Standard Energy Harvesting Research Articles

A compact self-powered inductor-less piezoelectric energy harvesting circuit using gyrator

In traditional low-frequency energy harvesting circuits, a large matched inductor with a large size is unavoidable. To reduce the size of the circuit, this paper proposes a compact self-powered inductor-less high-efficiency piezoelectric energy harvesting circuit using a low-power-consumption gyrator. A self-powered floating gyrator inductor is used in place of an inductor in the proposed circuit, and the required phasor response is acquired by using its voltage–current (V–I) relationship. The proposed circuit offers easy adjustability and performance benefits in small integrated circuits packages. The proposed circuit can be cost-effective and provide reduced area advantages in autonomous self-powered Internet-of-Things and wireless sensor nodes applications. Regarding harvested energy, the proposed circuit with a storage capacitor of 0.24 F can obtain 320% improved performance than standard energy harvesting along with the lowest power consumption of 0.25 µW in self-powered operation. The proposed technique can also be applied to similar piezoelectric energy harvesting strategies with large inductors.

A comparative analysis of parallel SSHI and SEH for bistable vibration energy harvesters

The present work focuses on ambient vibration energy harvesting. Specifically, this article deals with bistable piezoelectric energy harvesters (PEHs) which exhibits a wider bandwidth than linear oscillators. These complex systems require an energy extraction circuit (EEC) to rectify their voltage to supply power to autonomous sensors. This EEC needs to be optimized in order to increase the harvested power and even the bandwidth of PEHs. Because of the complex dynamics of bistable PEHs, there is a lack of simple and physically-insightful models in the literature that would allow the understanding and optimization of the extraction circuit. To address this issue, the present work derives closed-form models of a bistable PEH coupled to a passive and an active synchronous EEC: respectively the standard energy harvesting (SEH) circuit and the parallel synchronized switch harvesting on inductor (P-SSHI) circuit. Experimental measurements conducted on a custom bistable PEH demonstrate the validity of the proposed models with a relative error lower than 15% on the harvested power and the bandwidth. The proposed models allow to easily understand the influence of the P-SSHI circuit on the dynamics of a bistable PEH. Moreover, a comparison of the performance of the SEH and the P-SSHI circuits, valid for any bistable generator, is proposed. The latter shows that under low electromechanical coupling and low acceleration amplitude the P-SSHI circuit leads to multiply the maximum harvested power up to 4.3 compared to the SEH circuit, and the bandwidth by a factor of 2.3.

A Self-Powered Synchronous Switch Energy Extraction Circuit for Electromagnetic Energy Harvesting Enhancement

Previous studies have shown that the synchronous switch energy extraction (SSEE) solutions could enhance the energy harvesting capability of vibration energy harvesters with capacitive output impedance, such as piezoelectric ones. These circuits use a synchronous switch inductive branch to compensate for the capacitive source. Some studies have also shown that an inductive source can be compensated by a synchronous switch capacitive branch. Yet, the controls were all carried out by external bulky and power-hungry controllers, which is unrealistic in a self-contained and self-sustainable system. This paper proposes a self-powered SSEE (SP-SSEE) circuit for inductive electromagnetic energy harvesting (EMEH) sources. The sampling, synchronization, and switch control are implemented with a small series sampling inductor, a comparator, and some digital gates, respectively. The SSEE circuit carries out two rounds of the switch on/off actions in each vibration cycle to make the current through the induced equivalent voltage source in phase with its voltage. By improving the power factor of the induced voltage source, it enlarges the harvested power under the same excitation. It uses fewer switching actions than the conventional pulse-width modulation (PWM) ac-dc rectifier designs. Moreover, the self-powered design makes the SSEE solution a passive ac-dc rectifier, which is more convenient to be utilized in real applications. The detailed working principle and experimental validation of the SP-SSEE circuit are provided in this paper. The results show that, under the tested frequencies, SP-SSEE outperforms the benchmark standard energy harvesting (SEH) diode-bridge rectifier by 62.1% to 96.4% percent under different excitation frequencies, in terms of harvested power.

