Advanced controller design based on gain and phase margin for microgrid containing PV/WTG/Fuel cell/Electrolyzer/BESS

Nowadays, with the increase in the amount of power generation related to renewable energy resources, the need for energy storage and management is raised. In this regard, the hydrogen energy plays a critical role in the development of renewable technologies. In view of the above, advanced controller design is presented in this paper to effectively perform load frequency control of islanded fuel cell microgrid based on the wind turbine, photovoltaic, fuel cell, electrolyzer, battery energy storage systems, and residential and commercial loads. The controller design is based on the determination of the controller parameters that the fuel cell microgrid system will provide the desired dynamic properties. In the proposed controller design, virtual gain and phase margin testers are added to provide the desired dynamic properties. The controller's stable parameter plane is determined with the help of the stability boundary locus method, taking into account time delay, gain, and phase margin. First, the accuracy of the stable parameter plane determined for the proposed controller design is demonstrated by means of time domain and eigenvalue analyzes. Finally, in order to show the performance of the advanced controller design and the success of the fuel cell as a backup generator, analysis studies have been carried out using actual data of solar and wind, and appropriate changes of load in studied microgrid.     

Magnetic field enhancement of electrochemical hydrogen evolution reaction probed by magneto-optics

External magnetic fields affect various electrochemical processes and can be used to enhance the efficiency of the electrochemical water splitting reaction. However, the driving forces behind this effect are poorly understood due to the analytical challenges of the available interface-sensitive techniques. Here, we present a set-up based on magneto- and electro-optical probing, which allows to juxtapose the magnetic properties of the electrode with the electrochemical current densities in situ at various applied potentials and magnetic fields. On the example of an archetypal hydrogen evolution catalyst, Pt (in a form of Co/Pt superlattice), we provide evidence that a magnetic field acts on the electrochemical double layer affecting the local concentration gradient of hydroxide ions, which simultaneously affects the magneto-optical and magnetocurrent response.     

A deep learning-based CEP rule extraction framework for IoT data

The Journal of Supercomputing - With the recent developments in Internet of Things (IoT), the number of sensors that generate raw data with high velocity, variety, and volume is tremendously...     

Energy use,CO2 emission and foreign direct investment: Is there any inconsistence between causal relations?

In this study, the causal relations between inward foreign direct investment (FDI)-energy use per capita and inward FDI-CO₂ emission per capita were analyzed and the inconsistency between the causal relations was investigated via bootstrap-corrected panel causality test and cross-correlation analysis. In this direction, data from 76 countries including the period of 1980–2009 was processed. No supportive evidence was found for changing causal relations to country group which was classified into income level. The findings indicated that while the pollution haven hypothesis was supported for Mozambique, United Arab Emirates and Oman, the pollution halo hypothesis was supported in the case of India, Iceland, Panama and Zambia. For other countries, energy use and CO₂ emission were neutral to inward FDI flows in aggregated level. Furthermore, this study urged that increased (decreased) energy use due to the inward FDI flows did not necessarily mean an increase (decrease) in pollution level, and vice versa. For policy purpose, FDI attractive policy should be regulated by taking into account this possibility.     

The analysis of thermoluminescent glow peaks of natural calcite after beta irradiation

In this study, the thermoluminescence properties of natural calcite samples were examined in detail. The glow curve of the sample irradiated with beta radiation shows two main peaks, P1 (at 115 °C) and P4 (at 254 °C). The additive dose, variable heating rate, computer glow curve deconvolution, peak shape and three point methods have been used to evaluate the trapping parameters, namely the order of kinetics (b), activation energy (E) and the frequency factor (s) associated with the dosimetric thermoluminescent glow peaks (P1 and P4) of natural calcite after different dose levels with beta irradiation.     

