Study On System Integration Of Combined Cooling Heating And Power System Based On Hybrid System

The Continuing growth in energy consumption demands and increasingly serious environmental pollution problems are greatly restricting the sustainable development of China’s economy.The combined cooling,heating and power(CCHP)system as an important measure of energy-saving and emission reduction has been vigorously promoted in China.Due to lack of consideration of the relationship between user’s demands and energy supplies,when the user load fluctuates violently,the combined system regulation performance is poor.Thus,the current CCHP systems have low efficiency in actual operation process.In order to improve the efficiency of the CCHP system in actual operation process,this dissertation has studied the matching relationship between supply and demand in CCHP system and conducted researches on CCHP system from system integration,variable operating conditions control,multi-index comprehensive evaluation and practical case study based on national key scientific research projects.This dissertation has introduced the axiomatic design method to analyze the supply side and the demand side of a typical CCHP system.Based on the analysis results,the supply and demand matching design method for CCHP system is proposed.The matching coefficient between the energy supply and the user demand of the CCHP system had been defined based on the energy matching graph,which quantitatively reflects the matching relationship between the user’s demand and the system energy supply.At the same time,different operation control measures of the CCHP system had been put forward under different user load demands based on the energy matching graph method,which providing support for improving the performance analysis of CCHP system.The design and partial load calculation models of the CCHP system’s components had been established,including compressor,turbine,combustion chamber and heat exchanger and so on.Based on the component calculation models,the basic circulation system models of basic gas turbine cycle and absorption refrigeration system were built.Then a variable condition analysis model of typical CCHP system was established based on the basic cycle calculation models and the principle of comprehensive cascade utilization of energy.The performance analysis and exergy distribution analysis of the CCHP system under different working conditions had been conducted based on the model.The results revealed that the CCHP system’s efficiency under partial load decrease due to equipment’s poor partial load performance and strong coupling relationship between the devices.In order to improve the exergy efficiency of the CCHP system,a MGT-ORC-ARC system is proposed.The performance analysis and exergy distribution analysis of the proposed combined system had been conducted.The impact of the six different working fluids on the system performance had been also researched.In order to improve the equipment’s partial load performance and reduce the coupling relationship between devices,waste heat supplementation control measures,ORC(organic Rankine cycle)control measure and MCR(mechanical compression refrigeration)control measure have been proposed based on the energy matching graph method.The performance of these operation control measures had been analyzed combined with specific user load fluctuations in detail.The results showed that ORC control measure and MCR control measure could effectively improve the running performance of the CCHP system.And the operation and control area of the CCHP system were more extensive.A the same time,a comprehensive optimization method for the optimization design of the CCHP system,considering the supply and demand matching coefficient,the annual total primary energy cornsumption(PEC),the annual total cost(ATC)and the total environmental pollution effect(EPE)had been proposed.And the NSGA-II optimization method was adopted to solve the model.The optimization method provided theoretical support for the optimal design of the CCHP system.Finally,a practical office building has been taken as a case study,a hybrid combined system has been designed to support the building’s demands based on the supply and demand matching design method for CCHP.The hybrid combined system contained different control measures:such as MCR control and ORC control for different users’ load conditions.The multi-index integrated optimization analysis was carried out on hybrid combined system,the typical CCHP system under follow electricity load(FEL)mode and under follow thermal load(FEL)mode respectively,based on the user’s annual hour load data.The results showed that compared with the separate system,the supply and demand matching coefficient relative reduction rate,total primary energy saving rate,total cost saving rate and total environmental pollution effect relative reduction rate of the typical CCHP system in FEL optimization mode were 41.85%,9.06%,4.58%and 33.94%respectively.The supply and demand matching coefficient relative reduction rate,total primary energy saving rate,total cost saving rate and total environmental pollution effect relative reduction rate of the typical CCHP system in the FTL optimization mode were 17.03%,8.45%,4.8%and 20.20%respectively.The supply and demand matching coefficient relative reduction rate,total primary energy saving rate,total cost saving rate and total environmental pollution effect relative reduction rate of the hybrid combined system were 19.70%,19.52%,8.24%and 40.46%respectively.Compared with the typical CCHP system,the hybrid combined system has improved obviously in the three aspects of the annual total primary energy consumed,the annual total cost and the total environmental pollution effect.Finally,the effects of natural gas price,MCR cooling coefficient,MGT starting operating point and ORC rated power on the annual running performance of the hybrid combined system were analyzed.