Fuel flexibility of solid oxide fuel cells

Andre Weber

doi:10.1002/fuce.202100037

Abstract

AbstractOne of the major advantages of SOFCs is their high fuel flexibility. Next to natural gas and hydrogen, which are today's most common fuels for SOFC‐systems and cell‐/stack‐testing respectively, various other fuels are applicable as well. In the literature, a number of promising results show that available fuels as propane, butane, ammonia, gasoline, diesel etc. can be applied. Here, the performance of an anode supported cell operated in specialized single cell test benches with different gaseous and liquid fuels and reformates thereof is presented. Fuels as ammonia, dissolved urea (AddBlueTM), methane/steam and ethanol/water mixtures can directly be fed to the cell, whereas propane and diesel require external reforming. It is shown that in case of a stable fuel supply the cell performance with such fuels is similar to that of appropriate mixtures of H2, N2, CO, CO2, and steam, if the impact of endothermic reforming or decomposition reactions is considered. Even though a stable fuel cell operation with such fuels is possible in a single cell test bench, it should be pointed out that an appropriate fuel processing will be mandatory on the system level.

Highlights

Research on fuel flexibilityFuel flexibility is claimed to be a major advantage of solid oxide fuel cells
All tests are performed with state-of-the-art anode supported cells. Fuels such as hydrogen, methane, propane, diesel, an ethanol–water mixture, ammonia, and AdBlueTM are either directly supplied to the cell or a reformate composition, as analyzed at the outlet of an appropriate reformer, is supplied
In case of ammonia a cooling power of ∼5.7 W that is related to the endothermal decomposition of ammonia (0.167 nlm NH3) has to be expected, which resulted in a cell temperature decrease from 751.9◦C to 742.4◦C for operation with ammonia fuel

Summary

Introduction

Research on fuel flexibilityFuel flexibility is claimed to be a major advantage of solid oxide fuel cells. Fuels such as hydrogen (as a reference), methane, propane, diesel, an ethanol–water mixture, ammonia, and AdBlueTM are either directly supplied to the cell or a reformate composition, as analyzed at the outlet of an appropriate reformer, is supplied. In case of AdBlueTM and ethanol the measured OCV is ∼15 mV below the theoretical value, which might be related to deviations from the nominal fuel composition due to deviations in the supplied fuel mixture (31.8 to 33.2 wt.% urea according to DIN 70070) and an incomplete decomposition.

Results

Conclusion