Fabrication and Demonstration of 1 kW Class SOFC Stack and System for Residential Power Generation Application

The planar type 1 kW class solid oxide fuel cell (SOFC) stack using metallic interconnects such as ferritic stainless steel has been developed for application in a residential power generation system. For the intermediate temperature operation of the SOFC, a higher performance of anode-supported single cells of 10x10 cm(2) with a thin electrolyte layer of yttria-stabilized zirconia were fabricated by slurry coating, and their performances were improved by a microstructure-controlled anode substrate and by introducing alternative cathode materials. The thicknesses of the electrolyte and the cathode layers were about 20 mu m and 40 mu m, respectively. I-V and ac impedance characteristics of single cells were evaluated at an intermediate temperature (650-800 degrees C) by using hydrogen gas as fuel. The maximum power density of the 10x10 cm(2) anode-supported cells was about 0.32 W/cm(2) at 750 degrees C and 0.2 W/cm(2) at 650 degrees C. In this work a 1 kW class SOFC stack composed of 37 cells (10x10 cm(2)) was successfully manufactured and a SOFC system with balance of plant (BOP) (reformer, heat exchanger, catalytic burner, etc.) integrated for combined heat and power. The system designed for power generation by using a natural gas as fuel can concurrently produce electricity at a SOFC stack and hot water from recuperating heat. The system showed a maximum dc output of 1.3 kW(e). Detailed status and experimental results of the 1 kW SOFC system will be discussed in this paper.