F. Travasso

A real vibration database for kinetic energy harvesting application

In this article, we discuss the project of a vibration signal database for energy harvesting purpose. After a brief description where we present the technologies used to create the database and the procedures to acquire the signals, we show some results obtained using selected environmental noises from the database to characterize nonlinear energy harvesters.

Breaking strength tests on silicon and sapphire bondings for gravitational wave detectors

The realization of third-generation gravitational wave interferometric detectors is under way. An important improvement in detector sensitivity can be obtained with the reduction of thermal noise by reaching a cryogenic stage. Two materials have been identified to perform efficiently at low temperatures: silicon and sapphire. In this work the breaking strength of the silicate bonding that glues cylinders of silicon (Si) and sapphire (Al2O3) has been investigated. All material combinations, flatness quality and orientations have been tested over time. Breaking strength between Si–Si and Si–Al2O3 shows a value similar to that of fused silica, while Al2O3–Al2O3 does not seem to be a promising combination.

Low-frequency internal friction in silica glass

Precise low-frequency internal friction measurements on vitreous silica, taken over a wide temperature (4 K 160 K the loss angle develops a distinct step-like structure followed by a plateau, both independent of ν, thus signalling the onset of a competing relaxation mechanism with much higher an activation energy. Copyright c EPLA, 2007

Mechanical quality factor of large mirror substrates for gravitational waves detectors

Thermal noise in the mirror substrates sets a most severe limit to the low-frequency sensitivity of the interferometric gravitational wave detectors presently under construction. The mechanical quality of the mirror substrates and the geometry of their suspension are shown to affect markedly the noise level of the detector output. High mechanical Q have been obtained for different large fused silica substrates under Virgo suspension conditions. Moreover, calcium fluoride substrates are shown to provide a more promising option for the design of future cryogenic, low thermal noise interferometers.

Nonlinear noise harvesters for nanosensors

Abstract The nanosensor network is an interesting technology that promises a wide range of applications in human life. Nowadays a sensor node is typically battery powered and should operate without attendance for a relatively long period of time. Usually it is very difficult, or even impossible to change or recharge batteries. Moreover batteries are not a feasible solution at the nanoscale. In this paper we present a green alternative to power nanosensors, which consists of harvesting energy from the environment. We focus our attention on piezoelectric harvester capable to convert random environmental vibrations into electrical power. In particular we present an alternative method to gather energy from a wide frequency range based on the exploitation of nonlinear dynamics to enhance power production with respect to traditional linear kinetic harvesters.

Cosmic-ray spectra near the LISA orbit

Cosmic-ray particles traverse the LISA apparatus charging the proof masses. This process causes spurious Coulomb forces between the test masses and the surrounding conducting surfaces mimicking gravitational wave signals. Approximately 13 g cm−2 of matter overlies the proof masses. The nucleonic component of cosmic rays (about 99% of the total) below 100 MeV/n stops inside the spacecraft without reaching the masses. It is of major importance to determine the primary and solar cosmic-ray particle fluxes above this energy near the LISA orbit in order to predict the effect on the apparatus.

Monocrystalline fibres for low thermal noise suspension in advanced gravitational wave detectors

Thermal noise in mirror suspension will be the most severe fundamental limit to the low-frequency sensitivity of future interferometric gravitational wave detectors. We propose a new type of materials to realize low thermal noise suspension in such detectors. Monocrystalline suspension fibres are good candidates both for cryogenic and for ambient temperature interferometers. Material characteristics and a production facility are described in this paper.

Nonlinear Kinetic Energy Harvesting

Abstract Harvesting of kinetic energy present in the form of random vibrations is an interesting option due to the almost universal presence of this kind of motion. Traditional generators based on piezoelectric effect are built with linear oscillators made by a piezoelectric beam and a mass used to tune the resonance frequency on the predominant frequency of the vibrations spectrum. However, in most cases the ambient random vibrations have their energy distributed over a wide spectrum of frequencies, being rich especially at low frequency. Furthermore frequency tuning is not always possible due to geometrical/dynamical constraints. In this work we present a different method based on the exploitation of the nonlinear dynamical features of bistable oscillator. The experimental results and the digital simulations show that nonlinear harvester (e.g. bistable oscillators) can overcome some of the most severe limitations of generators based on linear dynamics.

Vibration Energy Harvesting: Linear and Nonlinear Oscillator Approaches

An important question that must be addressed by any energy harvesting technology is related to the type of energy available (Paradiso et al., 2005; Roundy et al., 2003). Among the renewable energy sources, kinetic energy is undoubtedly the most widely studied for applications to the micro-energy generation1. Kinetic energy harvesting requires a transduction mechanism to generate electrical energy from motion. This can happen via a mechanical coupling between the moving body and a physical device that is capable of generating electricity in the form of an electric current or of a voltage difference. In other words a kinetic energy harvester consists of a mechanical moving device that converts displacement into electric charge separation.

Hybrid autonomous transceivers

A small photocell and a non-linear vibration energy harvester have been used to power a low power wireless transceiver device. The device, a technology demonstrator, is self-powered and works without any battery on board. It is able to transmit at few meters distance data such as the temperature and the power supply voltage values in the 2,4 GHz ISM band every 10 seconds.