Renewable ammonia is increasingly seen as a carbon-free green fuel that paves the way for a new nitrogen-based energy economy. Its energy density per volume is almost twice that of hydrogen and it is easier to transport, store and distribute. As the market grows due to efforts by various companies (e.g. YARA) to achieve more environmentally friendly production, distribution channels for ammonia imports and ammonia refuelling technologies will follow. The project aims to promote the acceptance of ammonia as a synthetic fuel with no CO2 emissions. It focuses on a breakthrough in the direct conversion of NH3 fuel into electricity.
To this end, a new, promising process based on a membrane reactor is being implemented and experimentally characterised. The process is comparable to an internal short-circuit fuel cell, but without the typical electrical connections to avoid electrical losses. This makes the system much simpler and cheaper than a SOFC (solid oxide fuel cell). The chemical energy of the liquid ammonia is converted into a highly compressed gas (N2 + H2O) by means of so-called self-pressurised combustion in a pressure vessel with a constant volume. The energy is obtained through the expansion work with the aid of a gas expander, e.g. in a gas expander such as a steam turbine or an engine. Since high pressure increases the overall efficiency of the process, the membrane reactor consists of tubular ceramic membranes that can withstand very high external gas pressures. The membranes are conductive for oxide ions and electronic charge carriers and realise the internal electrical short circuit in a single element. They are also called MIEC (Mixed Ionic Electronic Conductor), ITM (Ion Transporting Membranes) and OTM (Oxygen Transporting Membranes). Similar to fuel cells, the thermodynamic efficiency of the process is not limited. In contrast to combustion engines, steam power plants or other processes based on the cycle of a working medium, a significantly higher efficiency is expected.
This project has been funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 951880.
Partner: INP Greifswald, ZBT GmbH, POLIMI, Fraunhofer IKTS, PBS, RANOTOR
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