Wireless energy transfer systems

A system, comprising:

• a source resonator having a Q-factor Q1 and a characteristic size x1, and a second resonator having a Q-factor Q2 and a characteristic size x2, and located a distance D from the source resonator;
• wherein the source resonator and the second resonator are coupled to exchange energy wirelessly among the source resonator and the second resonator;
• and
• wherein √{square root over (Q1Q2)} is greater than 100, and wherein at least one of the resonators is enclosed in a low loss tangent material.

A system, comprising:

• a source resonator having a Q-factor Q1 and a characteristic size x1, and a second resonator having a Q-factor Q2 and a characteristic size x2, and located a distance D from the source resonator;
• wherein the source resonator and the second resonator are coupled to exchange energy wirelessly among the source resonator and the second resonator, and wherein √{square root over (Q1Q2)} is greater than 100;
• and
• wherein at least one of the resonators includes a coil of a plurality of turns of a conducting material connected to a network of capacitors, wherein the plurality of turns are in a common plane, and wherein a characteristic thickness of the at least one of the resonators is much less than a characteristic size of the at least one of the resonators.