An indirect ammonia fuelled solid-oxide fuel cell system with free cracking from waste heat

Peters, Benjamin Matthew, Huddart, Adam, Cowan, Richard, Smith, Jayke and Davenne, Tristan 2024. An indirect ammonia fuelled solid-oxide fuel cell system with free cracking from waste heat. Journal of Ammonia Energy 2 (1) , pp. 85-100. 10.18573/jae.33

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Abstract

A 100W scale indirect ammonia solid oxide fuel cell (IA-SOFC) system called REACH was designed, built and tested at the Rutherford Appleton Laboratory, with an off-the-shelf 100W solid oxide fuel cell at its core. IA-SOFCs with thermal integration of cracking have been modelled at a large scale, and there have been single cell studies focusing on the degradation and NOx emissions while running on ammonia. REACH addresses the gap of demonstrating an integrated system and only a few stack-scale demonstrators to have been tested in academia. The purpose of this work was to present an engineering design that demonstrates the practical possibilities of using the waste heat from high-temperature SOFCs to perform ammonia cracking, and to demonstrate a real-world efficiency of above 45% for such a system. Tests were conducted in a fume hood with gaseous supplies of air and ammonia. The start-up testing proved that the proposed design is capable of autothermal cracking. The performance mapping of the fuel cell, that is the sweeping of fuel rates at differing air-fuel ratios, revealed a system efficiency of 14%. Upon diagnosis, this was due to low fuel utilisation of the off-the-shelf SOFC at its intended operating condition, which the supplier’s anode reduction process is likely to have caused. This illustrated that the commercial availability of reliable SOFC stacks can be an obstacle to research in this field. However, an effective design was delivered that has practically demonstrated the use of waste heat and unconverted fuel to pre-crack for high temperature SOFCs (autothermal cracking without power input for heating), thus a direct ammonia to power system that avoids the need for upstream purification steps was delivered. Questions remain around the precise composition of its exhaust, and suggestions for a follow up prototype are to remove the vacuum vessel and scale-up the power rating of the system to the 1-10kW scale.

Item Type:	Article
Date Type:	Publication
Status:	Published
Publisher:	Cardiff University Press
ISSN:	2752-7735
Funders:	STFC
Date of First Compliant Deposit:	12 July 2024
Date of Acceptance:	22 June 2024
Last Modified:	26 Jul 2024 10:17
URI:	https://orca.cardiff.ac.uk/id/eprint/170570

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