Nested Optimal Design For Renewable Energy Sources Integrated Combined Cooling,Heating,and Power System

Since the 21st century,with the development of the global economy,the world's population and energy consumption have increased dramatically.Fossil energy reserves continue to decrease and a large number of greenhouse gases have exacerbated the deterioration of the ecological environment.Human society is gradually experiencing energy and environmental crises.Vigorously developing renewable energy and achieving efficient use of energy are two important means of reducing the proportion of fossil energy consumption and building a clean,low-carbon,safe and efficient modern energy system.The combined cooling,heating,and power(CCHP)system is based on the principle of energy cascade utilization and local consumption.CCHP systems have such excellent characteristics as flexible distribution,efficient energy saving and low-carbon environmental protection.It is an ideal way to achieve energy saving and emission reduction.The CCHP system is a multi-input multi-output and energy-flow-coupled energy supply system.Its equipment selection,capacity configuration,and system operation mode determine the energy supply efficiency of the system.Existing studies usually use a single operating mode to optimize the system capacity on the basis of a fixed structure,and the proposed structure often lacks scientific theoretical support.In addition,the renewable energy sources integrated CCHP system has a larger structure and a more complicated energy flow.The key equipment of the system works more under off-design conditions,and the equipment capacity configuration is more dependent on the operation mode of the system.Therefore,it is difficult to obtain the optimal configuration result using a single fixed operation strategy.Therefore,this paper deeply studies the key problems of system structure,off-design characteristics,capacity and operation mode optimization.The nested optimization method of system structure,equipment capacity and operation mode is constructed,which provides ideas for the efficient application of renewable energy CCHP systemFirst,this paper proposes a structure design method for the multi-input multi-output and multi-coupling CCHP system.This method builds an energy supply path model based on energy input,conversion,and output.Using the equivalent electrical coefficient as the evaluation objective,the structure of the CCHP system is optimized.At the same time,the energy supply efficiency of the main energy supply unit of the system under different load rates is analyzed.And analyzes the system cooling,heating and electricity supply balanced type,which lays the foundation for the subsequent system capacity configuration researchSecondly,according to the optimized system structure,considering the influence of the randomness of renewable energy on the output of the energy supply unit of the system,a two-stage nested optimization configuration method for renewable energy CCHP system is proposed.The first stage uses genetic algorithms to obtain the capacity of each system equipment,and the second stage uses a nonlinear programming method to obtain the equipment output plan.The linear weighting method is used to comprehensively consider the three optimization goals of energy,economy and environment to establish a solution model.This method reduces the complexity of the optimization model,optimization variables and constraints,making it easier to obtain the optimal solution to the problem.Finally,this paper validates the proposed nested design method based on the cooling,heating and electricity loads of the selected building.The results show that compared with the traditional design method,the nested optimization design method has significantly improved the primary energy saving rate,comprehensive cost saving rate and carbon dioxide emission reduction rate index.Through the analysis of the results of the system throughout the year and typical days,it is proved that this method has a reasonable configuration effect.Compared with the traditional method,this method can more fully utilize renewable energy to match the user load.