Output Power Of Harvester Research Articles

A wearable collaborative energy harvester combination of frequency-up conversion vibration, ambient light and thermal energy

In this study, a wearable multi-source collaborative energy harvester (MC-EH) is proposed to overcome the problem that a single-source EH is unstable from time to time. A customized ring monocrystalline silicon photovoltaic (PV) cell on the surface of energy harvester (EH) is used to harvest ambient light energy. The thermoelectric generator (TEG) converts the thermal energy of the temperature difference into electrical energy. A Macro-Fiber Composite (MFC) constitutes piezoelectric frequency up-conversion rotating structure, which harvest the low frequency vibration energy. The advantages of designed MC-EH are that energy of human body and environment can be fully harvested. Due to the difficulty in extracting small voltage generated by TEG independently, MC-EH was improved that it can extract thermal energy in the process of vibration energy extraction efficiently by the interface circuit. Results showed that maximum output power of harvester was about 4.48 mW, power density was 1.5 × 10−4 W/cm3. MC-EH can work efficiently in different human movement states and environments conditions. Therefore, MC-EH may provide electric energy for wearable device. Three energy harvesting systems are integrated into one compact structure by MC-EH, forming the advantages and originality of MC-EH that brought a case study of EH.

Topological optimization of a variable cross-section cantilever-based piezoelectric wind energy harvester

Wind energy is a typical foreseeable renewable energy source. This study constructs and optimizes a variable cross-section cantilever-based piezoelectric energy harvester for low-speed wind energy harvesting. The Galerkin approach is usually used to discretize the continuum model and then get the ordinary differential equations. However, this method is more suitable for calculating uniformity than the variable cross-sectional beam model. To solve this problem, we proposed an improved piecewise Galerkin approach for discretizing the continuum model with a variable cross section. By modifying the boundary expressions and modal functions between segments, it can improve both computation speed and accuracy. COMSOL simulations demonstrate that natural frequencies calculated via the improved method are more accurate than those of the traditional Galerkin method. The method of multiple scales is applied to determine the output power and critical wind velocity. A distinctive numerical approach is presented for shape optimization by combining the analytical calculation method with the particle swarm optimization (PSO) technique for low-speed wind energy harvesting. Additionally, the logic function is chosen to produce the optimal shape’s fitting expression for engineering applications. With all the improvements, the output power of a variable cross-section beam-based harvester reaches as much as 3.668 times that of a uniform beam model, demonstrating the importance of structural optimization for this type of energy harvesters. Finally, experiments are set up to verify the optimization procedure. Actually, it builds an analytical framework for the adaptive selection of variable-section piezoelectric cantilever wind-induced vibration energy harvesters.

Optimization for piezoelectric energy harvesters with self-coupled structure: A double kill in bandwidth and power

Vibration energy harvesting is promising to supply power autonomy for many electronic devices. This paper proposes a novel nonlinear piezoelectric energy harvester with a two-degree-of-freedom self-coupled structure. The operating frequency range and the power output of the new harvester is enhanced simultaneously compared with the conventional stopper-based nonlinear energy harvester. The dynamic model of the self-coupled structure is established, and then the bucket hat-like elastic potential energy function of the structure is obtained, which accounts for the superior performance of the harvester. Moreover, an optimization methodology for developing the nonlinear piezoelectric energy harvester was proposed. The conventional and novel energy harvesters were designed, optimized, and fabricated. Experimental results indicate that the maximum output power of the novel energy harvester can be enhanced to 3.54 times of that of the conventional energy harvester with a stopper structure. Besides, the working bandwidth is broadened from 4.7 Hz to 5.2 Hz. It is expected that this work is devoted to the future improvement of vibration energy harvesters in practical applications.

