Modeling and technical–economic optimization of an autonomous photovoltaic system

Solar energy technologies offer a clean and renewable energy source, and are essential components of a sustainable energy future. The current paper presents a method for technical–economic optimization of an autonomous photovoltaic system. The principal objective of this study is to find the optimum characteristics of a photovoltaic system, able to accomplish the energy requirements of a given load distribution, for a specific site.Mathematical models are exploited to analyze the working of the photovoltaic system. These models present an estimation of the recovered solar energy anywhere and anytime, an evaluation of the electric energy produced by a photovoltaic generator and a determination of the storage unit characteristics. Then, the optimizing step is done based on lack of energy to generate probability (LEGP), percentage of the surplus of energy produced (PSEP) and the cost of the kilowatt-hour produced (C_kWh).A case study has been presented to determine the optimal system configuration used to satisfy the requirements of a typical residential home located in Sfax, Tunisia.     

Variations in essential oil and fatty acid composition during Myrtus communis var. italica fruit maturation

The essential oil and fatty acid composition of Myrtus communis var. italica fruit during its ripening was determined. The effect of the harvesting time on some physical properties of Myrtus fruits, fruit weight and moisture content, were significant. The increase of fruit weight (from 2.54 to 8.79 g% fruits) during ripeness was correlated positively with that of moisture content (from 28% to 72%). Fruit essential oil yields varied from 0.003% to 0.01% and showed a remarkable increase at 60 days after flowering to reach a maximum of 0.11%. Forty-seven volatile compounds were identified in fruit essential oils; 1,8-cineole (7.31–40.99%), geranyl acetate (1.83–20.54%), linalool (0.74–18.92%) and α-pinene (1.24–12.64%) were the main monoterpene compounds. Total fatty acid contents varied from 0.81% to 3.10% during fruit maturation and the predominant fatty acids were linoleic (12.21–71.34%), palmitic (13.58–37.07%) and oleic (6.49–21.89%) acids. The linoleic acid proportions correlated inversely with palmitic and oleic acids during all the stages of ripening.     

Numerical modeling and performance evaluation of multi-tubular sodium alanate hydride finned reactor

The optimization of the hydrogen loading process in a multi-tubular sodium alanate hydride reactor equipped with longitudinal fins is investigated numerically. The effect of the number, thickness and tip clearance of the fins on the hydrogen charging rate is assessed, so that the fin optimal geometric properties are determined by the compromise between the hydrogen loading rate and the fin contribution to the weight and the volume of the storage system. Simulation results have shown that the hydrogen loading rate corresponding to this optimized configuration is 41% greater than the case without fins if we suppose a perfect interconnectivity between the fin tips and the internal walls of the hydride tubes. Otherwise, the amount of stored hydrogen decreases drastically. The loading of hydrogen under high charging pressures results in higher hydrogen loading rates and there is an interaction between the geometric and operating parameters leading to the optimized amount of stored hydrogen.     

Composition and insecticidal activity of essential oil from Pistacia lentiscus L. against Ectomyelois ceratoniae Zeller and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

This study reports investigations on the chemical constituents and fumigant toxicity of Pistacia lentiscus L. (Anacardiaceae) essential oil against two major stored-date insects, carob moth Ectomyelois ceratoniae Zeller and Mediterranean flour moth Ephestia kuehniella Zeller. Results showed that P. lentiscus essential oil contained terpinene-4-ol (23.32%), α-terpineol (7.12%) and β-caryophyllene (22.62%) as major compounds. Fumigant toxicity tests showed that P. lentiscus oil was more toxic to E. kuehniella (LC₅₀ = 1.84 μl/l, LC₉₅ = 5.14 μl/l) than E. ceratoniae (LC₅₀ = 3.29 μl/l, LC₉₅ = 14.24 μl/l). The fecundity and hatching rate of both insects decreased with increases in concentration or exposure time to the oil. At 136 μl/l air, fecundities and hatching rates were respectively 35 eggs/female and 42.86% for E. ceratoniae and 78 eggs/female and 29.49% for E. kuehniella.     

Sensitivity study of alanate hydride storage system

A successful metal hydride application is closely related to an optimized design of the storage hydrogen system. In previous studies, Hardy and Anton developed scoping and numerical models describing phenomena occurring during the loading process in an alanate storage system having the configuration of a cylindrical shell, tube and fin heat exchanger. In this paper, the numerical tool is used to evaluate the influence of varying the fin thickness and the number of heat exchanger tubes on both the loading and discharging processes. The objective is to evaluate the influence of the geometric parameters of these heat exchangers on the management of heat to be removed/supplied during the sorption process and thus optimize the loading/discharging times; while having the maximum possible volume for containing the hydride and the lightest weight of the storage system. Results showed that equipping the storage system with fins fitted to the heat exchanger tubes is the best design for efficient use of the hydride bed. In the absence of fins, a number of optimal tubes is determined, however, the hydrogen uptake rate is still lower than one obtained for the finned case and there is a reduction of volumetric and gravimetric storage capacities by comparison to the finned system.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles coated by new functionalized tetraaza-2,3 dialdehyde micro-crystalline cellulose: synthesis,characterization, and catalytic application for degradation of Acid Yellow 17

