Impact of voltage degradation in water electrolyzers on sustainability of synthetic natural gas production: Energy, economic, and environmental analysis

Synthetic natural gas (SNG) production from captured CO₂ and H₂ produced by water electrolysis using renewable energy is of increasing interest for low-carbon fuel production, CO₂ utilization technology, and unstable renewable energy storage. In this study, the effect of voltage degradation in a water electrolyzer, a core technology for SNG production, on the unit production cost of SNG production and CO₂ emissions, with different water electrolysis types such as alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and solid oxide electrolysis (SOEL), was identified through techno-economic and environmental assessment. In particular, the energy efficiency, unit production cost of SNG, and CO₂ emissions were identified based on the change in the power consumption caused by voltage degradation. Moderate voltage loss results in a decrease in energy efficiency from 53.8% to 48.8% in AEL, 55.3% to 47.0% in PEMEL, and 76.3% to 51.2% in SOEL. Moreover, respective SNG unit production costs of 140.3–170.2 USD MWh⁻¹, 157.5–203.1 USD MWh⁻¹, and 153.1–353.5 USD MWh⁻¹ for AEL, PEMEL, and SOEL, respectively, were obtained, showing an increase in SNG production cost due to the voltage degradation. Furthermore, total CO₂ emissions for the SNG production process were investigated considering voltage degradation as well as electricity generation sources.