Energy Harvesting in Immersed Tunnel for Powering Wireless Sensor Nodes for Corrosion Monitoring

Collecting data from corrosion sensors in reinforced concrete structures demands intensive labor work, therefore measurements are only performed occasionally. A low-cost Wireless Sensor Network/Node (WSN) will eliminate the need for manual work and allow for continuous measurements if needed. For a distributed WSN over a large area, a concerning issue is how to power such devices. This paper, therefore, investigates the use of a reinforced concrete battery for powering WSNs. Results obtained from a real-world immersed tunnel, which has hundreds of electrochemical based corrosion sensors embedded into the reinforced concrete structure, shows that sufficient energy can be harvested from the sensors, to perform wireless transmission of corrosion data to a base-station. With an open circuit potential of 975 mV, the maximum harvested output power is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12.4~\mu \text{W}$ </tex-math></inline-formula> , while the minimum measured output power is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu \text{W}$ </tex-math></inline-formula> . The results also show that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.82~\mu \text{W}$ </tex-math></inline-formula> , with an open circuit potential of 727 mV, can be directly harvested from the reinforcement steel itself. Due to the fact that the steel volume can work as a large battery anode, a longer lifetime for the energy source is expected. Furthermore, we show that the harvested energy from the corrosion sensors will induce a galvanic corrosion rate of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.7~\mu \text{m}$ </tex-math></inline-formula> /year, when transmitting the corrosion data once a month. This indicates that there is no risk to the structural integrity when using this energy source.

Design and Development of a 2 × 2 Array Piezoelectric–Electromagnetic Hybrid Energy Harvester

Energy harvesting technology is regarded as a feasible solution for the continuous power supply of microelectronic devices. Efforts have been made to improve the output power of all kinds of energy harvesting devices. This paper reports a 2 × 2 array piezoelectric–electromagnetic hybrid energy harvester that achieves high power output through the combination of piezoelectric and electromagnetic conversion. The harvester included four piezoelectric–electromagnetic hybrid modules, each of which consisted of a piezoelectric sheet, a permanent magnet and a wound coil. The permanent magnet, also serving as the mass block of the cantilever beam when subjected to external stimulus, contributed to a large displacement of the vibration and generated high output power. At an acceleration of 1 g and a resonance frequency of 70.4 Hz, the measured maximum output power of the hybrid energy harvester was 66.08 mW, of which the piezoelectric and electromagnetic portions were 56.96 and 9.12 mW, respectively. Furthermore, in a charging experiment, a capacitor of 23.5 mF was charged to 11.5 V within 20 s, which demonstrates a practical application of the hybrid energy harvester for microelectronic devices.

Modeling and analysis of energy harvester based on galloping considering the non-homogeneous beam

ABSTRACT This paper proposes a piezoelectric energy harvester based on non-homogeneous beam, which is employed to capture wind energy by galloping. A distributed parameter model of piezoelectric energy harvester with the nonuniformity of cantilever beam is developed. The quasi steady state approximation is used to simulate the fluid force. The model is verified by the experimental results reported previously. The influences of load resistance, the position of piezoelectric patch, and the size of beam on the output power are studied. Finally, a set of optimization parameters are generated to study the performance of the energy harvester. The results show that compared with rectangular beam, the output power of piezoelectric energy harvester with non-homogeneous beam can be increased by 32%.

Proizvodnja i ispitivanje elektormagnetnih generatora milimetarske skale za udarne kretnje visokih amplituda

Environment vibrations are an important source of energy, often occurring at very low frequencies, but with large amplitude. The possibility to use the large amplitude of the motions is important to enhance the energy harvester's output power. In this paper, an electromagnetic energy harvester is designed and fabricated to produce electricity from low- frequency high amplitude impact motions using an elastic polyurethane cylinder. This millimeter-scale electromagnetic generator (MS-EMG) includes a movable magnet attached to a free sliding mass, a fixed coil, and a polyurethane holding chamber. Polyurethane is a very stable elastic polymer that provides continuous large-amplitude movement for the magnet and plays an effective role in impact capability. Therefore, the effect of impact excitation and the polyurethane foam was investigated simultaneously. The performance of the device was studied, experimentally, for the environment vibrations in the range of 1 to 10 Hz. The impact motions were applied using a simulator that was fabricated for this work. The fabricated MS-EMG with a volume of 1.07 cm3 and a mass of 8.74 g show the capability of producing a voltage of 44.41 mV and power of 10.48 µW over a 100 Oresistive load, using a 6 Hz frequency impact motion. Finally, an analytical model is used to simulate the device performance which showed a good agreement with the experimental results.

