ASSIGNMENT MODEL FOR CHARGING OF THERMAL ENERGY STORAGE BY ELECTRIC CHILLERS USING ZERO-ONE PROGRAMMING APPROACH

Thermal Energy Storage (TES) system is commonly installed at District Cooling plant for storing of chilled water (CHW). The stored CHW is used to support requirement of chilled water during day time. Charging of the TES tank by the electrical chillers (EC) is done during off-peak hours. For the case of TES tank at Universiti Teknologi Petronas (UTP), the charging of TES tank is done from 6pm to 6 am. To ensure optimum TES charging, the operations of EC need to adhere to an optimum scheduling strategy. To address this requirement, an assignment model using transportation model is proposed. The model is formulated as a zero-one programming model. Spreadsheet is used for solving the model. Results from analysis indicate that maximum production of chilled water depends on the generating capacity of the EC. Results from three case studies indicate that all EC were operated at below rated capacity. Based on the weekly data, the maximum operated capacities of EC1, EC2, EC3 and EC4 are 308RT, 288RT, 295RT and 270RT respectively. This is below rated capacity 325RT of the EC. The outcome is that TES is not charged to full capacity during off peak period. From the sensitivity analysis using the proposed model, TES could be fully charged during the off peak period. An example, if three of EC are operated to full capacities for specified off peak period, TES could be fully charged. The model could be useful for the UTP District Cooling plant to schedule EC for charging of TES during off peak hours.