A method of transferring energy comprising: providing a first electromagnetic resonator structure receiving energy from an external power supply, said first resonator structure having a first resonant frequency ω 1 , resonant wavelength λ 1 , resonance width Γ 1 , a first Q-factor Q 1 , and a characteristic size L 1 , wherein said first resonator structure comprises a capacitively-loaded conducting-wire loop, where the characteristic size L 1 is the radius of the loop; providing a second electromagnetic resonator structure being positioned distal from said first resonator structure, at closest distance D, said second resonator structure having a second resonant frequency ω 2 , resonant wavelength λ 2 , and resonance width Γ 2 , a second Q-factor Q 2 , and a characteristic size L 2 , wherein said second resonator structure comprises a capacitively-loaded conducting-wire loop where the characteristic size L 2 is the radius of the loop, wherein the two said frequencies ω 1 and ω 2 are close to within the narrower of the two resonance widths Γ 1 and Γ 2 , and transferring energy non-radiatively between said first resonator structure and said second resonator structure, said energy transfer being mediated through coupling of their resonant-field evanescent tails, and the rate of energy transfer between said first resonator and said second resonator being denoted by κ, wherein Q 1 >200 and Q 2 >200, and κ/sqrt(Γ 1 ∗Γ 2 )>2 and D/L 2 >1,2,3,5, wherein non-radiative means D is smaller than each of the resonant wavelengths λ 1 and λ 2 , wherein the second resonator structure is part of a mobile wireless receiver. providing a first electromagnetic resonator structure receiving energy from an external power supply, said first resonator structure having a first resonant frequency ω 1 , resonant wavelength λ 1 , resonance width Γ 1 , a first Q-factor Q 1 , and a characteristic size L 1 , wherein said first resonator structure comprises a capacitively-loaded conducting-wire loop, where the characteristic size L 1 is the radius of the loop; providing a second electromagnetic resonator structure being positioned distal from said first resonator structure, at closest distance D, said second resonator structure having a second resonant frequency ω 2 , resonant wavelength λ 2 , and resonance width Γ 2 , a second Q-factor Q 2 , and a characteristic size L 2 , wherein said second resonator structure comprises a capacitively-loaded conducting-wire loop where the characteristic size L 2 is the radius of the loop, wherein the two said frequencies ω 1 and ω 2 are close to within the narrower of the two resonance widths Γ 1 and Γ 2 , and transferring energy non-radiatively between said first resonator structure and said second resonator structure, said energy transfer being mediated through coupling of their resonant-field evanescent tails, and the rate of energy transfer between said first resonator and said second resonator being denoted by κ, wherein Q 1 >200 and Q 2 >200, and κ/sqrt(Γ 1 ∗Γ 2 )>2 and D/L 2 >1,2,3,5, wherein non-radiative means D is smaller than each of the resonant wavelengths λ 1 and λ 2 , wherein the second resonator structure is part of a mobile wireless receiver. <EOS>