This White Paper describes factors to be considered when optimizing an existing data center chilled water plant.
Data centers have always emphasized system reliability as a primary goal. However, recent emphasis on the energy consumption of data centers has renewed a focus on cooling efficiency. As system efficiency and ultra-low Power Utilization Effectiveness (PUE) numbers assume a higher profile, particularly in new purpose-built data centers, the PUE of legacy data centers can sometimes be dismissed or overlooked. But even among data centers a decade old or more, substantial improvements in operating efficiency can be made, often with little or no new equipment.
The primary energy users in chilled water systems are roughly, in decreasing order: the chiller; the cooling tower fan; the chilled water pumps (whether primary only, primary/secondary or variable primary); and the condenser water pumps. The fan energy of the air distribution systems is another component which needs to be considered when trying to optimize total net cooling system efficiency instead of just concentrating on wire-to-water plant efficiency, or least effective of all, just chiller operating efficiency. All the components combine and work in concert.