| Regional ground source heat pump applications are widely known for their advantages of energy saving,good environmental benefits,high system efficiency,and economical efficiency.However,there are usually problems in the selection and optimization of system types.One of the common key issues is the choice of system form centralized and decentralized.The choice of system form,in the centralized form,also involves a centralized reasonable scale.This article will take the actual project of three ground source heat pump systems as an example to analyze and compare its energy efficiency.The comparison involved two situations: the design of the full load condition and the dynamic load condition throughout the year.And it analyzed existing measured energy efficiency.Three actual projects were analyzed: they were a small and medium-scale centralized system in Wuhan,a certain regional decentralized system in Wuhan,and a large-scale centralized system in Guiyang.The design of the full-load operating conditions was based on the design parameters of the three systems and compared the host,pump,and system energy efficiency.Under the design of full-load conditions,due to the high proportion of energy consumption and low energy efficiency of the transportation system of large-scale regional centralized systems,the centralized system of small and medium-sized areas is 21.01% more efficient than large-scale regional centralized systems.In the design of the system,it is necessary to reasonably match the energy consumption ratio of the host and the transportation system to prevent the scale being too large and the chilled water circulation system needs to set up a multi-stage pump transmission cycle,which causes the energy consumption of the transportation system to be too high,thereby lowering the energy efficiency of the system.Regional decentralized systems,due to the differences in the main engine compressors and the differences in the efficiency of the water pump motors,caused the energy efficiency of the system to be 28.1% lower than that of the medium-and small-scale regional centralized systems.In order to eliminate the inconsistency of case equipment selection performance,based on samples from multiple manufacturers,the energy efficiency of the host and the pump under the average equipment performance level was statistically analyzed.In the three cases,the design was re-evaluated with the average equipment performance level.Energy efficiency: The energy efficiency of small and medium-sized centralized systems is on average 20.8% higher than that of regional decentralized systems.The average energy efficiency of large-scale regional centralized systems is 11.6%.It is recommended that if the regional scale is too large,centralized systems in the design of the whole region should be divided into several reasonably-sized regional centralized systems.Under the dynamic load conditions throughout the year,using the system energy consumption simulated by TRNSYS,a centralized system model and a regional decentralized system model were established based on the example system.Under typical meteorological hourly data,the system energy efficiency was simulated and calculated.The centralized system of small and medium-sized areas is mainly due to the low energy efficiency of the host running at low load rates,resulting in a decrease of 18.4% in energy efficiency of the system compared to the energy efficiency of the design conditions system,while the regional decentralized system can operate under partial load conditions.With some of the mainframes turned on,the mainframes were operating at a relatively high load rate.The energy efficiency of the system was only 8.4% lower than that of the design operating conditions system.The medium and small-scale regional centralized systems were 13.1% more efficient than the regional decentralized systems.Finally,the energy efficiency of the centralized system is higher than that of the decentralized system.The use of regional centralized systems is better when dynamic load fluctuations are small,and most of the buildings are in high demand buildings for the whole year.However,for buildings with large changes in air-conditioning load demand and large differences in the use of end-use equipment,the regional distributed system is more adaptable and has a lower energy efficiency reduction ratio than the design operating conditions. |
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