Upper bound efficiencies for work generation from the energy of confined systems of quantum particles

Abstract

The maximum amount of work extraction from confined particles energy is treated for a larger class of particles than the usual case of boltzons and photons. The treatment does not restrict to exergy evaluation since real-world processes take place in finite time. Both reversible and endoreversible work extraction is considered. The maximum extractable work is estimated in case that the equilibrium of the particle system with the environment is not reached during work extraction. This result is different for bosons or fermions having non-zero rest mass in the non-relativistic limit and for zero rest mass or non-zero rest mass particles in the extreme relativistic limit, respectively. For particles obeying spontaneous creation and annihilation the exergy content cannot be properly defined. The exergy concept makes sense for confined particles for which very slow (flowing) filling and emptying processes may be imagined. The Carnot efficiency is not a proper upper bound for the conversion of confined thermal radiation into work but it may be used as a safe superior (but less accurate) limit in this case.