Dorin Petreus

An energy converter method for battery cell balancing

Batteries packs made of series-parallel connected cells have developed a lot lately. These new solutions brought along with them some safety issues due to the possibility of overcharging or under-discharging of every individual cell that forms the pack. Balancing is one of the most important issues regarding battery management, as without it the individual cell voltages will draft apart over time and the packs total capacity will also decrease more quickly. This paper presents some theory behind the balancing methods developed so far and presents a new system used for cell balancing.

Arsenic and antimony determination in non- and biodegradable materials by hydride generation capacitively coupled plasma microtorch optical emission spectrometry.

A sensitive method using a miniature analytical system with a capacitively coupled plasma microtorch (25 W, 13.56 MHz, 0.4 l min(-1) Ar) was developed and evaluated for the determination of As and Sb in recyclable plastics and biodegradable materials by hydride generation optical emission spectrometry. Given their toxicity, As and Sb should be subject to monitoring in such materials despite not being included within the scope of Restriction of Hazardous Substances Directive. The advantages of the proposed approach are better detection limits and lower analysis cost relative to conventional systems based on inductively coupled plasma optical emission and flame atomic absorption spectrometry with/without derivatization. Samples were subjected to acidic microwave-assisted digestion in a nitric-sulfuric acid mixture. Chemical hydride generation with 0.5% NaBH4 after the prereduction of As(V) and Sb(V) with 0.3% L-cysteine in 0.01 mol l(-1) HCl (10 min contact time at 90±5°C) was used. Under the optimal hydride generation conditions and analytical system operation the detection limits (mg kg(-1)) were 0.5 (As) and 0.1 (Sb), whereas the precision was 0.4-7.1% for 10.2-46.2 mg kg(-1) As and 0.4-3.2% for 7.1-156 mg kg(-1) Sb. Analysis of two polyethylene CRMs revealed recoveries of 101±2% As and 100±1% Sb.

A novel global MPPT based on genetic algorithms for photovoltaic systems under the influence of partial shading

This paper presents a novel maximum power point tracking (MPPT) algorithm, based on genetic algorithms (GA). This algorithm is used for searching the global maximum power point (GMPP) for photovoltaic systems affected by partial shading. The “Perturb and Observe” (P&O) algorithm is embedded into the GA function for improving the optimisation process. By adding this functionality to the algorithm, the number of iterations and the population size is low, thus finding the MPP in a short time. Description of this algorithm and its performances will be detailed in this article, verified through simulation and experimental results.

Modeling and simulation of supercapacitors

In this paper we present some models for supercapacitors. The supercapacitors are used more and more in high level industries such as: traction systems, automotive industry, aerospace industry, telecommunications etc. Understanding supercapacitors operation mode is necessary so we can be able to determine the applications which require these components, and to be able to choose between supercapacitors and other energy storage devices. In this paper were used some models for the implementation of supercapacitors, and the simulations made in Orcad 9.2 to determine their operation, are in time and frequency domain. Also, the models were implemented in Simulink 7.5 and the simulation results prove the models accuracy. Two test measurements on the ECOND Pscap350 supercapacitor were realized and using the measurement data, two methods to compute the parameters are presented.

Simultaneous determination of As and Sb in soil using hydride generation capacitively coupled plasma microtorch optical emission spectrometry – comparison with inductively coupled plasma optical emission spectrometry

A method using a miniature analytical system based on hydride generation capacitively coupled plasma microtorch optical emission spectrometry with a QE65 Pro microspectrometer was developed and evaluated for the simultaneous determination of As and Sb in soil samples. The use of this microspectrometer allows the examination of the spectral range between 190 and 220 nm where the continuum background emission of the plasma is low and the most intense resonance lines As 193.759; 197.262 nm and Sb 206.833; 217.581 nm are located. The method involves microwave-assisted digestion of samples in aqua regia, prereduction of As(V) and Sb(V) to their (+3) species with 0.3% L-cysteine by heating in a boiling water bath at 90 ± 5 °C and hydride generation in 0.01 mol L−1 HCl (pH = 2.00 ± 0.01) medium with 0.5% NaBH4 solution. The method was optimized in order to provide the simultaneous determination of As and Sb. The figures of merit were evaluated at different emission wavelengths under the optimum conditions of plasma microtorch operation (10 W, 150 mL min−1 Ar), and the best performances were obtained at 193.759 nm (As) and 217.581 nm (Sb). The figures of merit of the method were compared to those of the traditional hydride generation inductively coupled plasma optical emission spectrometry taken as a reference method. Analysis of CRMs revealed recoveries of 101 ± 9% As and 102 ± 3% Sb comparable to 102 ± 7% As and 98 ± 4% Sb in the reference method. The precision of determinations was 2–10% for 90–210 mg kg−1 As and 40–130 mg kg−1 Sb, close to 3–8% in hydride generation inductively coupled plasma optical emission spectrometry. The Bland and Altman test performed on 10 soil samples indicated no significant difference between the results obtained by the two methods, so that the miniature analytical system could be successfully applied for As and Sb monitoring in environmental samples. The proposed method is attractive in terms of analytical costs due to limited consumption of high purity HCl, power and Ar to sustain the plasma, and therefore more advantageous than hydride generation inductively coupled plasma optical emission spectrometry.

