Generalized formulation for ideal light-powered systems through energy and entropy flow analysis Part 2: Beyond the first-order evaluation under realistic conditions

Abstract

This study formulates the ideal efficiency of light-powered systems in the most general form, based on the first principle of energy-entropy flow analysis under the condition of zero entropy generation within the system. A unified formula for the ideal efficiency of light-powered systems is presented in this study. The formula incorporates the absorption ratio |$\varepsilon$| as an indicator beyond the first-order evaluation based on photon number, for light with a dilution indicator d, and it is extended to cases where entropy is simultaneously discarded from the system via radiation and heat. Selecting the appropriate Y-factors and p-parameters from this study for given conditions allows us to accurately and systematically derive the ideal efficiencies of light-powered systems and correctly classify the multiple ideal efficiencies that were previously confused, such as the Jeter, Spanner, and Landsberg-Petela efficiencies which form the basis of practical efficiency. This study also classified existing light-powered systems into two models: the piston-cylinder radiation model and the flowing radiation model, and demonstrated that the latter model is suitable for micro light-powered systems. Finally, this study clarified two issues with the ideal efficiency proposed by Landsberg and Tonge (often referred to as the Landsberg limit) based on the classical flowing radiation model, and derived a new ideal efficiency using a simple mathematical model based on Einstein's theory of radiation and absorption in a two-level system, which assumes quantum transitions, to resolve those problems. The newly obtained ideal efficiency was found to behave very similarly to the Carnot efficiency.