Experimental Results of Ultrahigh-Efficiency Wireless Power Transfer Using Extremely High-Quality Factor Superconducting Coil With Double-Sided Coated Conductor Tape

Extremely high-quality factor (
Q
) superconducting coils comprising two conventional high-temperature superconducting (HTS) coated conductor (CC) tapes, the use of which substantially improves the power transfer efficiency (PTE) of resonant coupling wireless power transfer (WPT), have been developed. In this article, a method for joining two HTS CC tapes by using dielectric film tape was developed. A styrene foam coil-support configuration that has lower effective dielectric loss was also developed. The skin effect of the Ag protection layer was suppressed by making it thinner than the conventional one. A coil using the proposed tape had a measured
Q
(resonant frequency: 8.0 MHz) of around 20 000, which is about 20 times that of one using Cu tape. Measurement of the PTE of a WPT system using coils fabricated using the proposed tape for transmitting and receiving demonstrated that the use of coils with an extremely high
Q
enables a WPT system to achieve a transfer distance much greater than that of a comparable system with Cu coils. Measured PTE of the system using such coils and one using Cu coils were 90% and 28% at a transfer distance of 80 cm. This achievement opens the door to new high-frequency applications of HTS CC tape such as using if for WPT.