Epoxy‐ and polyester‐based composites reinforced with glass,carbon and aramid fabrics: Measurement of heat capacity and thermal conductivity of composites by differential scanning calorimetry

The primary purpose of the study is to investigate the temperature dependence of heat capacity and thermal conductivity of composites having different fiber/matrix combinations by means of heat‐flux differential scanning calorimetry (DSC). The materials used as samples in this study were epoxy‐ and polyester‐based composites. Noncrimp stitched glass, carbon, and aramid fabric were used as reinforcements for making unidirectional composites. For the heat capacity measurements the composite sample and a standard material are separately subjected to same linear temperature program. By recording the heat flow rate into the composite sample as a function of temperature, and comparing it with the heat flow rate into a standard material under the same conditions, the temperature dependence of heat capacity of the composite sample is determined. Measurements were carried out over a wide range of temperatures from about 20 to 250°C. The differential scanning calorimeter was adapted to perform the thermal conductivity measurements in the direction perpendicular to the fiber axis over the temperature range of 45–235°C. The method used in this study utilizes the measurement of rate of heat flow into a sensor material during its first‐order phase transition to obtain the thermal resistance of a composite material placed between the sensor material and the heater in the DSC. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of diffusion-annealing time (0.5 h ≤ t ≤ 2 h) on the mechanical and superconducting properties of Cu-diffused bulk MgB2 superconductors by use of experimental and different theoretical models

This study reports the effect of different annealing time (0.5 h ≤ t ≤ 2 h) on the electrical, physical, microstructural, mechanical and superconducting properties of Cu-diffused bulk magnesium diboride (MgB₂) system by means of dc resistivity, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and microhardness measurements (H _v ). The room temperature resistivity (at 300 K), critical transition (T _c ^offset and T _c ^onset ) temperature, variation of transition temperature, grain size, phase purity, lattice parameter, texturing, surface morphology, crystallinity and Vickers microhardness values of the samples are evaluated and compared with each other. The resistivity results obtained reveal that the (T _c ^offset and T _c ^onset ) values of the samples produced ascend with the enhancement in the annealing time up to 1 h beyond which these values start to reduce systematically and in fact the smallest T _c ^onset of 38.1 K and T _c ^offset of 36.2 K are observed for the sample annealed for 2 h. Similarly, the SEM micrographs display that the surface morphology, crystallinity and grain connectivity improve until a certain diffusion-annealing time (1 h), and after this point, all the properties obtained start to degrade with the increase of the annealing time. Furthermore, the peak intensities, grain sizes and lattice parameters deduced from the XRD measurements illustrate that a systematic elongation in the a and c axis lengths is detected with the annealing time until 1 h beyond which a regular contraction in the lattice parameters is observed for the samples. Likewise, the peak intensities belonging to MgB₂ phase enhance with the increment of the annealing time up to 1 h after which they reduce slowly; however, a new peak belonging to Mg₂Cu phase appears in the sample annealed for the duration of 2 h, confirming both the reduction of the grain size and degradation of the critical temperature. Additionally, we have focused on the microhardness measurements for the examination of the mechanical properties of the samples studied. Experimental results of microhardness measurements are estimated using the various models such as Meyer’s law, proportional sample resistance model, modified proportional sample resistance model and Hays-Kendall (HK) approach. Based on the simulation results obtained, the Hays-Kendall (HK) approach is determined as the most suitable model describing the mechanical properties of samples prepared.     

Sn diffusion coefficient and activation energy determined by way of XRD measurement and evaluation of micromechanical properties of Sn diffused YBa2Cu3O7−x superconducting ceramics

