Second law aspects of solar energy conversion
The thermodynamics of solar thermal energy conversion installations is reviewed in the spirit of second law analysis. A review of the equilibrium thermodynamics of radiation as a photon gas system, and with an outline of benchmark reversible and irreversible processes involving thermal radiation are given. The controversy regarding the exergy content of enclosed blackbody radiation is elucidated in a new unifying theory that shows the relationship between `radiation' as an exergy source, and the `sun and ambient temperature reservoirs' as the combination that is ultimately responsible for the production of exergy. The maximization of exergy extraction per unit of collector area is discussed. The solutions to this basic problem are reviewed in the many contexts in which the problem has been posed; single-temperature collectors, infinite series of monochromatic receivers, unconcentrating collectors, convectively cooled collectors and, finally, concentrating collectors cooled by both convection and radiation
