Thermodynamic analysis and optimization of a novel hybrid system using thermoacoustic cycle to harvest waste heat of high temperature PEMFC

The high temperature proton exchange membrane fuel cell (HTPEMFC) shows multiple advantages over the traditional PEMFC. To achieve the waste heat effective utilization of the fuel cell, a novel hybrid system mainly including a HTPEMFC and a thermo-acoustic cycle (TAC) is proposed. By considering the major irreversible losses, such as ohmic, concentration and activation losses, regenerative loss, heat transfer loss between the HTPEMFC and the TAC, and heat leak loss from the HTPEMFC to the environment, the expressions for the output power and energy efficiency of the proposed system are obtained. Based on typical conditions, the maximum power density for the proposed system increases by 33.3% compared with a single HTPEMFC system, and the corresponding energy efficiency also improves by 34.5%. The sensitive analysis is represented, and coupling a TAC unite to recover the HTPEMFC waste heat shows significant advantages by comparing with other available HTPEMFC-based hybrid systems. Finally, the proposed system is optimized using ideal point method based on the multi-objective optimization. The optimal power density is 6147.8 W m⁻², and the optimal efficiency is 53.9%. This work proves the feasibility of the HTPEMFC-TAC system, and hints the broad prospect of low-grade heat collections through a TAC.