Design and part-load performance of a hybrid system based on a solid oxidefuel cell reactor and a micro gas turbine

This paper addresses the design and off-design analysis of a hybrid system (HS) based on the coupling of a recuperated micro gas turbine (MGT) with a high temperature solid oxide fuel cell (SOFC) reactor. The SOFC reactor mod el is presented and discussed, taking into account the influence of the rea ctor lay-out. the current density, the air utilisation factor, the cell ope rating temperature, etc. The SOFC design and off-design performance is pres ented and discussed: the design and off-design models of a recuperated micr o-gas turbine are also presented. The operating line, the influence of the micro gas turbine "variable speed" control, and the efficiency behaviour at part load are analysed in depth. Finally, the model of the hybrid system obtained by coupling the MGT and th e SOFC reactor, considering the compatibility (technological constraints) o f the two systems, is presented. The model allows the evaluation of the: de sign and off-design behaviour of the hybrid system, particularly when the M GT variable speed control system is considered. The thermal efficiency of t he hybrid system, taking into account its size (250/300 kW(e)). is notewort hy: higher than 60% at design point, and also very high at part load condit ions. Such a result is mainly due to the simultaneous positive influence of SOFC off-design behaviour and MGT variable speed control. Moreover, it is possible to recover the waste heat from the gas at the MGT recuperator outl et (T-gas is about 250 degreesC) for cogeneration purposes. (C) 2001 Elsevi er Science B.V. All rights reserved.