  Frequency up-conversion of few low-energy photons into a single high-energy
photon, greatly contributes to imaging, light sources, detection and other
fields of research. However, it offers negligible efficiency when up-converting
many photons. This is because coherent process are fundamentally limited due to
momentum conservation requirements, while in incoherent up-conversion the
finite intermediate states lifetime requires huge intensities.
Thermodynamically, conventional incoherent up-conversion is driven by the
internal energy of the incoming photons. However, a system can also drive work
through change in its collective properties such as entropy. Here we
experimentally demonstrate entropy driven ten-fold up-conversion from 10.6{\mu}
to 1{\mu}m at internal efficiency above 27% and total efficiency above 10%. In
addition, the emitted radiance at 1{\mu}m exceeds the maximal possible
Black-Body radiance of our device, indicating emitter's effective-temperature
that is considerably above the bulk-temperature. This work opens the way for
up-conversion of thermal-radiation, and high-temperature chemistry done at
room-temperature.
