Shaikh Faruque Ali

Current trend in energy harvesting research is to increase the operating bandwidth of energy harvesters. Multiple harvesters, nonlinear harvesters and hybrid harvesters are suggested to address the issue. In this paper, a system consisting of two electromagnetic harvesters with magnetic and mechanical couplings subjected to harmonic support excitations is proposed. Two pendulums with close resonating frequencies are used to generate power over a broad range of frequencies. The pendulums behave nonlinearly under the influence of magnetic interaction. This nonlinear motion harvests power at broader bandwidth. A mathematical model of the proposed harvester is established. Experiments are performed to validate the theoretical results. It has been observed that the nonlinear responses due to both magnet and mechanical couplings improve individual harvester performance. This is advantageous over harvesters that have magnetically coupling only. Additionally, the dynamics of harvesting system is numerically studied where large amplitude chaotic motion, quasi-periodic oscillations and periodic motions are observed and reported.

This manuscript discusses a magnetically coupled nonlinear hybrid piezo-electromagnetic energy harvester under harmonic base motion. Linear energy harvester works optimally when the natural frequency of the harvester meets the resonating frequency, elsewhere harvested power falls drastically. Most of the ambient vibration sources are random in nature. Hence, considering the realistic application, narrowband linear vibration energy harvesters are inefficient. Alternatively, nonlinear energy harvesters are capable of producing the electrical power over a broad frequency range. Hence, to acquire the optimum power in the broader frequency range, a magnetically coupled hybrid piezo-electromagnetic energy harvester is developed. In this current work, a tip loaded unimorph piezo cantilever beam configuration is used to scavenge electrical energy from the strain developed in the piezoelectric patch and spring-magnetic mass attached to another end of the cantilever beam with solenoid arrangements are used to scavenge electrical energy from the relative motion between magnetic mass and solenoid. This hybrid harvester is coupled with magnetic oscillators to introduces nonlinearity in the developed harvester. This paper compares, the energy harvested from the hybrid harvester with that of conventional piezoelectric and electromagnetic harvesters for both linear and nonlinear systems.

With the advent of technology miniaturization, portable electronic devices are evolving at a rapid pace, especially in the field of wireless sensor networks for IoT applications. On the contrary, battery technology has not seen a similar growth in miniaturization. Also, frequent replacement of batteries is challenging for devices located in remote places. Energy harvesting from ambient conditions may be one solution to the above challenges. The IoT and powering of portable devices are becoming increasingly popular among researchers working on structural health monitoring systems. Thermoelectric, piezoelectric, electromagnetic, electrostatic and triboelectric mechanisms are the major energy transduction methods adopted in the development of energy harvesting devices. Many of these devices have limitations including relatively low power density, narrow bandwidth and low efficiency at lower frequencies. The virtual International Conference on Advances in Energy Harvesting Technology (ICAEHT 2021, 18–20 March 2021) was organized to bring together researchers working on energy harvesting to discuss possible solutions to the above limitations and future directions. The content of this special issue was inspired from the contributions and discussions made during the ICAEHT 2021 and a few more from invited papers. The 19 selected papers cover thermoelectric, piezoelectric, electromagnetic and triboelectric energy harvesters. Modelling, analysis, optimization, control, experimentation, energy management and application aspects of the harvesters are covered in this special issue entitled “Energy harvesting: materials, structures and methods”. We hope that readers will find this special issue quite interesting, encouraging and novel.

In this research energy harvesting from near periodic structure is discussed. The near periodic system consists of two pendulums connected using a common linear spring. Mistuning in the simple coupled pendulum system is achieved by varying the length of one of the pendulums. Effect of this mistuning on amount of energy harvested is developed analytically and numerically. This will be discussed in this paper and at the same time effect of harvesting on mistuning will be presented. It is shown that with a proper electrical damping, optimal power can be obtained and effect of mistuning can be minimized. Same analysis is carried out with energy harvesting from both the pendulums. In case of harvesting from both the pendulums the harvesting bandwidth is increased and electrical damping required to minimize mistuning is more than that in case of harvesting with mistuned pendulum alone.

