Energy Acquisition of Solar-Powered Joint-Wing Aircraft Considering Mismatch Power Loss

Solar-powered aircraft can perform long-term flights with clean solar energy. However, the energy derived from solar irradiation is influenced by the time of year and latitude, which limits the energy acquisition ability of solar aircraft with a straight-wing configuration. Hence, unconventional configurations based on increasing wing dihedral to track the sun are proposed to improve energy acquisition at high-latitude regions in winter, which may involve power loss caused by mismatch in the photovoltaic system. However, mismatch loss is seldom considered and may cause energy to be overestimated. In this paper, the energy acquisition characteristics of a joint-wing configuration are presented based on the simulation of an energy system to investigate the mismatch power loss. The results indicate a 4~15% deviation from the frequently used estimation method and show that the mismatch loss is influenced by the curved upper surface, the severity of shading and the circuit configuration. Then, the configuration energy acquisition factor is proposed to represent the energy acquisition ability of the joint-wing configuration. Finally, the matching between the aircraft configuration and flight trajectory is analyzed, demonstrating that the solar-powered aircraft with an unconventional wing configuration is more sensitive to the coupling between configuration and trajectory.

Polarization Properties of Obliquely Incident EM Waves in Nonuniform Weakly Ionized Dusty Plasma

Effects of nonuniform weakly ionized dusty plasma on the polarization properties of obliquely incident electromagnetic (EM) waves were theoretically investigated in this paper. The dielectric coefficient of magnetized dusty plasma is obtained based on the Bhatnagar–Gross–Krook collision model. Then, the effects of external magnetic field, dust radii, and density on the polarization mismatch loss of obliquely incident EM waves in the L-band were analyzed using the equivalent impedance method. Results indicate that the larger the external magnetic field, the greater the polarization mismatch loss. In addition, we also found that dusty particles alleviate the deterioration of the polarization state significantly; regulating and controlling dust radius and density can avoid polarization reversal and reduce the polarization mismatch loss. We further analyzed the variation of the polarization state under different reentry heights. Our analysis reveals interesting features concerning polarization properties of obliquely incident EM waves, which provide an important theoretical basis for information reception in the plasma sheath containing ablative particles.

A Jigsaw Puzzle based Reconfiguration Technique for Enhancing Maximum Power in Partial Shaded Hybrid Photovoltaic Array

The Photovoltaic (PV) module subjected to partial shading exhibits multiple peaks in the power-voltage characteristics leading to mismatch losses. This loss is a function of module interconnection, shading area and shading pattern. The hybrid configuration has found to be superior to improve the performance of the PV array during partial shading conditions. This work aims to minimize the mismatch loss by using an optimized jigsaw puzzle based reconfiguration technique. The physical position of the modules is rearranged based on the jigsaw puzzle pattern without altering the electrical connections. The performance of the proposed jigsaw puzzle pattern is configured on different interconnection schemes like total-cross-tied, series-parallel total-cross-tied, bridge-link total-cross-tied and honey comb total-cross-tied. For the different shading patterns, the performance of the proposed reconfiguration technique is compared with the existing puzzle based reconfiguration technique schemes such as ken-ken, skyscraper, odd-even and latin square in terms of global maximum power point, power loss, mismatch loss, fill factor, execution ratio and performance enhancement ratio. To validate the results, the performance of the proposed reconfiguration technique is tested in MATLAB/Simulink environment and experiment setup for a 4x4 PV array. The proposed jigsaw puzzle based reconfiguration technique mitigates the occurrence of multiple local power point on the power-voltage characteristics. Hence, the simulation results show the proposed jigsaw based reconfiguration technique improves the output power by 14.01% compared to the existing reconfiguration technique under partial shaded conditions. The effectiveness of the jigsaw puzzle arrangement is also validated experimentally and the results are presented in this paper.

Grating Coupler Design for Vertical Light Coupling in Silicon Thin Films on Lithium Niobate

In this paper we provide a design for a vertical grating coupler for a silicon thin film on lithium niobate. The parameters-such as the cladding layer thickness of lithium niobate, fiber position, fiber angle, grating period, and duty cycle are analyzed and optimized to reduce the mode mismatch loss and the internal reflections. The alignment tolerances, for the grating coupler parameters, are also simulated and evaluated. We determine that our simulated grating coupler exhibits high efficiency, enhanced light coupling, and high alignment tolerance.