The paper investigates the feasibility of using long-lifetime resonant electromagnetic states with localized, slowly-evanescent field patterns for efficient wireless non-radiative mid-range energy transfer. The authors explore the potential of "strong coupling" between two medium-range distant states to achieve practical energy transfer. Through detailed theoretical and numerical analyses, they demonstrate that such a scheme can be effective, provided the system operates in a regime of strong coupling compared to intrinsic loss rates. The study focuses on two types of resonant structures: dielectric disks and capacitively-loaded conducting-wire loops. For dielectric disks, high-$Q$ whispering-gallery modes are achieved, and for conducting-wire loops, resonant inductive modes are considered. The influence of extraneous objects on the resonances is analyzed using perturbation theory, showing that the proposed scheme is robust to small perturbations but sensitive to large perturbations from high-loss objects. The efficiency of the energy-transfer scheme is evaluated, and it is shown that the working efficiency can be optimized to over 17% for practical applications. The authors conclude that this scheme has potential for various modern applications, including powering robots and computers in factory rooms, electric buses on highways, and optical interconnects for CMOS electronics.The paper investigates the feasibility of using long-lifetime resonant electromagnetic states with localized, slowly-evanescent field patterns for efficient wireless non-radiative mid-range energy transfer. The authors explore the potential of "strong coupling" between two medium-range distant states to achieve practical energy transfer. Through detailed theoretical and numerical analyses, they demonstrate that such a scheme can be effective, provided the system operates in a regime of strong coupling compared to intrinsic loss rates. The study focuses on two types of resonant structures: dielectric disks and capacitively-loaded conducting-wire loops. For dielectric disks, high-$Q$ whispering-gallery modes are achieved, and for conducting-wire loops, resonant inductive modes are considered. The influence of extraneous objects on the resonances is analyzed using perturbation theory, showing that the proposed scheme is robust to small perturbations but sensitive to large perturbations from high-loss objects. The efficiency of the energy-transfer scheme is evaluated, and it is shown that the working efficiency can be optimized to over 17% for practical applications. The authors conclude that this scheme has potential for various modern applications, including powering robots and computers in factory rooms, electric buses on highways, and optical interconnects for CMOS electronics.