Multiple energy harvesters in a single device has become important to harvest enough power at wider frequencies for sensors. In such situation presence of magnetic force and mechanical coupling may change the performance of the overall system. This paper, studies a simple case of two pendulums in a same frame coupled magnetically and mechanically for electromagnetic broadband energy harvesting under low frequency excitation. The effect of mechanical coupling, frequency and distance between harvesters on bandwidth and magnitude of power are analyzed. The numerical analysis shows that the mechanical coupling with magnetic coupling increases the power magnitude and band width.

A low frequency magneto-mechanically coupled energy harvesting system is proposed to increase the power magnitude and bandwidth simultaneously. The system consists of two pendulums that are magnetically and mechanically coupled. The analytical formulation for the coupled system is developed based on the extended Lagrangian formulation. The experimental and simulated results are reported. The results exhibiting the benefits of magneto-mechanical coupling are reported. The experiments show an increment of 30.69% in the power magnitude and 100% enhancement in the bandwidth when compared to independent harvesters even at a low amplitude of excitation. Moreover, Chaos is observed at low frequency and at a low amplitude, which tends to provide larger bandwidths with more power.

Multiple energy harvesters in a single device has become important to harvest enough power for sensors. In such situation presence of mistuning may change the performance of the overall system. This paper studies the issue of presence of mistuning in such system and also extend the study to performance evaluation when mechanically coupling is present between the multiple harvesters. A simple case of two pendulums in a same frame is analysed for electromagnetic energy harvesting. Experiments are carried out to support the numerical evaluation. The study limits its observations to low frequency and low amplitude motions. The observation made are very interesting and intricate.

This article investigates an array of pendulums as a potential broadband energy harvester. Closed form expression of the total power is analytically obtained. Effect of parameters on the total power harvested and on frequency band of the harvested power is accessed numerically. Finally experiments are carried out for arrays with two to five pendulums, which strongly supports the numerical observations. Different configurations are studied; (a) pendulums in the array are independent of each other, (b) pendulums are coupled using springs in between. The effect of mechanical grounding, where in the extreme pendulums are connected to the support through a spring, is also investigated. Observations show that array of coupled pendulums with mechanical grounding increased the bandwidth of harvesting frequency. The bandwidth and the total power harvested saturates with the number of pendulums.

Energy harvesting has received a lot of attention in the recent past. At present a single device does not harvested energy enough to power up an electronic sensors. In order to increase the power output multiple identical harvesters are used. When multiple harvesters are used, they bring in non-uniformity in their physical parameters due to variability during manufacturing or even during deployment. Therefore, 'n' numbers of harvesters do not necessary produce 'n' times the harvested power of a single device. The variability in parameters is less enough to be coined as mistuning. In this paper, an analysis of multiple energy harvesters is studied. The harvesters are assumed to show mistuning. The study is further extended to understand the effect of mechanical coupling between the harvesters. For simplification, pendulums are considered as the harvesters, with magnetic tip masses for the electromagnetic energy harvesting. Mistuning is achieved by varying the length of the pendulums. A generalized mathematical model for n coupled harvesters with mistuning is developed. Simulations are performed with the number of harvesters varying from 2 to 6 with ±1% non-repetitive mistuning in the lengths of the harvesters, and a comparison of the power harvested between mechanically coupled and uncoupled harvesters is presented.

Dynamic vibration absorbers (DVAs) have proven to be an effective passive technique to suppress device vibration, with many realistic implementations in structures, buildings, and machines. Vibration energy harvesting is a process used to convert unwanted vibrations of a host structure into electrical energy. In this paper, a harmonic single degree-of-freedom system is considered consisting of a pendulum absorber and electromagnetic energy harvesting transduction mechanism. These types of DVAs are suitable for control of multi-story buildings, where for the simplicity of analysis a two degree-of-freedom system which models the building with the absorber is considered. Controlling the vibrations of buildings is the primary objective, and harvesting the energy from the dynamic vibration pendulum absorber at the same time is the secondary objective. Parametric analyses are performed. It is observed that proper system parameter selection is key for reducing the vibration amplitude of the primary system and for enhancing the energy harvested from the secondary system. Optimization analysis based on the genetic algorithm approach is used to optimize the system parameters. It is observed that with a proper selection of parameters, wideband energy can be harvested along with reduction in vibration of the building.