Maurizio Spadavecchia

Characterization and Testing of a Tool for Photovoltaic Panel Modeling

This paper presents the evaluation of the performance, in terms of uncertainty, of a tool designed to estimate the main parameters of a model of a photovoltaic panel (PVP) under real and/or simulated working conditions. The presented tool permits the characterization of the panel, and it is useful to predict its behavior in whatever working condition; in this way, it is possible to compare the actual and expected performance to prevent any decrease in the output power, so permitting the replacement of the monitored module before it goes out of order or its efficiency falls under a given threshold. The well-known two-diode model is used to estimate the parameters of the electrical equivalent circuit of the PVP and to simulate the I -V and P-V characteristic curves in any given environmental condition of irradiance and/or temperature. The model and the estimation algorithm are implemented with MATLAB functions, whereas data acquisition and result presentation are managed by a LabVIEW graphics user interface. The presented tool has been validated against an experimentally characterized PVP. The environmental parameters of the model such as irradiance and temperature have been set (with their respective uncertainties) during simulations or directly measured during the outdoor tests, whereas the others parameters have been evaluated using a best-fit algorithm on the measured data. The estimation is based on the minimization of a new objective function and on a modified expression of the model resistances, which differ from those mentioned in the available literature. After a review of the state of the art, this paper provides the description of the estimation technique and its validation by means of simulations and experiments. Some results are also provided to illustrate the performance of the proposed test method.

Uncertainty Analysis in Photovoltaic Cell Parameter Estimation

This paper describes a theoretical approach to evaluate the uncertainty on the series and shunt resistances estimated by the seven-parameter (double diode) model of a photovoltaic (PV) cell using data commonly provided by panel manufacturers, measured environmental parameters, and semiempirical equations. After a brief survey on the state of the art and the treatment of the double-diode model, the procedure proposed by the authors, to estimate the unknown parameters, is illustrated. The theoretical expression of the uncertainty, which affects the estimation of the series and shunt resistances (namely, and ) of a PV cell, is then derived. A statistical analysis performed by means of a Monte Carlo simulation is in agreement with the theoretical expression of the uncertainty.

A Technique to Improve the Image Quality in Computer Tomography

The purpose of this paper is to assess the effect of different noise reduction filters on computed tomography (CT) images. In particular, denoising filters based on the combination of Gaussian and Prewitt operators and on anisotropic diffusion are proposed. Simulation results show that the proposed techniques increase the image quality and allow the use of a low-dose CT protocol.

Channel Characterization of an Open Source Energy Meter

In this paper, a prototype of an energy monitoring device based on an open source concept is presented. This architecture assures several advantages with respect to traditional energy meters, such as easy development of new applications making cost- and time-effective the migration to future smart grid infrastructures and simple adjustments to change in the relevant standards. The open source philosophy has been adopted designing the software components to make all features easily customizable by the user. In this paper, the characterization of the acquisition channels using measurement data obtained stimulating them with signals generated using a high-accuracy waveform generation module is presented.

A tool for Photovoltaic panels modeling and testing

This paper presents the results obtained testing a tool designed to characterize and simulate the behavior of a Photovoltaic (PV) panel under real and/or simulated working conditions. The presented tool permits the continuous monitoring of the I-V (Current-Voltage) and P-V (Power-Voltage) characteristics of the panel and the comparison between actual and expected performance; in this way it is possible to prevent any possible decrease of the output power and to replace the monitored module before it goes out of order or its efficiency falls under a given threshold.

Analysis of the uncertainty of the double-diode model of a photovoltaic panel

In this paper the theoretical expression of the uncertainty, which affects the estimation of the series and shunt resistances (namely Rs and Rsh) of a Photovoltaic cell, is derived. After a brief treatment about the double diode model, the new procedure to estimate the unknown parameters proposed by the authors is illustrated. Numerical results and a first discussion about the biases and standard deviations of Rs and Rsh estimators in a wide range of environmental conditions are given.

Fast Thermal Characterization of Thermoelectric Modules Using Infrared Camera

Thermoelectric modules are receiving more and more attention due to the increasing interest in the energy harvesting sector. The selection of the proper module for a particular application can be done comparing the values of the figure of merit, which depend on electrical parameters such as internal electrical resistance and Seebeck voltage, and the equivalent thermal resistance. Despite its importance, thermal resistance is more difficult to estimate than other parameters, as a well-engineered experimental setup is usually needed. In this paper, a new, fast, and noninvasive method based on thermal imaging techniques, to estimate the thermal resistance of thermoelectric modules, is presented. The comparison between this method and a direct measurement method based on thermocouple probes shows that very similar performance, with a small relative error, is achieved quicker, also avoiding to implement a complex measurement setup involving many temperature probes. Moreover, due to the contactless nature of the procedure, the proposed experimental setup can be easily tuned for modules of different sizes without the need to modify any mechanical part.

High Dynamic Range Power Consumption Measurement in Microcontroller-Based Applications

This paper proposes an innovative method for power consumption measurement in microcontroller-based systems that provides high accuracy on a wide dynamic range of current values, which makes it particularly suitable for all those applications characterized by alternating low-/high-power modes and fast current variations. We demonstrate that using an op-amp-based voltage feedback configuration, it is possible to use shunt resistor values higher than usual to obtain increased voltage drops without affecting the microcontrollers power supply voltage. Consequently, it is possible to directly use a data acquisition board to acquire the shunt voltage, eliminating all those common errors, like offset and gain, due to the use of an additional intermediate amplification stage. The proposed scheme has been successfully used to accurately characterize the power consumption of a single sensor node of a wireless sensor network.

Design of a low cost multipurpose wireless sensor network

This paper proposes the implementation of a low-cost and reliable multipurpose wireless sensor network framework. It has been designed to be easily customizable in order to adapt it to the particular application.

A proposal for an open source energy meter

This paper describes the design and the implementation of a prototype for an Alternating Current (AC) energy monitoring device based on an open source concept. The measurement device aims to provide a remote monitoring interface useful for three-phase and single-phase AC power systems. The open-source philosophy has been adopted designing the software components in order to make all features easily customizable by the user. In this way one can easily develop new applications making cost- and time-effective the migration to future smart grid infrastructures.