Energy Efficiency in the Hydrogen Value Chain for Ammonia Synthesis

Sammanfattning

Green ammonia, produced from renewable hydrogen, is emerging as an important energy carrier and decarbonized fertilizer alternative. However, its production is highly energy-intensive, making process efficiency critical to its commercial viability. This study investigates how targeted heat integration can enhance the energy and cost efficiency of green ammonia production based on a 200 MW PEM electrolyzer. Three design configurations were developed and simulated using Aspen Plus: The Base Design without advanced heat integration representing a conventional green ammonia plant including freshwater generation, electrolysis, Haber-Bosch synthesis and cooling. The Alfa Laval Design, incorporating Alfa Laval’s multi-effect evaporation technology for freshwater generation using electrolyzer waste heat into the process, and a Suggested Design further optimized with absorption refrigeration and steam turbine enhancements. The designs were evaluated based on electricity, heating, and cooling demands, and compared with literature in terms of total energy intensity and the levelized cost of ammonia. Results proved that strategic heat recovery significantly improved process performance. The Suggested Design reduced electricity consumption by 1.1%, heating by over 60%, and cooling demand by 16% compared to the Base Design. These reductions translated into a total annual utility savings of 85.4MSEK and lowered the levelized cost of ammonia by 380 SEK/ton ammonia. With a payback period of approximately 1.5 years, the optimizations demonstrated strong economic viability. The study concludes that heat integration offers a powerful pathway to reduce both energy use and production cost in green ammonia systems. The findings demonstrate that strategic process integration can significantly improve the energy efficiency and cost-effectiveness of green ammonia production. This methodological framework can be used to support industrial-scale design decisions, provide a foundation for further research, and contribute to the global transition toward utilizing green hydrogen for sustainable ammonia.