  Near-field heat engines are devices that convert the evanescent thermal field
supported by a primary source into usable mechanical energy. By analyzing the
thermodynamic performance of three-body near-field heat engines, we demonstrate
that the power they supply can be substantially larger than that of two-body
systems, showing their strong potential for energy harvesting. Theoretical
limits for energy and entropy fluxes in three-body systems are discussed and
compared with their corresponding two-body counterparts. Such considerations
confirm that the thermodynamic availability in energy-conversion processes
driven by three-body photon tunneling can exceed the thermodynamic availability
in two-body systems.
