TECHNIQUE

Gasification and combustion of de-oiled Pongamia Pinnata seed cake is done to produce higher energy biomass waste heat “syngas” for generating power using hybrid thermoelectric generator (TEG). A test rig is fabricated and experiments conducted with synthetic oil (Therminol-55) as the heating fluid under water and air-cooled methods. The hot side temperature is varied from 200 - 250ºC while the coolant temperature is maintained at 30 oC for both water and air respectively. Experimental results showed 22.27% enhancement in electric power at a constant hot side temperature of 250 ºC under water cooled method. In addition, simulation results for the above mentioned conditions using artificial neural networks (ANN) tool in MATLAB also agreed well with the sample experimental results. The performance parameters such as open circuit voltage, maximum output power and matched load resistance are forecasted using ANN upto maximum possible hot side temperature of 350ºC. Further, the financial evaluation of Biomass gasified-thermoelectric system ($0.0018/kWh and in terms of Indian currency is ₨ 0.0676/kWh) is found to be almost negligible on comparison with other available renewable energy technologies.  

Nonlinear Piezoelectric Energy Harvester with Ball Tip Mass

In this study, a nonlinear piezoelectric energy harvester (PEH) with a ball tip mass was designed and fabricated for broadband energy harvesting. The proposed nonlinear PEH exhibits two resonant frequencies (5 and 15 Hz) and can harvest a considerable amount of electrical energy, whereas a conventional PEH with a rigid tip mass only exhibits one (15 Hz). The minimum acceleration that can induce nonlinearity in the proposed PEH was determined to be 3 m s–2. In order to maximize the electrical output of the proposed PEH, 0.1 mm was selected as the optimal vibration amplitude of the ball among three options (0.1, 0.5, and 1.0 mm). The maximum output power of the proposed PEH was measured as 13.5 mW at 15 Hz and at a load resistance of 30 kΩ, which is the matching load resistance calculated and verified with the experimental result. The output power of the proposed PEH was measured to be 1.8 mW at 5 Hz and 45 kΩ, whereas that of the conventional PEH at 5 Hz was 0.03 mW, implying that the proposed PEH possesses one additional resonant frequency over the conventional PEH. In addition, the proposed PEH performs significantly better than the conventional PEH in terms of broadband energy harvesting. At a power level of 100 μW, the proposed PEH at 3 m s–2 provides a bandwidth of 20 Hz, which is more than 133% wider than the 15 Hz provided by the conventional PEH. By utilizing the nonlinearity with a ball tip mass, the PEH vibration is capable of harvesting considerable electrical energy from more than two resonant frequencies.

High Efficiency Harmonic Harvester Rectenna for Energy Storage Application

This work presents harmonic harvester Rectenna integrated power management circuitry for improving RF-DC power conversion efficiency. The circuitry is developed for battery charging or energy storage application; resistance emulation method is used to realize a matching load resistance at output terminals. The proposed technique is useful for harvesting near maximum output power from the dual rectifiers (fundamental and harmonics) independently. Also, it delivers the combined maximal power to the energy storage cell. The power management module based on dual input buck-boost converter with simple open loop control is utilized.

Freestanding-electret rotary generator at an average conversion efficiency of 56%: Theoretical and experimental studies

Harvesting ambient mechanical energy is a crucial method to gain low-cost, clean and sustainable electric energy for self-powered electronics. Herein, we develop a freestanding-electret rotary generator and the explicit analytical solutions of the output current, voltage and average power are obtained from its theoretical model. The maximum average output power and the matched load resistance can be estimated directly from simple formulas. The generator using an inexpensive micro-nano-structured PTFE electret film achieves an open-circuit voltage with an amplitude of 650V and a conversion efficiency about 56% with 10.5mW output power at a rotation rate of 750rpm. We find that the opposite charges injected into the back of the electret during the charging process tremendously counteract the effect of the charges on the front and reduce the output power. Eventually the theoretical and experimental results are very close when the net charge density is used instead of the surface charge density.

