Further research finds schematics and theory of operation some translated to English. Seems to work something like the Tom Bearden electromagnetic generator, except with an air core operating at higher frequencies. In a nutshell, the harvestable energy due to a rapid change in a magnetic field is limited by the rate of change of the magnetic field, which can be greater than the amount of energy needed to induce the change. This is no different than an off the shelf standard heat pump with a COP greater than one, except that instead of pumping heat, these devices pump electrons.