Attilio Di Nisio

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.

Feasibility of a Photovoltaic–Thermoelectric Generator: Performance Analysis and Simulation Results

This paper describes a theoretical approach to evaluate the performance of a hybrid solar system made with photovoltaic cells and thermoelectric (TE) modules. After a brief treatment of the integrated system, energy conversion and performance parameters are evaluated through numerical simulations depending on the global radiation and temperature distribution obtained by the Joint Research Center of the European Commission and of the National Renewable Energy Laboratory. The contribution of TE module to total energy seems significant in southern European towns and less substantial when the locations considered are very distant from the equator and show the possibility of using TE devices for energy production.

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.

An online defects inspection system for satin glass based on machine vision

Today, quality control is a nodal point in many industries, and in the glass one in particular; in most cases the human control does not catch up with the pressing market requirements, therefore computer vision inspection systems are preferable to reduce costs and to improve the product quality, but several problems must be solved. In this paper a prototype system, able to reproduce all the functionalities of an automatic glass inspection system, is designed and realized; it guarantees good results and considerable reliability with low incidence on manufacturing costs. The final in-line computer vision system is under development in cooperation with a specialized electronic industry.

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.

Measuring Time Base Distortion in Analog-Memory Sampling Digitizers

High-frequency digital oscilloscopes are often prone to systematic errors in sampling time or time base distortion (TBD). This error greatly affects the quality of the acquisition of fast signals, but its systematic nature makes measurement and correction possible and greatly advantageous. Existing techniques for measuring TBD exhibit good performance with equivalent-time sampling digitizers, but they are not able to measure the distortion in real-time analog-memory systems - a technology of widespread use in modern gigasamples/second sampling scopes. This paper illustrates the correct measurement technique that was developed according to the hardware peculiarities of analog-memory sampling digitizers. The performance of the developed techniques are theoretically evaluated and practically demonstrated in the experimental characterization of an actual real-time analog-memory scope.

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.

Dose Optimization in Chest Radiography: System and Model Characterization via Experimental Investigation

The main purpose of this paper is to analyze the digital radiographic methodologies used in diagnostic investigation, in order to reduce radiation doses to the patients by assuring a good quality of the images. To this end, the main parameters influencing the absorbed dose during radiographic exams and the effect of the human body on X-ray attenuation were investigated. It is generally understood that radiographic techniques need an appropriate choice of the operative parameters as functions of patients characteristics, with the aim of providing the minimum dose that is compatible with an image that satisfies the goal of the examination and has a good signal-to-noise ratio. In an effort to identify an optimized radiographic protocol, the correlation between body size and radiation dose was investigated.

Maximum likelihood estimation for linearity testing of ADCs stimulated by known constant signals

A maximum likelihood (ML) estimator is derived for the problem of measuring the code transition levels of an analog-to-digital converter (ADC). The proposed method is intended to test the linearity of the ADC in the static regime, using only constant test signals, except for a small amount of additive noise. The measurement data are employed in a nearly optimal manner, due to the statistical properties of the ML estimator, which are thoroughly examined. The reported analysis allows the design of the test under a given uncertainty constraint.

Loop-back linearity test of ADCs and DACs

A loop-back test is illustrated, where the outputs of a DAC are dithered by additive noise and digitized by an ADC. The samples are collected in a code occurrences table, which allows the measurement of the input/outputs characteristics of both the ADC and the DAC. The method is particularly suited for implementing self-calibration strategies. The measurement is performed by means of maximum likelihood estimation and is therefore statistically nearly optimal. After a description of the method, experimental data are illustrated for validating the proposed linearity test.