Optimization research on round-trip efficiency of a CHP system based on 10 kW-grade unitized regenerative fuel cell

The unitized regenerative fuel cell (URFC) integrates fuel cell and water electrolyzer into the same device, and the round-trip efficiency (RTE) is considered as an important criterion for evaluating its comprehensive per-formance. A model of URFC-based combined heat and power (CHP) system is developed, which takes into ac-count the energy consumption of the components, and conducts orthogonal matrix analysis in three dimensions, including operating current density, temperature and pressure, to quantitatively evaluate the RTE of the CHP system based on URFC. The results show that the RTE of the system exceeds 75 % when the operating current density in FC mode lower than 0.6 A/cm2, and the operating current density in WE mode is between 1.4 A/cm2 and 3 A/cm2. The RTE of the system increases at lower FC temperatures, although the electrical output efficiency is lower. Compared to the working pressure of 1 atm in FC mode, the RTE of the system increases by 0.6 % at the working pressure of 3 atm. In addition, an adaptive optimization strategy is proposed, by adjusting the working current density in the two operating modes and controlling the temperature in the FC mode, which enables a proportional delivery of thermal and electrical energy according to demand and ensures high system efficiency.