Energy and Exergy Analysis of Ethanol Steam Reforming with an Emphasis on Thermal Efficiency for Sustainable Mobility Applications

The growing demand for sustainable energy and the need to reduce greenhouse gas emissions have driven interest in low-carbon hydrogen production. Ethanol steam reforming (SR) offers a promising on-board H2 source by exploiting ethanol’s renewability and liquid-fuel convenience. This study presents an integrated energy and exergy analysis of ethanol SR across 573 to 923 K and steam-to-ethanol (S/E) ratios from 1 to 4 using Gibbs free energy minimization in MATLAB to predict equilibrium compositions and thermal duties. Energy analysis shows the heating duty rising from 0.0311 kWh/mol ethanol at 573 K (S/E = 1) to 0.0521 kWh/mol at 923 K (S/E = 4). Reforming duty shifts from -0.0075 to +0.2426 kWh/mol, while cooling duty recovers between -0.0219 and -0.0727 kWh/mol. The net energy balance transitions from strongly endothermic below 650 K to near-neutral at 700 to 750 K for S/E > 2, and becomes exothermic above 800 K, reaching +0.2463 kWh/mol at 923 K. Exergy analysis reveals that heating stage irreversibilities increase modestly from 0.015 to 0.035 kWh/mol ethanol with higher temperature and S/E. In contrast, reforming-stage destruction falls sharply from 0.125 to 0.017 kWh/mol, and cooling-stage destruction decreases from 0.038 to 0.024 kWh/mol as conditions become more favorable. Total exergy destruction peaks at 0.071 kWh/mol near 713 K (S/E ≈ 4) before declining to 0.060 kWh/mol at 923 K (S/E = 4). Exergetic efficiency correspondingly rises from 1.5 % to over 70 % across this range. The shift in dominant exergy losses from reforming at low temperatures to cooling at high temperatures highlights key opportunities for advanced heat-recovery integration. Optimal operation between 850 K and 900 K with elevated S/E ratios maximizes hydrogen yield while minimizing energy quality losses. These insights inform reactor design and thermal management strategies for sustainable mobility, demonstrating that tailored temperature and steam loading can substantially improve the performance of on-board ethanol steam reforming systems.