Green ammonia as a spatial energy vector: a review

Abstract

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 access to this resource, Japan, Germany and South Korea have announced plans to import hydrogen; other major energy consumers are sure to follow. Ammonia, a promising hydrogen derivative, may enable this energy transport, by densifying hydrogen at relatively low cost using well-understood technologies. This review seeks to describe a global green ammonia import/export market: it identifies benefits and limitations of ammonia relative to other hydrogen carriers, the costs of ammonia production and transport, and the constraints on both supply and demand. We find that green ammonia as an energy vector is likely to be critical to future energy systems, but that gaps remain in the literature. In particular, rigorous analysis of production and transport costs are rarely paired, preventing realistic assessments of the delivered cost of energy, or the selection of optimum import/export partners to minimise the delivered cost of ammonia. Filling these gaps in the literature is a prerequisite to the development of robust hydrogen and ammonia strategies, and to enable the formation of global import and export markets of green fuel.