[ ammonia ]
Naturally , there are other configurations of HB plants , featuring various technologies for nitrogen production , compression , and product separation . Still , most models prioritize the configuration with the highest technology readiness level . 11
Energy demand
Haber-Bosch plants are designed for 24 / 7 operation , and the typically sized HB + ASU ( air separation unit ) plant will require between 28 and 44 MW of 24 / 7 electricity supply .
The energy supply for green hydrogen feedstock is significantly greater than the electricity demand for the HB process . Figure 2 illustrates the energy requirements for hydrogen production using alkaline electrolyzers operating 24 / 7 as a reference .
CAPEX costs
The capital expenditure for a green ammonia production plant is dominated by the electrolyzer cost . In the case of 24 / 7 alkaline electrolyzer operations , the associated CAPEX costs are as shown in Figure 3 . These costs are based on an assumed CAPEX of USD 183 / kg of NH 3
/ day for the HB plant and USD 800 / kW for the alkaline electrolyzer , which can be considered as referential .
With more optimistic assumptions about CAPEX costs of HB plants , the costs can be significantly lower .
This illustrates that green ammonia production is greatly influenced by the energy demand and CAPEX costs of green hydrogen production . The cost of energy for hydrogen production will be a
Energy demand , Haber-Bosch process
35 MW
Including nitrogen production , compression , and balance of plant
Energy demand , H2 production ( 24 / 7 )
374 MW
Fig . 3 . Electricity demand for the HB process and 24 / 7 hydrogen production via alkaline water electrolysis
determining factor for overall costs . The positive news is that green hydrogen costs are decreasing significantly due to the availability of low-cost renewable energy and the rapid learning curve in the electrolyzer production industry , leading to electrolyzers with lower costs and higher efficiency .
Solar ammonia : a sustainable pathway
A particular case of green ammonia is ‘ solar ammonia ’, produced by integrating HB plants with solar PV-driven electrolysis . 9 Solar ammonia offers a promising low-emission alternative and the potential to benefit from low-cost electricity , provided that the solar resource is robust , and the levelized cost of energy ( LCOE ) of the solar plant is sufficiently low . By coupling HB plants with solar PV-driven electrolysis , renewable energy sources can be utilized for ammonia production , reducing the carbon footprint and aligning with global sustainability goals . However , this integration comes with challenges .
The dynamic and intermittent nature of solar energy introduces variability , which can impact the traditionally inflexible HB cycle . By redesigning
Table 1 . Key parameters useful for analysis of ammonia projects Parameter Unit Typical values Comment Sources
NH 3 production capacity , current |
kg of NH 3 / day |
1,000,000 – 2,000,000 |
Current industrial-scale plants 9 |
NH 3 production capacity , flex |
kg of NH 3 / day |
200,000 – 500,000 |
Flexible HB reduced-scale plants ( future ) 7 |
Specific energy consumption , HB kWh / kg of NH 3 0.64 – 1.08 For HB + ASU ( excluding electrolyzers ) 7 , 9 , 11
Specific CAPEX , HB USD /( kg of NH 3
/ day ) 100 – 206 For HB + ASU ( excluding electrolyzers ) 9 , 11 , 12
Hydrogen Tech World | Issue 12 | October 2023 27