Flexible Production of Green Ammonia : An Optimisation Approach to Cost-Efficient and Adaptable Power to Ammonia Production in Denmark

Abstract

The majority of global ammonia production relies on non-renewable energy, as green ammonia is substantially more expensive. However, the energy landscape is changing, and countries like Denmark are expanding their capacity in renewable energy. Given this increase in renewable capacity, demand for ammonia, and net-zero solutions, it is essential to reduce the total cost of ammonia and increase its competitiveness. The primary objective of this thesis is to study the feasibility of decreasing the overall cost of ammonia in the established renewable market of Denmark. The ammonia production configuration considered in this thesis consists of alkaline water electrolysis and Haber- Bosch synthesis. We employed a multi-period, mixed integer optimisation model over the three coming decades and adjusted key elements to see their effect on cost. The ammonia system considered is grid-connected to the west Denmark electricity grid DK1 and utilise historical NordPool data from the same electricity grid for our optimization model. The findings indicates that savings of up to 1,5 percent are possible for ammonia production, when utilising excess production capacity and the capabilities are improved to satisfy annual demand. The savings occur as a result of more production during advantageous time periods. However, excessive production capacity increases costs as a result of the systems capabilities. Furthermore, we find intermediate hydrogen storage to not be beneficial, except for long-term periods of extreme electricity price volatility with no excess production capacity. Additionally, the alkaline electrolysis should be minimized in relations to the appropriate excess production capacity of the Haber-Bosch synthesis given its high degradation.