Green hydrogen is considered a highly promising vector for deep decarbonisation of energy systems and is forecast to represent 20% of global energy use by 2050. In order to secure...

The production of hydrogen from hydrocarbon/water compounds can be classified into three categories, namely "brown", "blue", and "green". 27 Brown hydrogen is produced from H 2 O by steam reforming of natural gas (or coal) at about 800−900 °C. The enthalpy required for H 2 production is significantly Figure 4. (a) Schematic diagram of (A) methane-fed and (B) electrolysis-driven Haber−Bosch ammonia production. Reproduced with permission from ref 44. Copyright 2020 The Royal Society of Chemistry. (b) Dissociative pathway for N 2 activation (above) and stepwise nondissociative pathway for N 2 activation (below). Reprinted with permission from ref 46. Copyright 2019 John Wiley and Sons. (c−e) Various strategies to carry out ammonia synthesis at low temperature and low pressure: (c) The use of electrostatically polar surfaces to alleviate hydrogen poisoning challenges at low temperature. Reprinted with permission from ref 52. Copyright 2020 American Chemical Society. (d) Dual-site mechanism to tackle nitrogen activation and hydrogen dissociation separately. Reprinted with permission from ref 54. Copyright 2020 Springer Nature. (e) Li-polarized surface to stabilize intermediates to carry out the more energy favorable non-dissociative pathway. Reprinted with permission from ref 46. Copyright 2019 John Wiley and Sons. (f) A novel mechanochemical method to enable ammonia synthesis at 45 °C and 1 bar. Reprinted with permission from ref 55. Copyright 2020 Springer Nature. (g) Direct eNRR via absorption of N 2 onto the catalyst surface, followed by progressive proton and electron additions to produce a first, followed by a second molecule of ammonia. Reprinted with permission from ref 56. Copyright 2018 John Wiley and Sons. (h) Indirect electrochemical N 2 reduction to ammonia based on lithium as a mediator, forming Li 3 N as an intermediate, and reaction with H 2 O on a copper substrate. Reprinted with permission from ref 57.

Summary Green ammonia is a promising hydrogen derivative which enables intercontinental transport of dispatchable renewable energy. This research describes the development of a model which optimizes a global green ammonia network, considering the costs of production, storage, and transport. In generating the model, we show economies of scale for green ammonia production are small beyond 1 million tonnes per annum (MMTPA), although benefits accrue up to a production rate of 10 MMTPA if a production facility is serviced by a new port or requires a long pipeline. The model demonstrates that optimal sites for ammonia production require not only an excellent renewable resource but also ample land from which energy can be harvested. Land limitations constrain project size in otherwise optimal locations and force production to more expensive sites. Comparison of current crude oil markets to future ammonia markets reveals a trend away from global supply hubs and toward demand centers serviced by regional production.

Grid connectivity for green ammonia can reduce costs and have negative carbon emissions if the process acts as an electricity consumer/producer.

No abstract

No abstract

No abstract

No abstract