Harvesting waste heat produced in solid oxide fuel cell using near-field thermophotovoltaic cell

A coupled system consisting of a regenerator, a solid oxide fuel cell (SOFC), and a near-field thermophotovoltaic cell (NFTC) is proposed to recovery the waste heat from the SOFC. Based on the theories of electrochemical and fluctuation electrodynamics, analytical formulas for the power output and the energy efficiency of the coupled system are derived. The dependence of the matching area ratio between the subsystems on the key parameters is discussed. As the SOFC works at 1073 K, the two voltages of the subsystems are optimized. The maximum power output density of 1.01 Wcm(-2) and an efficiency of 0.402 are achieved for the proposed system. By comparing, to the performance of the single SOFC, the optimally working regions of the coupled system are determined. The effects of the SOFC's temperature and the NFTC's vacuum gap on the maximum power output density and the optimum operating conditions of the system are studied. One can find that the maximum power density in the near-field is 1.3 times than that in the far-field and better than the most of the other SOFC-based systems. The present work can provide a new route to efficiently utilize the waste heat of SOFC to achieve higher energy efficiency.