This report presents an example of introducing inverters to a large-capacity centrifugal chiller and the resulting effects. A fixed-speed centrifugal chiller attains the highest COP at the rated capacity when the cooling water inlet temperature is at the rated value. However, the annual load variations show that operation under the rated conditions is rare and operation is mostly under partial load conditions or low cooling water temperature conditions. On the other hand, a variable-speed centrifugal chiller significantly improves the COP under partial load conditions or low cooling water temperature conditions. As a result of the improvement of system operation and the introduction of inverters to centrifugal chillers that were delivered as fixed-speed centrifugal chillers in the past, the cooling COP of the system in fiscal 2018 improved by 15% compared with that in fiscal 2012.
