Development of segmented-in-series-type solid oxide fuel cells for residential applications

Segmented-in-series-type solid oxide fuel cells (SIS-SOFCs) have been developed for residential applications. The average stack voltage of the SIS-SOFC with a fuel consisting of CH₄ (steam/carbon = 2.5) was 0.75 V and 0.24 A/cm² at fuel utilisation = 70.1%, yielding a direct current lower heating value (LHV) energy conversion efficiency of 50.6%. The degradation ratio, the ratio for thermal cycling, and the ratio for redox cycling were 0.62%/1000 h, 0.11% per cycle, and 0.04% per cycle, respectively. A micro combined heat and power (m-CHP) SOFC system was fabricated and successfully demonstrated for over 4000 h. The degradation ratio of 0.75%/1000 h was almost the same as that of the stack in a furnace. An LHV alternating current electrical efficiency of over 40% and LHV heat recovery efficiency of over 35% was achieved. Thus, SIS-SOFCs are suitable for m-CHP SOFC systems.