Renewable energy is playing an increasingly important role in addressing some of the key challenges facing today’s global society such as the cost of energy, energy security and climate change mitigation. Because energy storage is crucial for overcoming the inherent intermittency of renewable resources, chemical storage of energy can be achieved via Hydrogen (H2) or carbon-neutral Hydrogen derivatives such as Ammonia (NH3).

Some of the advantages of Ammonia over Hydrogen are its lower cost per unit of stored energy, higher volumetric energy density, easier and more widespread production, handling and distribution capacity, and better commercial viability. Thus, with its established transportation network and high flexibility, Ammonia could provide a practical next generation energy system for the transportation sector and for power generation by captive power plants. Ammonia is a carbon-free molecule and therefore burning it in an internal combustion engine leads to zero CO2 emission from the stack.

Most of the Ammonia produced today is obtained from natural gas and without carbon-capture (gray Ammonia), and majority of the Ammonia produced is used in the fertilizer industry. However, Ammonia becomes a carbon-neutral fuel when it is produced from renewable energy sources like electricity from wind and solar energy through electrolysis (green Ammonia) or from fossil sources associated with carbon-capture and storage technologies (blue Ammonia).

Ammonia characteristics

  • Ammonia is a colorless gas with a sharp, penetrating odor.
  • It is a toxic gas and requires great care to prevent and control environmental release.
  • In pure form, it is known as anhydrous Ammonia and is hygroscopic (readily absorbs moisture).
  • Ammonia has 82.2% Nitrogen content.
  • The energy content of Ammonia is 18.8 MJ/kg while hydrogen’s is 120 MJ/kg.
  • At temperatures below –33°C, Ammonia turns liquid at atmospheric pressure.
  • Ammonia has a high ignition temperature so is commonly mixed with traditional fuels in internal combustion engines with air (gas form) or injected into the cylinder (liquid form). It can also be preheated to enhance combustion.

Ammonia transportation

  • Ammonia is usually shipped in the liquid state therefore it must either be compressed or refrigerated or some combination of the two.
  • It is transported in steel containers and requires special conditions for storage and handling. Ammonia storage tanks may be classified as fully refrigerated, semi-refrigerated or pressurized.
  • Prior to distribution, Ammonia loading temperature might be higher than the storage temperature due to temperature limitation of the truck/pipeline material.
  • Considerable infrastructure already exists for the transportation and storage of Ammonia, along with well-established safe handling procedures. This existing logistical infrastructure is a key advantage over hydrogen, and could enable the early adoption of large-scale transportation of Ammonia as an energy carrier and fuel.

Ammonia potential uses

  • In addition to its current main use in the fertilizer industry, green ammonia has the potential to play a role in other applications, especially if considered as part of a decarbonization strategy and can be used through direct combustion or by chemical reaction in a fuel cell.
  • The growing interest in the transportation sector as a shipping and marine fuel is primarily due to its zero-carbon emissions as well as its zero-sulphur content, which results in lower emissions and ensures compliance with IMO 2020 and IMO 2050.
  • Ammonia can also be burned directly in gas turbines for electricity production in a mixture with natural gas or hydro­gen. If ammonia is imported as a hydrogen carrier, burning it directly could eliminate the requirement for ammonia cracking (to reconvert it into hydrogen).