Mechanical Rectifier for Broadband Piezoelectric Vibration Energy Harvesting and Self-Adapting Synchronous Electric Charge Extraction

The synchronized switch interface circuit is believed to boost the piezoelectric power generation. The threshold voltage of electronic components causes rectification loss and delay of peak detection. This work reports a novel design of a mechanical rectification piezoelectric vibration energy harvester (MR-PVEH). Compact and low loss mechanical rectification is achieved by double switch with 5 electrodes contact at the cantilever tip. The switch as a mechanical stopper also contributes to broadband performance. The saturation voltage and response frequency range can be adjusted in modeling and simulation of nonlinear electromechanical coupling vibration. Self-adapting Mechanical rectification optimized synchronous electric charge extraction (M-OSECE) circuit is also proposed with less electronic components in this paper and shows an extra 60% increase in generated power than the traditional standard energy harvesting circuit (SEH) in test. This novel design gives a promising solution for self-adapting synchronous switching in broadband piezoelectric vibration energy harvesting.

A comprehensive analysis of piezoelectric energy harvesting from bridge vibrations

Piezoelectric energy harvesting from bridge vibrations has the potential to power wireless sensors used for bridge health monitoring. Often, it is necessary to store the harvested energy before it could be used to power the sensor intermittently. However, the behavior of the piezoelectric energy harvester (PEH) with nonlinear interface circuits for energy extraction and storage subject to realistic bridge vibrations has not been fully understood. This work performs a comprehensive analysis on the performance of the PEH subject to the measured railway bridge vibrations and compares the energy stored on a capacitor using four different interface circuits. Firstly, the dynamic characteristics of the railway bridge is analyzed. A cantilevered PEH is then designed and fabricated based on the dynamic characteristics of the bridge. Subsequently, four realistic energy extraction and storage interface circuits, namely, the standard energy harvesting (SEH), synchronized charge extraction (SCE), parallel synchronized switch harvesting on inductor (P-SSHI) and series SSHI (S-SSHI) circuits, are evaluated and compared when the PEH subject to the measured bridge vibrations. The influence of the storage capacitance and the 1st short-circuit natural frequency of the PEH on the stored energy with these four circuits is then discussed. An optimal storage capacitance exists in the systems based on SEH, P-SSHI and S-SSHI circuits. The system based on P-SSHI circuit has the highest efficiency on energy storage. This work provides a technical framework to develop the realistic energy harvesting and storage system for realization of self-powered bridge condition monitoring.

A Multistep Charge Extractions and Voltage Bias-Flip (MCEBF) Interface Circuit for Piezoelectric Energy Harvesting Enhancement

In piezoelectric energy harvesting (PEH), interface circuits using synchronous switch actions, including synchronized charge extraction (CE) and/or bias-flip (BF), can achieve much higher energy harvesting (EH) capability, compared with the standard energy harvesting (SEH) bridge rectifier. In this article, a multistep charge extraction and voltage bias-flip (MCEBF) interface circuit is proposed to further enhance the harvesting capability under weakly coupling conditions. The EH enhancement is realized by reducing the dissipation in CE with multiple CE actions and simultaneously enlarging the extracted energy with a BF action. MCEBF can also generate positive and negative voltage rails via buck-boost topology to supply power for double-rail devices. The optimal control method of MCEBF is theoretically derived. In our experiment, under constant deflection excitation, the best MCEBF case offers 487%, 95%, and 49% more harvested power, compared with SEH, synchronous electric charge extraction (SECE), and parallel synchronized switch harvesting on inductor (P-SSHI) interface circuits, respectively. MCEBF also keeps the benefit of load independence as SECE does under weakly coupling conditions.

Comparison of Four Electrical Interfacing Circuits in Frequency Up-Conversion Piezoelectric Energy Harvesting.

Efficiently scavenging piezoelectric vibration energy is attracting a lot of interest. One important type is the frequency up-conversion (FUC) energy harvester, in which a low-frequency beam (LFB) impacts a high-frequency beam (HFB). In this paper, four interface circuits, standard energy harvesting (SEH), self-powered synchronous electric charge extraction (SP-SECE), self-powered synchronized switch harvesting on inductor (SP-SSHI) and self-powered optimized SECE (SP-OSECE), are compared while rectifying the generated piezoelectric voltage. The efficiencies of the four circuits are firstly tested at constant displacement and further analyzed. Furthermore, the harvested power under FUC is tested for different electromechanical couplings and different load values. The results show that SP-OSECE performs best in the case of a weak coupling or low-load resistance, for which the maximum power can be 43% higher than that of SEH. As the coupling level increases, SP-SSHI becomes the most efficient circuit with a 31% higher maximum power compared to that of SEH. The reasons for the variations in each circuit with different coupling coefficients are also analyzed.

