A comparative thermodynamic investigation with environmental analysis of SOFC waste heat to power conversion employing Kalina and Organic Rankine Cycles

A comparative energy and exergy analysis is reported of employing Organic Rankine and Kalina cycles for waste heat recovery from hybrid SOFC/GT system. The considered SOFC/GT system, which is fed by methane, includes both external and internal reformers with anode gas recycle. Thermodynamic models are developed for SOFC/GT system and the two proposed combined cycles and the effects of important parameters are investigated on the cycles' performances. An environmental impact assessment in terms of carbon dioxide emissions is also carried out. The results provide a good motivation for employing ORC or Kalina cycle for waste heat recovery from SOFC/GT system to enhance the overall energy conversion efficiency. The results revealed the superiority of the ORC over the Kalina cycle in this case. The results showed that an exergy efficiency of 62.35% is achievable for the combined SOFC/GT-ORC system while the exergy efficiency of the combined SOFC/GT-KC system reaches 59.53%.