Proper intermittency management in green ammonia production is a key performance driver of the whole production plant. The main challenge is to manage two units: the hydrogen production by water electrolysis which is very flexible and reactive together with the ammonia synthesis which is more sensitive to fluctuation.  

Attention is often focused on maximizing hydrogen production by trying to follow as close as possible the available power, and by using hydrogen storage to keep a constant Ammonia production. This simplistic approach usually leads to a higher Levelized Cost of Hydrogen (due to high storage cost) and safety issues (due to high pressure hydrogen).  

Rely has completed a case study based on an industrial scale ammonia production project, defining the best asset architecture. This study leverages  dynamic modelling software Odyssey to compare a wide combination of configurations and operational strategies to minimize both LCOH and LCOA. The simulations are run over the plant’s full lifecycle. First, they are run hourly and subhourly at plant level.  Once an optimum architecture is selected at system level, the study addresses intermittency challenges by pushing it further and performing unit level optimization using a secondary modeling tool.  

In the key learnings, it is concluded that multi‑resolution dynamic simulation (hours → minutes → seconds) is essential to address the intermittency challenges of green hydrogen and progress from conceptual design to verifiable, safe, and robust industrial operation. From this, a project can use integrated system design, combining renewable plant sizing, electrolyzer control logic, and ammonia synthesis constraints, to significantly improve overall performance and cost competitiveness.