Analysis and optimization of self-powered parallel synchronized switch harvesting on inductor circuit for piezoelectric energy harvesting

Due to its strong environmental robustness and high energy density, piezoelectric energy harvesting is considered one of the most promising methods to power wireless sensor nodes under extreme conditions. The interface circuit is essential to a piezoelectric energy harvester to reduce internal energy dissipation, achieve impedance matching, and improve energy conversion efficiency. Existing researches show that a parallel synchronized switch harvesting on inductor (P-SSHI) interface circuit compared with a standard energy harvesting (SEH) circuit can significantly improve the output power. Therefore, this paper proposes a self-powered optimized PSSHI (SP-OPSSHI) circuit, which adopts a new peak detection switching circuit to replace the switches in the P-SSHI circuit. It can realize switch control without an external starting power supply, i.e. cold start. Compared with an existing self-powered PSSHI (SP-PSSHI) circuit, it can effectively eliminate the ‘second inversion’ phenomenon caused by the parasitic capacitors of transistors after the voltage inversion process. The cause and effect of ‘second inversion’ on energy harvesting are analyzed in this study. Then, the working principle and process of the optimized circuit are discussed, and energy harvesting under the ideal state is conducted. Finally, the SP-OPSSHI circuit is developed and tested. The experimental waveforms show that the SP-OPSSHI circuit compared with the SP-PSSHI circuit can significantly reduce the impact of parasitic capacitors in the energy harvesting process. The output performance of the SP-OPSSH circuit is tested with the variation of resistance. The experimental results indicate that the SP-OPSSHI circuit has an optimal load resistance of 350 kΩ, achieving a maximum harvested power being 2.91 times that of the SEH circuit.

An SSHC Interface Circuit for Energy Harvesting of Piezoelectric Flags

Piezoelectric flags have functions of both classic flags and energy harvesting, and are becoming a new research focus. Interface circuits that convert wind energy to electrical energy are the key component of piezoelectric flags. A new structure for piezoelectric flags was designed to generate vibration by wind induction. After theoretical analysis, only SEH (standard energy harvesting) and SSHC (synchronized switch-harvesting-on capacitors) interface circuits were found suitable for piezoelectric flags. Simulation in Multisim was performed to compare SEH and SSHC in different load resistance. Experiments were carried out using different wind speeds. The on-time and delay-time of each switch were controlled by the proposed control algorithm. Both simulation and experimental results indicate that the output voltage with SSHC is higher than the output voltage with SEH. When the resistance is 1700 kΩ and the wind speed is 24 m/s, the output power of SSHC can be increased by 45.63% compared with the SEH circuit.

Global optimisation approach for designing high-efficiency piezoelectric beam-based energy harvesting devices

The paper proposes a novel methodology for developing high-power energy harvesting gravity-based devices using an array of piezoelectric beams for wind energy applications. The methodology incorporates a global multidimensional constrained optimisation algorithm, which accounts for the physical size of the device, the physical, geometrical and electrical properties of the piezoelectric beams, and the power management circuit to increase the device’s efficiency. As the beams are plucked sequentially, they vibrate out-of-phase, which consequently leads to charge cancellation issues. The paper proposes and incorporates an electrical circuit design to avoid such problems, being able to further increase the efficiency of the device by 35% when compared against the output from the standard energy harvesting (SEH) circuit with independent rectifiers. The proposed optimisation methodology is applied to the devices utilising flexible polyvinylidene fluoride beams. The developed dynamic numerical model of the beams’ vibration is validated using the experimental results and the results of a Finite Element Analysis. To study the electro-mechanical coupling of the beams, an electric circuit and the power management circuit are created and modelled in Matlab/Simulink software. The optimised device delivers 6 to 17 times higher energy output compared to the unoptimised device. The performance of this device was also compared to that of the device with much stiffer LiNbO3 beams (Clementi et al., 2021, [1]) to demonstrate the direct applicability of such devices to power sensors and transmitter units for structural monitoring of wind turbine blades. It has been demonstrated that the LiNbO3-beam device yields an energy output with one order of magnitude higher. The applied optimisation methodology enabled a 0.057 × 0.017 × 2 m3 dimension device to produce a power output in the range from 0.5 to 1 W depending on the blades’ speed, resulting in 1.06 mW/cm3 power density of the device.

