Thermo-economic Optimization of a Solid Oxide Fuel Cell, Gas Turbine Hybrid System

Large scale power production benefits from the high efficiency of gas-steam combined cycles. In the lower power range, fuel cells are a good candidate to combine with gas turbines. Such systems can achieve efficiencies exceeding 60%. High temperature Solid Oxide Fuel Cells (SOFC) offer good opportunities for this coupling. In this paper, a systematic method to select a design according to user specifications is presented. The most attractive configurations of this technology coupling are identified using a thermo-economic multi-objective optimization approach. The SOFC model includes detailed computation of losses of the electrodes and thermal management. The system is integrated using pinch based methods. A thermo- economic approach is then used to compute the integrated system performances, size and cost. This allows to perform the optimization of the system with regard to two objectives: minimize the specific cost and maximize the efficiency. Optimization results prove the existence of designs with costs from 2400 $/kW for a 44$/kW for a 70% efficiency. Several design options are analysed regarding, among others, fuel processing, pressure ratio or turbine inlet temperature. The model of a pressurized SOFC-microGT hybrid cycle combines a state-of- the-art planar SOFC with a high speed micro gas turbine sustained by air bearings.