A cost-efficient path to utilize coal via solid oxide fuel cells and alkali metal thermoelectric converters

In addition to directly burning in firepower plants, coal can be alternatively gasified into gaseous carbon monoxide and then fed into solid oxide fuel cells for efficient power generation. Carbon monoxide solid oxide fuel cells (CO-SOFCs) not only avoid the drawbacks of expensive hydrogen fuel but also facilitate carbon dioxide's separation and enrichment. In this paper, an integrated system is first presented to efficiently recycle the waste heat released from CO-SOFCs via alkali metal thermoelectric converters (AMTECs) for additional electricity generation. Key performance indicators such as power density and energy efficiency are mathematically expressed by including the heat-transfer losses between heat sources and AMTEC. The maximum power density of the integrated system gains 18% improvement compared with that of the sole CO-SOFC. The maximum efficiency can reach 60.84%. The optimum ranges of the current density, efficiency, and power density for the whole integrated system are determined. Furthermore, the influences of the fuel cell temperature on the optimum ranges are also studied. The correlations between the critical parameters and the maximum power density and efficiency of the system are revealed. The maximum power density and efficiency as well as the corresponding parameters are calculated numerically. The findings show that waste heat can be recycled efficiently by employing AMTECs. Novelty Statement A numerical model of the CO-SOFC/AMTEC integrated system is established. The maximum efficiency of the hybrid system can reach 60.84%. The optimum ranges of key parameters are determined and discussed.