Original Date: 03/17/1997
Revision Date: 01/18/2007
Information : Chiller Performance
Polaroid’s production requirements made it necessary to operate the cool water chillers during the winter months. Each chiller, matched with a water cooled condenser that had a fixed fan and pitch, was controlled by a snap-acting thermostat ranging from 75°F to 85°F. The cold winter air would quickly cool the water in the condenser to 75°F and cause the chiller to turn off until the water’s temperature rose to 85°F. With this situation occurring 20 times an hour, the inconsistent water temperature of the condenser caused the chiller to constantly load and unload, resulting in higher energy cost.
Polaroid implemented a short-term solution by installing a variable pitch fan blade on the water tower. The apparatus would sense the water temperature of the condenser and then adjust its blades according to the load of the system. This solution maintained a constant water temperature in the condenser, allowed the chiller to operate smoothly without constant loading and unloading, and reduced the energy consumption from 0.8 to 0.7 kilowatt per ton.
Next, Polaroid installed variable speed devices on the chiller and condenser pumps, and used a control system to modulate the devices according to the cooling load of the building. By adjusting speeds according to the demand, this new system reduced Polaroid’s energy cost further from the initial starting point of 0.8 to 0.43 kilowatt per ton.
By retrofitting its cool water chillers with variable pitch fan blades and control systems, Polaroid saved $30,000 a year in energy cost on a one-time investment of $10,000. In addition, Polaroid saved almost 50% in energy by installing variable speed devices on its motors and pumps.
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