Investigations on energy harvesting systems incorporating mechanical and electrical nonlinearities to charge reusable batteries

This report analyzes the electromechanical coupling evident in vibration energy harvesting systems that charge reusable batteries. A model of a vibration energy harvesting system with far-from-equilibrium nonlinearities is considered for sake of capitalizing on high-energy forced vibrations. The piezoelectric structure is coupled with nonlinear interface circuits that leverage rectification and control stages to enhance power delivery to the battery. Three circuits, namely standard energy harvesting (SEH) circuit, parallel synchronized switching harvesting on inductor (P-SSHI) circuit, and synchronized charge extraction (SCE) are considered as interfaces between the nonlinear energy harvester and a battery. A simplified power calculation is numerically verified to accurately estimate the harvested power respectively delivered from three interface circuits to the battery. The investigations reveal that increasing required battery voltage may inhibit means to achieve high-energy vibrations and thus prevent battery charging. By a conservation of energy, it is shown that the phase lag between beam velocity and the base acceleration is the primary indicator of interference between dynamic energy flows in the electromechanical sub-systems. This research sheds light on the influences of energy storage components on the functioning of nonlinear vibration energy harvesting systems. Moreover, the principles uncovered for the inhibition of high-energy oscillation may guide future nonlinear energy harvesting system design to extract the best power out from the ambient vibration environments.

Synchronized switch piezoelectric energy harvesting using rotating magnetic ball and reed switches

Synchronized switch harvesting on inductor (SSHI) interface circuit has been developed to boost the harvesting capability of piezoelectric energy harvesters (PEHs). Although some electronic self-powered peak-detector and switching circuits have been proposed to support the practical realization of SSHI, the energy dissipation and voltage drops in transistors and diodes of the self-powered circuits might significantly deteriorate the actual energy harvesting performance. Some mechatronic designs were proposed as well. However, most of their switches are activated by touch impacts, which might introduce undesired high-order vibrations to the main structure. In this paper, rather than using the impact-engaged strategy discussed in the literature, a new mechanism using a magnetic ball for vibration synchronization and reed switches for switching operation is proposed. A PEH shunted to an SSHI interface circuit using the proposed mechatronic approach has been prototyped. Since the peak-detection and switching operations are completed by a mechanical mechanism, less passive electrical components, which consume extra energy, are required in our proposed design. Therefore, the overall energy harvesting performance is improved. Numerical simulations and experimental tests have validated the feasibility of the proposed design. The experimental results have shown that the power output produced by the proposed mechatronic self-powered SSHI design can be increased by and , as compared with the cases using a benchmark standard energy harvesting bridge rectifier and an electronic self-powered SSHI solutions, respectively. Moreover, owing to the new mechatronic design, the auxiliary mechanical components are embedded in the tip block of the cantilevered PEH, rendering the whole system to be a compact design.

Lumped Parameter Evaluation Model Analysis and Load Coupling Modeling of Piezoelectric Composite Cantilever Beam

In order to study the working mechanism of piezoelectric composite cantilever beam and improve the ability of predicting the power generation performance of piezoelectric composite cantilever vibration energy harvester (CVEH), the simple and high-precision analysis models of equivalent mass and equivalent stiffness of CVEH are proposed. The natural frequency method is used to compare the calculation results of the evaluation model, Rayleigh Ritz method and finite element simulation, and the results show that the consistency (Ω) between the evaluation model and the finite element simulation is more than 95%. The influence of the mass ratio (α) between the end mass of the beam and the weight of the beam itself on Ω is analyzed by using the proposed evaluation model, which shows that Ω increases with the increase of α, and the increase is more significant in the range of 0<α<4. The analysis of the influence of α on the natural frequency of the beam () shows that decreases with the increase of α, and the decrease is more obvious in the range of 0<α<2. According to the evaluation model, the electromechanical conversion analysis models of CVEH and its control equation with coupling of standard energy harvesting (SEH) interface circuit and Double synchronous switch harvesting (DSSH) interface circuit are established respectively, and the mathematical models of its output voltage are derived. The power generation experiment of CVEH is carried out, and the results show that the proposed models are in good agreement with the experimental results.

