Multi-State Availability and Reliability Assessment of Electric Chillers of a District Cooling Plant

Availability and reliability are among the factors that influence the equipment and plant performance. These factors are more important for equipment and plants that are required to operate continuously to meet the demand. For the case of a co-generated district cooling (GDC) plant, among the equipment that are continuously operating are gas turbines (GT), electric chillers (EC) and absorption chillers (SAC). In this paper, availability and reliability assessment of EC are selected for the study. The EC are used for charging of the thermal energy storage of the GDC plant. Due to multi-states nature of the demand, Markov model was used for the analysis. Five years performance data were used to determine the states of the models covering the full working, partial working and failed states. State space diagram is used to indicate the possible operating scenario of the EC. The differential equations were formulated to evaluate the availability and reliability of the chilled water generated by the EC. Results from the analysis indicate that the model is able to predict the EC availability with 95 per cent confident level in comparison with the actual data. While for the case of reliability, the values obtained by the model are comparable with the traditional binary availability. In conclusion the developed models could be useful to predict the availability and reliability of EC at the GDC plant.