Multi-criteria assessment and optimization study on 5 kW PEMFC based residential CCHP system

This paper presents a multi-criteria assessment (including thermodynamics, economics and environment) study on 5 kW PEMFC based residential combined cooling, heating and power system (CCHP). The system is mainly composed of a 5 kW PEMFC stack, a heat recovery system, a small absorption chiller and auxiliary component (including gas compressor and humidifier), which can provide electric power, space heating/cooling and hot water for apartment simultaneously. The thermodynamic model of the CCHP system is partially validated. The system performances, including energy and exergy efficiencies, annual cost and pollutant emission reduction, are evaluated in a parametric analysis method. Moreover, aiming at improving the evaluation indexes, the system is optimized using evolution algorithm, and three dimensional (3D) Pareto solutions and optimal operating parameter set are obtained. The results indicate that low operating temperature, high relative humidity and pressure of inlet gases are helpful for improving system exergy efficiency and GHG emission reduction. The optimized system exergy efficiency, annual cost and GHG emission reduction at Final Optimal Point (FOP) are 39.9%, 29337.3$ and 1.82 ×107 g, respectively. Comparing with un-optimized system, the system working at optimal parameters shows better performances in both exergy efficiency and GHG emission reduction besides a sacrifice in economic cost.