Low-speed flutter of artificial stalk-leaf and its application in wind energy harvesting

Developing wind energy harvester (WEH) by mimicking the leaf flutter may provide an innovative way for increasing the power efficiency and decreasing the cut-in speed. The low-speed flutter mechanism of the stalk-leaf system is investigated through introducing a frictionless hinge into the stalk-leaf finite element model. The aeroelastic system is established by the usage of doublet-lattice aerodynamics and the spline interpolation between structural motion and flow downwash. The critical flutter speed and frequency are analyzed via V-g method. The evolution of damping and frequency with wind speed which various from static air to Beaufort level 5 are simulated. The influence of inclined angle of the stalk on the flutter characteristics is studied. The stainless-steel artificial stalk-leaf systems with inclined angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° are fabricated and tested in wind tunnel. The wind energy harvesting performance is also measured by attaching macro-fiber composite patches on root of the stalk. It is found that the 30° stalk-leaf WEH has the lowest critical flutter speed, while the energy harvesting output (voltage and power) increases slowly with the increase of the wind speed. On the contrary, although the 90° stalk-leaf (vertical stalk) WEH has the steepest velocity-voltage and velocity-power curve, it also has the highest cut-in speed. In the preliminary tests, the 30° stalk-leaf WEH outputs steady power density of 47.46 μW cm−3 with stable oscillating frequency of 6.6 Hz at 11 m s−1 wind, while the 90° stalk-leaf WEH outputs power density of 92.88 μW cm−3 with oscillating frequency of 7.2 Hz at the same wind speed. The stalk-leaf design presents a possible way to balance the performance between the high efficiency and the low cut-in speed for the WEHs.

Cut-corner prism piezoelectric energy harvester based on galloping enhancement mechanism

To improve the efficiency of harvesting energy, a cut-corner prism piezoelectric energy harvester based on galloping enhancement is designed in this study. Galloping is caused by the pressure difference between the upper and lower surfaces of the prism. Numerical simulations indicate that the cut-corner can reduce the occurrence of the shear layer reattachment phenomenon and also increase the strength of the secondary backflow between the shear layer and the lateral side of the prism, thereby raising the pressure difference between the upper and lower surfaces of the prism. The effect of cut-corner size on the performance of cut-corner prism energy harvesters is investigated experimentally. The results show that the optimal range for the prism is when the lengths of the cut-corner windward side and parallel side are 0.2B–0.4B (B is the length of the prism side) and 0.5B–0.6B, respectively. At a wind speed of 6.24 m/s and a resistance of 1 × 105Ω, the maximum output power of the cut-corner prism energy harvester with a windward side length of 0.4B and a parallel side length of 0.6B can reach 47.5 mW, which is 261% higher than that of the reference square prism, effectively raising the performance of the piezoelectric energy harvester.

