Optimize a Chilled-Water Plant with Magnetic-Bearing Variable Speed Chillers

摘要

Variable speed centrifugal chillers perform much more efficiently at part-load ratio of cooling demand as well as partial compression ratio of lift head compared to constant speed centrifugal chillers. Magnetic bearing technology further improves the benefit of variable speed centrifugal chillers. This performance difference requires a reconsideration of most effective plant operation when magnetic bearing centrifugal chillers are incorporated. In this paper, a component-based model is developed for a chilled-water plant with oil-free chillers at the Texas A&M University System RELLIS Campus. The model, calibrated by on-site measured data from the building automation system, is used to evaluate the savings potential for different operation strategies. An optimal chiller staging strategy, basedon the optimal efficiency curve, is simulated for the case study plant under constant water flow and variable water flow scenarios respectively. The results show that optimal chiller staging only improves plant performance by 2.1% for the constant water flow system. Implementing optimal staging with variable water flow would increase the energy savings to 13.7% compared to current operation of the case-study plant.