Luigi Costanzo

Closed-form analysis of Switchless Electrostatic Vibration Energy Harvesters

Batteries drawbacks are represented by the high cost, the limited reliability and the frequent maintenance requirements (recharge or replacement). Energy Harvesting (EH) offers an alternative to batteries replacement or, at least it allows the increase of their lifetime. EH is the conversion of ambient energy, which is present in the environment, into electrical energy. Different energy sources for EH applications have been reported in the literature: light, radio frequency (RF), temperature gradients, solar energy, vibrations. In this paper we will focus on vibration EH. In a Vibration Energy Harvester (VEH) electrical energy is generated by allowing an inertial mass to vibrate with respect to a frame. In this paper a closed-form analysis of the model of a single-degree of freedom Out-of-Plane Switchless Electrostatic Vibration Energy Harvester (SEVEH) will be presented and discussed. We will demonstrate that, under suitable reasonable assumptions, it is possible to study SEVEHs by using models that admit closed form solutions and, at the same time, are enough accurate if the simplifying hypothesis are met. In particular, a circuital model will be developed which describes both the mechanical and the electrical subsystems composing a SEVEH.

Identification of the parameters of the equivalent electric circuit of electromagnetic harvesters

This paper concerns electromagnetic vibration energy harvesters. The knowledge of the equivalent electric circuit of electromagnetic harvesters is a fundamental need in order to be able to carry out numerical simulations of electromagnetic vibration harvesters. The aim of this paper is the description of a suitable procedure leading to the determination of the parameters of such an equivalent electric circuit. In fact, while in the case of the laboratory harvesters which are presented and discussed in the scientific literature such parameters are usually known, in the case of commercial devices instead such parameters must be extracted from the typical information which can be usually found in the manufacturers data sheet.

Multi-objective optimization of PV arrays performances by means of the dynamical reconfiguration of PV modules connections

Mismatching operating conditions (due to clouds, shading, non-uniform aging, manufacturing tolerances, etc.) strongly limit the energetic efficiency and the reliability of PV plants. The dynamical re-configuration of PV modules represents a promising solution in order to mitigate the drawbacks associated to mismatching phenomena. The goal of this paper is just to prove that, by using the dynamical reconfiguration of PV modules, it is possible to find configurations which allow to get a suitable compromise between energetic efficiency and reliability. In particular, in this paper, the expression of a suitable Objective Function whose maximization allows to get the required compromise between energetic efficiency and amplitude of thermal stresses (due to bypass diode conduction and/or reverse biasing of shaded cells) is introduced and discussed.

Resonant electromagnetic vibration harvesters feeding sensor nodes for real-time diagnostics and monitoring in railway vehicles for goods transportation: A numerical-experimental analysis

In this paper, the results of a combined numerical-experimental analysis on a system, part of a wireless sensor network, composed by a resonant electromagnetic energy harvester, a suitable power electronic interface and a sensor node are presented and discussed. Such a system is to be used onboard for real-time diagnostics and monitoring in railway vehicles for goods transportation.

Resonant electromagnetic vibration energy harvesters: The harvester ideal utilization factor

In this paper an important figure of merit is introduced and discussed with reference to electromagnetic vibration energy harvesters which are loaded by diode bridge rectifiers. It is called Harvester Ideal Utilization Factor. It precisely quantifies how close to the optimum the harvester is loaded. Such a figure of merit can be defined not only for electromagnetic but also for piezoelectric harvesters as long as the assumptions which allow the modeling of such vibration harvesters by means of an equivalent linear electric circuit are valid.

Experimental analysis of mechanical vibrations and wind speed for a rail vehicle WSN fed by energy harvesters

Real-time diagnostic and monitoring on railway vehicles for goods transportation is considered. The results of a preliminary experimental activity aimed to model mechanical vibrations and wind speed for autonomous monitoring and diagnostic wireless sensor network fed by means of energy harvesters are reported and commented.

MPPT in Wireless Sensor Nodes Supply Systems Based on Electromagnetic Vibration Harvesters for Freight Wagons Applications

The starting point for the proper design of an efficient wireless sensor node (WSN) supply system that is based on the adoption of a resonant electromagnetic vibration energy harvester (REVEH) is represented by the choice of a REVEH with a proper resonance frequency. But further likewise important design guidelines need to be also taken into account especially if, as in the case of freight wagons applications, vibrations are nonsinusoidal and their characteristics change with time. In this paper, the guidelines leading to the development of a smart power electronics interface between the REVEH and the WSN are provided with reference to freight wagons applications. In particular, for the most widely used double stage ac/dc architecture for REVEH applications, such guidelines not only allow the choice of the proper dc/dc converter topology, but they also allow the development of a suitable maximum power point tracking control strategy that allows to avoid the waste of energy and the consequent necessity to oversize the REVEH.

Modified TEODI MPPT Technique: Theoretical Analysis and Experimental Validation in Uniform and Mismatching Conditions

In this paper, the theoretical analysis and the experimental validation of a modified version of the maximum power point tracking technique, that is known with the acronym TEODI, are presented and discussed. The modified version of TEODI (MTEODI) outperforms TEODI in photovoltaic (PV) applications operating under mismatching conditions. The working principle of MTEODI is based on the periodic measurement of the short-circuit currents of the PV units. The knowledge of such currents allows not only the determination of whether mismatching conditions occur but identification of the values of the suitable correction factors, on which the working of MTEODI is based, as well.

Optimization of both the energetic efficiency and the duration of life of PV arrays by means of the dynamical reconfiguration of PV modules connections

In mismatching operating conditions (due to clouds, shadows, soiling from dust, debris, manufacturing tolerances, non-uniform aging, different orientation of parts of the PV field, etc.) the energetic efficiency and the reliability of the Photovoltaic (PV) systems are strongly compromised. A possible solution adopt to mitigate the negative effects of the occurrence of mismatching conditions is represented by the dynamical reconfiguration of PV modules in the PV field. The goal of this paper is to demonstrate that, by using the dynamical reconfiguration of PV modules, it is possible to find a configuration which represent a suitable compromise between efficiency and reliability. Further work is needed and is in progress in order to design suitable re-configuration algorithms able to identify such compromise configurations.

Dual implementation of the MPPT technique TEODI: Uniform and mismatching operating conditions

In this paper the dual implementation of the MPPT technique TEODI is presented and discussed. Such a new technique will be called D-TEODI. As well as TEODI, also D-TEODI is suitable for DMPPT PV applications. Its main advantages, as for TEODI, are the simplicity of implementation, the absence of memory and multiplication operations, and the high MPPT efficiency obtainable when the PV modules belonging to the same TEODI Building Block operate in the same atmospheric conditions (absence of mismatching conditions). In order to obtain a technique which is efficient also when mismatching events occur, a proper modification of D-TEODI is necessary. The modified version of D-TEODI will be called MD-TEODI. MD-TEODI is based on the periodic measurement of the short circuit currents of the PV modules. The knowledge of such currents allows not only to determine if mismatching conditions have occurred, but also to identify a suitable correction factor k on which the working of MD-TEODI is based. The results of numerical simulations fully confirm the validity of MD-TEODI.