Emmanuelle Arroyo

Energy harvesting from ambient vibrations: Electromagnetic device and synchronous extraction circuit

This article presents the design and experimental test of a new electromagnetic generator optimized for vibration energy harvesting with a nonlinear energy extraction circuit (synchronized magnetic flux extraction circuit). Previous results showed that the synchronized magnetic flux extraction circuit allows the rectification and the amplification of the voltages produced by an electromagnetic transducer, as well as the optimization of the energy transfer independently of the load impedance. A new geometry of electromagnetic harvester is proposed and optimized to harvest the maximum energy with the synchronized magnetic flux extraction circuit. The studied structure, whose total volume is 10 cm3, is based on a closed ferromagnetic back iron in order to obtain a high reactance in comparison with its resistance. Experimental measurements show that with the synchronized magnetic flux extraction technique, a rectified power of 1.6 mW is harvested at 1 g, 100 Hz over a 10 Hz bandwidth.

Experimental and Theoretical Study of a Piezoelectric Vibration Energy Harvester Under High Temperature

This paper focuses on studying the effect of increasing the ambient temperature up to 160 °C on the power harvested by an MEMS piezoelectric micro-cantilever manufactured using an aluminum nitride-on-silicon fabrication process. An experimental study shows that the peak output power decreases by 60% to 70% depending on the input acceleration. A theoretical study establishes the relationship of all important parameters with temperature and includes them into a temperature-dependent model. This model shows that around 50% of the power drop can be explained by a decreasing quality factor, and that thermal stresses account for around 30% of this decrease. [2017-0071]

Utilising Nonlinear Air Damping as a Soft Mechanical Stopper for MEMS Vibration Energy Harvesting

This paper reports on the theory and experimental verification of utilising air damping as a soft stopper mechanism for piezoelectric vibration energy harvesting to enhance shock resistance. Experiments to characterise device responsiveness under various vibration conditions were performed at different air pressure levels, and a dimensionless model was constructed with nonlinear damping terms included to model PVEH response. The relationship between the quadratic damping coefficient ζ n and air pressure is empirically established, and an optimal pressure level is calculated to trade off harvestable energy and device robustness for specific environmental conditions.

High temperature performance of a piezoelectric micro cantilever for vibration energy harvesting

Energy harvesters withstanding high temperatures could provide potentially unlimited energy to sensor nodes placed in harsh environments, where manual maintenance is difficult and costly. Experimental results on a classical microcantilever show a 67% drop of the maximum power when the temperature is increased up to 160 °C. This decrease is investigated using a lumped-parameters model which takes into account variations in material parameters with temperature, damping increase and thermal stresses induced by mismatched thermal coefficients in a composite cantilever. The model allows a description of the maximum power evolution as a function of temperature and input acceleration. Simulation results further show that an increase in damping and the apparition of thermal stresses are contributing to the power drop at 59% and 13% respectively.

Interdigitated cantilever array topology for low frequency MEMS vibration energy harvesting

© Published under licence by IOP Publishing Ltd. Micro-fabricated vibration energy harvesters enable merits such as miniaturisation, economies of scale for manufacturing, and ease of integration with semiconductor IC technologies. However, the frequency range of ambient vibration is generally low (10s Hz to 100s Hz). Existing MEMS vibration energy harvesters that target these frequencies typically are in the centimetre scale range. This sacrifices the miniaturisation aspect as well as introducing new challenges in packaging and integration for the unconventionally large MEMS devices. This paper proposes a new interdigitated fork cantilever array topology, which allows for up to about a third reduction in resonant frequency compared to the classical cantilever topology, for the same design area and without compromising on power optimisation. Further resonant frequency reduction is also possible, but at the expense of power optimisation. This opens up design flexibility to achieve low frequency MEMS resonators that are more suitable to practically target ambient vibration, without sacrificing the aforementioned merits of MEMS technology.

