Second law and radiation

The available energy of thermal radiation and solar radiation is examined in this paper. The extension of the available energy concept to the evaluation of the potential energy conversion in solar converters is outlined. The fundamental question discussed is: How much of a given solar radiation flux is convertible to thermodynamic work? The basic relations for evaluating the available energy in radiation processes are developed. The effects of both the spectral and spacial distribution of the radiation on the available energy are discussed. Atmospheric effects are examined, using NASA standard atmosphere solar spectral distributions. The available energy of the spectral characteristics is compared with the available energy of thermal equilibrium radiation at the same solar flux. This is used to illustrate the available energy losses in thermal energy converters. The technical evaluation of solar energy converters are discussed, based on the available energy of the input energy. A method for evaluating spectral sharing solar conversion devices and solar energy simulators is outlined.