Thermodynamics and flexibility assessment on integrated high-temperature PEMFC and double-effect absorption heating/cooling cogeneration cycle

High-temperature proton exchange membrane fuel cell (HT-PEMFC) is promising in the next-generation integrated energy systems, because of its reliability, controllability and high-grade exhaust heat which enables the operation of combined heating, cooling and power generation (CCHP). However, the conventional HT-PEMFC based CCHPs suffers from the electric-thermal coupling, which is incompatible with the varying electricity and heating/cooling loads. To this end, a double-effect absorption heating/cooling cogeneration cycle (DACC) is proposed to decouple the production of electricity and heating/cooling, by flexibly adjusting the ratio of the vapor distributed to the branches of turbine and evaporator. The mathematical model is developed and validated, based on which the parametric analysis is characterized under different conditions. Under the heating cogeneration mode, the overall efficiency of the system is improved by 5.9-26.2% compared with the single HTPEMFC. The maximum overall efficiency is 0.4797, corresponding the current density of 0.23 A/cm2. Under the cooling cogeneration mode, the system cooling capacity, net power, and cooling/power ratio can be adjusted in the range of 17.78-137.55 kW, 77.46-156.3 kW and 0.19-1.21, respectively. Owing to the flexible adjustment ability, the HT-PEMFC-DACC system can serve as an effective solution in future zero-carbon distributed energy systems.