Operation Optimization Of Natural Gas CCHP System Under Dynamic Loads

The combined cooling, heating and power (CCHP) system is broadly identified as an alternative for the world to solve energy, economic and environmental problems. Using natural gas as primary energy for CCHP system is the best choice to achieve building energy-saving and to efficiently utilize natural gas. Natural gas CCHP system is built on the concept of multistage energy utilization which can provide cooling, heating and electricity for the buildings in order to improve energy efficiency and reduce carbon emission. Therefore, to optimize the facilities scheme and operation of the CCHP system will bring huge economic and environmental benefits to human society.Firstly, this paper introduces the basic concept and characteristics of natural gas CCHP system. On the basis of relevant literature, the system scheme is carried out. The main equipments characteristics of CCHP system are summarized and introduced. This study also introduced a novel operational strategy in which the system follows a hybrid electric-thermal load. Based on the analysis of the energy flow, a mixed integer nonlinear program (MINLP) optimal model has been developed with objective of minimizing the annual total cost.Secondly, a commercial building is simulated and calculated by the software of EnegryPlus, the data of building cooling, heating and electric loads are obtained hourly in a year. The facilities scheme and operational strategy of this model are optimized by particle swarm optimization (PSO) algorithm. After that, the operation strategies are analyzed and energy-saving, economical and environmental effect of the CCHP system are evaluated. The result has an actual guiding significance for the CCHP system design and operation, which will be a reference for the development of distributed energy systems.Finally, an optimization model of CCHP system including the environmental cost is proposed. In the model, the pollutant emission and reduction factors are considered, and the constraint of pollutant emission is introduced. Furthermore, a sensitivity analysis is presented in order to show how the annual total cost would vary due to the changes of natural gas price, electricity price and environmental cost. The proposed model can be an effective tool for accurate evaluation and optimal operation of CCHP systems.