Performance evaluation of an integrated proton exchange membrane fuel cell system with ejector absorption refrigeration cycle

Abstract

Absorption chiller systems are advantageous to vapor compression cooling systems due to capability of utilizing low-grade heat sources such as waste heat from industries, renewable energies, and generated heat by fuel cell. The main issue in absorption cooling system is the low cycle coefficient of performance (COP) that can be addressed by integrated ejector-absorption cooling systems. In this study, an integrated system of proton exchange membrane (PEM) fuel cell that thermally drives an ejector-absorption refrigeration cycle is proposed. The effects of generator temperature, condenser pressure, evaporator pressure, and inlet fuel mass flow rate to the fuel cell on the ejector entrainment ratio (ϕ) and COP are evaluated. Moreover, the performance of the integrated system is evaluated at different geometrical and operating conditions of PEM fuel cell. The results reveal that the ϕ and COP parameters increase up to 18.51% and 48% by increasing the generator temperature from 70 °C to 100 °C, respectively. At higher inlet mass flow rate of fuel to the reformer, the cooling capacity and the system COP improve. Furthermore, the maximum value of ϕ and COP are 0.39 and 0.77, respectively, at the best operating condition of the PEM fuel cell, i.e. the current density of 0.75 A/cm2. It is also concluded that the system overall energy efficiency at temperature of 80 °C and the current density of 0.5, 0.6, 0.75, and 0.85 A/cm2 are 43%, 39%, 35%, 32%, and 37%, respectively. Moreover, the COP of absorption chiller with ejector at the operating pressure of 1 bar and the temperature of 80 °C for PEM fuel cell is 6.7% higher than conventional absorption chiller.