Ramizi Mohamed

Paper pressboard is one of the main insulating elements that need to be investigated in order to identify the life span of high voltage transformer. In actual condition, the pressboard insulation is sealed in an enclosed metal container and immersed in transformer oil. Over the time, the pressboard insulation will degrade its performance and some part of pressboard polymeric compounds disbursed into its surrounding oil and some parts of oil compounds absorbed into the pressboard. This phenomenon can be analyzed and measured with its degree of polymerization (DP). Where DP is a measure of the chain length of the cellulose macromolecules, and is correlated to the mechanical strength of the paper and also can be correlated to transformer aging assessment. Based on reviews and reports, heat was believed to be the main cause of pressboard degradation in high voltage transformer. The correlation of heat and DP is difficult to obtain while a transformer is under commissioning, as this would need for the transformer to fully dismantle and extract the pressboard at the point of interest; as this is impossible at any circumstances, unless the transformer has undergone forensic investigation if total failure occurred. Therefore, this paper is presenting a technique under accelerated heating process in order to investigate the correlation of degraded paper pressboard and heated transformer oil under an influenced of controlled heat. A newly pressboard paper insulation was cut into pieces and undergone heating process immersed in transformer oil with predetermined heating hours. The pressboard and oil specimens were then put under difference tests, namely DP, furan compound, oil colour, neutralization value and water saturation. The results show good flag above the average until 288 hours heating process with reducing DP value. This give an indication that the heating element was certainly the main parameter of aging process based on the correlation of test parameter versus aging time.

Early studies of transformer winding parameters were focused on the determination via its physical dimensions and empirical formulas. In most cases it is divided into several parts namely coil section pairs, coils distance, disc coils diameter and thickness of insulation. Maxwell’s equations are often the solution to the problem, which satisfy related boundary conditions between conductors for mutual inductance and capacitor equations. Such solutions often led to errors and hence its mathematical model. To counter the problem, it was suggested that such approximations must be conducted with experimental model windings at the same time. Frequency domain measurements and time domain measurements can be conducted to effectively determine these parameters. This in turn will investigate the behaviour of transformer winding electromagnetic transient at high frequency. From theoretical point of view, predominantly capacitive winding model often considered to represent its behaviour at high frequency and will give the results of its initial distribution. Under this consideration, a single phase plain winding is considered for investigation. A single rectangular wave was considered to represent infinitive impinge incident wave, injected at one end of transformer winding and the measured response signals of the wavetail were considered for measurement. The experimental response and modelling results were compared and proved to have high agreement between the two.

Sunlight and heat use various continually changing techniques, including solar thermal and artificial photosynthesis. These mechanisms change their orientation throughout the day as the sun maximizes energy absorption. Solar panels are directed towards the sun by the trackers that can increase solar energy compared to the fixed-angle system. Modification efficiency is improved in any solar system when the tracking system is continuously adjusted to the most favorable angle as the sun crosses the sky. The project presents the development of a solar tracking system using Arduino-UNO that allows the panel to move towards high-intensity sunlight via two LDRs. The monitoring system is implemented to record the data of solar energy parameters and factors affecting its deficiencies using ThingSpeak platform. The result shows the tracking system has efficiencies of 54.74% higher than a fixed system. The monitoring system is practical for analyzing the real-time solar panel competent environmental factors.

Chalcogenide, tin selenide-based thermoelectric (TE) materials are Earth-abundant, non-toxic, and are proven to be highly stable intrinsically with ultralow thermal conductivity. This work presented an updated review regarding the extraordinary performance of tin selenide in TE applications, focusing on the crystal structures and their commonly used fabrication methods. Besides, various optimization strategies were recorded to improve the performance of tin selenide as a mid-temperature TE material. The analyses and reviews over the methodologies showed a noticeable improvement in the electrical conductivity and Seebeck coefficient, with a noticeable decrement in the thermal conductivity, thereby enhancing the tin selenide figure of merit value. The applications of SnSe in the TE fields such as microgenerators, and flexible and wearable devices are also discussed. In the future, research in low-dimensional TE materials focusing on nanostructures and nanocomposites can be conducted with the advancements in material science technology as well as microtechnology and nanotechnology.

In the last few years, intensive research has been done to enhance artificial intelligence (AI) using optimization techniques. In this paper, we present an extensive review of artificial neural networks (ANNs) based optimization algorithm techniques with some of the famous optimization techniques, e.g., genetic algorithm (GA), particle swarm optimization (PSO), artificial bee colony (ABC), and backtracking search algorithm (BSA) and some modern developed techniques, e.g., the lightning search algorithm (LSA) and whale optimization algorithm (WOA), and many more. The entire set of such techniques is classified as algorithms based on a population where the initial population is randomly created. Input parameters are initialized within the specified range, and they can provide optimal solutions. This paper emphasizes enhancing the neural network via optimization algorithms by manipulating its tuned parameters or training parameters to obtain the best structure network pattern to dissolve the problems in the best way. This paper includes some results for improving the ANN performance by PSO, GA, ABC, and BSA optimization techniques, respectively, to search for optimal parameters, e.g., the number of neurons in the hidden layers and learning rate. The obtained neural net is used for solving energy management problems in the virtual power plant system.

