Integration of solid oxide fuel cells into gas turbine power generation cycles. Part 2: Hybrid model for various integration schemes

Abstract

The second part of this paper deals with modelling gas turbine cycles integrated with a fuel cell model to produce hybrid cycles. The main objectives were to develop an understanding of the integration options and to determine the theoretical optimum configuration. Six different realistic cycles are analysed and discussed. The fuel cell model is detailed in Part 1 of this paper. The gas turbine cycles considered included intercooling, reheat and recuperation. The choice of hybrid configuration will depend on the application, but from this analysis it is shown that a recuperated gas turbine cycle with a fuel cell ahead of the combustor is a good choice for power generation at small/medium scale. This cycle achieved a thermal efficiency of 64.1 per cent at a relatively low pressure ratio of 14; the specific power, although lower than that of other configurations explored, was found to be reasonable at 520 kW/kgs. The addition of an intercooler to this cycle indicated a further increase in efficiency at 69.6 per cent and a considerable increase in specific power; the corresponding pressure ratio was 30, which would lead to a significantly different gas turbine. The maximum efficiency of all cases was found for a cycle containing a primary fuel cell (ahead of the combustor) and a reheat fuel cell (in-between the high-pressure and low-pressure turbine) with a numerical value of 76.4 per cent at a low pressure ratio but leading to a much reduced power (200 kW/kgs); a peak specific power of 489 kW/kgs was found but at much higher pressure ratios.