It is not possible at the macro scale, at the nano scale I would not be so certain ... see the casimir effect!
Heck, the Casimir effect respects energy conservation, when measured in physics, no offense to uluberlus who distort everything !!
The Casimir effect is initially the Van der Walls interaction for the case of 2 molecules not too far apart !!
Van der Waals, also quantum, with virtual photons, conserves energy and is the basis of solid, liquid to vapor passage !!Casimir is what becomes Van der Waals at a greater distance, when the propagation time of virtual photons becomes long !!
So it conserves energy !!
http://en.wikipedia.org/wiki/Van_der_Waals_forceThe London-van der Waals forces are related to the Casimir effect for dielectric media, the former being the microscopic description of the latter bulk property. The first detailed calculations of this were done in 1955 by EM Lifshitz. [2] [3]
At the nano level quantum mechanics describes the passage very quickly through high energy states (virtual), but at the end, in long time, the energy is conserved !!
Thus, for nano, we can go through higher energies by passing barriers, very quickly as in the tunnel effect, but in the end the energy is preserved !!
Radioactivity is a tunnel effect with passage through a barrier which if high, gives radioactive life times of billions of years !!
The chemical reactions, the photoelectric effect are quantum, with energy of the photons of the vacuum, with passage over narrow barriers of higher energy, virtual states, of very short time, but which conserve energy, like a photovoltaic panel prove it all the time !!
But Casimir, quantum, vacuum energy, respect the conservation of energy on our scale for an engine or heating !!
All is not resolved, and it remains to be discovered, but the current experimental facts explained will remain with the same explanations but more complex at very high virtual energies which remain unknown and almost inaccessible, and studied at LEP in Geneva.