Among the numerous modern, high-efficiency energy technologies allowing for the conversion of chemical energy of coal into electricity and heat, the Direct Carbon Fuel Cells (DCFC) deserve special attention. These are devices that allow, as the only one among all types of fuel cells, to directly convert the chemical energy contained in solid fuel (coal) into electricity. In addition, they are characterized by high efficiency and low emission of pollutants. The paper reviews and discusses previous research and development works, both around the world and in Poland, into the technology of direct carbon fuel cells with an alkaline (hydroxide) electrolyte.
The influences of various operating conditions including cathode inlet air flow rate, electrolyte temperature and fuel particles size on the performance of the direct carbon fuel cell DCFC were presented and discussed in this paper. The experimental results indicated that the cell performance was enhanced with increases of the cathode inlet gas flow rate and cell temperature. Binary alkali hydroxide mixture (NaOH-LiOH, 90-10 mol%) was used as electrolyte and the biochar of apple tree origin carbonized at 873 K was used as fuel. Low melting temperature of the electrolyte and its good ionic conductivity enabled to operate the DCFC at medium temperatures of 723-773 K. The highest current density (601 A m−2) was obtained for temperature 773 K and air flow rate 8.3×106 m3s−1. Itwas shown that too low or too high air flow rates negatively affect the cell performance. The results also indicated that the operation of the DCFC could be improved by proper selection of the fuel particle size.