A comparative assessment on hydrogen production from low- and high-temperature electrolysis

In this work a comparative analysis between low- and high-temperature electrolysis for hydrogen generation is assessed. A hydrogen production system based on Solid Oxide Electrolysis Cells (SOEC) is designed and modeled and compared to the performance of a more mature system based on PEM technology. The SOEC system mainly consists of an SOEC stack, a heat recovery system and a hydrogen compression section. Experimental data measured in steam electrolysis tests performed on single solid oxide cells were utilized into the model to characterize the stack performance. The model carries out a thermodynamic analysis in order to calculate the energy efficiency and the exergetic consumption of the system; these performances are subsequently compared with those of a low-temperature hydrogen generation system evaluated from experimental data measured in test sessions performed on a complete BoP integrating a pressurized Proton Exchange Membrane (PEM) electrolyser. The comparison is carried out with the two electrolysis systems generating hydrogen at the same production rate and pressure. The results of this study show that the modeled SOEC hydrogen generation system can compete with the PEM electrolyser, achieving better performance than the low-temperature system at hydrogen production rate higher than 18.3 g h−1 (corresponding to 0.25 A cm−2) and showing an energy efficiency up to 14% higher than the PEM system at 1 A cm−2.