Exploiting the waste heat from an alkaline fuel cell via electrochemical cycles

Based on the current models of an alkaline fuel cell (AFC) and a thermally regenerative electrochemical cycle (TREC), a novel model of the hybrid system consisting of an AFC, n TRECs, and a regenerator is proposed. The maximum power output density of the hybrid system is calculated. It is found that when the regenerative efficiency of TRECs is in the 0.4-0.8 range, the maximum power output density of the hybrid system is about 1.46-1.77 times of that of the AFC. Moreover, the influences of the current density of the AFC and the regeneration efficiency of the TRECs on the performance characteristics of the hybrid system are discussed in detail. The choice criteria of main parameters are given. The performances of several AFC-based hybrid systems are compared. When the AFC is operated at 353 K, the maximum power output density of the AFC-TREC hybrid system is about 2 times of that of the AFC-TEG hybrid system, 2.42 times of that of the AFC-refrigerator hybrid system, 1.17 times of that of the AFC-heat driven hybrid system, respectively. The results obtained show that the proposed model can more efficiently harvest the waste heat released from AFCs than other AFC-based hybrid systems.