On the thermodynamics of the conversion of partially polarized black-body radiation

(Received 7 November 1991, revised 9 March 1992 and 11 May 1992, accepted 23 June 1992)

Abstract
This paper considers a model consisting of : (i) a source of partially polarized black-body radiation (the pump), (ii) a thermally radiative or non-radiative ambient sink and (iii) two energy converters. The first converter (RH) transforms the energy of the black-body radiation into heat, while the second one (HW) (which has a non-zero entropy generation rate) uses that heat to produce work. The entropy-generation rates in the two converters are non-negative only when some conditions are satisfied, which relate the coefficients of polarization, the three temperatures (of the pump, ambient and converter RH) and the solid angle subtended by the pump. The range of validity of some upper bounds proposed in literature for the conversion efficiency of the radiation energy into work is also determined. Thermal equilibrium imposes some relations between the polarization of the radiation and the solid angle subtended by the pump. The maximum efficiency is studied for the situation when the HW converter follows a regenerative cycle.