Renewable energy is continuously increasing its penetration in the energy supply network around the world. Due to the intermittent nature of renewable energy sources like solar and wind, storage of excess energy during its availability is vital. Energy storage, especially on the large scale, has recently received a lot of attention from the scientific world and ammonia has been identified as a
promising energy storage medium suitable for this application. Factors like high energy density, potential to have minimal carbon footprint and ready existence of suitable infrastructure for handling and transport especially make it an attractive choice. Moreover, ammonia is a bulk feedstock in the chemical and fertiliser industry making it a valuable commodity.
A generic model has been developed in MATLAB to assess the economic feasibility of producing ammonia from varying availability of electric power. The model estimates the optimum plant capacity at which levelised production cost is minimum thereby resulting in minimum energy storage cost. Steel industries like Tata Steel produce electric power to satisfy the plant’s operational
demand using by-product gases (termed as work arising gases) evolved during the steel making process. An intermittent availability of surplus electric power has been reported at Tata Steel, IJmuiden.
The economic feasibility of utilising ammonia to store the surplus available electric power using the developed MATLAB model has been assessed in this study. It has been found that the variable cost due to electric power consumption, the fixed cost of the system and capital cost of the electrolyser
significantly influence the production cost of ammonia. The minimum levelised production cost estimated in this study is €997/ton which is almost three times the current market price of ammonia. The system shows potential to produce ammonia at a competitive price when sufficient electric power is continuously available at an electricity price of €10/MWh or lower. Utilising part of the hydrogen produced from the work arising gases in the ammonia production process helps to lower the levelised production cost to around €913/ton. Availability of sufficient hydrogen simplifies the system and it may be possible to produce ammonia at a competitive price when hydrogen price is lower than €1.26/kg.
The power to ammonia process shows an efficiency of around 50%. Using gas turbines to produce electricity from ammonia are expected to result in roundtrip efficiencies of around 15%-25%. Research and pilot plants have shown good potential of using ammonia as a fuel in combustion engines and commercial applications are expected to be realised in the near future.