Non-blackbody radiation exergy analysis model based on equivalent temperature method for energy conversion application

Thermal radiation plays an essential role in solar energy conversion systems and high-temperature engineering applications. Radiative thermodynamic analysis is crucial for achieving full-spectrum solar energy utilization. However, most research is focused on blackbody radiation, while graybody radiation is more commonly encountered in engineering systems. With the rapid development of micro/nanostructured materials for selective spectral radiation in solar energy applications, conventional graybody models are no longer sufficient for accurate predictions. Consequently, it becomes necessary to investigate graybody radiative exergy as well as the monochromatic radiative exergy of non-blackbody radiation. Since monochromatic radiation is fundamentally an ensemble of monochromatic photons, analyzing monochromatic photon properties provides an important pathway for understanding non-blackbody radiation. Building on the equivalent temperature concept, an analytical model for graybody spectral radiative exergy is firstly derived by employing the photon infinite-staged Carnot engine model. Second, a non-blackbody radiative thermodynamic model is proposed by integrating equivalent temperature method with infinite-staged Carnot engine model. Through case studies, a practical approach for evaluating non-blackbody radiative exergy is established. In addition, the essential role of the infinite-staged Carnot engine model in radiative thermodynamics is verified. Finally, exergy analyses are performed for micro/nanostructured solar absorbers and thermophotovoltaic systems. This study develops a general methodology for applying monochromatic radiative exergy theory in energy engineering analyses and provides key theoretical support for thermodynamic research in solar conversion and thermal engineering systems.