Resource Allocation in Vibration Energy Harvesters

This paper studies the optimization of mechanics and resource allocation in linear vibration energy harvesters operating under an overall size constraint. In such harvesters, the volume aspect ratio and the stroke direction should be carefully selected to maximize output power and power density. Further, because the proof mass and spring stroke must share the available size along the stroke direction, a mass-stroke design trade-off results; the trade-off is optimized here. The optimization further leads to a universal metric the enables the comparison of linear vibration energy harvesters designed to operate in a limited volume. Examination of this metric results in guidelines and best practices for selecting harvester dimensions and shape for a given volume constraint, all based on the dimensional harvester optimization for maximum size-constrained output power. This paper offers several key contributions. First, it provides an evaluation and optimization of the impact that volume shaping and volumetric resource allocation have on the output power of linear vibration energy harvesters. Second, it develops a “universal normalized surface” relating output power to dimensional harvester design. The surface expresses the performance limit of space-constrained linear vibration energy harvesters in terms of their output power density. This leads to universal guidelines for harvester design. Finally, benchmarking harvesters reported in the literature against the universal surface demonstrates that their output performances lie on or below the surface, despite large variations in their exogenous design variables such as vibration amplitude, frequency, volume etc. Thus, this paper offers an effective method to evaluate mechanical design and optimization in state-of-the-art linear vibration energy harvesters under volume constraints, a scenario suited for IoT applications. [2021-0074]

Energy harvesting approach for trackside health monitoring devices in railroads

Design, modelling, simulation and lab test of a trackside electromagnetic energy harvesting (TEEH) approach for an AC electrified railway is provided in this study. By collecting the electromagnetic energy inspired from track current, an alternative energy source along the trackside can be achieved, which is not sensitive to weather and location factors. This study aims to verify the feasibility of TEEH and provide a guideline for future study. The electromagnetic field distribution model of the rail is built through theoretical calculations and FEM simulation. The relationship between harvester parameters and output power is confirmed. A TEEH prototype test bench has been built to verify the theory. The result indicates a close match. The average output power of 9.2 mW is achieved from a Φ57 × 30 mm hollow coil when the track current is 600 A 50 Hz. This study proposed a detailed derivation and modelling process, providing a preliminary reference and guidance for the design of an electromagnetic energy harvester.

High-isolated WiFi-2.4 GHz/LTE MIMO antenna for RF-energy harvesting applications

In this article, a two-port novel structure with a common shared ground stub with enhanced isolation for RF-energy harvesting for WiFi-2.4 GHz/LTE applications is presented. The optimized antenna (antenna (4): 0.6λ0 × 0.4λ0 × 0.0128λ0 mm3) is selected as proposed antenna at design frequency (f0 = 2.4 GHz) among antennas (1–4) after study of simulated results through HFSS version 18.2. Two optimized identical elements are closely separated at 0.067 λ0 distance and an enhanced isolation (greater than 49 dB) and perfect impedance matching have been obtained. Proposed antenna covers a wide bandwidth of 2.25–2.98 GHz (simulated), 2.24–3.05 GHz (measured) and fractional bandwidth of 27.91% (simulated), 30.62% (measured) respectively with 2.4 & 2.8 GHz resonance. A peak gain of 2.4 dB at 2.4 GHz and 4.7 dB at 2.8 GHz has been obtained. The antenna exhibits a 95.2% radiation efficiency and 0.8 W/kg specific absorption rate (SAR). MIMO performance metric of the proposed antenna in terms of envelope correlation coefficient (ECC), diversity gain (dB), total active reflection coefficient (TARC), mean effective gain (MEG), and channel capacity loss (CCL) has been evaluated and found in close agreement with practical standards. Moreever, the proposed antenna is further tested for harvested power wherein a maximum harvested voltage of 4.7 V, 4.88 mW Friis equation output, 2.91mW harvested output power and 54.98% power conversion efficiency in 2.4–2.5 GHz band at 20dBm power source are recorded.

