A comprehensive simulator for assessing the reliability of a photovoltaic panel peak power tracking system

When designing a maximum power point tracking (MPPT) algorithm, it is often difficult to correctly predict, before field testing, the behavior of this MPPT under varying solar irradiation on photovoltaic (PV) panels. A solution to this problem is to design a maximum power point trackers simulator of a PV system used to test MPPT algorithms. This simulator must have the same role as the MPPT card of the PV panel and thus will fully emulate the response of a real MPPT card of the PV panel. Therefore, it is a good substitute to help to test the peak power trackers of the PV system in the laboratory. This paper describes a simple peak power trackers simulator of the PV system which has a short response time thus, can be used to test MPPT algorithms under very rapid variation condition. The obtained results and the theoretical operation confirm the reliability and the superior performance of the proposed model.     

Daily energy planning of a household photovoltaic panel

This paper puts forward an energy planning approach which offers a daily optimum management of a household photovoltaic panel generation (PVG) without using storage equipment. The approach considers the PVG of the last 10 days to estimate the one of the next day, using a Neuro-Fuzzy algorithm. The estimated PVG is planned according to the consumer’s needs so as to use the maximum of the generated energy. The algorithm decides by means of fuzzy rules the connection times of appliances, having different powers, to the photovoltaic panel (PVP) output during the day. The decision is made on the basis of optimization criteria with respect to different user operation modes. The approach is validated on a 260 Wp PVP and a set of four appliances of 30 W, 40 W, 60 W and 75 W. The system is installed at the National Engineering School, University of Sfax (ENIS) – Tunisia. The daily energetic assessment confirms that the PVG planning makes use of the estimated available energy in between 70% and 80%.     

Improved process monitoring using the CUSUM and EWMA-based multiscale PCA fault detection framework

Process monitoring techniques are of paramount importance in the chemical industry to improve both the product quality and plant safety. Small or incipient irregularities may lead to severe degradation in complex chemical processes, and the conventional process monitoring techniques cannot detect these irregularities. In this study to improve the performance of monitoring, an online multiscale fault detection approach is proposed by integrating multiscale principal component analysis (MSPCA) with cumulative sum (CUSUM) and exponentially weighted moving average (EWMA) control charts. The new Hotelling's T² and square prediction error (SPE) based fault detection indices are proposed to detect the incipient irregularities in the process data. The performance of the proposed fault detection methods was tested for simulated data obtained from the CSTR system and compared to that of conventional PCA and MSPCA based methods. The results demonstrate that the proposed EWMA based MSPCA fault detection method was successful in detecting the faults. Moreover, a comparative study shows that the SPE-EWMA monitoring index exhibits a better performance with lower values of missed detections ranging from 0% to 0.80% and false alarms ranging from 0% to 21.20%.     

Effect of amorphous SiC layer on electrical and optical properties of Al/a-SiC/c-Si Schottky diode for optoelectronic applications

Journal of Materials Science: Materials in Electronics - In this work, we report on the study of the electrical and optical properties of amorphous silicon carbide (a-SiC)-based Schottky diodes for...     

Vanadium doped SnO<Subscript>2</Subscript> nanoparticles for photocatalytic degradation of methylene blue

Nanometric V-doped particles with vanadium concentration varying from 0 to 10% were prepared using the polyol method. The influence of the doping on the textural, structural and optical properties was studied by various methods of characterization. X-ray diffraction (XRD) patterns disclose that nanocrystallites of cassiterite, i.e. rutile-like tetragonal structure SnO₂ and the absence of a new vanadium phase in the XRD pattern in the different concentration of doping were formed after annealing, the ordinary crystallite size decreased from 20.6 to 12.3 when the doping concentration increased from 0 to 10%, respectively. Moreover, the N₂ sorption porosimetry and transmission electron microscopic show that all samples synthesized were constituted of an aggregated network of almost spherical nanoparticles, which sizes changed with the altitude in the doping concentration to 10%. In accordance with UV–visible absorption measurements, this diminution of nanoparticles sizes was followed by a decrease in the band gap value from 3.25 eV, for undoped SnO₂, to 2.75 eV, for SnO₂ doped at 10%. On the other part, the photocatalytic activity of undoped and V-doped SnO₂ nanoparticles was studied using methylene blue (MB) as model organic pollutants. The SnO₂ nanoparticles doped at 10% of vanadium disclosed that the discoloration of MB reached 97.4% after irradiation of 120 min, with an apparent constant rate of the degradation reaching 0.035 min^?1 for MB degradation that was about 2.5 times more than that of pure SnO₂ (0.014 min^?1).     

