An improved operation strategy for CCHP system based on high-speed railways station case study

Operation strategy significantly affects the economic and environmental performance of combined cooling, heating and power (CCHP) system. An improved strategy following balanced heat-electrical load (FBL), which includes three sub-strategies of various redundant energy, was proposed for a CCHP system with heat pump. The proposed FBL strategy was applied to a CCHP system in a high-speed railway station, and the performance of FBL strategy was compared with that of following hybrid electric-heating load (FHL) strategy. The optimal rated gas turbine capacity was optimized firstly under various strategies to guarantee the fairness of comparison. The primary energy consumption rate, CO₂ emission reduction rate, operating cost savings rate and comprehensive performance matching (CPM) parameter of the CCHP system were adopted as criteria to evaluate the system performance. Results showed that all the criteria were improved by using FBL strategy with the CPMs of the three sub-strategies increasing 20.82%, 14.8% and 18.52% respectively. Secondly, high relevance was observed between CPM and the thermoelectric ratio. Based on analyses of other two typical loads of Harbin and Kunming, a linear function was developed between the CPM and the load thermoelectric ratio, which can provide a direct and convenient method to evaluate the CCHP performance. Finally, the sensitivity analysis of the electricity price to gas price ratio indicated that the CCHP system was not applicable when the ratio was less than 1.79. The amount of redundant energy could not be adopted as a criterion for the system performance in the comparative analysis of various operation strategies, but the increasing redundancy energy led to the degradation of the system performance under the same operation strategy.