Green ammonia |
Powering the energy transition
Green ammonia is being increasingly recognised as a cost effective way of transporting green energy over long distances, and also as a potential fuel. It is relatively easy to liquefy and has a much higher volumetric energy density than liquid hydrogen. Ammonia (albeit grey) also has the advantage of already being a globally traded commodity, with a mature transport infrastructure
Stephen B. Harrison sbh4 consulting, Germany
Above: Ammonia storage spheres
E-fuels such as ammonia and methanol are derived from hydrogen or syngas generated by electrolysis. When the electricity flowing to the electrolyser is from renewable sources such as hydropower or PV solar power, the e-fuels are regarded as renewable, or green. The first MW-scale green ammonia project was implemented in 1928 in Norway. The Rjukan facility started up in 1928 with 165 MW of power flowing to 150 electrolyser modules generating 27 900 Nm3
/h of green hydrogen.
At a similar scale, also using Norwegian hydropower, Glomfjord commenced in 1949. Both schemes used atmospheric pressure, alkaline electrolysis. The H2
was converted to ammonia to
produce ammonium nitrate, a fertiliser. In a similar setup to the two Norwegian projects, hydropower from the Aswan dam was used to generate green hydrogen. One facility was built using Demag electrolysers in 1959. It had a total of 203 MW capacity of atmospheric pressure alkaline electrolysers across 288 modules generating 36 000 Nm3
A slightly smaller system was implemented
using equipment from BBC Electrolyzer System Oerlikon in 1973. As with the case in Norway, the goal was to make ammonia for fertilisers to increase the yield of local food production.
The revival of green ammonia in the 2020s
/h of hydrogen.
Looking to the more recent past, for several years now, attention has focused on green hydrogen as a clean energy vector. The motivation to produce green ammonia from green hydrogen includes the historic reason: production of nitrogen fertilisers. But the demand for green ammonia and e-fuels will grow as they are increasingly recognised as being cost-effective ways of transporting green energy over long distances. Conversion of hydrogen to ammonia or e-methanol adds cost at the production location but means that energy-dense liquid ammonia or liquid methanol can be shipped to the end-user location. These fuels are more cost effective to ship long distances than hydrogen which has a comparatively low volumetric energy density as a compressed gas or liquid.
30 | January/February 2023|
www.modernpowersystems.com
Ammonia is easily liquefied and has a volumetric energy density about 50% higher than liquid hydrogen.
The savings in shipping costs of liquid ammonia, compared to liquid hydrogen, mean that capex and opex savings from the shipping operation can be routed to the ammonia synthesis facility.
One of the attractions of using ammonia as a tradeable energy vector is that it is already a globally produced and traded commodity. Worldwide grey ammonia production is currently around 185 million tonnes per year. The global merchant market for traded grey ammonia is circa 20 million tonnes per year. 170 ammonia tankers sail the world’s oceans shipping these merchant ammonia volumes across 120 portside ammonia terminals. A typical ammonia tanker can transport 60 000 tonnes of liquid ammonia and a terminal would typically be built to store twice this capacity.
The maturity of the ammonia transportation infrastructure is an attractive reason for considering the use of green ammonia as a
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