A self-powered ultra-low-power intermittent-control SSHI circuit for piezoelectric energy harvesting

PurposeExisting control circuits for piezoelectric energy harvesting (PEH) suffers from long startup time or high power consumption. This paper aims to design an ultra-low power control circuit that can harvest weak ambient vibrational energy on the order of several microwatts to power heavy loads such as wireless sensors.Design/methodology/approachA self-powered control circuit is proposed, functioning for very brief periods at the maximum power point, resulting in a low duty cycle. The circuit can start to function at low input power thresholds and can promptly achieve optimal operating conditions when cold-starting. The circuit is designed to be able to operate without stable DC power supply and powered by the piezoelectric transducers.FindingsWhen using the series-synchronized switch harvesting on inductor circuit with a large 1 mF energy storage capacitor, the proposed circuit can perform 322% better than the standard energy harvesting circuit in terms of energy harvested. This control circuit can also achieve an ultra-low consumption of 0.3 µW, as well as capable of cold-starting with input power as low as 5.78 µW.Originality/valueThe intermittent control strategy proposed in this paper can drastically reduce power consumption of the control circuit. Without dedicated cold-start modules and DC auxiliary supply, the circuit can achieve optimal efficiency within one input cycle, if the input signal is larger than voltage threshold. The proposed control strategy is especially favorable for harvesting energy from natural vibrations and can be a promising solution for other PEH circuits as well.

An SECE array of piezoelectric energy harvesting

The paper studies the electrical response of an array of piezoelectric oscillators attached to the synchronized electric charge extraction (SECE) interface circuit. The analytic estimate of output power is derived and presented through the matrix formulation of generalized Ohm’s law (charging on capacitance) for the case of parallel (series) connection of energy harvesters. These formulations mainly depend on the proposed equivalent load impedances which are independent of external resistive loads. It therefore offers an advantage of enabling harvested power independent of DC output voltage and making the harvester array desirable for broadband energy scavenging. The proposed framework is subsequently validated both numerically and experimentally. The results show that the power output and bandwidth of an SECE-based array are superior to that based on the standard energy harvesting circuit. Further, it is found that the behavior of an SECE array electrically arranged in parallel connection is different from that connected in series. The former demonstrates the output power higher than the latter, while the latter exhibits roughly uniform peak power in frequency response. However, the experiment indicates the unexpected power drop deviated significantly from the prediction in the array of harvesters connected in series. Such a discrepancy is explained as a result of comparatively serious leakage current in the reverse-biased diodes.

Enhanced piezoelectric energy harvesting power with thermoelectric energy assistance

The demand for life-time power supply in Internet of Things (IoT) nodes is a challenge issue. Piezoelectric energy harvesting (PEH) is expected to meet the demand by harvesting vibration energy and converting it into electricity for the IoT nodes. This article presents a novel PEH power improvement circuit with thermoelectric energy assistance. The proposed circuit can extract energy from thermoelectric generator (TEG) to assist the PEH. Simulation and experimental platforms are built for testing the power generation performance of the proposed circuit. With the thermoelectric assistance of 0.1 V and 0.2 V, the harvested power can reach 3.4 times and 4 times that of the standard energy harvesting (SEH) circuit when the piezoelectric transducer (PZT) original open circuit voltage Voc,org = 8 V, respectively. The harvested power can be increased by 13.3% and 33.3% with the thermoelectric assistance of 0.1 V and 0.2 V, respectively.