In this study, the performance analysis of the thermoelectric-solar (TEM-SA) hybrid energy harvesting system is presented. The proposed system is analyzed for continuous and discontinuous load condition and mobile devices as a load. In this feed forward type of controller, Inverse Dynamic Analysis Input Shaper (IDAIS) is introduced to shape the unsteady response behavior to become stable input and is named as Shapeable MPPT (SMPPT). The experimental analysis is done to verify the performance of the new arrangement proposed circuit of HEHS which is used only one MPPT board. An initial test is made in determining which energy-efficient sources are capable to produce the highest output. Then the device that produces the highest output is connected to the new arrangement proposed circuit incorporated SMPPT unit, the converter, and the energy storage. With constant source supply, full charging time obtained for mobile phone is 4 hours and 30 minutes which is equivalent to the charging period using the normal alternating current sources. Greater focus is then given to the charging time for some types of mobile phones that have different battery capacity mAH. From the verification results, it is found that the load that having lowest mAh values steadily able to reach the full charging period faster than the others.

This paper reviews energy storage systems, in general, and for specific applications in low-cost micro-energy harvesting (MEH) systems, low-cost microelectronic devices, and wireless sensor networks (WSNs). With the development of electronic gadgets, low-cost microelectronic devices and WSNs, the need for an efficient, light and reliable energy storage device is increased. The current energy storage systems (ESS) have the disadvantages of self-discharging, energy density, life cycles, and cost. The ambient energy resources are the best option as an energy source, but the main challenge in harvesting energy from ambient sources is the instability of the source of energy. Due to the explosion of lithium batteries in many cases, and the pros associated with them, the design of an efficient device, which is more reliable and efficient than conventional batteries, is important. This review paper focused on the issues of the reliability and performance of electrical ESS, and, especially, discussed the technical challenges and suggested solutions for ESS (batteries, supercapacitors, and for a hybrid combination of supercapacitors and batteries) in detail. Nowadays, the main market of batteries is WSNs, but in the last decade, the world’s attention has turned toward supercapacitors as a good alternative of batteries. The main advantages of supercapacitors are their light weight, volume, greater life cycle, turbo charging/discharging, high energy density and power density, low cost, easy maintenance, and no pollution. This study reviews supercapacitors as a better alternative of batteries in low-cost electronic devices, WSNs, and MEH systems.

This paper presents a hybrid optimization approach for the enhancement of performance of a piezoelectric energy harvesting system (PEHS). The existing PEHS shows substantial power loss during hardware implementation. To overcome the problem, this study proposes a hybrid optimization technique to improve the PEHS efficiency. In addition, the converter design as well as controller technique are enhanced and simulated in a MATLAB/Simulink platform. The controller technique of the proposed structure is connected to the converter prototype through the dSPACE DS1104 board (dSPACE, Paderborn, Germany). To enhance the proportional-integral voltage controller (PIVC) based on hybrid optimization method, a massive enhancement in reducing the output error is done in terms of power efficiency, power loss, rising time and settling time. The results show that the overall PEHS converter efficiency is about 85% based on the simulation and experimental implementations.

We report on the microelectronic characteristics of a novel hybrid heterojunction device based on a solution processable semiconducting polymer poly(9,9-dioctylfluorenyl-2,7-diyl)- co-(N,N0-diphenyl)-N,N′di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) and p-type silicon (p-Si). The PFB/p-Si heterojunction is prepared by spin coating 20 mg/mL solution of PFB in chloroform on the precleaned polished surface of p-Si substrate. Thermal evaporation of silver (Ag) electrode on top of PFB completes the fabrication of the Ag (90 nm)/PFB (180 nm)/p-Si heterojunction device. Morphology of PFB thin film is studied by using an atomic force microscope (AFM) and scanning electron microscope (SEM), which reveals grains are randomly distributed with slightly different grain sizes and shapes. It leads the film to form nonuniformity and some roughness in its topography that results in limiting the current (I) flow across the film/interface with p-Si. Ultraviolet (UV–vis) absorption and X-ray diffraction (XRD) spectra are measured for optical bandgap and crystal structure analysis of PFB. The key microelectronic parameters—rectification ratio (RR), ideality factor (n), barrier height (Φ_b), series resistance (R_s) and reverse saturation current (I₀)—of the Ag/PFB/p-Si heterojunction are found from current–voltage (I–V) characteristics at room temperature (300 K) in dark conditions (≈0 lux). The Ag/PFB/p-Si heterojunction device exhibits improved microelectronic parameters when compared to those of earlier reported devices that were prepared in the same configuration. This improvement in the device parameters reveals enhancement in the microelectronic properties across the interface/depletion region of the Ag/PFB/p-Si device, which can be attributed to the remarkable electronic properties of PFB such as its relatively high hole mobility and better charge carriers’ conduction. The charge transport mechanisms through the device is also studied. Having the smaller values of I₀ ≈ 7 × 10⁻¹⁰ A and n ≈ 3.23, as well as higher shunt resistance (R_sh) of 32 GΩ for the Ag/PFB/p-Si device suggest its potential for many electronic and optoelectronic applications.