Experimental investigation on thermoelectric generator with non-uniform hot-side heat exchanger for waste heat recovery

In typical gas-to-liquid thermoelectric generators for waste heat recovery, the stream-wise gas temperature drop in the hot-side heat exchanger leads to the decrease of power output of the whole system. Denser fins are usually arranged on the downstream of the hot-side heat exchanger to improve the uniformity of temperature field and thus the total power output performance of thermoelectric generators when the steam-wise temperature drop is small, but it is not benificial when the steam-wise temperature drop is large. This work investigates the effect of configuration of winglet vortex generators on the performance of thermoelectric generator system. Three sets of hot-side heat exchangers, including a heat exchanger with smooth channel, a heat exchanger with uniform configuration of winglet vortex generators and a heat exchanger with non-uniform configuration of winglet vortex generators, are tested in a gas-to-liquid thermoelectric generators experimental system. The hot-side Reynolds number ranges from 3000 to 6400 and the hot-side inlet temperature is within 523–553K. The experimental results show that the total and net power output of thermoelectric generator under matched load resistance with uniform heat exchanger can respectively outperform that with smooth heat exchanger by 97.5% and 77.7% in average, whereas that with non-uniform heat exchanger by 189.1% and 177.4% in average. Since the uniform and non-uniform heat exchangers have the same number but different configuration of winglet vortex generators, this kind of active cascade control of heat transfer enhancement elements is proved to be effective in improving the power output of thermoelectric generator system without increasing pumping power.

High performance bimorph piezoelectric MEMS harvester via bulk PZT thick films on thin beryllium-bronze substrate

This letter presents a high performance bimorph piezoelectric MEMS harvester with bulk PZT thick films on both sides of a flexible thin beryllium-bronze substrate via bonding and thinning technologies. The upper and lower PZT layers are thinned down to about 53 μm and 76 μm, respectively, and a commercial beryllium bronze with the thickness of about 50 μm is used as the substrate. The effective volume of this device is 30.6 mm3. The harvester with a tungsten proof mass generated the close-circuit peak-to-peak voltage of 53.1 V, the output power of 0.979 mW, and the power density of 31.99 mW/cm3 with the matching load resistance of 360 kΩ at the applied acceleration amplitude of 3.5 g and the applied frequency of 77.2 Hz. Meanwhile, in order to evaluate the stability, the device was measured continuously under applied acceleration amplitudes of 1.0 g and 3.5 g for one hour and demonstrated a good stability. Then, the harvester was utilized to light up LEDs and about twenty-one serial LEDs were lighted up at resonance under an applied acceleration amplitude of 3.0 g.

Performance Analysis of (Bi2Te3-PbTe) Hybrid Thermoelectric Generator

A theoretical analysis on the performance of (Bi2Te3-PbTe) hybrid thermoelectric generator (TEG) is presented in this paper. The effect of different performance parameters such as output voltage, output current, output power, maximum power output, open circuit voltage, Seebeck co-efficient, electrical resistance, thermal conductance, figure of merit, efficiency, heat absorbed and heat removed based on maximum conversion and power efficiency have been analyzed by varying the hot side temperature up to 350oC and by varying the cold side temperature from 30oC to 150oC. The results showed that a maximum power output of 21.7 W has been obtained with the use of one hybrid thermoelectric module for a temperature difference of 320oC between the hot and cold side of the thermoelectric generator at matched load resistance. The figure of merit was found to be around 1.28 which makes its usage possible in the intermediate temperature (250oC to 350oC) applications such as heating of Biomass waste, heat from Biomass cook stoves or waste heat recovery etc. It is also observed that the hybrid thermoelectric generator offers superior performance over 250oC of the hot side temperature, compared to standard Bi2Te3 modules

Power Optimization Configuration for Piezoelectric Cantilever Arrays

This paper investigates the changes in the output of the piezoelectric cantilever arrays when connected in different configurations. In this research matching load resistance determined and optimum output was measured by connecting the piezoelectric cantilever arrays to resistance ranging from 10 Ω to 1 MΩ while excited by constant vibration source at frequency of 300 Hz and acceleration of 1-g level. The result shows that matching load resistance for one single piezoelectric cantilever is 13 KΩ. When two, three and four cantilevers are connected in series, the matching load resistance is 26 kΩ, 39 kΩ and 52 kΩ respectively. While in parallel connection, matching load resistance reduced to 6.5 kΩ, 4.5 kΩ and 3.5 kΩ for two, three, and four connected cantilevers respectively. In series configuration, the voltage output produced is much higher as compared to the piezoelectric cantilever arrays that are connected in parallel connection. The voltage output of the piezoelectric cantilever increased from 3.41V to 6.09V when it is connected in series configuration with same polarity. Whereas in term of power output, piezoelectric cantilever arrays in parallel configuration produce higher power output as compared to piezoelectric cantilever arrays in series connection. The maximum power increased from 272μW to 521μW when two cantilevers are connected in parallel configuration with same polarity.

