Performance Analysis And Optimization Of Nature Gas-fired CCHP System

Distributed combined cooling heating and power system(CCHP) is a kind of system based on the concept of cascaded utilization of energy. Because of the high efficiency, energy saving, high reliability, environmental protection and peak load shifting, this system is considered to be one of the best choice to solve energy, economic and environmental problems. At present, CCHP system is widely used in the United States, Britain, Japan and other countries. Recently the development of CCHP system attaches more and more attention in our country. The CCHP system has many equipments and influence factors, so it's necessary to configurate and optimize the system rationally to exert its advantages.Previous studies are mostly about system configuration or operation strategy of CCHP system in grid parallel mode. Yet to see exhaustive studies on CCHP system operating in grid connected mode.Firstly this paper introduces the basic concept of CCHP system, including the system classification, form and performance evaluation, etc.This paper compares the commonly used methods of load forecasting and simulates the hourly cooling, heating and power loads of an office building of 10000m2 in North China.The energy demands including cool, heat and power of the office building are presented and analyzed.A CCHP system for the office building is proposed and designed. Then the running performance, energetic and economic of CCHP system following the thermal load and the electrical load are respectively analyzed and compared. For the office buildings in this paper, CCHP system following the electrical load has better economic and energy saving efficiency.A mixed-integer nonlinear programming(MINLP) model with minimization the annual total cost as objective is established to optimize the facilities scheme and operational strategy of cogeneration system. Research shows that the Primary energy ratio(PER) of CCHP system is significantly higher than the conventional energy supply. The PER is 69% and the primary energy saving rate is more than 20%. The annual cost of the optimized CCHP system is 970 million Yuan about 80% of the traditional mode. The influences on the economy of CCHP system are studied such as natural gas price and electricity price. When natural gas price is less than 3.4 Yuan/m3, or electricity price is greater than 0.6 Yuan/k Wh, the economy of CCHP is superior to the conventional energy supply. And when natural gas price is higher than 3.6 Yuan/m3, or electricity price is less than 0.5 Yuan/k Wh, the CCHP system is not suitable for the building.Finally, the feasibility of electricity sale of CCHP system is studied. The optimal equipment configuration and operation strategy of the electricity sale CCHP system is got based on the above optimization mode.Then this paper calculates the payback period of investment, annual fees and annual heat release under different electricity price to investigate the feasibility of the online system.The result shows that the annual fees decreases with large electricity price ratio. At the same time, the payback period and annual heat exhausted may increase drastically.