A Single‐Chamber SOFC Stack: Energy Recovery from Engine Exhaust

The feasibility of applying single-chamber solid oxide fuel cells (SC-SOFCs) to power generators for exhaust energy recovery was investigated using both model and actual exhaust gases. In the experiments with model exhaust gases, a single cell, Ni-Ce0.8Sm0.2O1.9/YSZ/La0.8Sr0.2MnO3, was operated in a mixture of gases containing ppm levels of CH4, C2H6, C3H8, C4H10 and O2. The cell performance was considerably affected by the molar ratio of total hydrocarbons to O2, the operating temperature and the gas flow rate. The optimal operating conditions of the SC-SOFC were found to be similar to those found in actual exhaust from gasoline engines. Thermal and mechanical loading performance tests demonstrated high tolerance towards thermal cycling and breakage of the electrolyte. Performance tests with and without a gas separator suggested that there is no requirement for a gas separator in an actual exhaust. In the experiments with actual exhaust gases, a 12-cell stack was installed to a 250-cm3 engine. The open circuit voltages (OCVs) were between 5 and 8 V and independent of the number of revolutions, but were lower than the values expected from the model exhaust results. This was considered to be due to the deviation of the actual exhaust gases from the model gases. Nevertheless, the stack performance was reproducible and stable in the range from 1,500 to 5,500 rpm. The resultant peak power reached above 1 W at 4,500 rpm.