Techno-economic evaluation of hydrogen and ammonia as energy carriers in a multi-generation system

Abstract

Green hydrogen is suitable for grid-scale energy storage to increase the penetration of renewable energy, and it is also an alternative to fossil fuels. However, it still suffers from storage problems owing to its low volumetric energy density, embrittlement, and very low boiling point. To improve safety and reduce cost, green ammonia has been proposed as a substitute for hydrogen and has attracted considerable attention. In this study, a multi-generation system was proposed to compare green hydrogen and green ammonia as energy carriers. Four scenarios are discussed and the performances under different energy carriers, constant and time-of-use electricity prices, and on-grid and off-grid operations are compared. The optimal planning of the system was formulated as a mixed-integer linear programming problem and was evaluated using supply and demand profiles hourly over a year. The objective was to maximize profitability, which is reflected by the cumulative cash position and payback period. The results revealed that the hydrogen-based system was superior to the ammonia-based system. In the hydrogen-based scenario, the cumulative cash position was 83.43 MUSD and the payback period was 14 years. The cumulative cash position and payback period were 12.78 MUSD and 22 years, respectively, in the ammonia-based scenario. To improve profitability, it is recommended to increase the capacity for hydrogen/ammonia production and reduce the capacity for backup power generation.