Environmental Leading Assessment Modeling And Multi-objective Optimization Of Comprehensive Energy System Based On Renewable Energy

With the development of the global economy,the energy consumption is increasing,while fossil energy reserves are decreasing,and greenhouse gas emissions dominated by carbon dioxide are rising sharply.The energy and environmental issues have attracted more and more attention.Distributed energy supply system combines energy resources with buildings,which is a comprehensive energy system integrating stable,efficient,environmental protection and safe energy supply.Through the integration of comprehensive energy supply system and diversified renewable energy,the energy structure imbalance,energy shortage and environmental pollution are solved.Solar energy,biomass energy and air energy are widely concerned and applied because of large reserves and environmental friendliness.The comprehensive energy system based on renewable energy(RE-CES)is formed by many devices,which is complex,interactive and interdependent.And the problems of low efficiency,waste resources and mismatch between the sides of supply and demand are easily caused due to improper configuration.By establishing the mathematical model of comprehensive energy system with complementary solar energy,biomass energy and air energy,accords with the "double carbon" policy of China,the comprehensive evaluation model based on environment and multi-objective optimization model are structured in the present work.The 50 households at the level of the village in the cold area(Lanzhou city)are taken as an example to analyze and verify.The main research operation of this manuscript is as follows:Firstly,according to the construction principle of evaluation indexes of comprehensive energy system,various evaluation indexes are analyzed and screened.The thermal,environmental and economic indicators of the system are studied,for fitting the current urgent needs of environmental policies and the requirements of multi-dimensional evaluation,an environmental comprehensive evaluation index CEI is built,and a multi-dimensional comprehensive evaluation index based on weight on account of environment for comprehensive energy system is established.Secondly,considering the regional environmental factors,climate conditions,energy consumption characteristics of users and the distribution of local renewable energy,a comprehensive energy system on the basis solar energy,biomass energy and air energy is constructed.Combined with advanced technologies of solar photovoltaic panel power generation,anaerobic fermentation of biomass,internal combustion engines and air source heat pumps,then the RE-CES is founded through material flow,energy flow and data flow.Nextly,the multi-objective optimization model of the RE-CES under various operation modes is set up.The maximized benefit relative evaluation indicators are selected as the objective function,and the demand side constraints,energy conservation and facility operation constraints as the constraints conditions.The capacity of internal combustion engine,anaerobic reactor,solar photovoltaic and air source heat pump are as the decision variables.Combined with the improved multi-objective genetic algorithm(NSGA-Ⅱ),using the combination of subjective and objective solution technology Entropy-Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)method to realize the multi-objective optimization of the RE-CES.Finally,a variety of optimal setting schemes of RE-CES under diversified operation modes are solved and analyzed.The results reveal that the election of population number and reproduction iteration times has a part of effects on the optimization results.Under the allowable calculation conditions,multiple different schemes can be selected to find the optimal setting with the best convergence effect and optimization results at the balance of calculation speed and time.When maximizing carbon dioxide emission reduction rate,annual cost saving rate and primary energy saving rate,the weight factor of environmental comprehensive evaluation index is 1/2 and the economic and energy index is 1/4,the comprehensive evaluation index CI dominated by environment after optimization under the three operation modes is better than that before optimization.At the operation mode of mixed loads following,the change of optimization results is the most obvious,and the optimized value is also the highest in all schemes,and the CI increases from 48.66% before optimization to 52.30%.The comprehensive environmental assessment index CEI also reached the maximum of82.53% under the mode of mixed loads following,and the proportion of all input renewable energy increased from 93.48% before optimization to 99.14% after,which verified the reliability of the multi-objective optimization model.