Sustainability analysis and exergy return on investment of a dual-chamber solar PV-powered evaporative cooling system based on conventional and extended exergy approach

This study evaluates the sustainability of a dual-chamber evaporative cooling system operating at different cooling chamber temperatures, using exergy-based sustainability indices and extended exergy accounting, with a focus on waste exergy management and environmental sustainability. The results show that the system’s sustainability can be improved by reducing physical exergy influx and optimizing waste exergy management, with waste exergy ratio values ranging from 0.71 to 0.91, lack of productivity values ranging from 2.86 to 18.51, environmental impact factor values ranging from 0.079 to 0.20, exergy recovery ratio values ranging from 0.85 to 0.89, and environmental destruction coefficient values ranging from 3.86 to 19.51. The exergy return on investment (ExRoI) analysis reveals that labour, capital, and material resources contribute significantly to the total invested exergy, with total invested exergy ranging from 124,292.8 to 154,882.7 MJ. The ExRoI values ranged from 8 to 30%, and ExRoI-based sustainability index values ranged from 1.08 to 1.43. The results showed that too much physical exergy influx was invested into the system constituting about 70–76% of exergy influx in all cases. Thus, the conventional exergy efficiency and percentage ExRoI were close with percentage ExRoI being lower by 0.44–1.2%. The findings provide valuable insights for energy policymakers and manufacturers to establish design standards and select optimal evaporative cooling systems for Sub-Saharan Africa.