Study of thermal effects in ammonia-fueled solid oxide fuel cells

Abstract

Ammonia is regarded as a promising alternative to hydrogen because of its high hydrogen content, ease of transportation and storage, and other favorable properties. However, in ammonia-fueled solid oxide fuel cell (SOFC), the intense heat absorption and excretion of ammonia decomposition and electrochemical reactions can lead to inhomogeneous temperatures inside the cell, which restricts long-life operation. For this reason, a three-dimensional tubular solid oxide fuel cell thermo-electrochemical model is established to explore the thermal characteristics when using ammonia as the fuel. The errors between the power density and voltage obtained from the numerical model and the experimental data in the literature are less than 5 %, which proves the accuracy of the model in this paper. Further parametric simulations reveal that the electrochemical performance and heat production rate are strongly affected by the operating voltage. And a peak power density of 66.4 mW/cm2 is obtained at an operating voltage of 0.45 V. Additionally, increasing the inlet temperature and increasing the fuel flow rate are beneficial for improving cell efficiency, although achieving temperature uniformity remains a challenge. The ammonia pre-reforming degree can be adjusted to effectively improve the temperature distribution uniformity within the cell and improve its internal heat balance. The maximum temperature difference in 96 % pre-reformed SOFC is only 22 K, while it reaches 167 K in direct ammonia SOFC. The temperature and electrochemical performance laws revealed in this study provide a theoretical basis for the optimization of ammonia-fueled SOFC.