Techno-economic and exergy assessment of green methanol production: Integration of parabolic trough solar plant with alkaline electrolysis and calcium looping-based direct air capture

This study aims to evaluate the techno-economic feasibility of green methanol production powered by green hydrogen from alkaline electrolysis and CO₂ captured through a calcium-looping-based DAC cycle using KOH solution, integrating a hybrid energy system consisting of a PTC-based solar power plant and grid electricity to supply the energy requirements of the production chain. The objective is to assess the potential of the proposed production chain as a low-carbon alternative to fossil-based methanol, with the potential to reduce carbon emissions from methanol production. Aspen HYSYS and Aspen Plus simulations indicate that green hydrogen is produced at a rate of 1.7 ton/h by the alkaline electrolysis system, operating with an input power of 87.4 MW. The DAC cycle requires 17.6 MW of thermal energy to capture 13.7 ton of CO₂ per hour. Based on these inputs, the methanol synthesis process yields approximately 8.6 ton/h of methanol with over 95% purity, consumes 25.3 MW of thermal energy. A PTC-based solar power plant in Zahedan, simulated in Thermoflex, with an 86.8 hectare solar field, supplies the required thermal and electrical energy for the chain during peak hours, ensuring stable operation of the green methanol production chain. Also, a performance assessment of the solar power plant under varying seasonal and hourly conditions is conducted using the SAM software. Sensitivity analysis demonstrated that the optimal configuration of the hybrid energy system was obtained at a solar share of 40%, with LCOT and LCOE values of 0.035 $/kWh and 0.041 $/kWh, respectively. Finally, the economic analysis indicated LCOH, LCOC, and LCOM values of 4.13 $/kg, 93.43 $/ton, and 992.35 $/ton, respectively. The findings demonstrate the techno-economic feasibility of green methanol production based on green hydrogen and DAC technology, highlighting its potential as a low-carbon methanol production pathway in regions with high solar irradiance.