A comparative study between three different methods of hydrogel network characterization: effect of composition on the crosslinking properties using sol–gel,rheological and mechanical analyses

Polymer Bulletin - Previously, different techniques were used to identify the crosslinking density of hydrogels. In this study, we aimed to compare three different methods of network structure...     

Combining Soft Chemistry and Spark Plasma Sintering to Produce Highly Dense and Finely Grained Soft Ferrimagnetic Y3Fe5O12 (YIG) Ceramics

We report the synthesis of yttrium iron garnet (YIG) combining soft chemistry route, namely the polyol process, and spark plasma sintering (SPS) technique. The polyol process produced an intermediary amorphous phase containing both iron and yttrium cations in the desired ratio. They were annealed at 400°C in air to decompose the organic content of the reaction (polyol and acetate). To achieve the garnet phase, the polyol‐obtained precursor was subjected to reactive SPS treatment at a temperature of 750°C, far below the typical temperatures (1350°C) used in the classic solid‐state reaction process. In 15 min pure and high‐density Y₃Fe₅O₁₂ ceramic, with about 100 nm sized crystalline grains, was obtained. We report as well the characterization of the initial amorphous phase and the obtained YIG by X‐ray diffraction, scanning electron microscopy, Fourier‐transform infrared spectroscopy, ⁵⁷Fe Mössbauer spectrometry, and magnetization measurements.     

Purification and characterization of an amylase from Opuntiaficus‐indica seeds

BACKGROUND: In Tunisia, prickly pear fruit grow spontaneously; it is consumed as fresh fruit, juice or jam. When the fruit is used for juice production, the seeds are discarded and go to waste. Our study aimed to extract biomolecules from seeds by producing value‐added products from the fruits. RESULTS: An amylase from Opuntia ficus‐indica seeds was extracted and purified to homogeneity. An increase in specific activity of 113‐fold was observed. The apparent molecular mass of the enzyme is 64 kDa. The optimum pH and temperature for enzyme activity were pH 5 and 60 °C, respectively. Under these conditions, the specific activity is 245.5 U mg^?1. The enzyme was activated by Co²⁺ and Mg²⁺ (relative activity 117% and 113% respectively) at lower ion concentrations. It was strongly inhibited by Mn²⁺ and Fe²⁺. Cu²⁺ inhibited totally the activity of this enzyme, but Ca²⁺ has an inhibitory effect which increases with ion concentration. CONCLUSION: The extracted enzyme belongs to the exo type of amylases and is classified as a β‐cyclodextrin glycosyltransferase since it generates mainly β‐cyclodextrin from starch. It exhibits high thermal stability and a broad range of pH stability, making it a promising prospect for industrial and food applications. Copyright © 2012 Society of Chemical Industry     

Two-dimensional contour cutting of polycrystalline cubic boron nitride using a novel laser/water jet hybrid process

In the laser/water jet hybrid machining (LWJ), a novel process applicable to brittle materials, the laser beam creates a groove through evaporation and causes solid-state phase transition through heating and shock waves while the water jet performs quenching. Both laser and water jet induce stresses and phase changes that lead to cutting via crack formation and controlled fracture mechanism through the rest of the thickness. While LWJ is very well documented by our group for one-dimensional cutting, it remains as a challenge for two-dimensional cutting because of the changing direction of the crack in relation to the laser beam path. In this paper, a focused continuous wave CO₂ laser (400?W) was combined with abrasive-free water jet at 0.4–1.4?MPa (60–200?psi) to generate and steer the controlled crack in two directions in polycrystalline cubic boron nitride tool blanks. A 42.33-mm/s (100?in./min) cutting speed was used in all the tests. The direction of the cracks generated by LWJ was changed to 60°, 108°, 120°, 135° and made to follow a curve with 1?mm radius in accordance with the standard tool shapes. The cut quality was investigated at the point of change in the crack direction using optical profilometer, Raman spectroscopy, and scanning electron microscopy. Results indicated that successful cuts were made with obtuse angles (120° and 135°) in contrast to acute angles (60°). The crack propagation in the heat affected zone, where the phase transition from c-BN to a new phase has occurred, is responsible for the inability to obtain good quality cuts in the acute angle cases. A preliminary graphical representation that explains the observed experimental results is formulated.