Thermofluid and exergy characteristics of MoS2/water nanofluid flow in a flat‑plate solar collector under high‑irradiance conditions

This study presents a comprehensive energy, exergy, economic, and environmental (4E) assessment of a flat‑plate solar collector operating with MoS2/water nanofluids at concentrations of 0%, 0.5%, and 1% under the high‑irradiance climatic conditions of Ahvaz, Iran. A validated transient numerical model is employed to evaluate the system’s monthly performance over a full annual cycle, yielding a Root Mean Square Error (RMSE) of 16.42 W and a Mean Absolute Percentage Error (MAPE) of 2.12%. The results indicate that the 1 vol% nanofluid consistently enhances thermal performance, increasing the useful energy gain by up to 13% and the collector outlet temperature by 20% during winter months. Exergy analysis reveals notable improvements, with exergy output and exergy efficiency increasing by up to 20 and 22%, respectively, alongside a 6–7% reduction in exergy destruction. From an economic standpoint, the system achieves a minimum Levelized Cost of Heat (LCOH) of 0.77 $/kWh in June, while the specific exergy cost is reduced by 3–5% through nanoparticle addition. Environmentally, the 1 vol% nanofluid yields the highest avoided CO2 emissions (up to 44 kg/month) and improves both the Environmental Index and the Environmental–Energetic Efficiency. Moreover, the Solar Utilization Ratio (SUR) increases by 10–13% on an annual basis. Overall, the findings demonstrate that MoS2‑based nanofluids offer substantial thermodynamic, economic, and environmental advantages, confirming their suitability for flat‑plate solar collectors operating in high‑irradiance regions.