Techno-economic analyses of power-to-ammonia-to-power and biomass-to-ammonia-to-power pathways for carbon neutrality scenario

In the energy system transition, energy storage technology is vital for increasing the penetration of renewables, where chemical energy storage is most suitable for long-term grid-scale energy storage. Green ammonia is selected to replace hydrogen for the sake of storage efficiency, safety, and cost. Most time, ammonia is seen as either an energy storage medium or a fuel. However, the dual identity of ammonia as an energy carrier is discussed less. So, this study conceptualizes power-to-ammonia-to-power (P2A2P) and biomass-to-ammonia-to power (B2A2P) pathways where ammonia is served as an energy carrier for both energy storage and fuel. Eight scenarios involving recent ammonia production and utilization technologies are technically and economically evaluated based on hourly weather and demand data. The results show that the B2A2P pathway presents a better performance because the average energy and exergy efficiencies are hardly influenced by the supply and demand balance of electricity. They can reach 40-50% in contrast to 27-47% in the P2A2P pathway. Besides, the B2A2P pathway provides a considerable amount of ammonia (around 10,000 t/month), which takes the major part of revenues. Although the CAPEX (603.3-675.1 MUSD) and OPEX (30-40 MUSD) in the B2A2P pathway are much higher than that of P2A2P (159.2-181.1 and 6-9 MUSD, respectively), the optimal scenario of the B2A2P pathway has a shorter discounted payback time (six years), and higher net present value (415.5 MUSD).

Automated summary

In the transition of the energy system, chemical energy storage is crucial for the increase of renewable energy penetration. Green ammonia is a suitable alternative to hydrogen for energy storage, with higher efficiency, safety, and cost-effectiveness. This study explores the dual identity of ammonia as an energy carrier and compares the performance and economic benefits of different scenarios. The results show that the biomass-to-ammonia-to-power pathway has better performance, higher energy and exergy efficiencies, and provides a significant amount of ammonia production.