This article presents a comprehensive thermodynamic analysis of renewable energy conversion systems, with particular emphasis on solar photovoltaic (PV) cells, concentrating solar power (CSP) systems, wind turbines, and thermoelectric generators (TEGs). We examine fundamental Carnot efficiency limits governing heat engines and derive modified efficiency expressions applicable under finite-time thermodynamic (FTT) constraints. Entropy generation minimization (EGM) techniques identify dominant irreversibility sources and guide design improvements. Our analysis demonstrates that CSP parabolic dish systems operating at concentration ratios C = 800–1200 achieve exergetic efficiencies of 40–44%, approaching the Curzon-Ahlborn ceiling of 38.8%. Cascaded Bi₂Te₃/PbTe TEG configurations attain ZTeff = 2.1 at Tm = 550 K, yielding 14.3% conversion efficiency — a 28% improvement over single-stage designs. Modified Betz-Joukowski aerothermodynamic modeling constrains the practical wind turbine efficiency ceiling to 48.7% under realistic atmospheric boundary layer conditions. These findings establish actionable design guidelines and underscore the indispensable role of second-law analysis in next-generation renewable energy optimization.

Keywords: Carnot efficiency · entropy generation minimization · solar concentration · thermoelectric generators · Betz limit · exergy analysis · finite-time thermodynamics · renewable energy optimization · LCOE · energy finance