Hydrogen as a vector has a low volumetric energy density, it has to be either compressed to high pressure, liquefied or combined as hydrogen carrier.

Amongst all considered options, ammonia is a carbon-free and dispatchable energy carrier for large-scale renewable electricity storage. It is a primary candidate for securing a clean supply of renewable energy for various stationary and mobile applications. This ability to provide a wide range of energy storage services relies on using existing robust infrastructure, established regulation and acceptable safety record in the industry for over 75 years.

Ammonia is easily liquefied at 1 MPa and ambient temperature. It also presents a high hydrogen gravimetric density of 17.8 % by weight and simultaneously an impressive volumetric hydrogen density of 108 kg H2/m3 at 20°C and 8.6 bars. This is 1.5 time greater than liquified hydrogen and over 4 times better than metal hydrides for instance. This significant advantage of ammonia in carrying hydrogen per unit volume translates directly into a lower cost per unit of stored energy compared to other alternatives. Furthermore, ammonia has the unique feature to behave as a CO2-free energy storage mean unlike other hydrogen carriers such as methanol, methanol, formic acid or Fischer-Tropsch products which release carbon oxides during their use. 

In the ARENHA project, the aim is to demonstrate that ammonia has the required assets to behave as an efficient and cost-effective CO2-free energy storage vector. This only holds true if ammonia production and decomposition are tightly integrated with renewable energy generation.