The energy conversion efficiency of

The energy conversion efficiency of FCE is intrinsically higher than internal combustionengines since it is not limited by Carnot cycle. The maximum theoretical electricalefficiency of the fuel cell stack can be 83%. Because of the internal resistance, etc., the practical electrical efficiency of the fuel cell could be 50–70% [4]. In Ref. [1], the efficiency properties of the single fuel cell have been analyzed theoretically. The expressions of the efficiency properties of the single fuel cell have been presented. But there is no further discussed. In Ref. [2], the efficiency properties of the fuel cell stack and these of the FCE have been studied using the simulation method. This reference has especially analyzed the properties of the fuel cell stack and that of the FCE under different control strategies. In Refs. [3,5,6] the efficiency properties of the fuel cell stack have been analyzed theoretically, and the theoretical expressions have also been presented, but they did not compare the theoretical value to the test data.