The energy-efficiency impacts of cooling towers are analyzed in Kruse (1991):
Cooling towers play a relatively minor role in the direct energy consumption of a project, but their relationship with chillers allows them to have a significant indirect effect. As previously mentioned, the efficiency of a chiller improves with colder condenser (cooling tower) water. For this reason, don't be afraid to buy plenty of cooling tower. Towers are relatively inexpensive pieces of equipment, and they can lose efficiency if not sufficiently maintained. Also, don't be in a hurry to cycle down or cycle off the tower fans. Compare the fan energy savings with the chiller performance first. It is likely that running the fans to create colder tower water will reap overall savings due to improved chiller efficiency.
Cooling tower capacity can be better maintained with water filtration devices. According to Latzer (2002), reduced energy consumption, improved chemical performance, lower maintenance costs, and safer operation are possible when tower water is kept clean. A permanent media, or "sand", filtration system is designed to automatically backwash itself when the media becomes clogged.