Optimization Of Heat Pump Supplementary Heating System For Heating Substation

With the development of urban construction,the heating capacity of the district heating substation cannot meet the increasing heat load demand due to the increasing buildings,and there is an urgent need to supplement the heating capacity of the existing heating substation.Also,targets such as “coal consumption reduction”,“carbon peaking”,and “carbon neutrality” put forward higher requirements for the selection of district heating sources.Therefore,heat pumps get more attention in the field of district heating for its environmental protection,high efficiency,energy saving and stable characteristics.In order to solve the insufficient heating capacity of district heating substations caused by urban expansion,to respond to clean heating policy,and to avoid the costs of a municipal heating network transformation,this paper establishes three heat pump supplementary heating systems for district heating substation,namely,electric-driven air-source supplementary heat pump heating system,electric-driven water-source heat pump supplementary heating system,and hot water absorption heat pump supplementary heating system to increase the heating capacity of the heating substation.According to the application principles of three different types of heat pumps and the available resource of urban district heating substation,the physical models of each system are determined.On the basis of theoretical analysis,the simulation models of the three systems are established in TRNSYS.Bi-level optimization model with the target of optimal life cycle economy is adopted for the most reasonable facilities capacity and operation strategy.A residential district heating substation supplementary heating system in Beijing is taken as an example and the system optimization results and application effects are compared and evaluated from the perspectives of the systems energy consumption,equipment scheduling,application economy and economic sensitivity,and the application impact,respectively.The simulation research results show that,from the design optimization results,the three systems have respectively achieved a reduction in installed capacity of 394 k W,344 k W and 544 k W with the reasonable configuration of the heat storage device.And from the results of operation optimization,the heat pump unit is the main heat supply equipment in the air-source heat pump supplementary heating system,and its opening time accounts for 67%,and the total heat supply accounts for 70%.As for the watersource heat pump supplementary heating system and absorption heat pump supplementary heating system,the plate heat exchanger plays the main role in heat supply strategies,and its heat supply accounts for 90.3% and 91.3% respectively,while the heat pump units and the heat storage device are responsible for heat supplement and peak regulation.Compared with the other two systems,the air source heat pump supplementary heating system can reduce the total energy consumption by more than50%.All three systems can meet the supplementary heating requirements,but for the energy-saving potential of the three system,air-source heat pump supplementary heating system is better.All three systems can make accurate scheduling for changes of heat load as well as realizing economic benefits during the full life cycle,but the airsource heat pump supplementary heating system is more economical because it has an operating cost of over ￥800,000 less than the other two systems for every year.In addition,the sensitivity analysis results indicate that the metered heating price and life cycle have a greater impact on the economics of system application,so it must be considered attentively.It is found that the daily load rate of the power grid can increase by 5.2% during non-severe cold periods,and the seasonal imbalance coefficient for the whole year can increase by 25.2% when the air-source heat pump heating system is applied.Its application can make the regional electric load in winter more stable,improve the overall reliability of the power grid and the utilization rate of power assets.