Research On Optimization Design Method And Operation Performances Of Integrated Energy System

Through the organic coordination of the whole process of energy production,transmission,conversion,storage and consumption,the integrated energy system(IES)optimizes and integrates various forms of energy,such as thermal energy,electric energy and natural gas,so as to realize the coupling,coordination and complementation,and the cascade efficient utilization of different types of energy.IES can meet various energy needs of users,and has efficient,environmental,economical,reliable and flexible characteristics,which is an effective approach to achieve the clean,low-carbon,safe and efficient energy provision.However,there are still many scientific problems that need to be further studied in the field of IES design and operation.In this context,this paper studied the optimization design method and operation performances for building-scale IES and district-scale IES,from the perspective of three system levels(i.e.device,unit and network),which is aiming to provide theoretical basis and key technical support for the configuration optimization and coordinated operation of IES.In this paper,the variable-condition thermodynamic models of IES functional units,and the optimization model of the building-scale IES with the minimal annual total cost as the target were initially established.Also,a cost-oriented self-adaption(SA)strategy was proposed.Based on the exhaustive search method,the optimized configuration and operation of IES were explored,accoriding to following electric load(FEL)strategy,following thermal load(FTL)strategy and SA strategy respectively.Further,the quantitative relationships between different optimization variable combinations,energy supply area,floor area ratio,energy supply distance and the annual total cost of IES were obtained.The results indicate that the building-scale IES can effectively reduce the annual total cost under the SA strategy.Subsequently,aiming at the disadvantages of the conventional central circulating pump(CCCP)district heating system,such as high energy consumption and low economic benefit,the distributed variable-frequency speed pump(DVFSP)district heating system was proposed.Also,an equipotential line method was illustrated to determine the optimal energy station locaton for district heating system.Further,for the building-scale IES couplied with DVFSP system,the operation performances,economic benefit,payback period and other related aspects were studied.The results show that the payback period of the IES operating with FEL strategy is obviously shorter than that with FTL strategy,and the payback period is more significantly affected by the heat price.Afterwards,an IES,including two power cycles(i.e.an internal combustion engine(ICE),an organic Rankine cycle(ORC))and solar thermal unit(ST)and a compressed air energy storage(CAES),was proposed.The energy provision characteristics and operation performances with different system integrated configrations were obtained.Through optimizing the operation parameters with the minimal operation cost as the target,the economic operation mode of IES with typical configuration was determined.It is found that the IES couplied with multiple energy conversion units and energy storage units can flexibly adjust the output electric-heat ratio,reduce the amount of generated waste heat.The economic operation mode can significantly reduce the cost per unit area,and improve the system energy efficiency.Finally,for the problem of time-consuming solution of the regional nonlinear collaborative optimization model,a three-layer nested loop optimization method which combines the orthogonal experiment method and genetic algorithm was proposed.Based on this method,the annual total cost,the energy interaction between energy stations,and the cost with different energy supply areas for the district-scale IES were investigated,which was also compared with the reuslts of buildin-scale IES.It indicates the rule of economic difference between the district-scale IES and the building-scale IES.Through the case study,this method is applicable to solve the optimization problem under the network level for the equipment configuration,operation state and energy interaction mode between multiple energy stations.