From renewable energy to ship fuel: ammonia as an energy vector and mean for energy storage

The stochastic and non-controllable nature of most of renewable energy sources makes it necessary to include extensive use of energy storage in national grids to overcome periods with low availability. Hence, effective energy storage technologies will be requiredfor achieving a 100% renewable energy system. Currently used technologies are only partly suitable for this task. Batteries are efficient but expensive, and mostly suitable for daily storage. Hydrogen has a significant potential, but suffers from a low energy density and difficulties in handling and transportation. Among different potential solutions, ammonia was often pointed out as a high-density and low-cost hydrogen carrier. In this paper, we analyze the efficiency of an ammonia-based pathway for the storage of excess energy from renewable energy sources, its transportation, and its final use. As a case study, we consider the use on board of a urban car transport vessel as the user of the stored energy. The energy efficiency and cost of the whole chain, from the production at the wind farm until its use on board of the ferry, is evaluated and compared with competitive alternatives, namely batteries and hydrogen storage. The results show that, while not being a game-changer, the use of ammonia as mean for storing and transporting excess energy from renewable power plants is viable and, in combination with other storage systems, contributes to a relevant part of the share of total installed storage capacity in the most cost-effective solution.