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

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

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

Experimental testing of a horizontal-axis wind turbine to assess its performance

This paper describes a test procedure to investigate the performance of a micro wind turbine with horizontal-axis. A 3D model of a rotor with five blades has been designed by a MATLAB software; its airfoil is optimized to efficiently work at low wind speed. The rotor is coupled to an electric generator and this equipment is tested in a wind tunnel. An anemometer is used to measure and set the desired wind speeds. Electric quantities, i.e., voltage, current and power, are acquired by a digital multimeter. A variable resistance is used to change the operating point of the generator. Preliminary results are reported that refer to the application of the proposed test procedures to a wind turbine with a 0.2 m2 swept area

Exploring circannual rhythms and chronotype effect in patients with Obsessive-Compulsive Tic Disorder (OCTD) : a pilot study

Background: The aim of this study was to test, through a chronobiologic approach, the existence of a significant circannual rhythm of tics and obsessive-compulsive symptoms in patients with Obsessive-Compulsive Tic Disorder (OCTD). The chronotype effect on tics and OC symptoms during seasons was also studied. Methods: Patients with a diagnosis of OCTD (N = 37; mean age = 18.78 \ub1 8.61) underwent four clinical evaluations: Winter (WIN), Spring (SPR), Summer (SUM) and Autumn (AUT). Tics were evaluated through Yale Global Tic Severity Scale (YGTSS) and OC symptoms through Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Patients\u2019 chronotype was assessed by the Horne-Ostberg morningness-eveningness questionnaire (MEQ), which categorizes subjects according to the individuals'chronotype, being morning-type, evening-type, and neither-type. Results: A statistically significant circannual rhythm was observed for OC symptoms (p = 0.007), with the acrophase occurring between AUT and WIN. Y-BOCS differed along the year (p = 0.0003 and \u3b72p = 0.40) with lower results in SUM compared to WIN (p < 0.05) and AUT (p < 0.01). Tics displayed no circannual rhythm and YGTSS scores were comparable among seasons. Patients were classified as 15 morning-types (40.5%) 15 neither-types (40.5%) and 7 evening-types (19.0%). YGTSS data were similar for all chronotypes while Y-BOCS results were greater during SUM in evening-types than morning-type patients (p < 0.05; 15.7 \ub1 5.2 vs 3.4 \ub1 6.0). Limitations: It is essential to investigate the existence of tics and OC symptoms circannual rhythms over the course of more than one year with a larger sample. Conclusions: OC symptoms displayed a significant circannual rhythm and were influenced by patients\u2019 chronotype. On the contrary, tics resulted similar among seasons and chronotypes

Innovative Laboratories for Teaching on Photovoltaic Generation in Higher Education

The production of energy from Photovoltaic technology is becoming more and more relevant. Therefore, it is essential that academic world focuses attention on this topic in order to properly teach and transmit knowledge, skills and abilities. These ones are very useful in work activities. The academic course 'Photovoltaic Power Generation' aims to better explain theoretical aspects by practical activities which require the implementation of innovative laboratories for learning. This paper presents the guidelines for replication of laboratory practices (twin labs), already offered to Italian students, in the context of the project EU-MONG

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

A pre-docking source for the power-law behavior of spontaneous quantal release: application to the analysis of LTP

In neurons, power-law behavior with different scaling exponents has been reported at many different levels, including fluctuations in membrane potentials, synaptic transmission up to neuronal network dynamics. Unfortunately in most cases the source of this nonlinear feature remains controversial. Here we have analyzed the dynamics of spontaneous quantal release at hippocampal synapses and characterized their power-law behavior. While in control conditions a fractal exponent greater than zero was rarely observed, its value was greatly increased by α-latrotoxin (α-LTX), a potent stimulator of spontaneous release, known to act at the very last step of vesicle fusion. Based on computer modeling, we confirmed that at an increase in fusion probability would unmask a pre-docking phenomenon with 1/f structure, where α estimated from the release series appears to sense the increase in release probability independently from the number of active sites. In the simplest scenario the pre-docking 1/f process could coincide with the Brownian diffusion of synaptic vesicles. Interestingly, when the effect of long-term potentiation (LTP) was tested, a ∼200% long-lasting increase in quantal frequency was accompanied by a significant increase in the scaling exponent. The similarity between the action of LTP and of α-LTX suggests an increased contribution of high release probability sites following the induction of LTP. In conclusion, our results indicate that the source of the synaptic powerlaw behavior arises before synaptic vesicles dock to the active zone and that the fractal exponent α is capable of sensing a change in release probability independently from the number of active sites or synapses. © 2015 Lamanna, Signorini, Cerutti and Malgaroli

Scale invariant disordered nanotopography promotes hippocampal neuron development and maturation with involvement of mechanotransductive pathways

The identification of biomaterials which promote neuronal maturation up to the generation of integrated neural circuits is fundamental for modern neuroscience. The development of neural circuits arises from complex maturative processes regulated by poorly understood signaling events, often guided by the extracellular matrix (ECM). Here we report that nanostructured zirconia surfaces, produced by supersonic cluster beam deposition of zirconia nanoparticles and characterized by ECM-like nanotopographical features, can direct the maturation of neural networks. Hippocampal neurons cultured on such cluster-assembled surfaces displayed enhanced differentiation paralleled by functional changes. The latter was demonstrated by single-cell electrophysiology showing earlier action potential generation and increased spontaneous postsynaptic currents compared to the neurons grown on the featureless unnaturally flat standard control surfaces. Label-free shotgun proteomics broadly confirmed the functional changes and suggests furthermore a vast impact of the neuron/nanotopography interaction on mechanotransductive machinery components, known to control physiological in vivo ECM-regulated axon guidance and synaptic plasticity. Our results indicate a potential of cluster-assembled zirconia nanotopography exploitable for the creation of efficient neural tissue interfaces and cell culture devices promoting neurogenic events, but also for unveiling mechanotransductive aspects of neuronal development and maturation

Functional mapping of brain synapses by the enriching activity-marker SynaptoZip

Ideally, elucidating the role of specific brain circuits in animal behavior would require the ability to measure activity at all involved synapses, possibly with unrestricted field of view, thus even at those boutons deeply located into the brain. Here, we introduce and validate an efficient scheme reporting synaptic vesicle cycling in vivo. This is based on SynaptoZip, a genetically encoded molecule deploying in the vesicular lumen a bait moiety designed to capture upon exocytosis a labeled alien peptide, Synbond. The resulting signal is cumulative and stores the number of cycling events occurring at individual synapses. Since this functional signal is enduring and measurable both online and ex post, SynaptoZip provides a unique method for the analysis of the history of synaptic activity in regions several millimeters below the brain surface. We show its broad applicability by reporting stimulus-evoked and spontaneous circuit activity in wide cortical fields, in anesthetized and freely moving animals