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“Green ammonia” is to be trialled as a form of energy storage with the opening of a pilot project in Oxfordshire next week.
The demonstration plant, reportedly the first of its kind in the world, will use renewable electricity to create ammonia from water and nitrogen, which will then be used to fuel an engine to recover the energy consumed in production.
Existing ammonia plants produce ammonia in vast quantities – mainly for fertilising crops – by combining hydrogen and nitrogen via the Haber-Bosch process. Natural gas and other fossil fuels provide both power and a source of hydrogen, meaning the process releases large amounts of carbon dioxide.
The new pilot project, developed primarily by Siemens, will instead use renewable electricity to extract hydrogen from water through electrolysis. Renewable electricity will also power the Haber-Bosch process, allowing ammonia to be produced without any carbon emissions.
When power is needed, the ammonia will be burnt in a reciprocating engine, converting the fuel back into nitrogen and water.
Siemens said although the presence of nitrogen could lead to the emission of nitrogen oxides, there are well-established selective catalytic reduction processes for removing nitrogen oxides from exhaust gases. The company added that ammonia combustion with low emissions of nitrogen oxides is being actively researched.
Energy can be also be released through combustion in a gas turbine, or by splitting the ammonia into nitrogen and hydrogen, and then using the hydrogen in a fuel cell.
Ammonia is already kept in large volumes for long periods and transported around the world by sea. Siemens said the fuel not only offers a potential source of long-range energy storage needed to fill extended gaps in renewable generation, but could also be used to export low-carbon energy to countries with limited local renewable resources.
Ian Wilkinson, programme manager at Siemens Corporate Technologies, said: “Meeting our decarbonisation targets is a big challenge for society today and demands a range of complementary solutions, including a variety of storage technologies.
“Carbon-free chemical energy storage – including green ammonia – has the potential to work alongside other storage methods such as batteries, and help increase the penetration of renewable power into our energy systems.
“This demonstrator, and the work we’ve done with colleagues from academia, shows that green ammonia is a viable option and can help reduce carbon emissions from existing industrial processes as well as provide a means for transporting and storing renewable energy in bulk.”
The pilot project is a collaborative effort, also involving the Science and Technology Facilities Council, Oxford University and the University of Cardiff. Siemens has invested £500,000, whilst Innovate UK has provided £1 million of funding.
The facility will open on 26 June.
Earlier this month, Highview Power opened the world’s first grid-scale liquid air energy storage plant near Manchester.
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