Filling a cavity with zero-point electromagnetic radiation

In the present contribution we analyse, within the frame of a particular form of classical electrodynamics, a simple thought experiment performed by an idealized heat engine bathed in zero-point (ZP) electromagnetic radiation. In contrast to the usual forms of heat engines driven by electromagnetic radiation, all partitions of our engine are made of more realistic material having an upper frequency cut-off. Analysing the operation of such an engine at T=0, a possible mechanism of filling real cavities with ZP radiation based on Doppler's effect has been suggested.