Research >> 1. Energy Saving from HVAC System >>Optimization for the operation of district heating and cooling system

■ Optimization for the Operation of District Heating and Cooling System

□ The Retro-Commissioning and Proposal of Operation Shemes for the Heat Sourse System of an Existing District Heating and Cooling System by Simulation

Purpose of the study
District Heating and Cooling (DHC) systems have been applied since the 1970's because the DHC can reduce harmful waste exhaust and offers improved energy efficiency compared to traditional local heat and cooling systems. However, the Coefficient of Performance (COP) of the system has often been reported to be less than 1 because delivering energy consumption is large and equipments are oversize, for example, which make the achievement of high energy efficiency impossible. Therefore, it is important to operate DHC systems either reasonably or optimally, which requires the development of an enhanced operation mode in order to improve energy efficiency and maintain normal heating and cooling operation. In order to apply retro-commissioning to an existing DHC system, simulation models of each component were first developed, and the simulation accuracy was verified using measured data. Next, the models of the individual components and the control model were connected to form the simulation model of the entire heat source system. Finally, several proposals for the reduction of energy consumption were analyzed through simulation.

Figure-1 Buildings served by the DHC plant

Figure-2 System diagram of the heat source plant

Figure-3 Measurement

Results of the study
For the purpose of improving the operation of the DHC plant, the DHC system was analyzed to develop an optimal operation method. The following items were examined:
 1) The change in the temperature set point of the cooling water.
 2) Assess the performance of an operation mode that does not use an ice thermal storage subsystem because of its low COP.
 3) Assess the performance of making the chilled water return temperature in conform with the design value by changing the water flow rate.
 Furthermore, a tool for optimizing the operation of heat source plant is developed using MATLAB language and Sateflow and Simulink tool.

Figure-4 Tool to optimize the operation of heat sourse equipment by Stateflow

Figure-5 User interface of the simulation tool by MATLAB/Simulink