A Method to Optimize the Output Power of MEMS Vibrational Energy Harvester

A Method to Optimize the Output Power of MEMS Vibrational Energy Harvester

Development and application performance of road spring-type piezoelectric transducer for energy harvesting

Piezoelectric pavement energy transducers have attracted attention because they can directly convert mechanical energy into electric energy, thus enabling environmental protection, energy regeneration, and high energy output. However, existing piezoelectric transducers used in pavements made of piezoelectric ceramics are brittle and have short lives under long-term vehicle loading fatigue. In the present study, to raise the efficiency of energy harvesting, a new road piezoelectric transducer with a specified flexibility was designed and fabricated with two types of structures, plane and spring types, and their output performances were evaluated and compared. The test results showed that at the excitation frequency of 10 Hz and test displacement of 2 mm, the maximum output power of the spring piezoelectric energy harvester reached 14.183 mWmax for a matching resistance of 1 kΩ, and the output power was 2.24 times that of the plane piezoelectric energy harvester. Then, a fatigue test under an excitation frequency of 10 Hz and testing displacement of 2 mm was performed for the durability of the road spring-type piezoelectric transducer unit, and results showed that the piezoelectric transducer has a good durability and meets the general conditions for road engineering. Finally, the road spring-type piezoelectric energy harvester was tested on an actual road. When a pickup truck drove at a speed of 40 km h−1, the output power of the spring piezoelectric energy harvester reached a maximum of 592.77 mWmax for a matching resistance of 3 kΩ. Thus, this spring-type piezoelectric harvester can be ideally applied in road traffic.

Enhancing output power of rotational electret energy harvester by synchronized switch harvesting on inductor

A nonlinear interface circuit, known as synchronized switch harvesting on inductor (SSHI), for in-plane rotational electret kinetic energy harvesters (EHs) was developed. An explicit generator model is derived to verify the applicability of SSHI, which was originally proposed for the piezoelectric EH, on an in-plane electret EH. Experimentally, 505 μW was harvested with SSHI at a rectified voltage of 142 V for an in-plane rotational electret EH rotating at 1 rps, which is 2.47 times of that with a full-bridge rectifier, and which is in good agreement with the simulation result. The circuit efficiency and criteria for the inductor selection were clarified through circuit analysis based on spice simulation. It is found that the power dissipation of voltage-divider and rectification diodes becomes pronounced as the load voltage increases, constraining the efficiency. The inductor, which usually dominates the circuit volume, can be miniaturized for electret EHs, because the voltage inversion ratio, a benchmark of the SSHI performance, turns out to be insensitive to the series resistance of the inductor. The self-powering ability of the proposed circuit is also presented.

Synergetic enhancement of the energy harvesting performance in flexible hybrid generator driven by human body using thermoelectric and piezoelectric combine effects

Flexible thermoelectric-piezoelectric generator (f-TPEG) has emerged as the leading candidate to realize long-term biomedical monitoring-based ubiquitous healthcare services. We developed a f-TPEG composed of a piezoelectric (PE) poly(vinylidene fluoride-co-trifluoroethylene) thin film and thermoelectric (TE) bismuth telluride-based alloy blocks. The surficial properties of TE and PE components of f-TPEG were thoroughly optimized to minimize the loss of output performance and enhance the mechanical stability. The f-TPEG harvested a maximum electric voltage of ~17 V and current signals of ~3.8μA at a temperature difference of 3 K by periodic bendings: The harvested output power of the fabricated hybrid energy generator was well integrated without sacrificing each PE and TE-based energy generation. In addition, to confirm the biological energy harvesting efficiency of the generator, we demonstrated the f-TPEG taped onto human fingers, which converts an output voltage of about 8 V and a current pulse of about 6 μA. The results obtained herein suggest that the f-TPEG would play a variety of important roles in wearable device, which needs long-term biomedical monitoring and applications in smart clothing.