A handy motion driven hybrid energy harvester: dual Halbach array based electromagnetic and triboelectric generators

In this work, we have proposed and experimentally validated of hybrid electromagnetic and triboelectric energy harvester using dual Halbach magnets array excited by human handy motion. Hybrid electromagnetic (EM) and triboelectric (TE) generator that can deliver an output performance much higher than that of the individual energy-harvesting unit due to the combination operation of EM and TE mechanisms under the same mechanical movements. A Halbach array concentrates the magnetic flux lines on one side of the array while suppressing the flux lines on the other side. Dual Halbach array allows the concentrated magnetic flux lines to interact with the same coil in a way where maximum flux linkage occurs. When an external mechanical vibration is applied to the hybrid structure in the axial direction of the harvester, the suspended mass (two sided dual-Halbach-array frame) starts to oscillate within the magnetic springs and TEG part. Therefore, the TEG part, the Al film and microstructure PDMS film are collected into full contact with each other, generating triboelectric charges due to the various triboelectricities between them. A prototype of the hybrid harvester has been fabricated and tested. The EMG is capable of delivering maximum 11.5mW peak power at 32.5Ω matching load resistance and the TEG delivering 88μW peak power at 10MΩ load resistance.

Flexible Piezoelectric Energy Harvesting from Mouse Click Motions

In this paper, we study energy harvesting from the mouse click motions of a robot finger and a human index finger using a piezoelectric material. The feasibility of energy harvesting from mouse click motions is experimentally and theoretically assessed. The fingers wear a glove with a pocket for including the piezoelectric material. We model the energy harvesting system through the inverse kinematic framework of parallel joints in a finger and the electromechanical coupling equations of the piezoelectric material. The model is validated through energy harvesting experiments in the robot and human fingers with the systematically varying load resistance. We find that energy harvesting is maximized at the matched load resistance to the impedance of the piezoelectric material, and the harvested energy level is tens of nJ.

A Non-Resonant Magnetoelectric Energy Converter for Scavenging Magnetic Field Energy From Two-Wire Power Cords

A non-resonant magnetoelectric (ME) energy converter is presented for scavenging power-frequency magnetic field energy from two-wire power cords. The device is composed of a Terfenol-D/Pb(Mg1/3Nb2/3)O3-PbTiO3(PMNT)/Terfenol-D ME transducer, a NdFeB manget, and E-shaped magnetic yokes. The ME transducer, the magnet, and the magnetic yokes constitute a magnetic circuit, and the bias magnetic field of the ME transducer can be tuned by adjusting the contact area between the magnet and the magnetic yokes to obtain optimal power output. Meanwhile, the power-frequency magnetic field of the power cord is concentrated to the ME transducer by the magnetic yokes, which can potentially improve the power output of the device. Experiments were undertaken to evaluate the potential of energy scavenging from nearby power cords. When coupled to an appliance power cord carrying a current of 16 A, the device generated a rms voltage of 2.46 V and a maximum power of $6.05 \times 10^{\mathrm {-6}}$ W with a matching load resistance of $\sim 1~\text{M}\Omega $ . At a duration of 205 ms, the device can supply power for a temperature-humidity wireless sensor through an up-conversion management circuit with the power consumption of 90 mW at transmitting and 18 mW at receiving.

Performance Analysis of (Bi2Te3-PbTe) Hybrid Thermoelectric Generator

The performance of (Bi<sub>2</sub>Te<sub>3</sub>-PbTe) hybrid thermoelectric generator (TEG)<strong> </strong>composed of n-type Bismuth Telluride and p-type Lead Telluride semiconductor materials is presented in this paper. <strong> </strong>The effect of different performance parameters such as output voltage, output current, output power, maximum power output, open circuit voltage, Seebeck co-efficient, electrical resistance, thermal conductance, figure of merit, efficiency, heat absorbed and heat removed based on maximum conversion and power efficiency have been theoretically analyzed by varying the hot side temperature of the hybrid thermoelectric generator up to 350<sup>o</sup>C and by varying the cold side temperature from 30<sup>o</sup>C to 150<sup>o</sup>C. The results showed that a maximum power output of 21.7 W has been obtained with the use of one hybrid thermoelectric module for a temperature difference of 320<sup>o</sup>C between the hot and cold side of the thermoelectric generator at matched load resistance. The figure of merit was found to be around 1.28 which makes its usage possible in the intermediate temperature (250<sup>o</sup>C to 350<sup>o</sup>C) applications such as heating of Biomass waste, heat from Biomass cook stoves or waste heat recovery etc. It is also observed that the hybrid thermoelectric generator offers superior performance over 250<sup>o</sup>C of the hot side temperature, compared to standard Bi<sub>2</sub>Te<sub>3 </sub>modules.