We analyze the time-resolved energy transport and the entropy production in
ac-driven quantum coherent electron systems coupled to multiple reservoirs at
finite temperature. At slow driving we formulate the first and second laws of
thermodynamics valid at each instant of time. We identify heat fluxes flowing
though the different pieces of the device and emphasize the importance of the
energy stored in the contact and central regions for the second law of
thermodynamics to be instantaneously satisfied. In addition, we discuss
conservative and dissipative contributions to the heat flux and to the entropy
production as a function of time. We illustrate these ideas with a simple model
corresponding to a driven level coupled to two reservoirs with different
chemical potentials.Comment: 12 pages, 5 figures; v2: discussions improved, references adde