There is growing recognition of the need for long-duration energy storage to cope with low frequency (i.e. seasonal to multi-annual) variability in renewable energy supplies. Recent analysis for the UK has estimated that 60–100 TWh of hydrogen storage could be required to provide zero-carbon backup for renewable energy supplies in 2050. However, the analysis did not consider the potential role of green energy imports as a supplement to domestic energy storage. Using a global spatially-explicit model of green hydrogen/ammonia production and shipping we estimate the lowest import costs for green ammonia to the UK, and compare them with the levelized costs of energy storage across scenarios of varying domestic renewable energy production. The results indicate that imported green ammonia could offer a cost-comparable alternative to domestic hydrogen production, storage and power generation, whilst increasing energy system resilience through supply diversification, at a similar or cheaper delivered energy cost compared to a hydrogen-only storage system. In countries lacking the geological potential for low-cost hydrogen storage, green ammonia imports could have an even more significant role.

Green ammonia has been proposed as a technologically viable solution to decarbonise global shipping, yet there are conflicting ambitions for where global production, transport and fuelling infrastructure will be located. Here, we develop a spatial modelling framework to quantify the cost-optimal fuel supply to decarbonise shipping in 2050 using green ammonia. We find that the demand for green ammonia by 2050 could be three to four times the current (grey) ammonia production, requiring major new investments in infrastructure. Our model predicts a regionalisation of supply, entailing a few large supply clusters that will serve regional demand centres, with limited long-distance shipping of green ammonia fuel. In this cost-efficient model, practically all green ammonia production is predicted to lie within 40° latitudes North/South. To facilitate this transformation, investments worth USD 2 trillion would be needed, half of which will be required in low- and middle-income countries.