Optimizing thermal design for sustainable renewable energy in a novel low-temperature desalination-power cycle

Abstract The escalating global demand for freshwater and clean energy necessitates innovative co-generation solutions. This study provides a comprehensive techno-economic comparison of flat plate solar collectors and evacuated tube solar collectors for a novel solar-driven, low-temperature desalination-power cycle. This innovative cycle operates using water vapor under subatmospheric pressure with an 80 °C evaporator and a 30 °C condenser, requiring 8.25 MW of thermal input. Its unique integration of a turbo-vapor generating unit, a low-pressure steam turbine, and a multistage flash evaporation plant significantly boosts thermal utilization and freshwater output. Performance analysis, which established an optimal solar field inlet temperature of 85 °C, further reveals crucial trade-offs when operating with outlet temperatures between 90 and 100 °C. Regarding their distinct performance characteristics, evacuated tube solar collectors yield higher thermal efficiencies (63.9–64.6%) and require a 33% smaller land footprint. However, this specific collector technology also incurs an 18% greater capital cost. In contrast, flat plate solar collectors, exhibiting efficiencies between 47.5 and 50.8%, provide a key operational benefit through 12.5–19.6% lower pressure losses. The study conclusively demonstrates that for this specific low-temperature application, flat plate solar collectors offer a more compellingly balanced solution regarding overall cost-effectiveness, reduced pumping power, and system performance, despite the inherent thermal efficiency advantage of evacuated tube solar collectors.