Second Law Analysis of Solid Oxide Fuel Cell Integrated With Reheat and Regenerative Braysson System and Steam Generation Unit

ABSTRACT

Global energy requirements are continuously rising, posing significant challenges to sustainable energy development. Thus, research on energy utilization has become a necessity now more than ever before. Historically, the heat waste from fuel cells has been harnessed to generate additional power via Rankine or Brayton cycles. This study aims to conduct a comprehensive exergy analysis of a cogeneration setup incorporating a high‐temperature solid oxide fuel cell (SOFC) integrated with a closed‐loop Reheat and Regenerative Braysson Cycle coupled with a steam generator. While SOFC possesses the potential to operate on any kind of hydrocarbon fuel for direct energy conversion, the Braysson cycle, which is a merger of two power cycles (Brayton & Ericsson cycles), is proven to outperform a conventional Brayton cycle. The temperature at which SOFC operate is 950°C, while the Braysson cycle is designed to operate with a turbine inlet temperature (TIT) between 400 and 900°C. In order to attain maximum output power and efficiencies, distinct values of optimum pressure ratio exist. A range of TITs and pressure ratios was evaluated to assess the exergy efficiency of the integrated system and to quantify exergy destruction across individual components as well as the overall setup. The analysis reveals that the afterburner contributes the most to overall exergy destruction, reaching a maximum of 116.28 kW. Individually, the SOFC demonstrates an exergy efficiency of approximately 16%. Nonetheless, when integrated with the Braysson cycle and supplemented by steam generation, the system's exergy efficiency improves substantially, reaching 46.5% at 900°C and an optimal pressure ratio of 2.7. A considerable performance gain is observed in the hybrid system in contrast to the standalone fuel cell.