Due to the inherent nature of the renewable power, sizing eSyngas plants powered with renewable energy brings complexity normally not faced by natural gas-based facilities. In this article, Dr Raimon Marin and Dr Solomos Georgiou of AFRY discuss the application of AFRY’s state-of-the-art modelling tool to optimise the size and production of a green hydrogen system and a green ammonia plant based on given renewable power profiles and their associated variability (e.g., hourly, daily, seasonally, and annually).