A feasibility study of implementing an Ammonia Economy
This thesis reports the results of a feasibility study performed on the concept of an Ammonia Economy, which treats ammonia as an alternative fuel and energy storage mechanism. As part of the Ammonia Economy, costs for production, storage, and transportation of this alternative fuel are also presented. The cost of hydrogen, which is the main feedstock for ammonia production, was first determined for both fossil-fuel and alternative energy sources. Capital costs and operating parameters of an ammonia synthesis plant were then used in an economic model to calculate the cost of ammonia from energy sources that included natural gas, coal, nuclear, ocean thermal energy conversion (OTEC), wind, solar, and biomass. The energy use and cost for both hydrogen and ammonia fuels was then compared for fuel storage and transportation.
The results showed that the lowest cost ammonia source is coal with a production cost of 147-432 $/t, or a gasoline equivalent of 0.96-2.83 $/gal. Natural gas and OTEC also provided low costs of less than 689 $/t, or a gasoline equivalent of 4.51 $/gal. Other alternative ammonia sources were more expensive, however, they may become economical as fossil fuel costs increase and technological advances improve the alternative fuel technology.
The storage analysis of ammonia and hydrogen showed that the ammonia storage system is 93.6% efficient when the ammonia synthesis energy is included in the calculation, which was calculated by dividing the chemical energy stored by the chemical and electrical energy added to the storage vessel. In comparison, hydrogen is only 76.9% efficient. Ammonia also required nearly five times less energy for low temperature storage than hydrogen. In addition, ammonia has a storage cost advantage over hydrogen with an estimated cost for 182 days of storage to be 14.83 $/kg-H2 and 0.51 $/kg-H2, respectively.
Comparing the transportation of the two fuels showed that ammonia is more efficient and less expensive than hydrogen to transport in a pipeline. Specifically, the efficiency for transporting the fuel 1,610 km and delivering it at fueling pressure is 93.4% and 86.9% for ammonia and hydrogen, respectively. The ammonia calculation also includes the losses involved with ammonia synthesis from a hydrogen source. Pipeline transportation costs are estimated to be 0.70-3.22 $/kg for hydrogen, and 0.0344 $/kg for ammonia. The ammonia delivery cost in hydrogen terms is 0.194 $/kg-H2, which makes hydrogen at least three times more costly to transport than ammonia.