| In recent years,natural gas distributed energy systems(DES)were extensively applied in the word,and many advantages of DES(such as high energy efficiency,CCHP,etc.)also have been recognized by the industry experts.However,the natural gas DES were simply adopted without in-depth analysis in practical engineering applications,and the energy consumption of natural gas,cold energy and heat energy transmission and distribution was not comprehensively considered.In this study,aiming at the trend of widely application of gas distributed energy,the energy consumption transmission and distribution of natural gas,cold energy and hot energy were unified included into the comprehensive energy consumption of the combined supply system.The calculation method of comprehensive energy efficiency of natural gas DES was analyzed,and the comprehensive energy efficiency calculation software of gas DES was developed,which would provide a high-efficiency calculation tool for the comprehensive energy efficiency evaluation of the combined supply system under different conditions in practical engineering applications.First,the calculation method of energy consumption of natural gas long distance pipeline transportation was analyzed.Based on the comprehensive analysis of energy consumption,the analysis of theoretical calculation method in natural gas pipeline energy consumption was carried out,and the influence of different transmission distances and volumes on the pipeline efficiency was studied by using the parameters of Seninglan pipeline.The results showed that the pipeline efficiency had a linear relationship with the transmission distance under the condition of the remaining parameters unchanged.When the transmission distance increased from 200 km to 1400km,the energy consumption of natural gas elevated from 0.5%to 3.6%of the energy carried by natural gas;with the increase of throughput,the pipeline efficiency also gradually decreased.When the throughput raised from 14×10~8 Nm~3 to 34×10~8 Nm~3,the energy consumption elevated from 1%to 7%of the energy carried by natural gas.Secondly,the calculation method of integrated energy efficiency of natural gas DES was established.The energy transportation consumption of natural gas,cold energy and hot energy were included in the primary energy utilization efficiency calculation of the combined supply system,and the influence of different factors on the comprehensive energy efficiency of the combined supply system was analyzed.The results showed that with the increase of the flue gas temperature at the outlet of the absorption refrigerator,the refrigerating capacity would decrease.When the flue gas temperature at the outlet of the absorption refrigerator increases 10°C,the primary energy utilization rate would decrease approximately 0.34%.When other parameters remained unchanged,with the increase of energy supply distance,the primary energy consumption ratio(ECR’)of energy consumption and transmission of cold and hot water circulating pumps increased,which would decrease the primary energy utilization rate.With the increase of specific friction,ECR’also gradually increased,but the primary energy utilization would decrease.When the temperature difference between supply and return water raised,the ECR’decreased,which would increase the primary energy utilization.Finally,the comprehensive energy efficiency calculation software of gas distributed energy was developed by MATLAB,and the influence of gas transmission energy consumption and various factors during the process of cold and hot transmission on the comprehensive energy efficiency of the combined supply system were analyzed.In case of an actual natural gas DES,the software calculation results showed that the primary energy utilization efficiency could reach 78%under cooling condition(the ratio of cooling to power at 1,operation condition of determining electricity by heat).Considering the energy consumption generated in the transmission and distribution of cold water,according to the maximum average specific friction,when the energy supply radius was 500 m,800 m and 1000 m,the corrected efficiencies could reach 75.2%,74.9%and 73.9%,respectively.Based on the maximum energy supply radius of 1000 m,when the average specific friction was 40Pa/m,60 Pa/m and 80 Pa/m,the primary energy utilization efficiency could reach75.0%,74.5%and 74.0%,respectively,which all meet the requirements of specification. |
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