Thermodynamic and exergoeconomic assessment of a solar-assisted polygeneration system integrating power, cooling, heating, and desalination technologies

This study proposes a solar-assisted polygeneration system for the simultaneous production of power, heating, cooling, and freshwater through cascaded heat recovery. The system integrates a solar power tower with molten-salt thermal storage, an auxiliary heater, a recompression supercritical carbon dioxide Brayton cycle, a toluene-based organic Rankine cycle, a single-effect LiBr–H 2 O absorption chiller, and a multi-effect distillation–thermal vapour compression desalination unit. Energy, exergy, and exergoeconomic analyses were conducted, followed by a comprehensive parametric assessment. Under baseline conditions, the system produces 263.5 MW of net power, 237.7 MW of heating, 58.89 MW of cooling, and 89.02 kg/s of total distillate freshwater. Compared with the configuration without the ORC and MED–TVC units, the complete system increases the second-law efficiency by 6.57 percentage points and reduces LCOE by 5.14%. The first- and second-law efficiencies are 39.15% and 54.97%, respectively, while the first- and second-law energy-utilization factors reach 86.30% and 58.93%. Based on 8000 equivalent full-load operating hours, the annual-equivalent levelized costs of useful energy and net power are estimated at $24.53/MWh and $54.07/MWh, respectively. The auxiliary heater accounts for approximately 40% of the total exergy destruction, while the organic Rankine cycle contributes only 4%. The parametric analysis identifies favourable operating ranges of 0.5–2 for the supplementary energy ratio, 2.8–3.2 for the sCO₂-cycle pressure ratio, and approximately 0.33 for the recompression split ratio. Reducing reliance on the auxiliary heater improves the second-law efficiency and lowers the system cost. These findings demonstrate the potential of cascaded solar and waste-heat utilization for integrated energy and freshwater production.