A feasible way to handle the heat management of direct carbon solid oxide fuel cells

A novel integrated system consisting of an external heat source, a direct carbon solid oxide fuel cell (DC-SOFC), a vacuum thermionic generator (VTIG) and a regenerator is proposed to handle the heat management of the DC-SOFC. The electrochemical/chemical reactions, ionic/electronic charge transport, mass/momentum transport and heat transfer are fully considered in the 2D tubular DC-SOFC model, which shows that the overall heat released in the cell is always different from the heat required by the internal Boudouard reaction. Three different operation strategies of the proposed system are presented, and accordingly, analytical expressions for the overall power output and efficiency for the proposed system are specified. The results show that the VTIG could effectively recover the waste heat for additional power production at a large operating current density, and the maximum power density and efficiency of the proposed system could reach more than 8100 W m−2 and 60% at 30,000 A m−2 and 1173 K, respectively. The effects of the operating current density, the operating temperature and the distance between the carbon layer and anode of the DC-SOFC, and the size, anode temperature and work function of the VTIG on the performance of the proposed system are discussed through comprehensive parametric studies.