This study manifests not only the effect of Sn diffusion on physical, electrical, mechanical, structural and superconducting properties of the bulk YBa₂Cu₃O_7?x (Y123) superconductors prepared by the conventional solid-state reaction route by use of electrical resistance, X-ray diffraction analysis (XRD), electron dispersive X-ray, scanning electron microscopy, transport critical current density (J _c ) and Vickers microhardness (H _v ) measurements but also the diffusion coefficient and the activation energy of tin (Sn) in the Y123 material for the first time. The diffusion coefficient and the activation energy of Sn are investigated in the temperature range 500–945 °C using the change of the lattice parameters extracted from the XRD patterns. The resistance (at room temperature), critical (onset and offset) temperature, variation of critical temperature, hole-carrier concentration, crystallinity, lattice parameter, texturing, surface morphology, lotgering index, element distribution, critical current density, oxygen content, load dependent microhardness, elastic modulus and yield strength values are obtained for the pure and Sn diffused samples and compared with each other. One can see that all superconducting parameters given above depend sensitively on the Sn diffusion on Y123 system. The obtained results exhibit that the room temperature resistance enhances with the Sn diffusion because of the hole filling when the onset $ (T_{c}^{onset} ) $ ( T c onset ) and offset $ (T_{c}^{offset} ) $ ( T c offset ) critical temperatures are obtained to be about 93.4 and 89.6 K for the pure sample as against 92.2 and 88.1 K for the Sn diffused sample, respectively. This may be attributed to the fact that the decrement in the critical temperatures is due to the deterioration of crystallinity and descend in the grain size. As for the critical current density measurements, J _c values are obtained to be about 125.4–65.3 A/cm², respectively, for the undiffused and Sn diffused materials. This may be led to the decrease of the flux pinning mechanism stemming from the stacking faults, planar and micro-defects. At the same time, XRD measurements display that the samples produced in this work exhibit the polycrystalline superconducting phase with the changing intensity of diffraction lines. Besides, the peak intensities belonging to major phase (Y123) decrease monotonously with Sn diffusion in the system; however, new peaks belonging to the minor (BaCuO₂) phases start to appear for Sn diffused sample confirming both the reduction of the grain size and degradation of the critical temperature. Moreover, the pure sample is confirmed by both enhancement of a and b lattice constants and the decrement of the cell parameter c of the sample in comparison with that of the Sn diffused sample. According to SEM examination, the crystallinity and grain connectivity suppress with the Sn diffusion. EDX measurements illustrate that not only do the elements used for the preparation of the Y123 superconductors with and without Sn diffusion distribute homogeneously but also the level of Cu element reduces with the Sn diffusion, presenting that the Cu²⁺ ions may partly be diffused by tetravalent tin (Sn⁴⁺) ions. Further, surprising results of the Vickers microhardness values demonstrate that the pure sample visualizes Indentation Size Effect (ISE) feature; however, the Sn diffused sample reports Reverse Indentation Size Effect (RISE) nature. Additionally, the diffusion coefficient is observed to increase from 1.11 × 10^?9 to 2.82 × 10^?8 cm² s^?1 as the diffusion-annealing temperature increases, verifying that the Sn diffusion at lower temperatures is much less significant as compared to the higher ones. Temperature dependence of the Sn diffusion coefficient and activation energy in the range of 500–945 °C is defined with the aid of the following equation: $$ D = 7.78 \times 10^{ - 6} { \exp }\left[ {\left( {( - 0.590 \pm 0.005){\raise0.7ex\hbox{${\text{eV}}$} \!\mathord{\left/ {\vphantom {{\text{eV}} {k_{B} T}}}\right.\kern-0pt} \!\lower0.7ex\hbox{${k_{B} T}$}}} \right)} \right] $$ D = 7.78 × 10 ? 6 exp [ ( ( ? 0.590 ± 0.005 ) eV / eV k B T k B T ) ] .     

Force analysis of bearings on a modified mechanism using proposed recurrent hybrid neural networks

Due to different load conditions on four-bar mechanisms, it is necessary to analyze force distribution on the bearing systems of mechanisms. A proposed neural network was developed and designed to analyze force distribution on the bearings of a four bar mechanism. The proposed neural network has three layers: input layer, output layer and hidden layer. The hidden layer consists of a recurrent structure to keep dynamic memory for later use. The mechanism is an extended version of a four-bar mechanism. Two elements, spring and viscous, are employed to overcome big force problem on the bearings of the mechanism. The results of the proposed neural network give superior performance for analyzing the forces on the bearings of the four-bar mechanism undergoing big forces and high repetitive motion tracking. This continuation of simulation analysis of bearings should be a benefit to bearing designers and researchers of such mechanisms.