Lorenzo Ciani

FMECA technique on photovoltaic module

The solar photovoltaic industry has seen rapid expansion in the past decade with an ever-increasing share of the electricity-generating capacity for the world. For the emerging photovoltaic (PV) industry the assessment of the quality and reliability of its products is becoming more and more important. To this aim and to ensure an optimal design and material choice, a failure modes, effects and criticality analysis methodology (FMECA) to classify the occurrence, the severity and the impact of all possible failure mechanisms on the PV system has been introduced. This helps to eliminate or reduce the impact of potential failure modes before the completion of the design and before failures occur in the field. By means of this analysis it can be noticed that a crucial aspect in PV systems is the cleaning status of the panel surface. In this paper this problem has been analyzed by means of an experimental activity. Finally a method for the assessment of the PV panel condition has been proposed.

A simplified procedure for the analysis of Safety Instrumented Systems in the process industry application

Abstract International Standards and Guidelines propose qualitative and quantitative methodologies for the safety assessment of the Safety Instrumented System (SIS). However, some of these methodologies are often complex and not very easy to apply. In fact, some criticalities are found by technicians voted to the functional safety such as the study of SIS for complex architectures, calculation of safety parameters, difficulties in the identification of the SIS subsystem during the design review to guarantee the safety requirements, and so on. The aim of this paper is to propose a simplified and more efficient methodology for safety assessment of electromechanical SIS in compliance with the Standards IEC 61508 and IEC 61511. The proposed technique is based on an alternative implementation of the Reliability Block Diagram (RBD) approach for the performance analysis of the Safety Instrumented System. In order to demonstrate the advantages of the proposal, a case study of some of the safety functions is considered. With respect to other methodologies normally used for safety analysis, the results proved the proposed approach both easier in the application and time-saving. In addition, such results are comparatively close to those obtained by using the Standard methods.

The FMEDA approach to improve the safety assessment according to the IEC61508

According to the Standard IEC61508, the paper presents a case study concerning the evaluation of both the safe failure fraction (SFF) and the probability of failure on demand (PFD) for a complex system. After a preliminary presentation of the criteria for the safety integrity level (SIL) verification, the work focuses the attention on the method to achieve the PFD. In particular, an approach based on failure modes, effects and diagnostic analysis (FMEDA) is proposed and then a comparison with the approach described in the Standard. The paper aims to clarify both the knowledge and the application of the IEC61508 and proposes a technique to satisfy the hardware safety integrity requirements.

Design and implementation of a on-board device for photovoltaic panels monitoring

Nowadays the world energy infrastructure is subjected to a progressive transformation. In fact it is already possible to notice the growing number of distributed small generation units, based on different technologies, directly connected to the power grid. At present the energy that can be produced by the sun and wind seem to be the most promising renewable energy sources. The use of the solar energy requires to optimize the efficiency of the converting chain and to maintain the performances of the system. These requirements highlight the need to equip photovoltaic (PV) plants with efficient condition monitoring tools. In this paper a hardware solution for monitoring system that allows implementing algorithm devoted to check the dependability of the PV panels and to improve the overall system efficiency is presented.

Economical evaluation of PV system losses due to the dust and pollution

The continuously increasing number of Photovoltaic (PV) plants has stimulated the research in order to increment their overall efficiency. Usually, the efforts have been focused on the research of innovative materials and in general on the optimization of the photovoltaic conversion. Pollution due to the traffic, to the industrial activities or to the residential heating can reduce the efficiency of the PV plant. However, this phenomenon has been rarely investigated. It is important to highlight that these losses may have a significant impact in PV module and plant performances thus reducing the financial incomes in a nonnegligible way. This paper present and discuss a method which allows to choose the optimal maintenance interval for a PV plant. The method, starting from the costs related to the cleaning of the panels, compares them to the economic losses due to the decrease of the efficiency.

Ultracapacitor Degradation State Diagnosis via Electrochemical Impedance Spectroscopy

In this paper, we propose the use of the electrochemical impedance spectroscopy technique for state diagnosis of electric double-layer ultracapacitors. Ultracapacitors under investigation are Maxwell BCAP 0350 and they were stressed in several ways for our study. The analyzed stress conditions include accelerated aging tests, overvoltage, and over temperature tests. Chemical and physical effects on supercapacitor materials are pointed out through a morphologic analysis implemented by means of an environmental scanning electron microscope and a chemical composition analysis obtained by means of an energy dispersive spectrometer. Consequent degradation effects are described in terms of frequency behavior of equivalent circuital parameters.

Software automated testing: A solution to maximize the test plan coverage and to increase software reliability and quality in use

Software plays an increasingly important role in complex systems, especially for high-tech applications involved in important fields, such as transportation, financial management, communication, biomedical applications and so on. For these systems, performances such as efficient operation, fault tolerance, safety and security have to be guaranteed by the software structure, whose quality in use is assuming a growing importance from the industrial point of view. The basic problem is that the complexity of the task which software has to perform has often grown more quickly than hardware. In addition, unlike hardware, software cannot break or wear out, but can fail during its life cycle (dynamic defects) [1]. Software problems, essentially, have to be solved with quality assurance tools such as configuration management, testing procedures, quality data reporting systems and so on [2]. In this context, the paper proposes a new approach concerning the automated software testing as an aid to maximize the test plan coverage within the time available and also to increase software reliability and quality in use [3]. In this paper a method which combines accelerated automated tests for the study of software regression and memory overflow will be shown, in order to guarantee software with both a high quality level and a decrease of the testing time. The software will be tested by using test sequences reproducing the actual operating conditions and accelerated stress level. Moreover the research wishes to define some parameters of the software life and to show the generality of the proposed technique.

Experimental tests and reliability assessment of electronic ballast system

Abstract The necessity of clean energy resources development has increasingly become the focus of attention of the world. An important contribution to this topic could be given by minor waste in the illumination system. This paper presents results obtained by qualification tests implemented on electronic ballasts, with particular attention to on/off, thermal tests and EMC tests. Being the device under test an innovative electronic power supply system designed for application in energy saving, it is fundamental also an evaluation and analysis of the reliability performances. To this aim some results obtained with reliability prediction method are also presented in the paper.

A Novel Approach To Automated Testing To Increase Software Reliability

Software plays an increasingly important role in equipment and systems, both in terms of technical relevance and of development cost (often higher than 50% even for small systems). Unlike HW, SW does not go through a production phase. Also, SW cannot break or wear out. However, it can fail to satisfy its required function because of defects which manifest themselves while the system is operating (dynamic defects). A fault in the SW is thus caused by a defect, even if appears randomly in time, and SW problems are basically quality problems which have to be solved with quality assurance tools (configuration management, testing, and quality data reporting systems). In order to grant a software high quality level against a reasonable cost, the testing planning phase has to be study in detail. In order to do so, an adequate coverage of the product functionality has to be supplied to reduce the test time. The aim of the paper is suggesting an automated software testing as a solution to the problem of having to maximize the test plan coverage within the available time and to increase software reliability and quality in use.

Definition of Safety Levels and Performances of Safety: Applications for an Electronic Equipment Used on Rolling Stock

This work presents a safety analysis on an electronic equipment used on rolling stock in according to the international safety standard, IEC 61508. Alternative methods, the fault tree analysis (FTA) and the Markov-Chain analysis, are shown and discussed in this paper. Such methods allow to cover wider reliability configuration classes with respect to the formulas suggested in the standard.