Self-Powered Multi-Input Serial SSHI Interface Circuit With Arbitrary Phase Difference for Piezoelectric Energy Harvesting

A self-powered multi-input serial synchronized switch harvesting on inductor (MIS-SSHI) interface circuit with arbitrary phase difference for piezoelectric energy harvesting is proposed in this article. The proposed MIS-SSHI can extract energy from multiple PZTs based on S-SSHI technique and handle inductor access conflict to avoid mutual influence between the PZTs, without using extra inductor access controlling circuit. Four cases of different phases between PZTs are discussed to explain how to handle the inductor access conflict. Besides, the diodes in traditional S-SSHI circuit are removed to improve the conversion efficiency. An experimental platform is built for testing the power generation performance of the proposed circuit. The experimental results show that the proposed MIS-SSHI circuit can harvest energy from two PZTs with arbitrary phase difference (0-2π) based on single inductor. The maximum harvested power of the proposed MIS-SSHI circuit for single PZT can reach 3.7 times that of the standard energy harvesting circuit.

Modeling, analysis and comparison of four charging interface circuits for piezoelectric energy harvesting

Four interface circuits have been widely studied in piezoelectric energy harvesting over the last two decades, namely, the standard energy harvesting (SEH) circuit, synchronized charge extraction (SCE) circuit, parallel synchronized switch harvesting on inductor (P-SSHI) circuit and series synchronized switch harvesting on inductor (S-SSHI) circuit. However, the abilities of these four circuits to charge storage capacitors are yet to be understood. This work focuses on the modeling and comparison of the charging process of these four circuits. First, the solutions of the voltage variations on the storage capacitors during charging process in each half-cycle are derived. Subsequently, the equivalent circuit model of the harvester interfaced with SEH and self-powered SCE, P-SSHI and S-SSHI circuits are implemented and simulated to validate the theoretical results. In the evaluation of the four circuits, different electromechanical coupling conditions of the PEH have been considered. The influence of the storage capacitance on charging performance are investigated. It is shown that for the SEH, P-SSHI or S-SSHI circuit, an optimal storage capacitor exists to maximize the accumulated energy and it varies with coupling condition. For a PEH with weak coupling, the P-SSHI circuits is suitable for energy charging. For the medium and strong coupling conditions, the SEH and S-SSHI circuits are more efficient as compared to the P-SSHI and SCE circuits.

Theoretical study and Simulation method for optimizing the performance of advanced Energy Harvesting techniques

This paper investigates and compares the efficiencies of four different interfaces for vibration based energy harvesting systems. In some cases, the increase in power was found to be in the order of ten times the output power compared to the standard approach to energy harvested by piezoelectric materials. The authors updated the review of synchronous switching techniques used in the conversion of ambient mechanical energy to useful electrical energy using piezoelectric materials is given. The basic concepts involved in the standard energy harvesting approach and synchronous switch harvesting techniques are presented. A comparative analysis of these techniques, highlighting the strengths and limitations of each approach in terms of power conversion efficiency, load independence, implementation complexity and adaptability for system applications are discussed.

A piezoelectric energy harvesting concept for an energy-autonomous instrumented total hip replacement

To improve the clinical outcome of total hip replacements (THRs), instrumented implants with sensory functions for implant monitoring and diagnostics or actuators for therapeutic measures are a promising approach. Therefore, an adequate energy source is needed. Batteries and external power supplies bring shortcomings e.g. limited lifetime or dependency on external equipment. Energy harvesting has the clear benefit of providing continuous and independent power for fully autonomous implants. Our present study evaluates by means of finite element analysis (FEA) the capabilities of a concept of a piezoelectric energy harvesting system (ring shaped multilayer piezoelectric element of 5 mm diameter and 2.5 mm height) integrated in a femoral hip stem. The deformations from a modified load-bearing implant are used to generate electric power for various instrumentation purposes. Besides the expected amount of converted energy, the influence on the stress distribution of the instrumented implant is analysed. The results show that the local stress increase for the modified implant geometry does not exceed the stress of the original reference model. The maximum generated open circuit voltage of 11.9 V can be processed in standard energy harvesting circuitry whereas an average power output amounts up to 8.1 µW. In order to increase the electric power in an upcoming design optimization, a sensitivity analysis is performed to identify the most important influencing parameters with regard to power output and implant safety.