Monitoring & metering
adopted by some marine engine manufacturers, which involves ammonia dual fuelling, which is where some of the fuel oil (marine diesel) is replaced with ammonia as a retrofit solution. Typically, up to 40 per cent diesel is still used in these engines, which will have consequences for local pollution, and limit the scope for decarbonisation. “The vision of the EPSRC MariNH3
programme is therefore to investigate full decarbonisation of marine transport emissions through multidisciplinary research focused on highly promising disruptive ammonia fuelled engine concepts, which have the potential to allow full decarbonisation, whilst minimising pollution and end-use energy demand. “Our goal is to develop the best technical
solutions in parallel with appropriate acceptance criteria and policy, so that we can develop technologies and policies which are ‘right first time’ and appropriately scaled across the marine sector. “The MariNH3 framework is based around
a ‘technology agnostic’ approach to life cycle analysis to ensure that ammonia end-use is implemented appropriately. We wish to achieve this while developing the next generation of propulsion researchers, capable of adopting a technological and systems engineering approach to help steer and maintain the strong powertrain research community that we have in the UK.”
The climaTe imperaTive
In 2021, COP26 climate conference in Glasgow highlighted the insufficiency of the greenhouse gas emissions (GHG) reductions promised by the world’s nations in their nationally determined contributions (NDCs). Consequently, nations and the world’s leading organisations are urgently looking for ways to further reduce emissions, and a reduction in the use of fossil fuels is one of the more obvious alternatives. So- called ‘clean energy’ sources are therefore being rapidly developed. At the same time, rising energy prices are also helping to make renewable energy sources more attractive.
Why ammonia?
Green hydrogen, produced by the electrolysis of water using renewable energy, offers enormous potential in the decarbonisation of the energy sector as a whole. As a fuel, the
main advantage of hydrogen (H2) is that it does not contain carbon, so combustion emissions
do not contain CO2 (greenhouse gas) or CO. However, when burned in air hydrogen does produce harmful nitrogen oxides. With high flame speed and temperature, the
combustion characteristics of hydrogen differs from conventional fuels, but the main challenges with hydrogen relate to its storage and distribution. On a weight basis, hydrogen has a higher energy content than conventional fuels, but on a volume basis the situation is reversed.
Furthermore, the storage of hydrogen gas typically requires high-pressure tanks, and storage as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one atmosphere pressure is minus 252.8°C. So, if the question is ‘how do we exploit the advantages of green hydrogen?’ the
answer is: convert it to ammonia (NH3). Ammonia has a higher energy density
(12.7MJ/L) than liquid hydrogen (8.5MJ/L), and ammonia can be stored at a much less energy- intensive minus 33°C or it can be pressurised to about ten times atmospheric pressure. Ammonia is also less flammable than hydrogen, although it has an unpleasant odour and is toxic - breathing low levels may cause irritation to the eyes, nose and throat. High levels of ammonia may cause burns and swelling in the airways, lung damage and can be fatal. Hydrogen can be converted to ammonia via
the Haber-Bosch process which reacts hydrogen with atmospheric nitrogen under pressure. Historically, this process has been employed to manufacture agricultural fertilisers using natural gas (fossil fuel) as the source of hydrogen. However, this process is energy intensive and produces high levels of carbon dioxide emissions. In the past, ammonia has been regarded as a
useful medium for the transport of energy, so that it can be cracked into nitrogen and hydrogen at the point of delivery. However, the
Instrumentation Monthly August 2022
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