Ammonia as a Renewable Energy Transportation Media

TLDR

Ammonia produced from renewable hydrogen can store and transport renewable energy, but converting it back to usable forms incurs significant energy losses. The paper reviews current ammonia synthesis processes and technologies for its use as an energy carrier. The authors analyze these processes and technologies to evaluate their performance as an energy carrier. The authors estimate round‑trip efficiencies for various end‑use routes, showing substantial variation between best‑ and worst‑case scenarios.

Abstract

Ammonia synthesized using hydrogen from renewable sources offers a vast potential for the storage as well as transportation of renewable energy from regions with high intensity to regions lean in renewable sources. Ammonia can be used as an energy vector for an emissionless energy cycle in a variety of ways. Ammonia at the point of end use can be converted to hydrogen for fuel cell vehicles or alternatively utilized directly in solid oxide fuel cells, in an internal combustion engine or a gas turbine. One ton of ammonia production requires 9–15 MWh of energy. However, its conversion back to useful form or direct utilization can lead to substantial energy losses. In this paper, we present an overview of the current processes and technologies for ammonia synthesis and its utilization as an energy carrier. We have performed an estimation of the round-trip efficiency of different routes for ammonia utilization at the point of end use along with some sensitivity analysis, and we discuss the outcomes resulting from the best and worst case scenarios.