Hydrogen production intensification by energy demand management in high-temperature electrolysis

• First detailed SOE flowsheet built in Aspen Plus with electrochemical sub-model. • Box–Behnken DOE optimises T, P, j, steam ratio and utilisation in one run. • Electrical work minimised to 170.1 kJ mol⁻¹ H₂ via waste-heat integration. • Multi-objective Pareto search delivers 21 % lower grid power than baseline. Solid oxide electrolysers (SOEs) can decarbonise H 2 supply when powered by renewable electricity but remain constrained by high electrical demand and integration penalties. Our objective is to minimise the electrical (P el ), and thermal (Q th ) energy demand per mole of H 2 by jointly tuning cell temperature, steam fraction, steam utilisation, pressure, and current density. Compared with prior single-variable or thermo-neutral-constrained studies, we develop and validate a steady-state, process-level optimisation framework that couples an Aspen Plus SOE model with electrochemical post-processing and heat caused by ohmic resistance recovery. A Box–Behnken design explores five key operating parameters to capture synergies and trade-offs between Q th and P el energy inputs. Single-objective optimisation yields P el = 170.1 kJ mol⁻¹ H 2 , a 41.4% reduction versus literature baselines. Multi-objective optimisation, using an equal-weighted composite desirability function aggregating thermal and electrical demands, further reduces P el by 21.2% while balancing thermal input, 4–8% lower than single-objective baselines at moderate temperature (∼781°C) and pressure (∼17.5 bar). Findings demonstrate a clear process intensification advantage over previous studies by simultaneously leveraging operating parameter synergies and heat-integration. However, results are bounded by steady-state, perfectly mixed, isothermal assumptions. The identified operating windows are mechanistically grounded targets that warrant stack-scale and plant-level validation.