Capacitive power transfer for maritime electrical charging applications

Wireless power transfer can provide the convenience of automatic charging while the ships or maritime vehicles are docking, mooring, or in a sailing maneuver. It can address the challenges facing conventional wired charging technologies, including long charging and queuing time, wear and tear of the physical contacts, handling cables and wires, and electric shock hazards. Capacitive power transfer (CPT) is one of the wireless charging technologies that has received attention in on-road electric vehicle charging applications. By the main of electric fields, CPT offers an inexpensive and light charging solution with good misalignment performance. Thus, this study investigates the CPT system in which air and water are the separation medium for the electrical wireless charging of small ships and unmanned maritime vehicles. Unlike on-road charging applications, air or water can be utilized as charging mediums to charge small ships and unmanned maritime vehicles. Because of the low permittivity of the air, the air-gapped capacitive coupling in the Pico Farad range requires a mega-hertz operating frequency to transfer power over a few hundred millimeters. This study examines an air-gapped CPT system to transfer about 135 W at a separation distance of 50 mm, a total efficiency of approximately 83.9%, and a 1 MHz operating efficiency. At 13.56 MHz, the study tested a shielded air-gapped CPT system that transfers about 100 W at a separation distance of 30 mm and a total efficiency of about 87%. The study also examines the underwater CPT system by submerging the couplers in water to increase the capacitive coupling. The system can transfer about 129 W at a separation distance of 300 mm, a total efficiency of aboutapproximately%, and a 1.1 MHz operating efficiency. These CPT systems can upscale to provide a few kW for small ships and unmanned maritime vehicles. But they are still facing several challenges that need further investigations

An efficient up-link load reduction model based on clustering in vanets

Vehicular Ad Hoc Networks (VANETs) enable communication between vehicles to avoid the accident. Cluster is a technique in VANETs used to group vehicles. The aim of this thesis is to mitigate uplink load at Base-Stations (BSs) resulted from the following: first, increased number of vehicles in the urban city leads to an increase in the number of cluster head (CH) in the network while each CH required uplink channel from BS. Second, increased vehicles mobility makes the clusters unstable and try to reserve another uplink channel from the BS. Third, the handover problem in the cell edges makes the CHs try to reconnect with the BS. Fourth, duplicated information sent from CHs to the BSs at the intersections make the BSs loaded by unnecessary information. This study proposed an Efficient Up-link Load Reduction (EULR) model to mitigate the uplink load at BSs. EULR model consisted of three parts: the first part, two novel algorithms Smart CH Election (SCHE) and Hybrid Cluster-Head Election (HCHE) to increase cluster stability and reduce the number of CHs changes in the network by selecting the best vehicle as cluster head (CH) based on two dynamic thresholds. Second part, Intelligent Cluster-Head (ICH) method is proposed which aims to mitigate handover problem of a CHs at the cell edge of a neighbor's BSs by transferring uplink connection to the CH that has the highest RSS and hence reducing load at the BSs. Last part, Dynamic Multi-Agent (DMA) method is proposed to avoid duplicated information transmission from CHs at intersections to the BSs. The DMA method filtered the CHs information by sending only new information to the BS; therefore, this method helped to reduce the load at BSs. Performance of the EULR model is evaluated through simulation with real-time datasets. Overall, the EULR model reduces the number of CHs by 9.53%, increased CHs stability by 40.38%, achieved less packet loss by 26.81% and reduced the duplicated information at the intersection by 81% than the previous related works. Finally, the proposed methods have shown significant network performance results compared to previous related works as stated in this thesis

A Numerical Investigation of Thermal Airflows over Strip Fin Heat Sinks

The benefits of using strip fin heat sinks (SFHSs) where the cross-sectional aspect ratio of the fins lie between those for plate fins (high aspect ratio) and pins fins (aspect ratio≈ 1) are explored computationally, using a conjugate heat transfer model. Results show that strip fins provide another effective means of enhancing heat transfer, especially when staggered arrangements of strip fins are used. A detailed parameter investigation demonstrates that perforating the strip fins provide additional improvements in terms of enhanced heat transfer, together with reduced pressure loss and heat sink mass. Results are also given which show that, for practical applications in micro-electronics cooling, perforated SFHSs offer important benefits as a means of achieving smaller processor temperatures for reduced mechanical power consumption

An appraisal of the thermal decomposition mechanisms of ILs as potential lubricants

Ionic liquid (IL) lubricants are rapidly seeing increased use as either base lubricants or additives for a wide range of functionalities. This study considers the thermal stability of the ILs with the emphasis being their use as potential lubricants. The effect of IL chemistry, including anion chain length, cation chain length, anion type, and cation type, on their thermal stability is studied. The decomposition mechanism as a function of time and temperature is considered. Five ILs are studied by utilising both thermogravimetric analysis (TGA) for the dynamic thermal decomposition and Fourier transform IR spectroscopy (FTIR) for the static thermal decomposition. For static thermal decomposition, both time and temperature are varied. The results show that the variation of IL chemistry directly influences their thermal stability. The increase of either cation or anion chain length decreases their thermal stability. Both anion and cation type have a significant influence on the thermal stability

Analysis of OFDM and WPOFDM Systems in Different Wireless Multipath Channels

In this paper, the performance analysis for orthogonal frequency division multiplexing (OFDM) and wavelet packet based OFDM (WPOFDM) systems over different wireless multipath channels has been investigated. The bit error rate (BER) performance for both systems is shown to be comparable and even at times better for OFDM especially in frequency selective fading channel at high values of S/N. Simulation results also show a significant enhancement for WPOFDM in terms of spectral efficiency and side-lobes suppression comparing to OFDM. Keywords: OFDM, WPOFDM, PSD, BER performance, wavelet filters, fading channels.

Reactivity of oil‐soluble IL with silicon surface at elevated temperature

The reactivity of an oil‐miscible ionic liquid, phosphonium phosphate (PP), and the common anti‐wear additive zinc dialkyl dithio phosphate (ZDDP) with a solid surface at elevated temperature in the absence of any tribological motion is investigated. Understanding the thermal film build up, composition, and relative thickness will help in the understanding of lubrication mechanisms once tribological effects are introduced. Attenuated total reflection–Fourier transform infrared (ATR‐FTIR), scanning electron microscopy–energy dispersive spectroscopy (SEM‐EDS), and X‐ray photoelectron spectroscopy (XPS) are employed to characterise silicon surfaces before and after the experiments in terms of surface chemistry and surface morphology. The results show that both additives react with the silicon surface to produce thermal films. However, ZDDP forms a thicker film. PP reacts with the silicon and forms a thermal film, but the reaction rate is self‐limited such that an increase of time to 24 hours does not significantly increase the film thickness

A Review of Power Converters for Ships Electrification

Fully electric ships have become popular to meet the demand for emission-free transportation and improve ships' functionality, reliability, and efficiency. Previous studies reviewed the shipboard power systems, the different types of shipboard energy storage devices, and the influences of the shore-to-ship connection on ports' electrical grid. However, the converter topologies used in the electrification of ships have received very little attention. This article presents a comprehensive topological review of currently available shore-to-ship and shipboard power converters in the literature and on the market. The main goal is to anticipate future trends and potential challenges to stimulate research to accelerate more efficient and reliable electric ships