(205f) Clean Production of Hydrogen from Steam Electrolysis in Molten Salts – Experimental Investigation and Process Modeling

The transition towards a renewable energy-dominated grid has increased the demand for clean and sustainable methods of hydrogen production. Electrolysis is one of the most promising methods for hydrogen production, and this talk focuses on molten salt electrolysis, a relatively new and unconventional approach that allows for steam electrolysis at higher temperatures (>100 C) compared to traditional low-temperature electrolysis systems. This approach is potentially appealing because of many reasons including: a) thermodynamic advantages of reducing electricity input over heat input with increasing reaction temperature, b) likelihood of lower overpotential due to faster reaction kinetics at higher temperatures and c) avoiding reliance on precious materials for catalyzing the reaction. Here, we discuss results pertaining to a) experimental investigation of the proposed approach, b) process model development, and c) subsequent techno-economic analysis and optimization to benchmark the process concept against other low-carbon hydrogen production routes.

The experiments provide insights into the feasibility and practical limitations of the molten salt electrolyser. Cyclic voltammetry experiments have been successfully conducted to determine the polarization curve (voltage-current density dependence) at different experimental conditions and point to the possibility of lower overpotentials compared to state-of-art alkaline electrolysis systems.

Based on these experiments we developed a process simulation model for a production-scale facility that incorporates a custom model for the electrolyser. The model considers various parameters, including the operating temperature and current density, and enables the investigation of the impact of different operating conditions on the efficiency of the process. Additionally, the process model provides a useful tool for identifying how various process design choices, like reaction temperature, heat recuperation mechanisms and cell ohmic potential impact the overall energy requirements of the system and subsequently levelized cost of hydrogen produced.

Techno-economic analyses of the proposed process are performed and results are benchmarked against other approaches to hydrogen production: alkaline, proton-exchange membrane, and natural gas reforming. Due to the highly volatile nature of electricity prices in future renewable energy-dominated grids, both static and dynamic operation of the plant is considered in the techno-economic analyses. The techno-economic modeling results reveal key performance targets for molten electrolysis to be cost-competitive with other approaches for low-carbon hydrogen production.