Exergy-based performance evaluation of a direct steam generation receiver for solar energy exploitation

Direct steam generation (DSG) in linear parabolic collectors represents an effective pathway to improve solar-thermal energy utilization by eliminating the constraints of conventional heat-transfer fluids and enabling higher operating temperatures. This study develops a comprehensive energy and exergy modeling framework for a DSG solar collector receiver, integrating optical–thermal characteristics with detailed representations of radiative, convective, and conductive heat-loss mechanisms. The receiver performance is investigated under varying solar irradiance levels and mass flow rates, and the axial thermal behavior is resolved into three distinct regions corresponding to single-phase heating up to saturation, two-phase evaporation, and superheated steam heating. The numerical approach is validated through a grid-independence study, demonstrating solution stability beyond 1000 elements, and through consistency checks with published correlations for temperature evolution and two-phase pressure-drop behavior. The results indicate that, at a solar irradiance of 1000 W m − 2 and an optical quality of 0.8, the receiver achieves a thermal efficiency of 92.17%. Exergy analysis reveals an overall receiver exergy efficiency in the range of 35–38% at 900 W m − 2 , assuming a reference temperature of 298 K, underscoring the impact of irreversibilities associated with finite-temperature heat transfer and environmental losses. The distribution of exergy destruction shows that radiative and ambient losses account for 44.9%, followed by conduction (31.8%) and convection (23.3%). These findings provide practical guidance for receiver design improvements and operational strategies aimed at more effective solar energy exploitation.