In this paper, a district heating and cooling (DHC) plant operation support system and an on-line heat load prediction system are described. For DHC plants using electricity, it is desirable to use thermal storage to shift the electric power load from the daytime to nighttime. To do that, it is necessary to make a schedule of DHC plant operation based on hourly heat load predictions for the next day. The operation support system has two subsystems. The heat load prediction subsystem gives the hourly heat load predictions that are necessary for heat pump operation. This subsystem is used on-line. In the similar days selection subsystem, similar days are selected from past plant operation. This operation support system is used in a real DHC plant operation.

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