A new concept of frequency-excitation-up conversion to improve the yield of linear piezoelectric generators

A new and novel frequency-excitation up-conversion (FEUC) mechanism achieved by converting low-frequency excitation into friction-induced vibration (FIV) is proposed to improve the output power of linear piezoelectric energy harvesters at ultra-low ambient frequencies. For comparison, a conventional resonant energy harvester and an impact-driven energy harvester are created, the output power is measured at the resonant frequency under a 0.5 g driving acceleration. Then, a friction system driven by reciprocating sliding and capable of generating FIV is established. The driving reciprocating is equivalent to the low-frequency ambient vibration, and a single piezoelectric cantilever beam is added to the friction system for energy recovery. The results show that, compared with the impact-driven energy harvester, the vibration frequency can be increased hundreds of times, and the excitation level can be improved several orders of magnitude by the friction nonlinearities. The impedance of the energy harvester is reduced significantly due to a sharp increase in the vibration frequency. In addition, the open-circuit voltage amplitude is not substantially lowered due to the significantly increased excitation level, even though the piezoelectric cantilever beam operates in a high-frequency condition and in the absence of resonance. Therefore, the output power is dramatically improved. The effectiveness and superiority of the FEUC strategy proposed in this work has been demonstrated.

Analysis of Irreversible Thermodynamic Losses in Emissive-Energy Harvesters Based on Photon Beams

An analysis of irreversible energy losses that happen upon emissive-energy conversion is presented in this article. For this, we show that in these converters, the total amount of entropy produced in the conversion is proportional to the number of emitted photons, which justifies their description as counterparts of thermophotovoltaic engines. In the last part of this article, using a model of low-intensity photon beams and the detailed balance principle, we show the effects of irreversibilities on the output power and efficiency of emissive-energy harvesters.

Horizontally Assembled Trapezoidal Piezoelectric Cantilevers Driven by Magnetic Coupling for Rotational Energy Harvester Applications

Horizontally assembled trapezoidal piezoelectric cantilevers driven by magnetic coupling were fabricated for rotational energy harvester applications. A dodecagonal rigid frame with an attached array of six trapezoidal cantilevers served as a stator for electrical power generation. A rotor disk with six permanent magnets (PMs) interacted magnetically with the counterpart cantilever’s tip-mass PMs of the stator by rotational motion. Each trapezoidal piezoelectric cantilever beam was designed to operate in a transverse mode that utilizes a planar Ag/Pd electrode printed onto lead zirconate titanate (PZT) piezoelectric thick film. The optimized distance between a pair of PMs of the rotor and the stator was evaluated as approximately 10 mm along the same vertical direction to make the piezoelectric cantilever beam most deflectable without the occurrence of cracks. The theoretically calculated resistance torque was maximized at 46 mN·m for the optimized trapezoidal piezoelectric cantilever. The proposed energy harvester was also demonstrated for wind energy harvester applications. Its harvested output power reached a maximum of approximately 22 mW at a wind speed of 10 m/s under a resistive load of 30 kΩ. The output performance of the proposed energy harvester makes it possible to power numerous low-power applications such as smart sensor systems.

Hydrokinetic piezoelectric energy harvesting by wake induced vibration

Piezoelectric energy harvesters capture various kinetic energy to power wireless sensors. A new hydrokinetic piezoelectric energy harvester using wake-induced vibration (WIV) is proposed in this paper. The mathematical model of the hydrokinetic energy harvester is established to consider the effect for different velocity regions. Circulating water-channel experiment is carried out to exam the performance of the harvester. The experimental results show that the model can predict the output power appropriately. Frequency analysis indicates that the performances in VIV region and WIV region are dominated by the wake vortex frequency and the natural frequency respectively. The flow pattern changes greatly under different spacings which are divided into extended-body, reattachment and co-shedding regions. The maximum output power of the harvester locates in the reattachment region. The maximum experimental power densities for the inverted D-shaped, circular and D-shaped cylinders are 570.3W/m3, 596.4W/m3, 1074W/m3, respectively. They are 43.2, 25.3, 31 times of that without wake interference. The corresponding optimal experimental spacing ratios are 5, 2.6 and 2, respectively. Compared with the case without wake interference, the output power of the hydrokinetic piezoelectric energy harvester using WIV is significantly improved.