The Potential Of Ammonia As Carbon-Free Fuel — Major New Research Project At The University Of Aarhus

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If You Think Hydrogen As Energy Carrier Means Trouble, Try Ammonia — New Research From Denmark Shows How

A major new research project at the Department of Engineering at Aarhus University can potentially revolutionize production of ammonia, traditionally an essential ingredient in fertilizers. However, the substance has the potential to revolutionize the entire energy and transport sector, if produced in a carbon-neutral manner that is, without the use of natural gas or coal, and without the huge demand for fossil energy currently entailed by ammonia production.

The experimental site is located at Foulum in Denmark, and this is a lucky spot when it comes to access to renewable energy. It’s the same location that Apple has chosen for building a large data centre. This area has huge capacity connections to the abundant wind turbines in western Denmark and an enormous 1.6 GW capacity HVDC connection to Norway making trading Danish wind and Norwegian hydro energy possible at large scale.

Lars Ditlev Mørck Ottosen, head of the chemical and biotechnology section at the Department of Engineering, Aarhus University:

“We have a particularly effective technology here at Foulum that enables us to make ammonia exclusively from electricity from certified wind turbines, water and air. The method is far more energy-efficient than conventional ammonia production, which today accounts for as much as 1% of the world’s total energy consumption.”

The production method uses no natural gas, oil, or coal like conventional and very energy-demanding ammonia production, which means that there is potential to save enormous amounts of fossil energy and CO₂. It’s the primary steps of producing the N₂ and H

₂ gasses that are most energy-efficient with the new method, whilst the synthesis of the ammonia end product (3 H₂ + N₂ → 2 NH₃) is the same as current technology.

“If the ammonia we produce in this way can also be certified as organic, we’ll be able to solve a huge problem for many farmers, and perhaps we’ll see a massive growth of organic farming,” says PhD student Christian Dannesboe.

But how is ammonia utilized as an energy carrier? I asked Christian Dannesboe to explain:

“Our purpose in producing ammonia is precisely that it can be burned as a liquid fuel. In the original application of the project, it was intended to prove ammonia as a liquid fuel by rebuilding a ships combustion engine to operate on ammonia. It’s quite a revolutionary feat to manage that. Very high-efficiency is desired, so there are still a number of lab experiments to be carried out that will reveal how close we can get to theoretical limits of ammonia production, and we therefore have to divide the application into several stages. The application we have been granted now will be used to prove a radical energy-efficient production of ammonia only on the basis of electricity, water and air. When this is in place, we will build engines that prove that we have found the Egg of Columbus, and finally have a carbon free solution for heavy traffic (ships, trains and the like). We will also show that ammonia can be converted back to electricity using fuel cells in this project. It can be done incredibly energy-efficient, but we do it first and foremost to show the potential of ammonia as an energy carrier, and not so much to revolutionize electricity production in general.”

Actually, according to ammoniaenergy.org, MAN Energy Solutions (formerly MAN Diesel & Turbo) is planning to have the first ammonia engine in operation by early 2022. Its marine engines are powering 50% of the world’s trade and the company believes that 3,000 of its current ME-LGIP Engines of sizes ranging from 5 to 85 MW using liquefied petroleum gas (LPG) or liquefied natural gas (LNG) can be converted to use ammonia.

The combustion of ammonia to nitrogen and water is exothermic and the base theoretical reaction is:

4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O

However, NOx emissions can be a problem with incomplete combustion and therefore a so-called Selective Catalytic Reduction (SCR) process is used where ammonia and an urea solution is injected at the exhaust resulting in only nitrogen and water as waste:

4 NO + 4 NH

₃ + O₂ = 4 N₂ + 6 H₂O

6 NO₂ + 8 NH₃ = 7 N₂ + 12 H₂O

There are several other challenges in ammonia combustion, such as low flammability and low radiation intensity. When the combustion dynamics are better understood, then even applications such as gas turbines may be viable. For starters, though, the huge 2-stroke piston ship engines seem like a good idea. In terms of safety, it’s important to note that even though ammonia is not explosive like traditional gas fuels, it is toxic for humans and has to be carried at sub-zero temperatures and high pressure in order to stay liquefied.

Project partners are Aarhus University, Energinet, Haldor Topsøe DTU, Vestas, Equinor, and Ørsted Wind Power. The EU Energy Technology Development and Demonstration Programme (EUDP) is supporting the project with $2.4 million out of a total budget of $4.1 million.

You can find more specifics on ammonia fueled engines at NH3 Fuel Association, and you can read the Department of Engineering’s own article at Aarhus University.