Performance assessment and parametric optimum selection of the hybrid system consisting of a direct ethanol fuel cell and three-heat-reservoir cycle.

A direct ethanol fuel cell is the device to directly convert the chemical energy of the ethanol and oxygen into the electricity and heat. To improve the electrical power density and increase the energy conversion efficiency as much as possible, a three-heat-reservoir refrigeration cycle is coupled to the direct ethanol fuel cell, so that the waste heat of the fuel cell can be effectively utilized. The performances of the direct ethanol fuel cell and hybrid system are systemically assessed and compared. The whole performance of the hybrid system is optimized. The maximum power densities of the hybrid system can attain, respectively, 0.20, 0.21, and 0.22 (Js-1cm-2), which are 1.41, 1.71, and 2.10 times those of the fuel cell, when the temperatures of the fuel cell are 328.15, 338.15, and 348.15 (K). The partial current densities, voltage output, and flow density of waste heat of the fuel cell, and coefficient of performance and cooling rate of the three-heat-reservoir cycle are determined at a given molar concentration of the inlet ethanol at the optimum power density, and consequently, the optimum selection criterion of the molar concentration of the inlet ethanol is obtained.