Introduzione

Questo numero di Welfare ed Ergonomia propone una riflessione sul peso che l\u2019et\ue0 ha nella societ\ue0 attuale, evidenziando la distanza tra l\u2019et\ue0 anagrafica, quella valutata collettivamente, in base a parametri sanitari e complessi calcoli economici, e quella individualmente percepita, nel gap fra l\u2019ordine prescrittivo dei ruoli prestabiliti e le performance che giovani, adulti e anziani ritengono di interpretare nelle diverse \u201cprovince di significato\u201d (Schutz 1979)

Optimisation of Generation Models for Clusters of Photovoltaic Plants

The present work analyses the actual production profiles of a group of tens of thousands of PV plants. Actual PV generation profiles are represented as hourly average powers gathered from the energy meters measured at the point of common coupling with the grid. After filtering, data cleaning and statistical analysis, reference PV plants are selected for the improvements of the PV generation models. Production profiles are calculated by using literature generation models, with weather data as inputs. An optimisation is performed on the parameters of the literature models to minimise the differences between the cumulative distribution functions of calculated profiles and measured data. The study compares the performance of the different models and shows how the optimisation increases the quality of the calculated profiles

Reliability analysis and repair activity for the components of 350 kw inverters in a large scale grid-connected photovoltaic system

The reliability of photovoltaic (PV) generators is strongly affected by the performance of Direct Current/Alternating Current (DC/AC) converters, being the major source of PV under-performance. However, generally, their reliability is not investigated at component level: thus, the present work presents a reliability analysis and the repair activity for the components of full bridge DC/AC converters. In the first part of the paper, a reliability analysis using failure rates from literature is carried out for 132 inverters (AC rated power of 350 kW each) with global AC power of 46 MW in a large scale grid-connected PV plant. Then, in the second part of the work, results from literature are compared with data obtained by analyzing industrial maintenance reports in the years 2015–2017. In conclusion, the yearly energy losses involved in the downtime are quantified, as well as their availability

Statistical Validation and Power Modelling of Hourly Profiles for a Large-Scale Photovoltaic Plant Portfolio

In the last decades, the number of photovoltaic (PV) generators significantly increased over the world. An accurate analysis of the massive data gathered from the meters of the PV plants can improve the management of their intermittent generation. This paper presents a methodology to analyse the production profiles of a portfolio of thousands of PV plants installed in an Italian region. The procedure faces the problem of filtering poor and incomplete data, then uses a stratified sampling technique for the statistical validation of the remaining profiles. Finally, the checked production profiles are used to adjust the energy model to better match the measured data and calculate the whole PV portfolio production

Maintenance Activity, Reliability, Availability, and Related Energy Losses in Ten Operating Photovoltaic Systems up to 1.8 MW

In general, photovoltaic (PV) plants do not include components with moving parts and, as a consequence, they are wrongly considered maintenance-free. Thus, this article presents a maintenance, reliability, and availability analysis of ten PV systems, with different inverter configurations, in the context of the intermittent renewable energy source systems, including the wind farms. The first part of the analysis consists of the evaluation of reliability using failure rates from the literature. In the second part, these results are compared with data obtained from industrial maintenance reports in the years 2016-2018. Finally, the yearly energy losses and the availability of each PV plant are assessed

In-field monitoring of eight photovoltaic plants: Degradation rate over seven years of continuous operation

The results of more than seven years (October 2010-December 2017) of continuous monitoring are presented in this paper that refer to eight outdoors PhotoVoltaic (PV) plants. The monitored plants are based on different technologies: mono-crystalline silicon (m-Si), poli-crystalline silicon (p-Si), string ribbon silicon, Copper Indium Gallium Selenide (CIGS) thin film and Cadmium Telluride (CdTe) thin film. Thin-film and m-Si modules are used both in fixed installation and on x-y tracking systems. The results are expressed in terms of degradation rate of the efficiency of each PV plant, which is estimated from the measurements provided by a multi-channel data-acquisition system that senses both electrical and environmental quantities. A comparison with the electrical characterization of each plant obtained by means of the transient charge of a capacitive load is also proposed. In addition, three of the monitored plants have been characterized at module level and the estimated degradation rates have been compared to the values obtained with the monitoring system. The main outcome of this work can be summarized in a higher degradation rate of thin-film based PV modules with respect to silicon-based PV modules

Innovative teaching on photovoltaic generation

One of the most important technologies for the renewable energy production is the Photovoltaic (PV) one. In the last decades, the enormous growth in the world of Photovoltaic installation capacity, and future trends, makes the knowledge of this topic fundamental for engineers working in the energy field with this competence, and not only. Thus, for students enrolled in industrial engineering courses, appropriate and innovative teaching methods are necessary. This paper aims to describe the structure of the course 'Photovoltaic Power Generation' in which solar resource and the photovoltaic generators, including power electronics, are explained. The topics of traditional theoretical lectures are presented, with the links to practical exercises and laboratories

Assessing the role of fluctuating renewables in energy transition: Methodologies and tools

Due to the environmental impacts brought by current energy schemes, the energy transition, a new paradigm shift from fossil fuels to renewable energy, has been widely accepted and is being realized through collective international, regional, and local efforts. Electricity, as the most direct and effective use of renewable energy sources (RES), plays a key role in the energy transition. In this paper, we first discuss a viable pathway to energy transition through the electricity triangle, highlighting the role of RES in electricity generation. Further, we propose methodologies for the planning of wind and solar PV, as well as how to address their uncertainty in generation expansion problems. Finally, by using a web-based tool, “RES-PLAT”, we demonstrate the scheme in a case study in Egypt, which evaluates the impacts and benefits of a large-scale RES expansion

Comparison of correction methods of wind speed for performance evaluation of wind turbines

The performance of horizontal axis wind turbines strongly depends on the speed of the wind that enters in the rotor of the turbine. Unfortunately, this quantity is rarely available since the wind speed is measured on the back of the turbine, where a lower value is present. For this reason, two correction methods are usually employed that require two input quantities: the wind speed on the back of the turbine nacelle and the wind speed detected by a meteorological station close to the investigated turbine. Since an anemometric station is not always available, a third method is here proposed that does not require this input quantity. The proposed method relies on the wind speed on the back of the turbine and the manufacturer power curve. The effectiveness of such a method is shown by comparison to the results obtained with the standard methods implemented on a wind power plant in Southern Italy

Experimental evidence of PID effect on CIGS photovoltaic modules

As well known, potential induced degradation (PID) strongly decreases the performance of photovoltaic (PV) strings made of several crystalline silicon modules in hot and wet climates. In this paper, PID tests have been performed on commercial copper indium gallium selenide (CIGS) modules to investigate if this degradation may be remarkable also for CIGS technology. The tests have been conducted inside an environmental chamber where the temperature has been set to 85 \ub0C and the relative humidity to 85%. A negative potential of 1000 V has been applied to the PV modules in different configurations. The results demonstrate that there is a degradation affecting the maximum power point and the fill factor of the current\u2010voltage (I\u2010V) curves. In fact, the measurement of the I\u2010V curves at standard test condition show that all the parameters of the PV modules are influenced. This reveals that CIGS modules suffer PID under high negative voltage: this degradation occurs by different mechanisms, such as shunting, observed only in electroluminescence images of modules tested with negative bias. After the stress test, PID is partially recovered by applying a positive voltage of 1000 V and measuring the performance recovery of the degraded modules. The leakage currents flowing during the PID test in the chamber are measured with both positive and negative voltages; this analysis indicates a correlation between leakage current and power losses in case of negative potential