Thermodynamics and 3E analyses of a high-temperature proton exchange membrane fuel cell-based CCHP system with cascade utilization of waste heat

Abstract

Hybrid hydrogen fuel cell energy systems have proven a promising way to reduce carbon emissions. To achieve the cascade utilization of waste heat, a high-temperature proton exchange membrane fuel cell-based combined cooling, heating, and power (PEMFCCCHP) with condensation heat recovery is proposed. The waste heat of PEMFC is used to drive an organic Rankine cycle and an absorption refrigeration cycle, while the low temperature waste heat of organic Rankine cycle and the absorption refrigeration cycle are used to heat domestic hot water. The PEMFCCCHP system is characterized using a validated model under different working conditions. The equivalent power density increases from 59.4 kW to 211.5 kW, as operating current density of PEMFC increases from 0.2 A/cm2 to 1.0 A/cm2, while the exergy efficiency of the integrated system decreases from 0.689 to 0.491. The maximum equivalent power density of 157 kW is obtained at the waste heat distribution ratio of 0.43, compared to 128 kW of the individual PEMFC system. Compared to the single PEMFC system and the PEMFCCCHP without condensation heat recovery, the exergy efficiency of the proposed system is improved by 22.6% and 10.4%, respectively. The system has the smallest fossil energy consumption and carbon emissions and the highest cost saving ratio under the wind-to-hydrogen technology, with the payback period of 4.5 years when the price of hydrogen is 5 $/kg.