آنالیز عملکرد سیستم خنک کننده ناحیه ای مبتنی بر اطلاعات عملیات Performance analysis of a district cooling system based on operation data

1. Introduction District cooling system (DCS) becomes increasingly popular for its high energy efficiency. It appears to be a promising energy saving measure for high density business areas especially in Hot Summer Cold Winter zone and Subtropical zone. The results show that the energy efficiency for cooling in DHC systems is superior to that in the case of individual cooling systems because of the ‘‘concentration effect’’ and ‘‘grade of operation’’ [1]. A further study shows that energy conservation measures on the demand side would decrease energy consumption by 23.9% when electric driven heat pumps are used as the heat source[2]. However, the two large and well-known projects in China, were claimed the price for cooling taken from DCS too expensive. It is almost the same with or even higher than the local electricity price compared to only half or one third of the electricity of a traditional cooling system [3]. For many reasons such as that DCS is not well designed or operated and the energy efficiency is lower than that expected [4]. For most DCS projects, there are few English literatures about the analysis of their energy efficiency based on actual operating data. Thus, the so-called high efficiency can’t be verified and it’s hard for the designers to realize their mistakes in design phase, such as over sizing the capacity of the equipment. Based on those facts, operating data are collected to evaluate the actual performance of the DCS plant. 2. Methods In this paper, we take a DCS plant in Hot Summer Cold Winter zone as an example. The data were uploaded by sensors embedded in the system. The DCS plant was developed in an area of 166,667m2 that will actually comprise a floor area of 1,000,000 m2 . The predicted total cooling demand of this area was 116MW. Considering simultaneity usage coefficient of 0.7, the design values are 77.9MW for the cooling load and 49.0 MW for the heating load. The cooling load is produced by five centrifugal chillers, two direct-fired absorption chillers, five steam-operated absorption chillers and one flue gas/hot water with direct-fired type absorption chiller. Table .1 shows the main units in the plant.