• A Python model for semi-islanded green ammonia production was developed. • The LCOA ranges from 669.30 to 867.94 €/tNH 3 . • Power generation represents the largest share of total system costs. • The LCOA decreases by up to 15.15 % over the next two decades. • Dynamic operation achieves up to a 6 % reduction compared with continuous operation. The study presents a technical and economic assessment of green ammonia production in several counties in Ireland. The system is based on renewable energy sources, namely photovoltaic and offshore wind. Three locations were chosen based on their renewable potential and the availability of export ports to EU (European Union) markets. A high-temporal-resolution model for green ammonia production has been developed for the first time in Ireland. The WSA (Wind Solar Ammonia) model was developed specifically for this research. It uses MILP (Mixed Integer Linear Programming) and optimisation techniques to simulate scenarios at the lowest possible cost. The Python-based model incorporates all relevant energy subsystems and use functions from specialised libraries. The WSA model includes large-scale hydrogen production with proton exchange membrane electrolysers, air separation to produce nitrogen, Haber-Bosch ammonia synthesis, desalination unit. Storages buffers were implemented for green hydrogen, green ammonia, purified sea water, and nitrogen. Both continuous and dynamic operation were simulated, continuous operation reflects industrial reliability, stable equipment performance, and maximised lifetime, while dynamic operation captures renewable intermittency, curtailment reduction, and system flexibility. Cork is identified as the least-cost location, with the dynamic operation system achieving the lowest LCOA (Levelised Cost Of Ammonia) at 791.07 €/t in 2030 and 731.45 €/t in 2040, outperforming the continuous operation system, which records 834.27 €/t in 2030 and 741.62 €/t in 2040. The system achieve a carbon saving up to 94.63 % compared to the ammonia fossil fuel-based comparator.