Open-source Modelica models for the control performance simulation of chiller plants with water-side economizer

There are several cooling mode control sequences for chiller plants with water-side economizers adopted in industry and academia, and it is widely known that this supervisory control significantly affects energy consumption; however, there is a lack of a modeling resource to allow multiple control sequences to be evaluated systematically under different settings, such as system configurations, load types, and climate locations. To fill this gap, this paper develops open-source Modelica models to simulate the control and energy performance of multiple cooling mode control sequences for chiller plants with water-side economizers. These models allow users to develop and test their advanced control sequences for chiller plants with water-side economizers for their target climates and system configurations. To demonstrate how these models can be utilized, a chiller plant with an integrated water-side economizer is simulated using two advanced cooling mode control sequences, two cooling load types, and six climates, for a total of 24 simulation cases. This study revealed that the energy saving potential varied from 8.6% to 36.8% for constant load profiles in all of the considered climates, and from 6.3% to 25.8% for variable load profiles in most of the climates. Results also showed that the developed system models are able to capture transient control details and reveal counterintuitive energy performance.