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 $10×10 cm2$ 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 $20 μm$ and $40 μm$, respectively. $I-V$ and ac impedance characteristics of single cells were evaluated at an intermediate temperature $(650–800°C)$ by using hydrogen gas as fuel. The maximum power density of the $10×10 cm2$ anode-supported cells was about $0.32 W/cm2$ at $750°C$ and $0.2 W/cm2$ at $650°C$. In this work a 1 kW class SOFC stack composed of 37 cells $(10×10 cm2)$ 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 $1.3 kWe$. Detailed status and experimental results of the 1 kW SOFC system will be discussed in this paper.

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