Analytical characterization of a method for mercury determination in food using cold vapour capacitively coupled plasma microtorch optical emission spectrometry – compliance with European legislation requirements

This paper presents the analytical characterization of a highly sensitive and inexpensive method for Hg determination in food based on cold vapour capacitively coupled plasma microtorch optical emission spectrometry. The novelty of the work lies in combining the on-line preconcentration of Hg cold vapour on a gold filament microcollector with a low-power (20 W) and low Ar consumption (200 mL min−1) microtorch to increase the sensitivity of the method. The method involves microwave assisted digestion of the lyophilized samples in a HNO3–H2O2 mixture, conventional chemical cold vapour generation using the SnCl2–HCl system, on-line preconcentration on a gold filament and emission measurement at 253.652 nm using a low-resolution microspectrometer. The figures of merit were discussed in relation with the demands in the Decisions 2007/333/EC, 2011/836/EC and 2002/657/EC on the determination of toxic elements in food. The detection and quantification limits were 0.005 μg kg−1 and 0.015 μg kg−1 allowing the use of the method for Hg determination in foods such as chicken meat, bread, rice, vegetables and fruits. For concentrations in the range 0.57–25.2 μg kg−1 the precision was 0.7–9.0%, below the maximum standard uncertainty set in the above mentioned legislation. Recovery of 97.9 ± 4.6% and trueness in the range (−7.7)–(+4.7%) in the analysis of five certified reference materials were found to be satisfactory, since the found concentrations fall within the ±10% bound of the target value. The proposed method developed using miniaturized instrumentation is cost-effective and enables us to achieve Hg determination in food complying with European legislation. The system has analytical potential for the future and prototyping perspectives.

A miniaturized capacitively coupled plasma microtorch optical emission spectrometer and a Rh coiled-filament as small-sized electrothermal vaporization device for simultaneous determination of volatile elements from liquid microsamples: Spectral and analytical characterization

A low power and low argon consumption (13.56 MHz, 15 W, 150 ml min(-1)) capacitively coupled plasma microtorch interfaced with a low-resolution microspectrometer and a small-sized electrothermal vaporization Rh coiled-filament as liquid microsample introduction device into the plasma was investigated for the simultaneous determination of several volatile elements of interest for environment. Constructive details, spectral and analytical characteristics, and optimum operating conditions of the laboratory equipment for the simultaneous determination of Ag, Cd, Cu, Pb and Zn requiring low vaporization power are provided. The method involves drying of 10 μl sample at 100°C, vaporization at 1500°C and emission measurement by capture of 20 successive spectral episodes each at an integration time of 500 ms. Experiments showed that emission of elements and plasma background were disturbed by the presence of complex matrix and hot Ar flow transporting the microsample into plasma. The emission spectrum of elements is simple, dominated by the resonance lines. The analytical system provided detection limits in the ng ml(-1) range: 0.5(Ag); 1.5(Cd); 5.6(Cu); 20(Pb) and 3(Zn) and absolute detection limits of the order of pg: 5(Ag); 15(Cd); 56(Cu); 200(Pb) and 30(Zn). It was demonstrated the utility and capability of the miniaturized analytical system in the simultaneous determination of elements in soil and water sediment using the standard addition method to compensate for the non-spectral effects of alkali and earth alkaline elements. The analysis of eight certified reference materials exhibited reliable results with recovery in the range of 95-108% and precision of 0.5-9.0% for the five examined elements. The proposed miniaturized analytical system is attractive due to the simple construction of the electrothermal vaporization device and microtorch, low costs associated to plasma generation, high analytical sensitivity and easy-to-run for simultaneous multielemental analysis of liquid microsamples.

Supercapacitor modelling using experimental measurements

Supercapacitors are components for energy storage, dedicated for applications where both energy and power density are needed. Even if their energy density is ten times lower than the energy density of batteries, supercapacitors offer new alternatives for applications where energy storage is needed. We have done an experimental bench and we have measured the voltage across a supercapacitor in a constant current charge/discharge cycle. Using these measurements and a mathematical algorithm we have proposed an electrical model for the supercapacitor, and we have determined the parameters of the model also.

Assessment of Temperature Distribution in Intraperitoneal Chemohyperthermia

Advanced modeling techniques and multipoint temperature measurement devices are required in order to create a complex intraperitoneal chemohyperthermia physical model. This paper proposes two configurations appropriate for the implementation of a multipoint temperature measurement system. The design constrains were carefully defined considering the overall chemohyperthermia performance expectations and the need to provide thermal data for building a consistent 3D thermal map of the intra-peritoneal volume.

Design of a plasma generator based on E power amplifier and impedance matching

The paper presents the design key issues for a plasma generation method. A Class E Power Amplifier is used to generate plasma at 13.56MHz with a variable load implemented with an air coil and a variable capacitor. Class E amplifier represents a mean of high efficiency power amplification. Ideal amplifiers reach 100% efficiency and by proper filtering and tuning even the real circuit efficiency can be only 5% lower. By measuring the input impedance of the matching network the resistance, the voltage and the power of the plasma torch can be estimated. In order to do that, two matching networks were designed; the first one is partially compensated and the second is completely compensated. The problems that can appear at a capacitive tuning in air and Argon atmosphere are also presented. Finally, the steps needed to design the plasma generator with class E power amplifier and air coils are described.