Abstract
The transition toward low-carbon ammonia production increasingly relies on highly efficient routes for renewable hydrogen generation, with Solid Oxide Electrolysis (SOE) representing a particularly promising solution. SOEs, operating with steam at elevated temperatures, offer intrinsic thermodynamic advantages and are attractive when integrated with processes that can effectively utilize or supply high-grade heat. This context opens the possibility for advanced energy coupling between hydrogen production and the exothermic ammonia synthesis process. This work investigates such an energy integration strategy by simulating a small-scale ammonia plant where hydrogen is produced through an SOE system thermally coupled to the ammonia synthesis loop. Specifically, high-grade heat available in the Haber-Bosch (HB) reactor outlet is recovered via a "Heat Recovery Steam Generator" (HRSG) to provide a substantial fraction (55 wt%) of the steam required by the electrolyzer. The assessment demonstrates that the integrated configuration significantly reduces the external electrical demand for steam generation by 84%, achieving a substantial enhancement in system-level electrical efficiency. Total plant energy efficiency increases from 57% to 62%, and the electricity-to-hydrogen ratio decreases from 45.9 to 42.1 kWh/kg. These improvements translate directly into a decrease in the Levelized Cost of Ammonia (LCOA) by 4-5%, underscoring the relevance of high-temperature electrolysis supported by effective plantwide heat recovery.