In past years, SOFC technology has shown much progress on material development, stack development, and prototype system demonstration; and some of the proto system are evaluated to be very close to the commercial phase. However, for the SOFC system to be competitive to the large scale power generation technologies, such as gas turbine combine cycle, coal power plant, efficiency should be further improved.
The ways of improving efficiency are classified as (a) improving performance of fuel cell stack, (b) reducing BOPs' power consumption, (c) optimizing the cycle structure and operating condition, and importantly, (d) hybridization of fuel cell system by combining fuel cell with other power units.
In this presentation, a novel concept of SOFC hybrid power generation system, an SOFC-engine hybrid, will be introduced and the proof-of-concept test results of 5kW system will be presented. The SOFC-engine hybrid system consists of an SOFC stack, an HCCI type internal combustion engine, an external reformer, an air blower, a fuel supply system, a demi-water pump, an air heat exchanger, a steam generator, and other control units.
Test results, at low fuel utilization such as 50%, reveal that the SOFC and HCCI engine generate 2.96 kW and 1.36 kW, respectively; the power share is around 2:1. However at higher fuel utilization, the power share ratio of engine has decreased; the SOFC and engine generate 3.82 kW and 0.79 kW at 60% fuel utilization, 4.25 kW and 0.42 kW at 70% fuel utilization, respectively.