Ammonia Fuel Cells: SOFC stack test and system analysis

By Trevor Brown on October 07, 2016

New research, recently published in the International Journal of Hydrogen Energy, demonstrates that solid oxide fuel cell (SOFC) systems fueled with ammonia could be “more efficient than equivalent hydrogen-based” systems.

This new paper comes out of the Fuel Cell Lab at the University of Perugia, in Italy, and builds upon years of research coming out of that laboratory on the use of ammonia and urea in fuel cells.

Decomposition of ammonia introduces an endothermic reaction that permits heat absorbance in the anode and a better control of stack temperature. Based on tests results, a thermodynamic model of a complete system was designed and studied. The results demonstrate that the ammonia fueled SOFC is more efficient than an equivalent hydrogen fueled one, due to the cooling effect of internal reactions that reduces ancillaries energy consumptions related to cathode air flow.
SOFC operating with ammonia: Stack test and system analysis (Giovanni Cinti, et al), International Journal of Hydrogen Energy, 08/17/2016

These latest findings are based on SOFC tests “using both pure and diluted ammonia,” which is more often called aqueous ammonia in industrial markets. The use of aqueous ammonia demonstrates “an additional route for efficient power production.”

A previous paper by the same team, published in 2015, focused on urea as the fuel source, because urea is “widely available … safe to be handled and used, and can be recovered from biomass or water treatment plants as a byproduct.”

Urea decomposition was studied and reproduced in the experimental activity to evaluate its effect on the performance of SOFCs. A gas stream, obtained by simulating decomposed urea with technical gases mixtures, was fed into an SOFC stack, varying the operational temperature and the steam to carbon ratio. Experimental results produced efficiencies higher than 40%. Based on experimental data a 0-D model was developed and operational conditions were expanded, reaching an overall efficiency of 60%.
SOFC fuelled with reformed urea (Giovanni Cinti, et al), Applied Energy, 09/15/2015

Both of these recent studies draw on work that started in 2014, under the direction of Umberto Desideri, who is now at the University of Pisa.

The paper reports experimental test performed to evaluate the feasibility of NH3 directly fed to a 50 cm2 single cell SOFC … The study of temperatures and of heat flows show how the cell is cooled down to lower temperature because of heat adsorbed by the reaction and by flow mix entering the anode. The study shows also how for operative temperatures below 800 °C the cracking reaction takes place in the cell active area. Efficiency test demonstrates that the cell can operate at 300 mW cm–2 and 30% efficiency.
Experimental Analysis of SOFC Fuelled by Ammonia (Umberto Desideri, et al), Fuel Cells, April 2014