Article,
On the exergy of radiation
Solar Energy, (2003)
Abstract
In the domain of heat radiation, and particularly of solar energy
use, the notion of exergy (or alternatively entropy) of radiation
has given rise to a fairly abundant literature; unfortunately, incoherencies
and discrepancies between the various authors could lead to a complete
disuse of the notion in this context. The aim of this paper is to
contribute to a clarification of this issue. We propose here a derivation
of the exergy of radiation, based solely on classical thermodynamics
notions, making thus possible a ready check of the validity of the
results. Results are given first for the blackbody case, then extended
to a radiation with arbitrary spectrum. Finally, application of the
notion of radiation entropy to a few simple examples shows the consistency
of this notion with some well-known physical laws, and can even give
some insight into the real signification of these laws.
