  We study the thermodynamics of near-field thermal radiation between two
identical polar media at different temperatures. As an application, we consider
an idealized energy harvesting process from sources at near room temperature at
the nanoscale. We compute the maximum work flux that can be extracted from the
radiation in the near-field regime and compare it with the corresponding
maximum work flux in the blackbody regime. This work flux is considerably
higher in the near-field regime. For materials that support surface phonon
polaritons, explicit expressions for the work flux and an upper bound for the
efficiency as functions of the surface wave frequency are obtained.

Mesoscale and Nanoscale Physics;Statistical Mechanics