Abstract
Currently, manufactured ammonia relies on natural gas or coal, which releases harmful carbon emissions. We investigate the viability of a small-scale “green” ammonia plant where renewable electricity is used to provide hydrogen via electrolysis and nitrogen via air liquefaction to a Haber–Bosch system to synthesize ammonia. The relatively small scale, and measures such as continuous preheating, are envisioned to provide response times on the order of minutes rather than the days required by prevalent large-scale, fossil fuel-based ammonia plants. A green ammonia plant can serve as a demand-responsive load and long-term energy storage mechanism (through chemical energy storage in ammonia). We investigate its functional and economic viability within an agricultural community microgrid, which is a new contribution to this area of study. This paper proposes a coordinated operational mixed-integer linear programming (MILP) model of an electricity distribution system and an electricity-run, green ammonia plant enabled by the Haber–Bosch process. Case studies in both grid-connected and islanded modes are performed on an agricultural community microgrid based on a modified Pacific Gas & Electric (PG&E) 69-node electricity distribution system coupled with a flexible, small-scale ammonia plant and direct ammonia fuel cell. Results indicate the ammonia plant can adequately serve as a demand response resource and positively impact the distribution locational marginal price (DLMP) by reducing or removing voltage violations and line congestion in the system. Studies showed this coupling decreased electricity costs of the ammonia plant by nearly a third, with ammonia profits increasing 17%. Further, in an emergency, the direct ammonia fuel cell can provide essential power. This cooperation among the food–energy–water (FEW) network offers a unique solution to the challenge of a more efficient interconnection of renewable energy (RE) resources to the grid. Additionally, this work has the potential to reduce grid dependence on fossil fuels and aid in the decarbonization of ammonia production.
