Actual state of technology in direct carbon fuel cells

At medium term, electricity could be partially provided by the utilization of carbon in high temperature fuel cells. The thermodynamic efficiency of a direct carbon fuel cell (DCFC) slightly exceeds 100% in a wide temperature range due to the positive value of the reaction entropy change. Thus, the thermodynamic efficiency is higher than those of conventional fuel cell types for gaseous fuels. In DCFC technology, three different main electrolyte concepts are used up to now: two types of liquid salt electrolytes (molten carbonate or molten hydroxide) and a solid oxide electrolyte (solid ceramic layer). For instance, it has been reported that power densities up to 210mWcm^-2 can been achieved at 750 °C in a molten carbonate based cell, resulting to a real practical efficiency of about 60%. Recently, also combined technologies have been developed in which a maximum power density of 500mWcm^-2 is possible. In this paper, the actual state of technology will be discussed for the different concepts of direct carbon fuel cells.