A Review of Metamaterials in Wireless Power Transfer.

Wireless power transfer (WPT) is a technology that enables energy transmission without physical contact, utilizing magnetic and electric fields as soft media. While WPT has numerous applications, the increasing power transfer distance often results in a decrease in transmission efficiency, as well as the urgent need for addressing safety concerns. Metamaterials offer a promising way for improving efficiency and reducing the flux density in WPT systems. This paper provides an overview of the current status and technical challenges of metamaterial-based WPT systems. The basic principles of magnetic coupling resonant wireless power transfer (MCR-WPT) are presented, followed by a detailed description of the metamaterial design theory and its application in WPT. The paper then reviews the metamaterial-based wireless energy transmission system from three perspectives: transmission efficiency, misalignment tolerance, and electromagnetic shielding. Finally, the paper summarizes the development trends and technical challenges of metamaterial-based WPT systems.

Metamaterials for Wireless Power Transfer: A New Open Special Issue in Materials.

Metamaterials for Wireless Power Transfer is a new open Special Issue of Materials, which aims to publish original and review papers on new scientific and applied research and make great contributions to the finding and understanding of the use of metamaterials for wireless power transfer (WPT) and related fundamentals, characterization, and applications [...].

Matrix Metamaterial Shielding Design for Wireless Power Transfer to Control the Magnetic Field.

A wireless power transfer (WPT) system can bring convenience to human life, while a leakage magnetic field around the system can be harmful to humans or the environment. Due to application limitations of aluminum and ferrite materials, it is urgent to find a new type of shielding material. This paper first proposes a detailed model and analysis method of the matrix shielding metamaterial (MSM), which is applied to the low-frequency WPT system in an electric vehicle (EV). The MSM is placed on the top and side of the EV system to shield the magnetic field from all positions. To explore its function, a theoretical analysis of the MSM is proposed to prove the shielding performance. The simulation modeling and the design procedure of the MSM are introduced. Moreover, the prototype model of the WPT system with the MSM is established. The experimental results indicate that the magnetic field is controlled when the MSM is applied on the top or side of the EV-WPT system. The proposed MSM has been successfully proven to effectively shield the leakage magnetic field in the WPT system, which is suitable for the kHz range frequency.

Enhancing the Stability of Medium Range and Misalignment Wireless Power Transfer System by Negative Magnetic Metamaterials.

The misalignment of the resonant coils in wireless power transfer (WPT) systems causes a sharp decrease in transfer efficiency. This paper presents a method which improves the misalignment tolerance of WPT systems. Based on electromagnetic simulations, the structural unit parameters of the electromagnetic material were extracted, and an experimental prototype of a four-coil WPT system was built. The influence of electromagnetic metamaterials on the WPT system under the conditions of lateral misalignment and angular offset was investigated. Experiments showed that the transfer efficiency of the system could be maintained above 45% when the transfer distance of the WPT system with electromagnetic metamaterials was 1 m and the resonant coils were shifted laterally within one coil diameter. Furthermore, the system transfer efficiency could be stabilized by more than 40% within an angle variation range of 70 degrees. Under the same conditions, the transfer efficiency of a system without electromagnetic metamaterials was as low as 30% when lateral migration occurred, and less than 25% when the angle changed. This comparison shows that the stability of the WPT system loaded with electromagnetic metamaterials was significantly enhanced.

Simultaneous normal and parallel incidence planar left-handed metamaterial.

We investigate numerically the negative refraction of a simultaneous normal and parallel incidence planar left-handed metamaterial (LHM) in this paper. This LHM is comprised of fourfold C-shaped rings, which are printed on both sides of the substrates symmetrically, and it can exhibit left-handed properties with electromagnetic wave incident in three different directions. The retrieved result and the simulated result verify the left-handed properties of the fourfold C-shaped metamaterial very well. Then the different electric responses of the normal and parallel incidence cases to the incident electromagnetic wave are discussed, and it is due to the different distribution of the induced currents in the metallic wires.

Numerical studies of a low-loss and broad-pass-band single-sided-structure left-handed metamaterial.

A single-sided structure left-handed metamaterial (LHM), of which the symmetric paired split-ring resonators are connected directly through cut wires, is discussed in this paper. This connected single-sided LHM can exhibit a low loss and broad negative refraction passband. Good agreement of the retrieved result and the simulated result verify the above conclusion by comparison with the in-plane case and the off-plane case [T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, Phys. Rev. Lett. 93, 107402 (2004)].

Effect of Non-Coal Heating and Traditional Heating on Indoor Environment of Rural Houses in Tianjin.

In order to understand the effect of the non-coal heating and the traditional coal-fired heating on the indoor environment of the rural houses, the humidity environment and indoor air quality in several households were investigated during the heating period in Beichen District and Wuqing District of Tianjin, China. The results showed that the indoor average temperature for the heating by the electricity and the natural gas was higher than that by the traditional coal fire. The indoor relative humidity for the heating by the electricity and the natural gas was lower than that by the traditional coal fire. The indoor air quality (IAQ) for the heating by the electricity and the natural gas was better than that by the traditional coal fire. For traditional coal-fire heating households, the indoor pollutant emission (CO emission) by using the clean coal was lower than that by using the raw coal. The indoor ventilation rate which was an important parameter for the indoor air quality was generally poor in winter. The total volatile organic compounds (TVOC) emission in the indoors of the coal-fired heating households was generally higher than that of the non-coaled heating households.

Filamentary streamer discharges in argon at atmospheric pressure excited by surface plasmon polaritons.

This paper describes a microwave plasma jet in an argon atmosphere capable of generating filamentary streamer discharges within the entire quartz tube excited by surface waves of surface plasmon polaritons (SPPs) located in the tube. Several discharge streamers are immediately produced at the end of the copper wire when incident power reaches 20 W. From simulations, the wavelength of the surface wave was found to be approximately 5.7 cm. Although the developing streamers induce E-field enhancements favoring discharging, more streamer bifurcations requiring additional energy to maintain discharging diminish the resonant enhanced E-field. The underlying mechanism of the proposed plasma jet is resonant excitation of SPPs and its interaction with plasmas.