Search Results (5)

Permanent magnet eddy current heating as a new type of wind energy utilization method, which is energy-saving, is zero-emission, and involves no pollution and a high utilization of wind energy, has attracted more and more attention. This paper deals with the simulation and optimal design of a permanent magnet eddy current heater (PMECH) driven by wind. Solid steel, closed-slot, and open-slot PMECH are proposed, and corresponding 2D finite element method (FEM) models are established. Using the skin depth concept, numerical analyses are conducted on the influence of the number, size, and position of copper strips on the thermal power of closed-slot and open-slot PMECHs, and the thermal power growth compared to solid steel PMECH. The results showed that there is an optimal value for stator wall thickness. When the air-gap length is 0.5 mm and the rotation speed is 200 and 1000 rpm, the optimal stator wall thickness is 16 and 9 mm, respectively. Compared to the influence of conductivity on thermal power, the influence of permeability is more significant. Compared with solid steel PMECH, both closed-slot and open-slot PMECH in a low-speed region can effectively improve thermal power, and the open slot has more obvious advantages. The maximum values of the thermal power growth (TPG) and thermal power growth rate (TPGR) of the closed-slot PMECH are 1.57 kW and 120.15%, respectively. The maximums of TPG and TPGR of the open-slot PMECH are 2.58 kW and 175.08%, respectively. The experimental results prove the validity of the analytical calculation. Full article

Transient response performance and steady-state operation performance are the two most important performance indicators of a motor drive system. In order to solve these two problems, this study proposes a new induction motor (IM) model, and then designs a new simplified linearization controller method. First, the tangential force that determines the transient process of the motor is represented by electromagnetic torque, and the radial force is represented by reactive torque. Then, the dual-torque model of IM is derived, which not only accurately shows the rotating air-gap magnetic field through the amplitude and rotating angular frequency, but also visually demonstrates the physical essence of the transient process of IM. Then, this study proposes a simplified feedback linearization method without the analysis of zero dynamic. In addition, a time-scale hierarchical control system is designed to reduce the ripple caused by the coupling of different time-scale variables. The experimental results show that the steady-state torque ripple of the proposed method is 65% lower than that of RFOC, and the torque response speed is 10% higher than that of DTC. Full article

There are many islands without full access to electricity around the world. These energy-poor regions generally have drinking water supply issues too. Renewable energy-powered desalination units can convert seawater to freshwater by using such as oceanic wave energy to mitigate the water limitation in small islands. A novel wave-powered floating desalination system (WavoWater) was proposed for easy on-site deployment and minimal environmental impact. WavoWater can produce freshwater using a vacuum-applied air-gap membrane distillation (AGMD) system, and the heat needed for the AGMD is provided through a heat pump powered by wave energy. Small-scale experiments were conducted to estimate the water generation rate of the vacuum-applied AGMD, and the WavoWater system modeling was developed based on the experimental results and wave data observed near the City of Newport, OR, USA. Fast Fourier transform was applied to estimate the wave energy spectrum in a random sea wave state. It was evaluated that 1 m-diameter WavoWater can produce 12.6 kg of fresh water per day with about 3.1 kWh of wave energy. With the performance evaluation, the aspects of zero discharging and minimal environmental impact were also highlighted for the stand-alone wave-powered desalination system. Full article

A zero-energy building (ZEB) requires an innovative integration of technologies, in which windows play a paramount role in energy reduction, storage, and generation. This study contributes to four innovative designs of sliding smart windows. It integrates air-gap (AG), phase change material (PCM), photovoltaic (PV), and vacuum glazing (VG) technologies. These smart sliding windows are proposed to generate electricity along with achieving efficient thermal insulations and heat storage simultaneously. A two-dimensional multiphysics thermal model that couples the PCM melting and solidification model, PV model, natural convection in the cavity, and the surface-to-surface radiation model in the vacuum gap are developed for the first time. The model is validated with data in the literature. The transient simulations were carried out to investigate the thermo-electrical performance of a window with an area of 1 m by 1 m for the meteorological conditions of Kuwait city on the 10th of June 2018, where the window was oriented to south direction. The results showed that the total solar heat energy gain per unit window area is 2.6 kWh, 0.02 kWh, 0.22 kWh, 1.48 kWh, and 0.2 kWh for the double AG, AG + PV + PCM + VG, PV + PCM + VG, AG + PV + PCM, and the ventilated AG + PV + PCM + VG, respectively. The results elucidate the advantages of the integration of VG in this integrated sliding smart window. The daily generated PV electrical energy in these systems is around 1.3 kWh, 1.43 kWh, and 1.38 kWh for the base case with double AG, PV + PCM + VG, and the ventilated AG + PV + PCM + VG respectively per unit window area. Full article

In this paper, we propose a novel study concerning the future use of a zero-airgap induction motor in applications related to transmission oil pumps. The name of the machine comes from the fact that the rotor touches the stator as it spins. The use of such an eccentric motor provides the possibility to remove the mechanical part that is typically found in the transmission oil pump, increasing its efficiency in this way. We focused on determining the optimum variant of a zero-airgap small power induction motor from the point of view of the electrical and mechanical performance. As such, 18 topologies of induction motors with various numbers of pole pairs and rotor bars were designed and numerically analyzed. For the best variant from each category, different eccentricities were considered to evaluate this effect over the performances of the motors. For the best candidate, various analyses were performed in order to demonstrate the validity of this solution for the proposed application. Elements regarding the thermal analysis of this structure are also presented here. Full article