Rectified Output Power Analysis of Piezoelectric Energy Harvester Arrays under Noisy Excitation

© Published under licence by IOP Publishing Ltd. In the past decade, vibration energy harvesting has emerged as a potential alternative solution to power wireless sensor nodes. In real-world implementations, external excitation can be very noisy and includes noise signals in a wide frequency band. In order to accommodate operation under noisy excitation, arrays of energy harvesters with different resonance frequencies are often employed to improve responsibility. Due to the nature of noisy excitation and the difference in resonance frequencies, the response voltage signals from each harvester can be very different in amplitude, frequency and phase. In this paper, an array with two cantilevered energy harvesters is studied to analyze the rectified output power with different configurations using full-bridge rectifiers (FBR). The experiments show that connecting the two harvesters in parallel or in series before connecting with a FBR results in significant voltage cancellation due to phase mismatch. The most efficient way to extract energy is to use two FBRs for the two cantilevered energy harvesters, individually, and charge to one single storage capacitor connected at the outputs of the two FBRs.

Energy neutral operation of vibration energy-harvesting sensor networks for bridge applications.

Structural monitoring of critical bridge structures can greatly benefit from the use of wireless sensor networks (WSNs), however energy harvesting for the operation of the network remains a challenge in this setting. While solar and wind power are possible and credible solutions to energy generation, the need for positioning sensor nodes in shaded and sheltered locations, e.g., under a bridge deck, is also often precluding their adoption in real-world deployments. In some scenarios vibration energy harvesting has been shown as an effective solution, instead.This paper presents a multihop vibration energy-harvesting WSN system for bridge applications. The system relies on an ultra-low power wireless sensor node, driven by a novel vibration based energy-harvesting technology. We use a receiver-initiated routing protocol to enable energy-efficient and reliable connectivity between nodes with different energy charging capabilities. By combining real vibration data with an experimentally validated model of the vibration energy harvester, a hardware model, and the COOJA simulator, we develop a framework to conduct realistic and repeatable experiments to evaluate the system before on-site deployment.Simulation results show that the system is able to maintain energy neutral operation, preserving energy with careful management of sleep and communication times. We also validate the system through a laboratory experiment on real hardware against real vibration data collected from a bridge. Besides providing general guidelines and considerations for the development of vibration energy-harvesting systems for bridge applications, this work highlights the limitations of the energy budget made available by traffic-induced vibrations, which clearly shrink the applicability of vibration energy-harvesting technology for WSNs to low traffic applications.

A micromachined device describing over a hundred orders of parametric resonance

The following article appeared in Jia, Y., Du, S., Arroyo, E., & Seshia, A. A. (2018). A micromachined device describing over a hundred orders of parametric resonance. Applied Physics Letters, 112, 171901. https://doi.org/10.1063/1.5024667 and may be found at https://aip.scitation.org/doi/10.1063/1.5024667. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.

Connection Configurations to Increase Operational Range and Output Power of Piezoelectric MEMS Vibration Energy Harvesters

Among the various methods of extracting energy harvested by a piezoelectric vibration energy harvester, full-bridge rectifiers (FBR) are widely employed due to its simplicity and stability. However, its efficiency and operational range are limited due to a threshold voltage that the open-circuit voltage generated from the piezoelectric transducer (PT) must attain prior to any energy extraction. This voltage linearly depends on the output voltage of the FBR and the forward voltage drop of diodes and the nature of the interface can significantly limit the amount of extracted energy under low excitation levels. In this paper, a passive scheme is proposed to split the electrode of a micromachined PT into multiple (n) equal regions, which are electrically connected in series. The power output from such a series connected MEMS PT allows for the generated voltage to readily overcome the threshold set by the FBR. Theoretical calculations have been performed in this paper to assess the performance for different series stages (n values) and the theory has been experimentally validated. The results show that a PT with more series stages (high n values) improves the efficiency of energy extraction relative to the case with fewer series-connected stages under weak excitation levels.