Thermoeconomic evaluation of a geothermal-driven polygeneration system with PEM electrolysis and non-thermal plasma ammonia synthesis

• A non-thermal plasma reactor synthesizes ammonia at low pressure and moderate temperatures. • This method allows direct coupling with renewables, aiding decentralized production. • Thermodynamic irreversibility is reduced by avoiding N 2 and H 2 pre-compression. • This electrified process makes ammonia a zero-carbon fertilizer and energy carrier. The global transition to a hydrogen economy is hindered by the lack of truly no direct CO 2 emissions processes. Haber–Bosch method relies on fossil–derived hydrogen, while also is limited by high pressures and temperatures demanding compatibility with renewable sources. The proposed system uses geothermal energy to drive a non-thermal plasma reactor for ammonia synthesis and a PEME to supply hydrogen. Excess heat is utilized for hot water production and electricity generation via a Kalina-cycle–single-flash power plant. Under base‑case conditions, the integrated geothermal–Kalina–PEME–NTP system delivered 40.60% thermal, 16.61% electrical and 42.63% exergy efficiency and required 6403 kW wind turbine power in this case. Despite a baseline LCOA of approximately 7.6 $/kg, sensitivity analysis indicates that the LPC Total decreases from 2.82 to 0.0667 $/kWh, through Kalina cycle integration from 0.058 to 0.039 $/kWh via recycle optimization. Exergy losses, which are dominated by the geothermal unit, diminish with increased geothermal flow and reduced water feed as turbines and heat exchangers approach optimal design. Furthermore, the recycle-gas ratio exhibits a broad optimum between 0.6 and 0.65, yielding an exergy efficiency of 40–43% and an LPC Total of 0.05–0.055 $/kWh.