Thermodynamic assessment of a system configuration strategy for a cogeneration system combining SOFC, thermoelectric generator, and absorption heat pump

For the promotion of solid oxide fuel cells (SOFC), it is essential to improve the applicability of cogeneration systems based on SOFCs in buildings. In this study, a cogeneration system which uses a thermoelectric generator and an absorption heat pump to recover the waste heat of SOFC exhaust gas was proposed. Based on the cogeneration system, a novel system configuration strategy that can adjust the system's heat-to-power ratio was developed. By implementing this strategy, four configurations (in which the locations of the waste heat recovery components are different) were formed. A mathematical model was established to evaluate the thermodynamic performance of the system. In order to make use of the cold fluid of the thermoelectric generators, the influence of the circulating water utilization mode on system performance was firstly studied. Second, the performance differences among the four configurations under the designated and variable conditions were analyzed. The results demonstrate that the mode in which water is cycled between the thermoelectric generator and the absorber of the absorption heat pump is the most efficient. By implementing the aforementioned configuration strategy, the system's heat-to-power ratio can be adjusted within two intervals ranging from 0.8 to 2.4 and from 4.2 to 9.5. Therefore, this novel configuration strategy for the cogeneration system delivers superior performance in responding to the needs of the energy demand side, and thus can help widen the application scenarios of SOFC cogeneration systems.