In this study, we developed an original approach for preparing cellulose-coated magnetite nanoparticles (NPs). Two novel Schiff bases (PDA-g-DAC) and [Bz-(PDA-g-DAC)] were synthesized via condensation reactions of periodate oxidized micro-crystalline cellulose (DAC) with o-phenylene diamine (PDA) to obtain its azomethine derivative with 85% yield. Subsequently, the functionalization of (PDA-g-DAC) with benzil (Bz) yields the tetraaza macrocycle [Bz-(PDA-g-DAC)]. The physicochemical characterization of the condensation products was performed using ¹³CNMR, FTIR, ATG, DSC, and X-ray diffraction techniques. Magnetic nanomaterial-based Schiff base cellulose was successfully prepared using in situ chemical co-precipitation of coordinated ferric and ferrous ions in cellulose Schiff base matrix under optimized conditions, and then, its magnetic properties were characterized. The results demonstrated that the Fe₃O₄ NPs coated with [Bz-(PDA-g-DAC)] were homogeneously coated in the matrix under ultrasonic irradiation with the saturation magnetization of 69.50 emu g^?1. In addition, XRD line broadening analysis showed that the average particle size of the NPs was 37.3 nm. Furthermore, FTIR spectra demonstrated that [Bz-(PDA-g-DAC)] concavity was anchored to magnetite Fe₃O₄ NPs through azomethine groups. Vibrating sample magnetometry (VSM) of [Bz-(PDA-g-DAC)@Fe₃O₄] magnetic nanocomposite samples showed the typical behavior of ferromagnetism. This study provided a green and facile method to inhibit magnetic nanoparticle aggregation. Activity results revealed that the prepared [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst shows the maximum activity for degradation of Acid Yellow 17 (AY17) compared to other prepared catalysts. After degradation reaction, the [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst was recovered from the reaction mixture via an external magnet and used for further five consecutive cycles with excellent catalytic activity, successively, which was comparable to the fresh catalyst. The catalyst degradation efficiency and its easy separation exhibited that [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst is a promising material for the removal of AY17 from aqueous solutions in green chemistry perspectives.     

Imaging and Spectroscopic Sensing with Low-Repetition-Rate Terahertz Pulses and GaN TeraFET Detectors

Aiming for non-destructive testing and security applications, we investigate transmission-mode imaging and spectroscopic sensing using terahertz (THz) pulses from a commercial optical parametric oscillator (OPO) in combination with THz detectors based on antenna-coupled field-effect transistors (TeraFETs). The Q-switched OPO generates quasi-continuous-wave THz pulses with a peak power of up to 1 W at a repetition rate between 12 and 90 Hz. The pulses are frequency-tunable between 0.7 and 2.6 THz with a typical linewidth of 50 GHz. We explore detection with fast GaN/AlGaN TeraFETs which hold the potential for multi-pixel and homodyne detection.     

Exploratory chemometric analysis for the characterisation of Tunisian olive cultivars according to their lipid and sterolic profiles

This study aims to evaluate some Tunisian olive genetic resources using fatty acid, triacyglycerol and sterolic compositions and to classify the cultivars according to their fruit genotype and to their respective geographical origin (North, Centre and South). manova results showed that the studied cultivars presented highly significant differences regarding all the variables (P < 0.01). The most discriminant variables of fatty acids are C17:1 (F = 98.468), C16:0 (F = 92.994), C18:1 (F = 60.865), C18:1/C18:2 (F = 44.632) and C18:2 (F = 40.167); those of triacylglycerols are POP (F = 123.34), LLL (F = 122.944), LnLO (F = 98.363), POO (F = 93.357) and LOO (F = 90.42), while sitostanol (F = 289.171), campestanol (F = 192.792) and campesterol (F = 160.724) have the higher discriminant power among sterol compounds. Principal component analysis (PCA) was performed on the data of each chemical parameter to explore their usefulness for the discrimination of eleven monovarietal olive oils. Best differentiations among cultivars were obtained with triacyglycerol and sterolic compositions. The spatial distribution of the different oil samples using all the collected data showed a good discrimination among olive cultivars. A strong resolution between the samples according to the geographical origin was obtained by means of factorial discriminant analysis (FDA) (λ = 0.002). Comparisons of the distances between classes were statistically significant (Fisher tests; P < 0.0001), and 90.91% of cross‐validated grouped cases are correctly classified. The obtained results could become an important tool for sorting out oils to a single cultivar or to a specific geographical area.     

Effects of frying on the fatty acid composition in farmed and wild gilthead sea bream (Sparus aurata)

The effects of frying in soybean (FWSO) and olive oils (FWOO) on the fatty acid composition of farmed and wild gilthead sea bream Sparus aurata were evaluated. The fat content increased with both frying treatments. However, after FWOO the moisture content of the fish was reduced to a greater extent than that in fish FWSO. The concentration of saturated fatty acids (SFA) decreased significantly during both frying processes ( P  < 0.01). However, the concentration of monounsaturated fatty acids (MUFA) increased significantly in fish fried in olive oil ( P  < 0.01). The fried fish contained a higher level of n-6 polyunsaturated fatty acids (PUFA) and a lower level of n-3 PUFA compared to raw fish. The n-3/n-6 ratio decreased in wild fish FWSO and FWOO from 0.94 ± 0.08 to 0.15 ± 0.01 and 0.15 ± 0.02, respectively. In farmed bream, the ratios decreased from 2.51 ± 0.03 to 0.18 ± 0.03 and 0.36 ± 0.01, respectively. The concentration of trans fatty acids decreased significantly in both fish types after frying ( P  < 0.05). The frying process widely affected the EPA and DHA content, limiting the positive effects of n-3 PUFA.