Generating electricity requires generating a potential difference, for which there are not that many methods, barring major advances in physics. Methods such as electromagnetic (the method used for steam power), photovoltaic (solar cells), chemical (batteries, bioelectric), piezoelectric, thermo/pyroelectric, electrostatic. The problem with the latter, more advanced technologies, is that they do not scale easily to the Megawatt scale, required by current centralized generation technologies.

Unless we develop a portable nuclear fusion reactor, the energy available by distributed generation (mostly solar, wind, biomass, maybe using the exotic physics) is low, and would require major changes in current lifestyle to be sustainable.

The principle of conservation of energy still applies – you can not get energy out of nothing. With steam turbine (and solar cell etc.) efficiencies in the >=20% range, there is not much to gain by more efficient generation methods – certainly not an order of magnitude.