Ciborowski and Pluemer (1991) present a case study of energy-efficient cooling in a semiconductor cleanroom in Sunnyvale, California.
...the power requirements (kW/Ton) for chillers drops the cooler the condenser water that is used. Temperature approach for condenser water to outside wet bulb is on the order of 5-7°F at 75_-80°F wet bulb temperatures. At an outside wet bulb temperature of 50°F, a typical cooling tower temperature approach is on the order of 15°F. Even with this approach divergence, it is possible to get 65°F condenser water with a 50°F outside wet bulb. ...the cooling tower fans are equipped with variable frequency drives. As part of the general building information, ... the dew point and dry bulb temperature of the outside air [are measured]. From this information the wet bulb temperature is calculated. The tower sump water temperature is also monitored. Based on approach information provided by the cooling tower manufacturer, an algorithm was written to reset the condenser water temperature based on outside wet bulb, by varying the speed of the cooling tower fans.