Optimization of a chilled water plant without storage using a forward plant model

This paper introduces a forward chilled water plant model to optimize the setpoints of continuous controlled variables in a chiller plant without storage and controlled by supervisory control. It can also be used to estimate the savings potential of some energy conservation measures. This model is based on a Wire-to-Water efficiency concept to simulate the plant power for producing cooling. The fluctuation of the chilled water loop supply and return temperature difference is also considered to reflect its effects on the chiller loading and pumping power. The variables to be optimized could be cooling tower approach, chiller chilled water leaving temperature, and chiller condenser water flow rate. This is a non-linear programming problem and can be solved with the generalized reduced gradient nonlinear solver. The application of this model is illustrated with a practical chilled water system.